Cardiovascular II

Question 1

Identify characteristics of arteries, veins and capillaries based on location.

Answer 1

Large Arteries: 3mm, oxygenated blood away from heart
Arteries: 100mm, oxygenated blood away from heart
Arterioles: 20-30mm, oxygenated blood away from heart
Capillaries: 7-10mm, gas exchange with surrounding tissues
Venules: 20-30mm, deoxygenated blood towards heart
Veins: 15-24mm, deoxygenated blood towards the heart
Large Veins: 6mm, deoxygenated blood towards heart

Question 2

Identify the layers of an artery and indicate properties of each layer.

Answer 2

1. Tunica Externa: connective tissue (collagen) to provide stability
2. Externa Elastic Membrane: contains elastin fibres; allow for stretching when under high pressure from ventricular contraction; able to recoil driving blood through circulatory system during diastole
3. Tunica Media: smooth muscle
4. Internal Elastic Membrane: contains elastin fibres to allow expansion of vessel under pressure
5. Tunica Interna: endothelium (lines lumen of blood vessel), basement membrane made of glycoprotein and connective tissue, elastin

Question 3

Identify the layers of a vein and indicate properties of each layer.

Answer 3

1. Tunica Externa: connective tissue
2. Tunica Media: smooth muscle
3. Tunica Interna: endothelium (lines lumen of blood vessel), basement membrane made of glycoprotein and connective tissue, elastin

Question 4

Identify the layers of a capillary and indicate the properties of each layer.

Answer 4

Capillaries are made of single layer of endothelium, allowing rapid exchange between blood and tissues.

Question 5

Describe pulse pressure of an artery and how it impacts blood flow.

Answer 5

Pulse Pressure: difference between diastolic and systolic pressure
-can be felt by pulsating artery and feeling expansion
-proportional to stroke volume as pulse pressure and stroke volume increase; difference in blood pressure becomes greater

Question 6

Differentiate between arteries, distributing arteries and arterioles.

Answer 6

Conducting Arteries: largest and more elastic arteries
-capable of expanding to absorb pressure from ventricular contraction and recoil during relaxation
Disturbing Arteries: smaller, more muscular arteries that distribute blood to organ
Arterioles: smallest arteries, that distribute blood to capillary beds
-blood flow controlled at arteriole level by vasoconstriction and vasodilation of smooth muscle layer

Question 7

Discuss continuous capillaries: mechanisms of exchange and where they are located in the mammalian body.

Answer 7

Continuous Capillaries: made of endothelial cells that are closely attached to each other without larger intercellular channels
-movement of very small molecules; water, gases
-exchange is mainly by pinocytosis
-located in adipose tissue, muscle, lungs, CNS (blood-brain barrier)

Question 8

Discuss fenestrated capillaries including: mechanism of exchange and where they are located in the mammalian body.

Answer 8

Fenestrated Capillaries: larger pores ‘fenestra’, increasing exchange of substances across capillary bed
-pores lined with mucoprotein to restrict large molecules (proteins)
-located in endocrine glands, kidneys, intestines

Question 9

Discuss discontinuous capillaries including: mechanism of exchange and where they are located in the mammalian body.

Answer 9

Discontinuous Capillaries: largest opening, for larger components (RBC, WBC, large serum proteins)
-mostly found in the liver, spleen and bone marrow

Question 10

Describe a pre-capillary sphincter and indicate its function.

Answer 10

Pre-Capillary Sphincter: junction between arterial system and capillary beds
-made of smooth muscle at control blood flow into capillary bed by cycles of contraction and relaxation
-group of circular muscle bands that regulate blood flow from the arterioles into the capillaries

Question 11

Differentiate between veins and venules.

Answer 11

Venules: smallest vein, have 2 layers; tunica externa and tunica interna
-contains valves
-collect deoxygenated blood from tissue capillaries and carries blood to progressively larger veins
Veins: larger, have 3 layers; tunica externa, tunica media, tunica interna
-medium veins have valves, larger veins have no valves
-collects blood from venules and delivers it back to the heart

Question 12

Describe mechanisms that facilitate venous return to the heart.

