Excitation-contraction Coupling Flashcards
(48 cards)
Which nerve parasympatheticaly innervates the heart?
where on the heart does it innervate?
What effect does it have on heart?
- VAGUS 10th Cranial nerve
- synapses with SA and AV node
- post ganglionic cells release Ach
- acts on M2 receptors
DECREASE Heart Rate
DECREASE AV node conduction velocity
describe how the resting membrane potential of cardiac cells is
generated
- K+ PERMEBAILITY SETS THE RMP*
- cardiac myocytes r more permeable to K
- K+ ions leave the cell down their concentration gradient
- this makes the inside negative
- as charge builds up an electrical gradient is made.
draw the changes in membrane potential and describe the ionic currents underlying the cell AP of
(i) ventricular cells
(ii) pacemaker cells
P
describe the processes of excitation - contraction coupling in ventricular myocardial cells.
P
describe the factors influencing the changes in intracellular free Ca + concentration of ventricular cells during the AP
O
explain the effects of hyper and hypokalaemia on the heart
hyper > Increased extracellular K levels result in depolarization of the membrane potentials of cells, due to the increase in the Ek. This depolarization opens some voltage-gated sodium channels, but also INACTIVATES them at the same time.»_space;SLOWER DEPOLARISATION UPSTROKE
Hypo > delays repolarization
LENGTHENS AP
describe the membrane potential changes in pacemaker cells associated with increases and decreases in heart rate.
P
detail the neurotransmitters and receptors involved in the
autonomic nervous system
O
explain the cellular mechanisms by which the autonomic nervous system controls
1) heart rate
2) force of contraction in the normal heart
O
describe the mechanisms which control contraction of vascular smooth muscle cells
O
explain the role of the ANS in controlling peripheral resistance
P
what r pacemaker cells?
specialised cells that generate an electrical event at regular intervals.
the AP
distinguish btw AP in Pacemaker cells & ventricular myocardial cells
,
what structure conducts excitation through the ventricular myocardiam?
purkunjee fibers
why is the cardiac AP much longer?
bc of the ‘plateu phase’ caused mainly by calcium
describe how RMP is made
- K+ PERMEBAILITY SETS THE RMP*
- cardiac myocytes r more permeable to K
- K+ ions leave the cell down their concentration gradient
- this makes the inside negative
- as charge builds up an electrical gradient is made.
what channel is responsible for the upstroke of the AP in pacemaker cells?
L-type Ca channels!
*
*AT AN EQAULAIBREM OF AN ION, THE CONCENTRATION GRADIENT AND ELECTRICAL GRADIENT R THE SAME
reminder
describe what happens during platue phase
voltage-gated ca+ channels (L-type)»_space;ca+ influx
FEW K channels»_space; efflux
this balances the potential
what is the pacemaker potential?
refers to a LONG SLOW depolarization to threshold, its due to a ‘funny current’ which r made by channels called HCN
In SA and AV node
what is meant by the “funny current?” what channels r responsible for it
during pacemaker potential, it spontaneously depolarises from its most negative value (-60mv) due to HCN channels (open due to hyper polarisation). this initial depolarisation is known as the funny current
draw the SA node action potential, what shape does the graph give?
- LONG depolarisation to threshold via HCN
- upstroke via L-type voltage gated ca channels
- downstroke opening of voltage-K channels
what is a special feature about the SA node AP
they don’t ever sit at rest, they spontaneously depolarise, they don’t need neighbouring cells to activate them (3ala kayf umhum)
what channels make the funny current?
HCN channels, influx of Na+ channels (SLOW sodium channels)
