Unit 4 Learning Guide
Chapter 11- Nervous System
Lesson 1- Neurons
Complete the following table by describing the three main types of nerve cells.
motor neurons
sensory neurons
interneurons
Carry impulses from the central nervous system to effectors
such as organs, muscles, and glands. Long axons and short
dendrites
Carry impulse from the sensory receptors (any cells that
detect eternal or internal stimulations.) to the central nervous
system. Has the cell body outside of the CNS. Short axons and
long dendrites
Carry impulses from the sensory neurons to motor neurons
and are located solely in the central nervous system.
Summarize the location, structure and function of the myelin sheath. Then name the
disease that affects the myelin sheath.
Location: Found on the outer layer of the neuron extensions, usually on the axons of
sensory and motor neurons.
Structure: made up of Schwann cells and shown as a grey coating in the diagram above.
Function: It enables the neuron to quickly transfer or propagates an impulse, the
myelinated axons carry impulse up to 150 meters per second. Non-myelinated axon travels
in about 0.5 to 10 meters per second.
Disease: An autoimmune disease called multiple sclerosis (MS) causes the white blood cells
to attack the protective myelin covering of neurons, and sometimes destroys it. This
damage interrupts the normal movement of nerve impulses along the axons. The
symptoms of MS vary greatly from person to person, ranging from problems with vision
and coordination to partial or even complete paralysis.
Draw and label a sensory neuron. Make sure the following are labelled: axon, cell body,
dendrite, sensory receptor, myelin sheath and direction of nerve impulse. Then note how
the length of the dendrite and axon differs compared to a motor neuron and interneuron.
Why can an impulse traveling along an axon not reverse its direction?
The sodium-potassium pump has not restored the resting potential immediately behind the
action potential.
Lesson 2- Neuron Transmission
Thoroughly explain the steps involved in the conduction of one nerve impulse in a neuron.
Use the graph template below. Sketch an action potential - label the axes and the 4 stages of
a nerve impulse. Then, underneath your graph, describe the concentrations of ions in Stage
1 and the movement of ions in stages 2-4.
A. The membrane is at resting membrane
potential (RMP), in this case -70 mV
B. As an impulse passes the microprobe, the
potential reverses to +40 mV. This is
called depolarization.
C. As the impulse moves on, the membrane
returns to resting potential. This is
called repolarization.
D. During the period after repolarization, the membrane is in a recovery (refractory)
period.
E. action threshold, below a certain amount of stimulus a neuron will not fire. This
important principle in action potential is called the all-or-none response. The neuron either
reaches threshold stimulation and fires (initiates an impulse), or it doesn't reach threshold
stimulation, and nothing happens. Individual neurons cannot vary the way they carry
action potentials. For variation in sensation to occur, various numbers of neurons fire.
Hitting your thumb with a hammer causes a huge number of neurons to fire. Gently
touching the hammer only stimulates a few. The brain interprets the number of neurons
firing as variation in stimulation.
the distribution of potassium K+ (more inside)
and sodium Na+(more outside) and organic anions
(negatively charged) (more inside)

the overall uneven balance between positive
and negative ions between the inside and outside
causes a potential difference (measured in millivolts)
of -65mV, which is 65/1000's of a volt.

This uneven ion distribution creates a condition
called Resting Membrane Potential (RMP) when the
neuron is not conducting an impulse.
Steps of Action Potential:
1.
2.
3.
4.
5.
6.
7.
8.
Sodium gates open
Sodium rushes into the cell
With more sodium ions inside than potassium ions outside, cell depolarize
Potassium gates open
Potassium ions rushes out
Cell repolarized
Sodium and potassium pump restores original cell distribution
Neuron ready for another stimulation action potential
What are the structures labelled “X” and what do they collectively produce?
Schwann cells collectively produce myelin
sheaths.
In a neuron, the correct order of
structures that a nerve impulse
passes through is
dendrite → cell body → axon
Explain saltatory conduction
The way where the impulse jumps from node to node. A faster way to travel down the axon
than travelling without myelin.
Lesson 3- Synaptic Transmission
Label the following diagram by drawing a label line from the term to the correct structure.
Explain how neurotransmitters are released from an axon bulb and what their effect on the
next neuron can be. Start with the action potential Na+/K+ reaching the axon bulb.
The swelling at the end of the axon. This is called the axon bulb. The axon bulb contains vesicles
loaded with protein molecules called neurotransmitters. The two neurons do not touch each
other. Instead, they are separated by a tiny gap called the synaptic cleft.







The action potential Na/K reaches the axon bulb, where it causes the bulb to
increase its calcium permeability.
The calcium ions then rush in.
The vesicles containing neurotransmitter molecules then fuse with the presynaptic
membrane, causing the neurotransmitter to be released into the cleft.
Once released they diffuse across the postsynaptic membrane, where they can
attach to receptor sites that are embedded.
These receptors are Na gates that get opened by the neurotransmitter’s presence.
It causes the postsynaptic cell to go into action potential
The next cell then carries the impulses again.
What happens to neurotransmitters after they are released from the synaptic vesicles? Why
does this happen?





The neurotransmitters only exist in the cleft for a short time.
Enzymes are released from the cleft to break them down.
