Exam 3: Muscle Tissue

Question 1

How does the muscular system produce motion?

Answer 1

Contraction and relaxation of muscles

Question 2

Functions of muscle tissue

Answer 2

Produce skeletal movement
Stabilize posture and body position
Support soft tissues
Guard entrances and exits 
Maintain body temperature 
Store nutrient reserves

Question 3

Properties of muscle tissue

Answer 3

Electrical excitability
Contractility
Extensibility
Elasticity

Question 4

The ability to respond to internal or external stimuli by producing action potentials

Answer 4

Electrical excitability

Question 5

The ability to contract when stimulated by an action potential

Answer 5

Contractility

Question 6

The ability to stretch without being damaged

Answer 6

Extensibility

Question 7

The ability to return to original shape and size after contraction or extension

Answer 7

Elasticity

Question 8

Types of muscle tissue

Answer 8

Skeletal muscle
Cardiac muscle
Smooth muscle

Question 9

Skeletal muscle

Answer 9

Associated with skeleton and skin
Striated
Mainly voluntary control

Question 10

Cardiac muscle

Answer 10

Located in heart
Striated
Involuntary control

Question 11

Smooth muscle

Answer 11

Located in walls of hollow internal structures (respiratory, circulatory, digestive systems, etc. ) and in skin
Non-striated
Involuntary control

Question 12

Also called muscle fibers because of their elongated shape

Answer 12

Muscle cells

Question 13

What are the connective tissue components of skeletal muscle?

Answer 13

Fascia
Tendons
Deep fascia

Question 14

Sheet of connective tissue surrounding a muscle

Answer 14

Fascia

Question 15

Connects muscle to skin

Answer 15

Superficial fascia

Question 16

Connects muscle to muscle or muscle to bone

Answer 16

Deep fascia

Question 17

Extensions of connective tissue (fascia) that attach a skeletal muscle to the periosteum of a bone

Answer 17

Tendons

Question 18

Deep fascia is underlaid by 3 other layers of connective tissue which are:

Answer 18

Epimysium
Perimysium
Endomysium

Question 19

Connective tissue that surrounds the entire muscle

Answer 19

Epimysium

Question 20

Connective tissue that surrounds groups of 10-100 muscle fibers and separates them into bundles, or fascicles

Answer 20

Perimysium

Question 21

Connective tissue that surrounds and separate individual muscle fibers within a fascicle

Answer 21

Endomysium

Question 22

How does the muscle tissue get nerve and blood supply?

Answer 22

• Somatic motor neurons stimulate muscles. Each neuron has branches that extend to individual muscle fibers.
• Each muscle supplied by one artery and one or two veins. Associated with a capillary bed that extends to all muscle fibers

Question 23

What is the embryonic origin of muscle fibers?

Answer 23

Arise from fusion of myoblasts in embryo

Question 24

Plasma membrane of muscle fibers

Answer 24

Sarcolemma

Question 25

Invaginations of the sarcolemma extending from surface of muscle fiber inward; Open to outside of cell and Filled with interstitial fluid

Answer 25

Transverse tubules

Question 26

Cytoplasm of muscle fibers Richly supplied with glycogen Richly supplied with myoglobin

Answer 26

Sarcoplasm

Question 27

Extends length for muscle fiber Contractile organelles of skeletal muscle fibers Striated

Answer 27

Myofibril

Question 28

Surrounds myofibril and is a system of fluid filled membranous sacs, similar to smooth ER; stores Ca2+

Answer 28

Sarcoplasmic reticulum

Question 29

2 types of protein filaments that compose myofibrils

Answer 29

Thick and thin filaments

Question 30

Functional unit of myofibril, and compartments where filaments are arranged

Answer 30

Sarcomeres

Question 31

Each thick filament is surrounded by ____ thin filaments.

