The Nervous System - School District of New Berlin

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The Nervous System
Chapters 11-14
Unit Objectives
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List the organs and divisions of the nervous system & describe the generalized
functions of the system as a whole.
Identify the major types of cells in the nervous system and discuss the function
of each.
Identify the anatomical and functional components of a signal. Compare and
contrast the propagation of a nerve impulse along a nerve fiber and across a
synaptic cleft.
Identify the major anatomical components of the brain and spinal cord and
briefly comment on the function of each.
Compare and contrast spinal and cranial nerves.
Discuss the functional characteristics of the two divisions of the autonomic
nervous system
Organs & Divisions of Nervous
System
• Central Nervous System (CNS): Brain &
Spinal Cord
• Peripheral Nervous System (PNS): Nerves
extend to outlying or peripheral parts of the
body
– Autonomic Nervous System (ANS):
subdivision of PNS regulates automatic or
involuntary functions
1. Brainstem
Spinal cord
Brainstem
Medulla Oblongata
Function:
-movement
-posture
-rate of heart contractions
-breathing rate
-non-vital reflexes
Pons
-relays sensory information
-regulates breathing
Midbrain
-skeletal reflex center
2. Diencephalon
Spinal cord
Diencephalon
Thalamus
-interprets all senses except smell
-synapses for voluntary movement
Hypothalamus
-controls the autonomic nervous system
-coordinates the nervous and endocrine system
-controls reactions to threats
-controls sleep cycles
-involved in sexual responses
-controls body temperature
3. Cerebrummakes up about 7/8 of your entire brain
Divided into 4 lobes
Cerebrum
The surface of the
cerebrum is highly
folded.
Ridges = gyri
Grooves = sulci
Deep grooves= fissures
They create more surface
area.
Why does the cerebrum
need more surface
area?
4. Cerebellum (little brain)
Cerebellum
-quality control center for movement
It fine-tunes the movements called for by
the cerebrum. It compares the actual
movement with the intended movement
and makes corrections, as necessary.
Cranial Nerves
SPINAL
NERVES
The Peripheral Nervous System
• Consists of the nerves that lead into or
outward from the brain and spinal cord
-12 cranial nerves
-31 pairs of spinal nerves
Cells of the Nervous System
• Neurons
• 3 Main Parts
– Dendrites: conducts impulses to cell body
– Cell body
– Axon: conducts impulses away from the cell
body
Cells of the Nervous System
• Neurons are classified according to function
– Sensory: conduct impulses to the spinal cord &
brain
– Motor: conduct impulses away from brain &
spinal cord to muscles & glands
– Interneurons: conduct impulses from sensory
neurons to motor neurons
Neuron
Axon terminals
Dendrite
1
2
Cell body
Node of
Ranvier
4
3
5
Schwann’s Cells
7
6
8
Nucleus
Axon Hillock Myelin Sheath
Cells of the Nervous System
• Glia: Connective tissue cells of the CNS
• 3 Main types
– Astrocytes: star-shaped cells that anchor small
blood vessels to neurons
– Microglia: small cells that move in inflamed
brain tissue carrying on phagocytosis
– Oligodendrocytes: form myelin sheaths on
axons in the CNS
Cells of Nervous System
– Satellite cells- surround and control the
chemical environment of the neuron
– Schwann cells- insulate the neuron, form the
myelin sheath
Nerve Impulses
• Nerve impulses have a domino effect
• Through a chain of chemical events, the
dendrites pick up an impulse that’s shuttled
through the axon and transmitted to the next
neuron.
• The entire impulse passes through a neuron in
about 7 milliseconds- faster than a lightning
strike.
Step 1
Resting Potential
(the nerve fiber is not sending a signal)
• NaK pumps in the cell
membrane actively transport
3 Na+ ions out of the cell for
every 2 K+ ions pumped into
the cell
• The result- the interior of the
cell is negatively charged
with respect to the exteriorpolarization
Step 2
Depolarization
• A threshold stimulus is received. A threshold
stimulus is the stimulation level that must be
exceeded to elicit a nerve impulse or a muscle
contraction
• Sodium Channels in a local region of the
membrane open and sodium diffuses inward
depolarizing the membrane
• What charge are sodium ions?
• +
• What will happen to the charge inside of the
neuron?
• It will become more +
Step 3
Repolarization
• Potassium channels in
the membrane open
• Potassium ions diffuse
outward, repolarizing
the membrane
Step 4
Action Potential
• The resulting action
potential causes a local
bioelectric current that
stimulates adjacent portions
of the membrane
• The wave of action potential
travels the length of the
nerve fiber as a nerve
impulse
Summary of Nerve Impulse
•Nerve impulse summary animation
The Synapse
• A gap called a synapse or synaptic cleft
separates the axon of one neuron and the
dendrites of the next neuron.
• *Neurons do not touch.
• Chemicals carry
messages across
the synapse.
1
2
5
4
3
7
6
8
1
2
7
3
4
5
6
The synapse animation
Neurotransmitters
• Excitatory neurotransmitters- lead to changes that generate
an action potential in the postsynaptic neuron
• Inhibitory neurotransmitters- tend to block the changes that
cause an action potential to be generated in a postsynaptic
neuron.
• Note- If a postsynaptic cell receive both excitatory and
inhibitory messages the response of the postsynaptic
depends on which message is stronger
Excitatory neurotransmitters
1. Acetylcholine- muscle contractions,
memory
2. Serotonin- sleep patterns, sensory
perception, mood, temperature regulation,
cerebral blood flow
3. Catecholamines (epinephrine,
norepinephrine)- mood, temperature
regulation, dreaming
Inhibitory Neurotransmitters
1. GABA- calms the brain
2. Dopamine- emotions, subconscious
movement of skeletal muscle, separation
of real from imagined
3. Endorphins- pain relieving, apatite
modulation, associated with runner’s high
Effect of drugs on neurotransmission
When neurons do not communicate normally, the brain does
not function normally either.
• Alcohol animation
Why is drinking alcohol dangerous?
• Cocaine animation
What feeling does dopamine give a person?
How does cocaine affect the transmission of dopamine?
Why is cocaine addicting?
Autonomic Nervous System
• Motor Neurons that conduct impulses from
the central nervous system to cardiac
muscle, smooth muscle, and glandular
epithelial tissue
• Regulates the body’s automatic functions to
maintain or quickly restore homeostasis
Autonomic Nervous System
• Composed of two divisions
– Sympathetic Nervous System
– Parasympathetic Nervous System
Sympathetic Nervous System
• Serves as the emergency or stress system,
controlling visceral effectors during
strenuous exercise & strong emotions
(anger, fear, hate, or anxiety)
• Group of changes induced by sympathetic
control is called fight-or-flight response
Parasympathetic Nervous System
• Dominates control of many visceral
effectors under normal, everyday
conditions.

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