block 2 lecture 10 Flashcards
what is the appearance of cardiac muscle?
striated, branched with intercolated discs
what ensures the muscle acts as one functional unit?
wave of depolarisation moves via gap junction
what are myocytes made up of?
myofibrils
myosin structure?
tail region of alpha chains in an alpha helix hinge region 2 heads regulatory light chians alkyle light chains
what allows myosin heads to bind to the actin?
hydrolysis of ATP
what type of protein is actin?
globular
what is the structure of actin?
two helical stands
inbetween strands is tropomyosin
what is the troponin complex?
troponin I
troponin C
troponin T
what is troponin I?
the inhibitory part
what does troponin C do?
binds to calcium ions
what does troponin T do?
keeps the troponin bound to the actin
what happens to troponin when calcium binds?
confirmational change and cross bridges can form
what happens to the products of ATP hydrolysis when it binds to myosin?
stays bound
what produces the power stroke?
inorganic phosphate is released
what is excitatory contraction coupling?
an action potential triggers a myocyte to contract
what happens when an action potential depolarises the membrane of a myocyte?
calcium ion channels open allowing influx of calcium ions
what are dihydropyridine receptors?
voltage gated calcium ion channels in the T tubules
what are ryonidine receptors?
receptor on the sarcosplasmic reticulum
what is the calcium release process called in the muscle of the heart?
calcium induced calcium influx
what controls the rate and force of contraction?
autonomic nervous system
what is released in the sympathetic system and where is it released from?
noradrenaline from the accelerator nerve
adrenal glands secrete adrenaline
what happens when the neurotransmitter of the sympathetic nervous system binds to the calcium receptors?
triggers calcium ion channels to trigger an influx of calcium ions which induces calcium release from the sarcoplastic reticulum
what can the noradrenaline bind to?
beta 1
what happens when noradrenaline binds to beta 1?
activates adenylate cyclase, forms cAMP, protein kinase phosphorylated, phospholamban phosphorylated so sarcoplasmic reticulum can pump calcium in
what is lusitropy?
relaxation
how does lusitropy work?
sarcoendoplasmic reticulum calcium ATPase returns calcium into the sarcoplasmic reticulum,
sodium/calcium exchanges in the sarcolemma transports calcium out of the cell
where are the cardiac inhibitory and cardiac accelerator centers?
medulla
what does the sympathetic nerve innervate?
nodes and ventricular muscle
what does the SAN release and where does it go?
acetylecholine onto the muscarinic receptors
what affects does noradrenaline have?
positive chronotropy
positive dromotropy
positive inotropy
what is positive chronotropy?
increase heart rate
what is positive dromotropy?
increased conduction velocity
what is positive inotropy?
increased contractility
what does acetylecholine bind to?
M2 receptors
what does acetylecholine binding to M2 receptors do?
negative chronotropy, dromotropy and inotropy
what happens when noradrenaline is released from the SAN?
bind to beta 1 coupled to G stimulatory proteins, CAMP is formed and protein kinase A is activated, calcium ion channel is depolarised, this increases action potential generation resulting in increased chronotropy and inotropy
what happens exactly when acetylecholine is released from SAN?
binds to muscarinic M2 inhibiting G proteins meaning you get phosphorylation of a potassium ion channel (GIRK) this causes potassium ions to leave the cell, this hyperpolarises the cell and decreases the heart rate
phase 4? sino atrial node action potential
sodium influx, calcium ion channels recover from inactivation, pump restores the ion gradient
phase 0? sino atrial node action potential
calcium ions influx this depolarised the SAN cells
phase 3? sino atrial node action potential
calcium ion channels become inactivated and there is a delayed potassium ion efflux to restore resting potential.
important feature of atrial emptying?
mostly passive
route of electrical activity in the heart?
sino atrial node
bundle of hiss
purkinje fibers
what is the anulus fibrosus?
acts as an electrical insulator between the atria and ventricles
what is the pacemaker of the heart?
SAN
what is EDV?
end diastolic volume
volume of blood left at the end of diastole
what is isovolumetric contraction?
when volume of blood remains the same but the pressure is increasing due to contraction
