The Cardiovascular System

Question 1

WHEN DOES A MYOCARDIAL INFARCTION OCCUR?

Answer 1

When blood circulation to the muscle of the heart itself is blocked

Question 2

WHAT IS DIFFUSION?

Answer 2

The net movement of solute down a concentration gradient, brought about by the innate, randomly-directed jumping around of the solute due to its thermal energy

Question 3

FUNCTION OF THE CARDIOVASCULAR SYSTEM

• Delivery of O₂ and nutrients to each cell
• Removal of CO₂ and waste products from each cell
• Communication between organs through transport of hormones and other extracellular mediator
• Temperature regulation
• Crucial hydrodynamic device in sexual reproduction!

Question 4

WHAT THREE FACTORS DETERMINE BLOOD PRESSURE?

Answer 4

Blood pressure is determined by three main factors – cardiac output (pumping of the heart), the blood vessels or vasculature which not only carry the blood but are responsible for the resistance that creates the blood pressure and the various fluid compartments.

Question 5

Cardiovascular circulation can be divided into the systemic and pulmonary (lung) circuits with the heart as the central pump

Question 6

WHAT TWO CIRCUITS IS CARDIOVASCULAR CIRCULATION DIVIDED INTO?

Answer 6

Systemic and Pulmonary (lung)

Question 7

WHAT IS THE COMPOSITION OF BLOOD?

Question 8

BLOOD DISTRIBUTION AT REST

At rest….most blood is flowing through abdominal organs and _.

Majority of pumping is in parallel which means that all flow through organs is not linked. Some exceptions including intensines which run into liver….carry food. However if blood flow is occulled then reduction in blood to liver

Heart flow is quite small and any small change in flow and therefore oxygen can lead to reduce O₂ and pain (called angina).

Answer 8

Kidneys

Question 9

AT REST, WHERE DOES MOST BLOOD FLOW THROUGH?

Answer 9

Abdominal organs

Kidneys

Question 10

BLOOD VESSELS CONTAIN MULTIPLE CELL LAYERS THAT REGULATE THEIR FUNCTION

Lumen

Endothelial cells (Tunica Intima)

Smooth muscle cells (Tunica Media)

Connective Tissue (Tunica Adventita)

All blood vessels contain endothelial cells but vary in the _ of the smooth muscle and connective tissue.

Answer 10

Thickness

Question 11

BLOOD VESSELS INVOLVED IN THE CIRCULATION

Question 12

THICH LAYER OF ELASTIC SMOOTH MUSCLE ACTS AS A PRESSURE RESERVOIR

Question 13

ARTERIOLES CONTAIN A THIN MUSCULAR WALL AND SMALL LUMEN

Contraction of the smooth muscle regulates the diameter of the lumen:

• Determine blood flow to organs
• Major determinant of mean arterial pressure

Question 14

CAPILLARIES HAVE A SINGLE LAYER OF ENDOTHELIAL CELLS

Exchange of nutrients, oxygen and _ across the capillary wall but NOT proteins.

Intercellular clefts and fused vesicles channels assist the exchange.

Answer 14

Waste

Question 15

WHAT SUBSTANCES ARE EXCHANGED ACROSS CAPILLARY WALLS?

Answer 15

Nutrients

Oxygen

Waste

Question 16

THE SKELETAL MUSCLE PUMP

Return of venous blood to the heart is facilitated by valves and the skeletal muscle pump.

Veins run close to the _ muscle .

Answer 16

Skeletal

Question 17

SUMMARY OF STRUCTURE AND FUNCTION OF BLOOD VESSELS

Question 18

OVERALL STRUCTURE OF THE HEART

Question 19

MAJOR BLOOD VESSELS TO THE HEART

Question 20

INTERNAL STRUCTURE OF THE HEART

Question 21

WHAT DO VALVES DO?

Answer 21

Prevent the backflow of blood (ensures that blood flows in one direction).

