Neurohumoral influence on cardiac system

Question 1

What does cholinergic mean?

Answer 1

parasympathetic stimulation

Question 2

What is the opposite of cholinergic?

Answer 2

andrenergic (sympathetic system)

Question 3

Where are the control centers for parasymp/symp control of the heart?

Answer 3

medulla oblongata

Question 4

T/F: Stimulation of the vagus nerve results in coronary vasocontriction.

Answer 4

true (vasodilation = symp)

Question 5

What is responsible for cholinergic stimulation in the heart?

Answer 5

vagus nerve, cardiac plexus

Question 6

What is responsible for andrenergic stimulation in the heart?

Answer 6

cord segments T1-4, upper thoracic to cervical chain ganglia

Question 7

Is acetylcholine part of the andrenergic or cholinergic system for the heart?

Answer 7

cholinergic

Question 8

What receptors are the main mechanisms behind controlling heart rate? Where are they found?

Answer 8

baroreceptors

- mechano receptors located in the carotid sinus and aortic arch

Question 9

Your patient with SCI is experiencing low BP. What would you expect would happen to his HR in response, due to the circulatory reflex?

Answer 9

low BP triggers sympathetic response to increase HR/BP and vasoconstriction of peripheral vessels

Question 10

Describe the difference between roles/location of baroreceptors and chemoreceptors for the heart.

Answer 10

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

Question 11

T/F: Increased O2 levels result in a decrease in HR.

Answer 11

true (more O2 available, not needing to pump out as much blood)

Question 12

T/F: a decreased pH indicates an elevated lactic acid level.

Answer 12

true

Question 13

T/F: Increased CO2 and increased lactic acid result in increased HR.

Answer 13

true

Question 14

Describe the effect of low vs high levels of potassium on the heart.

Answer 14

low K+ = hypokalemia

- produces wider PR interval, QRS, tall T waves

Question 15

T/F: There are higher levels of calcium outside of a neuron/muscle cell.

Answer 15

true: calcium wants to go in the neuron/muscle fiber but it can’t d/t the ligand-or voltage-gated channels preventing this

Question 16

Vessicles inside a terminal bulb of a neuron contain what neurotransmitter?

Answer 16

acytelcholine

Question 17

The increasing positivity of the inside of a neuron (d/t the action potential traveling down) results in what channel opening?

Answer 17

voltage gated calcium channel

Question 18

What action causes the vesicles in a terminal bulb to release ACH?

Answer 18

influx of positive calcium ions (now that voltage gated calcium channels are open from action potential)

Question 19

ACH binds to what channels on a muscle fiber?

Answer 19

ligand-gated sodium channels

Question 20

The action of ACH binding onto ligand-gated sodium channels causes what to occur in the muscle fiber?

Answer 20

influx of sodium (positive ions)

- since there’s a higher sodium concentration outside the cell than inside

Question 21

T/F: There’s a higher amount of Ca2+ inside the cell.

Answer 21

false, higher Ca2+ outside

- same as Na+

Question 22

Between Ca2+, Na+, and K+, which have higher concentrations inside the cell?

Answer 22

K+ only

- Ca2+ and Na+ are higher outside the cell (recall neuromuscular jxn)

Question 23

T/F: The inside of a cell is inherently positive.

Answer 23

no, resting intracellular potential is negative
(extracellular is positive)

between these two, these make up the resting membrane potential

Question 24

Normal blood potassium level?

Answer 24

3.5-5 mmol

Question 25

What way does sodium naturally want to diffuse, inside or outside the cell?

Answer 25

wants to go inside, since there’s a higher sodium concentration outside of the cell

Question 26

T/F: As K+ moves out of the cell, it decreases the threshold for an AP.

Answer 26

true

Question 27

With depolarization, what happens to membrane potential?

Answer 27

it goes up (gets positive, more likely AP)
- repolarization = goes back negative, where it began

depolarization = excitation

Question 28

What lab values indicate hypernatremia? Hyponatremia?

Answer 28

> 145mmol

hypo = <130mmol

Question 29

What is the resting potential of a heart cell?

Answer 29

-90mV

Question 30

What is the cause of the resting negative potential of a cardiomyocyte?

Answer 30

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)

Question 31

What ion is responsible for depolarization?

Answer 31

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

Question 32

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?

Answer 32

potassium channels open

• open at +20-30mV
• so potassium starts to get out of the cell, making the cell more negative

Question 33

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?)

Answer 33

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

Question 34

What ion is key for contraction through actin/myosin?

Answer 34

calcium

REVIEW THIS PROCESS

Question 35

What channel closes first with the depolarization process, potassium or calcium?

Answer 35

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

Question 36

How does repolarization occur?

Answer 36

potassium channels close more slowly than calcium channels, so potassium continues to leak out (making cell more negative inside, back to normal!)

Question 37

Give brief description of depolarization process.

Answer 37

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

Question 38

What does hypocalcemia do to the heart?

Answer 38

depress heart actions

Question 39

T/F: Magnesium is a calcium blocker.

Answer 39

true; hypermagnesemia can lead to cardiac arrest

Question 40

Your patient has a history of cardiac issues; upon eval, what questions should you ask to assess for any current symptoms?

Answer 40

1) chest pain
2) fatigue
3) palpitations
4) dizziness/syncope
5) edema