Chapter 9 Part 1

Question 1

Function of Muscle Tissue

Answer 1

Movement, Maintaining posture, Stabilizing joints, Heat production

Question 2

Characteristic properties:

Answer 2

Excitability (irritability) - responds to stimuli
Contractility - can shorten
Extensibility - can lengthen
Elasticity - returns to its original length after stretching

Question 3

Skeletal Muscle Fiber Characteristics

Answer 3

1. It is multinucleated.
2. It contains many mitochondria.
3. It has specific terms for some of the intracellular structures:
   Sarcolemma = Plasma membrane
   Sarcoplasm = Cytoplasm
   Sarcoplasmic reticulum = Smooth ER
4. Transverse tubules- extension of sarcolemma
5. Myofibirils and sarcomeres

Question 4

Myofibrils

Answer 4

Give skeletal and cardiac muscle their characteristic striated appearance.

• Actin (thin)
• Myosin (thick)

Question 5

Striations

Answer 5

actin and myosin arrangement

Question 6

A band

Answer 6

has both actin and myosin, forming a dark band (anisotropic).

Question 7

I band

Answer 7

contains only thin actin filaments. Much light gets through so it looks brighter.

Question 8

Z disc

Answer 8

located in the center of the I band. Z discs anchor the actin in place.

Question 9

H zone

Answer 9

brighter region in center of the A band containing only myosin filaments.

Question 10

M line

Answer 10

line in the center of the H zone formed by discs in the center of the myosin filaments.

Question 11

Sarcomere

Answer 11

the functional unit of contraction.

Extends from one Z disc to the next.

Question 12

Sarcoplasmic reticulum

Answer 12

the smooth ER of muscle cell

Question 13

Transverse tubules

Answer 13

tubular continuations of the sarcolemma that run through the cell like tunnels.

Question 14

Triads

Answer 14

two terminal cisterna and a T tubule cluster together to form a triad.

Question 15

Myosin

Answer 15

thick myofilaments that have globular heads extending to either side.
Cross bridges form between the myosin heads and the actin.
Has binding sites for actin and ATP.

Question 16

Actin

Answer 16

thin myofilaments that interact

with the myosin heads

Question 17

Motor neurons

Answer 17

somatic efferent neurons.

Question 18

Motor end plate

Answer 18

the region of the sarcolemma that lies directly under the terminal portion of the axon.

Question 19

Neuromuscular junction

Answer 19

the junction of an axon terminal with the motor end plate.

Question 20

Acetylcholinesterase

Answer 20

the enzyme that breaks down ACh is in the cleft to terminate signaling by ACh.

Question 21

Tension

Answer 21

the force exerted on an object by a contracting muscle.

Question 22

Load

Answer 22

the force exerted on the muscle by an object (usually its weight).

Question 23

Twitch

Answer 23

the mechanical response of a muscle fiber to a single action potential.

Question 24

Isotonic

Answer 24

contraction that causes movement. The tension of the muscle remains constant, and the muscle changes length. (Isotonic = constant tension)

Question 25

Concentric contractions

Answer 25

muscle shortens as it contracts. Most familiar.

Question 26

Eccentric contractions

Answer 26

muscle lengthens as it contracts. Example: squatting, where the quadriceps femoris group controls descent.

Question 27

Isometric

Answer 27

contraction to support a load in a constant position (like for posture) or against a load too great for the muscle to move. The length of the muscle remains constant, even though the tension is changing. (Isometric = constant length)