BIOL 1410 Lecture Notes - Lecture 19: Central Nervous System, Multipolar Neuron, Unipolar Neuron
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TOPIC 19: NERVOUS SYSTEM
A) Nervous System: Overview
2 divisions:
1) Central Nervous System (CNS)
oad center or otrol eter
brain + spinal cord
processes + integrates info
2) Peripheral Nervous System (PNS) figure 13.7 & 13.29
consists of:
a) cranial nerves
to/from brain
b) spinal nerves
to/from spinal cord
2 divisions of PNS: figure 11.1
a) sensory/afferent division enters
has sensory receptors that detect stimuli (change in internal or
external environments)
b) motor/efferent division
nerves convey impulses away from CNS exits
innervates (supplies signals/nerves to) effectors = muscles +
glands (endocrine or exocrine)
relationship between CNS and PNS:
example:
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2
Nervous System Organization: figure 11.2
B) Nervous System: Histology
Cell Types:
1) Neurons
conduct impulses
make up CNS + PNS
mostly amitotic (irreplaceable) you cant make more of them
o exceptions = taste, olfaction, memory
structure:
a) cell body
typical organelles
RER called - Nissl Bodies
groups/clusters in CNS = nuclei (gray matter)
groups/clusters in PNS = ganglia
b) processes from cell body:
i. dendrites
receive incoming messages + relay to cell body
ii. axon
carry impulses away from cell body
axon hillock = where axon meets cell body
axon terminal = typically branched with synaptic end
bulbs (enlarged tips)
may be:
myelinated - – wrapped in many layers of cell
membrane from Schwann cells (PNS) or
oligodendrocytes (CNS)
electrical insulation
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3
gaps in myelin sheath are called Nodes of
Ranvier
myelinated axon bundles in:
o CNS = tracts (white matter)
o PNS = nerves
o BE ABLE TO ANSWER THESE
QUESTION FOR THE EXAMS
unmyelinated – no myelin
2) Neuroglia (glial cells)
Surround and support neuron cells = can undergo mitosis (prone to cancer –
brain tumor)
types:
a) CNS neuroglia
i. oligodendrocytes
produce myelin around axon
ii. microglia
protective – become phagocytic if detect infected, dead,
or damaged neurons (because iue ells at eter
CNS)
iii. astrocytes
surround blood capillaries to form part of blood brain
barrier (BBB)
help control capillary permeability
iv. ependymal – neural epithelia
line brain ventricles + central canal of the spinal cord
secrete cerebrospinal fluid (CSF) + circulate it (cilia)
b) PNS neuroglia
i. Schwann cells
form myelin around axons in PNS
ii. Satellite cells
surround neuron cell bodies in ganglia – protection +
support
Neuron Classification:
1) Structural/Anatomical types:
based on # of cell processes off of cell body
a) Unipolar
1 process that divides into two: central + peripheral
peripheral end has dendrites = sensory receptors (pain, touch
etc) - remainder is axon
always sensory
b) Bipolar
2 processes: 1 axon, 1 process with dendrites
sensory – retina, nose (olfaction)
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Document Summary
Topic 19: nervous system: nervous system: overview. 2 divisions: central nervous system (cns) Processes + integrates info: peripheral nervous system (pns) figure 13. 7 & 13. 29. Consists of: cranial nerves to/from brain, spinal nerves to/from spinal cord. 2 divisions of pns: figure 11. 1: sensory/afferent division enters. Has sensory receptors that detect stimuli (change in internal or external environments: motor/efferent division. Nerves convey impulses away from cns exits innervates (supplies signals/nerves to) effectors = muscles + glands (endocrine or exocrine) Nervous system organization: figure 11. 2: nervous system: histology. Mostly amitotic (irreplaceable) you cant make more of them: exceptions = taste, olfaction, memory. Groups/clusters in cns = nuclei (gray matter) Groups/clusters in pns = ganglia: processes from cell body, dendrites. Receive incoming messages + relay to cell body: axon. Axon hillock = where axon meets cell body. Axon terminal = typically branched with synaptic end bulbs (enlarged tips)