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HOM: cardiovascular physiology > Lecture 1: overview > Flashcards

Lecture 1: overview Flashcards

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1
Q

What Einstein’s equation showing the reletionship between diffusion time and distance?

A

t α x2

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2
Q

What is the average distance of a neuromusclular gap?

How long does it take for diffusion to occur across this?

A

0.1µm

5x10-6 s

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3
Q

What is the average distance of a diffusion across a capillary wall?

how long does this take?

A

1µm

5x10-4 s

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4
Q

What is the average diffusion distance from a cell to a capillary?

How long does this take?

A

10µm

0.05s

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5
Q

What is the distance across the ventricle wall?

How long would it take for blood to diffuse across this distance?

A

1cm

15.5 hours

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6
Q

Why is pressure in the lungs low?

A

More time for diffusion since blood travels at a lowe velocity

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7
Q

What is William Harvey known for?

A

First person to describe the properties of blood being pumped around the body by the heart

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8
Q

How much blood is pumped by the human heart over the average lifetime?

A

200,000,000 litres

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9
Q

What is the ‘skeleton’ of the heart made from?

What does this form?

A

Collagen

Junction between atria and ventricles

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10
Q

Where are the cardiac valves held?

A

The annulus fibrosus

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11
Q

What is the epicardium?

A

A serous membrane that forms the innermost layer of the pericardium, attached to the muscles of the wall of the heart.

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12
Q

What is the myocardium?

A

The muscular tissue of the heart (middle layer)

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13
Q

What is the endocardium?

A

The thin, smooth membrane which lines the inside of the chambers of the heart and forms the surface of the valves

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14
Q

What are the 3 layers of all blood vessels, except capillaries?

A

Tunica intima

Tunica media

Tunica adventitia

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15
Q

What is the tunica intima?

A

The single layer of endothelial cells and the supporting internal elastic lamina lining the inside of vessels

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16
Q

What is the tunica media composed of?

A

A dense population of smooth muscle cells organised concentrically with bands or fibres of elastic tissue

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17
Q

What is the tunica adventitia composed of?

A

A collagenous extracellular martix containing fibroblasts, blood vessels and nerves

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18
Q

What is the function of the tunica adventitia?

A

Adds rigidity anf form to the blood vessel

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19
Q

Which layer of blood vessels varies most?

Why is this?

A

Tunica media

Allows large elastic arteries to stretch and recoil during systole and diastole to smooth pressure surges

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20
Q

Nearly all cells in the body are within what distance of a capillary?

A

10µm

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21
Q

Does most resistance come from arteries or veins?

A

Arteries

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22
Q

Why do veins offer low resistance?

A

Large cross-sectional area

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23
Q

How do veins prevent backflow of blood?

A

Pocket valves

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24
Q

What proportion of blood in the system is stored in the veins at any given time?

