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Intergrating Human Physiology Semester 2 > Week 4 Cardiovascular System > Flashcards

Week 4 Cardiovascular System Flashcards

1
Q

Components of the CV Components

A

The heart = A pump that provides continuous linkage with the vascular components

The arterial system= A high-pressure distribution circuit

The capillaries = exchange vessels

The venous system = low pressure collection and return circuit

The blood = a body fluid that transports essential substances ad metabolic waste products

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2
Q

Anatomy of the heart Pericardium

A

Membrane surrounds & protects heart

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3
Q

Anatomy of the heart epicardium

A

External layer composed of fibroelastic & adipose tissue and contains blood vessels, lymphatics and nerves that supply the myocardium

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4
Q

Anatomy of the heart Myocardium

A

Middle layer composed of striated cardiac muscle tissue. Intercalated discs allow electrical impulses (AP) to spread cell-to- cell, resulting in a coordinated and efficient contraction / pump

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5
Q

Anatomy of the heart Endocardium

A

Innermost layer of endothelium overlying thin layer of connective tissue

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6
Q

Anatomy of the heart

A

-Two superior receiving chambers: Atria
-Two inferior pumping chambers: Ventricles
- Interventricular septum separates the right and left sides
- The atrioventricular valves (tricuspid and bicuspid/mitral valve) ensure one-way blood flow between the atria and ventricle
- Myocardial thickness varies according to the amount of stress placed upon it

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7
Q

Pulmonary circulation

A

Right side receives deoxygenated blood from the body (via vena cava) and pumps blood to the lungs

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8
Q

Systemic circulation

A

Left side receives oxygenated blood from the lungs (via pulmonary vein) and pumps blood into the aorta for distribution throughout the body

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9
Q

Coronary circulation

A

The myocardium has its own network of blood vessels called the coronary circulation

• The coronary arteries branch from the ascending aorta and encircle the heart

• Delivers oxygen and nutrients to the heart muscle and collects carbon dioxide and waste, and then moves into coronary veins

• Tissue damage caused by an interruption in blood flow known as infarct. Myocardial infarction (heart attack) caused by blockage in coronary circulation

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10
Q

The vascular system

A

Arteries (conduit vessels)

Arterioles (resistance vessels) control blood flow, feed capillaries

Capillaries (exchange vessels)

Venules

Veins (capacitance vessels)

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11
Q

STRUCTURE OF BLOOD VESSELS

A

Tunica intima (inner lining of vessel)
• Epithelial layer, consisting of endothelial cells lining the lumen of the vessel, and a connective tissue

Tunica media (middle layer)
• Smooth muscle and elastic connective tissue. Primary role is to regulate the diameter of the lumen.

Tunica adventitia (outer covering of vessel)
• Connective tissue mainly collagen fibers. Contains nerves and small blood vessels.

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12
Q

LAYERS OF THE ARTERY WALL

A
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13
Q

DETECTING ATHEROSCLEROSIS

A
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14
Q

CAPILLARIES – EXCHANGE VESSELS

A

Single layer of endothelial cells

• 500 – 2000 capillaries per mm2 of skeletal muscle tissue

• Large surface area + slow rate of blood flow = effective O2 & CO2 exchange

• Precapillary sphincter is a band of smooth muscle that adjusts blood flow into capillaries

• Local blood flow matched to metabolic

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15
Q

THE VENOUS SYSTEM – CAPACITANCE VESSELS

A
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16
Q

THE CONDUCTING SYSTEM & CARDIAC CYCLE

THE CONDUCTING SYSTEM

A

SA node spontaneously depolarize and repolarizes to provide innate stimuli for heart action

SA node
↓
Atria
↓
AV node
↓
AV bundle
↓
Purkinjie fibers
↓
Ventricles

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17
Q

ELECTROCARDIOGRAM (ECG)

A

Depolarization causes contraction
Repolarization causes relaxation of cardiac muscle fibers.

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18
Q

CARDIAC CYCLE

A

The cardiac cycle is a period from the beginning of one heart beat to the beginning of the next one. It can be divided into two basic phases: diastole and systole

Diastole
• Period of the cardiac cycle when the heart muscle relaxes, and blood fills the chambers
• At rest, the heart spends two-thirds of its time in diastole

Systole
• Period of the cardiac cycle when the heart muscle contracts and blood is pumped out of the chambers
• At rest, the heart spends one-third of its time in systole

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19
Q

PRESSURE ACROSS THE CARDIAC CYCLE

A

In Systole
Ventricles eject blood into the arterial system.
To empty, ventricular pressure must be high – equivalent to that in the arterial system

In Diastole
Ventricles fill with blood entering via the atria from the venous system. To fill, ventricular pressure must be low – equivalent to that in the venous system

