Chapter 11 Study Topics- Muscle Tissue

Question 1

List and define the 5 universal characteristics of muscles.

Answer 1

1.Excitability (responsiveness)—to chemical signals, stretch, and electrical changes across the plasma membrane​
2.Conductivity—local electrical excitation sets off a wave of excitation that travels along the muscle fiber​
3.Contractility—shortens when stimulated​
4.Extensibility—capable of being stretched between contractions​
5. Elasticity—returns to its original rest length after being stretched​

Question 2

Define the following: endomysium, perimysium, epimysium

Answer 2

endomysium—surrounds each muscle fibers
perimysium— bundles muscle fibers into fascicles
epimysium— surrounds entire muscle

Question 3

Match the components of a muscle fiber (cell) to their function: sarcolemma, sarcoplasm, myofibril, glycogen, myoglobin, SR, T tubules, myoblasts

Answer 3

Sarcolemma—plasma membrane of a muscle fiber
Sarcoplasm—cytoplasm of a muscle fiber​
Sarcoplasmic reticulum (SR)-smooth ER that forms a network around each myofibril
Transverse (T) tubules—tubular infoldings of the sarcolemma which penetrate through the cell and emerge on the other side​
Myoblasts—stem cells that fused to form each muscle fiber early in development, each contributing one nucleus

Question 4

List the 3 myofilaments. What proteins are associated with each? Which proteins are contractile proteins, and which are regulatory proteins? Which regulatory protein binds to calcium?

Answer 4

1 Thick filaments—made of several hundred myosin molecules (myosin is a motor protein)

#2 Thin filaments—composed of three different protein types
Fibrous (F) actin—two intertwined strands of globular (G) actin subunits, each with an active site that can bind to head of myosin molecule​
Tropomyosin—each blocks six or seven active sites on G actin subunits​
Troponin—small, calcium-binding protein on each tropomyosin molecule​
#3 Elastic filaments—made of a huge, springy protein called titin

Question 5

Define a motor unit. Compare small motor units to large motor units

Answer 5

Motor unit—one nerve fiber and all the muscle fibers innervated by it
Small motor units provide a fine degree of control
Large motor units provides more strength that control

Question 6

Describe the structure of a neuromuscular junction. What is acetylcholine?

Answer 6

points where a nerve fiber meets its target cell. contains synaptic vesicles with neurotransmitter

Question 7

Describe the ICF and ECF environment of a cell at rest.

Answer 7

polarized—contains a net negative charge compared to the outside of the cell​

Question 8

Compare depolarization to repolarization. Describe the ion movements that occur during each.

Answer 8

depolarization- becoming positive
repolarization- becoming negative inside

Question 9

Define “action potential”.

Answer 9

up-and-down voltage shift

Question 10

How do toxins affect muscles? Compare spastic paralysis to flaccid paralysis.

Answer 10

interfering with synaptic function can paralyze muscles Some pesticides contain cholinesterase inhibitors​
Spastic paralysis—a state of continual contraction of the muscles; possible suffocation
Flaccid paralysis—a state in which the muscles are limp and cannot contract

Question 11

List the 4 major phases of contraction and relaxation and describe the 18 steps that occur.

Answer 11

1. Excitation

#1 Arrical of nerve signal 
#2 Acetylcholine (ACh) release 
#3 Binding of ACh to receptor 
#4 Opening of ligand- regulated ions
#5 Open of voltage- regulated ion gate #2. Excitation
#6 Action potentials propagated down T tubles 
#7 Calsium released from terminal cisterns 
#8 Binding of calcium to troponin
#9 Shifting of tropomysin #3. Contraction #10 Activation and cooking of myosin heads(recovery) stroke 
#11 Formation of myosin- actin cross bridge 
#12 Power stroke 
#13 Binding of new ATP #4. Relaxation
#14 Cessation of nervous stimulation and ACh released 
#15 ACh breakdown by Aectylcholinesterase
#16 Reabsorption of calcium ions by sarcoplasmic
#17 Loss of calcium ions troponin
#18 Return of tropomyosin to position blocking active sites of actin

Question 12

What happens to the H zones during contraction?

