Term
| contractile cells, and pacemaker cells |
|
Definition
| what are the 2 types of cardiac myocytes? |
|
|
Term
|
Definition
| which type of cardiac myocytes do excitation contraction coupling? |
|
|
Term
SA node
AV node
Perkinje fibers |
|
Definition
| give examples of pacemaker cells in the heart (3) |
|
|
Term
|
Definition
| what spreads the action potential through the heart? |
|
|
Term
|
Definition
| what is the main role of contractile cells of the heart? |
|
|
Term
|
Definition
| what cell initiate depolarization and are autorythmic in the heart? |
|
|
Term
|
Definition
| how are contractile fibers arranged in the heart? |
|
|
Term
1)large t-tubules (to help get action potential into cell and release Ca++ from SR)
2)lots of mitochondria
3)large SR to hold a lot of Ca++
4) intercalated discs |
|
Definition
| list the main features of a contractile cardiac muscle cell |
|
|
Term
| gap junctions (intercalated discs) |
|
Definition
| what allows cardiac myocytes to contract as a functional unit? |
|
|
Term
|
Definition
| resting potential of a cardiac myocyte |
|
|
Term
sodium: phase 1
potassium: phase 3,4,0,1
Calcium: phase 2 |
|
Definition
| in which phase is a cardiac myocyte most permeable to sodium? potassium? calcium? |
|
|
Term
phase 0: depolarization
phase 1: initial repolarization
phase 2: plateau
phase 3: rapid repolarization
phase 4: resting membrane potential |
|
Definition
| what occurs in each phase of an action potential in terms of overall cellular effects |
|
|
Term
| cardiac muscle has a plateau phase, it is caused by calcium channels |
|
Definition
| what phase of an action potential for cardiac muscle differs in skeletal muscle? what causes this? |
|
|
Term
sodium: phase 1-4
potassium: phase 2
calcium: phases 3,4,0,1 |
|
Definition
| in which phase is a cardiac myocyte least permeable to sodium? potassium? calcium? |
|
|
Term
0: Na + channels open
1: Na+ channels close
2: Ca+ channels open, K+ channels close
3: Ca+ channels close, K+ channels open
4:Resting potential (close to K+) |
|
Definition
| describe the phases of an action potential in a cardiac myocyte in terms of what ion channels open/close |
|
|
Term
| both are longer in cardiac muscles, also cardiac muscle cannot fuse contractions (no tetany) |
|
Definition
| compared the length of the action potential and refractory period in skeletal muscle and cardiac muscle |
|
|
Term
|
Definition
| what ion sets the resting membrane potential for cardiac muscle? |
|
|
Term
|
Definition
| what is the normal refractory perior for cardiac muscle cells? |
|
|
Term
|
Definition
| what is the relative refractory period for cardiac myocytes? |
|
|
Term
| yes, but it takes a stringer excitatory signal (and the contraction is weaker) |
|
Definition
| can an action potential occur during the relative refractory period of cardiac myocytes? |
|
|
Term
| cardiac muscle ryanodine receptors are not attached to the DHPR thing, but they both cause the calcium release from the SR |
|
Definition
| how do ryanodine receptors differ in cardiac muscle cells compared to skeletal muscle? |
|
|
Term
| skeletal muscle uses SR calcium, but cardiac muscle is dependent on outside Ca++ (25% of the calcium) |
|
Definition
| compare calcium sources for skeletal muscle and cardiac muscle |
|
|
Term
|
Definition
| what inhibits the SERCA pump in cardiac muscle to prolong contraction? |
|
|
Term
| the sodium/calcium pump which pumps out 1 calcium per 3 sodium in this is "coupled" |
|
Definition
| to pump the calcium out of a cardiac myocyte, what method is used primarily? |
|
|
Term
| yes, does the same actin myosin interaction skeletal muscle does |
|
Definition
| is there troponin in cardiac muscles? |
|
|
Term
| pumps Calcium back into the SR to allow muscle relaxation (this is inhibited by phospholambin) |
|
Definition
| what does the SERCA pump do? |
|
|
Term
1) action potential
2) VGCC calcium channel opens, allowing Ca++ to flow into the cell
3) Calcium activates ryanodine receptors in the SR
4) calcium binds to troponin, allowing the actin, myosin interaction
5) relaxation: 25% of Calcium is pumped out with the sodium coupled channels/ATPase, and 75% is pumped back into the SR via SERCA |
|
Definition
| list the steps (in the diagram) that a cardiac muscle takes to contract |
|
|
Term
| cardiac muscle cannot recruit more fibers or increase the rate of the action potentials, so it has to control things by regulating the calcium levels |
|
Definition
| how is cardiac muscle contraction force controlled? |
|
|
Term
| they allow calcium into the cell allowing for stronger contractions |
|
Definition
| what do L-type calcium channels (VGCC's or voltage gated calcium channels) do to cardiac muscle contraction when adrenergic receptors are stimulated? |
|
|
Term
1)L-type calcium channels (more Ca in)
2)Inhibition of phospholambin (inhibit the calcium re-uptake inhibitor) |
|
Definition
| what 2 things are activated with adrenergic stimulation of cardiac muscle? |
|
|
Term
1) adrenergic receptors have been stimulated
2) calcium an be taken up into the SR more rapidly allowing the heart to contract and relax faster |
|
Definition
