ANAT 7390 Lecture Notes - Lecture 1: Multipolar Neuron, Peripheral Nervous System, Axon Hillock
17 Jun 2018
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1
TOPIC XIX: NERVOUS SYSTEM
A) Nervous System Overview:
- 2 divisions:
1) Central Nervous System (CNS)
- command centre
- brain + spinal cord
- processes + integrates information
2) Peripheral Nervous System (PNS)
- consists of:
a) cranial nerves
to/ from brain
b) spinal nerves
to/ from spinal cord
- 2 divisions of PNS:
a) sensory/afferent division
- has sensory receptors that detect stimuli (changes in the
internal or external environments
- nerves convey impulses toward CNS
b) motor/efferent division
- nerves convey impulses away from CNS
- innervates (supplies nerves to) effectors = muscles +
glands (endocrine or exocrine)
Relationship between CNS and PNS:
PNS PNS
Receptors CNS Effector
detect afferent integrate efferent muscles +
stimuli (sensory neurons) (motor neurons) glands
- executes
response
Example:
Yikes!
hand touches sensory receptor CNS pull hand away
(effector = something hot skeletal muscle)
(stimulus)
2
Nervous System Organization:
B) Nervous System: Histology
- Cell types:
1) Neurons
- conduct impulses
- make up CNS + PNS
- mostly amitotic (irreplaceable)
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
- carries impulses away from cell body
- axon hillock - where axon meets cell body
- axon terminal → typically branched with synaptic
end bulbs (enlarged tips)
- may be:
① myelinated – wrapped in many layers of
cell membrane from Schwann cells
(PNS) or oligodendrocytes (CNS)
3
- electrical insulation
- gaps in myelin sheath are called
nodes of Ranvier
- myelinated axon bundles in:
- CNS = tracts (white
matter)
- PNS = nerves
② unmyelinated - no myelin
2) Neuroglia (glial cells)
- support neurons = can undergo mitosis (prone to cancer – brain
tumour)
- types:
a) CNS neuroglia
i) oligodendrocytes
- produce myelin around axon
ii) microglia
- protective ⇒ become phagocytic if detect
infected, dead or damaged neurons
(because immune cells can’t
enter CNS)
iii) astrocytes
- surround blood capillaries to form part of blood
brain barrier (BBB)
- help control capillary permeability
iv) ependymal cells - neural epithelium
- line brain ventricles + central canal of 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 cells bodies in ganglia
- protection and support
Neuron Classification:
1) Structural/Anatomical Types:
- based on number of processes coming off cell body
a) unipolar
- 1 process that divides into two: central + peripheral
Document Summary
Topic xix: nervous system: nervous system overview: to/ from brain to/ from spinal cord, cranial nerves, spinal nerves, peripheral nervous system (pns) 2 divisions of pns: sensory/afferent division, motor/efferent division. Has sensory receptors that detect stimuli (changes in the. Nerves convey impulses toward cns internal or external environments. Innervates (supplies nerves to) effectors = muscles + glands (endocrine or exocrine) Example: hand touches sensory receptor cns pull hand away (effector = something hot skeletal muscle) (stimulus) muscles + glands. Groups/clusters in cns = nuclei (gray matter) Groups/clusters in pns = ganglia: nervous system: histology. Structure: cell body, processes from cell body, dendrites, axon. Receive incoming messages + relay to cell body end bulbs (enlarged tips) Axon hillock - where axon meets cell body. May be: (cid:3843) (cid:373)yeli(cid:374)ated wrapped in many layers of cell membrane from schwann cells (pns) or oligodendrocytes (cns) Pns = nerves (cid:3844) u(cid:374)(cid:373)yeli(cid:374)ated - no myelin tumour) Support neurons = can undergo mitosis (prone to cancer brain.
