Spinal Cord Reflexes

Question 1

What are the 2 types of reflexes? What are the 2 subcategories of each?

Answer 1

SPINAL or CRANIAL

somatic (skeletal) or autonomic (visceral)

Question 2

What is the integrating center for spinal reflexes?

Answer 2

The grey matter of spinal cord

Question 3

What is the reflex arc?

Answer 3

a pathway followed by nerve impulses that produce reflex

Question 4

(SN) What are the 5 components of a reflex arc?

Answer 4

1.) receptor
2.) sensory neuron
3.) integrating center
4.) motor neuron
5.) effector

Question 5

(SN) What does the receptor do?

Answer 5

(SN) sensory receptor (RESPONDS to a STIMULUS by producing a generator or receptor POTENTIAL)

Question 6

(SN) What does the sensory neuron do?

Answer 6

Axon CONDUCTS IMPULSES from receptor to integrating center

Question 7

(SN) What does the integrating center do?

Answer 7

GREY MATTER

RELAYS impulses from SENSORY –> MOTOR NEURONS

Question 8

(SN) What does the motor neuron do?

Answer 8

axon conducts impulses from INT. CENTER –> EFFECTOR (out of CNS)

Question 9

(SN) What does the effector do?

Answer 9

skeletal muscle or gland that RESPONDS to motor nerve impulses

Question 10

What is the difference between monosynaptic and polysynaptic?

Answer 10

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.

Question 11

What is the innervation referring to the contraction of one muscle (agonist) and relaxation of its antagonist muscle(s)?

Answer 11

reciprocal innervation

Question 12

What are the 4 somatic spinal reflexes?

Answer 12

1.) stretch
2.) tendon
3.) flexor
4.) crossed extensor

Question 13

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?

Answer 13

Stretch reflex

Muscle contracts when stretched to prevent injury

monosynaptic

Ipsilateral

Biceps reflex, triceps reflex, brachioradialis

Question 14

Stretch reflex pathway.

Answer 14

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)

Question 15

After the muscle is contracted, what is the pathway for the antagonist muscles?

Does this happen through mono or polysynaptic interneuron?

Answer 15

1.) inhibitory interneurons and motor neurons travel to the antagonist muscle to relax it.

Polysynaptic (reciprocal)

Question 16

What else can stretch reflex maintain?

Answer 16

posture

Question 17

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?

Answer 17

Tendon reflex
polysynaptic
ipsilateral
reciprocal innervation (polysynaptic)

Question 18

Pathway of tendon reflex

Answer 18

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)

Question 19

Which reflex is a protective reflex moves a limb to avoid pain? What does it result in?

ispilateral?

mono or polysynaptic innervation?

Answer 19

flexor (withdrawal) reflex

ispilateral

contraction of flexor muscles to move a limb to avoid injury or pain

poly

Question 20

Flexor (withdrawal) reflex pathway

Answer 20

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

Question 21

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?

Answer 21

crossed extensor reflex

No, contralateral

Question 22

Pathway for crossed extensor reflex

Answer 22

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)

Question 23

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?

Answer 23

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.

Question 24

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?

Answer 24

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.

Question 25

When interneurons are ascending and descending to different SC segments this is called what? Which types of reflexes is this present in?

Answer 25

intersegmental reflex arch

Flexor (withdrawal) reflex