Answer 31

Two

Question 32

Regions of the sarcomere

Answer 32

``` A band I band Zone of overlap Z disc H zone M line ```

Question 33

Extends length of thick filaments

Answer 33

A line

Question 34

Region with thin filaments only

Answer 34

I line

Question 35

Region of overlap between thick and thin filaments

Answer 35

Zone of overlap

Question 36

Region found through center of each I band

Answer 36

Z disc

Question 37

Region with thick filaments only

Answer 37

H zone

Question 38

Region that support proteins linking thick filaments

Answer 38

M line

Question 39

Myofibrils include which proteins?

Answer 39

Contractile protein - generates force during contraction Regulatory protein - switch contraction process on and off Structural protein - keep thick and thin filaments in alignment

Question 40

Two contractile proteins

Answer 40

Myosin and actin

Question 41

Main component of thick filaments Functions as motor protein Includes tail and two "heads" Converts chemical energy of ATP into mechanical energy of motion (production of force)

Answer 41

Myosin

Question 42

Main component of thin filaments | Functions as anchor point for myosin

Answer 42

Actin

Question 43

Two regulatory proteins

Answer 43

Troponin and tropomysin

Question 44

Where do regulatory proteins occur?

Answer 44

Thin filament

Question 45

Overview of sliding filament mechanism

Answer 45

- Muscles get shorter (during contraction) or longer (during relaxation) because thick and thin filaments side past one another - Myosin heads bind to actin in thin filaments and "walk" along thin filaments, pulling thin filaments toward M line - Sarcomeres contract

Question 46

Contraction cycle (just be familiar with it)

Answer 46

1. ) Contraction cycles begins - Myosin head is already energized - Ca2+ ions enter myofibril 2. ) Active-site exposure - Ca2+ binds to troponin - Troponin pulls troponin myosin away from active sites of actin 3. ) Cross-bridge formation - Energized myosin heads bind to active sites of actin - Forming cross-bridges between thick and thin filaments 4. ) Myosin head pivoting - Myosin head pivoted toward M line during power stroke - ADP and phosphate group are released 5. ) Cross-bridge detachment - Another ATP binds to myosin head - Myosin head detaches from active site of actin - Cross-bridge is broken 6. ) Myosin reactivation - Free myosin head cleaves phosphate group from ATP - Myosin head becomes energized

Question 47

Describe the excitation-contraction coupling.

Answer 47

Increase of Ca2+ conc. in cytosol triggers muscle contraction Sarcoplasmic reticulum releases Ca2+ into cytosol via Ca2+ release channels Ca2+ release channels open in response to a muscle action potential (electrical excitation)

Question 48

Nerve action potential propagating triggers a muscle action potential via a ____________.

Answer 48

Neurotransmitter

Question 49

Synapse between neuron and muscle fiber

Answer 49

Neuromuscular junction (NMJ)

Question 50

Neurotransmitter responsible for communication across NMJ

Answer 50

Acetylcholine

Question 51

Describe the events at the NMJ

Answer 51

1. ) ACh packaged in vesicles at synaptic end bulb of neuron 2. ) Action potential reaches synaptic end bulb of neuron 3. ) Action potential triggers release of ACh into synaptic cleft via exocytosis 4. ) ACh diffuses across synaptic cleft and binds to receptors in sarcolemma of muscle fiber - Na+ channels in sarcolemma open, and Na+ enters sarcoplasm 5. ) Acetylcholinesterase (AChE) breaks down ACh

Question 52

What breaks down ACh?

Answer 52

Acetylcholinesterase (AChE)

Question 53

Force of contraction of a muscle varies due to:

Answer 53

Nutrient and oxygen availability Frequency of stimulation (rate at which action potentials arrive at NMJ) Amount of stretch before contraction Number of muscle fibers contracting

Question 54

Contraction of all muscle fiber in response to one nerve action potential

Answer 54

Twitch contraction

Question 55

Three phases of the twitch contraction

Answer 55

Latent period Contraction period Relaxation period

Question 56

What happens when there are 20-30 action potentials per second?

Answer 56

Incomplete (unfused) tetanus Sustained but wavering contraction Muscle fibers can't completely relax between stimuli

Question 57

What happens when there are 80-100 action potentials per second?

Answer 57

Complete (fused) tetanus Sustained, unwavering contraction Muscle fibers can't relax at all between stimuli