Question 22

BLOOD FLOW

Question 23

BLOOD SUPPLY TO THE HEART

• Heart is has an extensive network of blood vessels supplied with oxygenated blood via the coronary arteries.
• Coronary arteries branch off the _ (coming from left ventricle)
• Most deoxygenated blood drains back into the right atrium via a single vein (coronary sinus)

Answer 23

Aorta

Question 24

CORONARY ARTERIAL DISEASE CAN LEAD TO ISCHEMIA AND HEART ATTACKS

Coronary Arterial Disease

• insufficient blood flow (ischemia) is associated with chest pains (angina) often radiating down left arm
• severe blockage leads to damage (death) of the heart region and myocardial infarction or heart attack
• ventricular fibrillation and death (heart attack)

Causes of Coronary Arterial Disease

• Atherosclerosis (thickening of the coronary arteries)
• Blood clot (coronary thrombosis)
• Drugs
• Surgery

Question 25

WHAT DO YOU CALL A BACTERIAL INFECTION IN THE CEREBRAL SPINAL FLUID?

Answer 25

Meningitis

Question 26

**_CEREBRAL SPINAL FLUID (CSF)_** ## Footnote * CSF cushions the brain against damage (brain is floating in CSF). * CSF produced in specialised epithelial cell called choroid _ (500ml/day) * Circulation around brain and spinal cord driven by changes in circulation, respiratory and posture. * Passes into vein via valves at the top of the skull (arachnoid villus) * Bacterial infection in CSF is called meningitis (increased pressure in brain leading to seizures and loss of consciousness)

Answer 26

Plexus

Question 27

WHERE IS CSF PRODUCED?

Answer 27

In a specialised epithelial cell called the choroid plexus

Question 28

**_BLOOD VESSELS AND BLOOD-BRAIN BARRIER_** * Blood vessels ‘dive’ down into the brain. * Capillaries contain tight junction and are less permeable to many substances (blood brain barrier) * Difficult to get drugs and proteins into brain. * Exception is lipophilic molecules such as anaesthetics, alcohol etc . * Brain has no stored glycogen and requires constant supply of glucose and oxygen (damage within minutes) – 15% of resting blood flow * Loss of blood supply and death of neurons - stroke

Question 29

WHAT CAUSES A STROKE?

Answer 29

Loss of blood supply and death of neurons in the brain

Question 30

**_TWO MAJOR FLUID COMPARTMENTS: EXTRACELLULAR AND INTRACELLULAR_** THIS OCCURS IN THE CAPILLARIES

Question 31

**_HOW ARE THE VOLUMES IN THESE COMPARTMENTS MAINTAINED?_**

Question 32

WHAT IS OSMOSIS?

Answer 32

Net diffusion of water across a selectively permeable membrane from a region of high water concentration to one that has a lower water concentration (low particle concentration to high particle concentration)

Question 33

**_OSMOLES_** One osmole (osm) = 1 mole (6.02 x 10²³ ) of solute particles in 1L. FOR EXAMPLE: 1 M glucose = 1 Osm 1 M NaCl = 2 Osm 1 M MgCl2 = 3 Osm Osmolarity is INDEPENDENT of molecular weight

Question 34

**_CELLULAR MEMBRANES_** * Permeable to water * Impermeable to solutes (ions) such as Na+, Cl-, K+ etc * Osmosis determines distribution of water (i.e. size of intracellular and extracellular compartments)

Question 35

WHAT IS OSMOTIC PRESSURE?

Answer 35

The pressure required to prevent osmosis

Question 36

WHAT WOULD HAPPEN IF YOU PUT A CELL INTO A HYPOTONIC SOLUTION?

Answer 36

The cell would swell (due to water moving into the cell).

Question 37

WHAT WOULD HAPPEN IF YOU PUT A CELL INTO A HYPERTONIC SOLUTION?

Answer 37

The cell would shrink (due to water moving out of the cell)

Question 38

**_WHAT IS THE COLLOID OSMOTIC PRESSURE?_** Capillary membrane is semi-permeable. - Permits diffusion of ions, water, oxygen, nutrients and waste - NOT PROTEINS. - Pressure exerted by the higher levels of protein in the plasma compared with the interstitial fluid= draws water back into plasma by osmosis (absorption) - 28mmHg (plasma) – 3mmHg (interstitium) = 25mmHg

Question 39

WHAT IS HYDROSTATIC PRESSURE?