Answer 12

shorten and disappear

Question 13

How do muscles ensure that they can produce the greatest force when contracting?

Answer 13

There will be insufficient overlap of the myofilaments and less force will be produced

Question 14

Define rigor mortis. Release of which ion causes contraction?

Answer 14

hardening of muscles and stiffening of body beginning 3–4 hours after death.Ca2+

Question 15

What are the 3 phases of a muscle twitch? What happens in each? What is the term for the minimum voltage that causes a muscle twitch?

Answer 15

Latent period—delay just after stimulation of muscle​
Contraction phase—external tension is generated and a load is moved as the muscle fiber shortens​
Relaxation phase—sarcoplasmic calcium levels fall as calcium is reabsorbed into sarcoplasmic reticulum; tension declines​

Question 16

What two factors affect twitch strength? How?

Answer 16

Muscle size— thicker forms more cross-bridge
temporal summation—greater the frequency of stimulation, the stronger the muscle contraction

Question 17

What does the size principle tell us about muscle stimuli?

Answer 17

weak stimuli (low voltage) recruit small units, while strong stimuli recruit small and large units for powerful movements​

Question 18

Compare incomplete tetanus to fused tetanus

Answer 18

Incomplete tetanus- Only particle relaxation between stimuli resulting in fluttering
Fused Tetanus- unnaturally high stimulus frequencies cause a steady contraction

Question 19

Compare isometric contraction to isotonic contraction. What are the 2 forms of isotonic contraction?

Answer 19

Isometric contraction—contraction without a change in length (Same)
Isotonic contraction—contraction with a change in length but no change in tension​ (Change)
Concentric contraction: muscle shortens as it maintains tension (example: lifting weight)​
Eccentric contraction: muscle lengthens as it maintains tension (example: slowly lowering weight)​

Question 20

Compare anaerobic fermentation or aerobic respiration. Which one is more efficient?

Answer 20

Anaerobic fermentation—enables cells to produce ATP in the absence of oxygen; yields little ATP and lactate, which needs to be disposed of by the liver​
Aerobic respiration—produces far more ATP; does not generate lactate; requires a continual supply of oxygen​

Question 21

How do muscles create/use immediate energy?

Answer 21

Muscles meet most ATP demand by borrowing phosphate groups (Pi) from other molecules and transferring them to ADP

Question 22

How do muscles create short-term energy?

Answer 22

Anaerobic threshold (lactate threshold)—point at which lactate becomes detectable in the blood​
Glycogen–lactate system—the pathway from glycogen to lactate​

Question 23

How do muscles create long-term energy?

Answer 23

Two enzyme systems control these phosphate transfers:​
Myokinase—transfers Pi from one ADP to another, converting the latter to ATP​
Creatine kinase—obtains Pi from a phosphate-storage molecule creatine phosphate (CP) and gives it to ADP​

Question 24

Compare the 3 types of muscle fibers. Which is fastest at contracting? Which is most fatigable? Which type is best for walking?

Answer 24

1. Slow oxidative fibers

Well adapted for endurance; resist fatigue by oxidative (aerobic) ATP production​
Important for muscles that maintain posture (e.g., erector spinae of the back, soleus of calf)​
#2. Fast glycolytic fibers
Fibers well adapted for quick responses; utilize glycolysis and anaerobic fermentation for energy​
Abundant in quick and powerful muscles: eye and hand muscles, gastrocnemius of calf and biceps brachii
#3. Intermediate
walking

