Week 9 Flashcards
(140 cards)
1
Q
What is the heart and where is it located?
A
A muscular organ in the chest, acting as two pumps that circulate blood to the lungs and the body.
2
Q
What are the two primary functions of the heart?
A
Pump deoxygenated blood to the lungs
Pump oxygenated blood to the body
3
Q
What is the correct sequence of blood flow through the circulatory system?
A
Heart → Arteries → Capillaries → Veins → Heart
4
Q
What is the role of the superior vena cava?
A
It delivers deoxygenated blood from the body into the right atrium.
5
Q
What does the right atrium do?
A
Contracts and sends blood to the right ventricle.
6
Q
What does the tricuspid valve do?
A
Prevents backflow by ensuring blood flows from right atrium to right ventricle only.
7
Q
What does the right ventricle do?
A
Contracts and pumps blood into the pulmonary arteries.
8
Q
What is the role of the pulmonary valve?
A
Prevents backflow; ensures blood flows from right ventricle to pulmonary arteries.
9
Q
What do the pulmonary arteries do?
A
Carry deoxygenated blood to the lungs for oxygenation.
10
Q
What do the pulmonary veins do?
A
Return oxygenated blood from the lungs to the left atrium.
11
Q
What does the left atrium do?
A
Contracts and sends blood to the left ventricle.
12
Q
What does the mitral valve (bicuspid) do?
A
Ensures blood flows from left atrium to left ventricle only.
13
Q
What does the left ventricle do?
A
Contracts and pumps oxygenated blood into the aorta to be sent around the body.
14
Q
What is the function of the aortic valve?
A
Ensures blood flows from left ventricle into the aorta, preventing backflow.
15
Q
What is the role of the aorta?
A
The main artery that distributes oxygen-rich blood to the body.
16
Q
How many valves are there in the heart and what is their purpose?
A
There are four valves that act as one-way doors to keep blood flowing in the correct direction through the heart chambers.
17
Q
What controls the opening and closing of heart valves?
A
Blood pressure changes within each heart chamber.
18
Q
What are the names of the four heart valves?
A
Tricuspid valve
Mitral (bicuspid) valve
Pulmonary valve
Aortic valve
19
Q
What are atrioventricular (AV) valves and what do they do?
A
The tricuspid and mitral valves; they prevent backflow from ventricles to atria.
20
Q
What are semilunar valves and what do they do?
A
The pulmonary and aortic valves; they prevent backflow from arteries to ventricles.
21
Q
What are valve leaflets?
A
Flaps (2 or 3) that open to allow blood through and close to prevent backflow.
22
Q
What causes the sounds of the heartbeat?
A
The closing of heart valves — the valve leaflets slap shut, creating audible sounds.
23
Q
What is the “LUB” sound in the heartbeat?
A
The first heart sound, caused by the closing of the tricuspid and mitral (AV) valves.
24
Q
What is the “DUB” sound in the heartbeat?
A
The second heart sound, caused by the closing of the pulmonary and aortic (semilunar) valves.
25
What tool is used to listen to heart sounds?
A stethoscope.
26
What is the intrinsic conduction system of the heart?
A group of specialised cardiac muscle cells and fibres that initiate and coordinate the heart's rhythmic contractions.
27
Why is the conduction system important?
It synchronises atrial and ventricular contractions, ensuring efficient blood pumping through systemic and pulmonary circuits.
28
What provides the heart with its automatic rhythmic beat?
The intrinsic conduction system, supported by gap junctions and autorhythmic cells.
29
What is the function of the sinoatrial (SA) node?
It’s the natural pacemaker — initiates all heartbeats and determines heart rate.
Located in the right atrium near the superior vena cava.
30
What does the atrioventricular (AV) node do?
It acts as an electrical gateway to the ventricles and delays the impulse, allowing the atria to fully contract before ventricles do.
Located near the tricuspid valve in the right atrium.
31
What is the AV bundle (bundle of His)?
A pathway that receives impulses from the AV node and sends them to the bundle branches.
32
What do the right and left bundle branches do?
They conduct electrical impulses from the AV bundle to the apex of the heart.
33
What are Purkinje fibres?
Fibres that distribute impulses through the ventricular myocardium, causing ventricular contraction.
34
What is the order of signal transmission in the conduction system?
SA node → AV node → AV bundle → Bundle branches → Purkinje fibres
35
What device records the electrical activity of the heart?
An electrocardiograph, producing an ECG (electrocardiogram).
36
What is the P wave on an ECG?
Represents atrial depolarisation, triggering atrial contraction.
37
What does the PQ segment represent?
