cardiovascular system - haemodynamics

Question 1

what is haemodynamics

Answer 1

Study of how blood flows through the cardiovascular system

Question 2

blood flow is determined by what

Answer 2

physical factors:

• Blood pressure
• Resistance to flow

Question 3

what does resistance to blood flow depend on

Answer 3

Vessel length and radius

Blood viscosity

Arrangement of vessels

Question 4

what is Hydrostatic pressure exerted by

Answer 4

blood on walls of vessel

Question 5

what is resistance

Answer 5

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

Question 6

Pressure measured within major artery system measures

Answer 6

Millimetres of mercury (mm Hg)

Question 7

whats Systolic BP

Answer 7

Maximum BP during contraction of ventricles

Question 8

whats Diastolic BP

Answer 8

Minimum BP just before next contraction

Question 9

name a method for measuring blood pressure

Answer 9

sphygmomannometer

Question 10

explain what happens in a Sphygmomanometer

Answer 10

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)

Question 11

what is our arterial pulse

Answer 11

heart rate

Question 12

explain how we have an arterial pulse

Answer 12

Sudden ejection of blood into the aorta

then

Transmission through the arterial system

then

Rhythmic expansion of arterial wall

Question 13

what is tachycardia

Answer 13

rapid resting pulse >100 beats/min (bpm)

Question 14

what is Bradycardia

Answer 14

slow resting pulse <60 bpm

(e.g., endurance-trained athletes)

Question 15

what is venous return

Answer 15

Blood returns from periphery to the heart

Question 16

explain the respiratory pump in terms of venous control

Answer 16

Pressure changes in thorax & abdomen during respiration

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

Question 17

explain the skeletal muscle pump in terms of venous control

Answer 17

Skeletal muscles contract in lower limbs

valves in veins contribute to return

Question 18

Important difference between pulmonary & systemic circulation is what

Answer 18

the autoregulatory response to O2

Question 19

explain the autoregulatory response to O2

Answer 19

Systemic circulation dilate if low O2

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

Question 20

Substances enter & leave capillaries by:

Answer 20

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

Question 21

in capillary exchange, what are filtration and reabsorption promoted by

Answer 21

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

Reabsorption promoted by
- Blood colloidal osmotic pressure

Question 22

Whether fluid leaves or enters it depends on what

Answer 22

net balance of pressure

Question 23

explain Starling’s Law of Capillaries

Answer 23

volume of fluid & solutes reabsorbed = volume filtered

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

Question 24

explain the fluid exchange across walls of capillaries

Answer 24

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

Question 25

what can be used if a vessel is obstructed

Answer 25

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

Question 26

what can stents be used to do

Answer 26

open various 'tubes' within the body, with a balloon

Question 27

explain what Inferior Vena Cava Filters are for

Answer 27

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.

Question 28

when does a haemodynamic shock occur

Answer 28

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

Question 29

name the 4 types of haemodynamic shock

Answer 29

Hypovolumic Cardiogenic Vascular Obstructive

Question 30

explain the Hypovolumic haemodynamic shock

Answer 30

decreased blood volume - inadequate intake of fluid - diabetes mellitus may cause much greater fluid loss in urine - sudden haemorrhage - excessive sweating - diarrhoea - vomiting

Question 31

explain the cardiogenic haemodynamic shock

Answer 31

due to poor heart function - heart attack - heart valve problems

Question 32

explain the vascular haemodynamic shock

Answer 32

due to inappropriate vasodilation - anaphylactic shock (histamine release causes vasodilation) - head trauma - septic shock (bacteria)

Question 33

explain the obstructive haemodynamic shock

Answer 33

due to obstruction of blood flow - e.g., pulmonary embolism (clot)

Question 34

what happens if haemodynamic shock is mild

Answer 34

compensation by homeostatic mechanisms to prevent serious damage

Question 35

explain the homeostatic responses to shock

Answer 35

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)

Question 36

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

Answer 36

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

Question 37

describe some signs and symptoms of shock

Answer 37

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)