Nervous System Flashcards
Collection of axons wrapped in connective tissue
Nerve
Nerve cell, excitable transmit electrical signals
Neuron
Nerve fibers
Axons
Functions of nervous system
Sensory input
Integration
Motor output
Outside CNS consists of nerves extend from brain and spinal cord
Cranial nerves, spinal nerves, ganglia
PNS divided into 2 divisions
Sensory (afferent): signals picked up by sensory receptors throughout the body and carried by nerve fibers of PNS to CNS
Motor (efferent): signals carried away from CNS by nerve fibers of PNS to innervate muscles and glands
Motor division is divided into
Somatic: conducts impulses away from CNS to skeletal muscles (voluntary control)
Autonomic: conducts impulses away from CNS to viscera (involuntary control)
Autonomic divided into
Sympathetic: fight or flight
Parasympathetic: rest and digest Maintain basic body functions
Non-excitable support cells surround neurons
Neuroglia
Clusters of nerve cell bodies in CNS
Nuclei
Clusters of nerve cell bodies outside CNS
Ganglia
Processes branch out from cell body
Receiving signals & direct signals towards cell body
Dendrites
Single process arises from cell body
Cone shaped region near cell body
Axons
Axon hillock
Site where nerves communicate with one another
Synapse
Neuron conducts signals toward a synapse
Presynaptic neuron
Neuron transmits signals away from a synapse
Postsynaptic neuron
Gap in between presynaptic and postsynaptic
Synaptic cleft
Two distinct processes: one dendrite & one axon with a cell body in between
Bipolar neurons
Short single process emerges from cell body & divides into an inverted T into 2 long branches
1 branch- central into CNS = central process
Other branch- extends peripherally = peripheral process
Most sensory neurons of PNS are these
Unipolar (pseudounipolar) neurons
2 or more dendrites and single axon
Most abundant
All motor neurons are these
Multipolar neurons
Lie between motor and sensory neurons
Most are multipolar and found only in CNS
Interneurons
Star shaped cells
Most abundant type of glial cel in CNS
Form blood brain barrier, maintain ion and neurotransmitter concentrations
Astrocytes
Macrophages of the CNS
Remove debris, damaged tissues, and infectious microorganisms
Microglia
Production & circulation of cerebrospinal fluid (CSF)
Ependymal cells
Produce myelin
Wrap myelin around multiple axons
Oligodendrocytes
In PNS, myelinate one segment of one axon
Schwann cells
Glial cells in PNS
Satellite cells
Lipid rich sheath surrounds axons
Insulating layer prevents leakage of electrical current, increasing speed of impulse conduction
Myelin sheaths
Gaps in myelin sheath
Nodes of ranvier
Nerve impulses jump from cell membrane of one myelin sheath gap to the next, increases speed impulse conduction
Saltatory conduction
Composed of cell bodies, dendrites, neuroglia, unmyelinated axons
Found in outer portion of brain and in inner portion of spinal cord
Gray matter
Myelinated axons
Inner portion of brain and outer portion of spinal cord
White matter
Ascending axons in white matter of spinal cord
Bring sensory information from PNS to brain
Descending axons in white matter of spinal cord
Bring motor information from brain to the body
Connective tissue surrounding outside of nerve
Epineurium
Connective tissue surrounding a nerve fascicle
Perineurium
Bundle of nerve fibers (axons)
Fascicle
Connective tissue surrounding an individual nerve fiber
Endoneurium
Sensory neurons of PNS transmit sensory information from receptors
To CNS
Motor nerves of PNS transmit motor information from CNS
To effector organs
Interneurons in CNS gray matter receive sensory information from afferent neuron
And direct a response stimulating a efferent neuron
Involuntary rapid motor response to a stimulus
Reflex
Chain of neurons responsible for reflexes
Has 5 components
Reflex arc
Receptor, sensory neuron, integration center, motor neuron, effector
Site where stimulus acts located at peripheral end of sensory neuron
Receptor
Transmits sensory impulse to CNS
Sensory neuron
Consists of 1 or more synapses in gray matter of CNS
Directs response from sensory signal
Integration center
Transmits motor impulses away from CNS to an effector in periphery
Motor neuron
Muscle or gland that contracts or secretes
Effector
Reflex only one synapse is present in reflex arc
No interneuron
Sensory neuron synapses directly on motor
Knee jerk reflex
Monosynaptic reflex
More than one synapse in reflex arc
At least one interneuron
Withdrawal reflex
Polysynaptic reflex arc
Pain sensed through receptor in skin
Sensory information sent to CNS activating interneuron
Motor neuron going to forearm flexors is stimulated causing muscle contraction withdrawals hand away from painful stimulus
Withdrawal reflex
Autoimmune demyelination’s disease of CNS
Lymphocytes destroys myelin & inflammation
Scarring of myelin occurs along white matter
Vision disturbances, weakness, paresthesias
Multiple Sclerosis
Autoimmune disease of PNS
Bacterial GI infection & respiratory infections
Weakness begins in distal lower extremities & ascends to diaphragm = respiratory failure
Guillain-Barré syndrome
