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Medical Physiology 2 > Cardiovascular System > Flashcards

Cardiovascular System Flashcards

1
Q

The conduction velocity of action potentials in the heart is reduced as they pass through which of the following structures?

A

the atrioventricular node

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2
Q

Most of the blood volume in the body is contained within which of the following?

A

Veins

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3
Q

The pressure in the heart when the ventricles are relaxed is known as which of the following?

A

diastolic pressure

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4
Q

Oxygenated blood passes through which of the following?

Pulmonary veins.
Pulmonary arteries.
Left atrium.

A

Pulmonary veins.
Left atrium.

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5
Q

Venous return to the heart is assisted by which of the following?

low resistance of veins
low pressure in the right atrium
valves in veins
the skeletal muscle pump

A

all

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6
Q

The second heart sound corresponds with which of the following mechanical events?

Closing of the aortic valve.
Closing of the tricuspid valve.
Closing of the pulmonary valve.

A

Closing of the aortic valve.
Closing of the pulmonary valve.

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7
Q

Which of the following best describes the function of the tricuspid valve?

it prevents backflow of blood between the right atrium and the pulmonary artery
it prevents backflow of blood between the left atrium and left ventricle
it prevents backflow of blood between the right atrium and right ventricle
it prevents backflow of blood between the right and left atria
it prevents backflow of blood in veins

A

it prevents backflow of blood between the right atrium and right ventricle

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8
Q

Which of the following statements about cardiac pacemaker cells is/are TRUE?

Their membrane potential does not plateau following depolarisation.
Their resting membrane potential is -90 mV.
Their resting membrane potential is not stable.

A

Their membrane potential does not plateau following depolarisation.
Their resting membrane potential is not stable.

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9
Q

The wave on the electrocardiogram that represents ventricular repolarisation alone is which of the following?

A

T

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10
Q

Which of the following will increase mean arterial blood pressure?

  1. Increased heart rate.
  2. Decreased stroke volume
  3. Increased vasoconstriction of the systemic arteries.
A

1 & 3

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11
Q

Why is haematocrit often low in patients with kidney disease?

A

because these patients do not produce sufficient erythropoietin

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12
Q

The stage of the cardiac cycle where the pressure is the greatest within the heart is which of the following?

A

the ventricular ejection phase

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13
Q

Which of the following is/are a function of arterioles?

The control mean arterial pressure.
The regulation of blood flow to different regions of the body.
The transport of blood to capillaries.

A

all

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14
Q

The first and second heart sounds represent which of the following (in order)?

A

closure of the atrioventricular valves and closure of the semilunar valves

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15
Q

What is the difference in resting membrane potential between cardiac muscle cells and pacemaker cells?

A

30mV

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16
Q

the functions of the cardiovascular system

A

Transport of materials around the body:
(i) Between external environment and cells
Oxygen from lungs to cells
Nutrients from digestive tract to cells
(ii) From cell to cell
Hormones from endocrine cells to target cells
Stored nutrients (e.g. liver) to cells
(iii) Between cells and external environment
Carbon dioxide from cells to lungs
Metabolic wastes from cells to kidneys

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17
Q

consequences of cardiovascular system failure

A

Loss of blood supply to brain:
5‐10 seconds – loss of consciousness
2‐3 minutes – brain damage

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18
Q

Know what the major component of the cardiovascular system are how they are related to each other.

A

(i) Blood Vessels (Vasculature)
System that transports the blood around the body.
(ii) Blood
Liquid tissue that carries all the substances being moved.
(iii) Heart
Two‐channelled pump responsible for the movement of the blood.
Right Pump – delivers deoxygenated blood to lungs
Left Pump – delivers oxygenated blood to rest of body

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19
Q

Understand what constitutes the pulmonary and systemic circulations.

A

(i) Pulmonary Circulation
Vessels that connect heart to lungs
- Takes deoxygenated blood from the right hand side of the heart and is transported through the pulmonary artery to the capillaries where we get gas exchange and the oxygenated blood is transported back through the pulmonary arteries and returned to the left hand side of the heart

(ii) Systemic Circulation
Vessels that connect heart to other tissues
- Made up of a large number of circuits
- Oxygenated blood leaves the left hand side of the heart, flows out through arterial system which branches extensively to form capillary networks which provide blood supply to individual cells and systems
- Blood is then collected from those capillaries and transported back to the right hand side of the heart

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20
Q

Be familiar with the macroscopic structure differences between the major types of blood vessels.

