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Lecture 13
Human Nervous System |
-Central Nervous System (CNS)
A. Brain
B. Spinal Cord
-Peripheral Nervous System (PNS)
A. Somatic (voluntary)
B. Autonomic (involuntary)
- composed of conducting elements or cells called neurons and accessory elements called neuroglia (supporting cells) and meninges (coverings) |
Neurons |
-responsible for recieving and transmitting information
-classified according to function and structure |
sensory (afferent) neuron |
- neuron that delivers info to CNS |
motor (efferent) neuron |
- neuron that carries info to periphery (ie muscle) |
associative (interneuron) neuron |
- located between sensory and motor neurons
- modifies responses to other neurons |
multipolar neuron |
- multiple processes attached to cell body
- found throughout brain and spinal cord
|
bipolar neuron |
- two processes attached to cell body
- found in retina of eye and inner ear
|
unipolar neuron |
- one process attached to cell body
- found in ganglia (clusters of neurons adjacent to spinal cord) |
Cell body of a neuron |
contain:
-most of the organelles typically found in cells (ex nucleus, mitochondria, etc)
-nissi bodies
- neurofibrils |
nissi (chromatophilic) bodies |
-clusters of free ribosomes that produce protein (ex neurotransmitters) and rough ER
|
neurofibrils |
-represent cytoskeleton of neuron
- helps maintain shape of nerve cell body |
neurofibrils |
-represent cytoskeleton of neuron
- helps maintain shape of nerve cell body |
Dendrite |
-process (fiber) of a neuron
- more than one per neuron
- transmits info into cell body |
Dendrite |
-process (fiber) of a neuron
- more than one per neuron
- transmits info into cell body |
axon (nerve fiber) |
-process (fiber) of a neuron
-only one per neuron
- transmits info from cell body |
axon (nerve fiber) |
-process (fiber) of a neuron
-only one per neuron
- transmits info from cell body |
myelin sheath |
- produced by oligodendrocyte in CNS and by schwann cell in PNS
- composed of lipid
- conducts electrical impulses
|
myelin sheath |
- produced by oligodendrocyte in CNS and by schwann cell in PNS
- composed of lipid
- conducts electrical impulses
|
neurilemma |
cell wall of oligodendrocyte or schwann cell |
neurilemma |
cell wall of oligodendrocyte or schwann cell |
nodes of ranvier |
bare area - area not covered by myelin |
nodes of ranvier |
bare area - area not covered by myelin |
Types of Neuroglia ("neural-glue") |
in the CNS
-oligodendrocyte
-microglia
-astrocyte (don't forget blood-brain barrier)
-ependymal cells
in the PNS
-schwann cells
-satellite cells
|
Types of Neuroglia ("neural-glue") |
in the CNS
-oligodendrocyte
-microglia
-astrocyte (don't forget blood-brain barrier)
-ependymal cells
in the PNS
-schwann cells
-satellite cells
|
oligodendrocyte |
-located in CNS
-cells that produce myelin covering around nerve fibers (axons)
|
oligodendrocyte |
-located in CNS
-cells that produce myelin covering around nerve fibers (axons)
|
microglia |
-located in CNS
-phagocytic cells of CNS
-ingests dead or damaged tissue |
microglia |
-located in CNS
-phagocytic cells of CNS
-ingests dead or damaged tissue |
astrocyte |
-located in CNS
-cells that assist in the nourishment of neurons in the CNS
-helps form "blood-brain barrier" |
astrocyte |
-located in CNS
-cells that assist in the nourishment of neurons in the CNS
-helps form "blood-brain barrier" |
blood-brain barrier |
-formed by astrocyte
-regulates what substances pass from bloodstream into CNS
-composed of:
1)astrocyte
2)basement membrane
3)endothelial wall of capillary
|
blood-brain barrier |
-formed by astrocyte
-regulates what substances pass from bloodstream into CNS
-composed of:
1)astrocyte
2)basement membrane
3)endothelial wall of capillary
|
ependymal cells |
-located in CNS
-cells that line the cavities of ventricles of the brain |
ependymal cells |
-located in CNS
-cells that line the cavities of ventricles of the brain |
schwann cells (neurolemmocytes) |
-located in PNS
-produce myelin covering around nerve fibers (axons) in PNS
|
schwann cells (neurolemmocytes) |
-located in PNS
-produce myelin covering around nerve fibers (axons) in PNS
|
satellite cells |
-located in PNS
-regulate nourishment to neurons in PNS |
satellite cells |
-located in PNS
-regulate nourishment to neurons in PNS |
nuclei |
cluster of neurons in CNS |
nuclei |
cluster of neurons in CNS |
ganglia (ganglion) |
cluster of neurons in the PNS |
ganglia (ganglion) |
cluster of neurons in the PNS |
nerve |
bundles of axons in PNS |
nerve |
bundles of axons in PNS |
tract |
bundles of axons in CNS |
tract |
bundles of axons in CNS |
synapse |
-site of communication between neurons
-located in synaptic cleft (space) between them
-composed of:
-pre synaptic neuron
-synaptic cleft
-post synaptic neuron
-neurotransmitter in a pre synaptic axon is released across a synapse to attach to receptor sites on dendrite of post synaptic dendrite |
synapse |
-site of communication between neurons
-located in synaptic cleft (space) between them
-composed of:
-pre synaptic neuron
-synaptic cleft
-post synaptic neuron
-neurotransmitter in a pre synaptic axon is released across a synapse to attach to receptor sites on dendrite of post synaptic dendrite |
conduction of nerve impulse |
electrical impulse causes change of permeability of membrane
causes NA+ on outside to move inside |
conduction of nerve impulse |
electrical impulse causes change of permeability of membrane
causes NA+ on outside to move inside |
Continuous Conduction vs. Saltatory Conduction |
Continuous - impulse travels in continuous flow along an axon
Saltatory - impulse jumps or is transmitted from node of of ranvier to another |
Continuous Conduction vs. Saltatory Conduction |
Continuous - impulse travels in continuous flow along an axon
Saltatory - impulse jumps or is transmitted from node of of ranvier to another |
A-fibers |
-most heavily myelinated
-produces sharp pain |
A-fibers |
-most heavily myelinated
-produces sharp pain |
B-fibers |
-intermediate amount of myelin |
B-fibers |
-intermediate amount of myelin |
C-fibers |
-least amount of myelin, no myelin in some cases
-produces dull pain
|
C-fibers |
-least amount of myelin, no myelin in some cases
-produces dull pain
|
excitatory neurotransmitters |
- cause deploration of the postsynaptic neuron
1. acetylcholine
2. norepinephrine
3. serotonin
4. dopamine |
excitatory neurotransmitters |
- cause deploration of the postsynaptic neuron
1. acetylcholine
2. norepinephrine
3. serotonin
4. dopamine |
inhibatory neurotransmitters |
-hyperpolarize the postsynaptic neuron preventing the transmission of the nerve impulse across the synapse
1. GABA - inhibits cerebellum
2. enkephalins -
effects mimicked by heroin and morphine
3. endorphins -
4. dopamine - found in automatic nerve systems |
inhibatory neurotransmitters |
-hyperpolarize the postsynaptic neuron preventing the transmission of the nerve impulse across the synapse
1. GABA - inhibits cerebellum
2. enkephalins -
effects mimicked by heroin and morphine
3. endorphins -
4. dopamine - found in automatic nerve systems |