Chapter 10 Physiology

Front 1

Functions of the muscle

Back 1

1) Produces motion of the skeleton
2) Stabilizes body position.
3) Regulates organ volume to store and release materials.
4) Moves substance within the body.
5) Thermogenesis- produces heat to warm the body.

Front 2

Properties of the muscle
(ECEE)

Back 2

1) Electrical excitability: The ability to respond to certain stimuli by producing electrical signals (muscle action potentials).
2) Contractility: The ability to generate tension to do work.
3) Extensibility: The ability to stretch without damage, (smooth> cardiac> skeletal).
4) Elasticity: The ability to return to its original shape after contracting or extending.

Hint 2

Eat a big meal and stretch your stomach.
A rubber band is both extensible and elastic.
Cardiac muscle and smooth muscle have the same proteins but are arranged differently.

Front 3

Muscle fiber

Back 3

An individual muscle cell.

Front 4

Fascia

Back 4

A sheet of fibrous C.T. that surrounds muscles and other body organs.
(2 layers)

Front 5

Superficial fascia

Back 5

Separates muscles from the skin and is composed of adipose and aerolar C.T.

Hint 5

Areolar C.T. allows skin to very movable over muscle.

Front 6

Deep fascia

Back 6

Dense irregular C.T. that lines the body wall and also holds muscles with similar functions together.

Front 7

Epimysium

Back 7

The outer most layer which surrounds the muscle.

Front 8

Perimysium

Back 8

Surrounds each fascicle (a bundle of 10-100 muscle fibers).

Hint 8

Many fascicles are large enough to be seen. There are the 'grain" of meat.

Front 9

Endomysium

Back 9

A thin sheath of aerolar C.T. around each muscle fiber.

Front 10

Tendon

Back 10

A cord of dense regular connective tissue around each muscle fiber. Connects muscle to bone.

Front 11

Aponeurosis

Back 11

A broad flat tendon.

Front 12

Somatic motor neurons

Back 12

Stimulate skeletal muscle to contract.

Front 13

Axon collaterals

Back 13

Axons of somatic motor neurons branch inside the muscle into axon collaterals, which extend to different muscle fibers.

Front 14

Neuromuscular junction (NMJ)

Back 14

The connection between the neuron and the muscle fiber.

Front 15

Synaptic end bulbs

Back 15

here axon terminals expand into clusters of synaptic end bulbs.

Front 16

Blood supply

Back 16

Muscle is well supplied with blood so that each muscle fiber is in close contact with blood capillaries.

Front 17

Can a mature muscle fiber undergo cell division?

Back 17

No. A mature muscle fiber CANNOT undergo cell division.

Front 18

Satellite cell

Back 18

Cells in mature muscle that retain the capacity to regenerate muscle fibers.

Front 19

Sarcolemma

Back 19

Plasma membrane of a muscle fiber.

Front 20

T (Transverse) tubules

Back 20

Tiny invaginations of the sarcolemma that tunnel into each fiber and are filled with extracellular fluid (ECF). These allow the action potential to spread rapidly throughout the muscle cell.

Front 21

Sarcoplasm

Back 21

The muscle fiber's cytoplasm. It contains lots of glycogen, and myoglobin which binds oxygen needed for ATP production.

Front 22

Sarcoplasmic reticulum

Back 22

Modified endoplasmic reticulum of muscle fibers that stores Ca2+ and ends in terminal cisterns near T tubules.

Front 23

Myofibrils

Back 23

Lengthwise threads inside and extend the entire length of the fiber. They contain thin filaments and thick filaments arranged in compartments called sacromeres. These are connected end-to-end and are the functional units of a myofibril.

Front 24

Muscle protein

Back 24

Thick and thin filaments overlap each other in a pattern that creates striations.
A) Light I bands: contain only thin filaments.
B) Dark A bands: contains entire thick filament.
Arranged in compartments called sacromeres, separated by Z discs.
In the overlap region, six thin filaments surround each thick filament.

Front 25

Myosin

Back 25

Makes up the thick filaments and serves as the motor protein to move the thin filaments. It has a golf-club shape with myosin heads that will bind to thin filaments to move them.

Front 26

Actin

Back 26

Makes up most of the thin filaments and contains myosin binding sites that will bond to the myosin heads to move the actions during contraction.

