Human Systems
Endocrine, Reproductive, & Nervous
The Endocrine System
Glands that secrete hormones as a
chemical signal which is sent to
different parts of your body.
Helps maintain homeostasis
What are hormones?
• Chemical messengers that have a
physiological effect far from where
they originated.
• They travel through the
bloodstream
• Most are under the control of a
feedback mechanism.
Group Work!!!!
• Each group will be in charge of teaching about a pair
of hormones that may or may not work together.
–
–
–
–
–
•
•
•
•
•
Testosterone & Leptin
Thyroxin & Melatonin
Estrogen & Progesterone
Oxytocin & Prolactin
Insulin & glucagon
You will discuss where they originate
where they go
what their purpose is
how is homeostasis maintained.
Use drawing to help with presentation
Major Endocrine Glands
Sometimes the
glands come in
pairs…
Sometimes they
are alone…
Pathway
Example
Low blood
glucose
Stimulus
Pathway
Example
Stimulus
Suckling
Example
Pathway
Stimulus
Receptor
protein
Pancreas
secretes
glucagon ( )
Endocrine
cell
Blood
vessel
Hypothalamus/
posterior pituitary
Response
Hypothalamus
Neurosecretory
cell
Blood
vessel
Target
effectors
Sensory
neuron
Sensory
neuron
Hypothalamic
neurohormone
released in
response to
neural and
hormonal
signals
Neurosecretory
cell
Posterior pituitary
secretes oxytocin
( )
Blood
vessel
Hypothalamus
secretes prolactinreleasing
hormone ( )
Liver
Glycogen
breakdown,
glucose release
into blood
(a) Simple endocrine pathway
Target
effectors
Anterior
pituitary
secretes
prolactin ( )
Smooth muscle
in breast
Endocrine
cell
Response
Blood
vessel
Milk release
(b) Simple neurohormone pathway
Target
effectors
Mammary glands
Milk production
Response
Figure 45.2a–c
(c) Simple neuroendocrine pathway
A common feature
of control pathways
is a feedback loop
Receptor
Response
Stimulu
s
Effector
Homeostatic control of body temperature
Negative feedback: physiological changes that bring a value back
closer to a set point.
Message is sent by
thermoreceptors
Possitive
Feedbackamplifies the response
Types of Hormones & Their
Function
• Steroid hormones:
– Example is estrogen
– Function: increases thickness of uterine lining
• Proteins & Peptide hormones:
– Example is insulin
– Function: stimulates glucose uptake by body cells
• Amines derived from amino acids hormone:
– Example is thyroxin
– Function: increases metabolic rate
Basic Signal Transduction
Pathways
• INCLUDE:
– Reception
– Signal Transduction
– Response
Cell-Surface Receptors for Water-Soluble Hormones
SECRETORY
CELL
• The receptors for most
water-soluble hormones
• Are embedded in the plasma
membrane, projecting
outward from the cell
surface
• Insulin
• Prolactin
• Growth hormone
Hormone
molecule
VIA
BLOOD
Signal receptor
TARGET
CELL
Signal
transduction
pathway
OR
Cytoplasmic
response
DNA
Nuclear
response
NUCLEUS
Figure 45.3a
The same hormone may have
different effects on target cells
that have
• Different receptors for the hormone
• Different signal transduction pathways
• Different proteins for carrying out the
response
• The hormone epinephrine
• Has multiple effects in mediating the body’s response to
short-term stress
Different receptors
Epinephrine
a receptor
different cell responses
Epinephrine
b receptor
Epinephrine
b receptor
Glycogen
deposits
Vessel
constricts
(a) Intestinal blood
vessel
Figure 45.4a–c
Vessel
dilates
(b) Skeletal muscle
blood vessel
Different intracellular proteins
Glycogen
breaks down
and glucose
is released
from cell
(c) Liver cell
different cell responses
Intracellular Receptors for Lipid-Soluble Hormones
SECRETORY
CELL
• Steroids, thyroid hormones, and
the hormonal form of vitamin D
Hormone
molecule
VIA
BLOOD
• Enter target cells and bind to specific
protein receptors in the cytoplasm or
nucleus
• The protein-receptor complexes then
act as transcription factors in the
nucleus, regulating transcription of
specific genes
Figure 45.3b
(b) Receptor in cell nucleus
TARGET
CELL
Signal
receptor
Signal
transduction
and response
DNA
mRNA
NUCLEUS
Synthesis of
specific proteins
Local Regulators-convey messages
between neighboring cells
Cytokines
Growth Factors
Nitric oxide
Prostaglandins
Cytokines
• Initiates an immune response
Growth Factors
• Stimulate cell
division & growth
(proliferation) and
differentiation
• Must be present
in the
extracellular
environment
Prostaglandins help regulate
the aggregation of platelets
• An early step in the formation
of blood clots
• Help sperm reach the egg
• Help induce labor
• Send out an alarm by inducing
a fever and or inflammation
Figure 45.5
• The hypothalamus and pituitary integrate many functions of the vertebrate
endocrine system
• The hypothalamus and the pituitary gland
• Control much of the endocrine
system
The hypothalamus works in
conjunction with the nervous
system. It receives information
from the nerves and initiates
hormone production depending
on environmental conditions.
