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human anatomy and physiology > cardiovascular system - haemodynamics > Flashcards

cardiovascular system - haemodynamics Flashcards

1
Q

what is haemodynamics

A

Study of how blood flows through the cardiovascular system

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2
Q

blood flow is determined by what

A

physical factors:

  • Blood pressure
  • Resistance to flow
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3
Q

what does resistance to blood flow depend on

A

Vessel length and radius

Blood viscosity

Arrangement of vessels

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4
Q

what is Hydrostatic pressure exerted by

A

blood on walls of vessel

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5
Q

what is resistance

A

opposition to blood flow, principally due to friction between blood vessel walls & blood.

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6
Q

Pressure measured within major artery system measures

A

Millimetres of mercury (mm Hg)

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7
Q

whats Systolic BP

A

Maximum BP during contraction of ventricles

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8
Q

whats Diastolic BP

A

Minimum BP just before next contraction

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9
Q

name a method for measuring blood pressure

A

sphygmomannometer

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10
Q

explain what happens in a Sphygmomanometer

A

Inflate cuff
- Occlude artery – no sound (as no blood flow)

Slowly deflate

Listen for Korotkoff sounds
- Spurting blood - sound = systolic (pressure to allow blood through narrow vessel; mmHg)
- Further deflate – feint sound = diastolic (mmHg)

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11
Q

what is our arterial pulse

A

heart rate

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12
Q

explain how we have an arterial pulse

A

Sudden ejection of blood into the aorta

then

Transmission through the arterial system

then

Rhythmic expansion of arterial wall

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13
Q

what is tachycardia

A

rapid resting pulse >100 beats/min (bpm)

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14
Q

what is Bradycardia

A

slow resting pulse <60 bpm

(e.g., endurance-trained athletes)

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15
Q

what is venous return

A

Blood returns from periphery to the heart

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16
Q

explain the respiratory pump in terms of venous control

A

Pressure changes in thorax & abdomen during respiration

Inspiration —->low pressure in thorax —> draws blood into RA

17
Q

explain the skeletal muscle pump in terms of venous control

A

Skeletal muscles contract in lower limbs

valves in veins contribute to return

18
Q

Important difference between pulmonary & systemic circulation is what

A

the autoregulatory response to O2

19
Q

explain the autoregulatory response to O2

A

Systemic circulation dilate if low O2

Pulmonary constrict!
- so bypass poorly functioning areas, to reach better ventilated areas of lung

20
Q

Substances enter & leave capillaries by:

A

Diffusion (down concentration gradient)
- O2, CO2, Glucose, Amino acids

Transcytosis (vesicles in endothelial cells, for large lipid insoluble)
- Insulin, antibodies from maternal-foetal circulation

Bulk flow (high pressure to low)
- filtration OUT of capillaries & reabsorption IN

21
Q

in capillary exchange, what are filtration and reabsorption promoted by

A

Filtration promoted by
- Blood hydrostatic pressure (heart)
- Interstitial fluid osmotic pressure

Reabsorption promoted by
- Blood colloidal osmotic pressure

22
Q

Whether fluid leaves or enters it depends on what

A

net balance of pressure

23
Q

explain Starling’s Law of Capillaries

A

volume of fluid & solutes reabsorbed = volume filtered

If filtration&raquo_space;> reabsorption = OEDEMA (=excessive accumulation of fluid, usually causing swelling)

24
Q

explain the fluid exchange across walls of capillaries

A

at arterial end:
- osmosis in
- blood pressure, and negative interstitial pressure out

venous end:
- osmosis in (1/10 vol to lymphatics so outside capillaries, 9/10 vol returns to capillaries)
- blood pressure and negative interstitial pressure

25
Q

what can be used if a vessel is obstructed

A

Can use a Stent
names after charles stent
to overcome problem coronary obstruction

26
Q

what can stents be used to do

A

open various ‘tubes’ within the body, with a balloon

27
Q

explain what Inferior Vena Cava Filters are for

A

To prevent clots travelling up to the heart and on to the lungs
- pulmonary embolism

Inserted by surgery, remaining for ~1 month

For patients who cannot be given conventional therapy e.g., anticoagulants

Note: are different to stents.

28
Q

when does a haemodynamic shock occur

A

when Failure of CV system to deliver enough O2 & nutrient to meet cellular metabolic needs

Cells switch from aerobic to anaerobic production of ATP
- lactic acid accumulates in body fluids

If shock persists, organs become damaged
- Death if untreated

29
Q

name the 4 types of haemodynamic shock

A

Hypovolumic
Cardiogenic
Vascular
Obstructive

30
Q

explain the Hypovolumic haemodynamic shock

A

decreased blood volume

  • inadequate intake of fluid
  • diabetes mellitus may cause much greater fluid loss in urine
  • sudden haemorrhage
  • excessive sweating
  • diarrhoea
  • vomiting
31
Q

explain the cardiogenic haemodynamic shock

A

due to poor heart function

- heart attack
- heart valve problems
32
Q

explain the vascular haemodynamic shock

A

due to inappropriate vasodilation - anaphylactic shock (histamine release causes vasodilation)

- head trauma
- septic shock (bacteria)
33
Q

explain the obstructive haemodynamic shock

A

due to obstruction of blood flow

- e.g., pulmonary embolism (clot)
34
Q

what happens if haemodynamic shock is mild

A

compensation by homeostatic mechanisms to prevent serious damage

35
Q

explain the homeostatic responses to shock

A
  1. Activation of renin-angiotensin-aldosterone system (vasoconstrict, absorb H2O) so increase blood volume thus Blood Pressure (BP)
  2. Secretion of ADH (leads to as above)
  3. Activation of sympathetic ANS (vascoconstrict skin, abdominal viscera, not brain or heart) so increase heart rate & secretion of E & norE by adrenal medulla)
    (E = Epinephrine = adrenalin; norE = norepinephrine = noradrenaline)
  4. Release of local vasodilators (in response to hypoxia) e.g., K+, H+, lactic acid, adenosine, NO (NO = nitric oxide)
36
Q

explain how to tell if shock is life threatening in terms of blood volume

A

If blood volume reduces >10-20%, shock life-threatening

37
Q

describe some signs and symptoms of shock

A

Some easily predicted by the homeostatic responses:

Rapid resting heart rate
Weak, rapid pulse
Altered mental state
Sweating
Thirst
Reduced urine formation
Nausea
Acidosis (blood pH)

human anatomy and physiology (52 decks)

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