Answer 39

The force exerted by the blood on the capillary walls. Hydrostatic pressure drives blood from plasma into interstitial space

Question 40

**_CAPILLARY NET FILTRATION PRESSURE VARIES BETWEEN THE ARTERIAL AND VENOUS END OF THE CAPILLARIES_**

Question 41

**_BULK FLOW OF FLUID FROM PLASMA_**

Question 42

**_LYMPHATIC SYSTEM_** * Lymph system is parallel vascular system with two major functions: * Draining fluid from the tissues and returning to the cardiovascular system * Maintenance of the immune response

Question 43

WHAT ARE THE TWO MAJOR FUNCTIONS OF THE LYMPH SYSTEM?

Answer 43

* Draining fluid from the tissues and returning to the cardiovascular system * Maintenance of the immune response

Question 44

**_LYMPHATIC SYSTEM: DRAINAGE_** * Fluid (plasma) passes (8L/day) from blood into the interstitial area (surrounds cells in the tissues) * Collects fats from the intestines/liver and deposits into veins * Excess fluid passes into lymph capillaries, through lymph nodes (detection of infection) before passing back to blood stream at the neck (largest is thoracic duct that drains into subclavian vein) * Lymph vessels contain valves and fluid is forced along by action of muscles and breathing (respiration). Larger lymph vessels are surrounded by smooth muscle that contract spontaneously and driven by pacemaker cells (~ heart)

Question 45

**_LYMPHATIC SYSTEM: IMMUNITY_** * Lymph fluid contains white immune blood cells (lymphocytes, macrophages, dendritic cells) * Collects antigens (proteins produced by pathogens) * Antigens recognised by B-lymphocytes in lymph nodes leading to activation of immunity. * B-cell proliferate to produce antibodies. Lymph nodes also contain multiple other immune cells (swelling can occur)

Question 46

**_HEART FAILURE_** Excessive kidney retention of water Increased arteriolar resistance High venous pressure

Question 47

**_DECREASE IN COLLOID OSMOTIC PRESSURE_** Reduction in plasma proteins Loss of proteins in urine (kidney failure) Loss of protein in denuded skin areas (burns) Malnutrition

Question 48

WHAT IS INTRACELLULAR OEDEMA?

Answer 48

Depression of metabolic systems of the tissues and lack of adequate nutrition to the cells e.g. ischaemia: reduced activity of Na+ pumps leads to accumulation of Na+ in cells, causing osmosis of water into cells

Question 49

WHAT IS IT THAT DRIVES HEART RATE?

Answer 49

Heart rate is driven by waves of electrical activity that induce the cardiac muscles to contract

Question 50

**_HEART- BLOOD FLOW_**

Question 51

**_COMPONENTS OF THE CONDUCTION SYSTEM OF THE HEART_** If you cut the nerves the heart continues to beat …..Shows that heart has its own intrinsic beat. Heartbeat is driven by specialised myocytes composed of the sino-arterial node (at the top of the right atrium) and the artrioventricular node. AV node connects atria and ventricles and delays the signal for 0.1ms….allow atrial to contract before ventricle Bundles of his are fast conducting myocytes that connect to the Purkinje fibers. Purkinje fibers are very wide allowing rapid conduction throughout the ventricle and simultaneous contraction.

Question 53

WHAT ARE THE BUNDLE OF HIS?

Answer 53

Fast conducting myocytes that connect to the Purkinje fibers. Purkinje fibers are very wide allowing rapid conduction throughout the ventricle and simultaneous contraction.

Question 54

**_SEQUENCE OF CARDIAC EXCITATION_** Delay at AV node allows atria to contract before ventricles

Question 55

**_WHAT CAUSES THE PACEMAKER CELLS OF THE S-A NODE TO TRIGGER AN ACTION POTENTIAL?_** Low resting membrane potential (-60 to -70 mV) Na+ leakage that leads to depolarization Graph for the SA node cell

Question 56

**_MECHANISM UNDERLYING THE 'SPONTANEOUS' ACTION POTENTIALS IN THE PACEMAKER CELLS (SINO-ATRIAL NODES)_**

Question 57

**_MECHANISM OF CONTRACTION OF THE VENTRICULAR CARDIOCYTES_**

Question 58

WHAT IS IT THAT REGULATES THE CONTRACTION OF CARDIAC MUSCLES?

