Cardiovascular- Neurohumeral Influences

Question 1

Parasympathetic stimulation (cholinergic) and its effect on CV system?

Answer 1

1. control located in medulla oblongata, cardioinhibitory center
2. via vagus nerve (CN X), cardiac plexus, innervates the SA node, AV node, and sparsely innervates myocardium; releases acetylcholine
3. slows rate and force of myocardial contraction; decreases myocardial metabolism
4. Causes coronary artery vasoconstriction

Question 2

Sympathetic stimulation (adrenergic) and its effect on CV system?

Answer 2

1. control located in medulla oblongata, cardioacceleratory center
2. via cord segment T1-T4, upper thoracic to superior cervical chain ganglia; innervates SA node, AV node, conduction pathways, and myocytes; releases epinephrine and norepinephrine
3. causes an increase in the rate and force of myocardial contractions and myocardial metabolism
4. causes coronary artery vasodilation
5. The skin and peripheral vasculature receive only postganglionic sympathetic innervation. causes vasoconstriction of cutaneous arteries; sympathetic inhibition must occur for vasodilation.
6. drugs that increase sympathetic functioning are sympathomimetics; drugs that decrease sympathetic functioning are sympatholytics

Question 3

What are the additional control mechanisms?

Answer 3

1. baroreceptors (pressure receptors)
2. chemoreceptors
3. body temperature
4. ion concentrations

Question 4

Baroreceptors- the what, where, why

Answer 4

• main mechanisms controlling heart rate
• located in walls of aortic arch and carotid sinus via vasomotor center
• circulatory reflex- responds to changes in blood pressure

Question 5

How does circulatory reflex in baroreceptors work?

Answer 5

• increased BP results in parasympathetic stimulation, decreased rate and force of cardiac contraction; sympathetic inhabition, decreased peripheral resistance
• decreased BP results in sympathetic stimulation, increased HR and BP and vasoconstriction of peripheral blood vessels.
• Increase R atrial pressure causes reflex acceleration of HR

Question 6

Where are chemoreceptors and what do they do?

Answer 6

1. located in the carotid body
2. Sensitive to changes in blood chemicals: O2, CO2, lactic acid
   
   • increased CO2 or decreased O2 or decreased pH (elevated lactic acid) results in an increase in HR
   • increased O2 levels result in a decrease in HR

Question 7

How does body temperature work as a control mechanism?

Answer 7

• increased body temp causes HR to increase

- decreased body temp causes HR to decrease

Question 8

What are 6 ion changes that can act as a control mechanism?

Answer 8

1. hyperkalemia
2. hypokalemia
3. hypercalcemia
4. hypocalcemia
5. hypermagnesemia
6. hyposmagnesemia

Question 9

The effect of hyperkalemia

Answer 9

increased concentration of potassium ions decreases the HR and force or contraction, produces ECG changes (widened PR interval and QRS, tall T waves)

Question 10

The effect of hypokalemia

Answer 10

decreased concentrations of potassiumions produces ECG changes (flattened T waves, prolonged PR and QT intervals); arrhythmias, may progress to ventricular fibrillation

Question 11

The effect of hypercalcemia

Answer 11

increased calcium = increased heart actions

Question 12

The effect of hypocalcemia

Answer 12

decreased calcium = depressed heart actions

Question 13

The effect of hypermagnesemia

Answer 13

increased magnesium is a calcium blocker which can lead to arrhythmias or cardiac arrest

Question 14

The effect of hypomagnesemia

Answer 14

decreased magnesium causes ventricular arrhthmias, coronary artery vasospasm, and sudden death

Question 15

3 Things about peripheral resistance

Answer 15

1. increased peripheral resistance increases arterial blood volume and pressure
2. Decreased peripheral resistance decreases arterial blood volume and pressure.
3. Influenced by arterial blood volume, viscosity of blood and diameter of arterioles and capillaries.