Front 27

Tropomyosin

Back 27

Covers the myosin-bindin sites on actin to prevent contraction in a resting muscle.

Front 28

Troponin

Back 28

Holds the tropomyosin in place.

Front 29

Titin

Back 29

Gives elasticity and extensibility to myofibrils by stretching and then springing back.

Front 30

Dystrophin

Back 30

Links thin filaments to the sarcolemma to strengthen it and help transmit force to tendons.

Front 31

Where is the signal to contract passed from the neuron to the muscle fiber?

Back 31

The neuromuscular junction (NMJ)

Front 32

Where is the synaptic end bulb?

Back 32

On the neuron side of a small gap (synaptic cleft) between the neuron and muscle fiber.

Front 33

Where is the motor end plate?
(modified sarcolemma)

Back 33

On the muscle side.

Front 34

Summary of how muscle action potential arises
(AP= action potential)

Back 34

Nerve impulse-> release of Ach-> activation of Ach receptors-> muscle action potential -> termination of Ach activity

Front 35

AP 1) What triggers the release of the neurotransmitter acetylcholine (Ach) from synaptic vesicles?

Back 35

When the nerve impulse (nerve action potential) arrives at the synaptic end bulb.

Front 36

AP 2) Ach diffuses across the synaptic cleft to the motor end plate and binds to its receptors on the ____ ?

Back 36

Sarcolemma

Front 37

AP 3) The binding of Ach to its receptors on the sarcolemma, opens ion channels which allow Na+ to rush in and generate what?

Back 37

A muscle action potential: A temporary positive charge on the inside of the muscle fiber.
This causes contraction as it travels through the T tubules.

Front 38

AP 4) What enzyme then breaks down the Ach to prevent excessive stimulation?

Back 38

Acetylcholinesterase

Front 39

Thin filaments are attached to the ends of each sacromere and are separated by a gap. WHen muscles contract, how is this gap closed?

Back 39

Thin filaments moving toward the center of the sarcomere and it shortens.

Front 40

Summary of the sliding filament mechanism of muscle contraction
(SF= sliding filament)

Back 40

Hydrolysis of ATp energizes myosin-> attachment of myosin to actin forms cross bridges-> power stroke moves the actin -> detachment of myosin from actin

Front 41

SF 1) When the muscle action potential reaches the terminal cisterns what happens?

Back 41

It stimulatesCa2+ channels to open and release Ca2+ into the surrounding muscle cell's cytoplasm. (sarcoplasm)

Front 42

SF 2) What causes the troponin-tropomyosin complex to shift which on covers the myosin-binding sites on the actin?

Back 42

Ca2-+ bonds to troponin on thin filaments.

Front 43

SF 3) What is the power stroke and requires energy?

Back 43

An energized myosin head bonds to the actin forming a cross bride and swivels toward the center of the sarcomere pulling the actin toward the center.

Front 44

SF 4) ATP bonds to the myosin head. It is broken down and its energy causes the head to A, C, and C further down the thin filament, toward the end of the sarcomere.

Back 44

A: Detach
B: Rotate
C: Reattach

Front 45

SF 5) The myosin head then swivels and pulls that binding site further toward the ?

Back 45

Center

Front 46

SF 6) This is repeated as long as what is present?

Back 46

Ca2+

Front 47

SF 7) What happens in relaxation?

Back 47

Acetylcholinerase breaks down the acetylcholine transmitter at the motor end plate so that muscle action potentials are no longer generated and Ca2+ channels close.

Front 48

SF 8) Also Ca2+ is pumped back into terminal cisterns so that troponin-tropomyosin shifts back over the myosin binding sites on actin and ?

Back 48

Muscle stops contracting

Front 49

SF 9) Length-tension relationship

Back 49

A muscle fiber develops its greatest tension when there is an optimal zone of overlap between thick and thin filaments.

Front 50

Creatine phosphate

Back 50

Provides enough energy for maximal contraction for about 15 seconds. Creatine phosphate is stored in muscle and then transfers its high energy phosphate group to ADP to make ATP.

