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MEDSCI 142 > Section 3: Cardiovascular System > Flashcards

Section 3: Cardiovascular System Flashcards

1
Q

Human heart contains __ muscular pumps

A

2 muscular pumps, which each have a daily output of 7,000L of blood

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2
Q

Consequence of stoppage of heart’s muscular pumps

A

Unconsciousness in 10 seconds

Death in 4 minutes

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3
Q

Arteries vs veins

A

Arteries bring blood away from heart

Veins bring blood towards heart

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4
Q

Heart - circuits

A

Pulmonary circuit:
Only pumps to lungs
Medium resistance
Medium pressure

Systemic circuit:
Lots of systems involved
High resistance
High pressure

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5
Q

(Hepatic) portal veins

A

Veins don’t go straight back to heart

e.g. heptic portal vein - goes from gut to liver

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6
Q

Blood volume

A

9% pulmonary
7% pumps
84% systemic

Total 5L

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7
Q

Blood volume output

A

5L per minute for 1 pump

Can increase by 4 times if exercising, but trainable to up to 8x

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8
Q

Building a ventricular pump - phases

A

Filling phase:
Venous inlet on left side and arterial outlet on right
While ventricle is filling from venous end, an outlet valve is essential to prevent arterial blood from returning to the pump

Ejection phase:
Inlet valve necessary to prevent high-pressure blood in pumping chamber from returning to veins

Improvement #1:
An atrium is a reservoir upstream of the pump
During ejection phase, the atrium accumulates venous blood, which can enter the ventricle quickly during the filling phase

Improvement #2:
If inlet and outlet of pump are moved to lie close tgt, the walls of the pumping chamber can shorten in length and width
Adding an appendage = auricle also increases the capacity of the atrium

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9
Q

Auricle

A

An extension of the side of the atrium

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10
Q

Blood flow through heart - arrangements

A

Deoxygenated blood has a vertical arrangement

Oxygenated blood has a horizontal arrangement

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11
Q

Peak pressures (mmHg) - averages

A

Right atrium: 5 mmHg
Right ventricle: 27 mmHg
Left atrium: 8 mmHg
Left ventricle: 120 mmHg

Left higher as it must go through high resistance

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12
Q

Ventricular ejection - valves

A

Not actively opening valves - we’re actively preventing them from pushing too far

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13
Q

Ventricular inlet valves

A

AKA atrioventricular valves
Constructed from 2 or 3 flat flaps of fibrous CT
Free edge of each flap is tethered by tendinous cords - prevent it from bursting upwards into atrium during systole

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14
Q

Inlet valves

A 
Tricuspid valve (right)
Bicuspid/Mitral valve (left)
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15
Q

Left ventricle

A

Forms core of heart

Hollow cone with thick, muscular walls

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16
Q

Right ventricle

A

Sits on the side of left ventricle, much smaller

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17
Q

Open ends of ventricles are subdivided into…

A

An inlet and an outlet

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18
Q

Inlets and outlets - diameter

A

Inlets: large diameter to admit blood at low pressure
Outlets: small diameter because blood leaves ventricles at high pressure

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19
Q

Outlet valves

A 
Pulmonary valve (right)
Aortic valve (left)
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20
Q

Valves are essential for…

A

The operation of the pumps

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21
Q

Pathway taken by blood through ventricles

A

Approximately V-shaped

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22
Q

Ventricles in transverse section - peak pressure and wall thickness ratio

A

Peak pressure ratio (L:R) = 5:1

Wall thickness ratio (L:R) = 3:1 - main structural difference

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23
Q

Opening the pulmonary trunk

A

Shows three cusps of pulmonary valve

Shape = ‘semi-lunar’ - sometimes used to describe outlet valves

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24
Q

Outlet valves - number of cusps

A

Both outlet valves have three cusps, but unlike inlet valves, the cusps are each shaped like a pocket and lack cords
When inflated with blood, they gain strength from their 3D shape

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25
Q

Outlet valves - closed position

A

Ventricular filling
Pressure of blood trying to re-enter the ventricle forces the free edges of the cusps tightly together
Pressure in ventricle decreases
Pockets/cusps inflated

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26
Q

Where does the heart lie in our body

A

1/3 of mass of heart lies to right of mid-line of body and about 2/3 to the left

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27
Q

Apex of heart

A

Points inferiorly, anteriorly and to the left

So, heart is slightly rotated

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28
Q

Right border of heart

A

Formed mainly by right atrium

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29
Q

Inferior border of heart

A

Formed mainly by right ventricle

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30
Q

Left border of heart

A

Formed mainly by left ventricle (and in part, the left atrium/auricle)

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31
Q

Superior border of heart

A

Blood vessels = base

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32
Q

The heart is enclosed in a…

A

Double-walled bag

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33
Q

Pericardium - inner and outer walls is made of what?