Figure 45.7
Hypothalamus
Neurosecretory
cells of the
hypothalamus
Axon
Posterior
pituitary
Anterior
pituitary
HORMONE
TARGET
ADH
Kidney tubules
Oxytocin
Mammary glands,
uterine muscles
Pituitary Gland:
-posterior: releases neurohormones made in the hypothalamus
-anterior: regulated by trophic hormones produced in the hypothalamus.
What hormones does the
posterior pituitary gland release?
Oxytocin-contract uterine muscles
during childbirth & mestration
Antidiuretic hormone (ADH)- acts on
kidneys to increase water retention
What hormones does the anterior
pituitary gland release?
• Other hypothalamic cells produce tropic hormones-these are hormones that
regulate endocrine organs such as the anterior pituitary gland & are
produced by neurosecretory cells in the hypothalamus
• These hormones are secreted into the blood and transported to the anterior
pituitary (aka adenohypophysis)
Neurosecretory cells
of the hypothalamus
Tropic Effects Only
FSH, follicle-stimulating hormone
LH, luteinizing hormone
TSH, thyroid-stimulating hormone
ACTH, adrenocorticotropic hormone
Nontropic Effects Only
Prolactin
MSH, melanocyte-stimulating hormone
Endorphin
Nontropic and Tropic Effects
Growth hormone
Portal vessels
Endocrine cells of the
anterior pituitary
Hypothalamic
releasing
hormones
(red dots)
HORMONE
TARGET
Figure 45.8
FSH and LH
Testes or
ovaries
TSH
Thyroid
Pituitary hormones
(blue dots)
ACTH
Prolactin
MSH
Endorphin
Adrenal
cortex
Mammary
glands
Melanocytes
Pain receptors
in the brain
Growth hormone
Liver
Bones
Antidiuretic Hormone (ADH) –produced in the
hypothalamus; stored & released from the posterior
pituitary gland
• Controls how much water is
reabsorbed & back into the
bloodstream.
– If ADH is secreted, the collecting
duct of the kidneys becomes
permeable to water & water leaves
by way of osmosis into the highly
hypertonic medulla of the kidney.
• Little to no urine volume
– Water is then reabsorbed back into
the bloodstream
- If ADH is not secreted, the collecting
duct remains impermeable to water
- Urine will then contain a high
amount of water.
Nontropic Hormones
The nontropic hormones produced
by the anterior pituitary include:
• Prolactin stimulates lactation in
mammals
• But has diverse effects in different
vertebrates
• MSH influences skin pigmentation
in some vertebrates
• And fat metabolism in mammals
• Endorphins
• Inhibit the sensation of pain
Growth Hormone
• Similar in structure
to prolactin
– Indicates they
evolved from the
same ancestral gene
(too much)
(too little)
*Some athletes take growth hormones to enhance performance but research shows
it has little impact provided the athlete is not deficient in GH to begin with.