In some synapses, the neurotransmitter is recycled back to the vesicles.
Removing the neurotransmitter prevents the continued stimulation of the postsynaptic
cell.
The transmission across a synapse is one way only.
Controlling synaptic transmission:






An impulse is usually initiated at a receptor or in the CNS.
The synapse may be in the excitatory or the inhibitory state.
Integration occurs when neurons take all these together and sum them up in a
process.
Have you noticed that while playing a sport, you might be slightly injured but
not notice?
Inhibitory neurons are firing on the interneurons that would normally be stimulated by
excitatory neurons.
These inhibitory neurons cancel the input from the excitatory neurons and cause the CNS to be
unaware of the input.
Neurotransmitter
Site of Activity
Noradrenalin/adrenalin*
Sympathetic Nervous System - Your emergency response
system
Noradrenaline is excitatory.
Parasympathetic Nervous System -Your normal state
system
Acetylcholine
Acetylchline is inhibitory and almost always slows
activities.
Seratonin
Brain—produces happy feelings, prevents depression
Dopamine
Brain —produces sensation of pleasure, controls
movement
Gastrin*
Digestive System
Cholecystokinin*
Digestive System
Vasopressin*
Circulatory System
Oxytocin*
Reproductive System
Corticotropin*
Endocrine System
Explain how drugs affect the neurotransmitters in the synapse and elaborate on two of
these effects with specific drug examples.
1. bind to postsynaptic receptor sites and block neurotransmitters from attaching
2. prevent reabsorption and recycling of neurotransmitters back into presynaptic vesicles
3. inhibit or promote the release of neurotransmitters
4. destroy neurotransmitters
Painkiller drugs like acetaminophen (Tylenol) inhibit neurotransmitters by binding to the
postsynaptic membrane receptor sites so that the pain sensation message can't be
transmitted between neurons.
Cocaine blocks the reabsorption and recycling of dopamine, increasing pleasurable feelings.
It is addictive because it becomes required for a person to feel pleasure. Withdrawal causes
an overwhelming sense of displeasure.
Prozac blocks the reabsorption and recycling of serotonin, causing a prolonged happy
feeling. Serotonin reduces anxiety, fear, insomnia (sleeplessness) and restlessness, and
people who produce low amounts of serotonin may suffer from depression. Prozac
counteracts this condition.
Describe the symptoms of Parkinson’s disease. How are these symptoms related to the
neurotransmitter dopamine?
The symptoms of Parkinson’s disease are stiffness in the legs and lack of expression. The
purpose and function of dopamine are to control movement in humans, as well as being
able to produce the sensation of pleasure, which is emotional.
Lesson 4- Reflex Actions
Most neurons are organized into circuits with the following parts: receptor cells  sensory
neuron  interneuron  brain  interneuron  motor neuron  effector cells (muscle
or gland)
There is another circuit called the reflex arc. Explain what a reflex arc is and state the one
part that is different from the regular neuron circuit above. Then label the following path of
a reflex arc.
The Reflex action is an automatic response to a stimulus.
The Reflex arc involves:
1. Sensory receptors
2. Sensory neuron
3. Interneuron
4. Motor neuron
5. Effector organ
It bypasses the brain during the action.
What is the purpose of the reflex arc?
The purpose of the reflex arc is to ensure quick responses to environmental input. The CNS
has little to no input. These reflexes allow quick responses to immediate threats that can be
avoided by reflexive actions. Many reflexes maintain fluid motion as input from one part of
the body causes an immediate response from another part.
2 types of reflexes:
Simple reflex: The brain is not aware of the first responses.
Conditioned reflex: Involves previous learning so that the body responds subconsciously.
Do early evolved animals, such as jellyfish and sea anemones, have more reflex actions than
humans or less? Explain your answer.
I would think that animals such as jellyfish would have more reflex actions, as most of their
actions don’t require any input from their brain or they don’t have one at all. Meanwhile,
most of the actions from a human would require a lot more brain input, hence most of our
actions are controlled by the brain.
Lesson 5- Divisions of the Nervous System
Fill in the blanks to complete the Nervous System organization chart.
What is the function of the central nervous system (CNS)? What type of neurons are only
found in the CNS?
The CNS uses interneurons to process information received from various sensory neurons and
then to send responses back out to the rest of the body via motor neurons. Interneurons are only
found in the CNS.
The spinal cord also has a learning function that allows you to complete certain actions like
biking or walking.
What is the function of the peripheral nervous system (PNS)? What type of neurons are the
PNS mostly made up of?
The PNS determines how our muscles and organs respond to output from the CNS. It is made up
of sensory and motor neurons. The PNS is further subdivided into two divisions—
the somatic nervous system (SNS) and the autonomic nervous system (ANS). Both systems
control motor neurons.
Where are the nerves of the peripheral nervous system found?
They are found outside of the CNS and the Brain.
Summarize the parts of the Peripheral Nervous System in the following table.
somatic nervous system
autonomic nervous system
sympathetic nervous system
parasympathetic nervous
system
The somatic system includes all motor neurons
involved in controlling voluntary(conscious) muscle
movements. Blinking and pulling your hands away from
hot stoves are SNS controlled.
The control of various organs that is not conscious is
done by the ANS. Pumping blood, breathing, and
digesting food. This frees up the brain to process more
important stuff.
