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Unit 8: Physiology
Control Systems of the Body: The
Nervous & Endocrine Systems
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Unit 8: Physiology
Left Side
Pg
Right Side
Pg
Unit Page
48
Table of Contents
49
Neuron/Synapse
50
C.N. – Control Systems
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Homeostasis
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Section 35-2
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Flow Map: I Blood Glucose
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Flow Map: Leptin & Humger
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Nervous System
Overview
 Ultimate
systems.
control of all organ
 Responsible
for
communication between
parts of the body and
interactions with the
environment
 STRUCTURES: brain, spinal
cord, & peripheral nerves
+ Neurons
 Neurons:
nerve cells that
carry electrical impulses
through the body
 Impulse
= message
+ TYPES OF NEURONS
1. SENSORY
NEURONreceives info
from senses
(stimuli)
2. INTERNEURONprocesses info
(in brain & spinal
cord)
3. MOTOR
NEURON- sends
impulse to
effector (muscle
or gland)
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Reflex Arc
 The
impulse travels up sensory neurons, to
the spinal cord (interneuron), then
immediately travels down motor neurons
for a response.
 The pathway the impulse travels is called
the reflex arc
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Reflex Arc
• Receptor (sense organ)  sensory neuron 
spinal cord  motor neuron  effector (muscle)
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Reflex Arc
Sensory Neuron
Interneuron
Motor Neuron
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Structure
of a Neuron
Nucleus
Dendrites
Axon
terminals
Cell body
Myelin sheath
Nodes
Axon
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 Dendrites: receive impulses
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 Cell body: contains nucleus & cytoplasm
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 Myelin Sheath: covers the axon; sends the
impulse faster
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 Axon: transmit impulses away from cell
body
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 Nodes: gaps where impulses jump from
one node to the next
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 Axon terminals: transmits impulse
(message) to next cell
+ Action Potential

An impulse begins when a neuron is stimulated
by another neuron or by the environment.
 Gates
in the sodium channels open allowing
positively charged sodium (Na+) ions to flow
into the cell.
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
This reversal of charges is called the nerve impulse
or ACTION POTENTIAL
 Gates
in the potassium channels open, allowing
potassium (K+) ions to flow OUT of the cell. This
restores the negative potential
+ The action potential continues to move along
the axon in one direction toward the axon
terminals.
1.
At Rest
------------2.
Action Potential
++---------3.
----++----4.
---------++-
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
Synapse
Synapse: at the end of the
axon terminal where a neuron
can transfer an impulse to
another neuron.
 The
small space between the
two neurons is called the
Synaptic Cleft
 Neurotransmitters: chemical
signals that transmit an
impulse across the synapse to
another cell
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Homeostasis
 Homeostasis:
The relative maintenance of
the body’s internal environment
 All
systems of the body contribute toward
maintaining homeostasis
 The
Endocrine System (hormones) works in
conjunction with the Nervous System to
maintain homeostasis
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Endocrine System Overview
 Maintenance
of internal homeostasis ( the
internal environment in the body)
 Regulation
organism.
 Made
of growth and development of an
up of GLANDS that release hormones
into the bloodstream
 Hormones: chemical "messengers" that
control body functions
+ Major Glands of the
Endocrine System
+ Pituitary Gland
 Communicates
with the hypothalamus to
control many body activities (Master Gland)
 Produces
& secretes NINE hormones that
affects other glands and organs
Hormones of the Pituitary
 Human
Growth
Hormone (HGH)controls growth and
height
 Follicle
stimulating
Hormone (FSH) /
Luteinizing Hormone
(LH) – control gonads
(development of
sperm and
eggs/release of sperm
and eggs)
 Thyroid
Stimulating
Hormone (TSH)controls the thyroid
(metabolism)
 Adrenocorticotropic
Hormone (ACTH)stimulates growth of
the adrenal gland
(stress hormones)
Pancreas
 The
pancreas
produces insulin and
glucagon needed for
cells to absorb sugar
from the blood
 Insulin
– metabolizes
sugar
 Glucagon
– maintains
blood level of glucose
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 One
Negative Feedback Loop
hormone causes the opposite effect of
another hormone.
 Both are used to maintain homeostasis
 Examples:
 Insulin & Glucagon
 Leptin
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Negative Feedback Loop
Involving the Pancreas
 STEP
1: The pancreas releases insulin when
there is too much sugar in the blood.
 STEP
2: Insulin stimulates the liver to remove
sugar from the blood and store it as
glycogen.
 STEP
3: When there is not enough sugar in
the blood, the pancreas releases glucagon.
 STEP
4: Glucagon signals the liver to release
glucose back into the blood
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Negative Feedback Loop
Involving Leptin
 STEP
1: Fat cells produce leptin when they
are filled.
 STEP
2: Leptin is transported in the blood
to the brain where it helps to suppress a
person appetite.
 STEP
3: When the fat is used, the amount of
leptin decreases, which causes the brain to
start to feel hunger again
Individuals without
the gene to produce
Leptin