A

Both inner and outer pericardium are made of a single layer of squamous mesothelial cells
Walls are continuous where the great vessels enter and leave the heart

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34
Q

Pericardium - inner and outer wall - where

A 
Inner wall (visceral pericardium) adheres to heart and forms heart's outer surface (epicardium)
Outer wall (parietal pericardium) lines the fibrous pericardium
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35
Q

Fibrous pericardium

A

A tough fibrous sac
Outermost layer
Composed of collagen - doesn’t like to stretch

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36
Q

Parietal and visceral pericardium are made of…

A

Serous membrane

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37
Q

Pericardial space

A

Space between the visceral and parietal layers
Contains serous fluid, secreted by serous membrane
Allows parietal and visceral surfaces to slide without friction as the heart beats

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38
Q

What is ‘inside’ the pericardial space

A

Heart is NOT inside the pericardial space - excluded by visceral pericardium
Only pericardial fluid is inside the pericardial space

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39
Q

Fat

A

Good electrical insulator between atria and ventricles

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40
Q

Inlets and outlets - plane

A

Inlets and outlets on same plane with each other

Attach to fibrous skeleton - doesn’t allow inlet and outlet to stretch

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41
Q

Fibrous skeleton of heart

A

Fibres forming tricuspid ring are incomplete
Pulmonary ring is absent
Fatty CT present in areas where fibrous skeleton is incomplete

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42
Q

Sinoatrial (SA) node

A

Can depolarise and repolarise themselves (autonomic)
Pacemaker - determines heart rate
Influenced by hormones and nerve impulses

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43
Q

Atrioventricular (AV) node

A

Can depolarise and repolarise themselves, but not as fast as SA node

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44
Q

Purkinje fibres

A

Made of purkinje cells, which conduct APs very quickly and aren’t branched

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45
Q

Conduction system of heart: SA node –> Atrial muscle - speed and result

A

Speed - slow

Result - atrial contraction

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46
Q

Conduction system of heart: Atrioventricular node - speed and result

A

Speed - very slow

Result - 100ms delay in AP getting to ventricles

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47
Q

Conduction system of heart: AV bundle –> Purkinje fibres - speed and result

A

Speed - fast

Result - complete and even ventricular contraction, known as systole

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48
Q

The cardiac cycle

A

Ventricular filling:
Commences as pressure in ventricle drops below that of atrium
Mitral valve opens quietly and blood enters ventricle
Ventricle fills to ~80% of its capacity

Atrial contraction:
Left atrium contracts to complete filling of ventricle
Rise in atrial pressure is small for 2 reasons;
- atrial muscle layer is thin
- no valves where pulmonary veins enter atrium (so nothing to prevent backflow into veins)

Isovolumetric ventricular contraction (systole):
~0.05s
Ventricle starts to contract
Blood within it lifts backwards towards atrium and mitral valve closes (first heart sound)
Ventricular pressure still below aorta’s so aortic valve remains closed
Atrial P < ventral P (increasing) < arterial P
Ventricle is isolated from rest of circulation (inlet and outlet closed)

Ventricular ejection:
Systole continues, but ventricular pressure now exceeds aortic pressure and aortic valve cusps open quietly
Blood leaves ventricle
Since blood is ejected into aorta faster than it can run-off into distributing arteries, the pressure in ventricle and aorta continues to rise steeply
Later in this phase, rate of ejection falls below rate of run-off and aortic and ventricular pressures level-off, then decrease

Isovolumetric ventricular relaxation:
As ventricle relaxes, ventricular pressure drops suddenly, flow reverses in aorta and aortic valve closes (second heart sound) as blood tries to re-enter ventricle
Mitral valve is closed because ventricular pressure still exceeds atrial pressure
Atrial P < ventral P (increasing) < arterial P
Ventricle is isolated from rest of circulation (inlet and outlet closed)
Once ventricular pressure drops below pressure in atrium, cycle repeats

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49
Q

Heart sounds

A

First heart sound: lub

Second heart sound: dub

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50
Q

Do we need atria to survive

A

No, we don’t need atria for the last 20% filling

Can fill up some without it

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51
Q

Classes of blood vessels

A 
Elastic artery
Muscular artery
Arteriole
Capillary
Venule (collecting part)
Vein (collecting part)
Coronary arteries
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52
Q

Blood vessels: Elastic artery - structure and function

A

Structure: Many thin sheets of elastin in middle tunic, quite big - can fit finger inside