Answer 58

Calcium ions

Question 59

**_HOW DOES CALCIUM PRODUCE CONTRACTION OF THE CARDIAC MUSCLES?_** The entry of extracellular calcium ions causes the release of calcium from the sarcoplasmic reticulum, the source of about 95% of the calcium in the cytosol.

Question 60

WHAT IS THE REFRACTORY PERIOD?

Answer 60

Time required before it is possible to re-stimulate muscle contraction

Question 61

Cardiac muscle has a prolonged refractory period which allows for ventricles to fill with blood prior to pumping.

Question 62

WHAT SYSTEM REGULATES THE SINO-ATRIAL?

Answer 62

The autonomic nervous system

Question 63

WHAT HAPPENS WHEN YOU STIMULATE THE VAGUS NERVE?

Answer 63

Heart rate decreases

Question 64

**_HEART RATE REGULATION_** ## Footnote Sympathetic system innervates the WHOLE heart Parasympathetic innervates just the SA and AV nodes Both systems are tonically active but parasympathetic dominants at rest

Question 65

**_HEART RATE REGULATION: DECREASING HEART RATE_** Parasympathetic and sympathetic nervous system regulate the rate of depolarisation in the sino-atrial node

Question 66

**_HEART RATE REGULATION: INCREASING HEART RATE_** Parasympathetic and sympathetic nervous system regulate the rate of depolarisation in the sino-atrial node. Both the parasympathetic and sympathetic nerves are tonically active. At rest – parasympathetic dominates and heart rate reduced from 100 to 70

Question 67

WHAT DO YOU CALL A LOW HEART RATE?

Answer 67

Bradycardia

Question 68

WHAT DO YOU CALL A FAST HEART RATE?

Answer 68

Tachycardia

Question 69

WHAT ARE THE EVENTS THAT OCCUR TO DECREASE HEART RATE?

Answer 69

Question 70

WHAT ARE THE EVENTS THAT OCCUR TO INCREASE HEART RATE?

Answer 70

Question 71

WHAT DOES AN ELECTROCARDIOGRAM DO?

Answer 71

Measures the electrical activity of the heart.

Question 72

**_EINTHOVEN'S TRIANGLE_**

Question 73

AN ECG IS A SUMMATION OF THE SPREAD OF ACTION POTENTIALS THROUGH THE VARIOUS SECTIONS OF THE HEART. TRUE OR FALSE?

Answer 73

TRUE

Question 74

**_ELECTRICAL EVENTS OF THE CARDIAC CYCLE_**

Question 75

**_SUMMARY OF THE MEANING OF THE DEFLECTIONS OF THE ELECTROCARDIOGRAM_** ## Footnote P - Atrial depolarization QRS - Ventricular depolarization T - Ventricular repolarization PQ segment – Atrial contraction QT segment – Ventricular contraction

Question 76

**_ECG IS A POWERFUL TOOL FOR DIAGNOSING HEART DISEASE_** Provides valuable information concerning the electrical but NOT _ activity of the heart Heart rate Heart rhythm Disturbances of rhythm and conduction (arrhythmia, pacemaker) Conduction velocity Anatomical orientation of the heart Relative size of chambers Condition of tissue within the heart Damage to the myocardium Influence of certain drugs

Answer 76

Mechanical

Question 77

AN ECG PROVIDES VALUABLE INFORMATION CONCERNING THE MECHANICAL ACTIVITY OF THE HEART BUT NOT ELECTRICAL. TRUE OR FALSE?

Answer 77

FALSE Provides electrical but not mechanical

Question 78

WHAT IS THE RESULT OF VENTRICULAR FIBRILLATION, AND WHAT IS IT CAUSED BY?

