Download Chapter 8 Nervous System

Chapter 8
Nervous System
5 Functions
1. Sensory function =
receptors monitor external &
internal body changes;
providing input
Functions continued:
2.Integration function =
brain & spinal cord process
sensory information from
receptors & initiate a proper
response
Functions continued:
3. Motor function = output
response from brain & spinal
cord by way of nerve
impulses to effectors
(muscles, glands, etc)
Functions continued
4. Homeostasis-Depends on the
ability of the NS to detect,
interpret, and respond to change in
internal and external conditions.
In response, the NS can stimulate
or inhibit the activities of other
systems to maintain homeostasis.
Functions continued
5. Mental Activity-The brain is
the center of mental activity,
including consciousness,
memory, and thinking.
Organization
Organization
Organization
- 2 Major Division
1. CNS (central nervous
system) = brain , spinal
cord, nuclei
Organization
- 2 Major Division
2. PNS (peripheral nervous
system) = nerves (cranial
& spinal nerves) & ganglia
Organization:
Divisions of PNS
• PNS (peripheral nervous
system) is further divided into
2 divisions:
1. Sensory division = nerves
which send impulses to
CNS from receptors
Organization:
Divisions of PNS
• PNS
2. Motor Division = nerves
which carry impulses away
from CNS to effectors
(muscles, glands)
Organization:
Divisions of PNS
• PNS Motor Division is further
divided into
1. Somatic Nervous System =
(SNS) nerves that carry
impulses away from CNS to
voluntary effectors (skeletal
muscles)
Organization:
Divisions of PNS
• PNS Motor Division is further
divided into
2. Autonomic Nervous System
(ANS) = nerves which carry
impulses away from CNS to
involuntary effectors (glands,
heart, smooth muscle)
Organization:
Divisions of PNS
- PNS Motor Division,
Autonomic Nervous System
(ANS) is further divided into
1. Parasympathetic Division =
carries impulses away from
CNS to involuntary effectors
under normal conditions
Organization:
Divisions of PNS
2. Sympathetic Division =
carries impulses away from
CNS to involuntary effectors
under stressful conditions
- Sometimes called “fight or
flight”
Nervous System
CNS
PNS
Sensory
Somatic
Parasympathetic
Motor
Autonomic
Sympathetic
Autonomic Nervous System
• Can be divided into:
– Sympathetic
Nervous
System
• “Fight or Flight”
– Parasympathetic
Nervous System
• “Rest and
Digest”
These 2 systems are antagonistic.
Typically, the 2 divisions are balanced
to keep the body in a state of
dynamic balance.
ANS:
-Sympathetic & Parasympathetic
tend to produce opposite results
on their effectors
Sympathetic
heart
rate
Parasympathetic

heart rate
resp. rate

resp. rate


sweating
None
Sympathetic
Parasympathetic
Pupil dilation
Pupil constriction

Digestion
blood vessel
dilation in skeletal
muscles

Digestion
None
Sympathetic
Parasympathetic
Blood vessel
constriction in skin
& viscera
Adrenal
hormones
None
(adrenalin or epinephrine)
None
Nervous Tissue (primary cells)
Primary cells: Neurons/Neuroglia
1. Neurons = produce & conduct
nerve impulses (electrical
events):
- Major cells parts
a. cell body = contains main
organelles (nissl bodies =
rough E.R.)
Major cells parts
b. 2 cell processes = cell
extensions from the cell body
- dendrites = carry impulse
to cell body, may be
branched
- axon – carries impulse away
from cell body
c. Axon terminal = swollen
ending of axons contain synaptic
vesicles with chemicals
(neurotransmitters)
Direction of Impulse:
dendrite
cell
body
axon
d. axon hillock = expanded
portion where the axon
joins the cell body
e. myelin sheath = whitish
insulation layer surrounding
axon, protects & increases
speed of nerve impulses
-actually formed by Schwann
cells (a neuroglial cell)
2 types neurons
- myelinated neurons
(white matter)
- unmyelinated neurons
(gray matter)
f. Neurilemmal sheath =
surrounds myelin sheath,
used in repair of axon
g. Nodes of Ranvier = small
areas on myleinated axon
where no myelin sheath is
formed.
Nuclei in the CNS
By definiton:
1. clusters of cell bodies in the
CNS (brain & spinal cord)
Types of Neurons
By Function :
(what they do?)
1. sensory neuron = carries
impulses to CNS
2. motor neuron = carries
impulses away from the
CNS to effectors
Types of Neurons
3. interneuron = neurons
between sensory & motor
neurons; located only in
CNS
Types of Neurons
By structure
(what they look like?)
1. multipolar neuron = one
axon & many highly
branched dendrites
2. bipolar = one axon & one
dendrite on opposite sides of
cell body
3. unipolar neuron = one axon
& one dendrite connected to
cell body by a small
T-like process (ie one process
extends from the cell body)
multipolar neurons = motor
neuron & interneurons
bipolar neurons = sensory
neurons, usually in eye
unipolar neurons = sensory
neurons in skin
Nervous Tissue (2 primary
cell types)
2. Neuroglia = 5 types of
supportive cells:
-Oligodendrocytes, Schwann
cells. Microglia, astrocytes,
ependymal
Types of Neuroglia
• Oligodendrocytes:
produce myelin sheath in CNS
• Microglia:
help remove bacteria and cell debris from CNS
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Types of Neuroglia
•
•
Astrocytes:
- star-shaped
- most abundant
- form blood-brain barrier
Ependymal Cells:
produce and circulate cerebrospinal fluid (CSF)
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Types of Neuroglia
• Schwann cells:
produce myelin
sheath around
around axons in
PNS
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Saltatory conduction in a
myelinated axon
Synapse
• What is it?
- where an axon comes in close
contact to a muscle, gland,
organ, or other neuron
- involved with release of
neurotransmitters
- Ex. Neuromuscular junction
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Figure 8.13
Neuronal Pathways
Converging:
- two or more neurons synapse on same neuron
- allows info. to be transmitted in more than
one neuronal pathway to converge into a single
pathway
Diverging:
- axon from one neuron divides and synapses
with more than one neuron
- allows info. to be transmitted in one neuronal
pathway to diverge into 2 or more pathways
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