Cognitive/motor 2 Flashcards
describe motor behaviour
things need cns to move
Purposeful or goal oriented
describe 2 types of motor behaviour
voluntary
reflexive
what do al motor movements require and why
2 muscles
agonist muscle contracts and antagonist relaxes
to make muscle contract = activate motor neurons
to make muscle relax = inhibit motor neurons
describe extension
agonist = extensor muscle contracts
antagonist = flexor muscle relaxes
increases angle around joint
describe flexion
agonist = flexor muscle contracts
antagonist = extensor muscle relaxes
decreases angle around joint
describe reciprocal innervation of muscles
coordinated flexor and extensor muscle activation and relaxation
limb position maintained by balance of flexor and extensor muscle tension
describe motor neurons
only excitatory - ach
alpha = innervate skeletal muscle extrafusal (makes big muscles contract)
gamma = innervates muscle spindle - intrafusal (part of proprioceptive feedback)
cell bodies in ventral horn of spinal cord - spinal nerves or brainstem (cranial nerves)
receives inputs mostly from interneurons
describe spinal afferent pathway
sensory afferent - dorsal root ganglion
synapses both on interneuron and ascends dorsal columns to brain
descrive motor efferent patway
descending motor commands = comes from brain and innervate interneurons, voluntary input
Interneurons = integrate info from many things, like sensory info and motor commands and then activates other circuitry and sends axons and forms motor efferent
name and describe spinal interneurons
descending pathway
other spinal levels = voluntary movements
muscle receptor from antagonistic muscle = length monitoring
spinal interneuron
tendon receptor = tension monitoring, force of muscles
skin receptor = pain, driven by nociceptors
joint receptor = proprioceptive feedback
name 3 spinal reflexes
withdrawal
stretch
inverse stretch
describe withdrawal reflex
protects limb from injury
involuntary - happens at level of spinal cord
can most spinal reflexes be overriden
yesss
like if pain but its important to withdraw limb
describe flexion withdrawal reflex - polysynaptic
polysynaptic= more than one synapse between sensory input and motor response
activate nociceptors = aps up leg and enters dorsal horn and branches of axons activate interneurons, synapses on 2nd order neurons
innervates motor neurons in ventral horn of gray matter
Causes inhibition of motor neurons innervating ipsilateral extensor
excitation of motor neurons innervating ipsilateral flexor (contracts)
causes withdrawal
describe flexion withdrawal reflex - cross extensor reflex
when withdrawal = weight must shift to other leg
motor afferents = cross midline to anterolateral and do opposite
excitation of motor neurons innervating contralateral extensor
Inhibition of motor neurons innervating contralateral flexor
what does magnitude of withdrawal reflex depend on
magnitude of stimulus
more painful = bigger withdrawal
describe irradiation
A>b>c = pain input bigger for a and less as go to c
recruitment of interneurons drives increased withdrawal with increased pain, more aps = more drives motor neurons
Increase in rate and magnitude of withdrawal response with increased stimulus strength
describe afterdischarge
Response maintained after stimulus termination
feedback loops in spinal cord
keep reflex going
ppl withdrawal = tend not to reextend
describe polysynaptic - properties of withdrawal reflex
Interneurons between sensory input and motor output
describe ipsilateral - properties of withdrawal reflex
Flexor muscle contraction Extensor muscle relaxation
describe contralateral - properties of withdrawal reflex
Flexor muscle relaxation
Extensor muscle contraction (cross extensor reflex)
describe stretch reflex
controls muscle length or involves lengthening of muscles
monosynaptic - primary
polysynaptic - secondary
describe monosynaptic stretch reflex - knee jerk
little hammer stretches muscles
stretch extensor muscle - tap on tendon = pulls extensor muscle and activates stretch receptors (cell bodies in dorsal root ganglion)
goes up ipsilateral dorsal columns and tells brain muscle length is changing
also branches into spinal cord and synapses and produces motor response = excitation of motor neurons innervating ipsilateral extensor
polysynaptic = interneuron and inhibition of motor neurons innervating ipsilateral flexor = leg kicks
what asses muscle tone
stretch reflex - knee jerk
ability of muscles to resist being stretched = they pull back
