MS-1 FUND 1: 10:00-11:00
Monday, September 15, 2014
Dr. Cotlin
Nervous Tissue
Transcriber: Haley Gates
Editor: Sami Ashley
Page 1 of 4
Abbreviations:
Introductory Comments: This is the first hour of the lecture give by Dr. Cotlin on Nervous Tissue. This lecture includes a
description of the structure and function of the nervous system.
Announcements: An exam review of tests 1 & 2 is scheduled for Tuesday, September 16 at 1:00 p.m. There will be an
Embryogenesis review session on Thursday, September 18 at 1:00 p.m. Also, a Surgical Anatomy Session is scheduled
for Wednesday, September 24 at 8:00 a.m.; the exam review will be shifted to 10:00 a.m.
Nerve Tissue
Organization of Nervous System (slide 4) 5:38
a. Central Nervous System
i. Brain
ii. Spinal Cord
b. Peripheral Nervous System
i. Nerves that branch from the spinal cord
1. Cranial Nerves
2. Spinal Nerves
3. Peripheral Nerves would be ALL nerves that are Cranial and Spinal Nerves
ii. Associated ganglia
1. Large collections of neuron cell bodies
a. All neuronal cell bodies are located in the CNS or in the Peripheral Nervous System housed
in ganglia
II. Organization of the Central Nervous System and the Peripheral Nervous System (slide 5) 7:23
a. Afferent – any nerve that is receiving information from the periphery and transmitting the information to the
Central Nervous System
i. Sensory information. Major senses such as nose, eyes, and ears are all enriched with afferent nerve
signaling.
b. Efferent – any nerve that is carrying information from the Central Nervous System to the periphery
c. There isn’t always one nerve, one signal or one nerve, one function; there can be a relay system composed of
multiple nerves.
III. Peripheral Nervous System (slide 6) 10:04
a. Somatic Nervous System – voluntary functions
i. Synonymous with the Motor System
ii. Regulates and controls Skeletal Muscle
b. Autonomic Nervous System – involuntary functions
i. Sympathetic Nervous System – fight or flight
ii. Parasympathetic Nervous System – rest and digest
iii. Enteric Division – unique set of ganglia that control movement in the GI tract. Sometimes called the “brain
of the gut.”
c. Most organs, with a few exceptions, are innervated by both Sympathetic and Parasympathetic neurons.
d. Sympathetic and Parasympathetic responses are not an all-or-none response in the body as a whole or in an
organ system.
e. Components:
i. Cranial Nerves
ii. Spinal Nerves
iii. Peripheral Nerves
iv. Ganglia
1. Somatic or Sensory – housed in the dorsal root ganglia
2. Autonomic - Sympathetic, Parasympathetic, Enteric
v. Specialized Nerve Endings
IV. Classification of Neurons or Nerve Cells (Slides 7,8,9) 13:42
a. Morphology
i. Size
ii. Number of processes
iii. Shape
iv. Three basic morphological categories:
1. Multipolar – multiple processes on dendritic end and an axon (found in the CNS)
2. Bipolar – two processes- dendritic process and an axon (Retina, Ear)
3. Unipolar (Pseudounipolar) – one process (Sensory nerves of the Somatic Nervous System)
I.
MS-1 FUND 1: 10:00-11:00
Monday, September 15, 2014
Dr. Cotlin
Nervous Tissue
Transcriber: Haley Gates
Editor: Sami Ashley
Page 2 of 4
Abbreviations:
v. Side Note: Cell Body is referred to as the soma. The processes that receive information for any given
neuron are the dendritic processes. The transmitting process is the axon. On any given neuron there is
only one axon protruding from the cell body.
b. Function
i. Sensory – a neuron that is sensing from the periphery and carrying the signal to the Central Nervous
System
1. Pseudounipolar and bipolar neurons – neurons that are sensing information in the Peripheral
Nervous System
2. Integrative neurons – found in the Central Nervous System; integrate the signals coming in and out
of the Central Nervous System
ii. Motor – a neuron that moves a type of muscle (skeletal, cardiac, smooth)
1. The majority will be multipolar neurons
2. Motor neurons are found in the Autonomic Nervous System and Somatic Nervous System
3. If motor neurons are situated in a two-neuron system, then there will be a preganglionic/presynaptic
and postganglionic/postsynaptic portion.
iii. Excitatory
iv. Inhibitory
c. Neurotransmitter
1. Note: Dr. Cotlin stated that we “do not have to worry about these right now”
ii. Adrenergic
iii. Cholinergic
iv. Dopaminergic
v. GABAergic
V. Components of a Neuron (Slide 10) 20:17
a. Receptor Region – dendritic end
b. Soma – cell body
c. Conductive Region – axon
d. Telodendron – high branched region of the axon located in the effector region
e. Axon Hillock – region where axon region is extending and branching
f. Dendrite – process that has dendritic spines to increase surface area
VI. Organization of a typical Motor Neuron (Slide 11) 22:25
a. Oligodendrocyte – cells responsible for myelination in the Central Nervous System
i. One Oligodendrocyte to multiple axons
b. Schwann Cell – cells responsible for myelination in the Peripheral Nervous System
i. One Schwann Cell to one axon
VII. Organelles of a Neuron (Slide 12) 24:10
a. Nissl Bodies (aka Nissl Substance)- dense collections of Rough Endoplasmic Reticulum
b. “Vesicular” nucleus, prominent nucleolus
c. Golgi Apparatus
d. Mitochondria
e. Cytoskeleton- microtubules, microfilaments, intermediate filaments
f. Lysosomes
g. Lipofuscin – age related pigment
i. Neurons do not divide, but the tissue can be repaired. As the neurons age, the age spots tend to
accumulate.