Nonpituitary hormones help
regulate metabolism, homeostasis,
development, and behavior
• Thyroid Hormone
• Parathyroid Hormone
• Insulin and Glucagon
• Adrenal Hormones
• Gonadal Sex Hormones
• Melatonin
Nonpituitary hormones help regulate
metabolism, homeostasis,
development, and behavior
• The thyroid gland
–
–
Hypothalamus
Consists of two lobes located on the ventral surface of the
trachea
Produces two iodine-containing hormones, triiodothyronine
(T3) and thyroxine (T4)
• The hypothalamus and anterior pituitary
– Control the secretion of thyroid hormones
through two negative feedback loops
Anterior
pituitary
• The thyroid hormones
TSH
– Play crucial roles in stimulating
metabolism and influencing development
and maturation
Thyroid
T3
+
T4
• Hyperthyroidism, excessive secretion of thyroid
hormones
• Can cause Graves’ disease in humans
Figure 45.10
• Hypothyroidism, minimal to no secretion of thyroid
hormones
• Can cause weight gain, lethargy, & intolerance to cold
• In infants it can cause cretinism (low skeletal growth &
poor mental development
Parathyroid
Hormone
Why is the parathyroid
important?
Diabetes
• A disease characterized by hyperglycemia
– High blood glucose
TYPES OF DIABETES
Type I
Type II
β cells do not produce enough insulin
Body cell receptors do not respond
properly to insulin= insulin resistance
Can be controlled by the injection of
insulin
Can be controlled by diet
Autoimmune disease- immune system
attacks β cells & destroys them
Less than 10% of diabetics have this type.
Most common form of diabetes - 90%
Most often occurs in children & young
adults
Associated with genetic history, obesity,
lack of exercise, advanced age, & certain
ethnic groups
Adrenal Hormones: Response to Stress
• Epinephrine & norepinephrine stimulate the
“fight or flight” response.
– Nerve impulses from the brain stimulate the adrenal
medulla to release both hormones
– These hormones are released into the blood stream.
– They travel to the liver and muscle cells to break down
glycogen and release glucose.
•
•
•
•
Increase energy
Blood pressure
Breathing rate increases
Cellular metabolic rate rises
ALL PROMOTE
THE FLIGHT OR
FIGHT RESPONSE
More Adrenal
Hormones:
Response to
Stress
Steroid hormones from the
adrenal cortex are secreted
because of the stress stimulus
initiated by the hypothalamus
Hormones from adrenal cortex are corticosteroids.
-EX: glucocorticoids (cortisol)
mineralocorticoids (aldosterone)
It is suggested that both of these
hormones work together to maintain
homeostasis when the body is under
stress over a long period of time.
REPRODUCTION
HUMAN REPRODUCTION (sexual reproduction):
sperm, egg, & fertilization ensures genetic
variation in our species.
Bladder
Ureter
Seminal
Vesicle
Urethra
Ejaculatory
Duct
Vas Deferens
(sperm duct)
Penis
Epididymis
Testes
Scrotum
Prostate
Gland
Bulbourethral
Gland
Testosterone: Male Hormone
• Determines the development of male genitalia
during embryonic development
• Ensures development of secondary sex
characteristics during puberty.
• Maintains the sex drive of males throughout
their lifetime.
Oviduct (Fallopian Tube)
Ovary
Uterus
Bladder
Clitoris
Cervix
Urethra
Vagina
Rectum
The menstrual cycle
• Starts at puberty
• It’s a hormonal cycle lasting for ~28 days
– Times the release of the ovum (egg)
• For fertilization & implantation
• The inner lining of the uterus (endometrium)
grows thick (becomes highly vascular)
• If no implantation then blood vessels
breakdown (menstruation)
What are the hormone
levels at ovulation?
FSH, LH & estrogen= high
Progesterone = low
FSH- follicle stimulating hormone
LH- luteinizing hormone
Graafian follicle
Oocyte + zona pellucida
(glycoprotein coat)
For 10-12 days
Gonadotrophin
releasing hormone
Complete this chart
Hormones involved in the female menstrual cycle.
Hormone
Origin
Target
Causation
GnRH
Hypothalamus
Anterior
pituitary gland
Production of FSH & LH
FSH
Anterior
pituitary gland
Ovaries
Stimulate follicle growth &
production of oestrogen
LH
Anterior
pituitary gland
Ovaries
Stimulate follicle growth &
production of oestrogen
Oestrogen
Ovaries
Endometrium
Make endometrium highly
vascular
Progesterone
Corpus luteum
Endometrium
Maintains endometriums highly
vascular state
During ovulation what is happening
with the 4 hormones?
