Cardiovascular Physiology Flashcards

Question

cardiac output

Answer 1

**per minute** of ventricular contractions = **cardiac output**

Answer 2

1. autonomic nervous system innervation 2. preload on the heart

Answer 3

**parasympathetic:** remember, little innervation to cardiac contractile cells - **acetylcholine** is the neurotransmitter released - decrease Ca²⁺ premeability, so **decreases** strength of contraction and thus decreases **stroke volume** (minimally) **sympathetic:** innervates ventricular cardiomyocytes - **norepinephrine/epinephrine** binds receptors - increases Ca²⁺ permeability, so **increase****s**strength of contraction and thus**stroke volume**

Answer 4

**end diastolic volume (EDV):** amount of blood in the ventricle after atrial systole **stroke volume = EDV - ESV** **end systolic volume (ESV):** amount of blood in the ventricle after ventricular systole

Answer 5

1. autonomic nervous system innervation 2. preload on the heart

Answer 6

**preload:** the "load" on the heart prior to contraction this load is the **end diastolic volume** (EDV) the larger the EDV, the more stretch on the ventricles larger contraction (bigger stroke volume)

Answer 7

an increase in EDV = an **increase** in **period** =\> increases the stretch of the contractile cells of the ventricles =\> increases the force of contraction of these cells upon systole =\> increases the amount of blood ejected from the heart =\> increases stroke volume =\> increase cardiac output

Answer 8

Frank-Starling Law states: "a increase in EDV will cause an increase in stroke volume"

Answer 9

during dynamic exercise 1. muscle pump 2. sympathetic nervous system 3. respiratory pump result = increase SV =\> increase CO₂

Answer 10

remember the SNS affects SA node (HR) and ventricular muscle (SV) but also innervates **blood vessels** - causes a small constriction of veins - increases venous return - increases EDV, SV & CO

Answer 11

**tunica externa** - fibrous connective tissue **tunica media** - smooth muscle - elastic fibres **tunica interna** - endothelial cells

Answer 12

structure and tissue content determines the vessel's function

Answer 13

distribution vessels **structure:** large diameter thin walls compared to diameter lots of elastic =\> easy to distend **blood characteristic****s:** very high blood pressure high blood flow low resistance, small drop in pressure **purpose:** "shock absorbers"

Answer 14

resistance vessels **structure:** small diameter thick walls compared to diameter lots of smooth muscle smooth muscle innervated by SNS **blood characteristics:** large drop in pressure slower blood velocity **purpose:** controls blood flow (vasoconstriction, vasodilation)

Answer 15

1. blood flows down a **pressure gradient** (high to low) 2. but **resistance** decreases flow blood flow = pressure gradient / resistance

Answer 16

**blood flow = (P₁ - P₂) x r⁴**

Answer 17

total blood flow doesn't change with added resistance to an arteriole

Answer 18

exchange vessels **structure:** one endothelial cell thick very thin walls for diffusion **blood characteristics:** low blood pressure, small drop in pressure very low blood velocity huge total cross-sectional area for diffusion **purpose:** exchange of gases, nutrients, etc

Answer 19

more cross-sectional area = slower flow slower flow = maximize exchange

Answer 20

in skin, muscles, lungs, CNS: **Not so permeable** in kidneys, intestines, some other tissues: **More permeable**

Answer 21

**filtration:** movement of fluid **out** of a capillary **reabsorption:** movement of fluid **into** a capillary **Four Starling Forces** 1. capillary hydrostatic pressure (P_c) 2. interstitial fluid hydrostatic pressure (P_IF) 3. capillary plasma osmotic pressure (Π_c) 4. interstitial fluid osmotic pressure (Π_IF)

Answer 22

**capillary:** due to pressure of blood moving through (15 to 35 mmHg) **interstitial fluid:** due to pressure of fluid found here (-3 to +6 mmHg)

Answer 23

movement of fluid due to proteins = osmotic pressures (Π)

Answer 24

1. capillary plasma osmotic pressure (Π_c)(25 mmHg) 2. interstitial fluid osmotic pressure (Π_IF)(1-5 mmHg)

Answer 25

Net filtration pressure = K_f [(P_C + π_IF) - (π_C+ P_IF)] (OUT) (IN) K_f = filtration coefficient (larger = leakier capillary) positive number = filtration negative number = reabsorption

