Blood pressure and volume

Page 1

Altering flow

-changing vascular resistance

--vasocontriction and vasodilation

-changing perfusion pressure

Flow to tissues

-within range of normal BPS low is altered by intrinsic mechanisms

--AUTOREGULATION

-these can be overwhelmed by extrinsic mechanisms to maintain BP in times of need

--blood flow to brain coronary circa and skeletal muscle maintained

Intrinsic control

-metabolic autoregulation matches blood flow to met rate of tissue

-paracrine control - locally acting chemicals ...

Active hyperaemia

inc met rate inc blood flow

CO2 lactic acid an K vasodilators

02 is vasoconstriction STREAM

In essential tissues intrinsic remains in charge to ensure brain gets right blood flow

for quite a range of blood flow

3 graphs - stream?

Reactive hyperaemia

-when blood flow restricted products still produces, build up of waste products

-blood flow inc until returned to normal

ischaemia

infarction STREAM

nercosis

NB coronary blood flow occurs mainly in diastole

-- Stream

ischaemic exercise-- weight training

--sustained contraction squashes blood arteries

--less blood supply

--inc blood pressure

--infarction risk and ischaemic injury

STREAM slide 11

Paracrine controls

-- nitric oxide - released from endothelial cells

-inside of blood vessels- tunica intima

-inside of heart

--causes vaso dilation

histamine

-mediated by nitric oxide

-vasodilation

endothelial damage

-endothelin 1 - vasoconstriction

-thromboxane from platelets-- vasoconstriction

Extrinsic control

-brain cardiac muscle and workng skeletal muscle considered essential

-everything else is temporarily compromised to preserve flow to essential tissues

-reduced blood flow else where -- build up of CO2 K lactic acid-- causes vasodilation

----blood pressure drops

-coordinated by autonomic nervous system

--baroreflex

-RAAS

-hypothalamous

-pituitary

Cardiovascular centre

medulla oblongata

Baroreflex

-fast acting and life saving

-baroreceptors

-decides how much vessels stretch

-info via cranial nerves

--greater the stretch the faster action potentials .

---too high drop blood pressure

---too low inc blood pressure

-atria volume something

Drop in BP red APs

-inc sap out put

-inc HR

-shorthens Systole

Slide 17 -- stream

RAAS

-longer to kick in

-drop in BP inc symphony activity

-renin produced ---- angiotensin 1 made

-lung converts 1 to 2

-angiotensin 2 causes more vasoconstriction and release of aldosterone

--also causes hypothalamus to inc thirst sensation and ADH releases

-aldos causes inc of H2O retention in kidney

--inc BP

equally opposite if BP to high

Starlings law

-vasoconstricition of arterioles, red blood flow in capillaries red hydrostat

STREAM

Long term BP regulation governed by kidneys

-reference BP can be resent -- dodgy kidneys

System over rides

-fight or flight can bypass cardiovascular system -- blood flow to brain inc

-fainting from fear does opposite -- blood flow to brain dec