Function:
During systole - expand to store blood leaving ventricle
During diastole - push blood out into arterial tree by elastic recoil
Smooth the pulsatile flow of blood leaving ventricles

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53
Q

Transition between elastic and muscular artery

A

Gradual

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54
Q

Blood vessels: Muscular artery - structure and function

A

Structure: many layers of circular smooth muscle wrapped around vessel in middle tunic, varies in size from pencil to pin
Function: distribute blood around body at high pressure and lungs at medium pressure
Rate of blood flow is adjusted by using smooth muscle to vary radius of vessel
Controls bulk flow of blood - go where needed

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55
Q

Blood vessels: Muscular artery - flow rate

A

Flow is proportional to fourth power of radius (Poiseuille’s law)
Small change in radius has a large effect on flow rate

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56
Q

Blood vessels: Muscular artery - parts

A 
Inner tunic (tunica interna/intima)
Middle tunic with smooth muscle (tunica media)
Outer tunic (tunica externa/adventitia)
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57
Q

Blood vessels: Arteriole - structure and function

A

Structure: 1-3 layers of circular smooth muscle wrapped around vessel in middle tunic
Have a thicker muscular wall relative to their size than other blood vessels

Function: control blood flow into capillary beds
Where greatest pressure drop occurs and where there is greatest resistance to flow

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58
Q

Blood vessels: Degree of constriction of arterioles throughout body determines…

A

Total peripheral resistance, which in turn affects;
Mean arterial blood pressure - the more arterioles open, the more the heart has to pump blood into the big vessel to keep pressure up

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59
Q

Which blood vessels are endothelial cells found in

A

All blood vessels

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60
Q

Which blood vessels are the tunica interna found in

A

All blood vessels

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61
Q

Blood vessels: Capillary - structure and function

A

Structure: diameter just wide enough to admit one RBC
Wall is a single layer of endothelium with an external BM
No smooth muscle in wall and no CT –> can’t adjust diameter

Function: tiny vessels which are thin-walled to allow exchange of gases, nutrients and wastes between blood and surrounding tissue fluid
Blood flow is slow to allow time for exchange to occur
Leaky - plasma escapes, but most is immediately recovered due to osmosis

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62
Q

Blood vessels: Venule - structure and function

A

Structure: small venules have endothelium plus a little CT
Larger ones have a single layer of smooth muscle
Vary in size

Function: low-pressure vessels which drain capillary bed
During infection and inflammation, venules are the site where WBCs leave the blood circulation to attack bacteria
Very slow flow

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63
Q

Blood vessels: Vein - structure and function

A 
Structure: similar to a muscular artery but much thinner-walled for their size (less muscle and CT)
Larger veins (especially in legs) have valves which prevent backflow

Function: thin-walled, low-pressure, high V vessels which drain blood back to atria (except portal veins)
Walls are thin and soft –> stretch easily
Small change in venous BP causes large change in venous V
Act as a blood reservoir

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64
Q

Coronary arteries - location

A

Arise from the aorta just downstream from aortic valve

Underneath fibrous pericardium

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65
Q

What do coronary arteries supply

A

Muscles of the heart (myocardium), which is what makes them important

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66
Q

Reduction of coronary artery size

A

If narrows to ~20% its normal X-section by atheroma, significant obstruction to blood flow occurs
During exercise, the myocardium supplied by the diseased artery runs low on oxygen (ischemia) causing chest pain (angina) - may result in death of a local area of myocardium

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67
Q

Deoxygenated blood is drained from the ___ by ____

A

Myocardium

Cardiac veins, which return the blood to the right atrium

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68
Q

What function does the heart serve?

A

Demand –> Supply
Oxygen use –> Oxygen demand
More in –> More out

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69
Q

Cardiac output (CO) = ?

A

heart rate (HR) x stroke volume (SV)

At rest CO is between 4-7 litres / min

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70
Q

What is stroke volume (SV)

A

The volume of blood ejected by the left ventricle for 1 cardiac cycle

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71
Q

What is venous return

A

The volume of blood returning to the heart from the vasculature every min and is linked to CO

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72
Q

What is cardiac output (CO)

A

The volume of blood ejected into the aorta (or ejected from the left ventricle) per min (mL / min)

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73
Q

Cardiovascular system - flow

A

High flow

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74
Q

The more blood that returns to the heart during diastole…

A

The more blood is ejected during the next systole

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75
Q

Regulation of SV: Intrinsic regulation of force of contraction

A

Governed by degree of stretch of myocardial fibre at end of diastole

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76
Q

Regulation of SV: Extrinsic regulation

A

Determined by activity of ANS and circulating levels of various hormones

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77
Q

Starling’s Law

A

The energy of contraction of the ventricle is a function of the initial length of the muscle fibres comprising its walls
i.e. a greater force of contraction can occur if the heart muscle is stretched first

