Exam 2: Nervous System I Flashcards
Central Nervous System
- brain and spinal cord
- control center
- president
Peripheral Nervous System (PNS)
- cranial nerves, spinal nerves and ganglia
- ganglion=group of neuron cell bodies located outside CNS
- workers
Sensory (afferent) Division
receives information FROM body and transmits it TO CNS for processing
-has both CNS and PNS parts
Somatic Sensory
- part of sensory division
- receives sensory information from skin, joints, muscle, special senses (vision, hearing, balance, smell, taste)
Visceral Sensory
- part of sensory division
- receives sensory info from blood vessels and viscera
Motor Division
transmits info FROM the CNS To muscles and glands
-has both CNS and PNS parts
Somatic Motor
- part of motor division
- innervate skeletal muscle
- voluntary
Autonomic Motor
- part of motor division
- innervates smooth muscle, cardiac muscle, and glands of viscera (organs)
- involuntary
Neurons
- respond to stimuli and conduct nerve impulses
- primarily amitotic
Glial Cells
- support and protect neurons
- many more glial cells than neurons
- divide by mitosis
Cell Body of Neuron
-function: neuron’s control center or head
Nucleus
- -houses DNA
- contains nucleolus for protein synthesis
Chromatophilic substances (Nissl bodies)
- rough ER inside cell body
- function: protein synthesis
- look like darkened clumps within cytoplasm
- no chromatophilic substance in axon hillock
Dendrites
- short nerve cell process
- function: receive input (incoming nerve impulses)
- send nerve cells to cell body
- neuron can have 1 or many dendrites
Axon
- long nerve cell process
- function: send output (outgoing nerve impulses
- one axon per neuron
Axon Hillock
- portion of the cell body from where the axon originates
- no chromatophilic substance here
Multipolar Neuron
- one axon and many dendrites
- most common
- ex: motor neurons, interneurons
Bipolar Neuron
- two processes: one axon and one dendrite
- limited in location (rare)
- ex: retina of eye, olfactory neurons in nose
Unipolar (Pseudounipolar) Neuron
- Single process comes off of the cell body and divides into two branches
- common
- most (not all) sensory neurons
Sensory (afferent) Neuron
- brings information TO CNS
- either unipolar or bipolar neurons
Motor (efferent) Neuron
- takes information FROM CNS to other parts of the body
- all are multipolar
Interneuron
- help coordinate and integrate info between sensory and motor neurons
- located solely in CNS
- “translator/mediator”
- multipolar in form
Neuron Classification
-by structure or by function
Satellite Cells
- In PNS
- surround neuron cell bodies in spinal ganglia
- protect the cell bodies
- regulate nutrient exchange and waste removal
Neurolemmocytes (Schwann Cells)
- myelinate axons in PNS
- myelin is a protective covering around axon that insulates axon and helps produce faster nerve impulses
- can also help regenerate damaged PNS axons
Astrocytes
- in CNS
- regulate transfer of materials from blood to the brain, help workings of BBB
- helps make blood vessels less leaky
Blood Brain Barrier
- keeps harmful substances away from brain
- selectively permeable
- bust some needed substances can’t pass this barrier either like chemotherapy drugs
Astrocytes and the BBB (Parkinsons)
- caused by a decrease of a dopamine
- dopamine can’t pass the BBB but a related drug, L-dopa, can.
- Cocaine and methamphetamine pass through and damage BBB
Oligodendrocytes
- myelinates multipe axons in CNS
- to CNS as neurolemmocytes are to PNS
Microglia
- phagocytize damaged neurons in CNS
- replicate when there is CNS damage and need to clean up an area
Ependymal Cells
- line central canal and ventricles of CNS
- help circulate CSF
- central canal and ventricles are spaces within the spinal cord and brain respectively
Myelination
- process of wrapping an axon with myelin
- myelin insulates axon, produces a faster nerve impulse
- dendrites are not myelinated
Myelination Procedure in PNS
- Neurolemmocyte wraps around a 1 mm portion of an axon successively
- Cytoplasm and nucleus of neurolemmocyte gets “squeezed” to the outside
- inner successive layers of cell membrane make up the myelin sheath of neurolemocyte
Neurofibril Nodes (Nodes of Ranvier)
- separate neurolemmocytes
- axon unmyelinated here
- nerve impulse is generated at these nodes
Myelination in CNS
- one oligodendroyte myelinates 1 mm portions of many axons
- similar to PNS but oligodendrocytes myelinate CNS axons
