Muscular System

Question 1

What are the three types of muscular tissue in the body?

Answer 1

• Cardiac
• Smooth
• Skeletal

Question 2

Describe skeletal muscle.

Answer 2

• striated or voluntary muscle
• skeletal muscle contractions can be voluntarily controlled

Question 3

Describe cardiac muscle.

Answer 3

• composes the bulk of the heart
• muscle fibers are branched
• dark bands called intercalated disks
• interconnections of cardiac muscle fibers allow the hear to contract efficiently as a unit

Question 4

Describe smooth muscle.

Answer 4

• involuntary, smooth, or visceral muscle
• lacks striations
• found in the walls of hollow structures, such as digestive tract, blood vessels, etc.
• contractions are not voluntary

Question 5

Describe the structure of skeletal muscle.

Answer 5

• striated
• connective tissue forms ‘wrappers’ around each muscle fiber, around fascicles (groups) of muscle fibers, and around the entire muscle
• most skeletal muscles extend from on bone across a joint to another bone

Question 6

What are the three regions of a skeletal muscle?

Answer 6

• Origin - attachment to the bone that remains relatively stationary or fixed when movement at the joint occurs
• Insertion - point of attachment to the bone that moves when a muscle contracts
• Body - main part of the muscle

Question 7

How are muscles attached to bones?

Answer 7

Muscles are attached to bone by tendons - strong cords or sheets of fibrous connective tissues that extend from the muscle organ

Question 8

What is synovial fluid?

Answer 8

Synovial fluid, also known as joint fluid, is a thick liquid located between your joints. The fluid cushions and protects the ends of bones and reduces friction during movement.

Question 9

What is a bursae?

Answer 9

Small synovial-lined sacs containing small amounts of synovial fluid; located between some tendons and underlying bones.

Question 10

What are the two main types of myofiliments?

Answer 10

• Thick myofilaments (contain myosin)
• Thin myofilaments (contain actin)

Question 11

What is a sarcomere?

Answer 11

A sarcomere is the basic contractile unit of muscle fiber (separated from each other by dark bands called Z-lines)

Question 12

Describe the sliding filament model.

Answer 12

• Thick and thin myofilaments slide past each other to contract
• contraction requires calcium and energy-rich ATP molecules.

Question 13

What is the prime mover?

Answer 13

The main muscle responsible for producing a given movement.

Question 14

What is the synergist?

Answer 14

Muscle that helps the prime mover produce a given movement.

Question 15

What is the antagonist?

Answer 15

Muscle that opposes the action of a prime mover in any given movement.

Question 16

What are the three functions of skeletal muscle?

Answer 16

• Movement - muscles produce movement by pulling on bones as a muscle contracts
• Posture - a continuous low-strength muscle contraction called tonic contraction (muscle tone) enables us to maintain body position
• Heat production - contraction of muscle fibers produces most of the heat required to maintain normal body temperature

Question 17

What is fatigue as it relates to muscle?

Answer 17

• Reduced strength of muscle contraction caused by repeated muscle stimulation without adequate periods of rest.

Question 18

What is lactic acid?

Answer 18

Produced by contractions in the absence of adequate oxygen. Contributes to muscle soreness.

Question 19

What is oxygen debt?

Answer 19

Describes the extra oxygen needed to support the metabolic effort required to burn excess lactic acid (laboured breathing after strenuous exercise is required to “pay the debt”).

Question 20

What is a motor unit?

Answer 20

A motor neuron plus all the muscle fibers it controls.

Question 21

What is a motor neuron?

Answer 21

A nerve cell that transmits an impulse to a muscle causing contraction.

Question 22

What is the neuromuscular junction (NMJ)?

Answer 22

• The place where a motor neuron communicates with a muscle fiber
• chemicals called neurotransmitters cross the NMJ to trigger muscle contraction
• Acetylcholine (ACh) is the neurotransmitter operating at each NMJ.

Question 23

What is the threshold stimulus?

Answer 23

The minimal level of stimulation required to cause a muscle fiber to contract.

Question 24

Describe the “all-or-none” response.

Answer 24

If stimulated by a threshold stimulus, a muscle fiber will contract completely; if the muscle fiber does not reach the threshold stimulus, it will not contract (different motor units responding to different threshold stimuli permit a muscle as a whole to execute contractions of graded force).

Question 25

What are the four major types of skeletal muscle contractions?

Answer 25

• Twitch contractions
• Tetanic contractions
• Isotonic contractions
• Isometric contractions

Question 26

What is a twitch contraction?

Answer 26

Laboratory phenomena, not normal muscle activity; each is a single contraction of muscle fibers caused by a single threshold stimulus.

Question 27

What is a tetanic contraction?

Answer 27

Sustained muscular contractions caused by threshold stimuli hitting a muscle in rapid succession.

Question 28

What are the two types of isotonic contractions?

Answer 28

• Concentric contraction - causes a muscle to shorten, so that the insertion end of the muscle moves toward the point of origin.
• Eccentric contraction - causes a muscle to lengthen under tension, this moving the insertion away from the origin.

Question 29

What are isometric contractions?

Answer 29

• Do NOT produce movement; the muscle as a whole does not shorten; although no movement occurs, tension within the muscle increases.

Question 30

What is disuse atrophy?

Answer 30

Breakdown of muscle due to prolonged inactivity.

Question 31

What is hypertrophy?

Answer 31

Increase in muscle size, due to regular exercise.

Question 32

What is strength training?

Answer 32

Exercise involving contraction of muscles against heavy resistance; increases the numbers of myofilaments in each muscle fiber.

Question 33

What is endurance training?

Answer 33

Exercise that increases a muscle’s ability to sustain moderate exercise over a long period; sometimes called aerobic training.

Question 34

What are the four angular movements produced by skeletal muscle contractions?

Answer 34

• Flexion - decreasing an angle
• Extension - increasing an angle
• Abduction - moving away from the midline of the body
• Adduction - moving towards the midline of the body

Question 35

What are the three circular movements produced by skeletal muscle contractions?

Answer 35

• Rotation - moving around an axis
• Circumduction - moving the distal end of a part in a circle
• Supination and pronation - hand positions that result from rotation of the forearm

Question 36

What are the two special movements produced by skeletal muscle contractions?

Answer 36

• Dorsiflexion and plantar flexion - foot movements (upward and downward ankle movement)
• Inversion and eversion - foot movements (sideways)