The motor fibers of the sympathetic works to create a
fight or flight response. Main neurotransmitter used is
Norepinephrine. The adrenal gland above the kidney
releases epinephrine or adrenaline during the fight or
flight process.
Things are running smoothly, and the body returns to
normal conditions. Main neurotransmitter used is
acetylcholine.
Now briefly summarize the peripheral nervous system by taking the keywords from your
completed chart above to answer the following questions:
What is the function of the somatic nervous system?
Control voluntary muscle movements.
What is the function of the autonomic nervous system?
To Control the involuntary muscles movements such as the heart pumping or the digestion
of food.
What are the names of the autonomic divisions and what are the short phrases that help us
remember their functions?
Sympathetic: fight or flight
Parasympathetic: Rest or digest.
Lesson 6- The Brain
Complete the following table. Once you have defined each structure, label it on the diagram
below the table.
cerebrum
sensation, thought processes, motor control
cerebellum
organizes outgoing motor impulses so motions are coordinated and
smooth, controls balance and posture
hypothalamus
connects the brain with the endocrine organs by releasing
hormones that influence pituitary secretions
thalamus
receives and routes all incoming sensory information to the upper
brain
corpus callosum
medulla oblongata
pituitary
connects the two sides of the brain; information moving from one
half (hemisphere) of the brain to the other is routed through the
corpus callosum
controls basal metabolic functions - breathing, blood pressure, heart
rate, and many reflexive actions, such as coughing, vomiting,
hiccupping, and swallowing
releases hormones that control the endocrine system; because of this,
the brain controls such functions as sexual maturity, the menstrual
cycle, metabolic rate, and water concentration in the blood
One way that the brain controls the rest of the body is through neuro endocrine control.
This is when the nervous system controls the release of hormones into the blood that travel
in the circulatory system to the target organ or gland. Once homeostasis is reached, the
target organ or gland can then send negative feedback to the brain to stop (inhibit) the
hormone release. Summarize this process using the chart from the lesson. Start with the
hypothalamus, in the brain.
The hypothalamus receives information from the brain and monitors hormone
levels in the blood. It responds to the info by sending hormones to the pituitary gland
to release more hormones. Both are called endocrine glands because they produce
hormones released directly into the bloodstream and carried to other body parts.
Notice that the pituitary has two portions—the anterior pituitary (closer to the front
of the brain) and the posterior pituitary. The function of the anterior pituitary is
more diverse than that of the posterior pituitary. Also, notice all the target
tissues/organs/glands for the pituitary hormones and the hormones that are
released from these targets into a feedback loop -the red pathway.
This flowchart summarizes a
feedback loop in which
the hypothalamus first produces
a releasing hormone (RH), under the
direction of the brain. This RH causes
the anterior pituitary to release
a stimulating hormone (SH), which
in turn causes a target
gland/organ to produce a particular
hormone. This hormone has
an inhibitory effect on both the
hypothalamus and the anterior
pituitary, slowing the output of each
respective hormone. This is negative
feedback because it inhibits
production. In a few cases, a
feedback loop can be positive.
The pituitary gland (in the brain) releases a hormone into the blood that travels to the
adrenal glands on your kidneys. The adrenal glands then release adrenaline to give you that
so called “adrenaline rush”. The adrenal glands also release other hormones. Complete the
following chart to summarize the region of the adrenal gland where the hormone is
released from, the name of the hormone and its target.
Region of Adrenal Gland
Release
Adrenal cortex
Adrenal medulla
Hormone Secreted
Target
Cortisol
Aldosterone
Sex hormones
All tissue
Kidneys
Skin, muscles, bones, and
sex organs
Cardiac and other
muscles.
Adrenaline (epinephrine)
Noradrenaline
(norepinephrine)
Chapter 12- Urinary System
Lesson 1- Urinary System Anatomy
List the five major functions of the urinary system.
1. Excretion of urea
2. Regulation of blood pressure by regulating water concentration
3. Regulation of pH
4. Release of hormone Renin, important in Na and water regulation of the blood.
5. The release of the Hormone Erythropoietin is important for the red blood cell
oxygen carrying capacity.
Label the structures on the diagram and complete the structure functions.
Structure
Function
renal cortex
The outer region of the kidney that contains most of the nephron
tubules, including the glomerulus of each nephron
renal medulla
The central region of the kidney contains the nephron collecting
ducts and Loops of Henle.
renal pelvis
receives urine from the collecting ducts and sends it on to the ureter.
ureter
carries urine to bladder from each kidney
urinary bladder
stores urine until released in urination
urethra
carries urine from the bladder and out of the body
What are the functions of the renal artery and renal vein? Label them in the above diagram.
The renal artery brings the blood high in oxygen and urea to the kidney for filtration.
The renal vein brings the blood low in urea and low in oxygen away from the kidney
back to the heart and lungs.
Lesson 2- Nephron & Urine
Complete the blood vessel and nephron part function statements in the following table:
Structure
Function
afferent arteriole
Carries blood from the renal artery to the Glomerulus.
glomerulus
A loop of capillaries that carries blood from the afferent arteriole
to the efferent arteriole.
