The heart Flashcards
heart is found in
mediastinum, cuts into left lung
peripheral resistance
resistance to blood flow imposed by force of friction between blood and walls of vessels
factors influencing peripheral resistance
blood viscosity, diameter of arterioles
- high plasma protein= higher blood pressure
- high hematocrit (%RBC)= high blood pressure
vasoconstrict
smaller diameter= less blood flow, but higher pressure
what prevent AV valves from being everted into the ratio when ventricle contract and blood is pushed into them?
chord tendinae
when does blood go into ventricle
when more pressure in atrium
semilunar valves have ?
3 cusps
when do semilunar close?
when pressure in the ventricle falls below aortic and pulmonary pressure, so blood wants to go back into ventricle BUT..
- bc there are cusps, the cups fill and close!
which specialized cells are autorythmic and make up the conduction system, but do not contract
SA, AV node, AV bundle, right, left bundle branches and purkinje system
- these are even more specialized than other cells
- conduct impulse (AP) but no contraction
ectopic focus
caffiene, lack of sleep, heart disease- causing purkinje fibers to become overly excitable and depolarize faster than the SA node
order
SA, AV, AV bundle, bundle of his, PF
cardiac cells Auto ryth ?
do not have resting potencials
what instead to cardiac AR cells have
pacemaker- drifts between - slow depolarization
what causes membrane potential slow-drift?
less K+ leaking out , while NA+ still going in - till thresold- Ca+ in , K= out
within intercalated disc 2 junctions
gap and desmosomes
RMP potencial in contatille cells greater or less than neurons
less -90
neurons and other cells ( -70)
how is plateau maintained
Ca+ in slow, less K + out
calcium spark causes what?
Ca+ to bind to troponin ( same as skeletal )
indicator of hearth damage
blood test- troponin ( released in cell death)
rapid repetitive stimulation
tetnus
- can happen in skeletal bc short refractory, but not in cardiac bc Na+ channels are inactivated until membrane has repolarized
can both para and symp affect HR
yes both divisions of autonomic - through second messenger cAMP
vagus nerve
parasympathetic–> Ach down nerve ( bc NT) to slow heart rate- hyper polarize
sympathetic
release norepinephrine and epinephrine ( NT’s through blood)- depolarize
receptors sensitive to changes in pressure
baroreceptors
baroreceptors
send nerve fibers to the cardic control center in medulla oblongata - neg feedback loop- to oppose changes in blood pressure
snake drawing ( has is neg feedback included)
see snake, increase BP, baroreceptors sense this, send nerve to medulla, integrate, send signal down vagus nerve (Ach) to slow heart rate back to normal after scare, ACH act on SA node to hyperpolarize cells ( make more negative with K+ moving out )