The time the signal travels from the SA node to the AV node.
38
What does the QRS complex show on an ECG?
Ventricular depolarisation and contraction; atrial repolarisation also occurs but is masked.
39
What does the T wave represent?
Ventricular repolarisation just before ventricular relaxation (diastole).
40
How often does this conduction cycle occur at rest?
60 to 100 times per minute.
41
What is the cardiac cycle?
The complete sequence of events in one heartbeat, including atrial and ventricular systole and diastole.
42
What does "systole" mean?
Contraction of the heart muscle.
43
What does "diastole" mean?
Relaxation of the heart muscle.
44
What happens during atrial diastole?
Blood enters the atria from the vena cava (right) and pulmonary veins (left). AV valves are closed early in this phase.
45
What do the atria do during diastole?
Act as conduits and then pump residual blood into the ventricles.
46
What initiates atrial systole?
The SA node fires, causing atrial depolarisation and contraction.
47
What causes the AV valves to open during atrial systole?
Atrial pressure becomes greater than ventricular pressure.
48
What happens during early ventricular diastole?
Both AV and semilunar valves are closed — this phase is called isovolumetric relaxation.
49
What causes the AV valves to open during ventricular diastole?
Ventricular pressure drops below atrial pressure, allowing blood to flow into ventricles.
50
What is end-diastolic volume (EDV)?
The volume of blood in the ventricles at the end of diastole (also called preload).
51
When does ventricular systole begin?
After the AV node delays the signal, it passes to the bundle of His, then to Purkinje fibres, causing contraction.
52
What happens when ventricular pressure exceeds atrial pressure?
The AV valves close, marking the start of isovolumetric contraction.
53
What is isovolumetric contraction?
Ventricles contract with no change in volume because semilunar valves are still closed.
54
When do the semilunar valves open?
When ventricular pressure exceeds pressure in the outflow tracts, leading to the ejection phase.
55
What is stroke volume (SV)?
The amount of blood ejected from the ventricle during systole.
56
What is end-systolic volume (ESV)?
The amount of blood remaining in the ventricle after systole (afterload).
57
What happens after the ejection phase?
The ventricles enter isovolumetric relaxation, and the atria begin filling, restarting the cycle.
58
What is the Wiggers diagram?
A graph that shows the relationship between pressure, volume, electrical activity, and heart sounds during the cardiac cycle.
59
Which side of the heart is shown in the Wiggers diagram?
The left side (left atrium and left ventricle).
60
What is the main function of the heart?
To pump blood throughout the body, delivering oxygen and nutrients and removing carbon dioxide and waste.
61
What is cardiac output (CO)?
The volume of blood pumped from each ventricle per minute. It indicates how effectively the heart supplies blood to the body.
62
What is the formula for cardiac output?
Cardiac Output (L/min) = Heart Rate (beats/min) × Stroke Volume (L/beat)
63
What is heart rate?
The number of heartbeats per minute.
64
What determines resting heart rate?
The SA node (sinoatrial node) — it fires 60–100 times per minute.
65
What influences heart rate?
The autonomic nervous system and hormones like adrenaline affect SA node activity and heart rate.
66
What is stroke volume (SV)?
The volume of blood pumped by one ventricle per heartbeat.
67
What three main factors determine stroke volume?
Contractility
Preload
Afterload
68
What is contractility?
The intrinsic strength of the heart’s contraction.
↑ Contractility = ↑ Stroke volume = ↑ Cardiac output.
69
What is preload?
The degree of stretch of heart muscle fibres at the end of diastole, related to how much blood fills the ventricle.
70
What affects preload?
Duration of ventricular diastole (longer rest = more filling)
Venous return (more blood returning = more filling)
71
What is afterload?
The pressure the heart must overcome to open the semilunar valve and eject blood.
72
When does ventricular ejection begin?
When left ventricular pressure > aortic pressure, forcing the aortic valve open.
73
What is the function of blood vessels?
They form a closed delivery system that circulates blood throughout the body, beginning and ending at the heart.
74
Are blood vessels rigid like pipes?
No — they are dynamic, able to pulsate, constrict, and relax.
75
What are the three main types of blood vessels?
Arteries
Veins
Capillaries
76
How many layers do artery and vein walls have?
Three layers.
77
What is the innermost layer of arteries and veins?
A lining of endothelium (a single layer of cells).
78
What is the middle layer of arteries and veins made of?
Muscles and elastic fibres.
79
What is the outer layer of arteries and veins made of?
Connective tissue with elastic fibres.
80
How many layers do capillary walls have?
Just one — a single layer of endothelial cells.
81
Why are capillary walls so thin?
