Lecture 24. Muscle Physiology

Question 1

What is muscle tissue responsible for ?

Answer 1

Nearly all types of body movement

Question 2

What do muscle cells consist of ?

Answer 2

Filaments of the proteins actins and myosin

Question 3

What are the functions of the filaments of the proteins actin and myosin ?

Answer 3

Enable muscles to contract

Question 4

What are the three types of muscle tissue ?

Answer 4

1. Skeletal muscle
2. Smooth muscle
3. Cardiac muscle

Question 5

What is skeletal muscle responsible for ?

Answer 5

Voluntary movement

Question 6

What is smooth muscle responsible for ?

Answer 6

Involuntary body activities

Question 7

What is cardiac muscle responsible for ?

Answer 7

Contraction of the heart

Question 8

What does muscle contraction generate ?

Answer 8

Heat

Question 9

What type of tissue is muscle ?

Answer 9

Electrically excitable tissue

Question 10

What is muscle activity a response to ?

Answer 10

Input from nervous system

Question 11

What does muscle cell contraction rely on ?

Answer 11

The interaction between thin actin filaments and thick myosin filaments

Question 12

What does skeletal systems transform muscle contraction into ?

Answer 12

Locomotion

Question 13

What does the skeleton provide ?

Answer 13

A rigid structure to which muscles attach

Question 14

How are skeletal muscles attached ?

Answer 14

In antagonistic pairs

Question 15

What are the actions of antagonistic pairs coordinated by ?

Answer 15

The nervous system

Question 16

How do paired muscles work ?

Answer 16

Cooperatively

Question 17

What is locomotion ?

Answer 17

Movement through space

Question 18

How does skeletal muscle work ?

Answer 18

Moves bones and the body

Question 19

How is skeletal muscle characterised ?

Answer 19

Hierarchy of smaller and smaller units

Question 20

What does a skeletal muscle consist of ?

Answer 20

A bundle of long fibres, each a single cell, running along the length of the muscle

Question 21

What is each muscle fiber ?

Answer 21

A bundle of smaller myofibrils arranged longitudinally

Question 22

Why is skeletal muscle called striated muscle ?

Answer 22

Because the regular arrangement of myofilament creates a pattern of light and dark bands

Question 23

What is the functional unit of a muscle called ?

Answer 23

A saromere

Question 24

What is a sarcomere bordered by ?

Answer 24

Z lines

Question 25

Where to thin filaments attach ?

Answer 25

Z lines

Question 26

What is the sliding filament model of muscle contraction ?

Answer 26

Thin and thick filaments ratchet past each other longitudinally, powered by the myosin muscles

Question 27

What is the structure of myosin ?

Answer 27

A long tail region and a globular head region

Question 28

Where does the head of the myosin molecule bind to ?

Answer 28

An actin filament

Question 29

What does the head of the myosin molecule binding to an actin filament form ?

Answer 29

A cross bridge

Question 30

What does the head of the myosin molecule binding to an actin filament do ?

Answer 30

Pull the thin filament towards the centre of the sarcomere-the power stroke

Question 31

What does muscle contraction require ?

Answer 31

Repeated cycles of binding and release - cross bridge cycling

Question 32

What is muscle contraction dependent on ?

Answer 32

ATP

Question 33

Why does muscle fatigue ?

Answer 33

Metabolic reasons: lack of substrate (ATP) or accumulation of metabolites that interere with contraction

Question 34

What generates the ATP needed for muscle contraction ?

Answer 34

Glycolysis and aerobic respiration

Question 35

What happens during intense muscle activity ?

Answer 35

02 becomes limiting and ATP is generated by lactic acid fermentation

Question 36

Does cardiac muscle fatigue ?

Answer 36

No

Question 37

What else is muscle contraction dependent on ?

Answer 37

Calcium

Question 38

What binds to actin strands on thin filaments when a muscle fibre is at rest ?

