Exam 3: Chapter 13 Flashcards
where are neural reflexes integrated at? are they somatic or autonomic neurons?
entirely in the spinal cord
-both somatic and autonomic neurons
what does innate mean?
born with them, not learned
-patellar stretch, urination
what does conditioned mean?
learned and acquired through experience
-modulating urinary reflex (potty training)
what does it mean by a monosynaptic reflex?
no interneurons, only afferent & efferent neurons
-Stretch Reflex
what does it mean by a polysynaptic reflex?
multiple interneurons b/w afferent & efferent neurons
-Flexion Reflex
are autonomic (visceral) reflexes monosynaptic or polysnaptic? are they usually spinal or cranial?
polysynaptic
-use both spinal and cranial integration
-EX: urination, deification
do skeletal muscles send both excitatory and inhibitory signals?
NO, only excitatory
-contraction!
what are extrafusal fibers?
contractile fibers surround the muscle
-AP leads to contraction of fibers
-gets info through alpha neurons
what are intrafusal fibers?
fibers inside the muscle spindle
-ENDS: contractile, get efferent signals from gamma neurons
-MIDDLE: non-contractile, sends afferent signals to CNS, lack myofibrils
when are gamma neurons activated?
at the same time alpha motor neurons are activated
what is the golgi tendon organ reflex?
responds to muscle tension during the isometric phase of contraction
-uses free nerve endings and combines it’s info with other feedback
-series of elastic elements
what are muscle spindles?
responds to muscle stretch (length of muscle) that creates the stretch reflex
-small, elongated
-arranged parallel to extrafusal fibers
is the stretch reflex monosynaptic or polysynaptic?
monosynaptic
what is the stretch reflex w/o reciprocal inhibition?
- stretch signal in extrafusal fibers is detected by the muscle spindle
- muscle spindle stretches and increases afferent firing signal
- spinal cord excites and synapses with alpha & gamma motor neurons
- alpha and gamma motor neurons activate
- alpha neurons increases the efferent excitatory signal to the extrafusal fibers to contract the extensor
- gamma neuron uses alpha-gamma coactivation to shorten / length the muscle spindle in proportion to the muscle fibers by sending excitatory signals to the intrafusal fibers
what is a myotatic unit?
collection of pathways controlling a single joint
what is reciprocal inhibition?
you have to relax the flexor due to the extensor contraction in order to perform the movement
-occurs in antagonistic muscle groups
in reciprocal inhibition of the stretch reflex of the quad, what antagonistic muscle is relaxing? is this monosynaptic?
hamstring relaxes = POLYSYNAPTIC
quad contraction = MONOSYNAPTIC
what is the stretch reflex pathway w/ reciprocal inhibition?
- stretch is detecting by muscle spindle
- increases afferent firing signal to spinal cord
- spinal cord activates alpha and gamma motor neurons
- two pathways of alpha motor neurons
4a. one excites and causes contraction of the extensor
4b. one goes to an inhibitory interneuron to block AP’s and causes the flexor to stay relaxed - gamma alpha neurons contract intrafusal fibers in the muscle spindle (alpha-gamma coactivation)
is the flexion reflex monosynaptic or polysynaptic?
polysynaptic
what is the flexion reflex used for?
to pull away from a painful stimulus
what is the flexion reflex pathway for the right and left foot?
- painful stimulus activates nociceptor in right foot
- muscle spindle detects stretch
- afferent signal goes to spinal cord and signal diverges into multiple interneurons (4+) that go to both the right and left legs
RIGHT LEG
4. one collateral goes to excitatory interneurons to contract flexors using alpha neurons
5. other collateral goes to inhibitory interneurons to relax extensors using alpha neurons
6. withdrawal reflex pulls right foot away from stimulus
LEFT LEG
7. one collateral branch goes to excitatory interneurons to contract extensors using alpha neurons
8. other collateral branch goes to inhibitory interneurons to relax flexor using alpha neurons
9. crossed extensor reflex supports body weight as right foot withdrawals form pain stimulus
during the flexion reflex using the right and left feet, which muscle group contracts in each foot?
RIGHT: flexor contracts
LEFT: extensor contracts
what are each of the three body movements (reflex, voluntary, & rhythmic) stimulated by?
reflex: external stimuli
voluntary: external stimuli or at will
rhythmic: initiation & termination at will
describe what CPGs (central pattern generators) do for rhythmic movement?
they maintain movement after initiation
-located in the spinal cord
rate the complexity of each of the body movements? (reflex, voluntary, & rhythmic)
reflex: least complex
voluntary: most complex
rhythmic: intermediate complexity
where are each of the body movements (reflex, voluntary, & rhythmic) integrated at?
reflex: entirely in spinal cord
voluntary: cerebral cortex
rhythmic: spinal cord w/ input from cerebral cortex
what are examples for each of the body movements?
reflex: knee jerk, coughing, postural reflex
voluntary: playing piano
rhythmic: walking, running
what is the postural reflex?
helps maintain body position and influences voluntary movement
what does the spinal cord do for movement?
spinal reflexes, contains CPGs
what does the brainstem do for movement?
posture, hand & eye movement
what does the cerebral cortex do for movement?
planning & coordinating voluntary movements
what does the cerebellum do for movement?
adjusts & monitors voluntary movement, keeps balance
what does the thalamus do for movement?
relay station for the cerebral cortex
what does the basal ganglia do for movement?
coordinates movement, feedback
-releases DA
-sends inhibitory signals to suppress unwanted movement
what are the three stages of voluntary movement?
- Decision-Making & Planning
- Initiating Movement
- Executing the Movement
what three parts of the brain deal with Decision-Making & Planning? what do each of them do for movement?
cerebellum: body position, balance
cerebral cortex (association areas): visual & vestibular awareness
basal ganglia: modulate & plan movement, sends feedback to cerebral cortex through the thalamus
what brain part deals with initiating movement? what does it do?
motor cortex: organizes execution of movement, sends signal to effectors
what three parts of the brain deal with executing the movement? what do each of them do?
brainstem: hand & eye movement
spinal cord: goes through corticospinal tract (crossing over), synapses w/ motor neurons
cerebellum: makes postural adjustments to maintain balance even after / during the movement
what is the corticospinal tract?
descending tract from motor cortex -> spinal cord
-travels down brainstem
-crosses over in the medulla pyramids
-synapses w/ alpha neurons in SC
sends feedback to continue to maintain balance and receive sensory info after / during the movement
what is feedforward postural reflexes?
-allow body to prepare / anticipate for voluntary movement
-helps create a smooth & continuous motion by maintaining balance
how does a disfunction in the basal ganglia create Parkinson’s Disease?
able to plan movement but cannot initiate the movement
-unable to secrete DA normally
what are three treatments to Parkinson’s Disease? how do they work?
L-Dopa: precursor for DA that is able to cross the BBB and form DD
DA agonists
MAO inhibitors: stops MAO from breaking down DA