A

Arteries
Arterioles
Capillaries
Venules
Veins

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21
Q

Be familiar with the microscopic structure differences of the major types of blood vessels.

A

(i) Tunica Intima
Endothelium - single layer flat epithelial cells
Internal Elastic Lamina - connective tissue with elastic fibre
(ii) Tunica Media
Smooth Muscle
External Elastic Lamina
(iii) Tunica Externa
Connective Tissue
Vaso vasorum - small blood supply to walls of arteries and veins
Relative thickness of these layers varies

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22
Q

Be able to describe the different functions of blood.

A

(i) Distribution
Gases
Metabolic Wastes
Hormones
(ii) Regulation
Body temperature
pH
Fluid Volume
(iii) Protection
Preventing blood loss
Fighting infection

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23
Q

Understand that blood is made up of both plasma and formed elements and know the components of each of these.

A

Viscous, opaque, liquid
~5.5 litres
~ 8% body weight
Liquid tissue so contains both cells and fluid components:
(i) Plasma
~3 litres liquid:
Water
Ions, proteins, nutrients, wastes, gases
(ii) Formed elements
~2.5 litres cells and cell fragments:
Erythrocytes
Leucocytes
Platelets
Haematocrit (or packed cell volume (PCV)):
% blood volume made up of red blood cells
45% males
42% females

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24
Q

Understand how vessel length, vessel radius and blood viscosity impact on blood flow and why.

A

Vessel length:
longer vessel - greater resistance

Vessel radius:
- because of laminar flow & cell - wall collisions: flow slower near vessel wall and faster near centre
- smaller vessel (vasoconstriction)- greater resistance - slower flow
- larger vessel (vasodilation)- less resistance - faster flow
- small changes in radius -> large change in flow
- vessels get smaller as they get further away from the heart

Viscosity:
- blood is 5 x more viscous than water
- caused by friction between: formed elements, proteins and liquid
- flow rate :
increase viscosity -> increase resistance -> decrease flow
decrease viscosity -> decrease resistance -> increase flow
- haematocrit affects viscosity:
increase erythrocytes -> increase haematocrit -> decrease flow
decrease plasma -> increase haematocrit -> decrease flow