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20
Q

FLOW ACROSS THE CARDIAC CYCLE

A

a) Atrial contraction forces a small amount of additional blood into the relaxed ventricles

b) Ventricular systole - first phase: Ventricular contraction pushes AV valves closed but does not create enough pressure to open semilunar valves

c) Ventricular systole - second phase: As ventricular pressure rises and exceeds pressure in the arteries, the semilunar valves open and blood is ejected

d) Ventricular diastole – early: As ventricles relax, pressure drops, blood flows back against cusps of semilunar valves and forces them closed. Blood flows into the relaxed atria.

e) Ventricular diastole – Late: All chambers are relaxed. Ventricles fill passively

21
Q

HEART SOUNDS ACROSS THE CARDIAC CYCLE

A
22
Q

CARDIAC CYCLE VOLUMES

A

Venous Return (VR)
• The total blood volume returning to the heart by vena cava into the atria

Ventricular end diastolic volume (EDV)
• Total blood volume in each ventricle at the end of diastole

Ventricular end systolic volume (ESV)
• Total blood volume in each ventricle at the end of systole (ejection)

Stroke Volume (SV)
• The blood volume ejected per beat from each ventricle
SV

23
Q

STROKE VOLUME (SV)

A

60% at rest in healthy active young adult

Ejection Fraction (%) = stoke volume/ end diastolic volume

End diastolic volume (EDV) 100ml b-1
End systolic volume (ESV) 40ml b-1
Stroke volume (sv) 60ml-b-1

24
Q

CARDIAC OUTPUT

A

Cardiac output is the amount of blood pumped by each ventricle in 1 minute.
• Expressed in ml/min or L/min
Cardiac output = heart rate( HR) x stoke volume (SV)

25
Q

Volumes at rest

A

Cardiac output (Q) 6.0 L/min
Heart rate (HR) 75bpm
Stoke volume 80ml

Q= HR X SV

26
Q

Maximal exercise volumes

A

Q= 31.2 L. ^ 420%
HR= 195bpm ^160%
SV 160ml

27
Q

HEMODYNAMICS

A

Blood flow = ΔP/R

Perfusion pressure (Δ P)
• Pressure difference drives blood flow
• Flows from regions of higher (Aorta) to lower (Vena Cava) pressure

Resistance (R)

• Resistance is the force that opposes blood flow
• Dependent on blood viscosity (ƞ), vessel length (L) & radius (r) -
Resistance = [ƞL/r4]
Small changes in vessel dimeter (through vasodilation / vasoconstriction) produce large alteration in resistance and therefore blood flow

28
Q

BLOOD PRESSURE

A

Blood Pressure (BP) refers to the pulsatile force exerted by blood pushing against the walls of the arteries as the heart pumps blood

29
Q

Systolic pressure (SBP)

A

• Highest pressure in artery during ventricular contraction

30
Q

Diastolic pressure (DBP)

A

Lowest pressure in artery during ventricular relaxation

31
Q

Mean arterial pressure (MAP)

A

• Average pressure (geometric mean) over entire cardiac cycle
• MAP = DBP + [0.333(SBP-DBP)]

32
Q

Blood pressure values mm Hg

A

Normal = systolic less than 120 and diastolic less than 80
Elevated s= 120-129 and d less than 80

High blood pressure (hypertension) Stage 1 S (130-139) D 80-90

High blood pressure (hypertension) stage 2 s 140 or higher
D 90 or higher

Hypertensive Crisis higher than 180 an higher than 120

33
Q

BLOOD PRESSURE / FLOW

A

BP and blood flow (BF) vary considerably in the systemic circulation

• Resting BP fluctuates between 120 (systolic) and 80 (diastolic) mmHg in the aorta and large arteries

• Big drop in BP across the resistance vessels due to ↑ CSA

• BF velocity slows down as capillaries branch out
• Capillary BP ~ 30 mmHg
• Venous BP < 10 mmHg

34
Q

Blood pressure

A

Mean arterial BP = Flow x Resistance

Flow = Those that affect the
Cardiac Output
i.e. those that affect the heart
Stroke volume & heart rate

Resistance= Those that affect the systemic vascular resistance (total peripheral resistance, TPR)
i.e. those that affect the circulation
Vascular smooth muscle tone

35
Q

REGULATION OF HEART ACTIVITY

A

INTRINSIC

Cardiac muscle has ‘spontaneous rhythmicity’, allows it to contract without external stimulation

EXTRINSIC

Neural (via ANS)
Hormones (via endocrine system)