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78
Q

SV and diastole

A

As blood returns to the heart in diastole, it begins to fill the ventricle –> pressure rises –> stretches myocardial fibres, placing them under a degree of tension (preload)

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79
Q

What 3 factors regulate SV

A

Preload on heart (mmHg) - stretch on left ventricle before it contracts
- increased V –> increased pressure –> increased preload –> increased SV –> increased force of contraction

Contractility - ability of nervous system to increase contractility

Afterload (mmHg) - the pressure the heart has to work at to eject left ventricle, through aortic valve, into aortic arch (work heart must do) to pump blood out
- refers to arterial pressure in left ventricle

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80
Q

What is inotrophy

A

Force of a contraction / contractility

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81
Q

Ejection fraction

A

SV/EDV
60-70%
i.e. 60-70% of blood that comes into left ventricle is pumped out per cardiac cycle
<25% = heart failure

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82
Q

Pressure-volume curve

A

Shows the work performed by the heart each time it beats

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83
Q

Contractility - intropic agent

A

The SV increase when a +ve inotropic agent is present
These agents often promote Ca2+ inflow during cardiac AP, which strengthens the force of the subsequent muscle fibre contraction

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84
Q

Contraction of left ventricle requires…

A

Co-ordination (electrical activity)

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85
Q

Positive inotropic agents

A

A slight increase in Ca2+ plasma promotes Ca2+ inflow in AP –> increased inotrophy
K+ slows heart rate
Na+, K+ and Ca2+ highly regulated

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86
Q

Causes of heart failure

A

Ejection fraction decrease:
High blood pressure
Viruses
Coronary artery disease

Responds by increasing heart rate

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87
Q

What is the rhythmic pulsation of heart maintained by

A

Excitatory signals generated within the heart

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88
Q

Heart electrical activity

A

1.5 mV

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89
Q

Intrinsic HR

A

90-100 bpm (higher than resting)
Generated by pacemaker cells (e.g. SA node) which self-discharge
Causes ventricular myocytes to contract

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90
Q

What does an ECG measure

A

Sum of all electrical activity spreading over heart walls

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91
Q

Why does heart require electrical activity

A

To get to the right myocytes at the right time to allow them to contract

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92
Q

Which part of the heart is the last to contract

A

Apex of heart (base)

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93
Q

If measuring electrical activity in myocyte, you are measuring the…

A

Cardiac AP

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94
Q

Steps in cardiac muscle contraction (basic)

A

Depolarisation
Plateau
Repolarisation

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95
Q

Steps in cardiac muscle contraction (detail)

A

Excitation is initiated by specialised cells in SA node which lies close to right atrium
A wave of depolarisation is conducted throughout the myocardium
MP between successive APs show a progressive depolarisation - this is the pacemaker
When threshold is reached, an AP is triggered

Myocytes of atria, ventricle and conducting system have APs with a fast initial depolarisation followed by a pleateau phase prior to repolarisation
Since muscle is refractory during and shortly after the passage of an AP, the long plateau phase ensures unidirectional excitation of myocardium

Repolarisation of myocardial cells occur when V-gated Ca2+ channels inactivate and additional V-gated K+ channels open

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96
Q

SA node - resting potential

A

Cells of SA node have an unstable resting potential

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97
Q

Cardiac muscle contraction - Ca2+

A

Responsible for plateau phase (inward movement of Ca2+, as well as some K+ channels opening)
- ensures the AP lasts almost as long as the contraction

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98
Q

Electrocardiogram (ECG)

A 
P wave = atrial depolarisation (atrial contraction)
QRS complex (R wave) = onset of ventricular depolarisation (ventricular contraction)
T wave = ventricular repolarisation
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99
Q

ECG - ‘leads’

A

12 leads give diff views of atria and ventricles (L and R)

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100
Q

Fibrilation

A

If atria stops working –> atria fibrilation –> can still function / walk around
Ventricular fibrilation –> heart attack –> must reset / use defibrillator

101
Q

ECG - steps

A
  1. Depolarisation of atrial contractile fibres produce P wave
  2. Atrial systole (contraction)
  3. Depolarisation of ventricular contractile fibres produce QRS complex
  4. Ventricular systole (contraction)
  5. Repolarisation of ventricular contractile fibres produce T wave
  6. Ventricular diastole (relaxation)
102
Q

Autonomic Nervous System (ANS)