LH: is high
FSH: is high
Estrogen: is high
Progesterone: low
What is happening with the hormones
during menstruation?
All are low except FSH
As long as progesterone is being produced the endometrium will
not break down.
The hypothalamus will not produce GnRH as long as progesterone
levels & estrogen levels are high.
Therefore FSH and LH will remain at non conducive levels to
produce any other Graafian follicle.
Once the corpus luteum begins to break
down this lowers the levels of progesterone
and estrogen which signals the hypothalamus
to secrete GnRH
Natural Fertilization
• Occurs in the fallopian tubes 24-48 hours after
ovulation
• Zygote begins dividing and has divided many
times by the time it reaches the uterus for
implantation.
• As long as the endometrium is in a highly
vascular state, implantation will occur.
Problems couples may face with
having a baby
•
•
•
•
Low sperm count (in males)
Failure to achieve or maintain an erection
Do not ovulate regularly
Blocked fallopian tubes
One way to solve the problem…
• In-vitro fertilization:
– Female is injected with FSH for 10 days
• Ensures development of several Graafian follicles
– Several eggs are harvested surgically
– Male ejaculates into a container
– Harvested eggs are mixed with the sperm
– Observed under a microscope to determine which
eggs have been fertilized and are mitotically dividing
normally.
– 2 to 3 embryos are placed in the female uterus
– Leftovers are frozen & used later, if needed.
Ethical issues concerning IVF
FOR
• Allows couples who
normally would not be able
to have children to have
them.
• Unhealthy embryos are
eliminated for consideration
• Genetic screening can be
done prior to implantation
AGAINST
• Embryos not used are either
frozen or destroyed
• Legal issues with regards to
unused embryos if there is a
divorce.
• Genetic screening at embryo state
could lead to choosing desirable
characteristics
• IVF bypasses natures way of
decreasing the genetic frequency
of that reproductive problem
• IVF increases the chances of
multiple births & with it the
problems associated with multiple
births.
Reproduction & rearing of offspring
require free energy beyond that
used for maintenance & growth.
Reproductive strategies in response to
energy availability
• Food availability and ambient temperature
determine energy balance, and variation in
energy balance is the ultimate cause of
seasonal breeding in all mammals and the
proximate cause in many. Photoperiodic
cueing is common among long-lived mammals
from the highest latitudes down to the midtropics.
The Nervous System
OH MY!!!
CONSISTS OF THE BRAIN AND SPINAL CORD
Receive sensory information
from various receptors & then
interpret & process the
information.
If a response is needed some
portion of the brain or spinal
cord initiates a response =
motor response.
The cells that carry this
information are neurons
Spinal Nerves:
•There are 31 pairs
•Emerge from the spinal cord
•Some are motor nerves & some are sensory nerves
Cranial Nerves:
• There are 12 pairs
• Emerge from the brain stem of the brain
•EX: optic nerve pair (carry visual information from
retina to the brain)
COMPARE THE ORGANIZATION OF NERVOUS SYSTEMS
Nerve net + nerves
With cephalization came more complex
nervous systems like the CNS
What the heck do they do differently?
• Sensory neurons: transmit information from
external stimuli and internal conditions.
– Send the info to the CNS.
• Interneurons: analyze & interpret sensory
input
• Motor neurons: motor output leaves through
these & communicate with effector cells.
• Effector cells: muscle cells or endocrine cells.
Typical Pathway of Nervous System
Explain in as much
detail as possible the
pathway if you should
touch something hot.
As soon as you touched the pot of boiling water a sensory
receptor began an action potential or “nerve impulse”.
Each receptor in your body is designed to transform a particular kind of stimulus into
an action potential
There are a chain of neurons which take the impulse towards the CNS. In this case the
spinal cord.
Once at the spinal cord the action potential is routed to the appropriate area of the
CNS for interpretation.
During its stay in the CNS the action potential is carried by interneurons.
Your brain has now made the decision to remove your hand.
