Reflexes Flashcards
Which neurons are the largest in the ventral horn?
The Alpha motor neurons.
What function do the Alpha motor neurons have?
Function to innervate typical skeletal muscle fibers (Extrafusal fibers) which cause contraction and movement of muscles.
What function do the smaller gamma motor neurons have?
The gamma motor neurons innervate the contractile portions of intrafusal fibers of muscle spindles.
What is an intrasegmental reflex?
Involves or affects only a single spinal cord level.
What is an intersegmental reflex?
Involves or affects numerous spinal cord levels.
What is a suprasegmental reflex?
Influenced by neurons residing in the cerebral hemisphere or brainstem and through their connections influence reflex activity occuring at the spinal cord level.
What are the receptors involved in the muscle stretch reflex?
Muscle spindles which are embedded in the muscle.
What stimulus triggers sensory endings on the intrafusal fibers of the muscle to fire?
Muscle stretching causes firing of these nerves.
Describe the reciprocal inhibition reflex.
The muscle spindle acts as a receptor at the end of an Ia fiber.
Each central process then bifurcates, one branch performs excitation and the other inhibits the antagonist muscle.
Stimulation of a GTO receptor in a tendon will result in what action?
It will shut the muscle down in an attempt to limit the muscle from over contracting and causing damage to itself.
This is known as autgenic inhibition.
What is the flexor reflex (Withdrawl reflex, nociceptive reflex)?
This is a withdrawl reflex in association with pain within an affected limb.
What type of nerve receptors are in the flexor reflex?
Alpha Delta or two unmyelinated C fibers.
What is the pathway for the nerves in the Flexor reflex?
Central process enters the Dorsolateral tract of Lissauer where it branches into short ascending and descending branches synapsing with interneurns.
Excitatory interneurons synapse with alpha motor neurons that stimulate the withdrawl of limb through flexor muscles.
Inhibitory neurons synapse with alpha motor neurons and innervate the extensors (antagonists) causing thm to relax and aid in the pulling away.