Front 51

Anaerobic cellular respiration

Back 51

Provides enough energy for 30-40 seconds and it occurs when O2 is NOT available for aerobic cell respiration.
1) Glucose, from the blood and form the breakdown of glycogen within the muscle, is broken down into pyruvic acid by a process called glycolysis to produce a net of 2 ATP per glucose.
2) If O2 is NOT available, most of the pyruciv acid is broken down into lactic acid and most of this diffuses back into blood to be converted back ito glucose in the liver.
3) this is an anaerobic process since it does NOT require O2.

Front 52

Aerobic cellular respiration

Back 52

Provides most of the ATP in muscle activity that lasts longer than 30 seconds.
1) In the presence of o2, the pyretic acid from glycolysis is NOT broken down into lactic acid, but is completely broken down into Co2 and water in mitochondria. Also 36 ATP are produced.
2) ALso fatty acids and amino acids can be broken down.

Front 53

Structure of a motor unit

Back 53

A motor unit consist of one somatic motor neuron and all of the muscle fibers that is stimulates.

Front 54

Function of a motor unit

Back 54

Since all of the fibers of one motor unit contract and relax together, we can control the strength of a contraction by the number and size of motor units stimulated.

Front 55

Twitch contraction

Back 55

A brief contraction f all the muscle fibers in a motor unit in response to one action potential (nerve impulse) form a somatic motor neuron. It involves four phases recorded on amyogram.

Front 56

Latent Period

Back 56

Time between application of the stimulus and the beginning of contraction. Ca2+ is being released from the sarcoplasmic reticulum and filaments start to exert tension as slack is being removed from elastic components. First phase of twitch contraction.

Front 57

Contraction period

Back 57

Fibers shorten. Phase two of the twitch contraction.

Front 58

Relaxation period

Back 58

Ca2+ is actively pumped back into sarcoplasmic reticulum. Phase three of twitch contraction.

Front 59

Refractory period

Back 59

The time following a stimulus during a fiber cannot respond to another stimulus. fourth and last phase of twitch contraction.

Front 60

Frequency of stimulation

Back 60

The number of nerve imposes arriving at the NMJ per second and is the main factor that determines a muscle fiber's tension.

Front 61

Wave summation

Back 61

If subsequent stimuli arrive before a muscle fiber has finished relaxing, then they will produce a stronger contraction.

Front 62

Tetanus

Back 62

A sustained contraction.
1) Fused (complete) tetanus: shows no discernible twitches.
2) UNfused (incomplete) tetanus: shows discernible twitches,

Front 63

Motor unit recruitment

Back 63

The process in which the number of motor units activated increases. It helps produce smooth fine movements. Also if some units are activated and some are not this allows units to rest between contractions.

Front 64

Size of motor units activated

Back 64

The larger the motor unit that is activated, the stronger the contraction. But smaller units can give more precise movements.

Front 65

Muscle tone

Back 65

Small amount of tension in muscle due to weak, involuntary contractions. When this is lost, the muscle become flaccid.

Front 66

Isomeric contraction

Back 66

Muscle does not shorten, but develops tension.

Front 67

isotonic contraction

Back 67

Tension stays almost constant while muscle shortens to move a load.

Front 68

Slow oxidative fibers (SO)

Back 68

1) ATP is generated especially aerobically.
2) Contain many mitochondria and lots of myoglobin and have many blood capillaries.
3) Split ATP slowly and are very resistant to fatigue. Ex: in neck muscles to hold up the head.

Front 69

Fast ocidative-glycolitic fibers (FOG):

Back 69

1) ATP is generated especially aerobically but also by anaerobic cell respiration (glycolysis).
2) ALso contain many mitochondria, blood capillaries and contain lots of myoglobin.
3) Split ATP very rapidly and are moderately resistant to fatigue. Ex: in leg muscles of sprinters.

Front 70

Fast glycolytic fibers:

Back 70

1) Generate ATP anaerobically (by glycolysis).
2) Relative few mitochondria, blood capillaries, and have relatively low amounts of myoglobin.
3) Split ATP rapidly but have the lowest resistance to fatigue. Ex: arm muscles.

Front 71

What are the effects of exercise on different types of skeletal muscle fibers?

Back 71

A. Endurance exercises cause some fast glycolytic fibers to transform into fast oxidative-glycoytic.
B. Exercise that takes great strength for short periods increases the size and strength of fast glycolytic fibers and thus the size of muscles.
C. Exercise does not change the number of fibers.

