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Physiology of Organisms > 12-14 > Flashcards

12-14 Flashcards

1
Q

What is an infarct?

A

condition characterised by formation of a dense wedge-shaped block of dead tissue in the heart muscle following an interruption to blood supply

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2
Q

what are the 5 stages leading to a heart attack?

A
  1. thrombus
  2. Ischaemia
  3. Hypoxia
  4. Necrosis
  5. Arrythmia
  6. Heart Attack
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3
Q

Advantages of a circulatory system?

x 4

A
  1. Organisms can be bigger
  2. Sustain higher metabolic rates
  3. Direct flow of metabolites between organs
  4. Blood flow regulate organ function
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4
Q

Disadvantages of circulatory systems

x 4

A
  1. Circulatory failure can be fatal
  2. High pressures and flow require control
  3. High pressures place stress on vessels
  4. Metabolically expensive
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5
Q

Functions of circulatory system

x 5

A
  1. overcome problem of moving chemicals long distances at reasonably high speed
  2. Removal of waste products
  3. Transport of hormones
  4. Immunity (transport white blood cells)
  5. thermoregulatory control
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6
Q

How does a regulatory system aid in thermoregulation?

A
  • rise in core body temp causes blood vessels close to skin to dilate and allow more heat loss
  • other way round so constrict in cold
  • however persistent lack of blood flow can cause blockage to blood flow and lead to frostbite and then tissue death
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7
Q

Two main types of circulatory systems=

A
  1. Open

2. Closed

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8
Q

Open circulatory systems

A
  1. heat pumps haemolymph through arteries that empty into haemocoel and then to vein to heart
    - no distinction between blood and tissue fluid
    - most invertebrates
    - limited ability to alter velocity and blood flow
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9
Q

Closed circulatory systems

A

Blood never leaves vessels and is separated from tissue fluid
- relatively high pressure

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10
Q

Independent evolution of closed circulatory systems

A

In fish = SINGLE circulation as blood flows through heart once per cycle through body
Amphibians, reptiles, birds and mammals have evolved double circulation so heart re-pressurises blood to pump round body after going through lungs (systemic and pulmonary circuit)

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11
Q

How many sections of the heart do fish have?

A

2

1 ventricle and 1 atrium

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12
Q

How many heart sections do amphibians have?

A

3
single atrium divided into two separate chambers
- oxygen rich into one and then oxygen poor into other
- however unlike mammals which have fully developed septum, there is slight mixing of blood
- compensate inefficiencies by absorbing oxygen though moist skin

  • reptiles developed more of septum so dont need to be moist
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13
Q

Vessels of mammalian circulatory system

A
  1. aorta from heart to body
  2. arteries then branch into arterioles
  3. then capillary bed
  4. venules
  5. veins
  6. Superior and inferior vena cava into right atria of heart
  7. pulmonary artery to lungs
  8. pulmonary vein back to heart before going through aorta again
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14
Q

What is the sac surrounding the heart?

A

The pericardial sac and the lower surface of this is attached to diaphragm so normal breathing actually rocks the heart

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15
Q

What is the annulus fibrosus?

A

The collagen ‘skeleton’ that holds the cardiac valves

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16
Q

Atrioventricular valves

A

thin flaps of tissue between atria and ventricles

  • right side is tricuspid and left is bicuspid (or mitral)
  • attached to papillary muscles by chordae tendinae = collagenous tendons
  • neither actually open or close valves, just prevent turning inside out
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17
Q

Semi-lunar valves

A

aortic and pulmonary

  • 3 leaflets
  • dont need connective tissue
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18
Q

Three layers of vessels

A
  1. Tunica adventitia
  2. Tunica media
  3. Tunica intima
    (1 furthest outside and 3 closest to blood)
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19
Q

Structure of tunica adventitia

A

collagenous extracellular matrix containing fibroblasts, blood vessels(to supply muscle) and nerves
- FUNCTION = add rigidity and form

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20
Q

Structure of Tunica media

A

smooth muscle cells organised concentrically with bands of elastic tissue

  • varies in thickness in different blood vessels according to function
  • thick in arteries as muscle and elastic tissue required to expand and recoil
  • thin in veins
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21
Q

Properties of Tunica intima

A

thin layer of endothelial cells = endothelium and also its connective tissue

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22
Q

Capillary structure

A
  • single layer of endothelial cells
  • nearly all cells within 10μm distance of capillary
  • main site of nutrient and gaseous exchange
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23
Q

Venule and vein structure

A

thin walls and media

  • valves to prevent blood flowing backwards
  • large cross-sectional area and so low resistance
  • hold 2/3 of blood
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24
Q

How does blood flow?

A

down pressure gradient created by the heart
by darcy’s law
Q = ΔP/R
where Q is flow

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25
Q

What is the perfusion pressure and what can it be equated to?