A

2/3

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25
How do large vessels receive their blood supply?
Via the vasa vasorum
26
How are valves useful in venepuncture?
Adding pressure to valves makes veins more superficial
27
Where are nociceptive fibres located within blood vessels?
Tunica adventitia
28
Does fetal haemoglobin have a higher or lower affinity for oxygen than maternal haemoglobin?
Higher
29
What does P50 represent in terms of oxygen saturation? Is this value higher in fetus or mother?
The partial pressure of oxygen at which 50% of the haemoglobin is saturated Mother
30
What are the axis of the oxygen dissociation curve? What shape does it form?
X: Partial pressure of oxygen Y: Oxygen saturation of haemoglobin Sigmoidal
31
What is preferential streaming in the fetus important?
Ensures adequate supply of oxygenated blood to tissues most at risk of hypoxic damage e.g. the brain
32
What are the fetal shunts?
Ductus venosus Ductus arteriosus Foramen ovale
33
Where does the ductus venosus shunt blood to?
Placenta to right atrium of fetal heart, bypassing most of the fetal liver circulation
34
Where does the ductus arteriosus shunt blood?
Pulmonary artery to descending aorta
35
Where does the foramen ovale shunt blood?
Right atrium to left atrium
36
How much blood enters the ventricles when the atria are relaxed?
80%
37
What is the atrial kick/boost?
increased flow into the ventricles via atrial contraction during increased exercise
38
Does all blood travel forwards during atrial contraction? Why is this?
No A small amount of blood is forced backwards into the venae cavae because there are no one-way valves to prevent backflow Backflow is reduced by narrowing of veins during contraction
39
What causes the pulse seen in the jugular vein? When is this pulse most visible?
Backwards movement of blood from right atrium to venae cavae during atrial contraction When person is lying horizontally with head and chest elevated at 30º
40
What is indicated by a jugular pulse located higher on the neck when sitting upright?
High right atrial pressure
41
What is meant by isovolumetric contraction?
Ventricular contraction without any change in ventricular volume (AV and SL valves closed)
42
Why do large elastic arteries become distended during ventricuar ejection?
Ventricular blood enters the aorta faster than it can leave
43
What is the reason for the dicrotic notch?
Small amount of backflow as ventricular pressure falls below arterial pressure, causing closure of SL valves
44
What proportion of blood flow out of the ventricle is due to contraction? What causes the movement of the remaining blood?
2/3 Kinetic energy
45
What is the term for listenning to heart sounds?
Auscultation
46
What is the first heart sound (lub) associated with?
Closure of AV valves
47
What is the second heart sound (dub) associated with?
Closure of SL valves
48
What is an electromyogram?
2 electrodes placed about 2cm apart across a muscle e.g.biceps so that a burst of electrical activity can be recorded when the muscle is contracted
49
What is an electroencephalogram (EEG)?
Electrodes placed on skull potentials to record neuronal activity
50
What is an electroretinogram?
Electrodes placed on the eye to record electrical activity from light flashes
51
What is an electrocardiogram (ECG)?
A process whereby small potenials (approx. 1mv)are recorded between different locations on the skin that reflect the underlying activity of the heart
52
Who discovered the ECG and when?
William Einthoven and Augustus Waller
53
What does the P wave on an ECG correspond to?
Atrial depolarisation
54
What does the QRS complex on an ECG correspond to?
ventricular depolarisation
55
What does the T wave on an ECG correspond to?
Ventricular repolarisation
56
Why is atrial repolarisation not represented on an ECG trace?
Masked by QRS complex
57
How can heart rate be measured from an ECG?
58
How may a long QT interval in an ECG (long Q-T syndrome) be caused?
1. Inherited channelopathies in which mutations occur in myocardial Na+ and K+ channels 2. Side effects from seldane (non-sedating antihisthamine) which binds to K+ repolarisation channels
59
What does the width of the pressure volume loop represent?
60
What does the area within the pressure-volume loop represent?
Ventricular stroke work
61
What is aortic stenosis?
Impairment of left ventricular emptying because of high outflow resistance caused by a reduction in the valve orifice area when it opens
62
What are the effects of aortic stenosis?
- Increased pressure in ventricle - Increased cardiac afterload - Decreased stroke volume - Increased end systolic volume - Increased cardiac muscle mass - Increased risk of heart failure
63
What is the contractility of the heart dependent on?
Degree of stetch of the myocytes
64
What is the end diastolic volume (EDV)?
Amount of blood left at the end of cardiac filling
65
What is the end systolic volume (ESV)?
Amount of blood left in the heart at the end of ventricuar ejection
66
What is afterload equivalent to?
Peripheral resistance
67
What happens to cardiac output when afterload and heart rate are maintained at a constant level and pre-load is increased? What else is affected as a result of this?
Cardiac output increases - Left ventricular and aortic pressures increase - Increased EDV
68
What does Starling's law state?
The energy of contraction is a function of the length of the muscle fibre
69
Why is the cardiac response to increased afterload described as bi-phasic?
Initial decrease in CO (1-2 beats) Followed by increased/recovery of CO
70
What happens to CO when afterload is increased
Initial decrease in CO heart is pumping against increased resistance so less emptying of ventricles and increased ESV lead to decreased stroke volume and subsequent decrease in CO Then CO increases Afterload increases EDV which increases stretch and therefore increases CO (Starling)
71
What is the Anrep effect?
An autoregulation method in which myocardial contractility increases with afterload
72
According to the Anrep effect, how does sustained myocardial contracility increase CO?
- Activates tension dependent Na+/K+ exhangers bringing Na+ into the sarcolemma - Reduces Na+ gradient so sodium-calcium exhanger (NCX) stops working effectively - Ca2+ accumulates inside sarcolemma, taken up by SERCA pumps - CICR from SR by action potential - Increased force of contraction = increased SV = Increased CO to maintain perfusion
73
How is the heart innervated? What does this control?
Parasympathetic and sympathetic branches of the autonomic nervous system Rate and force of contraction
74
Where do the nerves supplying the heart originate?
Cardio-vascular centre of the medulla oblongata
75
What are the sympathetic nerves supplying the heart?
Cardiac accelerator nerves
76
Where do sympathetic nerves supplying the heart travel?
Cardiovascular centres in medulla oblongata ↓ Thorocic region of spinal cord ↓ SA node, AV node and most portions of the myocardium
77
What is released by sympathetic cardiac nerves? Where does this bind?
Noradrenaline β1 receptors on cardiac muscle fibres
78
What is the physiological effect of increased sympathetic innervation of the heart?
At SA node frequency of contaction increased (positive chronotropic effect) At contractile fibres in the ventricle, contraction increased (positive inotropic effect)
79
Which nerves control parasympathetic innervation of the heart?
Vagus nerves
80
What neurotransmitter is released by the vagus nerves?
Acetylcholine
81
Where does acetylcholine act in the heart?
Muscarinic receptors at the AV and SA nodes and at the atrial myocardium
82
What is the physiological effect of increased parasympathetic innervation of the heart?
Decreased heart rate (negative chronotropic effect) Little effect on contractility of the ventricles
83
How does adrenaline effect heart rate?
Acts on β1 receptors to increase frequency an force of contraction
84
What is the chronotropic effect?
Change in heart rate
85
What is the inotropic effect?
Force of contraction
86
What is the initial membrane potential of the SA node?
-60mV
87
What is the threshold value of nodal cells?
-40mV

HOM: cardiovascular physiology (7 decks)

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