Topic 6 & 11 – Human Health
and Physiology
6.5 & 6.6 Neurons, Synapses, Hormones, and
Homeostasis
• What do you know?
• What questions do you have?
• How do neurons transport information?
Read & Consider 6.5.1, 6.5.3
1 – NERVOUS SYSTEM
BASICS
Nervous System Overview
Central Nervous System (CNS) – made up
of the brain and spinal cord.
 Peripheral Nervous System (PNS) –
connects CNS to limbs and organs. Made
up of:

◦ Sensory System – part of the system
responsible for processing sensory information.
PNS continued…

Effector (motor) system:
◦ Autonomic nervous system – involuntary
response.
◦ Somatic nervous system – voluntary response

Neuron – the cell that transmits nerve
impulses.
Neuron Structure
Nucleus
Node of
Ranvier
Motor end
plate
Electrical Impulses

Impulses are short-lived changes in
electrical potential across the membrane
of a neuron.
◦ Neurons generate these changes by pumping
charged chemical ions (Na+ & K+) back and
forth.
Membrane Review
Define: lipid bilayer, protein channel, protein
pump, and diffusion. Recall that large /
charged molecules cannot move freely
through the lipid bilayer.
Resting Potential
• What do you know?
• What questions do you have?
• Define resting potential.
Read & Consider 6.5.2, 6.5.4-6.5.6, 6.5.9
2 – NERVE IMPULSE
The Complete Process
Resting
Potential
Repolarization
Depolarization
Action Potential

For each nerve signal, mineral ions move
in and out of the cell to achieve each
state in the cycle above.
Action Potential

Depolarization

Repolarization
Nerve Impulse 
Action potentials propagated along the
axons of neurons.
◦ Local currents cause each successive part of
the axon to reach threshold potential.
Impulse

The impulse travels at about 0.5m / ms.
◦ The greater the axon diameter the greater
the speed.
◦ Myelinated neurons conduct impulses faster
than non-myelinated.
Myelination
Saltatory
conduction - the
propagation of action
potentials along
myelinated axons
increasing conduction
velocity.
WATCH:
Neuron Resting Potential
2. Action potential and synaptic transmission
1.
Oscilloscope Traces
Integrating Signals
• What do you know?
• What questions do you have?
Read & Consider 6.5.7-6.5.8
3 – INTER-NERVE
COMMUNICATION

Synapse- is the point where the axon of
one neuron joins the dendrite or cell
body of another.
Presynaptic neuron –
bringing the impulse.
Postsynaptic neuron –
picking up the impulse.
Neurotransmitter 
Chemicals that carry the impulse from one
neuron to the next since the action potential
cannot cross the synaptic cleft.
Animations:
1
2
3
Neonicotinoid Pesticides
Pesticides that bind to
acetylcholine receptors
in the central nervous
system of insects leading
to paralysis and death.
Read: “Neonicotinoid
Pesticide Reduces Bumble
Bee Colony Growth and
Queen Production”
• What do you know?
• What questions do you have?
• How do you alter your internal state?
Read & Consider 6.6.1-6.6.4
4 – HORMONES &
HOMEOSTASIS
The Endocrine System
The endocrine system is composed of glands that secrete
hormones directly into the blood to be carried throughout
the body.
Insulin & Glucagon
Pancreatic cells
monitor blood glucose.
 Pancreatic islets are
irregular structures
throughout the
pancreas and comprise
its endocrine function.

◦ They contain α and β
cells.
Regulation -
Diabetes

Type I diabetes (early or juvenile
onset):
◦ Auto-immune disease in which the beta-cells
pancreatic are destroyed.
◦ Unable to produce insulin.
◦ Responds well to regular injection of insulin
probably manufactured as the genetically
engineered humulin.

Type II diabetes (Adult onset):
◦ Reduced sensitivity of the liver cells to insulin.
◦ Reduced number of receptors on the liver cell
membrane.
Thyroxin

Secreted by the thyroid gland to regulate
the metabolic rate and control body
temperature.
Leptin

Secreted by cells in adipose tissue to
reduce appetite.
“It's been called the "obesity hormone" or "fat hormone"
-- but also the "starvation hormone." When scientists
discovered leptin in 1994, excitement arose about its
potential as a blockbuster weight loss treatment. Even
today, the Internet is loaded with sites that sell leptin
supplements. Any truth to those pitches? And what exactly
is leptin?”
Kam, Katherine. "Leptin Hormone & Supplements: Do They Work for Obesity & Weight Loss?" WebMD.
WebMD, Apr. 2010. Web. 01 Dec. 2014.
Melatonin

Secreted by the pineal gland to control
circadian rhythms.
 Circadian rhythms are physical, mental and
behavioral changes that follow a roughly 24-hour
cycle, responding primarily to light and darkness in
an organism's environment. They are found in
most living things, including animals, plants and
many tiny microbes.
How does gender affect reaction
time?
How does height affect reaction
time?
1. Collect gender, height, and
reaction (best of 3) data.
2. Compile data into class
tables.
3. Complete analysis phase for
each research question.
Works Cited
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"AP Bio - Nervous System and Muscles." Quia -. N.p., n.d.Web. 03 Nov. 2014.
Calcattera, Craig. "Inside the Batter's Brain." Hardball Talk. NBC Sports, 9 May 2013. Web. 3 Nov. 2014.
"CH 11 Physics Underlying Impulse Transmission." CH 11 Physics Underlying Impulse Transmission. N.p.,
n.d.Web. 03 Nov. 2014.
"Chapter 2: Patterns in Nature." Chapter 2: Patterns in Nature. N.p., n.d.Web. 03 Nov. 2014.
Charand, Ka Xiong. "Nerve Cell." Nerve Cell. HyperPhysics, n.d.Web. 23 Nov. 2014.
Elliot, Anne. "Thyroid and Infertility." Annes Health Place. N.p., 25 Oct. 2010. Web. 01 Dec. 2014.
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Nov. 2014.
"Excitable Cells." Excitable Cells. N.p., 28 Apr. 2014. Web. 25 Nov. 2014.
Kam, Katherine. "Leptin Hormone & Supplements: Do They Work for Obesity & Weight Loss?" WebMD.
WebMD, Apr. 2010. Web. 01 Dec. 2014.
"KEEP CALM AND Maintain Homeostasis." - KEEP CALM AND CARRY ON Image Generator. Keep Calm
Network Ltd., n.d.Web. 28 Nov. 2014.
Monbiot, George. "DDT 2.0." PermacultureNews.org. N.p., 14 Aug. 2013. Web. 27 Nov. 2014.
"National Diabetes Information Clearinghouse (NDI)." Pancreatic Islet Transplantation. N.p., n.d.Web. 28
Nov. 2014.
"Nervous System Information." Nervous System Information. Adam Inc., 2001. Web. 24 Nov. 2014.
Shumpc. "Multipolar Neuron Stock Photo 153362348." Thinkstock. N.p., n.d.Web. 28 Oct. 2014.