Lecture 17

Question 1

Give the muscle related words and their meanings?

Answer 1

Myopathy= muscle disease

Myasthenia= muscle weakness

Myoclonus= muscle spasm

Myocardium= muscular component of heart

Myalgia= muscle pain

Question 2

What characterises smooth muscle?

Answer 2

It is not striated and has no nerve to muscle communication

Question 3

What is myoglobin?

Answer 3

Red protein similar to a single haemoglobin subunit. At low pH haemoglobin will give oxygen to myoglobin.

When striated muscle dies (necrosis)myoglobin is release into bloodstream known as myoglobinuria (after marathon with no training). Causes renal damage and removed by kidney to I’ve tea coloured urine.

Question 4

Explain muscle cell component terminology?

Answer 4

Sarcolemma- outer membrane of muscle cell

Sarcoplasm- cytoplasm of muscle cell

Sarcomere- contraction unit in striated muscle

Sarcosome- mitochondrion in muscle

Sarcoplasmic reticulum- smooth endoplasmic reticulum of muscle

Question 5

Difference between endomysium, perimysium and epimysium?

Answer 5

Endomysium found between fibres, perimysium found around fascicles and epimysium found surrounding muscle

Question 6

What’s the difference between the origin and the insertion?

Answer 6

Origin is fixed at the tendon while the insertion moves with contraction

Question 7

What is the difference between intrinsic and extrinsic muscle?

Answer 7

Intrinsic for example would be within the tongue and would allow it to change shape for swallowing etc. Extrinsic muscles would retract it or move it from side to side

Question 8

How is skeletal muscle structured

Answer 8

Myofibrils in a muscle cell or fibre surrounded by an endomysium and many of these make a fascicle surrounded by a perimysium and many of these make a muscle surrounded by an epimysium

Question 9

What is a myofibril made of?

Answer 9

Actin and myosin filaments

Question 10

What is a sarcomere?

Answer 10

Part of a myofibirl that forms the basic unit of striated muscle tissue

Question 11

Can you label the zones of a sarcomere?

Answer 11

See lecture

Question 12

What are T tubules?

Answer 12

Extension of sarcolemma that project into skeletal and cardiac muscle

Question 13

Where are sarcosomes located

Answer 13

Between the myofibrils and have peripherally positioned nuclei

Question 14

Where is a sarcomere measured form?

Answer 14

Z band to z band

Question 15

What types of muscle fibres are there

Answer 15

Fast, slow and intermediate

Question 16

What are the types of slow and fast twitch fibres

Answer 16

Slow type 1 oxidative

Fast type 2A oxidative

Fast type 2B glycolytic

Question 17

How to tell muscle fibre types from each other?

Answer 17

1a red, 2A red to pink 2B pale

2B glycolytic fibres used for strength training sprinting etc

Question 18

How to easily identify cardiac muscle?

Answer 18

Intercalated disks and branching

Question 19

Some differences between skeletal and cardiac muscle?

Answer 19

Nuclei central in cardiac peripheral in skeletal

Cardiomyocytes communicate through gap junctions in T tubules

Question 20

What hormones does the heart produce?

Answer 20

Atrial nuturietic factor and brain-type naturietic factor. Released during heart failure to make pumping easier by reducing vascular resistance

Question 21

Hypertrophy vs hyperplasia?

Answer 21

Hypertrophy is an increase in cell size hyperplasia is an increase in cell number

Question 22

Atrophy vs hypertrophy

Answer 22

Atrophy cells smaller hypertrophy cells larger

Question 23

Function of Purkinje fibres?

Answer 23

Rapid signal transduction which enables ventricles to contact in a synchronous manner

Question 24

Smooth muscle?

Answer 24

Tapered ends and spindle shaped

Slower and sustained contraction

Can be stretched

Single large nucleus that is central

Question 25

Clinical relevance of smooth muscle?

Answer 25

Involuntary and so can be hard to control eg high blood pressure asthma etc

Question 26

How are smooth muscle cells innvervated?

Answer 26

Autonomic nervous system sends signal to varicosities which release neurotransmitter into synaptic cleft

Question 27

How to identify smooth muscle?

Answer 27

Long flat cells with long and flat nuclei when relaxed

Question 28

Mature muscle repair?

Answer 28

Skeletal- cannot divide but satellite cells can go through mitosis to make more muscle cells- hyperplasia

Cardiac- cannot regenerate, fibroblasts lay down scar tissue

Smooth- can regenerate eg endometrium

Question 29

Where would you find fast and slow contracting muscle fibres?

Answer 29

Fast in eye, slow in back