To allow for easy diffusion of oxygen and nutrients into tissues.
82
What do veins do?
Carry deoxygenated blood back to the heart from various parts of the body.
83
How do the walls of veins compare to arteries?
Veins have thinner walls and are less elastic than arteries.
84
What special feature do veins have to prevent backflow?
Valves — they prevent the backward flow of blood.
85
What are venules?
Small veins that merge into larger veins, eventually leading to the vena cavae.
86
Where does venous blood return to in the heart?
The right atrium, via the superior and inferior vena cava.
87
Is pressure high or low in veins?
Much lower than in arteries.
88
What are capillaries?
Tiny, thin-walled blood vessels that connect arterioles to venules.
89
What is the function of capillaries?
Site of exchange of oxygen, nutrients, and waste products between blood and tissues.
90
What are capillary walls made of?
A single layer of endothelial cells — extremely thin to allow diffusion.
91
Where are capillaries found?
In networks throughout all tissues and organs.
92
What do arteries do?
Carry oxygenated blood away from the heart to the rest of the body.
93
What is the largest artery in the body?
The aorta, which arises from the left ventricle.
94
How are arteries structured to handle pressure?
They have thick, strong, elastic walls made of smooth muscle and elastic fibres.
95
What are arterioles?
Smaller branches of arteries that lead into capillary beds.
96
Why do arteries have elastic walls?
To withstand and regulate the high pressure from the heart’s pumping action.
97
What is blood pressure?
Blood pressure is the force of blood pressing against the walls of the blood vessels or arteries during each cardiac cycle.
98
Why is maintaining blood pressure important?
Too low pressure = inadequate blood supply to organs. Too high = damage to vessel linings, risk of heart disease or stroke.
99
What happens to blood pressure when blood leaves the heart?
Blood leaves the left ventricle at a high pressure (100–140 mmHg), pushing into arteries against elastic walls.
100
What is systolic blood pressure?
It is the maximum pressure on artery walls when the heart contracts.
101
What is diastolic blood pressure?
It is the pressure on artery walls when the heart relaxes.
102
What is mean arterial pressure (MAP)?
MAP is the average arterial pressure during a cardiac cycle.
103
How is MAP calculated?
MAP = Diastolic BP + ⅓(Systolic BP – Diastolic BP)
104
Why is MAP not a simple average of systolic and diastolic pressure?
Because the heart spends more time resting (diastole) than contracting (systole).
105
What are the three main factors that affect MAP?
Blood volume – More fluid = more pressure.
Total peripheral resistance – More resistance = higher MAP.
Cardiac output – More blood pumped = higher MAP.
106
What drives blood flow through the circulatory system?
The pressure difference (gradient) between arteries and veins, maintained by the heart’s pumping and vessel resistance.
107
Why is the arterial system considered high-pressure?
Because it receives blood directly from the heart during systole, and arteries act as pressure reservoirs due to their elastic and muscular walls.
108
Why does pressure decrease as blood moves through the arteries?
Due to friction and resistance as blood flows through arteries → arterioles → capillaries.
109
Why is the venous system low-pressure?
Blood loses energy after passing through capillaries, and veins have thin, compliant walls that store large volumes at low pressure.
110
Why are arteries called pressure reservoirs?
Their elastic walls store and maintain the pressure from the heart.
111
Why are veins called volume reservoirs?
Their stretchable walls allow storage of large volumes of blood at low pressure.
112
What is venous return?
The flow of blood back to the heart through veins.
113
Why is venous return challenging?
Venous pressure is low, especially in the lower body, and blood must travel against gravity.
114
What three mechanisms assist venous return?
Vein valves – One-way valves stop backflow and direct blood toward the heart.
Skeletal muscle pump – Muscle contractions squeeze veins and push blood forward.
Respiratory pump – Inhalation lowers thoracic pressure and raises abdominal pressure, helping move blood into the heart.
115
Why are venous return mechanisms important?
They ensure effective circulation and adequate return of blood to the heart, which maintains blood pressure and cardiac output.
116
What is the baroreceptor reflex and how does it regulate blood pressure?
The baroreceptor reflex is a fast-acting, negative feedback loop that helps keep blood pressure stable. Baroreceptors in the aorta and carotid bodies detect pressure changes. If pressure drops, they fire less, leading to sympathetic activation (↑ HR, ↑ stroke volume, vasoconstriction). If pressure rises, they fire more, leading to parasympathetic activation (↓ HR, ↓ stroke volume, vasodilation).
117
Where are baroreceptors located, and what do they detect?