Answer 12

1. Skeletal Muscle Pump: contraction of surrounding skeletal muscles compresses veins and propels blood forward
2. Venous Valves: closure of valves prevents backflow of blood
3. Breathing: contraction of diaphragm during inspiration causes difference in pressure between abdomen (high pressure) and thoracic cavity (low pressure)
   -pressure difference helps pump blood against gravity upward towards the heart

Question 13

Define: flow and perfusion.

Answer 13

Flow: measure of blood flowing through specific tissue in given time (mL/min)
Perfusion: measure of blood flow per given volume or tissue mass in given (mL/min/g)

Question 14

Discuss how blood flow is affected by driving forces and resistance.

Answer 14

-blood flow is determined by pressure difference (from high to low pressure)
-resistance within vasculature is measure of how difficult it is for blood to move through vessel
-greater pressure difference, greater blood flow

Question 15

Identify factors that determine driving forces and resistance.

Answer 15

Driving Forces: difference in pressure
Resistance: radius of blood vessel, blood viscosity, and vessel length

Question 16

Discuss the Poiseuille’s law and relate length of vessel, viscosity of blood, and radius of vessel to resistance.

Answer 16

Poiseuille’s Law: flow is related to blood pressure difference across vascular bed, length of vessels, viscosity of blood and fourth power of vessel radius

Question 17

Identify factors which affect blood viscosity, length of vessels, and vessel radius.

Answer 17

Vessel Radius:
-Vasoconstriction: decrease in vessel radius, increase resistance, decrease blood flow
-Vasodilation: increase vessel radius, decrease resistance, increase blood flow
Blood Viscosity:
-Dehydration - Polythemia: high RBC count due to high altitudes (blood doping) causes increase blood viscosity, increase resistance, decrease blood flow
-vessel length remains constant

Question 18

Define mean arterial pressure.

Answer 18

Mean Arterial Pressure: average blood pressure during one cardiac cycle; major determinant of blood flow = diastolic pressure + 1/3 pulse pressure

Question 19

Indicate average mean arterial pressure in different vessels of the systemic circulation.

Answer 19

Large Arteries: 120-80mmHg
Small Arteries/Arterioles: 100-30mmHg
Capillaries: 30-20mmHg
Venules: 20-5mmHg
Large Veins: < 5mmHg - 0

Question 20

Define: systolic blood pressure, diastolic blood pressure, pulse pressure, hypertension and hypotension.

Answer 20

Systolic Blood Pressure: highest level of arterial blood pressure during ventricular contraction
Diastolic Blood Pressure: lowest level of arterial blood pressure during ventricular
Pulse Pressure: difference in blood pressure between systolic and diastolic blood pressure
Hypertension: chronic high resting blood pressure (>140/90)
Hypotension: chronic low resting blood pressure

Question 21

List the factors that determine blood pressure.

Answer 21

Cardiac output, blood volume, resistance of blood flow.

Question 22

Describe how a pressure cuff and sphygmomanometer measure blood pressure.

Answer 22

-pressure cuff is wrapped around patients arm to constrict brachial artery and restrict blood flow; creates turbulent blood flow through artery causing Korotkoff sounds detected by stethoscope
-pressure within the cuff is measure by a sphygmomanometer
1. At first cuff pressure is too high so artery will be pinched off; no sound (cuff pressure>systolic pressure)
2. Gradual decrease in cuff pressure by releasing air; first Korotkoff sound is heard as blood flows through the constricted artery (systolic pressure) cuff pressure = systolic pressure
3. Continual decrease in cuff pressure until Korotkoff sounds disappear; artery is no longer constricted and return to normal blood flow
-last Korotkoff sound prior to this represents diastolic pressure (cuff pressure = diastolic pressure)

Question 23

Define cardiac output.

Answer 23

Cardiac Output: volume of blood being pumped per minute
CO (mL/min) = Stroke Volume (mL/beat) x Cardiac Rate (beats/min)

Question 24

Indicate how stroke volume and heart rate can alter cardiac output.