Answer 78

RESULT: * Random Firing of hearts * Fibrillating ventricles cannot pump blood * Fatal after a few minutes CAUSED BY: * Myocardial Infarction (heart attack) * Electrical shock * Drug intoxication * Impaired cardiac metabolism

Question 79

WHAT IS THE TREATMENT FOR VENTRICULAR FIBRILLATION?

Answer 79

CPR followed by electronic defibrillator

Question 80

HOW DO YOU CALCULATE CARDIAC OUTPUT?

Answer 80

Heart rate x Stroke volume

Question 81

**_HEART STRUCTURE_**

Question 82

WHAT TWO PHASES CAN THE CARDIAC CYCLE BE DIVIDED INTO, AND WHAT HAPPENS IN EACH OF THESE PHASES?

Answer 82

Systole – ventricular contraction and blood ejection Diastole – ventricular relaxation and blood filling .

Question 83

BLOOD PRESSURE IS INCREASED AS IT PASSES FROM ARTERIES TO VEINS. TRUE OR FALSE?

Answer 83

FALSE It decreases

Question 84

**_STAGE 1: SYSTOLE- VENTRICULAR CONTRACTION AND BLOOD EJECTION_**

Question 85

**_STAGE 2: DIASTOLE- VENTRICULAR RELAXATION AND BLOOD FILLING_**

Question 86

SEARCH UP HOW THE HEART WORKS (THE SERIES OF CONTRACTIONS AND RELAXATION SEQUENCE)

Question 87

WHAT CAUSES THE HEART SOUNDS THAT YOU HEAR THROUGH A STETHOSCOPE?

Answer 87

The opening and closing of valves

Question 88

**_HEART SOUNDS THROUGH A STETHOSCOPE_** 1st sound – closure of the atrioventricular (AV) valves ‘lub’- onset of systole (contraction) 2nd sound – closure of pulmonary and aortic valves ‘dub’- onset of diastole (relaxation)

Question 89

WHAT IS A SEPTAL DEFECT?

Answer 89

A hole in the heart

Question 90

WHAT IS STENOSIS?

Answer 90

Narrowed vessels

Question 91

**_REGULATION OF STROKE VOLUME_**

Question 92

**_FACTORS THAT INFLUENCE THE END DIASTOLIC VENTRICULAR VOLUME (PRELOAD)_**

Question 93

VENTRICLES CONTRACT WITH MORE FORCE WHEN THEY CONTAIN MORE BLOOD. TRUE OR FALSE?

Answer 93

TRUE

Question 94

**_FRANK-STARLING MECHANISM MAINTAINS BALANCE BETWEEN RIGHT AND LEFT SIDES OF THE HEART- STOP ACCUMULATION OF BLOOD IN THE LUNGS_** ## Footnote * If there is an _ in venous return to right ventricle then there will also be an _ in contraction= more blood to lungs * If there is an increase in venous return to left ventricle then there will also be an increase in contraction= higher stroke volume= blood doesnt accumulate in lungs

Question 95

**_OVERALL REGULATION OF CARDIAC OUTPUT_**

Question 96

WHAT IS CONGESTIVE HEART FAILURE (CHF) CHARACTERISED BY?

Answer 96

Reduced cardiac output

Question 97

WHAT ARE SOME SYMPTOMS OF CONGESTIVE HEART FAILURE?

Answer 97

Tiredness Shortness of breath Coughing Swelling in ankles and legs Excess of fluid in lungs (Pulmonary edema) Swollen abdomen Excess of fluid around the lungs (Pleural effusion)

Question 98

**_CHRONIC LEFT VENTRICULAR FAILURE (MOST COMMON)_** RISK FACTORS * Coronary artery disease leading to ischaemic heart disease and myocardial infarction (~ 65%) – systolic dysfunction * Hypertension (high blood pressure) (~ 10%) – diastolic dysfunction * Cardiomyopathy (viral infection, heavy drinking) * Getting old!!!

