Spinal Cord Reflexes Flashcards
What are the 2 types of reflexes? What are the 2 subcategories of each?
SPINAL or CRANIAL
somatic (skeletal) or autonomic (visceral)
What is the integrating center for spinal reflexes?
The grey matter of spinal cord
What is the reflex arc?
a pathway followed by nerve impulses that produce reflex
(SN) What are the 5 components of a reflex arc?
1.) receptor
2.) sensory neuron
3.) integrating center
4.) motor neuron
5.) effector
(SN) What does the receptor do?
(SN) sensory receptor (RESPONDS to a STIMULUS by producing a generator or receptor POTENTIAL)
(SN) What does the sensory neuron do?
Axon CONDUCTS IMPULSES from receptor to integrating center
(SN) What does the integrating center do?
GREY MATTER
RELAYS impulses from SENSORY –> MOTOR NEURONS
(SN) What does the motor neuron do?
axon conducts impulses from INT. CENTER –> EFFECTOR (out of CNS)
(SN) What does the effector do?
skeletal muscle or gland that RESPONDS to motor nerve impulses
What is the difference between monosynaptic and polysynaptic?
When a reflex arc consists of only 1 of each (two neurons total), one sensory neuron, and one motor neuron, it is defined as monosynaptic. Monosynaptic refers to the presence of a single chemical synapse
polysynaptic reflex arcs, one or more interneurons connect afferent (sensory) and efferent (motor) signals.
What is the innervation referring to the contraction of one muscle (agonist) and relaxation of its antagonist muscle(s)?
reciprocal innervation
What are the 4 somatic spinal reflexes?
1.) stretch
2.) tendon
3.) flexor
4.) crossed extensor
What kind of reflex is a feedback mechanism that controls muscle LENGTH by causing muscle CONTRACTION?
How does it prevent injury?
Mono or polysynaptic?
Ipsilateral or bilateral?
Examples?
Stretch reflex
Muscle contracts when stretched to prevent injury
monosynaptic
Ipsilateral
Biceps reflex, triceps reflex, brachioradialis
Stretch reflex pathway.
1.) stretching stimulates SENSORY RECEPTOR (muscle spindle)
2.) excites SENSORY NEURONS
3.) INT. CENTER- sensory n. activates motor n.
4.) excites MOTOR n.
5.) EFFECTOR (same muscle) contracts and relieves the stretching (AcH is released causing contraction)
After the muscle is contracted, what is the pathway for the antagonist muscles?
Does this happen through mono or polysynaptic interneuron?
1.) inhibitory interneurons and motor neurons travel to the antagonist muscle to relax it.
Polysynaptic (reciprocal)
What else can stretch reflex maintain?
posture
What kind of reflex is a feedback mechanism that controls muscle TENSION by causing muscle RELAXATION when muscle force becomes too extreme?
Mono or polysynaptic reflex?
Ipsilateral or bilateral?
Examples?
Innervation?
Tendon reflex
polysynaptic
ipsilateral
reciprocal innervation (polysynaptic)
Pathway of tendon reflex
1.) increased tension stimulates SENSORY RECEPTOR (Golgi tendon organ-junction of muscle and tendon)
2.) excited SENSORY NEURON
3.) I.C (SC) sensory neuron activates INHIBITORY interneuron
4.) motor neuron INHIBITED (hyperpolarized)
5.) EFFECTOR (muscle attached to same tendon relaxes and relieves excess tension)
Which reflex is a protective reflex moves a limb to avoid pain? What does it result in?
ispilateral?
mono or polysynaptic innervation?
flexor (withdrawal) reflex
ispilateral
contraction of flexor muscles to move a limb to avoid injury or pain
poly
Flexor (withdrawal) reflex pathway
1.) Step on a tack stimulates SENSORY RECEPTOR (dendrites of pain-sensitive neuron)
2.) excited SENSORY NEURON
3.) IC (SC) sensory neuron activates interneurons that BRANCH to different spinal cord segments, intersegmental reflex arch
4.) MOTOR NEURONS in SEVERAL segments are excited
5.) MORE THAN 1 muscle group activated to lift the foot off of tack
Which reflex helps maintain BALANCE during the flexor reflex, causing synchronized extension of the joints of one limb and flexion of the joints in the opposite limb?
ipsilateral?
crossed extensor reflex
No, contralateral
Pathway for crossed extensor reflex
1.) SENSORY RECEPTOR (stepping on tack in right foot)
2.) SENSORY NEURON excited (senses pain in right foot)
3.) IC: SN activates SEVERAL interneurons
4.) MOTOR NEURON excited
5.) EFFECTOR (extensor muscles) CONTRACT and extend LEFT leg in order to bare weight of right foot lifting (from the flexor (withdrawal) reflex)
What does Babinski’s reflex or extensor plantar reflex test for?
What does the test involve?
What is normal? Exceptions normal or abnormal? What do these exceptions cause?
dysfunctional CORTICOSPINAL TRACT (upper motor lesion (UML))
Stroking the outside sole from heel to toe with a pointed object
downward (flexor) movement of all toes
exception: children under 1.5 years of age (incomplete myelination) & dysfunction in the corticospinal tract. Both cause upward (extensor) movement of big toe, often with fanning.
What does tapping on the calcaneal tendon (Achilles tendon) cause? What does this check? What kind of pathology could this test indicate? Where is it usually absent?
plantar flexion (Achilles reflex/ankle jerk reflex)
Checks S1 nerve root. Sciatic nerve pathology or peripheral neuropathy (reduction in ankle jerk). Disk herniation at the L5-S1 level.
When interneurons are ascending and descending to different SC segments this is called what? Which types of reflexes is this present in?
intersegmental reflex arch
Flexor (withdrawal) reflex
