BMS2011 Lecture Notes - Lecture 6: Dense Irregular Connective Tissue, Axon Terminal, Saltatory Conduction
30 May 2018
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Week 3. Spinal Cord and Nerves
NERVOUS SYSTEM
CNS
o Brain and spinal cord
PNS
o Cranial nerves (12 pairs)
o Spinal nerves (31 pairs)
Cervical (8)
Thoracic (12)
Lumbar (5)
Sacral (5)
Coccygeal (1)
o Ganglia; cluster of neuron cell bodies outside of CNS
o Plexuses (cervical, lumbar and sacral)
-network of nerves, limbs and neck
Gaglia ad pleus are’t eres ut are odifiatios of PNS
1. Sensory division:
Receives sensory input from receptors and transmits to CNS
o Somatic sensory: general somatic senses eg. touch, pain, pressure
o Visceral sensory: transmits nerve impulses from blood vessels, viscera to CNS
eg. temperature and stretch (coming from encapsulated organs -> limited
2. Motor division:
Transmits motor impulses from CNS to muscles/glands
o Somatic motor (SNS): nerve impulses from CNS to skeletal muscles
-voluntary
o Autonomic motor (ANS): innervates internal organs, smooth & cardiac muscle,
glands
-sympathetic and parasympathetic
-effector organs
-involuntary/automatic systems
• Neuron structure:
o NS is composed of nervous tissue which is one of 4 primary tissue types (epithelial,
connective, muscle)
o Comprised of:
Neurons: excitable cells -> initiate and transmit nerve impulses
-typically has cell body, dendrites and axons
-high metabolic rate
-extreme longevity
-typically non-mitotic
find more resources at oneclass.com
find more resources at oneclass.com
Glial cells: non-excitable cells -> support and protect neurons/insulation
~80% of NS
-neurolemnocytes AKA schwann cells
-responsible for myelinating PNS axons (myelin sheath is a fatty coating) ->
speeds up rate of transmission
-provides saltatory conduction where nerve is transmitted from node to node
-unmyelinated -> continuous conduction (nerve impulse must travel entire
length of axon – slow nerve impulse)
Cell body (soma)
o Control of neuron
o Receives, integrates and sends impulses
o Clusters of soma in CNS= nucleus
-red nucleus = postural control in axial
o Clusters of soma in PNS = ganglion
Dendrites
o Short processes from body
o May be single or multiple
o Receptive region
o Conducts impulse towards cell body to be processed
o More dendrites = more nerve impulses the neuron can receive from other
cell (roughly measures complexity of information)
Axons
o Longer cell processes
o Most neurons only have one
o Transmits neve impulse away from body to another cell
o Telodendria: processes at end of axon (dendrites at end of axon)
o Axon terminals (synaptic knobs): chemical synapses
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Pns: brain and spinal cord, cranial nerves (12 pairs, spinal nerves (31 pairs) Sacral (5: ganglia; cluster of neuron cell bodies outside of cns, plexuses (cervical, lumbar and sacral) Ga(cid:374)glia a(cid:374)d ple(cid:454)us are(cid:374)"t (cid:374)er(cid:448)es (cid:271)ut are (cid:373)odifi(cid:272)atio(cid:374)s of pns: sensory division: Transmits motor impulses from cns to muscles/glands: somatic motor (sns): nerve impulses from cns to skeletal muscles. Voluntary: autonomic motor (ans): innervates internal organs, smooth & cardiac muscle, glands. Involuntary/automatic systems: neuron structure, ns is composed of nervous tissue which is one of 4 primary tissue types (epithelial, connective, muscle, comprised of: Neurons: excitable cells -> initiate and transmit nerve impulses. Glial cells: non-excitable cells -> support and protect neurons/insulation. Responsible for myelinating pns axons (myelin sheath is a fatty coating) -> speeds up rate of transmission. Provides saltatory conduction where nerve is transmitted from node to node. Unmyelinated -> continuous conduction (nerve impulse must travel entire length of axon slow nerve impulse)