A

It is the difference between the pressure in the arteries that supply a region and the veins that drain it.

It can be equated to arterial blood pressure as venous pressure is negligible

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26
Q

What is blood flow equal to?

A

Perfusion pressure/Vascular resistance

= roughly equal to cardiac output

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27
Q

What is stroke volume?

A

The amount of blood pumped out of each ventricle per beat

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28
Q

What is blood pressure?

A

Cardiac output x vascular resistance

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29
Q

What is cardiac output equal to?

A

stroke volume x heart rate

so volume of blood pumped out of heart in a period of time

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30
Q

What should the flow in vessels be?

A

Laminar

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31
Q

What is laminar flow influenced by?

A

R is proportional to Lη/r^4

R is resistance
L is length of vessel
η is viscosity of blood
r is vessel radius

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32
Q

What is blood viscosity (η) determined by?

A

ratio of red blood cells to plasma - calculated by haematocrit = a percentage

  • can be influenced by altitude and anaemia and exercise
33
Q

What is flow proportional to?

A

Flow inversely proportional to resistance

So proportional to r^4

34
Q

What is vasomotion?

A

changed in vessel diameter

  • vasoconstriction
  • vasodilatation
35
Q

How do vasoconstrictor nerves work?

A

tonically active and impose a constant squeezing tone
tone can be increased further

  • can occur from sympathetic nerve and noradrenaline which acts for vasoconstriction
  • both arterioles and venules are innervated by sympathetic vasoconstrictor fibres but arterioles are more innervated than venules
36
Q

What is the effect when venules constricted?

A

faster return of blood to the heart - increased venous return

37
Q

What is the most efficient mechanism to dilate a blood vessel?

A

withdraw/inhibit sympathetic tone as this increases vessel radius

38
Q

what vasoactive properties does adrenaline have?

A

constricts some circulations and dilates others

  • e.g in most peripheral circulations, adrenaline may cause vasoconstriction to help maintain arterial blood pressure
  • but at skeletal muscle dilation
39
Q

what local factors does the endothelium aid with?

A

ACh stimulates endothelium to produce NO (nitric oxide) which causes vasodilatation

  • NO is not stored
    produced by cleavage of arginine by NO synthase
  • enzyme regulated by Ca2+-calmodulin so regulated by Ca2+

SHEAR STRESS also increases NO synthase

40
Q

How to measure blood pressure

A

Sphygmomanometer

  • inflatable cuff and pressure gauge
  • above 120mmHg and then stethoscope to listen (brachial artery)
  • slowly release air pressure
  • Korotkoff sounds higher end of pressure (systolic)
  • when disappear then diastolic pressure
41
Q

How to calculate mean arterial blood pressure (MAP)

A

Diastolic + 1/3*(Systolic-Diastolic)

42
Q

What is arterial stiffness?

A

A measure of rigidity of blood vessels

- more rigid with age, cardiovascular disease = more calcium and collagen

43
Q

What is the immediate affect of exercise?

A

exercise can be full body or of a single muscle

  • if just bicep for example
  • blood flow in resting skeletal muscle is low
  • muscle contracts it compresses vessel
  • can completely stop blood flow
  • between contractions flow is so greatly enhanced almost x 30 in some cases
  • the increase in blood flow is mainly by local metabolites
  • lag when stop in reduction in blood flow as the metabolites need to be cleared
44
Q

What are local metabolites?

- what is the feedback loop called?

A

chemicals produced when increase in oxygen consumption which cause vasodilatation which brings more oxygen and more metabolites

  • metabolic autoregulation
  • Lactic acid and adenosine
45
Q

How are diffusion distances changed during exercise?

A

at rest muscle capillaries have no flowing blood

  • pre-capillary sphincters are constricted and closed
  • increase in local perfusion pressure and blood flow opens these sphincters to open capillaries
  • recruitment of capillaries shorten diffusion distance
46
Q

What is systole?

A

Contraction

47
Q

What is diastole?

A

relaxation

48
Q

What is phase 1 of heart pump?

- atrial systole

A
  • last 20% blood into ventricles when atria contract
  • force AV valves open
  • The additional flow of blood = ATRIAL KICK/BOOST
  • small amount pushed back into vena cavae as no valves
49
Q

Phase 2 of cardiac cycle?

