Chapter 9 - Muscular System

Question 1

General Properties of Muscle Tissue

Answer 1

-Contractibility
-Excitability
-Extensibility
-Elasticity

Question 2

Contractibility

Answer 2

The ability of muscles to shorten forcefully/contract

Question 3

Excitability

Answer 3

The capacity of muscles to respond to electrical stimuli

Question 4

Extensibility

Answer 4

Muscles can be stretched beyond their normal resting length and still be able to contract

Question 5

Elasticity

Answer 5

The ability of muscles to spring back to their original resting lengths after being stretched

Question 6

Functions of the muscular system

Answer 6

-Movement
-Maintenance of posture
-Respiration
-Production of body heat
-Communication
-Constriction of organs and vessels
-Contraction of the heart

Question 7

Epimysium

Answer 7

Layer of CT that surrounds a muscle (many fasicles)

Question 8

Perimysium

Answer 8

-Loose CT surrounding a group of muscle fibers
-Passage for blood vessels and nerves

Question 9

Fascicle

Answer 9

Bundle of muscle cells

Question 10

Endomysium

Answer 10

Loose CT separating individual muscle fibers within each fascicle

Question 11

Caveolae

Answer 11

-In smooth muscle cells
-Indentations in sarcolemma
-Many act like T tubules

Question 12

What do smooth muscle cells have instead of Z disks?

Answer 12

-Dense bodies
-Have non-contractile intermediate filaments

Question 13

Myosin phosphatase

Answer 13

Causes relaxation in smooth muscle cells

Question 14

Triad

Answer 14

Formed from two terminal cisternae and their associated T tubule

Question 15

Myofibrils

Answer 15

-Bundles of protein filaments
-Contain myofilaments that cause contraction

Question 16

Z disk

Answer 16

-Filamentous network of protein
-Serves as attachment for actin myofilaments

Question 17

I bands

Answer 17

-Lighter-staining region
-Each contains a Z disk
-Extends to end of myosin myofilaments

Question 18

A bands

Answer 18

-Central darker-staining region
-Overlapping actin and myosin myofilaments (except at center)

Question 19

H zone

Answer 19

Region in A band where actin and myosin do not overlap

Question 20

M line

Answer 20

-Middle of H zone
-Delicate filaments holding myosin in place

Question 21

Depolarization

Answer 21

Inside of the plasma membrane becomes less negative

Question 22

Repolarization

Answer 22

Return of the resting membrane potential

Question 23

Stages of Action Potential

Answer 23

-Resting: All Na and some K channels closed; inside cell more (-) than outside
-Depolarization: Na channels open
-Repolarization: Na channels closed, more K channels open

Question 24

Excitation-Contraction Coupling

Answer 24

Links mechanical and electrical components of contraction

Question 25

Muscle relaxation

Answer 25

-Ca2+ moves back into sarcoplasmic reticulum by active transport (needs ATP)
-Ca2+ moves away from troponin-tropomyosin complex
-Complex reestablishes its position and blocks binding sites

Question 26

Isometric Contractions

Answer 26

-No change in length but tension increases
-Postural muscles

Question 27

Isotonic Contractions

Answer 27

Change in length but tension constant

Question 28

Motor unit

Answer 28

-A single motor neuron and all muscle fibers innervated by it
-Large muscles have units with many muscle fibers, small/delicate muscles have units with only a few

Question 29

Treppe

Answer 29

-Graded muscle response
-Occurs in muscle rested for long period
-Each subsequent contraction is stronger than the last until all are equal (after a few stimuli)
-More Ca2+ in sarcoplasm, not all taken up into SR after each contraction

Question 30

Incomplete tetanus

Answer 30

Muscle fibers partially relax between contractions

Question 31

Complete tetanus

Answer 31

No relaxation between contractions

Question 32

Active tension

Answer 32

-Force applied to an object to be lifted when a muscle contracts
-Increases or decreases as a muscle fiber changes in length

Question 33

Passive tension

Answer 33

Tension applied to load when muscle stretches but is not stimulated

Question 34

Sub-threshold stimulus

Answer 34

No action potential - no contraction

Question 35

Threshold stimulus

Answer 35

Action potential - contraction

Question 36

Submaximal stimuli

Answer 36

Stronger stimuli that produce action potentials in axons of additional motor units

Question 37

Maximal stimulus

Answer 37

Action potentials are produced in axons of all motor units of a muscle

Question 38

Size principle

Answer 38

During recruitment, small motor units are recruited first, then larger motor units

Question 39

Muscle tone

Answer 39

Constant tension by muscles for long periods of time

Question 40

Types of Isotonic Contractions

Answer 40

-Concentric (overcomes opposing resistance and muscle shortens)
-Eccentric (tension maintained, muscle lengthens)

Question 41

Physiological contracture

Answer 41

State of fatigue where due to lack of ATP neither contraction nor relaxation can occur

Question 42

Sarcopenia

Answer 42

Muscle atrophy

Question 43

Power stroke

Answer 43

Movement of myosin head during contraction

Question 44

Recovery stroke

Answer 44

Returning of myosin head to low-energy position

Question 45

Major ATP-dependent events for relaxation

Answer 45

-Sodium-potassium pump to return to resting membrane potential
-ATP required to detach myosin heads from active site for recovery stroke
-ATP needed for active transport of Ca2+ into SR

Question 46

Major factors that increase number of cross-bridges that form

Answer 46

-Frequency of stimulation
-Muscle fiber diameter
-Muscle fiber length at time of contraction