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25
how is haematocrit altered
(a) Erythropoietin (EPO) Hormone secreted by kidney In response to hypoxia Stimulates erythrocyte production (b) Recombinant EPO Dramatically ↑ erythrocyte production Improves athletic performance ↑ erythrocyte + ↓ plasma → ↑ haematocrit (Ht) Stroke or heart failure In 2003‐2004 ‐ 8 young elite cyclists died in 13 months (c) Blood Doping Collect own blood and store Retranfuse when needed 2006 Tour De France ‘Operation Puerto’ (d) Polycythaemia vera Red blood cell disease Excessive red blood cells
26
Know who Jean Léonard Marie Poiseuille was, where and when he died as well as the equation that he is famous for.
French physician who died in 1869. Equation allows calculation of flow rate (assuming laminar flow): F = pressure gradient x (pie x radius cubed)/ (8 x viscosity x length of vessel)
27
Be familiar with the macroscopic structure of the heart, its chambers, valves and blood supply.
Chambers: Atria Ventricles - left ventricle wall thicker than right Valves: Atrioventricular valves - left AV value (Bicuspid or Mitral) and right AV valve (Tricuspid) Semilunar valves - pulmonary (towards lungs) & aorta
28
Understand the relationship between the two main heart sounds and the heart valves.
S1 - atrioventricular valves S2 - semilunar valves
29
Be able to describe the microscopic features of cardiomyocytes and how these are connected to form a functional syncytium.
Involuntary Autorhythmicity Striated Branched cells with single nucleus Held together by intercalated discs (Desmosomes & Gap Junctions) Sarcolemma Sarcoplasm Myofibrils Forms functional syncytium
30
Understand the functional properties of the conducting‐system cells and how these are responsible for the initiation and spread of electrical activity in the heart.
Non‐contractile cells (few myofibrils) Initiation & spread of electrical activity Sinoatrial (SA) Node -> atria (contraction) -> Atrioventricular (AV) Node -> Bundle of His -> Purkinje Fibres -> ventricles (contraction)
31
Be able to explain the ionic-basis of the action potential in atrial and ventricular cardiomyocytes.
Depolarising Phase: Opening of Na+ channels Na+ influx Plateau Phase: Closure of Na+ channels Opening of L‐type Ca 2 + channels Ca 2 + influx Repolarising Phase: Closure of L‐type Ca 2 + channels Opening of K+ channels Efflux of K+ N.B. Atrial & ventricular muscle fibres action potentials similar in shape
31
Know the features of cardiomyocyte action potentials.
Resting Membrane Potential (‐90 mV) Depolarising Phase Plateau Phase (0 mV) Repolarising Phase
32
Know the features of pacemaker action potentials.
‘Resting’ Membrane Potential (‐60 mV) Pacemaker Potential (slow depolarisation) Depolarising Phase (0 mV) Repolarising Phase
32
Be able to explain the ionic-basis of the pacemaker potential and action potential in pacemaker cells.
Pacemaker Potential: Opening of F‐type channels Net Na+ influx Opening of T‐type Ca 2 + channels Ca 2 + influx Depolarising Phase: Opening of L‐type Ca 2 + channels Ca 2 + influx Repolarising Phase: Closure of L‐type Ca 2 + channels Opening of K + channels Efflux of K+
33
Understand why the basic rhythm of the heart is set by pacemaker cells in the sinoatrial node.
Pacemaker potential in SA Node is shortest: SA Node = 100 beats/min (bpm) AV Node = 50 bpm Purkinje fibres = 30 bmp Cardiac muscle fibres have an absolute refractory period: 250 ms long Ion channel inactivation Prevents ectopic excitation
34
Be able to explain how and why the sympathetic and parasympathetic divisions of the autonomic nervous system modify heart rate.
Parasympathetic Division: Acetylcholine binds to muscarinic receptors Responsible for ‘rest & digest’ behaviours SA Node Acetylcholine binds to muscarinic receptors Increases duration of pacemaker potential Decreases heart rate Sympathetic Division: Noradrenaline binds to adrenergic receptors Responsible for ‘fight or flight’ behaviours Both spontaneously active Dual innervation of most organs Dynamically opposing effects Noradrenaline binds to β adrenergic receptors Decreases duration of pacemaker potential Increases heart rate Similar effect from adrenaline secreted by adrenal medulla At rest parasympathetic division predominates: Resting heart rate is ~70 bpm Block parasympathetic input (through vagus nerves) Heart rate increases to 100 bpm
34
Understand why conduction disorders affect heart rate and cardiac output.
Drugs or disease can result in abnormal rhythms. E.G. AV conduction disorder: Affects transmission through AV Node Ventricles initiate their own rhythm (slow) Atria and ventricles contract asynchronously Abnormal rhythms can be treated with artificial pacemaker
35
Be able to describe what an electrocardiogram is and the role that Willem Einthoven played in its history.
Electrical activity of heart recorded by electrodes in body surface Synchronous activity Conducting medium Sum of all action potentials occurring in heart Potential Difference (P.D.) Electrodes are referred to as leads Placed on chest wall or limbs Willem Einthoven Nobel Prize for Medicine – 1924 Standard leads are placed on wrists and left leg
36
Know what Einthoven’s triangle is and the different perspective provided by leads 1-3.
Lead I P.D. from RA to LA Lead II: P.D. from RA to LL Lead III: P.D. from LA to LL Provides different views of heart