Relay neurons send the action potential to the spinal cord & out one of the spinal
nerve pairs (motor neuron).
The motor neuron is taking the impulse/action potential to the muscle and a chemical
signal is sent to the muscle (effector cells) which results in a contraction, moving your
hand.
The name for the muscle (in
this case) is the effector.
Junction where a
neuron sends a
chemical to muscle
tissue is called:
motor end plate
The Mad Mad Neuron
Nervous system pathway is a one way road from
dendrite to synaptic terminals.
Functions
• Dendrites: receive signals
• Axon: transmits signals
• Synapse terminals: location where
neurotransmitters are released
• Neurotransmitters: chemical messengers that
travel out of the presynaptic neuron and into
the postsynaptic neuron.
– Ex: acetylcholine, epinephrine, norepinephrine,
dopamine, serotonin, and GABA
Neurons of Vertebrates & Most
Invertebrates
• Have cells that are helper cells to the neurons
called: Glial or glia cells
– Nourish neurons, insulate the axons, & regulate
the extracellular fluid around the neurons.
– Outnumber the neurons in the mammalian brain
10-50 fold.
– During a synapse some neurotransmitters are sent
to the glial cells to be metabolized for fuel
Types of Glia Cells
Astrocytes: facilitate info. Transfer at synapses & sometimes release neurotransmitters.
cause nearby blood vessels to dilate enabling neurons to receive oxygen &
glucose faster. They also regulate extracellular concentrations of ions &
neurotransmitters.
Schwann cells & oligodendrocytes: cover axons with a myelin sheath which provide
electrical insulation.
Microglia: protect against pathogens.
FUNCTIONS OF THE BRAIN
How do neurons communicate with each other?
This occurs through a chemical communication called a synapse.
-examples of chemicals: acetylcholine, epinephrine, dopamine,
norepinephrine, serotonin, and GABA
Different communication synapse
pattern may occur…
7.5
The neurotransmitters
binding to the receptor
protein initiates to ion
channel opening and Na+
diffusing in which starts
the action potential down
the postsynaptic neuron
9.5
The neurotransmitter is
broken down by enzymes
& is released from the
receptor protein. They will
diffuse back across the
synaptic gap.
9.75
Sodium channel closes
Usually a ligand-gated channel
Generations of Postsynaptic Potentials
• Neurotransmitters which generate action potentials
are known as Excitatory Neurotransmitters.
– Cause Na+ to diffuse into the postsynaptic neuron
– EX: acetocholine
• Neurotransmitters which prohibit action potentials are
known as Inhibitory Neurotransmitters.
– Causes hyperpolarization of a neuron by allowing Cl- move
across postsynaptic cell into the membrane or cause K+ to
move out of the postsynaptic cell
– EX: GABA
Acetylcholine
• Common neurotransmitter to vertebrates &
invertebrates.
• Helps with muscle stimulation, memory formation,
learning, heart rate, energy level.
• Released by motor neurons
• Controls your brain speed by determining the rate at
which electrical signals are processed throughout your
body
– Alzheimer’s disease is associated with an imbalance
• If it remained in the synapse, the postsynaptic neuron
would keep “firing” indefinitely.
– Acetylcholinesterase breaks down the acetylcholine in the
synapse.
GABA- Inhibitory neurotransmitter
•
•
•
•
•
•
Brain’s natural valium
Linked with relaxation, anti-anxiety
Provides calmness to your body
Involved in the production of endorphins
Controls muscle movement
Used to help with symptoms of Huntington’s
Disease
Dopamine- inhibitory
• Monitors our metabolism
– Works like a natural amphetamine
– Controls our energy
– Promotes feelings of enjoyment
Serotonin
•
•
•
•
•
•
•
Associated with anger regulation
Body temperature
Mood
Sleep
Pain control
Appetitie
Provides a satisfied feeling in the body
Decision making
• A neuron is on the receiving end of many
excitatory and inhibitory stimuli.
• The neuron sums up the signals
– If the sum is excitatory the axons will “fire”
– If the sum is inhibitory the axons will not
• The summation of the messages is the way
decisions are made by the central nervous
system.