Baroreceptors are stretch receptors located in the aortic arch and carotid bodies. They detect changes in blood vessel wall tension caused by blood pressure changes.
118
What happens when blood pressure increases?
Baroreceptors fire more → signals sent to medulla → ↑ parasympathetic, ↓ sympathetic output → ↓ HR, ↓ stroke volume, vasodilation → BP returns to normal.
119
What happens when blood pressure drops (e.g., on standing)?
Baroreceptors fire less → medulla ↓ parasympathetic, ↑ sympathetic → ↑ HR, ↑ stroke volume, vasoconstriction → BP rises back to normal.
120
What is the indirect renal mechanism for regulating blood pressure?
The indirect renal mechanism (RAS) responds slowly (over hours to days) to low BP by increasing blood volume through the renin-angiotensin-aldosterone system.
121
What triggers renin release from the kidneys?
A drop in arterial pressure reduces stretch → baroreceptors are inhibited → sympathetic nervous activity ↑ → juxtaglomerular cells in kidneys release renin.
122
What does renin do in the bloodstream?
Renin converts angiotensinogen (from liver) into angiotensin I, which is then converted into angiotensin II by ACE (angiotensin converting enzyme) in the lungs.
123
What are the effects of angiotensin II?
Causes vasoconstriction (↑ resistance → ↑ BP)
Stimulates thirst and ADH release (↑ water intake and retention)
Increases blood volume → ↑ BP
124
What role does aldosterone play in blood pressure regulation?
Angiotensin II stimulates the adrenal cortex to release aldosterone → kidneys reabsorb more sodium and water → ↑ blood volume → ↑ blood pressure.
125
How do ADH and thirst contribute to blood pressure regulation?
ADH (from the posterior pituitary) promotes water reabsorption by kidneys. The hypothalamus also triggers thirst. Both increase blood volume and restore BP.
126
What are capillaries and what is their function?
Capillaries are the smallest blood vessels with thin walls and tiny pores. They allow water and small solutes to pass but not large proteins. Their function is to enable the exchange of fluid, gases, nutrients, and waste between the blood and body cells.
127
What is capillary exchange?
Capillary exchange is the process where fluid, gases, nutrients, and waste move between blood in capillaries and surrounding body tissues.
128
What are the two main forces involved in capillary exchange?
The two forces are hydrostatic pressure (pushes fluid out of capillaries) and oncotic pressure (pulls fluid into capillaries due to plasma proteins).
129
What happens at the arterial end of a capillary?
Hydrostatic pressure is higher than oncotic pressure, so fluid and nutrients move out of the capillary into the surrounding tissue.
130
What happens at the venous end of a capillary?
Oncotic pressure becomes higher than hydrostatic pressure, so fluid re-enters the capillary from the tissue.
131
What is net filtration pressure (NFP)?
NFP is the difference between hydrostatic pressure and oncotic pressure. It determines whether fluid moves into or out of a capillary.
132
How much fluid returns to the blood via capillaries?
About 90% of the fluid pushed out at the arterial end is reabsorbed at the venous end. The remaining 10% enters the lymphatic system.
133
What is the difference between the pulmonary and systemic circuits of the heart?
Pulmonary circuit: right side pumps deoxygenated blood to the lungs.
Systemic circuit: left side pumps oxygenated blood to the body.
134
What are the phases of the cardiac cycle?
Atrial systole – atria contract, pushing blood into ventricles.
Ventricular systole – ventricles contract (isovolumetric contraction → ejection).
Isovolumetric relaxation – all valves closed, pressure falls.
Ventricular filling – AV valves open, ventricles fill with blood.
135
What determines stroke volume?
Preload: degree of stretch of the heart muscle.
Contractility: strength of contraction.
Afterload: pressure the ventricle must overcome to eject blood.
136
What are the three types of arteries and their roles?
Elastic arteries: near heart; pressure reservoirs.
Muscular arteries: distribute blood to specific organs.
Arterioles: smallest; regulate flow into capillaries.
137
What are the structural differences between capillary types?
Continuous: least permeable, most common.
Fenestrated: have pores; allow filtration (e.g. kidneys).
Sinusoidal: leaky, large gaps; found in liver, spleen.
138
What is resistance in blood flow and what affects it?
Resistance is opposition to flow, affected by:
Vessel diameter (most significant),
Blood viscosity,
Vessel length.
139
What are the components of mean arterial pressure (MAP)?
MAP ≈ diastolic BP + ⅓(pulse pressure)
Pulse pressure = systolic – diastolic.
140
What mechanisms assist venous return despite low pressure?
Skeletal muscle pump,
Respiratory pump,
Venoconstriction.