37
Understand how the electrocardiogram differs from normal in patients with an AV conduction disorder and long QT syndrome and the clinical consequences of these pathologies.
Idealised ECG Waves separated by segments P wave ‐ atrial depolarisation QRS complex ‐ ventricular depolarisation. T wave – ventricular repolarisation Clinically useful Routine monitoring of heart rate Detection of alterations in electrical signalling: AV Conduction Disorder: Action potential delayed or blocked in AV node Long QT Syndrome (LQTS) Congenital disorder Mutation of K+ channels Delayed repolarisation Fainting, cardiac arrest, sudden death
38
Understand what is meant by sinus arrhythmia, how it appears in an electrocardiogram and what causes it.
When there is irregularity in the sinus rate in which the variation in the R-R interval is greater than 0.12 secs
39
Know what is meant by excitation‐contraction coupling in cardiomyocytes and be able to describe the molecular processes responsible.
Contraction: Action Potential in T-tubule -> L-type Ca 2+ channels open, Ca 2+ influx -> opens ryanodine receptor -> large Ca 2+ release from SR -> Ca 2+ triggers shortening of myofibrils Relaxation: Ca 2+ pumped back into sarcoplasmic reticulum + Ca 2+ pumped out of fibre -> decrease in sarcoplasm (Ca 2+) -> lengthening of myofibrils
40
Know the six variables that are typically used to describe the changes in the heart that take place in the cardiac cycle.
41
Be able to describe the four major stages of a single cardiac cycle and the key steps involved in each.
Systole: Ventricles relaxed & pressure low a) Iosvolumetric Ventricular Contraction Initiated by depolarisation of ventricle (--> QRS wave) -> contraction of ventricles -> closure of AV valve (1st heart sound) -> increase ventricular pressure (no change in volume) b) ventricular ejection ventricular pressure > aortic pressure -> aortic valve opens -> blood ejected (stroke volume) -> aortic pressure increase -> ventricular volume decrease -> ventricular relaxation (--> T wave) -> ventricular pressure decrease Diastole: a) isovolumetric ventricular relaxation Ventricular pressure decreases -> aortic valve closes (--> 2nd heart sound) -> no changes in volume b) Ventricular filling Artial pressure > ventricular pressure -> Av valve opens -> blood flows into ventricle -> increase ventricular volume (80%) -> artial systole (--> P wave) -> completes ventricular filling (20%)
42
Understand what stroke volume is and the three factors that can modify its magnitude.
Stroke volume is volume of blood ejected from ventricle during each contraction Controlled by three factors: 1. End-Diastolic Volume 2. Sympathetic Nervous System 3. Afterload
43
1. End-Diastolic Volume
Volume of blood in ventricle after filling is complete The greater EDV the greater the stroke volume Otto Frank & Ernest Starling Frank‐Starling Law of the Heart Mechanism: increase venous return -> increase end-diastolic volume -> stretches myofibrils -> increase force of contraction -> increase stroke volume
44
2. Sympathetic nervous system
Sympathetic neurones innervate ventricles Noradrenaline increases force of cardiac muscle fibre contraction Mechanism: Noradrenaline -> B adrenergic receptors -> increase Ca 2+ release or increase Ca 2+ influx -> increase sarcoplasmic Ca 2+ -> increase force of contraction -> increase stroke volume
45
3. Afterload
Heart has to move blood against arterial pressure If ↑ arterial pressure then ↓ stroke volume Usually only a consideration in chronic hypertension
46
Know what venous return is, why it is important and the factors that can modify it.
Venous return = volume of blood entering right atrium/min Venous pressure low venules = 18 mmHg right atrium = 2 mmHg Little resistance to flow Very compliant ↑ volume with littlechange in pressure Veins can ‘store’ large volumes of blood Venous return affected by a number of variables: (i) Muscular Pump and Valves Contraction of skeletal muscle compresses vein Pumps blood towards heart Valves prevent backflow Significantly increases venous return (ii) Respiratory Pump Heart located in thoracic cavity During inspiration ‐ intrapleural pressure ↓ Decreases pressure in atria Increases pressure gradient Increases venous return (iii) Sympathetic Tone Smooth muscle of veins innervated by sympathetic neurones Noradrenaline binds to α receptors Venous constriction Returns blood to heart Increases venous return
47
Be able to define cardiac output, be able to calculate it and understand how it can change with exercise.
Volume of blood pumped by each ventricle in a minute: Cardiac Output (CO) = Heart Rate x Stroke Volume CO = 72 bpm x 70 ml CO = 5040 ml/min (~ 5 litres/min) Exercise: ↑ by 4‐5 times (20 – 25 litres/min) Athlete: ↑ by 7 times (35 litres/min).
48
Understand how cardiac output can be modified by changes in heart rate, stroke volume, hormones and drugs.
(i) Changes in Heart Rate: Referred to as chronotropic effects ii) Changes in Stroke Volume: Referred to as inotropic effects (iii) Hormones: (a) Adrenaline ↑ Heart rate ↑ Stroke volume (b) Thyroxine ↑ Heart rate ↑ Stroke volume (c) Glucagon ↑ Stroke volume (iv) Drugs: (a) Ivabradine Acts on F‐type channels Prolongs pacemaker potential ↓ heart rate (b) Sympathomimetics β adrenergic receptor agonists ↑ heart rate ↑ stroke volume (c) Beta‐blockers β adrenergic receptor antagonists Reduce sympathetic tone ↓ heart rate ↓ stroke volume
