Reflexes- Definitions Flashcards
Monosynaptic/Deep Tendon/Myotactic Reflex
afferent and efferent limbs are directly connected (one single synapse)
Polysynaptic Reflex
Afferent and Efferent limbs are connected by one or more interneuron
Reflex Arc Syndrome
Sensory receptor (Spindle/golgi tendon)
Afferent Neuron
Synapse on efferent (LMN neuron)
Muscle Contraction
Types of Stretch Reflexes
Deep Tendon Reflex
Golgi Tendon Reflex (inverse myotactic)
Flexion Crossed Extension Reflex
Afferent Limbs
Spindle –> 1a
Golgi Tendon –> 1b fibers
Efferent Limbs
A-gamma –> Intrafusal fibers
A-Alpha –> extrafusal fibers
Basic Reflex Arc
Is in response to passive muscle stretching
what fibers directly stimulate alpha motor fibers to contract the stretched muscle?
1a- Fibers (spindle)
1a fibers also stimulate inhibitory interneurons that eventually inhibit what neurons on the antagonist muscle?
alpha motor neurons
What are gamma motor neurons responsible for?
contracting the ends of the muscle spindle to keep its length identical to the muscle fibers in an effort to maintain monitoring of the muscle length at all times
what is the location and function of the golgi tendon?
located in series between the tendon and extrafusal fibers which are sensitive to tension
what fiber innervates the golgi tendon?
single 1b axon which is large, myelinated and with high velocity
what happens to the 1b fiber once it enters the tendon organ?
loses its myelination once it enters the tendon organ and intertwines the collagen chains
does contraction of the muscle increase or decrease 1b-axon firing?
Increase
what physiological response does increasing 1b axon firing have?
increase inhibition on the alpha motor neuron
what does having inhibition on the alpha motor neuron do?
ensures even distribution of tension and contraction as well as avoiding excessive contraction to the point of damage (known as the inverse myotactic reflex)
What is the primary function of the golgi tendon?
protection (increased tension will increase inhibition on contraction to avoid excessive contraction that can lead to damage)
posture ( via the patellar tendon and the quadriceps muscle)
what is the flexion or withdraw reflex?
in response to painful stimuli, causing rapid flexion as a protective mechanism pain afferents (a delta and c fibers) will stimulate excitatory interneurons that synapse on alpha motor neurons to flex the necessary muscle.
what is the flexion crossed extension reflex?
Flexion reflex is associated with the flexion crossed extension reflex in the contralateral limb
this will support the contralateral leg to maintain balance if the flexion reflex causes the ipsilateral leg to lift when you step on a pain.
so you inhibit the ipsilateral flexor stimulation and stimulate the contralateral flexor
what is the Babinski sign?
dorsiflexion of the big toe, often associated by fanning of the other toes.
why is a positive babinski sign in a newborn normal?
newborns have immature corticospinal tract
What does a positive babinski sign indicate?
UMN damage to spinal cord or brain disease to the corticospinal tract
If a patient exhibits hyperflexia what type of lesion is this associated with?
UMN lesion in the cortex or somewhere in the corticospinal tract (remember after spinal shock)
what is spinal shock?
acute damage to the spinal cord causing immediate areflexia caudal to injury; reflexes return in weeks
what is the lesion associated with hyporeflexia?
LMN reflex, NMJ muscle disease, sensory loss or peripheral nerve lesion
what is an example of the flexion reflex or “withdrawal reflex”?
pulling the hand away from a hot surface