The glomerulus is surrounded by the Glomerular capsule and both
these structures work together to filter the blood, starting to form
urine.
efferent arteriole
Carries blood from the glomerulus to the peritubular capillary
network.
peritubular
capillary network
(PCN)
Carries blood from the efferent arterioles to the renal vein
glomerular or
Bowman’s
capsule
proximal
convoluted tubule
loop of Henle
distal convoluted
tubule
collecting duct
The process that occurs here is pressure filtration
Small molecules such as water, urea, salts. Glucose, wastes, and
amino acids are filtered out of the blood and large molecules such as
proteins and blood cells stay in the blood.
The process that occurs here is selective reabsorption.
The molecules involved are water, glucose, and amino acids.
The process that continues here is selective reabsorption
The molecules involved are water, Na, Cl.
The process that occurs here is tubular secretion.
The molecules involved are large molecules such as molecules left
over from muscle metabolism, hormone breakdown, and drugs
such as antibiotics.
Blood pH is balanced with either H moving out of the blood into the
filtrate or HCO3 moving into the blood from the filtrate.
The process that continues here is selective reabsorption.
The molecule involved is water.
Also, urine is collected here and then it empties into the urethra to be
carried on to the bladder for storage and eventual excretion.
You can check your
answers for the above
questions in the Show It
section of the lesson.
Now label the structures
listed in the table above on
the following nephron
image. It is intentionally
not the same image as the
ones in the course content,
so it may be helpful to
colour in the blood flow
before you begin labelling.
List the pathway of a red blood cell from the aorta to the inferior vena cava through the
nephron.
Renal artery – afferent arterioles – glomerulus – efferent arterioles – peritubular capillary
network – loop of nephron – renal vein
Describe how the following processes contribute to the formation of urine.
a) pressure filtration
The blood is under pressure, which causes it to excrete all small molecules like
water, glucose, amino acids, salts, and wastes. All are filtered out and go into the
bowman capsule into the nephron. Which begins the urine formation.
b) selective reabsorption
The filtrates from the bowman’s capsule move into the nephron, where it enters the
proximal convoluted tubule. Water from the dilute filtrate starts to be re-absorbed
into the Peritubular capillary network. This reabsorption of water concentrated the
urine content. The Glucose and amino acids are reabsorbed by carrier proteins.
Water is absorbed in the descending loop and most ions like Na and Cl are pumped
out from the ascending loop of the loop Henle. Chloride ions (Cl-) move by attraction to
the Na+, resulting in a salty environment surrounding the loop of Henle and the
collecting duct. This hypertonic environment causes water to move by osmosis out of
the nephron, and back into the blood of the peritubular capillary network, further
concentrating the urine in the nephron.
Reabsorption accounts for about 98% of the glomerular filtrate. Of the 100 milliliters of
filtrate, only 2 millilitres find their way into the urine. This is a good thing. Otherwise, we
would die of dehydration!
c) tubular secretion
Tubular secretion is the second way that molecules and ions, that were not initially
pressure filtered into the nephron at the glomerular capsule, can move into the nephron.
Tubular secretion, by active transport, occurs across the wall of the distal convoluted
tubule (DCT) and into the urine. Molecules left over from muscle metabolism, hormone
breakdown, and drugs such as antibiotics are removed from the blood in this way.
An ion that can be tubular secreted at the DCT is H+. It can be secreted to control blood
pH (~7.4). If blood pH is too acidic (less than 7.4) then H+ can be secreted from the
blood into the DCT to be excreted in the urine. Another ion that can be tubular secreted
at the DCT is HCO3- It can be secreted if blood pH is too basic.
List the final components of urine:
96% water – relative concentration of water.
Thousands of different compounds: Chloride, potassium, sodium. Amino acids and
glucose and bile.
Urea is a result of protein breakdown that releases nitrogen compounds (i.e.,
ammonia). Ammonia is toxic, so is quickly converted to urea in the liver.
Small hormone molecules result from the breakdown of hormones.
Creatinine is a waste product produced by the muscles.
Ammonia is produced, once the urine is exposed to bacterial action outside of the
body, and this ammonia produces diaper rash in infants and give that kitty litter
that overpowering smell!
Lesson 3- Urinary System Hormones
Complete the following table.
hormone
source gland
site of action
function
antidiuretic
hormone
The posterior
pituitary gland in
the brain.
The cells in
the
nephron’s
collecting
duct and
DCT.
ADH is an anti-diuretic. It has the
opposite effect of a diuretic like
caffeine or alcohol. ADH stimulates
the nephron to increase the
reabsorption of water back into the
blood. This causes a decrease in the
amount of water in the urine, so
there is less urine and more
concentrated urine. This causes
urine to be a darker yellow colour.
Controlled by the
Hypothalamus, as
it detects different
water
concentration
levels.
The cells in the DCT and collecting
duct become more permeable to
take in more water.
This is a negative
feedback system
because the
decrease in the
water
concentration in the
blood stimulates a
series of events that
reverse the
imbalance.
Adrenal cortex
aldosterone
Caused by Renin,
produced by the
juxtaglomerular
apparatus.
If the water concentration in the
body falls, the hypothalamus would
signal for more ADH to cycle more
water for the body.
Nephron’s
collecting
duct and
DCT.
