Physiology -Blood flow Flashcards
describe the circulation to the heart
-how is blood flow controlled?
-pathology
(3 points and one pathology point , explain )
AT REST / WORKING = BLOOD FLOW IS MANTAINED
flow :
1-local metabolic activity =vasodialation due to decreases O2 , increased CO2,NO,increased H+/K+,lactate,prostaglandins
2-Neuronal innervation indirectly = sympathetic nerves in heart = B1 adrenoceptors increase HR,force of contraction which increases metabolic activty hence metabolites which cause dilation ! This outcompetes the effect of the A1 adrenocpetor which causes vasoconstriction
3-Mechanical compression of coronary arteries = highest in systole and least in diastole , so more blood flows to the heart in diastole
Pathology :
LV = Very high pressure , this cases the coronary arteries to be completed compressed in systole = no BLOOD FLOW=prone to ischaemia( decreased BF)= common site for MI ( health muscle death)
circulation to skeletal muscle
percentage rest /excersize
how can it be altered ?
18% –>70% when excercising
1) local metabolic controll =K+,Po4 3-, hypoxia , lactic acid cause vasodilatation
2) neuronal control = A1 noradrenergic vasoconstritor nerves
- adrenergic B2 receptors =vasodialation
- cholinergic vasodilator nerves
3) compressions of blood vessels during exercise alteres blood flow = musclar milking =Rhythmic sustained isometric contraction =better blood flow
circulation to splanchnic (organs in the abdominal cavity )
(3) %
30% in rest state and reduced to 5% in excersize
1) local mechanism =autoregualtion during digestion
2) nervous controll vasoconstrictor nerves in Low Bp cause increase SV/CO remember venoconstriction increase venous return
pulmonary circulation control
2
this is the CO flowing through lungs it can be x4-7 in excersize
1)controlled by local gas tension = hypoxic pulmonary Vasoconstriction ,allows perfusion, ventilation matching ( redirects blood to better ventilated areas)
cutaneous circulation
how do you control heat loss
(2)
4%-20%
1)There is a venous plexus in skin (dissipation of heat from skins surface , arteriovenous anastomoses = smooth muscle that connects arteries and veins , innervated by sympathetic neurones which can cause constriction and decrease blood flow to skin)
cerebral blood flow
(10)
1- during strep the brain needs % o2 consumption how is it controlled, what protects the brain ? 2 systems (2)
2-why is Cerebral blood flow special and how is it different (3)
4-intercranial pressure is a+b+c
5-how can inter cranial pressure increase ?
requires 20% of O2 consumption and this MUST BE MAINTAINED during stress
controll:
1)autoregulation = decreased O2, adenosine , decreased pH ,increased CO2= vasodialation
2)Myogenic response prevents changes in Bp when MAP goes down, the vessels dilate and when MAP increases the vessels constrict
Blood Flow is special the brain :
1-Blood flows directly to active area (you can see this in scans)
2-Blood brain barrier protects the brain and controls what goes in and out . Capillaries have TIGHT junctions which aren’t PERMEABLE=highly selective .
3- Intercranial pressure (ICP) = cranial cavity ( brain+blood+spinal fluid= must be CONSTANT, if the ICP increases the cerebral blood flow decreases )
CEREBRAL PERFUSION PRESSURE= MAP-ICP
the ICP can increase via:
1-Brain volume increases = oedema
2-increase in cerebrospinal fluid = hydrocephalus
3-Increases in Cerebral Blood volume = blockage of venous drainage or vasodilation
what happens when we faint
4
1-when we stand up 300ml-500ml pools in our veins
2-fluid increases in ISF
3-venous return decreases , SV,CO,BP,Cerebral BP decreases
4-decrease in cerebral BP =loss of consciousness
how is our body adapted against fainting/venous pooling?
4
1-Baroreflex ( increases HR/CO)= arteriolar vasoconstriction , causing an increase in BP
2-Cerebral vascular resistance deceases= blood flow increases
3-Muscle pump ( muscular milking )
4-Hormonal system = RAAS system
