Heart Physiology (05)

Question 1

Cardiac output (CO)

Answer 1

Amt of blood pumped by heart per min (typically refer to left ventricle)

Question 2

CO=?

Answer 2

HR x SV

Question 3

Cardiac reserve

Answer 3

Difference between co at rest and maximum CO

Question 4

Intristic regulation

Answer 4

Results from normal functional characteristics, not on neural or hormonal regulation

Question 5

Extrinsic regulation

Answer 5

Involves neural and hormonal control

Question 6

Factors affecting stroke volume (3)

Answer 6

1.Preload 2. Afterload 3. Contractility

Question 7

Preload

Answer 7

Amt of stretch of the ventricular walls before contraction

Question 8

What determines EDV

Answer 8

Venous return

Question 9

Afterload

Answer 9

The pressure the contracting ventricles must produce to overcome the pressure in the aorta

Question 10

Contractility

Answer 10

The forcefulness of contraction of the ventricle muscle fibers (strength of contraction), controlled by inotropic agents

Question 11

Positive inotropic agents

Answer 11

(open Ca 2+ channels): SNS: cardiac accelerator nerves: neurotransmitter – Norepinephrine (NE); hormones from adrenal medulla (Epinephrine/NE)

Question 12

Negative inotropic agents

Answer 12

drugs: calcium channel blockers and beta blockers

Question 13

Factors regulating heart rate

Answer 13

• Autonomic nervous system
• Hormones
• Ions
• Age
• Gender
• Physical fitness
• Temperature

Question 14

Parasympathetic nerve stimulation

Answer 14

• Vagus nerve: ↓ heart rate
• neurotransmitter acetylcholine (Ach) hyperpolarizes the heart (more K+ channels open, takes longer to reach threshold)

Question 15

Sympathetic nerve stimulation

Answer 15

• Cardiac accelerator nerves: ↑ heart rate (& contractility)
• NE released at SA/AV nodes (also coronary vessels & myocardium) (opens Ca 2+ channels)

Question 16

Hormonal Control (SNS)

Answer 16

• Epinephrine & NE from the adrenal medulla.
• Occurs in response to increased physical activity, emotional excitement, stress. Slower, but lasts longer

Question 17

Effect of blood pressure

Answer 17

• Baroreceptors monitor blood pressure (sensory neurons)
• Internal carotid arteries and aorta (carotid and aortic bodies)
• Sensory information to centers in the medulla oblongata

Question 18

Effect of pH, carbon dioxide, oxygen

Answer 18

• Chemoreceptors detect pH and CO 2 changes in the medulla oblongata
• Chemoreceptors also monitoring O 2 in carotid and aortic bodies

Question 19

Effect of extracellular ion concentration

Answer 19

Excess or reduced extracellular K+ decreases heart rate

Question 20

Effect of body temperature

Answer 20

Heart rate increases when body temperature increases, heart rate decreases when body temperature decreases