The aldosterone affects the
nephron's collecting duct and distal
convoluted tubule, causing
reabsorption of Na+ into the blood
and secretion of K+ into the urine. As
more Na+ is reabsorbed, more water
is reabsorbed. This increase in
water and salt results in an increase
in blood volume, resulting in an
increase in blood pressure.
Recall that the reabsorption of water
is driven by Na+ concentration. More
salt in the peritubular space means
the tonicity of the space increases,
drawing water along, which is
reabsorbed. This is also a negative
feedback system.
Describe how the hypothalamus, posterior pituitary gland, ADH and the nephron achieve
homeostasis of water levels in the blood.
The hypothalamus detects the water concentration level in the blood.
If the level falls, it will signal the posterior pituitary gland to release ADH.
The ADH then targets the cells in the DCT and the collecting duct of the Nephron.
It makes the cells more permeable to water, which causes more water to be
reabsorbed back into the Peritubular capillary bed.
As the water concentration in the blood increases, then the hypothalamus will slow
the production of ADH.
Describe aldosterone’s negative feedback loop for controlling blood pressure.
The juxtaglomerular kidney cells, which are sensitive to the change in blood
pressure are on the outside of the glomerulus.
When the pressure drops, Renin will be secreted, and it travels to the Adrenal
cortex.
The aldosterone will be released, and it travels to the DCT and collecting duct.
Na ions will be reabsorbed along with water and K ions will be in the urine.
The increase in water and salt results in an increase in blood volume, which
increases blood pressure.
Quiz review:
Which of the following symptoms might be an indication of kidney failure?
Protein in the urine
Chapter 13- Reproductive System
Lesson 1- Sexual Orientation and Gender Identity
As you are going through the lesson, complete the following table with summary notes.
sex
The World Health Organization (WHO) defines the working definition of
sex as “the biological characteristics that define humans as female or
male.
“Biological sex refers to the objectively measurable organs, hormones,
and chromosomes. Female = vagina, ovaries, XX chromosomes; male =
penis, testes, XY chromosomes.
intersex
Intersex is an umbrella term used to define someone who's sexual and
reproductive characteristics do not fit perfectly into our standard
definitions of male or female
2-spirit
Used by the indigenous community to refer to a person who has the
spirits of both a men and women.
hermaphrodite
Hermaphrodite is an older term generally intended to refer to the idea of
someone who has full male and full female sexual and reproductive
organs- a biological impossibility. The term hermaphrodite is now
considered to be out of date and offensive to intersex people.
chromosome
Chromosomes are the structures in our cells that contain our DNA -our
genes. The sex chromosomes are X and Y and we inherit one sex
chromosome from each parent. Most combinations are XX or XY. The
number of people born without a XX or XY chromosome pairing is 1 in
1666 births.
As you work your way through the SOGI 123 Information Sheet: Intersex Conditions, jot
down any further questions that you might have and one piece of information that you took
away from watching the videos.
Intersex is different from transgender, as the transgender represents your gender
identity, while intersex refers to people with biological characteristics.
Is the gender normalizing surgery a must or just a decision that is made to fit the
intersex individual in?
Pick one intersex condition to summarize.
Klinefelter syndrome (1 or 2 in 1000): Men with Klinefelter syndrome inherit an X chromosome
from their mother, a Y chromosome from their father, and an extra X chromosome from either
parent, resulting in an XXY karyotype. Infants usually appear to have normal male genitals, though
the testes may be small and firm. At puberty, boys with Klinefelter might not develop much body
hair and they may develop breasts. Testosterone injections can help men with Klinefelter syndrome
virialize more strongly.
Lesson 2- Male Reproductive Anatomy
As you are going through the lesson, complete the following table on male reproductive
anatomy.
Penis and urethra
deposit sperm inside the vagina of a female during copulation. It
also contains the final few centimetres of the urethra, so it is the
exit point for urine.
scrotum
A sac of skin and muscles that contains the testes. Plays an
important role in temperature regulation. As body temperature
drops, the muscles in the wall of the scrotum contract, pulling the
testes up against the body wall and helping them to retain heat.
Sperm formation in the testes will only take place at a few degrees
below body temperature, so the testes are suspended outside the
body in order for this to happen.
testes
produce sperm and the male reproductive hormone testosterone.
epididymis
a folded tube in which sperm spend time acquiring their tails and
maturing, gaining mitochondria.
vas deferens
the tube that carries sperm from the epididymis through the
abdominal cavity, past several glands, and finally to the urethra in
the penis.
seminal vesicles
produce fluid which includes fructose that sperm use as an energy
course for movement and prostaglandin hormones that cause
muscle contractions in the uterus. These contractions aid the
passage of sperm into the uterus.
prostate gland
a gland that produces a fluid that contains basic pH compounds to
neutralize the acidity of the vagina. The prostate muscles provide
much of the force needed for ejaculation to occur.
bulbourethral
glands (Cowper’s
glands)
small glands that secrete a thick clear mucus fluid that neutralizes
any trace amounts of urine in the urethra and assists the sperm in
their movement towards an egg. The thick clear mucus helps to
lubricate the penis for sexual intercourse.
The fluid from the bulbourethral glands is secreted before
ejaculation and may contain some sperm, which reduces the
effectiveness of the coitus interruptus (penis withdrawal before
ejaculation) birth control method.
