muscle tissue - function and disease Flashcards
cardiac vs smooth muscle
cardiac= electrical conduction, uses intercalated discs and has striations smooth = no striation, no troponin and a different type of contraction
explain process of cardiac contraction
vagus nerve- parasympathetic and deceleration. cardiac nerve- sympathetic and acceleration. the neurotransmitter is released into a large gap reaching all cells so there is simultaneous contraction
from where is the neurotransmitter released in smooth muscle contraction
neurotransmitter is related from varicosities which is arranged over entire smooth muscle structure so when its released all the cells are reached
explain the process of smooth muscle contraction
IP3 acts as second messenger for release of ca2+. This binds to calmodulin causing smooth muscle to contract from circular to linear. contraction continues but no ca2+ needed
explain the contraction of skeletal muscle
1) nerve impulse = Act release
2) conc of Na+ increases resulting in depolarisation
3) ca2+ ion are released from SER
4) ca2+ bind to troponin being myosin heads are able to bind to actin
= contraction
what does less fibres in a muscle mean
more fine control and therefore more fibres means more power
what is myesthenia gravis
results in weakness of the eyelid. is an autoimmune disease where antibodies block ach receptors. there are therefore less receptors and ‘invaginations” are reduced. = reduced synaptic transmission
explain the sliding filament theory
1) ca bound to troponin means it teaches so myosin and actin bind
2) ADP and Pi are related during the power stroke
3) ATP binds and cross bridge detaches
4) ATP is hydrolysed by ATPase and ADP is now attached instead
what happens to actin and myosin length during contraction
they remain the same its the sarcomere length that shorten
what is compartment syndrome
fascia keep things in compartments but trauma may cause internal bleeding in one compartment which exerts pressure on blood vessels and nerves
symptoms of compartment syndrome
deep pain, parasethsia (pins and needles), swollen shiny skin, feels tense and firm
how is compartment syndrome treated
doing a fasciotomy where its opened to release pressure and then later covered with skin graft
what is muscle tone regulated by
motor neurone activity, muscle elasticity, use and gravity. healthy muscles are never fully relaxed so they are ready to relax which improves with the more exercise you do
what is muscle hypertrophy
when replacement of proteins is greater than their destruction. new fibrils are produced and sarcomeres are added.
1 example of why hypertrophy occurs
this may be caused by overstretching so that A and I bands no longer re-engaged
what is muscle atrophy
when destruction of proteins is greater than their replacement resulting in loss of muscle power
what is muscle atrophy caused by
disuse, surgery and disease
what is duchene muscular dystrophy
inherited by X linked pattern and is due to absence of dystrophin gene which results in excess ca2+ entering the cell and into the mitochondria. water goes with it and mitochondria and muscle cells burst. CK and myoglobin levels are v high. muscle cells replaced by adipose
symptoms of duchene muscular dystrophy
muscle weakness. shoulder back walk and belly sticks out. poor balance, tight heel hard and thick lower leg muscles
what is rhabdomyolysis
it is the rupture of muscle cells
why is creatine kinase not a goos assay of myocardial infarction
is an enzyme and it is related after a heart attack but also after the damage of muscle cells
how does a troponin assay work
is related after MI within and hour and the smallest changes in conc of it in the blood are indicative of cardiac muscle damage but the quantity of it is not proportional to degree of muscle damage
what is the effect of the botulism toxin
blocks neurotransmitter resulting in non-contractile state of the skeletal muscle and face paralysis. used to treat wrinkles (botox) and facial muscle spasms
what does organophosphate poisoning result in
used as pesticides ad inhibit activity ach esterase = sludge and days of the week for muscarinic(para) and nicotinic(sympathetic) symptoms