Answer 24

Increase in stroke volume and heart rate will increase CO

Question 25

Discuss how autonomic nervous stimulation affects pacemaker potentials of the SA node.

Answer 25

-release of epinephrine and norepinephrine from ANS; cause opening of HCN channels (through the activation of β1-adrenergic receptors and production of cAMP) on the membrane pacemaker cells of the SA node (influx of Na+) increasing rate of depolarization and firing action potentials and increase heart rate -release of acetylcholine from the ANS causes opening of K+ channels, increasing the amount of K+ leaving pacemaker cell; slows down the rate of depolarization, decrease in heart rate

Question 26

Describe how autonomic stimulation of the heart affects HR and CO.

Answer 26

-autonomic stimulations mostly controls HR by affecting SA node -SNS also affects muscle contraction in atria and ventricles -SNS - increase HR, contraction strength, CO -PNS - decrease HR, CO

Question 27

Discuss the location of cardiac control centre and how it mediates changes in HR.

Answer 27

-cardiac control centre is located in medulla oblongata of brain stem -receives information from higher brain areas and sensory information (baroreceptors) and will regulate HR through ANS -cardiac centre contains 2 neural pools: 1. Cardioacceleratory Centre: sends signal via SNS to increase HR 2. Cardioinhibitory Centre: sends signal via PNS to decrease HR

Question 28

Discuss how baroreceptors, chemoreceptors, and proprioceptors can influence HR through the cardiac control centre.

Answer 28

Baroreceptor, chemoreceptors and proprioceptors will send sensory information to cardiac control centre. -Baroreceptors: pressure sensors in aorta and carotid arteries; detect increase in BP and will increase its firing rate to cardiac control centre -Chemoreceptors: pH sensors found in aortic arch, carotid arteries and medulla oblongata; detect changes in blood pH, O2, and CO2 relays information to cardiac control centre to increase HR if pH is low due to slow removal of CO2 -Proprioceptors: receptors found in muscles and joints; sensors are activated upon start of exercise and will quickly relay information to cardiac centre to increase HR

Question 29

Define tachycardia, bradycardia, chronotropic and dromotropic.

Answer 29

Tachycardia: high resting heart rate (>100bpm) Bradycardia: slow resting heart rate (<60bpm) Chronotropic: mechanisms that affect HR; can either be positive or negative Dromotropic: mechanisms that affect conduction speed

Question 30

List the 3 factors responsible for determining stroke volume.

Answer 30

Preload (end diastolic volume), afterload (total peripheral resistance), and contractility

Question 31

Define: preload, afterload, contractility, end diastolic volume, end systolic volume, ejection fraction and total peripheral resistance.

Answer 31

Preload: amount of tensions in ventricular myocardium immediately before it begins to contract -exercise increases preload; increased venous return; stretches myocardium -proportional to the volume of blood at the end of diastole Afterload: amount of resistance imposed on the ventricles after the start of contraction -blood pressure in the arteries just outside of the semilunar valves -proportional to the total peripheral resistance Contractility: strength of a contraction End Diastolic Volume: volume of blood in the ventricles at the end of diastole (refilling) End Systolic Volume: volume of blood that remain in the ventricles following ventricular contraction Ejection Fraction: volume of blood that is ejected by left and right ventricle per heartbeat Total Peripheral Resistance: resistance found in arterial system

Question 32

Discuss how preload and afterload can affect stroke volume and thus CO.

Answer 32

Preload: increase in venous return, cause more blood to return to heart, stretching myocytes increasing tension -increase preload, increase stroke volume and increase in cardiac output -decrease preload, decrease stroke volume and decrease in cardiac output Afterload: blood is pumped from an area of high pressure to low pressure -if the pressure in the arterial system is too high, it's more difficult for the ventricles to pump blood due to the equalization of pressure -increase afterload, decrease stroke volume, and decrease in cardiac output

Question 33

Describe the Frank-Starling Law of the heart.