Sperm anatomy
Draw and label a sperm cell below. List the function of each region.
labelled drawing:
Functions:
Tail: Sperm cells have a tail, which is a
flagellum. This tail allows the sperm to
move to carry DNA to the egg.
Middle piece: mid-piece "motor"' that is
packed with ATP-producing mitochondria
that produce energy for the sperm's tail to
move.
The head of the sperm contains the nucleus
with the DNA.
The acrosome cap of the head of the sperm
contains enzymes that will be released to
penetrate the egg.
Describe the pathway of sperm from where it is produced to where it may meet an egg in
the female body.
From the testes, where sperm are produced, the cells travel to the epididymis where they
mature. From there, during orgasm, muscular contractions of the epididymis and the vas
deferens propel the sperm out of the vas deferens. As they move, they pass several glands,
each of which contributes to the seminal fluid (semen). Without these fluids, sperm are
incapable of fertilizing an egg. Sperm first pass the seminal vesicles, then the prostate
gland, and finally the bulbourethral glands. The final pathway of sperm is the urethra,
which leads through the penis out of the body. Once the sperm leaves the penis, it travels
through the female body starting in the vagina, past the cervix, into the uterus and up into
the oviduct (fallopian tube) where it may meet an egg and where fertilization may occur.
Several natural or artificial things can prevent sperm from moving through this pathway.
A vasectomy is a male sterilization procedure where the vas deferens is cut and
tied/sealed off to prevent sperm from entering the urethra in the penis. Also scarring can
occur, which can be caused by bacterial infections of the inner lining of the vas deferens
tube. Sexually transmitted diseases, such as syphilis and gonorrhea, can also produce
scarring and reduce fertility.
Note that reduced fertility means there is a reduced chance of producing a fertilized egg
(pregnancy). Sterility means the chance is zero.
ORGASM in Males:
When a man is sexually excited, the arteries in the penis relax and widen. Increased
blood flow causes the penis to enlarge and become erect. Also, the veins that normally
carry blood away from the penis are compressed, and this maintains an erection.
When sexual stimulation intensifies, sperm (400 million +) enter the urethra from the
vasa deferens, and the accessory glands contribute secretions to the semen (2-6ml).
Once semen is in the urethra, rhythmic muscle contractions cause it to be ejaculated
from the penis in spurts into the vagina. During ejaculation, a sphincter normally closes
off the urinary bladder so that no urine enters the urethra, and no semen enters the
bladder.
Orgasm occurs at the climax of sexual stimulation. Blood pressure and pulse rate rise,
breathing quickens, and the penis and other body muscles contract rhythmically. A
sensation of intense pleasure is followed by relaxation when the penis returns to its
normal size.
Lesson 3- Male Reproductive Hormones
The testes have two roles in reproduction. They are:
1. To produce hormones
2. To produce sperm cells
Explain where and how sperm is produced:
Sperm production occurs in the seminiferous tubules. Sperm are gametes that result
from the cell division of meiosis. It occurs from puberty to death and requires a
temperature less than the body temp.
Summarize the role of the following hormones in the male reproductive system. Make sure
you include where the hormones are released from.
Produced in the interstitial cells.
testosterone
Controls the development of primary sex structures such
as the testes, penis and all other structures.
Development of the secondary characteristics. growth of
body hair, enlargement of larynx and lengthening of vocal
cords (causes voice to deepen), growth of male adult physique
(generally taller and broader shoulders and longer legs to
trunk than the female physique)
Gonadotropic Releasing Hormone
GnRH
FSH
released by hypothalamus and stimulates the anterior
pituitary to release two controlling hormones -FSH and
LH
Follicle Stimulating Hormone
Stimulate the production of sperm
LH
Luteinizing Hormone
Stimulates the production of testosterone
Explain how testosterone levels are controlled in males.
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Low testosterone levels in the blood will stimulate the hypothalamus to secret
the GnRH.
The GnRH stimulates the anterior pituitary gland to release LH.
LH stimulates the testes to stimulate more testosterone
This increased level of testosterone exerts negative feedback control over the
hypothalamus.
Brain is the control of the sexual functioning:
Before puberty, FSH and LH levels are very low.
Testosterone and Negative feedback scenario questions
a) A boy suffered from a brain tumour center in the hypothalamus. In order to save his
life, part of his hypothalamus was removed, and his GnRH production and release
were drastically reduced. How might his puberty be affected?
Less developed testes and penis. Less secondary features like low body hair and a
higher voice than normal. Stunned growth of muscle and shorter legs. Less sperm
production
b) Use your understanding of the neuroendocrine control of the testes by a negative
feedback loop. What treatments might be possible for the boy, if he chose to be
treated?
To take artificial hormones:
GnRH injections FSH and LH injections.
Testosterone-like drugs: Anabolic steroids to help with puberty.
c) Would this be a short-term treatment to ‘kick start’ puberty or would ongoing
treatment be necessary? Explain your answer.
It would be a long-term treatment, as hormones break down during longer periods,
and will need to be replaced if the body is not producing the correct amount needed.
d) Some male athletes take artificial testosterone (an anabolic steroid), at much higher
levels than therapeutic doses. They do this in order to enhance their physique, but
one of the adverse effects is atrophy (reduced size) of the testes. Explain why this
occurs.
