Cardio

Question 1

What is hydrostatic pressure

Answer 1

P = ro.gh

ro- density of fluid
G - gravity
H - height

Question 2

What is CO and the determinants of CO

Answer 2

Co = vol of blood ejected by one ventricle in 1 minute

CO = SVxHR

determinant: HR, contractility, preload, afterload

Question 3

What helps regulate the CO?

Answer 3

Neural control:
- Parasympathetic via vagus, Ach (muscarinic M2) R affects HR

• Sympathetic: (T1-4)
  NA beta1 R - affects HR and contractility Ie. preload and afterload

Hormonal: via adrenaline

Question 4

What is the equation for MAP

Answer 4

MAP = P(Dias) + 1/3x (Psys - Pdias)

Pressure = R x Q
So: MAP = SVR X CO
Pulse pressure = Psys-Pdias

At high HR: MAP Pdias+ 1/2 (Ps-Pd)

Question 5

What are the MAP at different points of the body and what causes the difference

Answer 5

Heart 100mmHg
Cerebral A 78mmHg
Femoral A 144mmHg

Changes are caused by hydrostatic pressure

Question 6

Where is blood mainly contained in

Answer 6

Venous system 60%
Heart 10%
Arteries 12 %
Caps 6%
Lungs 12%

Question 7

What kinds of receptors control the CVS

Answer 7

Central control is at the ventro lateral medulla

High P : barotecptors
Low P : volureceptors
Chemoreceptors : hypoxia initiates sympathise adrenal activation
Higher centres : pain and stress

Question 8

Where are the barorecptors and what is their role re CVS control

Answer 8

Located in the aorta and the carotid arteries

With decrease BP there is decrease stretch of A&raquo_space; there is decreased vagal discharge this increased HR; there is increased sympathetic stim&raquo_space; increased HR and contractility in heart, increased arteriolar vasoconstriction; there is activation of the endocrine system (NA/A ADH, angiotensin