Answer 33

Frank-Starling Law: intrinsic property of heart, end diastolic volume (EDV) is directly proportional to heart;s contraction strength and so stroke volume -EDV increase, increase stretch of myocardium, increase tension, increase contraction of myocardium, increase stroke volume

Question 34

Describe how autonomic stimulation of the heart affects stroke volume and CO.

Answer 34

-sympathetic stimulation will increase strength of contraction of ventricles; by increasing amount of Ca2+ available to sarcomeres -increase in contractility will increase stroke volume and so cardiac output

Question 35

Define: venous return, compliance, and capacitance vessels.

Answer 35

Venous Return: blood that is returned to the heart Compliance: ability of veins to expand under high pressure due to thinner, less muscular walls Capacitance Vessels: veins are compliant; they are able to store large volumes of blood known as capacitance vessels

Question 36

Identify factors that determine venous return and how that influences CO.

Answer 36

-blood volume, venous pressure (vasocontriction, skeletal muscles pump), negative intrathoracic pressure (breathing) -increase in any of these factors, increase venous return, increase end diastolic volume, increase stroked volume, increase CO

Question 37

Define extrinsic and intrinsic regulation of blood flow.

Answer 37

Extrinsic Regulation: control of blood flow by endocrine system and ANS Intrinsic Regulation: control of blood flow by mechanisms within heart

Question 38

Identify factors that determine intrinsic and extrinsic regulation of blood flow.

Answer 38

Extrinsic: SNS (adrenergic, cholinergic), PNS (cholinergic), hormones (ADH, histamine, prostaglandins) Intrinsic: myogenic controls, metabolic controls

Question 39

Predict changes to blood flow, and total peripheral resistance after autonomic stimulation of peripheral vessels.

Answer 39

SNS: adrenergic (vascular smooth muscle) -vasoconstriction of vessels, increase total peripheral resistance, decrease blood flow SNS: chloinergic (skeletal muscle) -vasodilation of vessels, decrease total peripheral resistance, increase blood flow PNS: cholinergic (digestive tract, genitalia, salivary glands) -vasodilation of vessels, increase blood flow (little to no effect on total peripheral resistance)

Question 40

Discuss the myogenic mechanism that regulates blood flow.

Answer 40

-vascular smooth muscle within organs detects changes in blood pressure; respond to either dilating or constricting blood vessels, to increase/decrease blood flow to maintain constant blood flow regardless of systemic arterial pressure -especially important for brain and kidney

Question 41

Identify metabolic factors that can regulate blood flow.

Answer 41

Metabolic factors that signal for increased oxygen requirement, and increased blood flow: -decrease O2, increase CO2, decrease tissue pH (due to lactic acid buildup + increase CO2), release of K+

Question 42

Describe the baroreceptor reflex.

Answer 42

Baroreceptor Reflex: maintains normal BP through system of arterial baroreceptors; detect changes in BP and relays information to ANS to regulate BP

Question 43

Identify location of baroreceptors, nerves involved and central centres responsible for mediating the baroreceptor reflex.

Answer 43

Baroreceptors are located in aortic arch and carotid sinuses. Nerves: 1. Sensory Neurons: relay information from baroreceptors to control centres via vagus and glossopharyngeal nerves 2. Effector Neurons: sympathetic cardiac nerves/parasympathetic vagus nerves Control/Integration Centres: 1. Vasomotor Control Centre: located in medulla oblongata and controls vasoconstriction, vasodilation 2. Cardiac Control Centre: located in medulla oblongata and regulates cardiac rate (firing of SA node)

Question 44

Predict changes in blood pressure mediated by the baroreceptor reflex after various stimuli.

Answer 44

-decrease venous return will cause a decrease in blood pressure detected by baroreceptors -sensory neurons relay information to integration centres in the medulla oblongata that will: 1. Initiate vasoconstriction of arterioles to increase peripheral resistance 2. Increase cardiac rate, thus cardiac output -both will cause an increase in blood pressure, turning off baroreceptor reflex through negative feedback loop

Question 45

Describe the effects of exercise on cardiac output.

