Neurohumeral Influences of the Heart

Question 1

Where is parasympathetic (cholinergic) control located?

Answer 1

Medulla oblongata (cardioinhibitory center)

Question 2

How does parasympathetic stimulation get to the heart?

Answer 2

Via the vagus nerve and cardiac plexus
- innervates the SA node, AV node and sparsely innervates myocardium; releases Ach

Question 3

What does parasympathetic (cholinergic) innervation to the heart do?

Answer 3

• slows rate and force of myocardial contraction
• decreases myocardial metabolism
• causes coronary artery vasoconstriction

Question 4

Where is sympathetic (adrenergic) control for the heart located?

Answer 4

medulla oblongata, cardioacceleratroy center

Question 5

How does sympathetic (adrenergic) innervation get to the heart?

Answer 5

-Via cord segments T1-T4, upper thoracic to superior cervical chain ganglia, innervates SA node, AV node, conduction pathways, and myocytes
- Releases epinephrine and norepinephrine

Question 6

What does sympathetic stimulation to the heart do?

Answer 6

causes an increase in the rate and force of myocardial contraction and myocardial metabolism
- coronary artery vasodilation

Question 7

What do skin and peripheral vasculature receive?

Answer 7

• only post ganglionic sympathetic innervation
• causes vasoconstriction of cutaneous arteries
• Sympathetic inhibition must occur for vasodilation

Question 8

What drugs increase sympathetic functioning?

Answer 8

sympathomimetics
(alpha or beta agonists)

Question 9

What drugs decrease sympathetic functioning?

Answer 9

sympatholytics
(alpha or beta antagonists or blockers)

Question 10

What is the main mechanism controlling heart rate?

Answer 10

baroreceptors

Question 11

Where are baroreceptors located?

Answer 11

in walls of aortic arch and carotid sinus
- function via vasomotor center

Question 12

What do baroreceptors do?

Answer 12

• circulatory reflex: respond to changes in blood pressure

Question 13

Baroreceptors response to increased BP

Answer 13

• parasympathetic stimulation
• decreased rate and force of cardiac contraction
• sympathetic inhibition
• decreased peripheral resistance

Question 14

Baroreceptors response to decreased BP

Answer 14

• sympathetic stimulation
• increased HR and BP
• Vasoconstriction of peripheral blood vessels

Question 15

What does increased right arterial pressure cause

Answer 15

reflex acceleration of heart rate

Question 16

Where are chemoreceptors located?

Answer 16

in the carotid body

Question 17

What are chemoreceptors sensitive to?

Answer 17

• changes in blood chemicals
• oxygen, carbon dioxide, and lactic acide

Question 18

What chemical changes cause an increase in HR

Answer 18

Increased CO2
Decreased O2
Decreased pH/elevated lactic acid

Question 19

What chemical changes cause a decrease in HR

Answer 19

• increase O2 levels

Question 20

Increased body temp causes HR to…

Answer 20

increase

Question 21

Decreased body temp causes HR to…

Answer 21

decrease

Question 22

Hyperkalemia causes

Answer 22

• decreased rate and force of contraction
• widened PR interval and QRS
• tall T waves

Question 23

Hypokalemia causes

Answer 23

• flattened T waves
• prolonged PR and QT intervals
• arrythmias
• may progress to ventricular fibrillation

Question 24

Hypercalcemia causes

Answer 24

• increased heart actions

Question 25

Hypocalcemia causes

Answer 25

• depressed heart actions

Question 26

Hypermagnesemia is

Answer 26

• a calcium channel blocker which can lead to arrhythmias or cardiac arrest

Question 27

Hypomagnesemia causes….

Answer 27

ventricular arrhythmias, coronary artery vasospasm, and sudden death

Question 28

Increased peripheral resistance…

Answer 28

increases arterial blood volume and pressure

Question 29

decreased peripheral resistance…

Answer 29

decreases arterial blood volume and pressure

Question 30

what is peripheral resistance influenced by?

Answer 30

arterial blood volume (viscosity of blood and diameter of arterioles and capillaries)