| what happens if phospholambin is inhibited? |
|
|
Term
they decrease strength of contraction (usually in order to decrease blood pressure)
since they block adrenergic stimulation, there is less calcium in the cell because the VGCC's are not activated to pump in outside calcium |
|
Definition
| what do beta blockers do to cardiac muscle cells? |
|
|
Term
| they inhibit L type calcium channels, decreasing the amount of calcium available to the myocyte |
|
Definition
| how do verapamil and nifedipine work? |
|
|
Term
| congestive heart failure -> it increases cardiac contraction and cardiac output |
|
Definition
| what is digoxin used for clinically? |
|
|
Term
| inhibits the Na/K+ pump, so sodium builds up inside the cell since it can't pump out. This slows the Na/Ca exchanger or reverses it even, so calcium builds up improving contraction |
|
Definition
| how does digoxin work on the cell bio level? |
|
|
Term
| fox glove, related to the digitalis plant(James bond was poisoned with this) |
|
Definition
| what plant does digoxin come from? what is this related to? |
|
|
Term
| it can trigger arrythmias because the electrolyte balance gets messed up, because the pumps are messed up |
|
Definition
| what is the down side of using digoxin? |
|
|
Term
| he went into ventricular tachycardia, so he tried to use his AED to stop his heart so the rhythm would reset but he did this after shooting up with some mystery cocktail to reverse the poison effects (ok so actually the girl connected his lead, you get the point -> arryhtmia) |
|
Definition
| when bond was poisoned with digitalis, what did he do, why? |
|
|
Term
| SA node, AV node, bundle of His, Purkinje fibers (the pacemaker cells) |
|
Definition
| what cells have a funny current? |
|
|
Term
pacemaker cells are contractile, but have fewer contractile fibers, no organized sarcomeres, and a faster conducting rate
they also dont have t-tubules, and auto depolarize |
|
Definition
| describe the contractile fibers, sarcomeres, and conducting rate of pacemaker cells compared to contractile |
|
|
Term
|
Definition
| why do pacemaker cells autodepolarize? |
|
|
Term
| phase 2 (where calcium channels open) |
|
Definition
| if you give someone verapamil, what phase of the action potential is inhibited? |
|
|
Term
| If, or funny current in pacemaker cells |
|
Definition
| what does HCN or hyperpolarization activated cyclic nucleotide gated describe? |
|
|
Term
| it is not constant, it slowly depolarizes due to the funny current(leaky sodium channels) |
|
Definition
| describe the resting potential of the conductile(pacemaker) cells |
|
|
Term
SA: 60-80/min
AV: 40-50/min
Purkinje fibers: 20/min |
|
Definition
| describe the intrinsic depolarization rate of SA nodal cells, AV nodal cells, and Purkinje fibers. |
|
|
Term
| they have a faster funny current |
|
Definition
| why do the atria beat faster than the ventricles? |
|
|
Term
1) there is no phase 1 in pacemaker cells(no sodium channels for fast depolarization)
2) there is no phase 2 (no L type calcium receptors, so no plateaus)
3) pacemaker cells have a funny current
both have potassium channels |
|
Definition
| how do pacemaker(like the SA node) action potentials differ from contractile cell action potentials? |
|
|
Term
1)SA node
2) internodal pathways
3a) atria
3b) AV node
4) bundle of His
5) L & R bundle branches (septa -> apex)
6) Purkinje fibers
7) ventricle muscles (last being upper left ventricle)
also depolarization spreads from endocardium to epicardium |
|
Definition
| describe the order structures are depolarized in the heart |
|
|
Term
|
Definition
| an action potential begins in the SA node, travels through conductile cells, then spreads through the muscle cells via ____ |
|
|
Term
|
Definition
| what cells undergo automatic depolarization to initiate an action potential? |
|
|
Term
| near the vena cava as far as Wacker is concerned |
|
Definition
|
|
Term
|
Definition
| how long does it take the an action potential to reach the AV node from the SA node? |
|
|
Term
|
Definition
| what is the conducting velocity of the heart? |
|
|
Term
| a fibrous tissue band (which is an insulator) that has fewer gap junctions -this slows down the AP |
|
Definition
| this separates the atria and ventricle so that action potentials only spread via the bundle of His |
|
|
Term
| it creates a pause in contraction (slows the action potential down) so that blood has time to fill up the ventricles |
|
Definition
| why is the fibrous tissue band important in the heart? |
|
|
Term
|
Definition
| how long does it take an action potential to reach the bundle of his (AV bundle) from the AV node? |
|
|
Term
|
Definition
| how long does it take an action potential to reach the bundle branches(ventricular septum)? |
|
|
Term
large, it is 1.5-4.0 m/s
in the muscles the conduction is 0.3-0.5 m/s |
|
Definition
| describe the conduction velocity of Purkinje fibers, what is the conduction velocity here? what is the conduction velocity in the cardiac muscles? |
|
|
Term
|
Definition
| if an action potential is spreading through the muscle rather than the purkinje fibers, what would the EKG show? |
|
|