Question 99

**_HEART FAILURE: SYSTOLIC DYSFUNCTION (VENTRICULAR EJECTION)_** Myocardial infarction --\> Damage to heart muscle --\> _ in ventricular contractility --\> Decrease in stroke volume

Answer 99

Decrease

Question 100

**_HEART FAILURE: DIASTOLIC DYSFUNCTION (VENTRICULAR FILLING)_** High Blood Pressure (Hypertension) --\> Increase in arterial _ --\> Increase in cardiac resistance --\> _ in ventricular muscle (hypertrophy) --\> stiffening of ventricular wall --\> End-diastolic ventricular volume --\> _ in stroke volume.

Answer 100

Pressure Increase Decrease

Question 101

HOW DO YOU CALCULATE MEAN ARTERIAL PRESSURE (BLOOD PRESSURE)?

Answer 101

Cardiac output x Total Peripheral Resistance

Question 102

WHAT DOES POISEUILLE'S LAW DESCRIBE?

Answer 102

Describes the factors that determine the flow through a tube in terms of pressure, flow and resistance

Question 103

**_POISEUILLE'S LAW_** **_(THIS IS ABOUT TUBES, NOT SPECIFICALLY BLOOD VESSELS)_**

Question 104

**_POISEUILLE'S LAW: BLOOD VESSELS_** Flow (Q) is directly proportional to the pressure gradient (P) vessel and the radius⁴ (r⁴) of the tube and inversely proportional to the length (L) of the vessel and to the viscosity (η) of the fluid.

Question 105

**_THE CARDIOVASCULAR SYSTEM CAN BE EQUATED TO POISEUILLE'S LAW_** Flow (Q) is proportional to the pressure gradient (ΔP ) and inversely proportional to the resistance: Q = ΔP / R Flow (Q) = cardiac output (L/min) Pressure gradient (ΔP ) = Blood pressure (mmHg) Resistance (R) = Peripheral resistance Cardiac output = Blood pressure/Peripheral resistance Blood pressure = Cardiac Output x Peripheral resistance

Question 106

HOW CAN YOU CALCULATE CARDIAC OUTPUT NOT USING HEART RATE AND STROKE VOLUME?

Answer 106

Cardiac output = Blood pressure/Peripheral resistance

Question 107

BLOOD IS PROPORTIONAL TO PRESSURE DIFFERENCE, BUT INDEPENDENT OF THE ABSOLUTE PRESSURE. TRUE OR FALSE?

Answer 107

TRUE

Question 108

**_FLOW IS INVERSELY PROPORTIONAL TO THE LENGTH AND VISCOSITY_** ## Footnote **Length (L)** * Longer the tube = more resistance = less flow * remains constant and therefore does NOT control blood flow **Viscosity (η)** Higher the viscosity (i.e. treacle) = more resistance = less flow Viscosity is related to the hematocrit (red blood cells/erythrocytes) * Dehydration * High altitude * Erythropoietin (EPO) – stimulate production RBC Remains constant under physiological conditions and therefore does NOT control blood flow

Question 109

WHAT IS THE MOST IMPORTANT FACTOR/CHARACTERISTIC OF A VESSEL IN DETERMINING (FLOW) RESISTANCE?

Answer 109

The radius of the vessel

Question 110

**_RADIUS OF THE VESSEL (THE MOST IMPORTANT FACTOR WHEN DETERMINING (FLOW) RESISTANCE)_** **Radius (r)** * Caused by the _ of the fluid against the vessel wall * The effect of changes in the radius is raised to the power of 4 * Reducing radius by two fold from 2 to 1 reduces flow by sixteen fold (i.e. resistance increased sixteen fold) * Possible to regulate the radius of blood vessels using smooth muscle.

Answer 110

Friction

Question 111

WHAT IS TOTAL PERIPHERAL RESISTANCE?

Answer 111

The sum of the resistance of all the blood vessels and determines blood pressure

Question 112

**_VASCULAR SMOOTH MUSCLE_**

Question 113

WHAT IS TOTAL PERIPHERAL RESISTANCE PRIMARILY REGULATED BY?

Answer 113

Arterioles

Question 114

WHERE DOES BLOOD MOSTLY FLOW THROUGH WHEN AT REST?

