session 8-muscle,contraction,structure,disease

Question 1

which type(s) of muscle is voluntary and which is involuntary?

Answer 1

voluntary-skeletal

involuntary-cardiac and smooth

Question 2

which muscle is striated/non striated?

Answer 2

striated=cardiac and skeletal

non striated=smooth

Question 3

draw the ultrastructure of muscle, in terms of bands/zones and state which contains actin and myosin.

Answer 3

see notes on penultimate

Question 4

draw the sliding filament model

Answer 4

see notes on penultimate

Question 5

what are the names of the 3 types of muscle?

Answer 5

cardiac,skeletal and smooth

Question 6

what is a satellite cell?

Answer 6

precursor to muscle cells

Question 7

how does skeletal muscle repair itself?

Answer 7

• tissue regenerates by mitotic activity of satellite cells, so that hyperplasia ( multiplication of cells) follows muscle injury
• satellite cells can also fuse with existing muscle cells, increasing mass (skeletal muscle hypertrophy)
• large damage repaired by connective tissue which leaves scar
• decrease in nerve or blood supply causes muscle fibre degeneration and replaced by fibrous tissue

Question 8

how does cardiac muscle repair itself?

Answer 8

• cannot regenerate

- after damage, fibroblasts lay down scar tissue

Question 9

how does smooth muscle repair itself?

Answer 9

-cells undergo mitosis and can form new smooth muscle cells

Question 10

in cardiac muscle cells, what kind of position do the nuclei take up and how many nuclei are present in each cell?

Answer 10

central and 1 or 2 nuclei per cell

Question 11

what kind of discs does the cardiac muscle contain?

Answer 11

intercalated

Question 12

the T tubules in cardiac muscle are in line with which band(s)?

Answer 12

z bands

Question 13

what band(s) are the t tubules in line with in skeletal muscle?

Answer 13

the A to i band junction

Question 14

in smooth muscle cells, where are the nuclei located and how many nuclei are there per cell?

Answer 14

central and one per cell

Question 15

what 3 features of large purkinje cell fibres make them suitable for their job of rapidly conducting action potentials, enabling the ventricles to contract in a synchronous manner?

Answer 15

• abundant glycogen
• sparse myofilaments
• extensive gap junction sites

Question 16

what happens to muscle fibres in disuse atrophy?

Answer 16

-shrink and weaken

Question 17

what natural process causes muscle atrophy and what is the medical term?

Answer 17

ageing

SARCOPENIA

Question 18

what is myasthenia gravis?

Answer 18

autoimmune destruction of end plate ACh receptors by antibodies
-loss of junctional folds at end plate (less SA for receptors)
-widening of synaptic cleft (slower diffusion rate of ACh)
PROBLEM: when affecting respiratory muscle

Question 19

Describe 3 symptoms of myasthenia gravis.

Answer 19

• Fatigue and sudden falling
• drooping eyelids (can be treated with ice-inhibits acetylcholinesterASE activity)
• double vision

Question 20

how do you treat myasthenia gravis?

Answer 20

acetylcholinesterase inhibitors
Immune suppressants
Plasmapheresis-removal of harmful antibodies
Thymectomy

Question 21

how does botox disrupt neuromuscular transmission?

Answer 21

stops ACh release

Question 22

how does organophosphate affect neuromuscular transmission?

Answer 22

irreversibly inhibits acetylcholinesterase

• ACh remains in receptors
• muscle stays contracted

Question 23

Describe WHY muscular dystrophy occurs.

Answer 23

• organ or tissue wastes away (can be through atrophy)
• genetic fault causing absence of certain proteins that anchor actin filaments to sarcolemma
• during contraction, muscle fibre tears apart

Question 24

In duchenne muscular dystrophy, what is the name of the protein that is completely absent and so cannot perform its role of binding actin to the sarcolemma?

Answer 24

dystrophin

Question 25

why do blood creatine kinase levels rise with DMD?

Answer 25

muscle cells open as they tear and so creatine kinase leaks into blood (blood test to diagnose DMD)

Question 26

what is pseudohypertrophy?

Answer 26

muscles become swollen with deposits of fat and fibrous tissue

Question 27

one symptom of DMD is gower’s sign:what is this?

Answer 27

using hands and knees to stand up from squat position-loss of proximal muscle strength

Question 28

what kind of disorder is malignant hyperthermia?

Answer 28

rare,autosomal dominant

Question 29

what sparks malignant hyperthermia?

Answer 29

general anaesthetic drugs

Question 30

what does succinylcholine do and does it act competitively or non competitively?

Answer 30

inhibits ACh activity by binding non competitively on receptors

Question 31

what is succinylcholine broken down with?(degraded slower than ACh)

Answer 31

butyrylcholinesterase

Question 32

what does malignant hyperthermia do in skeletal muscle?

Answer 32

uncontrolled increase in skeletal muscle oxidative metabolism-overwhelms bodies capacity to supply O2,remove CO2 and regulate
-leads to death

Question 33

what drug is used to treat malignant hyperthermia?

Answer 33

dantrolene=muscle relaxant by preventing calcium release

Question 34

What does the peri,Epi and endomysium contain?

Answer 34

Connective tissue, blood vessels and nerves

Question 35

What protein is a useful marker for cardiac ischaemia?

Answer 35

Troponin

Question 36

What is rigormortis?

Answer 36

Stiffening of joints and muscles in body, shortly after death

Question 37

What 2 things happen in DMD after muscle fibres tear?

Answer 37

Calcium enters and causes necrosis

Pseudohypertrophy-swelling before fat and connective tissue replace muscle fibres

Question 38

What type of inheritance is DMD?

Answer 38

X linked recessive