36
Q

AUTONOMIC EFFECTS ON THE HEART

A

Rate and strength of contraction can be altered by neural innervation & hormone secretion (chemical) stimulated through activation of Autonomic Nervous System (ANS)
• Epinephrine (Epi) = Adrenaline
• Norepinephrine (NE) = Noradrenaline

Exercise anticipation from higher centres activates sympathetic neurones in the hypothalamus

Vagus nerve fibres slow heart rate and conduction velocity through action of ACh at Sa and av node

Efferent sympathetic fibres increase heart rate and myocardial contractility and dilate coronary arteries

Sympathetic nervous stimulation of adrenal medulla causes epinephrine release

Released epinephrine delivered via blood accelerates SA node discharge, filters coronary vessels and increases myocardial metabolism

37
Q

Central command

A

Feed-forward control: Neural impulses from motor cortex irradiate to autonomic neurons, leading to parasympathetic withdrawal & sympathetic activation

38
Q

Skeletal muscle Mechanoreceptors / Metaboreceptors

A

Receptors in the muscle gather info concerning the mechanical (muscle length/tension etc) and metabolic (amount of metabolite accumulated) condition of the muscle

39
Q

Chemoreceptors

A

Central [medulla] and peripheral [aortic arch & carotid body] receptors activated by ↑ H+ and PCO2 = ↓ blood pH

40
Q

Baroreceptors

A

Receptors in the walls of aortic arch & carotid body monitor arterial blood pressure

41
Q

Cardiac accelerator nerve

A

Increased rate of depolarization in SA node (and AV node) increases HR. Increased contractility of atria and ventricles increases stroke volume

42
Q

Vagus nerves

A

Decreased rate of depolarization in SA node (and AV node) decreases HR

43
Q

Activation of the parasympathetic nervous system (PNS)

A

• Stimulates the release of acetylcholine (neurotransmitter) from the Vagus nerves
• Binds to muscarinic receptors on cardiac cells
• Causes hyperpolarization of cells in SA and AV node = ↓ HR
• At rest, PNS activity predominates; heart under ‘vagal tone’
• An increase of vagal tone slows HR (Bradycardia)
• A decrease of vagal tone increases HR (Tachycardia)
• As exercise begins, there is a ↓ in PNS activity

44
Q

Activation of the sympathetic nervous system (SNS)

A

• Stimulates the release of catecholamines:
o Noradrenaline (neurotransmitter) is released from sympathetic fibers / cardiac accelerator nerves o Adrenaline (hormone) is released from the adrenal gland
• Which activates adrenoceptors (β-receptors) on the cardiac cells
• Causing ↑ HR and ↑ force of ventricles contraction
• The SNS predominates during stress, when HR > 100BPM

45
Q

REGULATION OF STROKE VOLUME (SV)

A

Filling pressure (preload): Starlings law of the heart

Filling’ influenced by End diastolic ventricular stretch

Arterial pressure opposing ejection (afterload)

Contractility:
Sympathetic nerves circulating agents
↑ contractility = ↑ Ejection Fraction

Total peripheral resistance (TPR)

Emptying’ influenced by ventricular contractility & aortic artery pressure

↓ arterial BP during diastole = ↓ Afterload = Semilunar valves open sooner when BP in aorta & pulmonary artery is lower

↑ ventricular stretch prior to contraction = ↑ sarcomere length of cardiac myocyte = ↑ strength of contraction = ↑ EF

46
Q

REGULATION OF BLOOD PRESSURE & FLOW

A

LOCAL= Ability of local blood vessels to dilate / constrict altering regional BF depending on metabolic needs of the tissue

SYSTEMIC

SHORT TERM: Redistribution of systemic BF is controlled by neural mechanisms & hormones
LONG TERM: Changes in blood volume and blood pressure regulated by hormones

47
Q

SYSTEMIC REGULATION OF BP / FLOW

A

Sympathetic vasoconstriction is prominent in blood vessels of the skin, pancreas, GI tract, kidneys and helps to redirect blood flow to vital organs during the ‘fight or flight’ response

Skeletal muscle Mechanoreceptors / Metaboreceptors= Monitor joint movements

Chemoreceptors= Monitor blood acidity

Baroreceptors Monitor blood pressur

Adrenaline released from the adrenal medulla triggers vasoconstriction of most blood vessels (e.g. skin / GI tract) but dilation in others (e.g. muscle)

Postganglionic sympathetic fibers release noradrenaline which binds to α-receptors to cause vasoconstriction of arterioles.

48
Q

Sympathetic stimulation will increase blood pressure by:

A
  1. Increasing the strength (and rate) of the heart beat
  2. Constricting arterioles (vasoconstriction) and so increase vascular resistance
  3. Release adrenaline and increase the strength of the heart beat

Intergrating Human Physiology Semester 2 (18 decks)

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