Answer 114

Abdominal organs Kidneys

Question 115

ARTERIOLES DETERMINE BLOOD FLOW TO DIFFERENT ORGANS. TRUE OR FALSE?

Answer 115

TRUE

Question 116

**_DETERMINING BLOOD PRESSURE_**

Question 117

**_MEASURING ARTERIAL BLOOD PRESSURE_**

Question 118

WHAT CAUSES THE PULSE?

Answer 118

Vibration of the arteries caused by the ejection of the blood from the heart (left ventricle) into the systemic circulation.

Question 119

WHAT IS THE TYPICAL RESTING PULSE RATE?

Answer 119

70/min

Question 120

WHAT IS THE TYPICAL PULSE RATE AFTER EXERCISE?

Answer 120

220/min

Question 121

WHAT ARTERY IN THE WRIST CAN YOU MEASURE YOUR PULSE FROM? WHAT ABOUT IN YOUR NECK?

Answer 121

Wrist= radial artery Neck= corotid artery

Question 122

HOW DO YOU CALCULATE PULSE PRESSURE?

Answer 122

It's the difference between your systolic and diastolic pressure (e.g. 120-80=40mmHg)

Question 123

**_MEAN ARTERIAL PRESSURE (MAP)_** Mean arterial pressure (MAP) is the average pressure over the cycle - since diastole is twice as long as the systole = diastolic pressure (DP) + 1/3 pulse pressure (PP) = 80 + 1/3 (40) = 93mmHg

Question 124

**_BLOOD PRESSURE IS INFLUENCED BY HEIGHT_**

Question 125

**_BLOOD PRESSURE AND POSTURE_** Heart = ‘zero pressure point’ Standing Increased pressure of mean arterial blood pressure in legs (from 90 to 195 mmHg) leads to pooling of blood in the veins * Feet swelling on flights * Fainting in stationary soldiers However, since arterial and venous blood are at the same height. Blood gradient Delta-P = constant = blood flow continues

Question 126

**_HYPERTENSION IS ASSOCIATED WITH INCREASED MORTALITY_**

Question 127

WHICH RECEPTORS REGULATE MEAN ARTERIAL PRESSURE (MAP)?

Answer 127

Baroreceptors

Question 128

WHERE ARE ARTERIAL BARORECEPTORS LOCATED?

Answer 128

In the aortic arch and carotid sinuses

Question 129

**_ARTERIAL BARORECEPTORS_** ## Footnote Baroreceptor neurons function as sensors in the homeostatic maintenance of mean arterial pressure (MAP). Located in the aortic arch and _ sinuses where they monitor pressure.. Located in thinner walls that can be stretched (by pressure) Baroreceptor nerve endings are sensitive to stretch and _ in artery

Answer 129

Carotid Pressure

Question 130

**_ARTERIAL BARORECEPTORS ACT AS PART OF A NEGATIVE FEEDBACK PATHWAY THAT REGULATES MEAN ARTERIAL PRESSURE VIA THE BRAIN (CENTRAL CONTROL)_**

Question 131

_AUTONOMIC NERVOUS SYSTEM_ **Sympathetic nerves** * mediated by noradrenaline via beta-adrenergic receptors * alpha-1-adrenergic receptors in arterioles (except skeletal muscle which is a2-adrenergic ) * increase cardiac output and peripheral resistance **Parasympathetic nerves** * mediated by acetycholine via muscarinic receptors * inhibit heart rate

Question 132

**_STANDING UP (ORTHOSTASIS)_** * Standing and effect of gravity leads to blood pooling in legs (up to 500ml) * Reduced blood volume and lowering of central venous pressure * Reduced venous return, reduced end-diastolic pressure, reduced stroke volume and reduced blood pressure * Baroreceptor reflex will compensate * Standing and effect of gravity leads to blood pooling in legs (up to 500ml) * Reduced blood volume and lowering of central venous pressure * Reduced venous return, reduced end-diastolic pressure, reduced stroke volume and reduced blood pressure * Baroreceptor reflex will compensate

Question 133

**_AUTONOMIC NERVOUS SYSTEM_**

Question 134

WHAT CAN CAUSE HYPOTENSION?