VIII. Glial Cells (Slide 13) 24:35
a. Cells of the Nervous System that are supporting cells.
b. NOT neurons – they do not engage in synaptic activity or transmission of information
IX. Key Neuron Functions (Slide 16,17,18,19,20) 28:47
a. Protein Synthesis
i. Involves the RER and free ribosomes (Nissl Bodies)
ii. Structural proteins – such as those in membranes, organelles, cytoplasm, etc.
iii. Enzymatic proteins (sodium-potassium ATPase, enzymes for neurotransmitter synthesis/degradation, etc.)
iv. Protein Synthesis is conducted in the soma and trafficked to the axon or the axon terminal.
v. No protein synthesis in axon or axon terminal.
b. Axonal Transport
i. Anterograde – movement from the cell body to outside the cell
1. Kinesins are always involved in anterograde transport
2. Fast – 300-400 mm/day: organelles, amino acids, nucleotides, neurotransmitters
MS-1 FUND 1: 10:00-11:00
Monday, September 15, 2014
Dr. Cotlin
Nervous Tissue
Transcriber: Haley Gates
Editor: Sami Ashley
Page 3 of 4
Abbreviations:
3. Slow – 1-10 mm/day: tubulin, other MAPs, actin
ii. Retrograde – movement from outside the cell to the cell body
1. Dyneins are always involved in retrograde transport
2. 20-400 mm/day: variety of cellular macromolecules, also exogenous substances like viruses and
toxins
iii. The minus end is near the cell body and the plus end is near the end of a microtubule
iv. A neurotransmitter is made in the cell body and move to the microtubule end by kinesin.
v. If a neurotransmitter needs to be recycled, the neurotransmitter is moved to the cell body by dyneins.
vi. Chemotherapy agents such as vincristine and vinblastine target microtubules to inhibit cell division. As a
result, peripheral neuropathy is a common side effect due to the interruption of microtubules and the
misplacement of neurotransmitters.
c. Synaptic Transmission
i. At the end terminal of the presynaptic membrane, the membrane will depolarize and allow voltage-gated
Calcium channels to open.
ii. Calcium ions will influx into the cell and neurotransmitters in secretory vesicle will be secreted into the
synaptic cleft.
iii. The postsynaptic membrane will contain receptors (G-protein receptor, channel, etc.) to bind the
neurotransmitter.
iv. When the neurotransmitters are bound, the postsynaptic membrane will depolarize; Na+ ions rush in
through ion gates
v. Neurotransmitters that are released from the postsynaptic membrane may be recycled through coated
vesicles on the presynaptic membrane.
vi. Side note: Snare complex, Snap 25 and Synaptotagmin are mediating complexes that help anchor synaptic
vesicles during fusion.
vii. Types of Synapses (Slide 23) 37:57
1. Axosomatic Synapse – axon synapsing with the soma
2. Axodendritic Synapse – axon synapsing with a dendrite
3. Axoaxonic Synapse - axon synapsing on another axon
4. One dendrite can have multiple synapses for a variety of inputs (stimulatory, inhibitory, etc.)
d. Nerve Impulse Conduction (Slide 26) 39:52
i. Rate depends on axon diameter and myelin sheath.
1. Length – dictated by the target of the neuron
2. Diameter – can vary; presence or absence of a myelin sheath; thickness of a myelin sheath
ii. Larger, myelinated fibers: faster rate of impulse conduction (100 m/sec)
1. Large diameter: motor and proprioception
2. Medium diameter: fine touch
3. Small diameter: crude touch and pain
iii. Small, unmyelinated fibers (1 m/sec)
1. Postganglionic sympathetic and parasympathetic fibers
2. Slow diffuse pain fibers
X. Microanatomy of Nerve Fibers (Slide 28,29,30) 42:33
a. Nerve fiber typically means the axon process
b. Axon Components
i. Smooth Endoplasmic Reticulum – helping to recycle the membrane
ii. Microtubules
iii. Intermediate Filaments
iv. Axoplasm = axon cytoplasm
v. Mitochondria
c. Unmyelinated Nerve Fibers (Axons)
i. Axon with associated Schwann Cells that do not wrap around the axon.
ii. The axon is embedded within the Schwann Cells.
d. Myelinated Nerve Fibers (Axons)
i. Axon with a Schwann Cell tightly wrapped around the axon.
e. Schwann Cells (Neurolemmocyte)
f. Basal lamina surrounds the whole nerve fiber
XI. The Process of Myelination by a Schwann Cell (Slide 34) 48:26
a. Neurolemmocyte starts to wrap around a portion of an axon.
i. The axon communicates to the plasma membrane to begin wrapping.
b. Neurolemmocyte cytoplasm and plasma membrane begins to form consecutive layers around the axon.
MS-1 FUND 1: 10:00-11:00
Monday, September 15, 2014
Dr. Cotlin
Nervous Tissue
Transcriber: Haley Gates
Editor: Sami Ashley
Page 4 of 4
Abbreviations:
c. Regulation of myelination is dependent on Neuregulin- a transmembrane protein on the neurolemma of the
axon.
d. The overlapping layers of the neurolemmocyte plasma membrane form the myelin sheath.
i. Protein 0 is a homophilic binding protein that will bind to the multiple layers and anchors the extracellular
space.
ii. Myelin basic protein is a spacer in the cytosol.
e. The meurolemmocyte cytoplasm and nucleus are pushed to the periphery of the cell as the myelin sheath is
formed.
<END OF LECTURE 50:21 >