BMS10-1027 Control of BP Flashcards
What are extrinsic influences and give 2 examples?
Not locally generated
Neural and hormonal means
What are intrinsic influences and what are they important in?
Made locally and influence locally
Organ and tissue blood flow
What do extrinsic influences maintain?
CO, TPR and blood flow at organs and tissues
Where is the cardiovascular control centre?
Medulla oblongata
Describe the PNS path to decreasing heart rate
Nerves release acetylcholine which bind to muscarinic receptors on the pace maker hyperpolarising it to decrease HR
Describe the SNS path to increasing HR
Release noradrenaline which bind to b1 on the pacemaker to increase Ca sensitivity increasing HR and to myocardial cells to increase sarcomere length and contractile force
How does vasoconstriction occur?
Sympathetic neurons release noradrenaline which binds to adrenergic receptors
How does vasodilation occur?
Controlled by adrenaline release
Which hormone has a higher affinity for a1?
Noradrenaline
Why are b2 receptors important?
It promotes dilation in specific tissues due to the fight or flight response
Which receptor does HR and which does dilation?
B1 does HR and A1 does constriction
Do arteries have more PNS or SNS innervation?
SNS
What does the PNS do in extrinsic control?
Vasodilation in select areas e.g. saliva glands, pancreas and sex organs
Which NS can affect TPR as well as redistribute flow and why?
SNS, PNS doesn’t have enough innervation to influence
Angiotensin 2
Hormone causing vasoconstriction
ADH
Vasoconstriction and increased blood volume
ANP
Atrial natriuretic peptide causing vasodilation
Give examples of local factors affecting vascular one
Metabolites
NO
Hormones
Flow pressure
How do arterioles respond to increased pressure and who is this important for ?
Contract to reduce blood flow by increasing resistance to protect the glomerulus from increase pressure
Flow=
Pressure/resistance
How do histamines affect vascular tone?
Released by mast cells encouraging NO release to make capillaries more leaky
Where is NO made?
Endothelial cell
How does No cause vasodilation?
Increases cGMP formation which prevents Ca entry so they cant contract
How are metabolites (metabolic hyperaemia) involved in vasodilation and why is this beneficial?
Lactic acid and carbon dioxide enhance production of things that promote vasodilation
Only happen in active muscles
What is reactive hyperaemia?
When blood flow is cut off metabolites accumulate and cause vasodilation and continues until the metabolites are washed out
Arteriovenous anastomosis
Wide muscular vessels found in skin extremities to stop blood flow from the artery into the venous plexus which is close to the skin surface and would cause blood loss
What 2 things regulate blood flow?
Hypothalamus and SNS
What is special about metabolic hyperaemia in skeletal muscles?
Metabolic hyperaemia can override the SNS during exercise allowing them to dilate
What determines BP?
SV HR TPR Central venous pressure Blood volume
What is TPR also known as?
The afterload- the resistance the heart is pumping against
How is BP regulated?
Baroreceptors are sensitive to stretch in the aortic arch and carotid sinus
The carotid sinus has thin walls so small pressure changes are recognised by the brain stem which can stimulate the SNS or PSN
How does the SNS work to restore BP?
Constrict all vessels to increase central venous pressure and TPR
How does the PNS work to restore BP?
Increase HR and contractile force to increase CO
When standing up, what happens?
Blood pools in lower limbs decreasing CVP so SV and VEDP are decreased
MABP=
CO x HR
What mainly determines MABP?
Blood volume (increase one, the other decreases)
What does MABP influence?
Venous pressure and return, EDV, EDP, SV and CO
What does MABP do when increased for a long period of time?
Promotes excretion of fluid and salt to decrease blood volume and MABP
Control of plasma osmolarity
Hypothalamus detects it using osmoreceptors which makes us thirsty and makes the pituitary glad release ADH which adds aquaporin to increase water reabsorption in the distal nephron
What causes an increase in plasma osmolarity?
Increase sodium intake or dehydration
Why does plasma need to be osmotically balanced?
Make sure don’t loose too much water and become dehydrated
What ion controls blood volume?
Na
What is more important osmolarity or blood volume?
Osmolarity
What hormone is released when there is lots of stretching?
Myocytes in the atria release ANP which promotes urine production and Na excretion
What else happens with lots of stretching?
Copies the baroreceptor to decrease SNS activity to reduce MABP and renal stimulation
What is pressure natriuresis?
Increased arterial pressure increases metabolite release in the renal artery which increases flow in the renal medulla to increase Na secretion
What happens in the glomerulus when blood volume decreases?
Increase renal sympathetic drive so the afferent arteriole constricts and renin is released
Where is renin released from?
Juxtaglomerular
What does renin do?
Convert angiotensinogen to angiotensin 1 and then 2
What does angiotensin 2 do? (3)
Vasoconstrictor
ADH release for water reabsorption
Aldosterone for Na resorption
What does the hypothalamus to in response to atria stretch?
Decrease ADH to increase urine production
Decrease renal sympathetic activity so less renin is made to decrease Na water reabsorption
How does the vasogagal syncope work?
Overrides fight of flight to decrease SNS and increase PNS
This decreases HR and vasodilation so BP falls making you faint
What factor affects diastolic pressure?
Stress
Posture change
Exercise
What factors affect systolic pressure?
Health
What factors affect arterial pressure?
Arterial stiffness
Cardiac output
TPR
