Cardiac Homeostasis

Question 1

Two types of circulation

Answer 1

• pulmonary; to the lungs, short distance
• systemic; heart to rest of the body

Question 2

Diastolic Phase

Answer 2

• ventricles fill with blood
• ventricular pressure is lower than atrial pressure; AV valves open
• aortic valve closed

Question 3

Systolic Phase

Answer 3

• ## ventricles contract

Question 4

P wave during cardiac cycle

Answer 4

• precedes the contraction of the atria

Question 5

QRS wave during cardiac cycle

Answer 5

• precedes contraction of the ventricles

Question 6

T wave during cardiac cycle

Answer 6

• precedes relaxation of ventricles

Question 7

Heart sounds

Answer 7

1st sound; LUBB. Closure of AV valves during ventricular contraction
2nd sound; DUBB. Closing of pulmonary and aortic valves
3rd sound; after 2nd sound. Changes in filling speed
4th sound; after 1st sound. Contraction of atria vibrates ventricles

Question 8

Afterload

Answer 8

• the load or tension that the ventricular walls have to work against to eject blood
• the amount of work to expel blood to the aorta

Question 9

Preload

Answer 9

• load or tension on muscles at end of diastole
• initial stretching of cardiac myocyte

Question 10

Effect of sympathetic NS on heart

Answer 10

• increases force of contraction
• increases stroke volume, increasing venous return
• contraction of smooth muscle cells in veins

Question 11

Effect of parasympathetic NS on heart

Answer 11

• no effect on ventricles
• decrease atrial contractility

Question 12

Frank Starling Law

Answer 12

• intrinsic regulation of stroke volume
• increased blood filling ventricles, stretches muscle fibres
• causes actin and myosin to lengthen to optimal levels
• leads to more effective recoil, increased force of contraction

Question 13

Atrial Reflexes

Answer 13

• regulation of blood volume
• atria has low-pressure receptors; detect changes in blood volume
• increased blood volume; cardiovascular inhibitory centre activated in the medulla oblongata
• renal receptors in aorta also

Question 14

Reduction of blood volume (kidneys)

Answer 14

• Reduction in sympathetic input to kidney;
  1) dilates efferent arterioles, increase blood flow to glomerulus, increase GFR, more blood filtered
  2) Inhibition of RAAS; inhibits renin secretion
  -Inhibition of ADH
• ANP atrial natriuretic peptide; increase loss of Na+ and water

Question 15

Pathological Cardiac Outputs

Answer 15

• Low CO; drop in cardiac function
• High CO; chronic vasodilation; hyperthyroidism