Question 25

List 7 factors that affect muscular strength

Answer 25

1. Muscle size—thicker muscle forms more cross-bridges

#2 Fascicle arrangement—defines the shape and strength of a muscle​
#3 Size of active motor units—the larger the motor unit, the stronger the contraction​
#4 Multiple motor unit summation—simultaneous activation of more units increases tension​
#5 Temporal summation—the greater the frequency of stimulation, the stronger the muscle contraction​
#6 The length–tension relationship—a muscle resting at optimal length is prepared to contract more forcefully than a muscle that is excessively contracted or stretched​
#7 Fatigue—fatigued muscles contract more weakly than rested muscles​

Question 26

Compare resistance exercise to endurance exercise

Answer 26

Resistance exercise—contraction of a muscle against a load that resists movement
Endurance (aerobic) exercise—contraction of a muscle against a load that resists movement

Question 27

How do muscles create/use immediate energy?

Answer 27

Muscles meet most ATP demand by borrowing phosphate groups (Pi) from other molecules and transferring them to ADP

Question 28

How do muscles create short-term energy?

Answer 28

Anaerobic threshold (lactate threshold)—point at which lactate becomes detectable in the blood​

Question 29

How do muscles create long-term energy?

Answer 29

Two enzyme systems control these phosphate transfers:​
Myokinase—transfers Pi from one ADP to another, converting the latter to ATP​
Creatine kinase—obtains Pi from a phosphate-storage molecule creatine phosphate (CP) and gives it to ADP​

Question 30

Compare the 3 types of muscle fibers. Which is fastest at contracting? Which is most fatigable? Which type is best for walking?

Answer 30

1. Slow oxidative fibers

Well adapted for endurance; resist fatigue by oxidative (aerobic) ATP production​
Important for muscles that maintain posture (e.g., erector spinae of the back, soleus of calf)​
#2. Fast glycolytic fibers
Fibers well adapted for quick responses; utilize glycolysis and anaerobic fermentation for energy Abundant in quick and powerful muscles: eye and hand muscles, gastrocnemius of calf and biceps brachii
​#3. Intermediate
fast oxidative fibers type, is a good for sprinting and walking

Question 31

List 7 factors that affect muscular strength.

Answer 31

1. Muscle size—thicker muscle forms more cross-bridges

#2 Fascicle arrangement—defines the shape and strength of a muscle​
#3 Size of active motor units—the larger the motor unit, the stronger the contraction​
#4 Multiple motor unit summation—simultaneous activation of more units increases tension​
#5 Temporal summation—the greater the frequency of stimulation, the stronger the muscle contraction​
#6 The length–tension relationship—a muscle resting at optimal length is prepared to contract more forcefully than a muscle that is excessively contracted or stretched​
#7 Fatigue—fatigued muscles contract more weakly than rested muscles​

Question 32

Compare resistance exercise to endurance exercise.

Answer 32

Resistance exercise—contraction of a muscle against a load that resists movement
Endurance (aerobic) exercise—contraction of a muscle against a load that resists movement

Question 33

Compare skeletal muscle to smooth muscle. Which is slower to contract? Which includes troponin and which includes calmodulin?

Answer 33

Cardiac Muscle— Contract with regular rhythm, highly resistance to fatigue, works in sleep, contracts must last long enough to expel blood, Includes troponin
Smooth muscle—Contract is slower than skeletal and cardiac, injured smooth muscle regenerates well, names for its lack of striation, capable of mitosis and hyperplasia includes calmodulin

Question 34

Define peristalsis

Answer 34

Alternating contractions and relaxations of smooth muscle layers that mix and squeeze substances through the lumen of hollow organs

Question 35

Define plasticity and why it’s a characteristic of smooth muscle.

Answer 35

The ability to adjust its tension to the degree of stretch fill in hallow organs

Question 36

Describe MD myasthenia gravis, myofibrosis, and myosclerosis

Answer 36

Myasthenia gravis—autoimmune disease in which antibodies attack neuromuscular junctions and bind ACh receptors together in clusters
Fibrosis (myofibrosis)​— Replacement of muscle fibers by excessive amounts of connective tissues (fibrous scar tissue)​
Myosclerosis—​ Hardening of the muscle caused by calcification​