Muscles

Question 1

3 types of muscle - which are striated?

Answer 1

Skeletal - striated
Cardiac - striated
Smooth - non-striated

Question 2

Myoglobin

Answer 2

Protein with similar structure to a single subunit of Hb - an O2 storage molecule, providing O2 to working striated muscles.

Higher affinity for O2 than Hb - gives up O2 in muscles, especially in low pH.

Released into bloodstream (myoglobinaemia) when striated muscle dies or damaged (necrosis or rhabdomyolysis).

Can cause renal damage - removed by kidneys into urine (myoglobinuria) - tea coloured urine.

Question 3

Rhabdomyolysis

Answer 3

Muscle damage

Question 4

Myoglobinaemia

Answer 4

Myoglobin in blood.

Question 5

Myoglobinuria

Answer 5

Myoglobin in urine.

Question 6

Sarcolemma

Answer 6

Outer membrane of muscle cell.

Question 7

Sarcophagi

Answer 7

Cytoplasm of muscle cell

Question 8

Sarcosome

Answer 8

Mitochondrion

Question 9

Sarcomere

Answer 9

Contraction unit in striated muscle

Question 10

Sarcoplasmic reticulum

Answer 10

Smooth ER of muscle cell

Question 11

Myofibril structure (sarcomere)

Answer 11

Dark A band - H zone in centre, M line in centre of this
Light I band - Z band in centre

Question 12

Skeletal muscle structure

Answer 12

Many myofibrils make muscle fibre (sarcolemma).
- muscle fibres surrounded by endomysium

Many muscle fibres make fascicle.
- fascicle surround by perimysium

Many fascicles make muscle, as well as blood vessels.
- muscle surrounded by epimysium

Question 13

Tropomyosin

Answer 13

Stabilises structure of contraction unit.

Question 14

Muscle contraction speeds

Answer 14

Slow, fast, intermediate

Question 15

Muscle fibre types

Answer 15

Type 1 - slow twitch fibres (slow oxidative)

Type 2a - fast twitch fibres (fast oxidative glycolytic)

Type 2b - fast twitch fibres (fast glycolytic)

Question 16

Type 1 fibres:
Capillary supply?
Aerobic/anaerobic?
Myoglobin levels?
Number of mito?
Number of cytochromes?
Colour?
How fast do they fatigue?
What type of activities are they used in?
Examples of actions

Answer 16

Rich capillary supply
Aerobic
High myoglobin levels
Many mito
Many cytochrome
Red in colour
Fatigue resistant
Endurance type activities
Standing/walking

Question 17

Type 2a:
Capillary supply?
Aerobic/anaerobic?
Myoglobin levels?
Number of mito?
Number of cytochromes?
Colour?
How fast do they fatigue?
What type of activities are they used in?
Examples of actions

Answer 17

Rich capillary supply
Aerobic
High myoglobin levels
Many to intermediate no. of mito
Many cytochromes
Red to pink
Moderate fatigue resistance
Assist type 1 and 2b activities
Standing/walking (recruited 2nd)

Question 18

Type 2b:
Capillary supply?
Aerobic/anaerobic?
Myoglobin levels?
Number of mito?
Number of cytochromes?
Colour?
How fast do they fatigue?
What type of activities are they used in?
Examples of actions

Answer 18

Poor capillary supply
Anaerobic
Low myoglobin levels
Few mito
Few cytochromes
White (pale)
Rapidly fatigue
Strength/anaerobic type activities
Standing/walking - recruited last
Jumping/running/sprinting

Question 19

What are cytochromes?

Answer 19

Haemoproteins that functions as an electron shuttle in ETC - therefore more mito = more cytochromes.

Question 20

What ion does continued muscle contraction rely on? + what energy molecule also needed?

Answer 20

Ca2+ ions (and ATP)

Question 21

How do cardiac muscles look under the microscope?

Answer 21

Striated
Centrally positioned nucleus (1 or 2 per cell)
Intercalated discs
Branching

Question 22

ANP

Answer 22

Atrial natriuretic peptide
Released by atria during heart failure
Specifically congestive heart failure

Question 23

BNP

Answer 23

Brain-type natriuretic peptide
Released by ventricles
Specifically left ventricular hypertrophy, mitral valve disease

Question 24

Hypertrophy

Answer 24

Cells increase in size

Question 25

Hyperplasia

Answer 25

Cells increase in number

Question 26

Smooth muscle - histology

Answer 26

Spindle shaped
Single central large nucleus
Form sheets, bundles or layers
Multiple adjacent capillaries
Very tightly packed

Question 27

How are smooth muscle cells joined?

Answer 27

Gap junctions

Question 28

Where is smooth muscle found?

Answer 28

Contractile walls of passageways/cavities
Involuntary muscle
- means it can cause high BP; painful menstruation; lung disease; abnormal gut mobility; incontinence

Eg small intestine

Question 29

Is muscle repair possible?
- skeletal, cardiac, smooth

Answer 29

Skeletal:
Cannot divide - regenerate by mitotic activity of satellite cells so that hyperplasia follows muscle injury.

Cardiac:
Adult tissue generally considered to be incapable of regeneration
Damage - fibroblasts invade, divide and lay down scar tissue

Smooth:
Retain mitotic activity and can form new smooth muscle cells - very good at repairing themselves

Question 30

What does it mean for a muscle to act as a syncytium?

Which muscle types do this?

Answer 30

Means wave-like function

Cardiac and smooth muscle do this

Question 31

Satellite cells

Answer 31

Precursor cells to skeletal muscle cells - responsible for ability of smooth muscle to regenerate.

Question 32

Neuromuscular junction - what is it? What neurotransmitter is used?

How does its action work?

Answer 32

Small terminal swellings of the axons.
Acetylcholine

Nerve impulse releases acetylcholine; binds to receptors on sarcolemma; initiates an action potential which is propagated along the muscle.

Question 33

What is a kranocyte?

Answer 33

A connective tissue cell that resides over the terminal Schwann cell.

Functions not fully known, thought to anchor the nerve to the muscle cell.

Question 34

What is myosin?