2-10 The Control Of Movement

Front 1

Objective

Distinguish among the three types of vertebrate muscles.

Back 1

Smooth muscles, which control the digestive system and other organs

Skeletal or striated muscles, which control movement of the body in relation to the environment

Cardiac muscles (the heart muscles), which have properties intermediate between those of smooth and skeletal muscles

Front 2

Objective

Explain why antagonistic muscles are needed.

Back 2

Moving a leg or arm in two directions requires opposing sets of muscles, called antagonistic muscles. An arm, for example, has a flexor muscles that flexes or raises it and an extensor muscle that extends or straightens it. Walking, clapping hands, and other coordinated sequences require a regular alternation between contraction of one set of muscles and contraction of another.

Front 3

Objective

Indicate when fast-twitch and slow-twitch muscles are needed.

Back 3

Our muscle types range from fast-twitch fibers that produce fast contractions but fatigue rapidly to slow-twitch fibers that produce less vigorous contractions without fatiguing. We rely on our slow-twitch and intermediate fibers for non-strenuous activities. For example, you could talk for hours without fatiguing your lip muscles. You could probably walk for hours too. But if you run up a steep hill at full speed, you will have to switch to fast-twitch fibers, which will fatigue rapidly.

Front 4

Objective

Describe the role of muscle spindles in the knee-jerk reflex.

Back 4

See study guide.

Front 5

Objective

Discuss the extent to which a movement like walking is voluntary.

Back 5

You might think of walking as being purely voluntary, but even that example includes involuntary components. When you walk, you automatically compensate for the bumps and irregularities in the road. You probably also swing your arms automatically as an involuntary consequence of walking.

Front 6

Objective

Identify three reflexes that are present in infants but not in adults.

Back 6

Grasp Reflex: If you place an object firmly in an infant’s hand, the infant will reflexively grasp it tightly.

Babinski Reflex: If you stroke the sole of the foot, the infant will reflexively extend the big toe and fan the others.

Rooting Reflex: If you touch an infant’s cheek, the head will turn toward the stimulated cheek, and the infant will begin to suck. It is not a pure reflex, as its intensity depends on the infant’s arousal and hunger levels.

Front 7

smooth muscle

Back 7

Muscles that control the digestive system and other organs

Front 8

striated (skeletal) muscle

Back 8

Muscles that control movement of the body in relation to the environment

Front 9

cardiac muscle

Back 9

Heart muscles; have properties intermediate between those of smooth and skeletal muscles

Front 10

neuromuscular junction

Back 10

A synapse where a motor neuron axon meets a muscle fiber

Front 11

antagonistic muscle

Back 11

Opposing sets of muscles

Front 12

flexor

Back 12

Muscle that flexes or raises a limb

Front 13

extensor

Back 13

Muscle that extends or straightens a limb

Front 14

myasthenia gravis

Back 14

An autoimmune disease, in which the immune system forms antibodies that attack the individual’s own body; more specifically, the immune system attacks the acetylcholine receptors at neuromuscular junctions

Front 15

fast-twitch fibers

Back 15

Muscle type that produces fast contractions but fatigues rapidly

Front 16

slow-twitch fibers

Back 16

Muscle type that produces less vigorous contractions without fatiguing

Front 17

aerobic

Back 17

Use of air (specifically oxygen) during movements; slow-twitch fibers do not fatigue because they are aerobic

Front 18

anaerobic

Back 18

Using reactions that do not require oxygen at the time, although oxygen is eventually necessary for recovery; vigorous use of fast-twitch fibers results in fatigue because of the anaerobic process

Front 19

proprioceptor

Back 19

A receptor that detects the position or movement of a part of the body

Front 20

stretch reflex

Back 20

Reflex that occurs when a muscle is stretched (spinal cord sends reflexive signals as a result of the stretch)

Front 21

muscle spindle

Back 21

A proprioceptor parallel to the muscle that responds to a stretch; whenever the muscle spindle is stretched, its sensory nerve sends a message to a motor neuron in the spinal cord, which in turn sends a message back to the muscles surrounding the spindle, causing a contraction

Front 22

golgi tendon organ

Back 22

A proprioceptor that responds to increases in muscle tension; located in the tendons at opposite ends of a muscle and acts as a brake against an excessively vigorous contraction

Front 23

reflex

Back 23

Consistent automatic responses to stimuli

Front 24

grasp reflex

Back 24

If you place an object firmly in an infant’s hand, the infant will reflexively grasp it tightly

Front 25

babinski reflex

Back 25

If you stroke the sole of the foot, the infant will reflexively extend the big toe and fan the others

Front 26

rooting reflex

Back 26

If you touch an infant’s cheek, the head will turn toward the stimulated cheek, and the infant will begin to suck