A

A branch of the CNS

Involves brainstem - helps regulate cardiovascular system

103
Q

Components of ANS

A 
Parasympathetic:
Increased parasympathetic --> decreased HR
Quick acting
Neurotransmitter ACh
e.g. vagus nerve - slows HR
Sympathetic:
Increased sympathetic --> increased HR
Increased sympathetic --> increased SV (also increased by parasympathetic but v little)
Slower acting (5-10s to change HR)
Neurotransmitter NE
104
Q

ANS - goes to…

A

Every arteriole in the body

105
Q

What is the apex formed by

A

The tip of the left ventricle and rests on the diaphragm

106
Q

Layers of the heart wall

A

Epicardium (external)
Myocardium (middle)
Endocardium (inner)

107
Q

Layers of heart wall - myocardium

A

Responsible for pumping action of heart
Composed of cardiac muscle tissue
Makes up approx 95% of heart wall

108
Q

Layers of heart wall - endocardium

A

A thin layer of endothelium overlying a thin layer of CT
Provides a smooth lining for chambers of heart
Continuous with endothelial lining of large blood vessels attached to heart

109
Q

Coronary sulcus

A

Encircles most of the heart

Marks the external boundary betwen the superior atria and inferior ventricles

110
Q

Anterior interventricular sulcus

A

A shallow groove on the anterior surface of the heart that marks the external boundary between the right and left ventricles
Continuous with posterior interventricular sulfucs

111
Q

Which veins does the right atrium receive blood from

A

Superior vena cava, inferior vena cava and coronary sinus

112
Q

Right atrium - anterior and posterior walls

A

Very different
Inside of posterior wall is smooth
Inside of anterior wall is rought due to presence of muscular ridges

113
Q

Valves of the heart are composed of…

A

Dense CT covered by endocardium

114
Q

Chordae tendineae

A

Tendon-like cords connected to cusps of the inlet valves

115
Q

Pathway of blood from right ventricle

A

Blood passes from right ventricle through the pulmonary valve into pulmonary trunk, which divides into right and left pulmonary arteries and carries blood to the lungs

116
Q

How many veins does the left atrium receive blood from

A

4

117
Q

Blood passes from the left atrium into the left ventricle through the…

A

Bicuspid (mitral) valve

118
Q

How are the systemic and pulmonary circuits arranged

A

Arranged in series; output of one becomes the input of the other

119
Q

What blood do venules carry

A

Venules carry deoxygenated blood away from tissues and merge to form larger systemic veins

120
Q

What does blood pressure measure

A

Pressure in arteries (arterial pressure, i.e. pulsatile pressure)

121
Q

BP = ?

A

BP = CO x TPR (total peripheral resistance) = MAP

122
Q

High levels of BP for long periods of time can cause…

A

Weakness in blood vessels –> may burst or become occluded –> coronary or stroke

123
Q

What does BP drive

A

Exchange

124
Q

Where does exchange occur

A

Capillaries

The rest is just transport

125
Q

What is the driving force pushing blood through

A

Pressure

126
Q

Arterioles provide lots of…

A

Resistance
Are small vessels with lots of smooth muscle –> have a degree of tension/tone –> provides a shock absorption –> decreased pulsatility

127
Q

Does pressure increase or decrease in capillaries

A

Pressure continues to decrease in capillaries (was initially decreasing in arterioles) because we’re taking fluid out

128
Q

Venous pressure - level

A

Low

129
Q

Cardiovascular system - flow and pressure

A

Flow rate is same even though pressure changing

5L in and 5L out

130
Q

Capillary exchange - in and out?

A

At one end of capillary bed, we’re squeezing fluid out, but at other end we’re absorbing it back in
i.e. high V out and high V in

131
Q

Capillary exchange - lymphatic system

A

A certain amount of fluid passes out from capillaries into lymphatic system and is transported away

132
Q

Capillary exchange - BHP

A

Blood hydrostatic pressure

The driving force for exchange in arterial end of capillaries

133
Q

Capillary exchange - IFHP

A

Interstitial fluid hydrostatic pressure
Opposing pressure of interstitial fluid
Close to zero

134
Q

Capillary exchange - BCOP

A

Blood colloid osmotic pressure
Have proteins dissolved in plasma all the time but aren’t pushed out of capillaries –> act as a restraint for fluid going out - opposes BHP

135
Q

Capillary exchange - IFOP

A

Interstitial fluid osmotic pressure
Some proteins dissolve in interstitial fluid that isn’t reabsorbed back into capillaries
Normally very small

136
Q

Capillary exchange - NFP

A

Net filtration pressure

137
Q

Edema

A

Where you are pushing out more fluid than you are reabsorbing
Interstitial spaces between cells have lots of fluid in there
Net filtration increases –> extrudes more fluid out of plasma
Tissue in legs and limbs get swollen

138
Q

Arterioles - constriction?