Answer 26

Net filtration pressure = K_f [(P_C + Π_IF) - (Π_C + P_IF)] = 1[(35 + 2) - (25 + 3)] = 1[(37) - (28)] = +9 mmHg

Answer 27

capacitance vessels **structure:** valves large diameter very thin walls compared to diameter some elastic fibers and smooth muscle =\> SNS innervates smooth muscle **blood characteristics:** very low blood pressure medium blood velocity **purpose:**"blood reserve"

Answer 28

increase blood supply to **active** tissues and decrease it to **inactive** tissues increase or decrease heat loss from the body by redistributing blood maintain blood supply to vital organs - heart and brain - at all times main blood pressure (mean arterial pressure)

Answer 29

vasoconstrict (less flow) vasodilate (more flow)

Answer 30

1. local (intrinsic) tissue environment (temp, gases, pressure) 2. humoral (extrinsic) substances in blood 3. neural (extrinsic) nervous system

Answer 31

tissue environment (temp, gases, pressure) autoregulatory mechanisms **1. Myogenic theory** muscle stretch **2. Metabolic theory** metabolic needs

Answer 32

sudden increase in blood pressure **Blood Flow = (P₁ - P₂) x r⁴** =\> stretches walls of arterioles =\> smooth muscle in arteriole walls contract (reflex) =\> vasoconstriction =\> decreases blood flow and pressure after contraction \*this protects the capillaries and maintains normal blood flow

Answer 33

change metabolism, change metabolites and tissue conditions - increase in CO₂ - decrease in O₂ - increase in [H⁺] (increase in acidity = lower pH) - adenosine from adenosine triphosphate (ATP) breakdown - temperature these conditions causes arterioles to vasodilate to increase flow = **vasodilator metabolites**

Answer 34

breathing very quickly means there is less carbon dioxide in blood and reduces blood flow decrease in CO₂ increase in pH vasoconstriction and less blood flow

Answer 35

substances in blood **Vasoconstrictors** 1. Epinephrine - an amine, released upon SNS activation - binds to alpha adrenergic receptors, increase blood pressure on most blood vessels 2. Angiotensin II - a peptide hormone - made during low blood pressure 3. Antidiurtic Hormone (ADH) - a peptide hormone - released during low blood pressure **Vasodilators** 1. Epinephrine - an amine, released upon SNS activation - binds to beta₂ adrenergic receptors, decrease blood pressure in skeletal muscle & heart 2. Atrial natriuretic peptide - a peptide hormone - released during high blood pressure 3. Kinins and Histamine - inflammatory mediators - binds to smooth muscle receptors

Answer 36

nervous system Autonomic Nervous System **1. sympathetic nervous system** - innervates SA & AV node, ventricular muscle - innervates smooth muscle in veins (venous return =\> increases EDV) - innervates smooth muscle in arterioles **2. parasympathetic nervous system** - innervates SA & AV node - no blood vessel innervation - but **indirect effects** because no SNS activation

Answer 37

clinically: Mean Arterial Pressure = diastolic pressure + 1/3 (systolic - diastolic pressure) **recap:** Blood Flow = pressure/ resistance **cardiac output** (CO) = mean arterial pressure (MAP) / total peripheral resistance (TPR) rearrange: MAP = CO x TPR CO = HR x SV

Answer 38

**Negative Feedback Loop** **SET POINT** (Mean Arterial Pressure) =\> **CONTROL CENTRE** (CV centre in medulla) =\> **EFFECTOR** activate SNS or PSNS (Heart and blood vessels) =\> **CONTROLLED VARIABLE** (Mean Arterial Pressure) =\> **SENSORS** (Baroreceptors (mechanoreceptors)) =\> back to **CONTROL CENTRE** (Action Potential)

Answer 39

located in walls of aortic arch, carotid sinuses are stretch sensitive sensors = mechanoreceptors monitor blood pressure send action potential back to CV centre in medulla of brainstem

Answer 40

stretches aorta and carotid sinuses and activates baroreceptors =\> action potential sent to CV centre =\> CV centre compares signals to set point =\> shuts off SNS and activates PSNS =\> decrease Cardiac Output (decrease Heart Rate and Stroke Volume) and causes vasodilation (decrease Total Peripheral Resistance) =\> decreases Mean Arterial Pressure (MAP)