Download Nerves, Hormones, and Homeostasis

Topic 6.5
• 6.5.1-State that the nervous system consists of the central
nervous system (CNS) and peripheral nerves, and is composed
of cells called neurons that can carry rapid electrical impulses.
• 6.5.2-Draw and label the structure of a motor neuron.
• 6.5.3-State that nerve impulses are conducted from receptors to
the CNS by sensory neurons, within the CNS by relay neurons,
and from the CNS to effectors by motor neurons.
• 6.5.4-Define resting potential and action potential
(depolarization and repolarization)
• 6.5.5-Explain how a nerve impulse passes along a nonmyelinated neuron
• 6.5.6-Explain the principles of synaptic transmission.
• State that the nervous system consists of the central nervous
system (CNS) and peripheral nerves, and is composed of cells
called neurons that can carry rapid electrical impulses.
• Neurone=Neuron
• Central Nervous System (CNS)the brain and the spinal cord
• Peripheral Nervous System
(PNS)-outlying nerves conducting
impulses to and from the CNS
• Neuron-nerve cell; three types
(Soma)
• State that nerve impulses are conducted from receptors to the
CNS by sensory neurons, within the CNS by relay neurons, and
from the CNS to effectors by motor neurons.
• No difference in structure of the three types
• Resting Potential-the usual state of a nerve, when it is ready to
send an impulse
• Called potential because it refers to the electric potential of the
neuron membrane
• This resting state has Sodium ions (Na+) outside the membrane
and Potassium ions (K+) inside.
• The Resting Potential for a human neuron is about -70 millivolts
• This means the inside of the membrane is more negatively
charged than the outside
• Action Potential-the state of the nerve when its polarity has
been switched. The nerve has been depolarized.
• At the Action Potential, Na+ and K+ are both on the inside of
the neuron.
• The intervals during which the neuron is at the action potential
form the impulses that travel along the nerves
• In its resting state, a neuron is at resting potential.
• If a sensor is stimulated, this causes the nerve connected to it to
change.
• Chemically-controlled channel proteins in the main neuron body
open, letting Na+ ions in.
• This makes the membrane potential of the neuron increase.
• If the potential voltage increases to a “threshold level,” then
further changes take place.
• Once the voltage reaches the threshold, voltage-controlled
channel proteins open, allowing even more Na+ into the neuron
• This increases the charge of the inside of the neuron,
depolarizing it and bringing it to its action potential
• There are now Na+ and K+ ions in the neuron, so the inside is
relatively more positive than the outside
• This higher voltage causes more channel proteins to open, so the
action potential moves down the neuron
• At the Action Potential, the Na+ channel proteins close, so Na+
ions stop coming in to the neuron
• K+ channels open, and K+ starts to flow out of the neuron
• The neuron starts to be repolarized by this flow, and the
membrane potential voltage drops
• Once the voltage is low enough, the K+ channels close, and the
neuron is once again at resting potential
• Sodium-potassium pumps move the Na+ and K+ back to their
original locations: Na+ outside and K+ inside
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter14/animati
on__the_nerve_impulse.html
• If the voltage does not increase enough to trigger an action
potential, the Na+ ions are simply pumped back out, and the
neuron returns to resting potential
• To be felt, a stimulus must be great enough to trigger an
impulse
• Myelin is a fatty compound that surrounds the axon, except in
the Nodes of Ranvier
• There are no channel proteins where myelin sheaths surround
the axon
• Instead of the whole axon moving to action potential, only the
area around the node does so
• This greatly speeds and eases the process of moving an impulse
down the nerve
• When the opening of channel proteins reaches the end of the
axon, Ca2+ diffuses into the neuron
• Vesicles containing a neurotransmitter chemical already exist at
the axon tail, in swollen areas known as “terminal buttons”
• Calcium ions cause the vesicles to merge with the membrane of
the axon, releasing the chemical into the “synaptic cleft”,
between the button and another neuron
• The neurotransmitter bonds to a protein channel on the next
neuron, opening it and allowing Na+ ions in, continuing the
impulse
• The neurotransmitter is broken down by enzymes
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter14/animati
on__chemical_synapse__quiz_1_.html
• 6.5.1-State that the nervous system consists of the central
nervous system (CNS) and peripheral nerves, and is composed
of cells called neurons that can carry rapid electrical impulses.
• 6.5.2-Draw and label the structure of a motor neuron.
• 6.5.3-State that nerve impulses are conducted from receptors to
the CNS by sensory neurons, within the CNS by relay neurons,
and from the CNS to effectors by motor neurons.
• 6.5.4-Define resting potential and action potential
(depolarization and repolarization)
• 6.5.5-Explain how a nerve impulse passes along a nonmyelinated neuron
• 6.5.6-Explain the principles of synaptic transmission.
-Resting potential is the membrane potential of a
neuron membrane when not conducting an
impulse.
-Action potential is the state of the cell membrane
while conducting an impulse
A.Voltage-gated sodium ion channels open and Na+ is pumped
in.
B. Voltage-gated sodium ion channels open and Na+ diffuses out.
C.Voltage-gated potassium ion channels open and K+ is pumped
out.
D. Voltage-gated potassium ion channels open and K+ diffuses
out.
- Correct answer: D
A.Propagates an action potential by pumping sodium ions across
the membrane out of the neuron.
B. Propagates an action potential by pumping sodium ions across
the membrane into the neuron.
C.Initiates the action potential needed for the transmission of an
impulse by pumping calcium ions out of the endoplasmic
reticulum.
D. Establishes the resting potential needed for the transmission of
an impulse by pumping sodium and potassium ions across the
membrane.
-Correct answer: D
The Endocrine System (6.5.7)
Hormone are molecules secreted by certain glands that
have a direct affect on your body.
State that the endocrine system consists of glands that
release hormones that are transported in the blood.
Exocrine Glands