The side effect happens because the amount of testosterone in the blood is
already high, which causes the negative feedback loop to not function properly.
The hypothalamus stops sending signals to the anterior pituitary gland, which
then stops the release of LH to signal the testes to continue producing
testosterone, which causes them to shrink.
The eventual effects are a decrease in sperm count. Abnormal sperm
development and infertility.
Lesson 4- Female Reproductive Anatomy
As you are going through the lesson, complete the following table with notes about the
female reproductive anatomy including function(s), when appropriate.
ovaries
To produce egg cells and to produce hormones.
Egg production, called oogenesis, takes place in the follicle of the ovary.
Hormone production occurs in the developing follicle -mainly estrogenand the corpus luteum -primarily progesterone. Hormone production is
regulated by secretions from the anterior pituitary.
fimbriae
The cilia of the fimbriae sweeps the eggs into the oviduct
(fallopian tube)
oviducts (fallopian
tubes)
the egg is moved by muscular contractions. This journey lasts
for one to two days. It is during this time that the egg must be
fertilized for it to develop into an embryo. Eventually the egg
enters the uterus, a hollow muscular organ.
uterus
A hollow organ lined with endometrium. The eggs enter here
from the fallopian tube. Very elastic. Protection
endometrium
Nourishes the fertilized eggs by providing oxygen and
nutrients through diffusion.
cervix
The opening of the vagina canal from the inside. Allows fluid
to flow inside and out of the uterus.
vagina
Very elastic. Can expand when needed for a birth canal and
when receiving a penis during sex.
vulva
A series of folded tissues that surrounds the vaginal opening.
Protect the internal parts of the female reproductive system.
clitoris
contains a collection of nerve endings, similar in number to
those in the penis in males. Like the penis, the clitoris contains a
shaft of erectile tissue that becomes engorged with blood during
sexual stimulation.
Male
Female
Testes
Ovaries
Penis
Clitoris
lower surface of penis
labia minora
scrotum
labia majora
When a woman is sexually excited, the labia, the vaginal wall, and the clitoris become
engorged with blood. The vagina expands and elongates. Blood vessels in the vaginal
wall release small droplets of fluid that seep into the vagina and lubricate it. Mucussecreting glands on either side of the vagina also provide lubrication for entry of the
penis into the vagina. Although the vagina is the organ of sexual intercourse in females,
the extremely sensitive clitoris plays a significant role in the female sexual response.
The thrusting of the penis and the pressure of the pubic symphyses of the partners act
to stimulate the clitoris, which may swell to two or three times its usual size.
Orgasm occurs at the climax of sexual stimulation. Blood pressure and pulse rate rise,
breathing quickens, and the walls of the vagina, uterus, and oviducts contract
rhythmically. A sensation of intense pleasure is followed by relaxation when organs
return to their normal size.
Lesson 5- Female Reproductive Hormones
The menstrual cycle involves two simultaneous cycles – the ovarian and the uterine cycle
Ovarian Cycle
Test your understanding of the Ovarian Cycle by matching the following descriptions to the
correct spot on the graph image below. Write each letter in the circle of the area that best
describes the statement.
A. Both LH and FSH peak at day 13, but LH peaks much higher triggering ovulation.
B. End of Luteal Phase with corpus luteum disintegrates.
C. Ovarian Cycle
D. FSH and LH levels decrease and remain at their lowest levels until the cycle begins
again.
E. FSH is initially higher and then decreases. LH is initially lower and then increases,
peaking at day 13
F. Ovulation
G. Follicle in the ovary is developing the oocyte (egg)
FSH stimulates the maturation of the follicle- in this case the egg, not sperm-and LH
stimulates the maturation of the remaining follicle tissue that is now called the corpus
luteum.
Ovarian follicular phase:
Primary follicles contain oocytes and begin producing the sex hormone estrogen. Then
Secondary follicles contain secondary oocytes and produce the sex hormones estrogen and
some progesterone. The final step is that the vesicular Graafian follicle develops.
Trace the development of the egg inside the primary follicle, to the secondary follicle,
and eventually the Graafian follicle. The secondary and Graafian follicles produce the
sex hormone estrogen and a much smaller amount of progesterone, which are released
into the bloodstream.
The ovulation of the egg is right in the middle of the process. Caused by the sudden
spike in LH. Women's body temperature drops slightly before ovulation and rises slightly
above after for several days to increase progesterone levels.
Ovarian luteal phase:
Ovulation occurs in the period when the egg is released. LH stimulates the maturation of
the remaining follicle tissue which is now called the corpus luteum. The corpus luteum
continues to secrete progesterone and then some estrogen, as the cycle continues. In
the end, it degenerates.
Uterine Cycle
Test your understanding of the Uterine Cycle by matching the following descriptions to the
correct spot on the graph image below. Write each letter in the circle of the area that best
describes the statement.
A. Progesterone levels peak
B. Estrogen levels peak
C. Estrogen and progesterone hormones levels drop before the cycle continues.
D. Uterus lining is in the proliferative phase and is building up.
E. Uterus lining is being shed as the egg from the previous cycle was not fertilized.
F. Uterus lining continues to develop and secrete mucus for the egg and potential sperm.
Now add the labels menstruation (menstrual phase) and proliferative phase days 6-13 and
secretory phase days 15-28 to the previous image. Summarize the details about each of
these phases on the next page.
