Cardio Mod 4 Flashcards

Question

Resistance is related to blood flow how?

Answer 1

• Resistance is inversely related to blood flow | i) Increased resistance = decreased blood flow (less volume per unit of time

Answer 2

(i) Sometimes referred to as systemic vascular resistance (SVR) 1. TPR (or SVR) = resistance to all systemic vasculature excluding pulmonary vasculature 2. Arterioles major role in regulating TPR (SVR) a. Narrowed channel of arteriole provides most resistance – allows larger cross section of capillary bed to have slow low pressure flow for gas/nutrient exchange (ii) Inverse relationship 1. ↓ TPR = ↑ arterial blood flow to tissues and ↑ blood flow to venous system. 2. ↑ TPR = ↓ arterial blood flow to tissues and ↓ blood flow to venous system.

Answer 3

sympathetic “fight or flight” stress role requires different responses of blood vessels depending on tissue a. Vasoconstriction to preserve/increase systemic BP i. peripheral and GI/GU blood vessels b. Vasodilation to divert blood to tissues needed for “action/stress response” i. skeletal muscle, heart and CNS blood vessels to promote action/stress response c. Different sympathetic receptors allow dual response of blood vessels i. Beta 2 (β2) - dilate smooth muscle of blood vessels ii. Alpha 1 (α1) – constricts smooth muscle of blood vessels

Answer 4

sympathetic increases heart rate (chronotropic)/contractility(inotropic) a. Atria i. Nodal tissue: increase HR (increase conduction rate) ii. Myocardium (contractile tissue): increase contractility of atria b. Ventricles i. Myocardium (contractile tissue): increase contractility of ventricle

Answer 5

parasympathetic dilate GI/salivary gland blood vessels a. Vasodilation to GI tract to promote energy uptake/conservation b. Parasympathetic only innervate blood vessels of GI/salivary gland and erectile tissue

Answer 6

a. Atria: i. Nodal tissue: decrease HR (decrease conduction rate) ii. Myocardium (contractile tissue): decrease contractility of atria b. Ventricles i. No influence - parasympathetics DO NOT innervate ventricle

Answer 7

(i) Located within aorta and carotid sinus 1. If increase stretch on baroreceptors (↑ BP) then receptors signal CV centers in medulla to ↑ parasympathetic output and ↓ sympathetic output a. Net result = ↓cardiac output (↓HR, ↓contractility) and ↑ systemic blood vessel dilation 2. Or…if a decreased stretch on baroreceptors (↓ BP) then receptors signal CV centers in medulla to ↓ parasympathetic output and ↑ sympathetic output

Answer 8

(i) Located within aorta and carotid arteries (ii) Central receptors located brainstem (medulla) (iii) Major role in respiratory rate but also influence resistance by vasodilating and constricting blood vessels

Answer 9

a. Compliance – ability of blood vessel to stretch per given increase in blood pressure • Compliance differences between blood vessel types (i) veins more compliant than aorta (ii) aorta more compliant than arterioles

Answer 10

b. Elastance – ability of blood vessel to return to original diameter (i) Arterial vessels greater elastance than venous vessels

Answer 11

• Arterial system (i) will not accommodate large blood volume change unless accompanied by large pressure increase • Venous system (i) will accommodate large blood volume change with only small increase of pressure (“reservoir system”)

Answer 12

• Large increases in BP will correspond to increase blood volume in stiff blood vessels (arteriosclerosis, nicotine, etc…)

Answer 13

a. Systolic pressure • Highest arterial pressure during cardiac cycle - measured after ventricular ejection • < 140 mmHg b. Diastolic pressure • Lowest arterial pressure during cardiac cycle - measured during ventricular filling (blood is “passively” filling ventricle) • < 90 mmHg

Answer 14

• Difference between systolic and diastolic pressures (i) Systolic pressure – diastolic pressure = pulse pressure • Pulse pressure is determined by stroke volume • Clinical (i) Any pathology that reduces contraction or filling of ventricle will reduce pulse pressure (ii) Distal pulses “weak” vs “strong”

Answer 15

• Average pressure of arterial system • MAP = Diastolic pressure + 1/3 pulse pressure • Values: (i) Normal MAP values: 70 – 110 mmHg (ii) Minimal MAP values: approximately 50-60 mmHg is threshold to sustain visceral organ health (iii) Maximal MAP values: > 160 mmHg – may elevate CSF and intracranial pressures • NOTE: at higher HR MAP becomes closer to actual average between systolic and diastolic pressure • All changes in MAP are due to change in cardiac output or TPR (total peripheral resistance)

Answer 16

• CVP catheter (i) Assessment of right ventricular function and systemic fluid status • Normal CVP values: (i) 2-6 mm Hg – these are the values of the blood returning to the right atria

Answer 17

(i) “Over-hydration” which increases venous return (ii) Heart failure causing congestion (“back-up”) within right heart chambers (iii) Pulmonary trunk stenosis which limit venous outflow and lead to venous congestion (iv) Positive pressure breathing (mechanical ventilator or bag mask – “pushes/forcing air into lungs”) or physiological straining (v) Summary of ↑ CVP: 1. any pathology resulting in excessive ↑ venous return or ↑ right heart congestion/pressure