A

Change in radius = big effect on resistance

Blood flow decrease = vasoconstriction

139
Q

Renal blood flow

A

Renal blood flow can go from 1L/min to 50mL/min

140
Q

What happens if pressure decreases

A

No longer drives exchange

141
Q

What happens to blood vessels when you’re hot

A

Vasodilation (regulates temp)

142
Q

How is the cardiovascular system arranged

A

Anatomically arranged in parallel (not series) –> all receive same amount of pressure

143
Q

Cardiovascular system - arterioles in diff organs

A

Constriction of arterioles in diff organs helps redistribute blood flow to other organs

144
Q

Blood pressure - main points

A

Exchange

Stability

145
Q

General pathway for inputs and outputs

A

Input –> CNS (particularly ANS) –> Output

146
Q

Why don’t you faint when you stand up

A

Input: senses BP using arterial baroreceptors –>
CNS/ANS –>
Output:
- decrease in parasympathetic NS –> increase HR
- increase in sympathetic NS –> increase HR and SV
–>
Increased CO

BP = CO x TPR
Both CO and TPR increase –> increase BP

147
Q

Arterial baroreceptors

A

Y-shaped
Have afferent nerves entering which are stretch sensitive (stretch every heartbeat)
Increased BP activates more

Baroreceptors also found in aortic arch

148
Q

Arterioles and sympathetic nerves

A

Arterioles have sympathetic nerves branching throughout the muscle
Sympathetic nerves have varicosities that release NE –> vasoconstriction

149
Q

CNS: types of outputs

A

Neural and hormonal

150
Q

CNS: Output - angiotensin II

A

Important hormone for vasoconstriction
Ace inhibitor if you have high BP –> decrease angiotensin II –> vasodilation
Related to renin (produced in kidneys)

151
Q

Inputs to CNS

A

Multiple inputs which give rise to an output

152
Q

Vasoconstriction/dilation of organs

A

Vessels in some organs will vasoconstrict and other vessels in other organs will vasodilate
i.e. tailored response

153
Q

Cardiopulmonary receptors

A

Receptors found in major veins around the heart (especially SVC)
Respond to stretch of veins

154
Q

Cardiopulmonary receptors - drinking fluid process

A

Drinking fluid increases venous pressure –> receptor is stretched and fires off –>
CNS –decreases renal SNS activity–>
Kidney:
- increase renal blood flow
- increase filtration
- increase urine flow rate
–>
Venous pressure returns to normal (homeostasis)
Slow / long-term process compared to arterial baroreceptors

155
Q

CNS: Drinking fluid - hormonal response

A

Also slow activity
Antidiuretic hormone (ADH) decreases urine production
Decreased ADH –> allows you to excrete urine more

156
Q

Stable BP is important for…

A

Exchange

157
Q

When you almost get into an accident, you have elevated HR for a while (longer lasting) - why?

A

Increased sympathetic NS
CNS triggers adrenal gland via SNS
- secretes NE into bloodstream –> acts on α-receptor –> vasoconstriction –> increased HR and SV

158
Q

Blood vessels: Tunica interna/intima

A

Forms inner lining of blood vessel
In direct contact with blood as it flows through the lumen
Contributes minimally to thickness

159
Q

Blood vessels: Tunica media

A

Muscular and CT layer
Greatest variation among diff vessel types
In most vessels, relatively thick
Substantial amounts of elastic fibres

160
Q

Blood vessels: What separates the tunica media from the tunica externa?

A

External elastic lamina

161
Q

Blood vessels: Tunica externa

A

Consists of elastic and collagen fibres
Contains numerous nerves and tiny blood vessels
Helps anchor vessels to surrounding tissues

162
Q

Elastic arteries - elastic lamellae

A

The thick tunica media, dominated by elastic fibres

163
Q

Examples of elastic arteries

A

Aorta and pulmonary trunk

164
Q

Elastic arteries - important function

A

Help propel blood onward while ventricles are relaxing

165
Q

Elastic arteries AKA…

A

Conducting arteries

166
Q

Muscular arteries are also called…

A

Distributing arteries - continue to branch and ultimately distribute blood to each of the various organs

167
Q

Arterioles - metarteriole

A

Terminal end of arteriole

Tapers toward the capillary junction

168
Q

Capillary bed

A

A network of 10-100 capillaries that arise from a single metarteriole

169
Q

Cardiac conduction system

A

A network of specialised cardiac muscle fibres that provide a path for each cycle of cardiac excitation to progress through the heart

170
Q

Where is the only site where APs can electrically conduct from atria to ventricles?