Controlling the Signaling System
• Some synapses have neurotransmitters bind to
metabotrophic receptors instead of ion channels
– Activates a signal transduction pathway in the
postsynaptic neuron involving a 2nd messenger.
• Have a slower onset but last longer
• Modulate the responsiveness of postsynaptic neurons in
diverse ways.
– EX: altering the number of open channels
Just to mess with you a little…
• Neurosecretory cells (aka neurohormones)– Nerve cells that release hormones
• A few chemicals serve as both hormones and
chemical signals.
– EX: epinephrine/adrenaline & norepinephrine
• “fight or flight” hormone produced in adrenal gland
• Serves as a neurotransmitter
Difference between neurotransmitters
& endocrine signals
• Neurotransmitters: usually small, nitrogencontaining compounds that are conveyed from
one specialized nerve cell to another along
specific nerve highways throughout the body
& are designed to elicit immediate responses.
• Endocrine signals: usually hormone secreted
from glands that use blood vessels to disperse
their signal molecules, to elicit a slower
response.
THE MOUSE PARTY
The Nervous System & The
Endocrine System
Work cooperatively in order to
ensure homeostasis.
That’s it … for now 
What is a nerve impulse?
• Nerve impulse is misleading. We will call it an
action potential instead
• Can be measured in the same way as electricity is
measured
– Voltage
• Millivolts
• The conductor of a neuron is the axon
– Is covered by a myelin sheath
• Increases the rate at which an action potential passes down
an axon.
• Membrane potential: the electrical potential
difference across the plasma membrane.
Resting potential
• Area of a neuron that is ready to send an action
potential but is not currently sending one.
• This area is considered polarized
– Characterized by the active transport of sodium ions
(Na+ ) out of the axon cell & potassium ions (K+) into
the cytoplasm.
– There are negatively charged ions permanently
located in the cytoplasm
– This collection of charged ions leads to a net positive
charge outside the axon membrane & negative charge
inside.
Neuron at Resting Potential
Resting potential results from the
diffusion of K+ and Na+ through channels
that are always open (ungated)
There are also gated ion channels
• Stretch-gated ion
channels: in cells that
sense stretch
• Voltage-gated ion channels:
located in axons &
open/close when
membrane potential
changes.
• Ligand-gated ion
channels: located at
synapses & open/close for
a specific chemical.
Action Potential
• Described as a self-propagating wave of ion movements in and
out of the neuron membrane
• This is the diffusion of the Na+ & the K+ .
– Sodium channels open & then potassium ones do to.
• This is the “impulse” or action potential
• It is a nearly instantaneous event occurring in one area of the
axon = depolarization
– This area initiates the next area on the axon to open up the channels.
• This action continues down the axon.
• Once an impulse is started at the dendrite end that action
potential will self-propagate itself to the far axon end of the
cell.
Depolarization opens the activation gates on
most Na+ channels, while the K+ channels
activation gates remain closed. Na+ influx makes
the inside of the membrane positive with respect
to the outside.
The inactivation gates on most Na+
channels close, blocking Na+ influx. The
activation gates on most K+ channels
open, permitting K+ efflux which again
makes the inside of the cell negative.
A stimulus opens the activation gates on some Na+
channels. Na+ influx through those channels
depolarizes the membrane. If the depolarization
reaches the threshold, it triggers an action potential.
The activation gates on the Na+ and K+ channels are closed, & the
membrane’s resting potential is maintained.
Both gates of the Na+ channels are closed, but the
activation gates on some K+ channels are still open. As
these gates close on most K+ channels, & the
inactivation gates open on Na+ channels, the
membrane returns to its resting state.
Return to Resting Potential
• Remember that one neuron may send dozens of
action potentials in a very short period of time.
• Once an area of the axon sends an action
potential it cannot send another until the Na+ &
K+ have been restored to their positions at the
resting potential.
• Active transport is required to move the ions =
repolarization
– The time it takes for a neuron to send an action
potential & then repolarize is called: the refractory
period of that neuron.
Inside of
membrane
becomes less -
Inside of
membrane
becomes more -
What makes it go faster:
• Different sized axons
– Bigger = faster
Saltatory conduction: By jumping
from one node to the next, this increases the
conduction velocity, allowing the signal to
travel faster