Answer 18

(i) “Under-hydration” - hypovolemic shock from hemorrhage, fluid shift, dehydration (ii) Transient: orthostatic – stand up and transient drop in venous return (iii) Negative pressure breathing – mechanical ventilation that “sucks air into the lungs” 1. Patient who have lost motor control of muscles necessary for ventilation 2. Iron lung – polio epidemic in mid-1900’s

Answer 19

approximately 0-10 mmHg 1. Decrease CVP: stand up and transient drop in venous return to the heart, drop in CO (and BP) 2. Increase CVP: exercising muscle enhances venous return to heart which increases CO

Answer 20

(i) Mean CVP: average the highpoint and low points of A wave (ii) The A-wave 1. represents atrial contraction 2. High point of A wave represents right ventricular end diastolic pressure a. Atria is contracted and tricuspid valve is open so pressures of atria and ventricles are equal. (iii) The c-wave 1. Occurs at closure of the tricuspid valve. 2. Peak of C-wave occurs from tricuspid valve bulging back into atrium. (iv) X descent – represents atrial relaxation.

Answer 21

(v) V wave – represents the rise in atrial pressure before the tricuspid valve opens. 1. clinical: Enlarged in tricuspid regurgitation. (vi) Y descent - represents atrial emptying as blood fills the ventricle. (vii) The Z-point 1. Occurs just before the tricuspid valve closes (mid to end QRS) 2. Also can be used as good estimate of right ventricular end diastolic pressure if A-wave not visualized with pathology (A fib is an example).

Answer 22

(i) Balloon-tipped catheter (Swan-Ganz catheter) passed into peripheral vein – right atrium – right ventricle – pulmonary artery – branch of pulmonary artery (ii) When balloon is inflated it is indirectly measure pressures within pulmonary veins and left atrium

Answer 23

• Pulmonary capillary wedge pressure (PCWP) provides an indirect estimate of left atrial pressure (LAP). (i) Direct measurement of LAP isn’t practical: 1. Directly placing a catheter through artery – aorta – left ventricle - then into left atrium isn’t ideal

Answer 24

(i) Evaluate severity of any pathology causing elevated LAP 1. left ventricular failure 2. mitral valve stenosis and regurgitation 3. Aortic valve stenosis and regurgitation (ii) Evaluate pulmonary hypertension (which is really consequence of the above) (iii) Monitor blood volume during hypotensive shock (iv) Monitor and titrate diuretic meds

Answer 25

(i) Normal value of LAP = 8-10 mmHg (ii) Abnormal elevation will cause congestion (“back-up”) into pulmonary system. 1. > 20 mmHg of LAP is threshold at which pulmonary edema may occur

Answer 26

• Any increase in CO without a corresponding decrease in TPR will result in increase in MAP (i) HR, SV, contractility, venous return, and systemic blood volume all influence MAP

Answer 27

• TPR and MAP are directly related | (i) If TPR is decreased then MAP will decrease

Answer 28

stimulate retention of water (i) Released from posterior pituitary gland (ii) Triggers kidney to retain water which will increase blood volume and therefore increase MAP

Answer 29

(i) Renin released by kidney (ii) Renin converts angiotensinogen to Angiotensin I (iii) Angiotensin I is converted to Angiotensin II by the enzyme ACE (angitoensin converting enzyme produced in the lungs) (iv) Angiotensin II stimulates the release of Aldosterone which signals the kidneys to retain sodium 1. water “follows” sodium which results in an increased blood volume and therefore increased MAP (v) Clinical: ACE inhibitors to reduce BP

Answer 30

stimulates excretion of sodium and water 1. The right atria releases ANP in response to elevated atrial stretch 2. ANP inhibits ADH thus encouraging excretion of sodium and water (thus decreasing blood volume and lowering MAP) 3. NOTE: Natriuretic refers to sodium excretion (natriuresis)

Answer 31

• Adenomedullin (i) Synthesized and secreted from endothelium and smooth muscle of BV (ii) Vasodialtion effect on BV…thus decreasing MAP • Insulin (i) One role is to stimulate NO (nitric oxide) from endothelium to dilate blood vessel (thus attempting to lower MAP)

Answer 32

• Increased venous return increases preload-SV/CO and indirectly increases afterload • Venous system can accommodate up to 60% blood volume and still maintain 10 mmHg pressure (thus very compliant blood vessel walls) (i) as opposed to the arterial side which may contain 15% blood volume but have average pressure of 100 mmHg (MAP) • Sympathetic nervous system will stimulate the venous system to contract (decreasing compliance) and thus increasing BP by “pushing more blood through the heart” (i) increases preload which leads to increased SV/CO and afterload • Muscular pump and respiratory pump do the same thing by “contracting” the venous return and “pushing more blood through the heart”

Cardio Mod 4 Flashcards

(56 cards)