Front 72

Visceral (single unit) smooth muscle tissue

Back 72

A. Occurs in walls of small arteries, veins, and hollow viscera (organs); the fibers are arranged in a network.
B. An impulse to contract spreads to neighboring cells, which on tract together (as a single unit).

Front 73

Multiunit smooth muscle tissue

Back 73

A. It occurs in airways, large artery walls, arrestor pili muscles, and eye muscles that adjust pupil diameter and focus.
B. The fibers operate singly rather than as a unit. (Gives fine precise smooth muscle motor control)

Front 74

Microscopic anatomy

Back 74

A. Sarcoplasm of smooth muscle fibers contains both thick and thin filaments with are not organized into orderly sarcomeres.
B. Smooth muscle fibers contain intermediate filaments which are attached to dense bodies.

Front 75

Functional characteristics of smooth muscle tissue

Back 75

1) Their contractions start more slowly than in other muscle. They also last longer, which produces smooth muscle tone.
2) SMooth muscle fibers contract in response to autonomic nervous system stimulation, stretching, hormones, or local factors.
3) Smooth muscle fibers can stretch considerably and still maintain their contractile function (stress-relaxation response).

Front 76

How do skeletal muscle fibers regenerate?

Back 76

1) Regeneration is limited due to replacement of damaged muscle fibers by fibrous scar tissue (fibrosis).
2) Satellite cells help in regeneration.

Front 77

How do cardiac muscle fibers regenerate?

Back 77

1) Lacks satellite cells and therefore has low regeneration capability.
2) Stem cells may migrate from blood to form new muscle fibers.

Front 78

How do smooth muscle fibers regenerate?

Back 78

1) Has the greatest power of regeneration of all muscle types.
2) Some smooth muscle retains the capacity to divide.
3) Also there are some stem cells (pericytes) that can form new smooth muscle.

Front 79

Development of muscles

Back 79

A. Muscle fibers of the iris in the eye and the arrestor pili muscles develop from ectoderm.
B. All other muscles develop from mesoderm. Most skeletal muscles develop from mesoderm of somites in the embryo.

Front 80

How does aging affect skeletal muscle tissue?

Back 80

A. Loss of muscle mass, replaced by fibrous C.T. and fat.
B. Decrease in maximal strength.
C. Muscle reflexes slow down.
D. Loss of flexibility.
E. Percentage of fibers that are the slow oxidative apparently increases.

Front 81

Muscular dystrophy

Back 81

AN inherited desease characterized by degeneration of muscle fibers leading to atrophy of skeletal muscle. The gene that codes for dystrophin is mutated.

Front 82

Myasthenia gravis

Back 82

A weakness of skeletal muscles caused by a partial blockage of impulse transmission at the neuromuscular junction. An autoimmune disease most often affects the face and neck with difficulty in swallowing and double vision. Seventy five % are associate with a tumor or hyperplasia of the thymus.

Front 83

Fibromyalgia

Back 83

Affects fibrous C.T. of muscles, tendons, and ligaments. Gentle pressure at "tender points" produces pain. Also severe fatigue, poor sleep, headaches, and depression may occur.

Front 84

Spasm

Back 84

A sudden involuntary contraction in a single muscle in a large group of muscles.

Front 85

Cramp

Back 85

A painful spasm

Front 86

Tic

Back 86

A spasmodic, involuntary twitching of muscles under voluntary control.

Front 87

Tremor

Back 87

A rhythmic involuntary contraction of opposing muscle groups.

Front 88

Fasiculation

Back 88

Involuntary brief twitch of a motor unit visible under the skin.

Front 89

Fibrillation

Back 89

Involuntary twitches of a single muscle fiber but is not visible under the skin. It can be recorded by electromyography.

Front 90

Myalgia

Back 90

Pain in or associated with muscles.

Front 91

Myomalacia

Back 91

Pathological softening of muscle tissue.

Front 92

Myositis

Back 92

Inflammation of muscle fibers (cells).

Front 93

Myotonia

Back 93

Increase muscular excitability and contractibility with decrease power of relaxation; tonic spasm of a muscle.

Front 94

Volkmann's contracture

Back 94

Permanent shortening (contracture) and lack of extensibility of a muscle due to replacement of destroyed muscle fibers by fibrous connective tissue. Usually occur if a bandage or cast is on too tight (typically forearm flexors).