Exam 1 Flashcards
Na+
Iout, Iin, Keq
Iout: 145
Iin: 10
Keq: 70mV
K+
Iout, Iin, Keq
Iout: 4
Iin: 135
Keq: -94mV
Ca2+
Iout, Iin, Keq
Iout: 2
Iin: 10^-4
Keq: 132
goldmann field equation
each permeable ion attempts to drive Emem toward its own Ex (Nernst potential)
-many ions - total permeable ions dictate membrane potential
resting membrane potential
membrane potential is stable at this time
nodal tissue
pacemaker cells
how are cardiac cells myogenic
the electrical impulse starts in the same muscle causing it to contract
pacemakers
SA node, AV node, PBH system
provides electricity that generates heart beat by action potentials
pacemakers
what is the sinus rhythm
pace from the SA node
characteristics of nodal tissue action potential
- sinusoidal curve (wave like)
- no true RMP - never stable
- diastolic depolarization (graded potential)
Funny current
activated at a negative voltage!!
cation nonspecific!! - allows Na, Ca, and K to pass through
diastolic depolarization
sum of 3 currents that flow through funny channel
-each ion that passes drives the membrane potential to its own Nernst potential
-graded potential - slope shows rate of flux slow
current not strong bc slope is gradual
characteristics of cardiac muscle
- myogenic
- Ca dependent
- involuntary, striated
- no true RMP
- intercalated discs
- muscle fibers parallel and in series
- 30% is mitochondria!! - requires lots of energy
- T tubule and sarcoplasmic reticulum not as extensive as skeletal
physical places with high density of gap junctions
intercalated discs
gap junctions
- proteins imbedded in cell membrane of myocytes
- allow low resistance of current flow
- allow cell to cell communication and current flow between ICF
- protein composition with hydrophillic core - aqueous pore
what is the dominant pacemaker in a healthy heart
SA node triggers myocyte to have an action potential
phase 0 nodal tissue/pacemaker cell action potential
depolarization
once threshold is hit, Ca channels open
phase 3 nodal tissue action potential
repolarization
K channels activated
phase 4 nodal tissue action potential
diastolic depolarization (pacemaker potential) gives heart automaticity caused by activation of funny channels
myocyte action potential
square waves
like a light switch - needs to be hit to turn on and needs to be hit to turn off
MP: -90mV more neg than nodal tissue
phase 0 of myocyte-cardiac muscle action potential
depolarization
main ion moving is Na
Na fast channels - resistance to Na is low
phase 1 myocyte action potential
at peak of action potential
opening of K+ slow channels - this new current is why the line slopes down
inactivation of Na+ channels
phase 2 myocyte action potential
plateau
Ca, K, and Na lead to the plateau - all involved bc they are cancelling eachother out
time in the action potential when nothing is changing - parallel to x-axis
heart muscle does not do tetany
phase 3 myocyte action potential
membrane potential plumeting toward negative (K+)
fast K+ channels
repolarization does NOT extend beyond x-axis
in all muscle types, _____ precedes ______
electrical activity precedes mechanical
How does the PNS lower heart rate?
- interbeat interval
- inc maximum diastolic potential
what happens when the interbeat interval increases?
it gets longer between heart beats
takes a longer amount of time to reach threshold
lowers HR
how does NE effect the heart
increases heart rate
NADR
lowest point, maximum diastolic depolarization - most negative point
cardiac control center
cell bodies here travel to thoracic region when they synapse at ganglion
medulla
interganglionic commisural fibers
nerve fibers connecting superior and inferior ganglion together
all target tissues stimulated at same time, low R junctions
what responses do you get when you activate the medulla
indiscrete, systemic, not specific - sympathetic
indiscrete bc of the impulse by the interganglionic comisural fibers - conduct electricity get massive ganglion activation
arenaline is second contributer to SNS response
released fom adrenal medulla
- adrenal gland has tissue that can then secrete epinephrine
effective refractory period
can’t get another action potential
why are there effective refractory periods?
- all Na channels inactivated
- in order to get them ready for another action potential the cell has to be negative
need phase 0 to get anther action potential
what fraction of Na channels are closed at phase 4?
100%