Patient needs to be conscious
if tone gone or too big = indication of porbelm with cns pathways coming down spinal cord
name the 2 kinds of stretch receptors = proprioceptive receptors
muscle spindle
golgi tendon organ
describe golgi tendon organ
located in tendons
in series = whatever force muscle generates
golgi tendon organ feels force and reports to cns - in tendons = attach muscle to bone
Measures muscle tension
describe muscle spindle
in parallel with extrafusal muscle
has stretch receptor and intrafusal muscle fiber
Activated by during stretch reflex and sends ap to spinal cord
stretch receptor = in middle, located at each end of part of stretch receptor that measures muscle length
intrafusal muscle fiber= activated by gamma motor neurons, regulates stretch receptor
measures muscle length - embedded in muscle - however long muscle is when contracts or relaxes = stretch receptor follows same length
extrafusal muscle fiber - activated by alpha motor neurons = causes you to move= generate force, causes contraction of muscle and movement, sits around muscle spindle
describe muscle spindles
afferents - ia and ii = 2 types of afferents come out of muscle spindles
gamma motor axons = come in and innervate both sides of intrafusal muscle fiber
describe response of ia and ii afferents
Ia = primary
nuclear bag fibers = rapidly adapting indicates change in sensory input = when muscle length is changing
when stretch reflex = mediates it, only picks it up and communicates it
ii secondar
nuclear chain fibers
communicates static changes in muscle legth
non adapting slower to respond, static steady state muscle length
describe ia primary
signal dynamic changes in muscle length and some static changes
describe ii secondary
signal static muscle length
what can muscle spindles do
lose sensitivy
describe muscle spindle during extension
Muscles lengthen
feels lengthening of muscle and increases aps and tells cns muscle is longer
increase in muscle spindle afferent activity
describe muscle spindle during voluntary flexion
alpha motor neuron activity muscles shorten
muscle spindle collapses = sensitivity reduced
mostly work when stretched - when contracted = does not work, gamma neurons come to rescue
what do gamma motor neurons do
maintain muscle spindle sensitivity
how does gamma motor neurons maintain muscle spindle sensitivity
causes intrafusal fibers contract and muscle spindle is stretched - stretches them out, maintains muscle spindle sensitivity
alpha gamma coactivation
describe alpha gamma coactivation
descending pathways come down spinal cord and activate both alpha and gamma
Alpha = extrafusal muscle contraction and shortening
gamma = intrafusal muscle activation and maintains spindle sensitivity
change in length activates muscle spindle
describe properties of stretch reflex- 3
Resists changes in muscle length (sets muscle tone)
Mono- and polysynaptic components
Feedback from muscle spindles
describe properties of muscles spindles - 6
1) Reports muscle length.
2) In parallel with extrafusal muscle fibers (does not contribute to the force of muscle contraction).
3) Ia primary: Detects changes in muscle length and some static length (nuclear bag fibers).
4) II secondary: Detects static length (nuclear chain fibers).
5) Intrafusal fibers: Maintain muscle spindle sensitivity.
6) Alpha-gamma coactivation
describe inverse stretch reflexes
controls muscle tension
what does golgi tendon organ respond to
tension
describe golgi tendon organ - for inverse stretch reflex
in series with muscle
passive stretch = might activate a few aps
fully contracting muscle = much force, many aps, lots of tension, active contraction of extrafusal muscle fibers
active contraction of muscle produces more tension than stretching
collagen fibers pinched inside golgi tendon organ = tough fibers, in between = free nerve endings = pinch free nerve endings = activate mechanically gated ion channels
describe inverse stretch reflex pathway
Activation of golgi tendon organ via 1b afferents, goes up ipsilateral dorsal columns
increased tension in extensor muscle = increased afferent activity from golgi tendon organ = branches in gray matter and interneurons
Inhibition of motor neurons innervating ipsilateral extensor - both alpha and gamma
excitation of motor neurons innervating ipsilateral flexor - antagonist muscle
describe properties of golgi tendon organ
1) Reports muscle tension.
2) In series with extrafusal muscle fibers
3) Ib afferents
4) Underlies inverse stretch reflex (polysynaptic)
