Neurohumoral influence on cardiac system Flashcards
What does cholinergic mean?
parasympathetic stimulation
What is the opposite of cholinergic?
andrenergic (sympathetic system)
Where are the control centers for parasymp/symp control of the heart?
medulla oblongata
T/F: Stimulation of the vagus nerve results in coronary vasocontriction.
true (vasodilation = symp)
What is responsible for cholinergic stimulation in the heart?
vagus nerve, cardiac plexus
What is responsible for andrenergic stimulation in the heart?
cord segments T1-4, upper thoracic to cervical chain ganglia
Is acetylcholine part of the andrenergic or cholinergic system for the heart?
cholinergic
What receptors are the main mechanisms behind controlling heart rate? Where are they found?
baroreceptors
- mechano receptors located in the carotid sinus and aortic arch
Your patient with SCI is experiencing low BP. What would you expect would happen to his HR in response, due to the circulatory reflex?
low BP triggers sympathetic response to increase HR/BP and vasoconstriction of peripheral vessels
Describe the difference between roles/location of baroreceptors and chemoreceptors for the heart.
1) chemoreceptors
- located in carotid body
- sensitive to blood chemical changes (O2, CO2, lactic acid)
2) baroreceptors
- located in aortic arch and carotid sinus
- detect changes in BP and stimulate either parasymp or symp response accordingly
T/F: Increased O2 levels result in a decrease in HR.
true (more O2 available, not needing to pump out as much blood)
T/F: a decreased pH indicates an elevated lactic acid level.
true
T/F: Increased CO2 and increased lactic acid result in increased HR.
true
Describe the effect of low vs high levels of potassium on the heart.
low K+ = hypokalemia
- produces wider PR interval, QRS, tall T waves
T/F: There are higher levels of calcium outside of a neuron/muscle cell.
true: calcium wants to go in the neuron/muscle fiber but it can’t d/t the ligand-or voltage-gated channels preventing this
Vessicles inside a terminal bulb of a neuron contain what neurotransmitter?
acytelcholine
The increasing positivity of the inside of a neuron (d/t the action potential traveling down) results in what channel opening?
voltage gated calcium channel
What action causes the vesicles in a terminal bulb to release ACH?
influx of positive calcium ions (now that voltage gated calcium channels are open from action potential)
ACH binds to what channels on a muscle fiber?
ligand-gated sodium channels
The action of ACH binding onto ligand-gated sodium channels causes what to occur in the muscle fiber?
influx of sodium (positive ions)
- since there’s a higher sodium concentration outside the cell than inside
T/F: There’s a higher amount of Ca2+ inside the cell.
false, higher Ca2+ outside
- same as Na+
Between Ca2+, Na+, and K+, which have higher concentrations inside the cell?
K+ only
- Ca2+ and Na+ are higher outside the cell (recall neuromuscular jxn)
T/F: The inside of a cell is inherently positive.
no, resting intracellular potential is negative
(extracellular is positive)
between these two, these make up the resting membrane potential
Normal blood potassium level?
3.5-5 mmol
What way does sodium naturally want to diffuse, inside or outside the cell?
wants to go inside, since there’s a higher sodium concentration outside of the cell
T/F: As K+ moves out of the cell, it decreases the threshold for an AP.
true
With depolarization, what happens to membrane potential?
it goes up (gets positive, more likely AP)
- repolarization = goes back negative, where it began
depolarization = excitation
What lab values indicate hypernatremia? Hyponatremia?
> 145mmol
hypo = <130mmol
What is the resting potential of a heart cell?
-90mV
What is the cause of the resting negative potential of a cardiomyocyte?
1) sodium potassium channel: removing 3 Na+ ions and bringing in 2 K+ ions (negative net difference for inside the cell)
2) leaking K+ channels (K+ leaks out of cell, so inside of cell loses lots of positive charge)
What ion is responsible for depolarization?
Na+ rushing in
- some stimulus allows one Na+ channel to open, and that increases potential from -90 to -70
- once it hits -70, voltage-gated sodium channels burst open and TONS of sodium can now enter the cell
After Na2+ has rushed into the cell at full capacity, now what channels open up to help reduce that major positivity going on in the cell?
potassium channels open
- open at +20-30mV
- so potassium starts to get out of the cell, making the cell more negative
As potassium leaks out of the cell, NOW what channels open? (recall, sodium rushed in, opened potassium channels… now potassium is rushing out, and this opens what channel?)
calcium channel
- calcium moves in
- and now that calcium is moving into the cell (which is a myocite, remember), now it can CONTRACT
and thus we have heart contraction
What ion is key for contraction through actin/myosin?
calcium
REVIEW THIS PROCESS
What channel closes first with the depolarization process, potassium or calcium?
calcium way quicker to close
- so it stops coming in
- but potassium doesn’t close, so you keep getting outflow of K+ at this point, making cell more negative
How does repolarization occur?
potassium channels close more slowly than calcium channels, so potassium continues to leak out (making cell more negative inside, back to normal!)
Give brief description of depolarization process.
1) resting membrane -90mV
2) stimulus allows Na+ channel to open, rising cell to -70mV
3) now Na+ VG channels open, flooding in calcium and making cell very positive (+20mV)
4) potassium and calcium channels now open, allowing cell to leak potassium but gain calcium (Ca2+ wants to go in, K+ wants out) -> plateau here of voltage since positive trades for positive
What does hypocalcemia do to the heart?
depress heart actions
T/F: Magnesium is a calcium blocker.
true; hypermagnesemia can lead to cardiac arrest
Your patient has a history of cardiac issues; upon eval, what questions should you ask to assess for any current symptoms?
1) chest pain
2) fatigue
3) palpitations
4) dizziness/syncope
5) edema