While the ovary is involved with egg production, the uterus prepares for the egg's
arrival. The wall of the uterus is called the endometrium and this tissue goes through
three distinct phases, each corresponding to events within the ovary.
Uterine menstruation (menstrual phase)
days 1 to 5
endometrium developed in previous cycle is sloughed off if no fertilized egg is
present
often associated with discomfort and some pain
NOTE: If there is a fertilized egg, then the endometrium does not slough off and
the uterine cycle ceases as the embryo develops; this, too, is under hormonal
control.
Uterine Proliferative phase
days 6 to 13
endometrium thickens as it develops new tissue and blood vessels to prepare to
accept a fertilized egg.
Day 14 ovulation occurs. For an embryo to develop, the egg must be fertilized
within a couple of days of ovulation (fertilization- the union of the egg and sperm)
Uterine Secretory phase
days 15 to 28
endometrium secretes mucous, which accumulates in strands inside the uterus;
these provide a pathway for sperm that must swim through the uterus and into the
fallopian tubes to meet with the egg. Later the mucus traps the fertilized egg,
which eventually embeds into the uterine wall.
If the egg is not fertilized, the endometrium begins to degenerate, and the cycle
begins at day one again.
Low estrogen in the blood will cause the hypothalamus to produce GnRH, which
stimulates the anterior pituitary to produce FSH. FSH stimulates the ovary follicle to
produce primarily estrogen. This increased level of estrogen exerts negative feedback
control over the hypothalamus and stops (inhibits) the release of GnRH until estrogen
levels are low again.
Low progesterone in the blood will cause the hypothalamus to produce GnRH, which
stimulates the anterior pituitary to produce LH. LH stimulates the ovary corpus luteum to
produce primarily progesterone. This increased level of progesterone exerts negative
feedback control over the hypothalamus and stops (inhibits) the release of GnRH until
progesterone levels are low again.
Briefly explain the relationship between the named structures/hormones in females as a
final reproduction task.
1. FSH and the follicle
The FSH stimulates the growth of the follicle, which is the egg.
2. LH and the corpus luteum
The LH stimulates the maturation of the remaining follicle tissue called corpus
luteum.
3. ovary and uterus
The ovary is involved in egg production and the uterus prepares for the arrival of the
egg at the same time.
4. follicle and endometrium (uterus wall)
The endometrium follows the events happening in the ovary and goes through 3
different phrase that corresponds to each different phrase.
5. endometrium (uterus wall) and fertilized egg
The endometrium develops as a thick tissue to embed the egg and provide oxygen
and nutrients to it.
6. corpus luteum and endometrium (uterus wall)
The corpus luteum produces progesterone, which makes the endometrium thicken
furthermore and secretes mucous. This mucus provides a pathway for the sperm to
swim through and meet the egg. The mucus later traps the egg to embed itself in the
uterine wall.
7. HCG and implantation
HCG is a hormone where it has the same effect as LH. This hormone’s presence overrides
the brain as the control of the reproductive system. The HCG stimulates the production of
progesterone to maintain the endometrium.
What would happen to the embryo if no HCG were produced?
The corpus luteum would disintegrate, ceasing the production of progesterone. The
anterior pituitary would begin to produce greater levels of FSH and the endometrium
would respond by disintegrating, causing the embryo to be miscarried.
As the embryo develops it contributes tissue to the development of the placenta. The
endometrium also contributes to tissue. Think of the placenta as two interlocking hands
touching the other but not directly connected. Where the two tissues touch there are
blood vessels from each of the endometrium and the embryo. Across this narrow gap,
the embryo receives oxygen and nutrients. It also passes nitrogen wastes and carbon
dioxide to the mother, whose organs dispose of them. Eventually, the tissues of the
placenta take over progesterone production, suppressing the production of FSH by the
brain and assuring its own maintenance.
8. oxytocin and positive feedback loop
As the end of pregnancy nears, the uterus begins to contract, forcing the fetus into the
bottom of the uterus, where it applies pressure to the cervix. As the cervix begins to
stretch, it sends neural messages to the brain, which signals the release of oxytocin
from the posterior pituitary. Oxytocin stimulates more contractions, which result in
further stretching of the cervix. Contractions become more intense as oxytocin levels
rise.
Eventually, uterine contraction forces the baby through the vaginal canal, allowing the
cervix to contract back to it's normal size. This contraction of the cervix stops the neural
signals to the brain, which in turn stops the release of oxytocin. The uterus continues to
contract until it expels the placenta or after birth. After a few days, the uterus reverts to
its pre-pregnant size.
During pregnancy, the production of estrogen and progesterone causes the breast to
produce milk. After childbirth, levels of these hormones fall abruptly, and the anterior
pituitary begins to produce prolactin. It takes a couple of days of prolactin exposure to
fully prepare the breasts for milk production. If the baby is allowed to suckle on the
nipple, nerve connections with the brain stimulate the release of oxytocin from the
posterior pituitary. Oxytocin causes the contraction of milk-containing lobules in the
breast. The presence of oxytocin in breastfeeding mothers also stimulates their uterus
to revert to its normal size.