Exam 4, Chapter 13b - Somatic Motor (Part 2)

Question 1

1. Receptor
2. Sensory neuron
3. Integration center
4. Motor neuron
5. Effector

Answer 1

Reflex Arcs

Five Components of

Question 2

site of stimulus

Answer 2

Reflex Arcs

Receptor

Question 3

transmits the afferent impulse to the CNS

Answer 3

Reflex Arcs

Sensory neuron

Question 4

either monosynaptic or polysynaptic region within the CNS

Answer 4

Reflex Arcs

Integration center

Question 5

conducts efferent impulses from the integration center to an effector

Answer 5

Reflex Arcs

Motor Neuron

Question 6

muscle fiber or gland that responds to the efferent impulse

Answer 6

Reflex Arcs

Effector

Question 7

For skeletal muscles to perform in a normal coordinated fashion, the nervous system needs
___ types of information:

Answer 7

Reflex Component Anatomy

2

Question 8

Length of the muscle: provided by the

Answer 8

Reflex Component Anatomy

muscle spindles

Question 9

Amount of tension in the muscles: provided by the

Answer 9

Reflex Component Anatomy

Golgi tendon organs (proprioceptors)

Question 10

Composed of modified muscle fibers called intrafusal muscle fibers that are wrapped in a
connective tissue capsule (the spindle = fusal) and serve as receptive surfaces.

Answer 10

Muscle Spindles

Question 11

Only the ends of the ___ are contractile & are innervated by gamma (gamma) efferent fibers

Answer 11

Muscle Spindles

Question 12

Contractile skeletal muscle fibers are extrafusal fibers & are innervated by alpha (α) efferent fibers

Answer 12

Muscle Spindles

Question 13

signals from the brain cause the muscle spindles to be more taut (greater force of extrafusal contraction can be anticipated; e.g. high vertical jump) or to be
less taut, as the situation demands

Answer 13

Operation of the Muscle Spindles

Gamma / efferent

Question 14

Stretching the muscles also activates the ____, which then sends afferent impulses to the spinal cord

Answer 14

Muscle spindles

Question 15

The greater the rate and degree of stretch, the ___ the impulse frequency

Answer 15

Muscle spindles

higher

Question 16

Stretch Reflex
Patellar Reflex Example
Tapping the patellar tendon quickly - stretches the quadriceps and starts the reflex action

Answer 16

yes

Question 17

Stretch Reflex
Patellar Reflex Example
The ___ is activated and sends afferent impulses to the spinal cord (dorsal horn)
-Two components!

Answer 17

muscle spindle

Question 18

synapses with an alpha (alpha) motor neuron in the ipsilateral
ventral horn causing immediate contraction of the quadriceps, with resultant knee extension

Answer 18

Monosynaptic component

Question 19

the muscle spindle afferent simultaneously synapses with an inhibitory interneuron which subsequently synapses with the ventral horn α-motor neuron for the antagonist muscle (in this case, the hamstrings)

Answer 19

Polysynaptic component

Question 20

While the quadriceps muscles are contracting, the hamstrings are inhibited and unable to resist the contraction.

Answer 20

Net result: Reciprocal Inhibition:

Question 21

Stretch Reflex and Muscle Tone
The brain sends commands to _____ neurons, effectively setting a muscle’s length (or
tone).

Answer 21

gamma motor neurons

Question 22

The stretch reflex assists in maintaining this “set point” for muscle tone, especially in
the postural muscles of the trunk

Answer 22

ex:
knees don’t buckle during squat (stretched quadriceps muscle triggers a stretch reflex, which causes the quadriceps to contract, preventing a fall)

Question 23

activate skeletal muscles

Answer 23

Somatic (voluntary) reflexes: activate skeletal muscles

Question 24

activate visceral effectors

Answer 24

Autonomic Reflexes

Question 25

smooth muscle, cardiac muscle, glands

Answer 25

Autonomic Reflexes | Effectors

Question 26

these are used as neurotransmitters

Answer 26

Autonomic Reflexes Acetylcholine Norepinephrine

Question 27

Autonomic motor endings and visceral effectors are ___ than somatic junctions

Answer 27

Autonomic Reflexes | simpler

Question 28

Visceral responses are faster?/slower? than somatic responses

Answer 28

Autonomic Reflexes | slower

Question 29

Produces the opposite effect of the stretch reflex

Answer 29

Golgi Tendon Reflex and Flexor Withdrawal

Question 30

are located in the muscle tendons and are activated during a significant increase in muscle tension (e.g.: carrying a dangerously heavy load)

Answer 30

Golgi Tendon Reflex and Flexor Withdrawal | Golgi Tendon Organs (GTO)

Question 31

Helps prevent muscles and tendons from tearing when they are subjected to a damaging stretching force

Answer 31

Golgi Tendon Reflex and Flexor Withdrawal

Question 32

-The GTO afferent travels to the dorsal horn and synapses with an inhibitory interneuron. -This interneuron synapses with the ventral horn α-motor neuron for the contracting muscle. -The GTO afferent also synapses with an excitatory interneuron. -This interneuron synapses with the ventral horn α-motor neuron for the antagonist muscle.

Answer 32

Golgi Tendon Reflex and Flexor Withdrawal

Question 33

(contracting muscle relaxes & antagonist activates)

Answer 33

Golgi Tendon Reflex and Flexor Withdrawal | Net Result: Reciprocal Activation

Question 34

-reflex is initiated by a painful stimulus (actual or perceived) that causes automatic withdrawal of the threatened body part

Answer 34

Flexor Withdrawal Reflexes

Question 35

-Polysynaptic and ipsilateral

Answer 35

Flexor Withdrawal Reflexes

Question 36

-overrides other spinal pathways and other reflexes

Answer 36

Flexor Withdrawal Reflexes | Protective

Question 37

Can be overridden by descending signals from the brain (not pulling away from a needle during a blood draw)

Answer 37

Flexor Withdrawal Reflexes | Protective

Question 38

includes the flexor withdrawal component plus The contralateral side is extended (opposite arm swing when you pull one back) THINK DISCUS

Answer 38

Crossed Extensor Reflex

Question 39

initiated by firmly/sharply stimulating the lateral aspect of the sole of the foot, moving medially at the metatarsal heads

Answer 39

Plantar reflex

Question 40

normal response is downward flexion of all toes (including the hallux)

Answer 40

Plantar Reflex

Question 41

abnormal plantar reflex where the hallux extends and pedal digits 2-5 fan laterally

Answer 41

Babinski's sign

Question 42

Indirectly tests for corticospinal tract functioning (Indicates an UMN lesion)

Answer 42

Babinski's sign