Chapter 6

Question 1

muscle movement

Answer 1

voluntary - conscious control over movements.

involuntary - generally beyond our conscious control.

Question 2

3 types of movement

Answer 2

1. excitable - contract in response to chemical and/or electrical signals from other organ systems
2. contract (shorten) - all muscles have only one basic mechanism of action
3. relax - returning to their orginal length.

Question 3

3 types of muscles

Answer 3

1. skeletal - attach to skeleton and give us strength and mobility
2. cardiac - pump blood throughout the body
3. smooth muscle - walls of uterus propel the child through the birth canal.

Question 4

skeletal muscle

Answer 4

interact with the skeleton and cause bones to move (or prevent them from moving) relative to each other.

Question 5

synergistic muscles

Answer 5

work together to create the same movement

Question 6

antagonistic muscles

Answer 6

muscles that oppose each other

Question 7

origin

Answer 7

joins to a bone that remains relatively stationary.

Question 8

insertion

Answer 8

other end of the muscles, attaches to another bone across a joint.

Question 9

muscle

Answer 9

group of individual muscle cells, all with the same origin and insertion and all with the same function.

Question 10

fascicles

Answer 10

a muscle appears to be arranged in bundles

Question 11

fascia

Answer 11

enclosed in a sheath of a type of fibrous connective tissue

Question 12

muscle fibers

Answer 12

fascicle contains anywhere from a few dozen to thousands of individual muscle cells

Question 13

myofibrils

Answer 13

nuclei are located just under the cell membrane because nearly the entire interior of the cell is packed with long cylindrical structures arranged in parallel

Question 14

sarcomere

Answer 14

segment of a myofibril from one Z-line to the next. consists of myosin and actin.

Question 15

myosin

Answer 15

thick filaments composed of a protein

Question 16

actin

Answer 16

interspersed at regular intervals within filaments of a different protein

Question 17

4 keys makes a skeletal muscle cell contract and relax

Answer 17

1. a skeletal muscle cell must be activated by a nerve. It does not contract on its own.
2. Nerve activation increases the concentration of calcium in the vicinity of the contractile proteins.
3. The presence of calcium permits contraction. the absence of calcium prevents contraction
4. When muscle cell is no longer stimulated by a nerve, contraction ends

Question 18

Motor neurons

Answer 18

skeletal muscle cells are stimulated to contract by certain nerve cells. releases acetylcholine at the neuromuscular junction

Question 19

neurotransmitter

Answer 19

chemical released by nerve cells that has either an excitatory or inhibitory effect on another excitable cell

Question 20

neuromuscular junction

Answer 20

junction between a motor neurons and skeletal muscle cells

Question 21

sarcoplasmic reticulum

Answer 21

T tubules are in close contact with a series of membrane-bound chambers. store ionic calcium

Question 22

sliding filament mechanism

Answer 22

muscles contract when sarcomeres shorten and sarcomeres shorten when the thick and thin filaments slide past each other

Question 23

calcium

Answer 23

release of calcium from the sarcoplasmic reticulum triggers contraction. Calcium allows cross-bridges to form between myosin and actin, which leads to contraction by a sliding filament mechanism.

Question 24

ATP

Answer 24

Energy from the breakdown of ATP is required for contraction and for calcium transport. ATP is produced from metabolism of creatine phosphate and glycogen stores within the muscle, and from glucose and fatty acids obtained from the blood.

Question 25

2 types of contraction

Answer 25

1. Isotonic - occur whenever a muscle shortens while maintaining a constant force. 2. isometric - force is generated, muscle tension increases and muscle may even shorten a little as tendons are stretched slightly but bones and objects do not move

Question 26

Motor unit

Answer 26

smallest functional unit of muscle contraction because when the motor neuroncles is activated all the muscle cells in that motor unit are activated together.

Question 27

muscle tension

Answer 27

mechanical force that muscles generate when they contract

Question 28

3 factors of tension

Answer 28

1. number of muscle cells in each motor unit 2. number of motor units active at any one time 3. frequency of stimulation of individual motor units

Question 29

all-or-none principle

Answer 29

muscle cells are completely under the control of their motor neuron.

Question 30

recruitment

Answer 30

increasing tone or force by activating more motor units

Question 31

stimulus-twitch has 3 stages

Answer 31

1. Latent period - time between stimulation and the start of contraction 2. contraction - time during which the muscle actually shortens 3. relaxation - muscle returns to its original length

Question 32

summation

Answer 32

increasing muscle force by increasing the rate of stimulation of motor units

Question 33

slow-twitch fibers

Answer 33

rely on aerobic metabolism and are most useful for endurance

Question 34

fast-twitch

Answer 34

capable of short bursts of high-internsity work and are most useful where strength is required.

Question 35

cardiac and smooth muscle

Answer 35

involuntary and can contract without signals from the nerves. but they are also capable of responding to nerves

Question 36

cardiac

Answer 36

contracts and relaxes rhythmically. has thick and thin filaments arranged in sarcomeres. found only in heart, pumping blood, spontaneous (pacemaker cells) modifiable by nerves.

Question 37

smooth

Answer 37

sustain a contraction indefinitely. fillaments in smooth are arranged in bundles that crisscross the cell. found in walls of blood vessels and walls of organs of the digestive respiratory urinary and reproductive tracts; control of blood vessel diameter

Question 38

Muscular dystrophy

Answer 38

abnormal growth, a single defective gene results in the lack of a particular muscle cell protein.