session 8-muscle,contraction,structure,disease Flashcards
which type(s) of muscle is voluntary and which is involuntary?
voluntary-skeletal
involuntary-cardiac and smooth
which muscle is striated/non striated?
striated=cardiac and skeletal
non striated=smooth
draw the ultrastructure of muscle, in terms of bands/zones and state which contains actin and myosin.
see notes on penultimate
draw the sliding filament model
see notes on penultimate
what are the names of the 3 types of muscle?
cardiac,skeletal and smooth
what is a satellite cell?
precursor to muscle cells
how does skeletal muscle repair itself?
- 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
how does cardiac muscle repair itself?
- cannot regenerate
- after damage, fibroblasts lay down scar tissue
how does smooth muscle repair itself?
-cells undergo mitosis and can form new smooth muscle cells
in cardiac muscle cells, what kind of position do the nuclei take up and how many nuclei are present in each cell?
central and 1 or 2 nuclei per cell
what kind of discs does the cardiac muscle contain?
intercalated
the T tubules in cardiac muscle are in line with which band(s)?
z bands
what band(s) are the t tubules in line with in skeletal muscle?
the A to i band junction
in smooth muscle cells, where are the nuclei located and how many nuclei are there per cell?
central and one per cell
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?
- abundant glycogen
- sparse myofilaments
- extensive gap junction sites
what happens to muscle fibres in disuse atrophy?
-shrink and weaken
what natural process causes muscle atrophy and what is the medical term?
ageing
SARCOPENIA
what is myasthenia gravis?
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
Describe 3 symptoms of myasthenia gravis.
- Fatigue and sudden falling
- drooping eyelids (can be treated with ice-inhibits acetylcholinesterASE activity)
- double vision
how do you treat myasthenia gravis?
acetylcholinesterase inhibitors
Immune suppressants
Plasmapheresis-removal of harmful antibodies
Thymectomy
how does botox disrupt neuromuscular transmission?
stops ACh release
how does organophosphate affect neuromuscular transmission?
irreversibly inhibits acetylcholinesterase
- ACh remains in receptors
- muscle stays contracted
Describe WHY muscular dystrophy occurs.
- 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
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?
dystrophin
why do blood creatine kinase levels rise with DMD?
muscle cells open as they tear and so creatine kinase leaks into blood (blood test to diagnose DMD)
what is pseudohypertrophy?
muscles become swollen with deposits of fat and fibrous tissue
one symptom of DMD is gower’s sign:what is this?
using hands and knees to stand up from squat position-loss of proximal muscle strength
what kind of disorder is malignant hyperthermia?
rare,autosomal dominant
what sparks malignant hyperthermia?
general anaesthetic drugs
what does succinylcholine do and does it act competitively or non competitively?
inhibits ACh activity by binding non competitively on receptors
what is succinylcholine broken down with?(degraded slower than ACh)
butyrylcholinesterase
what does malignant hyperthermia do in skeletal muscle?
uncontrolled increase in skeletal muscle oxidative metabolism-overwhelms bodies capacity to supply O2,remove CO2 and regulate
-leads to death
what drug is used to treat malignant hyperthermia?
dantrolene=muscle relaxant by preventing calcium release
What does the peri,Epi and endomysium contain?
Connective tissue, blood vessels and nerves
What protein is a useful marker for cardiac ischaemia?
Troponin
What is rigormortis?
Stiffening of joints and muscles in body, shortly after death
What 2 things happen in DMD after muscle fibres tear?
Calcium enters and causes necrosis
Pseudohypertrophy-swelling before fat and connective tissue replace muscle fibres
What type of inheritance is DMD?
X linked recessive
