2: Muscle Physiology I

Question 1

What are some physiological functions of skeletal muscle?

Answer 1

Posture

Voluntary and involuntary movement (inc. respiratory movement)

Heat production

Transport of metabolites between organs (whole body metabolism)

Question 2

What are the three types of muscle?

Answer 2

Cardiac muscle

Skeletal muscle

Smooth muscle

Question 3

Muscle is the largest type of ___ in the body.

Answer 3

tissue

Question 4

What function do all three types of muscle have in common?

Answer 4

Produce tension and movement through CONTRACTION

Question 5

Which types of muscle are striated?

Answer 5

Cardiac muscle

Skeletal muscle

Question 6

Which type of muscle is unstriated?

Answer 6

Smooth muscle

Question 7

How is striation recognised under a microscope?

Answer 7

Alternating light (actin) and dark (myosin) bands

Question 8

Which division of the nervous system innervates skeletal muscle?

Answer 8

Somatic nerves

Question 9

Skeletal muscle is (voluntary / involuntary).

Answer 9

voluntary

Question 10

Which division of the nervous system innervates involuntary cardiac and smooth muscle?

Answer 10

Autonomic nervous system

Question 11

Initiation of contaction in skeletal muscle is ___genic.

Answer 11

neurogenic

Question 12

Skeletal muscle is arranged into ___ units.

Answer 12

motor

Question 13

Are skeletal muscle cells joined by gap junctions?

Answer 13

No

one neuromuscular junction between motor neuron and motor unit

Question 14

Does skeletal muscle have gap junctions?

Answer 14

No

Question 15

Which ion triggers contraction of skeletal and cardiac muscle?

Answer 15

Ca²⁺

Question 16

What is the only source of Ca²⁺ in skeletal muscle?

Answer 16

Sarcoplasmic reticulum

Question 17

What two factors control the “power” of skeletal muscle contraction?

Answer 17

Motor unit recruitment i.e how many muscle fibres are contracting?

Summation of contractions i.e are contractions being reactivated rapidly?

Question 18

There is no continuity of ____ between nerve and skeletal muscle cells.

Answer 18

cytoplasm

Question 19

What is the neurotransmitter found at neuromuscular junctions?

Answer 19

Acetylcholine

Question 20

What is a motor unit?

Answer 20

A single alpha motor neuron and ALL the skeletal muscle fibres it innervates

Question 21

The excitation of one alpha motor neuron will stimulate the contraction of (one / multiple) motor units(s).

Answer 21

multiple units

Question 22

What affects the number of motor units served by an alpha motor neuron?

Answer 22

Function of the muscle

Question 23

Muscles which serves fine, precision movements (give examples) are have (more / fewer) muscle fibres.

Answer 23

Eye movements

Facial expression

Hand movements

FEWER FIBRES

Question 24

Muscles which have powerful functions have (more / fewer) muscle fibres.

Answer 24

more

e.g limb movements

Question 25

A muscle fibre is made up of how many cells?

Answer 25

**One cell**

Question 26

A **motor unit** encompasses all the ___ \_\_\_ supplied by an ___ \_\_\_ \_\_\_.

Answer 26

**muscle fibres** **alpha motor neuron**

Question 27

What are the specialised contractile elements found within skeletal muscle cells?

Answer 27

**Myofibrils**

Question 28

What is the functional unit of a myofibril?

Answer 28

**Sarcomere**

Question 29

Name the two proteins found in a sarcomere, what colour they appear on microscopy and why?

Answer 29

**Actin** - light - thinner filaments **Myosin** - dark - thicker filaments

Question 30

Skeletal muscle fibres are **(parallel / divergent)**.

Answer 30

**parallel**

Question 31

By which structures are skeletal muscle fibres attached to bones?

Answer 31

**Tendons**

Question 32

Each muscle fibre contains many \_\_\_.

Answer 32

**myofibrils**

Question 33

Myofibrils have alternating segments of which two proteins?

Answer 33

**Actin** **Myosin**

Question 34

Within myofibrils, actin and myosin filaments are arranged into \_\_\_.

Answer 34

**sarcomeres**

Question 35

What is the definition of an organ's functional unit? What is the functional unit of skeletal muscle?

Answer 35

**Smallest component capable of performing all the organ's functions** **Sarcomere**

Question 36

What are **Z lines**?

Answer 36

Boundary lines splitting up sarcomeres

Question 37

What are **A bands**?

Answer 37

**Sections of overlapping actin and myosin filaments**

Question 38

What are **H zones**?

Answer 38

**Lighter area in the middle of A bands where actin doesn't overlap - myosin only**

Question 39

What are **M lines**?

Answer 39

**Line extending down the centre of the A band, right in the middle of the H zone**

Question 40

What are **I bands**?

Answer 40

**Remaining area of sarcomere where only actin is found**

Question 41

What is required for the sliding of myosin and actin filaments, which itself produces muscle contraction?

Answer 41

**ATP**

Question 42

What binds to the myosin head to trigger detachment from the actin fibre?

Answer 42

**ATP**

Question 43

Even if ATP is present, binding of the myosin head to a new section of actin filament will not occur without?

Answer 43

**Ca**²⁺

Question 44

Why does rigor mortis occur?

Answer 44

No ATP present, so myosin head remains attached to actin fibre

Question 45

Nerves generate an ___ \_\_\_, which travels to the ___ \_\_\_ junction and then to the skeletal muscle fibres.

Answer 45

**action potential** **neuromuscular junction**

Question 46

What is **excitation contraction coupling**?

Answer 46

Process by which **surface action potential** triggers **contraction of skeletal muscle**

Question 47

In skeletal muscle, where is Ca²⁺ released from?

Answer 47

**Sarcoplasmic reticulum**

Question 48

What structures are extensions of the surface membrane and invaginate into muscle cells, allowing surface action potentials to reach the sarcoplasmic reticulum?

Answer 48

**T-tubules**

Question 49

Ca²⁺ is released by which specific part of the sarcoplasmic reticulum?

Answer 49

**Lateral sacs**

Question 50

The myosin-binding sites on actin filaments are covered by which protein complex?

Answer 50

**Troponin-tropomyosin complex**

Question 51

When Ca²⁺ binds to the troponin-tropomyosin complex, what happens?

Answer 51

**Conformational change, complex moves and allows myosin to form cross bridge with actin**

Question 52

After an action potential, Ca²⁺ is **(passively / actively)** reabsorbed into the sarcoplasmic reticulum.

Answer 52

**actively** requiring ATP ATP is also required for cross bridge detachment

Question 53

ATP is required for **(contraction / relaxation)** of skeletal muscle.

Answer 53

**both**