Nervous System Control of Skeletal Muscle

Question 1

Usually have muscles on either side of a joint: ___________ such as biceps to flex and ___________ such as triceps to extend

Answer 1

flexors and extensors

Question 2

_________ pathways are efferent only

Answer 2

Motor

Question 3

___________ motor programs serve essential needs (locomotion, posture, breathing) and range from involuntary actions (withdrawal reflexes) to complex voluntary activities

Answer 3

Somatic

Question 4

One __________ can control from 3-1000 fibers, all will be in the same muscle, usually spread out

Answer 4

neuron

Question 5

A muscle fiber is usually innervated by a _________ neuron

Answer 5

single

Question 6

A ________________ consists of a motor neuron and all of the muscle fiber it controls

Answer 6

motor unit

Question 7

Muscle fiber is the same thing as muscle ______

Answer 7

cell

Question 8

A motor neuron may synapse with several fibers, but each fiber/cell only gets information from _______ neuron (in contrast to smooth muscle, which gets multiple inputs)

Answer 8

one

Question 9

At the neuromuscular junction, what ensures that that every time the motor neuron fires, the muscle cell will have an action potential and contract? (very reliable)

Answer 9

Proximity of voltage-gated Na+ channels (graded potential right next to action potential)

Question 10

During a reflex, the afferent, sensory neuron is pseudounipolar and the sends signals to an interneuron in the _____________

Answer 10

dorsal root ganglion

Question 11

During a reflex, the relay neuron, or ____________, can be either:

Answer 11

excitatory or inhibitory

Question 12

During a reflex, in an ___________ relay neuron is triggered, it will trigger an action potential in motor neuron, which causes increased muscle contraction

Answer 12

excitatory

Question 13

During a reflex, in an ___________ relay neuron in the dorsal root is triggered, Cl- channels open, Cl- rushes in, and no depolarization occurs in the motor neuron
(GABA, Gly)

Answer 13

inhibitory

Question 14

Two main types of lower motor neurons

Answer 14

Alpha and Gamma

Question 15

______ motor neurons innervate extrafusal muscle fibers to generate force for posture and movement

Answer 15

Alpha

Question 16

______ motor neurons innervate intrafusal muscle fibers (muscle spindle)

Answer 16

Gamma

Question 17

Shortening of the ______________ concurrent with shortening of the extrafusal muscle fibers enables continuous feedback via afferent sensory neurons to the spinal cord

Answer 17

muscle spindle

Question 18

The ____________ is critical for monitoring the length of the muscle as it shortens

Answer 18

muscle spindle

Question 19

Alpha and gamma motor neurons are ___________ fibers which are coactivated to finely regulate the intensity of muscle contraction

Answer 19

efferent

Question 20

Up to 50,000 in muscle
Like mini replicas of muscles
Mimic length of muscle they are sitting in
Important for relaying where your body is in space

Answer 20

Muscle spindles

Question 21

Measures stretch of a muscle

Answer 21

Muscle spindles

Question 22

If muscles are less stretched, muscle spindles will fire _____

Answer 22

less

Question 23

If muscles are more stretched, muscle spindles with fire _____

Answer 23

more

Question 24

Two different types of ___________ neurons coiled around the muscle spindle sense changes in stretch and the degree of stretch.

Answer 24

afferent

Question 25

The spindle acts through ______________ to cause contraction of stretched muscle and relaxation of antagonistic muscle.

Answer 25

reciprocal innervation

Question 26

Afferent neuron associated with Golgi tendon organ senses ___________ generated by muscle.

Answer 26

Tension

Question 27

Golgi tendon organs are activated by ___________ of the muscle, NOT passive stretch. They act in a negative feedback to regulate tension.

Answer 27

contraction

Question 28

_______________ are encapsulated afferent nerve endings located at junction of muscle and tendon in series with the extrafusal fibers. Output from each is sent via an afferent organ.

Answer 28

Golgi tendon organs

Question 29

Receptors of the Golgi tendon organs and the muscle spindle are both examples of _________ activated channels that operate in two different locations with different effects (one to prevent too much stretch, one to prevent too much tension).

Answer 29

stretch

Question 30

In a muscle stretch reflex (knee jerk), stretch sensory receptor activates excitation of motor neuron that will cause contraction in the extensor muscle and excites an ____________ interneuron that relaxes flexor muscle

Answer 30

inhibitory

Question 31

In a muscle stretch reflex, stretch sensory receptor in afferent neuron activates excitation of motor neuron that will cause contraction in a muscle and excites an ____________ interneuron that relaxes the opposing muscle

Answer 31

inhibitory

Question 32

The Golgi tendon reflex negative feedback loop limits __________ within the muscle to protect muscle and muscle-tendon junction

Answer 32

tension

Question 33

If the Golgi tendon organs of a muscle are stretched and stimulated, muscle contraction is _____________ (via the motor neuron)

Answer 33

inhibited

Question 34

In the Golgi tendon reflex, the _____________ muscle is stimulated to contract through the interaction of excitatory interneuron with the the afferent neuron

Answer 34

opposing

Question 35

The Golgi tendon reflex acts to protect muscles and tendons from damage due to excessive ________. They also play a role in equalizing the load across different parts of a muscle.

Answer 35

tension

Question 36

The Golgi tendon reflex inhibits the ___________ muscle, and activates the opposing muscle.

Answer 36

contracting

Question 37

Reflex circuitry mediates withdrawal of limb form a painful sensory stimulus (_________ reflex).

Answer 37

flexor reflex

Question 38

____________ reflex provides postural support during withdrawal of affected limb.

Answer 38

Crossed extensor reflex

Question 39

Pain input to spinal cord excites/inhibits reciprocal motor neurons on pained side of the body (causing withdrawal reflex) and on the __________ side of the body to support body weight.

Answer 39

opposite

Question 40

Why are two reflexes needed during withdrawal?

Answer 40

You can’t withdraw one leg without extending the opposite one so it can hold your weight (if you use the flexor reflex, you need to use the crossed extensor reflex too)