A

Atrioventricular (AV) bundle

171
Q

Nervous system regulation of the heart originates in…

A

The cardiovascular centre in the medulla

172
Q

Capillary exchange

A

The movement of substances between blood and interstitial fluid

173
Q

3 basic mechanisms by which substances enter and leave capillaries

A

Diffusion
Transcytosis
Bulk flow

174
Q

Bulk flow

A

A passive process where large numbers of ions, molecules, or particles in a fluid move tgt in the same direction
Move at faster rates than with diffusion alone

175
Q

What is bulk flow more important for

A

Regulation of relative volumes of blood and interstitial fluid

176
Q

Filtration vs reabsorption

A

Filtration: pressure-driven movement of fluid and solutes from blood capillaries into interstitial fluid
Reabsorption: pressure-driven movement from interstitial fluid into blood capillaries

177
Q

What does net filtration pressure (NFP) determine

A

Whether volumes of blood and interstitial fluid remain steady or change

178
Q

Within vessels, what is hydrostatic pressure due to

A

Pressure that water in blood plasma exerts against blood vessel walls

179
Q

NFP (net filtration pressure) = ?

A

(BHP + IFOP) - (BCOP + IFHP)

i.e. pressures that promote filtration minus pressures that promote reabsorption

If +ve = net outward pressure (filtration)
If -ve = net inward pressure (reabsorption)

180
Q

Systolic BP vs diastolic BP

A

Systolic: highest pressure attained in arteries during systole
Diastolic: lowest arterial pressure during diastole

181
Q

Mean arterial pressure (MAP) is roughly…

A

1/3 of the way between diastolic and systolic pressures

182
Q

Another way of calculating cardiac output = ?

A

CO = MAP / R

183
Q

Vascular resistasnce depends on…

A

Size of lumen
Blood viscosity
Total blood vessel length

184
Q

Total peripheral resistance

A

Refers to all vascular resistances offered by systemic blood vessels

185
Q

Circulation time

A

The time required for a drop of blood to pass from the right atrium, through the pulmonary circulation, back to the left atrium, through the systemic circulation down to the foot, and back again to the right atrium

In a resting person, usually ~1 min

186
Q

Proprioceptors

A

Monitor movements of joints and muscles and provide input to cardiovascular centre during physical activity

187
Q

Baroreceptors

A

Monitor changes in blood pressure and stretch in walls of blood vessels

188
Q

Chemoreceptors

A

Monitor conc of various chemicals in blood

189
Q

Baroreceptors - when BP falls…

A

Baroreceptors are stretched less –> send nerve impulses at slower rate to cardiovascular centre, which decreases parasympathetic stimulation of heart and increases sympathetic stimulation

190
Q

Where is the bicuspid valve located

A

Between the left atrium and the left ventricle

191
Q

Where does deoxygenated blood returning from the systemic circulation flow into

A

Right atrium

192
Q

Blood flows from the pulmonary veins into the..

A

Left atrium

193
Q

The outlet valves lack chordae tendinae because…

A

When the valves close, the cusps remain stable because of their cup shape

194
Q

Where the great arteries and veins attach at the base of the human heart, the aorta is…

A

Posterior to the pulmonary trunk

195
Q

There is a semilunar valve between the..

A

Right ventricle and the pulmonary trunk

196
Q

Does the left ventricle expel a greater volume of blood per beat than the right ventricle

A

No

197
Q

When do the atrioventricular valves close

A

The ventricles contract

198
Q

Where does blood flow into the coronary arteries from

A

The ascending aorta

199
Q

What component of the conduction system provides the only electrical connection between the atria and the ventricles

A

AV bundle

200
Q

A decrease in arterial blood pressure would most likely and immediately lead to…

A

Decreased afterload

201
Q

Blood flow to muscles increase if _______ in arterioles supplying the muscles increase

A

Vasodilation

202
Q

An increase in cardiac sympathetic activity would most likely and immediately…

A

Increase SV

203
Q

Increased stimulation of the heart by cardiac accelerator nerves causes…

A

Stimulation by NE of the SA node and of the beta receptors on the cardiac muscle fibres of the ventricles

204
Q

Where does blood flow most slowly through

A

Capillaries because their total cross-sectional area is the largest

205
Q

In terms of the structural organisation of the cardiovascular system, what factor contributes most to BP

A

The parallel arrangement of the vascular beds

206
Q

Stimulation of the heart by autonomic nerves fibres traveling with the vagus nerve causes…

A

Decreased HR but no change in ventricular contractility

207
Q

What happens if heart rate increases to very high levels

A

End-diastolic volume drops because ventricular filling time is so short

208
Q

Moderator band is part of..

