Structure of Skeletal, Cardiac and Smooth Muscle

Question 1

What enables body movement ?

Answer 1

Skeletal muscle contraction

Question 2

What enables body posture ?

Answer 2

Continual adjustments of skeletal muscles

Question 3

What enables support and protection ?

Answer 3

Skeletal muscles

e.g. surrounding joints and within the abdominal wall

Question 4

What enables sphincter control ?

Answer 4

Skeletal and Smooth muscle - cardiac sphincter in stomach; bladder; anus

Question 5

What enables movement of food along the GIT ?

Answer 5

Smooth muscle generates peristalsis

Question 6

What enables regulation of blood flow ?

Answer 6

Cardiac muscle pumps blood
Smooth muscle in vessel walls regulate blood flow

Question 7

What enables temperature regulation ?

Answer 7

Skeletal muscle - shivering
Smooth muscle - erection of hairs

Question 8

Name the 4 characteristics of ALL muscle

Answer 8

Excitability
Contractility
Extensibility
Elasticity

Question 9

What is meant by excitability ?

Answer 9

Responsive to stimuli

i.e. a chemical signal such as a neurotransmitter

Question 10

What is meant by contractility ?

Answer 10

Ability to shorten forcibly when adequately stimulated

Question 11

Concentric contraction

Answer 11

Muscle shortens

Question 12

Eccentric contraction

Answer 12

Muscle is stretched

Question 13

Isometric contraction

Answer 13

Muscle contracts but does not shorten

Question 14

What is meant by extensibility ?

Answer 14

Can extend beyond their resting/relaxed length

Question 15

What is meant by elasticity ?

Answer 15

Recoil and resume its resting length after stretching

Question 16

State the common features of all muscle

Answer 16

Actin and myosin
Use of ATP
Calcium ions
Stimulation

Question 17

Function of actin and myosin

Answer 17

Generate force for contraction

Question 18

How is ATP generated ?

Answer 18

generated via respiration

• Aerobic oxidative respiration
• Anaerobic glycolytic respiration

Question 19

Function of calcium ions

Answer 19

Needed for activation of contraction

Question 20

Function of stimulation

Answer 20

Need an action potential from a neuron

Question 21

What % of muscle protein does actin and myosin make up ?

Answer 21

around 90%

Question 22

What are actin and myosin ?

Answer 22

They are both enzymes :

ATPases - hydrolyse ATP –> ADP + Pi

Question 23

Describe some muscle cell components

Answer 23

Cell membrane - sacrolemma
Cytoplasm - sacroplasm
Nuclei, organelles …

Full of myofibrils - actin/myosin

Many mitochondria
Extensive sarcoplasmic reticulum

Question 24

Function of transverse T tubules

Answer 24

Brings action potentials into interior of muscle fibre

Question 25

Briefly describe skeletal muscle

Answer 25

640 muscles : 40% of body mass Attached to the skeleton via tendons Voluntary and reflexive control Sporadic and continual contraction

Question 26

Describe skeletal muscle cells

Answer 26

Large multinucleate cells (100micrometres - 60mm)

Question 27

State the 3 layers that form the tendons

Answer 27

Epimysium - outer Perimysium - middle Endomysium - innermost

Question 28

What in the function of the 3 layers ?

Answer 28

They are connective tissue which covers and supports muscle. Maintains structural integrity

Question 29

Myocyte

Answer 29

A single muscle cell, containing myofilaments

Question 30

Myofilament

Answer 30

Contractile units called SARCOMERES

Question 31

What are myofilaments composed of ?

Answer 31

Actin and Myosin

Question 32

Fasicle

Answer 32

Grouping of elongated bundles of muscle fibres (cells)

Question 33

Endomysium

Answer 33

Separates the muscle fibres

Question 34

Perimysium

Answer 34

Loose collagenous connective tissue that surrounds fascicles

Question 35

Epimysium

Answer 35

Dense collagenous sheath that surrounds gross muscle.

Question 36

Briefly describe cardiac muscle

Answer 36

Can contract without stimulation - auto-rhythmic Involuntary muscle : ANS Branched cells

Question 37

Describe cardiomyocytes

Answer 37

- Striated - Small - Uni or Bi-nucleated - Large number of mitochondria (25-30% of cell volume) - Aerobic respiration : can use multiple fuel sources - Intercalated discs : gap junctions / desmosomes

Question 38

What are GAP junctions ?

Answer 38

They are formed by connexions - 6 subunits/channel Sites of low electrical resistance They electrically connect cells

Question 39

Function of GAP junctions in cardiac muscle

Answer 39

Electrically links cardiomyocytes - allows diffusion of ions Cells of the myocardium contract as a unit (ALL or nothing)

Question 40

State the 7 places where smooth muscle is found

Answer 40

Blood vessels Digestive tract Bladder wall / urinary tract Respiratory tract Reproductive tract Eyes Skin

Question 41

Briefly describe smooth muscle cells

Answer 41

Small - 100-200 micrometers in length Spindle shaped cells arranged into sheets Less regularly organised NO striations Single nucleus Involuntary - ANS, hormones and stretch

Question 42

Describe the structural organisation of smooth muscle

Answer 42

Longitudinal and Circular layer

Question 43

Difference between smooth muscle and cardiac/ skeletal muscle

Answer 43

Smooth muscle has a slower contraction rate and a longer duration than cardiac or skeletal muscle.

Question 44

Describe actin and myosin in smooth muscle

Answer 44

Actin and myosin anchored via dense bodies throughout the sarcoplasm. Focal adhesions structurally connect cells

Question 45

Summary of skeletal muscle

Answer 45

Size - LARGE ( up to 60cm) Shape - Regular parallel myofibres Striations - Yes Nuclear content - Multinucleated Intercalated discs - NO Gap junctions - NO Control - Voluntary (via motor neurons and reflexive) Metabolism - Aerobic and anaerobic

Question 46

Summary of cardiac muscle

Answer 46

Size - Small (50-100 micrometers) Shape - Branched Striations - Yes Nuclear content - 1/2 nuclei Intercalated discs - Yes Gap junctions - Yes Control - Involuntary (via AND hormones and stretch) Metabolism - Aerobic

Question 47

Summary of smooth muscle

Answer 47

Size - Small (30-200 micrometers) Shape - Spindle Striations - No Nuclear content - single nuclei Intercalated discs - No Gap junctions - Yes Control - Involuntary (via AND hormones, local chemicals and stretch) Metabolism - Mainly aerobic