Answer 38

The regulatory protein tropomyosin and the troponin complex

Question 39

What prevents myosin and actin interacting ?

Answer 39

The regulatory protein tropomyosin and the troponin complex

Question 40

What must happen for a muscle fibre to contract ?

Answer 40

Myosin binding sites must be exposed

Question 41

When are myosin binding sites exposed ?

Answer 41

When calcium ions bind to troponin complex

Question 42

When does contraction occur ?

Answer 42

When the concentration of calcium is high

Question 43

When does muscle contraction stop ?

Answer 43

When the calcium ion concentration is low

Question 44

What is the stimulus leading to muscle contraction of a muscle fibre ?

Answer 44

An action potential in a motor neuron that makes a synapse with the muscle fibre

Question 45

What does the synaptic terminal of the motor neuron do ?

Answer 45

Releases the neurotransmitter acetylcholin

Question 46

What is the function of acetylcholine in skeletal muscle contraction ?

Answer 46

Depolarises the muscle causing it to produce and end plate potential

Question 47

Where do action potentials travel ?

Answer 47

To the interior of the muscle fibre along transverse tubules

Question 48

What does the traveling of the action potential to the interior of muscle fibres do ?

Answer 48

Causes the sarcoplasmic reticulum to release calcium ions

Question 49

Is the contraction of the whole muscle graded ?

Answer 49

Yes

Question 50

How does the nervous system produce graded contractions ?

Answer 50

1. Varying the number of fibres that contract | 2. Varying the rate at which fibres are stimulated

Question 51

What may each motor neuron synapse with ?

Answer 51

Multiple muscle fibres

Question 52

What does a motor unit consist of ?

Answer 52

A single motor neuron and all the muscle fibres it controls

Question 53

What is tetanus ?

Answer 53

Describes sustained muscle contraction, where a muscle doesn't relax between contractions

Question 54

What are some examples of disorders related to skeletal muscle ?

Answer 54

1. Amyotrophic lateral sclerosis 2. Myasthenia gravis 3. Multiple sclerosis 4. Duchenne muscular dystrophy

Question 55

How is ALS caused ?

Answer 55

Interferes with the excitation of skeletal muscle fibers

Question 56

What is myasthenia gravis ?

Answer 56

An autoimmune disease that attack acetylcholine receptors on muscle fibres

Question 57

What is multiple sclerosis ?

Answer 57

Demyelinating disease

Question 58

What does cardiac muscle consist of ?

Answer 58

Striated cells electrically connected by intercalated disks that contain gap junctions

Question 59

What can cardiac muscle do ?

Answer 59

Generate action potentials without neural input

Question 60

Do cardiac muscles have tetanic contraction ?

Answer 60

No

Question 61

Where is smooth muscle found ?

Answer 61

Mainly in walls of hollow organs such as circulatory system, digestive and reproductive

Question 62

What is slow in smooth muscle ?

Answer 62

Contractions - may be initiated by muscles themselves

Question 63

What can contractions be caused by in smooth muscle ?

Answer 63

Stimulation from neurons in the autonomic nervous system

Question 64

Why does smooth muscle lack striated ?

Answer 64

Actin and myosin are not regularly arrayed

Question 65

How does calcium enter smooth muscle ?

Answer 65

They enter the cytosol through smooth muscle

Question 66

What is muscle contraction regulated by in smooth muscle ?

Answer 66

Calcium ions

Question 67

How would you build skeletal muscle ?

Answer 67

1. Testosterone | 2. Anabolic steroids

Question 68

What is the building of muscle dependent on ?

Answer 68

Protein synthesis

Question 69

What does lack of muscle lead to ?

Answer 69

Atrophy

Question 70

What can the heart undergo in response to physiological stimulus ?

Answer 70

Changes in shape and mass

Question 71

How does endurance training effect the heart ?

Answer 71

Increases the volume

Question 72

How does resistance training effect the heart ?

Answer 72

Increase in mass