Motor Functions of Spinal Cord and Reflexes Flashcards
what is the name of the reflex that happens when you move your hand away very quickly when you put your hand on a hot burner
withdrawal of flexion reflex
what are the 3 neuronal organizations of the spinal cord
sensory neurons
motor neurons
interneurons
describe sensory neurons (ganglion, where does it transmits signals to, where is the synapse and what does it elicit)
-dorsal root ganglion
-transmits signals to higher centers
-synapse at the spinal cord level to elicit motor reflexes
describe motor neurons (horn, what do they innervate, what are the 2 types of MN and what does they excite)
-anterior horn,
-directly innervate skeletal m. fibers
-alpha MNs (A-alpha axons) excite extrafusal muscle fibers (motor units), muscle contraction
-Gamma MNs (A-gamma axons) excite intrafusal fibers (muscle sensory receptors)
describe interneurons (they have connections with what, what can they do)
-local neurons that have connections with sensory and motor neurons
-they can be inhibitory or excitatory
what are sensory receptors of the muscle and what are they stimulated by
mechanoreceptors and they are stimulated by mechanical displacement of the muscle
describe muscle spindles (where are they, what do they sense)
-distributed throughout the muscle belly (midportion of intrafusal fibers)
-sense muscle length (stretched, relaxed, contracted) and rate of change of length
what are sensory signals transmitted through in muscle spindles
1a (primary sensory endings) fibers
2 (secondary sensory endings) fibers
describe golgi tendon organs (where are they, what do they sense and what are sensory signals transmitted thru)
-are located in the muscle tendon
-sense tendon tension and rate of change of tension
-sensory signals are transmitted thru 1b fibers
sensory receptors within the body of a muscle that primarily detect changes in the length of a m
muscle spindles
what is the function of a muscle spindle
to provide info on the position of body parts (proprioception)
describe primary sensory endings of the muscle spindle (type 1a fibers) (where do they terminate, respond to what)
-terminate on nuclear bad and nuclear chain fibers
-respond to the rate of changes in muscle length (dynamic) and to the degree of stretch of the muscle (static)
describe secondary sensory endings of the muscle spindle (type 2 fibers) (where do they terminate, respond to what)
-terminate on nuclear chain fibers
-respond mostly to the degree of stretch of the muscle (static response)
what is alpha-gamma coactivation
causes the tension on the muscle spindles to be maintained as the muscle shortens; thus sensitivity to stretch is maintained
what needs to happen to send signals to the CNS
muscle spindles must be stretched
for the biceps curl example:
A) elbow is ___ = ____ and ____ fibers are ____= muscle spindles are responding by sending signals to the ____
elbow is extended = extrafusal and intrafusal fibers are stretched = muscle spindles are responding by sending signals to the CNS
for the biceps curl example:
B) during biceps curl, ____ are activated to contract ____ –> muscle spindles get ___ and can no longer send signals to the___
during biceps curl, alpha motorneurons (Mns) are activated to contract muscle fibers –> muscle spindles get shorten and can no longer send signals to the CNS
for the biceps curl example:
C) to avoid the B situation, ___ are activated to contract ____ fibers –> muscle spindles get ____ and respond by sending signals to the ___
C) to avoid the B situation, gamma are activated to contract intrafusal fibers –> muscle spindles get stretched and respond by sending signals to the CNS
what are encapsulated sensory receptor through which muscle tendon fibers pass
golgi tendon organs
golgi tendon organ are stimulated when muscle fibers are
tensed by the contraction or the stretching of the muscle (sensitive to muscle tension)
GTOs react intensively (static and dynamic responses) when
when muscle tension suddenly increase (dynamic) or settles down rapidly to a lower level of steady state tension (static)
what are GTO signals transmitted thru
Ib fibers
Ib fibers in GTO inhibit indirectly (through interneurons) what and to allow what
alpha motor neuron at the spinal cord to allow the muscle to relax and thus to relieve the tension on the tendon
what are named mechanism by which sensory impulses are automatically converted into a motor effect
spinal cord reflexes
what are the reactions in the spinal cord reflexes and what are they controlled by
involuntary and rapid reactions controlled by the spinal cord integration centers
what can spinal cord reflexes do to the body
protective mechanism to the body (e.g prevent an over stretch (or contraction) of the muscle, withdrawal from a painful stimulus…)
what is a stretch reflex
sudden stretch of the muscle activates the muscle spindles (of the same muscle)
what are the associated fibers to the stretch reflex and what do they transmit
associated sensory fibers (Ia &II) transmit impulses at the spinal cord level
in stretch reflex what fibers synapse directly with what and causes what
type Ia and II fibers synapse directly with alpha motor neurons causing the muscle to contract
the stretch reflex is a ____ reflex because of the connection between the sensory and the motor nerve fiber
monosynaptic
describe the neuronal circuits of the stretch reflex in a patellar reflex (what happens, what is the function, what are the endings for the afferent signals, where is the synapse, what results, what is the innervation, what send the efferent signals)
-striking the patellar tendon elicits a sudden kicking movement of the lower leg
-function of the stretch reflex is to oppose sudden changes in muscle length (stretching)
-afferent signal via primary (Ia) and secondary (II) sensory endings
-synapse in spinal cord with alpha motor neurons
-muscle contraction results to oppose stretch
-reciprocal innervation (Collateral 1a synapses inhibitory interneurons)
-inhibitory interneuron sends efferent signal to antagonist (relaxation of antagonist m.)
what is the function of Golgi tendon reflex
relieve excess tension on the tendon
contracting of a muscle creates a ___ on the ___ attached to the same muscle and thus ___ the golgi tendon organs
tension
tendon
activates
golgi tendon sensory fibers (1b) transmits ____ at a ____ _____ to ____
impulses at a higher frequency to spinal cord
in the golgi tendon reflex:
sensory neurons synapse with what, that inhibit what, and causes what
sensory neurons synapse with what, that excite what, and causes what
sensory neurons synapse with inhibitory interneurons that inhibit alpha motor neurons and cause the contracted muscle to relax
sensory neurons synapse with excitatory interneurons that excite alpha motor neurons of antagonist muscles and cause the muscle to relax
what are the five steps of golgi tendon reflex
1- increased tension stimulates sensory receptor (tendon)
2-sensory neuron excited
3-within integrating center (sc), sensory neuron activates inhibitory interneuron
4-motor neuron inhibited
5-effector (muscle attached to same tendon) relaxes and relieves excess tension
extrafusal fibers are activated by which types of motor neurons
alpha motor neurons
what is the flexion reflex
is initiated by a painful stimulus that causes automatic withdrawal of the threatened body part
in flexion reflex; sensory neurons synapse with interneurons that…
-excite motor neurons of the flexor muscle (e.g biceps) and cause muscle to contract
-inhibit motor neurons of the extensor muscle (e.g triceps) and cause the muscle to relax
