LC 4-14 (1) Flashcards
Specific segments of the skin supplied by a single spinal nerve
Dermatome (dermatome maps fig 14.13)
Disorder of reactivation of chicken pox virus
shingles
Three Sensory pathways
Primary sensory neuron, secondary sensory neuron, tertiary
first neuron in chain, unipolar neuron picks up signals from eg hand, sends to spinal cord, cell body in posterior root ganglia, synapses in dorsal horn of spinal cord, axon projects to secondary neuron within CNS
Primary Sensory Neuron
interneuron, multipolar, cell body in the posterior horn of the spinal cord, axon sends signal to thalamus
Secondary sensory neuron
interneuron in thalamus, multipolar, cell body in thalamus, sends signal to primary somatosensory cortex (postcentral gyrus) in parietal lobe, ends up connecting with motor portion
Tertiary neuron
upper and lower motor neuron
Two Motor pathways
multipolar, cell body in primary motor cortex (precentral gyrus) in frontal lobe, sends signals to lower motor neuron, syanpses in anterior horn of spinal cord
Upper motor neuron
multipolar, cell body in anterior horn of spinal cord, sends signal out through anterior root of spinal cord, sends signal to muscle
Lower motor neuron
Upper motor neuron problems cause what
spastic issues
Lower motor neuron causes what issues
weakness and flaccid issues
Rapid, pre-programmed, involuntary reactions of muscles and glands, survival mechanisms
reflexes
5 steps of reflex arc
Stimulus activates receptor, nerve signal travels through sensory neuron to spinal cord, signal is processed by interneurons, motor neuron transmits signal to effector, effector responds to signal
Reflex effecting same side
Ipsilateral reflexes
Reflex effecting other side
Contralateral reflex
Simplest of all reflexes, one synapse, two neurons
monosynaptic reflex
Reflex involving more than 1 synapse and more than 2 neurons
Polysynaptic reflex
Reflexes that only use spinal cord, not brain, still present in paralyzed people
Spinal reflexes
Monosynaptic, ipsilateral reflex, reflexive contraction of muscle after stretching, muscle that detects the stretch is what contracts
stretch reflex
Shutting down muscles on other side during stretch reflex to prevent overstretch, eg inhibit triceps during biceps stretch
Reciprocal inhibition
Polysynaptic, ipsilateral reflex, detects overcontraction and causes muscle to relax
Golgi tendon reflex
Contraction of muscles on other side to prevent overcontraction, eg activation of triceps brachii during full flexion of biceps brachii
Reciprocal activation
Polysynaptic, ipsilateral reflex, tend to be in response to painful or surprising stimuli, motor neurons signaled to flex
Withdrawal reflex
Polysynaptic, contralateral reflex, causes other side to extend, eg withdrawal reflex from painful stimuli while extending opposite side
Crossed-extensor reflex
Reflex diminished or absent, may indicate nerve, muscle, or tendon damage
Hypoactive reflex
Abnormally strong reflex, almost always due to brain trauma
Hyperactive reflex
Segments of skin supplied by single spinal nerve; can be used to indicate spinal nerve damage or referred pain from an organ also supplied by the nerve
dermatome
What are the three characteristics common to most nervous system pathways
Travel through white matter of the spinal cord, have paired tracts of sensory and motor pathways, each pathway has 2 or 3 neurons working in a chain
When a pathway affects the opposite side of the body the stimuli was received on
contralateral
When a pathway affects the same side of the body the stimuli was received on
ipsilateral
AKA ascending pathways; carry info about proprioception, touch, temperature, pain, damage, etc. towards CNS; includes somatosensory and viscerosensory; at least 2 sensory neurons in path
sensory pathway
First neuron in chain; detects stimuli with dendrite receptors; cell bodies in posterior root ganglia of spinal nerves; axon projecting to secondary neuron within CNS
Primary neuron
Interneuron; cell body within posterior horn of spinal cord or brainstem nucleus; axons project to thalamus or cerebellum or olfactory cortex (smell only)
Secondary neuron
If secondary neuron projected to thalamus, then there is a _________ in the path (if projected to cerebellum or olfactory cortex, the path ended there); interneurons; cell body in thalamus; axons project to somatosensory cortex
Tertiary neuron
AKA descending pathways; carry information to control effectors in response to stimuli; includes somatomotor and autonomic/viscera motor pathways; may have only 1 motor neuron in the case of reflexes; otherwise at least 2 motor neurons
motor pathway
Cell body within cerebral cortex; axons project to lower motor neurons; excites or inhibits activity of lower motor neuron
Upper motor neuron
Cell bodies within anterior horn of spinal cord; exits CNS and project to skeletal muscle; always excitatory
Lower motor neuron
What are the 4 main properties of a reflex
stimulus, rapid response, preprogrammed response, involuntary response
Property of a reflex required to initiate reflex
stimulus
Property of a reflex required few neurons and synaptic delay is minimal
rapid response
Property of a reflex that occurs the same way every time
preprogrammed response
Property of a reflex requiring no conscious intent of preawareness
involuntary response
What are the five steps involved in activation of a reflex
(1) Stimulus activates a receptor, (2) sensory neuron sends signal to the CNS, (3) information is processed and transmitted to motor neuron, (4) motor neuron transmits signal to an effector, (5) the effector responds to the nerve signal
Type of reflex where both receptor and effector are on same side of spinal cord
ipsilateral
Type of reflex where receptor and effector are on opposite sides of spinal cord
contralateral reflex
Quickest/simplest reflex path; no interneurons involved; sensory axons directly synapsing on motor neurons; so only one synapse needed; usually very simple response
monosynaptic reflex
More complex/slower pathways; interneurons involved; multiple synapses needed to complete arc; more involved effector responses possible
polysynaptic reflex
Monosynaptic reflex that regulates skeletal muscle length; after stretching of a muscle - reflexive muscle contraction results in muscle shortening
Stretch reflex
Polysynaptic reflex that prevents muscles from contracting excessively; after contracting of a muscle-reflexive muscle relaxation results in muscle lengthening
Golgi tendon reflex
Polysynaptic ipsilateral reflex that pulls afflicted limb away from painful stimuli; signals contraction/relaxation of muscles as needed
Withdrawal reflex
Polysynaptic, contralateral reflex that signals the opposite side of the body to move away from a painful stimuli; often in conjunction with withdrawal reflex
Crossed-extensor reflex
(Low) reflex diminished or absent; may indicate damage to spinal cord, muscle, or neuromuscular junction
Hypoactive reflex
(High) abnormally strong response; may indicate damage in brain or spinal cord
Hyperactive reflex
Part of the brain that creates dopamine
Substantia nigra
Part of the limbic system that helps with memory
Hippocampus
