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Chapter 12, 13
Nervous Tissue, Spinal Cord
Divisions of NS
1. CNS-central nervous system
A. Brain
B. Spinal Cord
2. PNS-peripheral nervous systemprimarily nerves of body
A. Spinal nerves- 31 pairs
B. Cranial nerves- 12 pairs
Divisions of PNS
a. Somatic- controls skeletal muscle, skin
b. Autonomic-controls smooth, cardiac
muscle
1. Sympathetic- fight/flight,
emergencies
2. Parasympathetic-relaxation,
“vegetative” reflexes
3 Basic Functions
1. Sensory (afferent)
Receptors send impulses to CNS
2. Motor (efferent)
CNS sends impulses to effectors (muscles
or glands)
3. Integrated Functions- intelligence,
creativity, personality, etc.
Organelles in a neuron
1.
2.
3.
4.
5.
Nucleus
Granular ER(Nissl bodies)
Mitochondria
Neurofibrils(microtubules)
No centrioles
-
Classification of Neurons
• P365
1. Anaxonic- located in brain, special sense
organs
2. Bipolar-special sense organs
3. Unipolar-sensory neurons of PNS
4. Multipolar- most common
Neuroglia
2. Neuroglia in PNS
A. Satellite Cells- similar to astrocytes
B. Schwann Cells- similar to
oligodenedrocytes, produce myelin
sheath in PNS
Neuroglia
1.Neuroglia in CNS
A. Astrocyte- function in creating bloodbrain barrier, provide structure
B. Oligodendocyte- produce myelin
sheath
C. Microglia- immune cells of CNS,
similar to macrophages
D. Ependymal- found in ventricles of
brain, produce cerebrospinal fluid
Synapse
• A specialized site where neurons
communicate with one another
• http://faculty.washington.edu/chudler/syna
pse.html
Myelin
• Acts like electrical insulation
• Nodes of ranvier-gaps between schwann
cells on axon; allows nerve impulse to
jump between nodes; leads to high
conduction speeds= 100m/s
• LocationsA. All motor neurons
B. All spinal nerves
C. 99% of brain
Unmyelinated
• Slow conductions speed, .5 m/s
• Located
A. In autonomic nervous system
Spinal Cord- Chapter 13
• Length= 18”, width=.5”
• Extends from
base(foramen magnum)
of skull to 2nd lumbar
vertebra
• “carrot shaped”
• Ends @ conus
medullaris- many nerves
exit and form cauda
equina
• 2 enlargements=cervical
and lumbar- where more
nerves enter and leave
the cord
# of spinal nerves-31
•
•
•
•
Cervical- 8
Thoracic-12
Lumbar-6
Sacral-5
Organization
1. White matter- myelinated sections on
outermost parts
•
can be ascending- going to brain
-carry sensory info
-called afferent
• Can be descending- coming from brain
- carry motor info
- called efferent
• Root- where nerve enters or exits cord
dorsal root=sensory/afferent
ventral root= motor/efferent
** In back door out front door**
Organization
1. Gray matter- unmyelinated sections
forming H pattern in the interior
•
posterior horns- contain afferent
neurons
•
anterior horns- contain efferent
neurons
• “cross bar”=commissure
Plexuses
•
1.
2.
3.
4.
Plexus- interwoven network of nerves
Cervical plexus
Brachial plexus
Lumbar plexus
Sacral plexus
Reflexes
•
•
1.
2.
3.
4.
5.
Rapid automatic response to a specific
stimuli
Work through a reflex arc- a simple neural
pathway
reception
transmission via sensory neuron
integration
transmission via motor neuron
response
Classifying Reflexes p 424
1. By response
A. Somatic reflex- involves skin, skeletal
muscle, function in protection
B. Visceral reflex- involves cardiac, smooth
muscle, glands, bl.v, function in
homeostasis
2. By development
A. Innate- w/drwal fr. pain, suckling,
tracking objects w/ eye
B. Acquired- driving, sports
3. By processing site
A. Spinal- patellar reflex
B. Cranial- sudden noise, bright light,
respiration
4.Complexity of circuit
A. MonosynapticB. Polysynaptic