A

The heart’s conduction system

209
Q

With regard to resistance, the parameter with the largest effect is…

A

Radius / diameter

210
Q

If plasma proteins are lost due to kidney disease, which of the following pressure changes occur as a direct result

A

Blood colloid osmotic pressure (BCOP) decreases

211
Q

The vasomotor region of the cardiovascular centre directly controls…

A

Peripheral resistance by changing diameter of blood vessels

212
Q

Where are baroreceptors located

A

In the walls of the aorta (aortic arch) and carotid arteries/sinus

213
Q

End-systolic volume

A

The amount of blood remaining in the ventricle when the semilunar valve closes

214
Q

What is angina pectoris

A

The pain accompanying myocardial ischemia

215
Q

Pons - grey or white matter?

A

Both

216
Q

Fibrous skeleton - function

A

Insulates the ventricular myocardium from electrical activity of the atria, so wave of electrical activation can only propagate between the 2 chambers via the AV node - prevents simultaneous contraction of atria and ventricles
Vital for coordination of mechanical contraction and thus ejection of blood

217
Q

Mitral regurgitation

A

Blood regurgitation from LV into LA during ventricular systole due to failure of valves to close properly
As soon as pressure in ventricle exceeds that of the atria (isovolumetric ventricular contraction), regurgitation may occur

218
Q

When does atrial diastole first occur

A

During isovolumetric ventricular contraction

219
Q

Longest phase in cardiac cycle

A

Ventricular filling

~0.4s

220
Q

What is the valve immediately upstream of the coronary arteries

A

Aortic semi-lunar valve

221
Q

Cardiac reserve

A

The difference between the rate at which the heart pumps blood and its max capacity for pumping blood at any given time

222
Q

Hypothermia ____ HR

A

Decreases

223
Q

Hypertension

A

Abnormal higher BP

224
Q

Bradycardia

A

Abnormally slow HR

225
Q

Tachycardia

A

Abnormally rapid HR

226
Q

Poiseuille’s law

A

States the velocity of a liquid flowing through a capillary is directly proportional to the pressure of the liquid and the fourth power of the radius of the capillary

227
Q

Hemorrhage

A

Blood loss

228
Q

Chronotropy

A

Heart rate

i.e. +ve chronotropic effect = increased HR

229
Q

Starling’s Law of the Capillaries

A

States that the V of fluid reabsorbed at the venous end of a capillary is nearly equal to the V of fluid filtered out at the arterial end

230
Q

Arterioles - nerves

A

Only contain sympathetic nerves (so there is a constant degree of tension)
Doesn’t contain parasympathetic nerves

231
Q

Chordae tendineae when valves are open

A

Chords are relaxed and closer to the middle of the lumen of the ventricle

232
Q

For no ventricular filling to occur…

A

Ventricular P must be higher than peak atrial pressures to keep inlet valves closed

233
Q

Upstream vs downstream

A 
Upstream = closer to heart
Downstream = further from heart
234
Q

Afterload and BP

A

Increased afterload = increased BP = hypertension

235
Q

Decreased BP and baroreceptors

A

Decreased BP –> baroreceptors fire less and upregulate sympathetic nervous activity

236
Q

Why is resting HR slower than intrinsic HR

A

Due to activity of parasympathetic NS

237
Q

Most anterior structure at base of heart

A

Pulmonary trunk

238
Q

Fibrous skeleton is made of…

A

CT

239
Q

Pulmonary veins drain into the…

A

LA –> LV

240
Q

Atria contract when initially stimulated by…

A

SA node

241
Q

Initiation of heartbeat is the responsibility of…

A

SA node

242
Q

Increase in venous return results in…

A

Increased end-diastolic volume –> increased preload

243
Q

Alpha vs beta receptors

A

Alpha receptors affect skin

Beta receptors affect cardiac muscle

244
Q

Vasomotor nerves

A

Activated by sympathetic activity –> vasoconstriction –> increased resistance

245
Q

Arteries and veins - pressure

A 
Arteries = high pressure
Veins = low pressure
246
Q

Standing still for long periods of time

A

Lack of skeletal muscle pumping of veins –> venous return decreases –> SV decreases –> CO decreases

247
Q

What happens during diastole

A

Relaxes and fills with blood

248
Q

End-systolic volume

A

The amount of blood remaining in the ventricle when the semi-lunar valve closes

MEDSCI 142 (9 decks)

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