- isovolumetric contraction

A
  • ventricular contraction without change in ventricular volume
  • contraction begins as spiral bands of ventricular muscle contract and squeeze blood upwards
  • AV valves shut so not back to atria
  • all valves closed so pressure increase no significant volume change
50
Q

Phase 3 of cardiac cycle

- ventricular ejection

A
  • pressure in ventricles exceeds that of aorta forcing semi-lunar valves open
  • into arteries
51
Q

Phase 4 of cardiac cycle

- isovolumetric relaxation

A
  • ventricles begin to relax
  • rapid fall in ventricular pressure
  • in left ventricle the pressure below aorta and so blood flows back to close aortic valve
  • brief rise in arterial pressure = DICHROTIC NOTCH
52
Q

Phase 5 of cardiac cycle

- late diastole

A
  • both chambers relaxed

- ventricles begin to fill with blood passively before atrial systole (phase 1)

53
Q

What is a phonocardiogram?

A
  • PCG records sounds and murmers of heart through process of auscultation
  • use stethoscope to hear different sounds
  • three in lub-dup-dup or lub-lub-dup are cardiac gallops
54
Q

What do the sounds ‘lub-dub’ correlate to?

A 
lub = closure of AV valves
dub = semi lunar
55
Q

What is an ECG?

A
  • electrocardiogram
  • detect underlying activity of heart
  • has three main segments
  • P wave, QRS complex, T wave
56
Q

What is shown by the P-wave of an ECG?

A

atrial depolarisation

57
Q

QRS complex of ECG?

A

ventricular depolarisation

58
Q

T-Wave of ECG

A

ventricular repolarisation

59
Q

Importance of R-R interval

A
  • measure of heart rate

- is one cycle

60
Q

What does a long Q-T interval mean?

A

most of the time inherited channelopathies

  • mutations in myocardial Na+ and K+ channels
  • or as a side effect of drufs
61
Q

Cardiac pressure loop

- graph

A

A = mitral valve opens

A-B = blood flows passively in so increase in volume but not pressure
- last bit done by atrial systole

B = Mitral valve closes

B-C = isovolumetric contraction

C = point where ventricular pressure exceeds arterial pressure so semi-lunar valves open

C-D = ejection of blood

D = semi lunar valve closure

D-A = diastole so reduction in pressure but no change in pressure

62
Q

What is the ESV and EDV?

- difference?

A 
ESV = end systolic volume
EDV = end diastolic volume
  • difference is stroke volume (between point A and B
63
Q

What does the area of the pressure-volume loop mean?

A

the work done per cardiac cycle

64
Q

What is aortic stenosis

- GRΑPH

A
  • left ventricle emptying is impaired
  • due to high outflow resistance
  • reduction in the valve orifice area when opens
65
Q

What are the main contractile cells in the heart called?

A

Myocytes

  • electrically connected by junctions at the intercalated disks
  • form a syncytium
66
Q

What are pacemaker cells?

A

depolarise and contract spontaneously and regularly

  • responsible for initiating heart beat
  • in pacemaker regions
67
Q

Two main pacemaker regions of the heart

A
  1. SA = sino-atrial node

2. AV = atrio-ventricular node

68
Q

Sino-atrial node properties

A

highest intrinsic rate and so dominates

- if destroyed then AV takes over

69
Q

What are purkinje fibres and bundle of His

A
  • conducting fibres that run down septum
70
Q

Where do the autonomic nervous system nerves connected to the heart originate?

A

cardiovascular centre of medulla

71
Q

What is the root of the sympathetic fibres that affect the heart?

A
  • fibres from medulla to spinal cord

- thoracic region of spinal cord - cardjac accelerator nerves to SA and AV, also most portions of myocardium

72
Q

What do the cardiac accelerator nerves do?

A
  • sympathetic
  • release noradrenaline in nodes and myocardium
  • increases the slope of the pacemaker potential, reducing time between beats
  • contractile muscle fibres in ventricles increase force when innervated
73
Q

What is a chronotropic effect?

A

effects on the heart rate

  • positive means increase in heart rate
  • negative means decrease
74
Q

what are inotropic effects?

A

Effects on contraction force

- positive is an increase in force

75
Q

How do the parasympathetic nerves get to the heart?

A

Vagus nerve

  • release ACh which acts on muscarinic receptors at SA
  • negative chronotropic effect
  • almost no inotropic effect
76
Q

What are the two types of arterial baroreceptors?

A
  1. carotid baroreceptors
    - in carotid sinus at the bifurcation of internal and external carotid arteries
  2. aortic baroreceptors
    - arch of aorta
77
Q

Explain the carotid sinus and aortic reflex

A
  • carotid=maintain normal pressure in circulation perfusion of the brain
  • aortic = systemic blood pressure
  • both baroreceptors act tonically and so increase in stretch increase speed of AP and so indicate higher pressures
  • stimulates cardiac inhibitory centre and inhibition of cardiac acceleratory centre
  • reduction in heart rate and force of contraction
78
Q

how does a sudden fall in systemic arterial blood pressure due to haemorrhage affect nerves

A

loss of blood volume means decrease in frequency of baroreceptors—>but opposite to normal response

Physiology of Organisms (9 decks)

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