49
Be familiar with the terms systolic pressure, diastolic pressure, pulse pressure and mean arterial pressure.
Systolic pressure (~120 mmHg) Diastolic pressure (~80 mmHg) – maintained by elastic arteries Pulse Pressure = systolic pressure ‐ diastolic pressure Mean Arterial Blood Pressure = diastolic pressure + ⅓ of pulse pressure
50
Be able to demonstrate how to record systolic and diastolic pressure and calculate pulse pressure and mean arterial pressure.
51
Know what the Korotkoff sounds are and be able to explain what causes them.
52
Know what the Harvard step test is and how to administer one.
53
Understand the effects of exercise on heart rate, blood pressure and cardiac output.
54
Understand how blood volume, cardiac output, diameter of veins and the diameter of arterioles all modify blood pressure.
Blood volume: increase in volume leads to an increase in pressure Cardiac output: An increase in cardiac output leads to an increase in blood pressure Diameter of veins: determines resistance of the system to blood flow Diameter of arterioles: When arterioles constrict, the resistance to blood flow increases, leading to an increase in blood pressure. Conversely, when arterioles dilate, resistance decreases, leading to a decrease in blood pressure.
55
Be able to describe how intrinsic and extrinsic controls modify blood flow through arterioles.
(a) Intrinsic (Local) Controls Self‐regulation of arteriole resistance to control blood flow Independent of neural or hormonal input Ensure adequate blood supply to tissues Metabolically active tissues ↓ Local vasodilation ↓ ↓ arteriole resistance --> ↑ local blood flow (b) Extrinsic Controls Sympathetic division of autonomic nervous system: noradrenaline α adrenergic receptors ↑ sympathetic tone – vasoconstriction ↓ sympathetic tone – vasodilation Changes regional (rather than local) blood flow Example: During exercise: ↑ blood flow to skeletal muscles ↓ blood flow to digestive tract Reinforced by adrenaline from adrenal medulla.
56
Be able to explain what orthostatic hypotension is and how the cardiovascular control systems react to restore normal blood pressure.
Orthostatic hypotension is a condition in which your blood pressure suddenly drops when you stand up from a seated or lying position. Rapid & short term control Ensure enough pressure to generate adequate blood flow Especially to the brain and heart Two important elements: (i) Arterial Baroreceptors Stretch sensitive nerve‐endings Carotid arteries Aortic Arch Spontaneously active Detect changes in blood pressure: ↑ BP ↑ actin potentials ↓ BP ↓ action potentials Relay this information to brainstem. (ii) Medullary Cardiovascular Control Center Located in medulla oblongata Collects information from arterial baroreceptors Determines appropriate response Alters sympathetic and parasympathetic tone: Heart Arterioles Veins
57
Be able to describe what capillary exchange is and the mechanisms that enable it.
Movement of materials between blood and tissues Capillaries well adapted for function: Endothelium Small diameter Slow blood flow High density: 50,000 miles of capillaries Most cells with 0.1 mm of capillary Massive surface area 6300 m2 Intercellular spaces Three mechanisms: (i) Diffusion Movement down concentration gradient Across plasma membrane Lipid‐soluble materials by simple diffusion Others by facilitated diffusion Gases, nutrients & metabolic end products (ii) Transcytosis Endocytosis into cell Exocytosis out of cell Non‐lipid soluble macromolecules (iii) Bulk Flow Mass movement of water and small solutes through intercellular spaces Driven by hydrostatic pressure (pushing fluid out of capillary) Opposed by osmotic (oncotic) pressure (sucking fluid back into capillary) Referred to as Starling's Forces:
58
Know what net filtration pressure is and how to calculate it.
NFP = difference between the hydrostatic and the oncotic pressure gradients: NFP = (HPc -HPi) - (OPc -OPi)
58
Understand the mechanisms responsible for the development of oedema following a soft tissue injury.
soft tissue injury -> plasma proteins in interstitial space -> increase interstitial fluid oncotic pressure -> increase filtratin & decrease reabsorption -> oedema
59
60
If cardiac output is 18 L/min, and heart rate is 150 beats per minute, what will the stroke volume be?
120mL 18000mL/150
61
Frank-Starling’s law states which of the following? stroke volume is proportional to end-diastolic volume stroke volume is inversely proportional to resistance blood flow is proportional to pressure differences stroke volume is proportional to cross-sectional area stroke volume is inversely proportional to pressure
stroke volume is proportional to end-diastolic volume
62
Venous return to the heart is assisted by which of the following? low resistance of veins low pressure in the right atrium valves in veins the skeletal muscle pump
all
63
The T wave of an electrocardiogram is associated with which of the following electrical events?
ventricular repolarisation
64
During the early phase of systole, which of the following events occur? Ventricular pressure rises. Ventricular volume decreases. The ventricles contract.
Ventricular pressure rises. The ventricles contract.

Medical Physiology 2 (6 decks)

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