Answer 134

Blood loss Loss of salts Stress or emotions

Question 135

WHERE IS MOST BLOOD DISTRIBUTED AT REST?

Answer 135

In the veins

Question 136

**_BLOOD VOLUME IS AN IMPORTANT LONG-TERM REGULATOR OF MEAN ARTERIAL PRESSURE_** * Baroreceptors can regulate short term (seconds-minute) changes in blood pressure * Changes in blood volume regulated by the kidneys are responsible for long-term regulation of blood pressure (renin-angiotensin system)

Question 138

WHAT THREE FACTORS REGULATE BLOOD FLOW? (ARTERIOLE RADIUS)

Answer 138

Local Neuronal Hormonal

Question 139

**_INTRINSIC (LOCAL) CONTROL OF ARTERIOLE VASODILATION AND VASOCONSTRICTION_** **_Local factors_** Myogenic Response * Vasoconstriction of arterioles caused by stretch of smooth muscle * Brain, kidney and heart – not skin Vasodilation induced by metabolites: * O2 ↓, CO2 ↑, * H⁺ ↑, adenosine ↑, K⁺ ↑, osmolarity↑ Autocoids * Mainly release as a result of inflammation and bleeding * Histamine, bradykinin, prostaglandins etc **_Endothelial cells (sheer stress)_** * Release local factors (paracrine) * Nitric oxide and prostacyclin (vasodilation) * Endothelin-1 (vasoconstriction)

Question 140

WHEN WOULD AUTOCOIDS MAINLY BE RELEASED?

Answer 140

As result of inflammation or bleeding

Question 141

**_INTRINSIC (LOCAL) REGULATION OF BLOOD FLOW_** * Increase metabolic activity leading to ACTIVE HYPEREMIA * Reduce blood flow in organ leading to FLOW AUTOREGULATION

Question 142

**_NEURAL CONTROL OF ARTERIOLES VASODILATION AND VASOCONSTRICTION (FROM BRAIN)_** _Skin_ Room Temperature •Arterioles constricted by moderate rate of sympathetic discharge Cold, Fear or Loss of blood * Sympathetic discharge increased and arterioles vasocontriction * Divert blood to essential organs Increased Body Temperature * Sympathetic discharge reduced and arterioles vasodilation * Blood flow to skin to facilitate body cooling

Question 143

**_HORMONAL CONTROL OF ARTERIOLE VASODILATION AND VASOCONSTRICTION_**

Question 144

WHAT HAPPENS WHEN YOUR BODY TEMPERATURE INCREASES?

Answer 144

* Sympathetic discharge reduced and arterioles vasodilation * Blood flow to skin to facilitate body cooling

Question 145

WHAT HAPPENS WHEN YOU'RE COLD, IN FEAR OR HAVE LOST A LOT OF BLOOD?

Answer 145

* Sympathetic discharge increased and arterioles vasocontriction * Divert blood to essential organs

Question 146

WHAT HAPPENS WHEN YOUR BODY IS AT ROOM TEMPERATURE?

Answer 146

Arterioles constricted by moderate rate of sympathetic discharge

Question 147

**_EXERCISE AND THE RESPONSE OF THE CARDIOVASCULAR SYSTEM_** Major problems to address: 1. Boost O₂ uptake and CO₂ removal (increased cardiac output) 2. Increase blood flow to muscles, heart and skin (changes peripheral resistance) 3. Stabilise arterial blood pressure (despite changes in cardiac output and peripheral resistance)

Question 148

DURING EXERCISE, WHICH PARTS OF THE BODY RECEIVE AN INCREASED BLOOD FLOW, AND VICE VERSA?

Answer 148

Increased blood flow= Skeletal muscle, skin, heart Decreased blood flow= Kidneys, abdominal organs

Question 149

**_EXERCISE: DIVERT FLOW TO THE SKIN, MUSCLES AND HEART_**

Question 150

**_VALSALVA MANOEUVRE_** TURN OVER TOO

Answer 150

Question 151

**_SUMMARY_**