Answer 45

-CO will increase 5X during exercise to meet oxygen demands and removal of waste products -increase in CO is due to increase in stroke volume and cardiac rate Stroke Volume: -increase venous return due to muscle activity and increase respiratory rate/diaphragm movement (increase in preload) -increase ejection fraction due to increase myocardial contractility (Frank-Starling Law) -decrease afterload due to decrease total peripheral resistance (due to vasodilation in skeletal muscle) Cardiac Rate: -increase in sympathetic nerve activity (release of epinephrine, norepinephrine)

Question 46

Define: blood hydrostatic pressure, interstitial hydrostatic pressure, blood colloid osmotic pressure and interstitial colloid osmotic pressure.

Answer 46

Blood Hydrostatic Pressure: blood pressure within capillaries Interstitial Hydrostatic Pressure: pressure of interstitial fluid outside of capillaries Blood Colloid Osmotic Pressure: osmotic pressure exerted by plasma proteins within capillaries Interstitial Colloid Osmotic Pressure: osmotic pressure exerted by proteins within interstitial fluid

Question 47

Identify the Starling forces that mediate exchange of fluid between tissue and capillaries and predict the movement of fluids for each.

Answer 47

1. Blood Hydrostatic Pressure: increase hydrostatic pressure -> fluid movement from capillary into interstitial space 2. Interstitial Colloid Osmotic Pressure: increase interstitial colloid pressure -> fluid movement from capillary into interstitial space 3. Interstitial Hydrostatic Pressure: increase interstitial hydrostatic pressure -> fluid movement from interstitial space into capillary 4. Blood Colloid Pressure: increase blood colloid osmotic pressure -> fluid movement from interstitial space into capillary

Question 48

Discuss why Starling forces favour net filtration at arterial end and net absorption at venous ends of capillaries.

Answer 48

-at arterial end of capillaries: movement of fluid favours net filtration (movement out of capillaries) due to high hydrostatic pressure -at venous end of capillaries: blood hydrostatic pressure is lower and there is net movement of fluid into capillaries (net absorption) due to osmotic pressure of plasma proteins (blood colloid osmotic pressure)

Question 49

Identify factors that could alter the Starling forces and result in edema.

Answer 49

1. High Arterial BP: increase hydrostatic pressure in capillaries, increase movement of fluid out of capillaries into interstitial space 2. Venous Obstruction: increase hydrostatic pressure in capillaries, increase movement of fluid out of capillaries into interstitial space 3. Leakage of Plasma Proteins into Interstitial Fluid: increase colloid pressure in interstitial space, increase movement of fluid out of capillaries into interstitial space 4. Decrease in Plasma Protein: decrease colloid pressure in capillaries , decrease movement of fluid into capillaries (at venular end)

Question 50

Briefly discuss how the kidneys can regulate blood volume by anti-diuretic hormone, aldosterone and renin-angiotensin-aldosterone system, atrial natriuretic peptide.

Answer 50

Anti-diuretic hormone (ADH): low blood volume results in high blood osmolality -detected by osmoreceptors in the hypothalamus -secretion of ADH by the posterior pituitary - stimulate water reabsorption in the kidneys - increased blood volume and osmolality Aldosterone: stimulates reabsorption of salt by the kidneys when dietary intake of salt is low -retention of salt will promote water reabsorption and increase blood volume Renin-Angiontensin-Aldosterone System: renin, triggered by low blood pressure and blood volume, causes increased production of angiotensin II; increased blood volume by stimulating the release of aldosterone from adrenal cortex and stimulating thirst centres in the hypothalamus Atrial Natriutetic Peptide (ANP): hormone that causes increased secretion of Na+ and thus water excretion in the urine, decreasing blood volume

Question 51

Describe how blood volume influences blood pressure.

Answer 51

-BP is directly proportional to CO and peripheral resistance -as blood volume increases; increase in CO -because of increase in stroke volume from high venous return -increase in CO and thus increases BP