Exocrine Glands are glands that secret their
product and is lead into an external
environment (not hormone producing yet still
apart of the endocrine system).
ex) Salivary Glands, Sweat Glands, Stomach
Three Types of Hormones

Steroids

Peptides

Amines
Difference between the three is based on their structure.
When the hormone is releases it travels to target cell with correct
receptor for that hormone.
Steroids
These hormones are lipids derived from
cholesterol (hydrophobic)

Ex) Testosterone
Peptides
These are short chains of amino acids (most
hormones are these)

Ex) Amylin (secreted by beta cells in the
pancreas)
Amines
These are smaller structures with amine groups.

Ex) Histamine (controls immune responses to
allergies)
The Homeostasis Commandments
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Maintaining internal environment between limits
Importance of blood pH
Carbon dioxide concentration
Blood glucose concentration
Maintaining levels of variables, Body temperature
and water balance
• Negative feedback mechanisms
• Roles of heat in blood, hypothalamus, sweat
glands, skin arterioles and shivering
Break it Down Now
Normal Limits
•
•
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Blood pH: 7.35
Carbon dioxide concentration: 390ppm per V
Blood glucose concentration: 90mg/dl
Body temperature: 37oC
Water balance
Important Vocabulary
• Homeostasis: The process of maintaining the internal
conditions of an organism between acceptable limits.
• Hypothalamus: A part in the brain that controls many
automatic functions in the body, most important is the body’s
“internal thermostat”.
• Negative feedback mechanisms: are self-regulating responses
to changes experienced by a system or organism, usually due
to external influences.
• Normal limits: The forms the body takes when its regulated
such as temperature (37oC).
How your body warms itself
How your body cools itself
Controlling Blood Glucose Levels
(6.5.11)

This is a type of homeostasis

Controlled by the pancreas (pancreatic islet)

Constantly Being regulated (see-saw)
Hepatic Portal Vein

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Once blood has taken the nutrients (glucose)
from the digestive system, it travels through the
hepatic portal vein.
This takes all blood to the liver before anywhere
else in the body.
Liver cells called hepatocytes must act on the
blood first to control the level of glucose in your
blood.
The liver is the “Control Center” when deciding
if there is too much or too little glucose in your
blood.
Some Pictures...
Pancreas Beta (β) Cells (Blood
Glucose levels too high)

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These produce insulin (hormone) when liver decides
there is too much glucose in the blood.
Insulin allows protein channels in your cell membranes to
open and allow the glucose to enter your cells through
facilitated diffusion (in your muscle cells).
Insulin also makes the hepatocytes cells take in glucose
(monosaccharide) and turn it into glycogen (a polysaccharide)
to be stored in their cytoplasm.
Pancreas Alpha (α) Cells (Blood
Glucose levels too low)
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Produces hormone called glucagon.
This allows the body to break down the
glycogen in your liver and muscle cells back
into glucose.
This increases your blood glucose levels.
Diabetes (6.5.12)

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A disease characterized by hyperglycaemia
(high blood sugar).
Your body's β cells can't produce a sufficient
amount of insulin.
Type 1 Diabetes

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Insulin - Dependant disease
Autoimmune disease, the body's immune system attacks the β
cells and destroying them.

Most often developed in children, but can develop at any age.
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Must take insulin shots externally.
Type 2 Diabetes
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Non-Insulin-Dependant Disease, Where the body's cells no
longer respond to insulin (they were overused).
This is the most common type of Diabetes (90% of diabetics).
Linked to genetic history, obesity, lack of exercise, age, and
certain ethnic groups.
If you family has a past with Diabetes, you are more
susceptible to it.
Controlled by diet.
Serious Affects of Diabetes w/ some
Facts
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Kidney failure, nerve damage, increases of cardiovascular
disease, poor wound healing, damage to retinas leading to
blindness.
Ethnic groups affected by type 2 diabetes the most are African
Americans, Hispanic/Latino Americans, American Indians,
Asian Americans, and Pacific Islander Americans