Blood Pressure Regulation Flashcards
What is blood pressure?
The force exerted upon vessel walls as blood flows through (measured in large muscular arteries)
A minimum pressure (capillary hydrostatic pressure) is required to exchange substances/fluids across capillary networks into the interstitial fluid = capillary exchange
What are the determinants of blood pressure?
Blood pressure is determined by:
* Cardiac output (HR X SV)
* Total Peripheral Resistance
Total Peripheral Resistance is dependent upon arteriolar radius.
What are the two main types of blood pressure regulation?
Short-term = Neural (for activities such as climbing stairs)
Long-term regulation = Endocrine (for more extreme activities)
This is known as autoregulation of local flow OR intrinsic control = regulation of blood flow at rest
What role do baroreceptors play in blood pressure regulation?
Located in aortic sinus (main) and carotid sinus
Baroreceptors detect changes in blood pressure and activate cardiovascular centres in the CNS
They facilitate short-term increases in blood pressure through sympathetic nervous system activation.
What is the function of chemoreceptors in blood pressure regulation?
Chemoreceptors detect changes in blood chemistry (e.g., CO2, pH, O2) and influence cardiovascular and respiratory responses
They help maintain blood flow to the brain during low oxygen conditions.
Fill in the blank: The _______ system is involved in long-term regulation of blood pressure.
Renin-Angiotensin-Aldosterone System (RAAS)
RAAS is activated in response to low blood pressure and promotes vasoconstriction and fluid retention.
What happens during the activation of the sympathetic nervous system in response to low blood pressure?
Increased heart rate (HR), increased stroke volume (SV), and vasoconstriction
This response helps to raise blood pressure quickly.
List the components involved in the Renin-Angiotensin-Aldosterone System (RAAS).
- Angiotensinogen
- Renin
- Angiotensin I
- Angiotensin Converting Enzyme (ACE)
- Angiotensin II
- Aldosterone
This system is crucial for regulating blood volume and pressure.
True or False: Autoregulation of blood flow is sufficient to restore homeostasis in all situations.
False
Autoregulation is insufficient when blood pressure and flow are too low to meet tissue demands.
What is the primary response to severe hemorrhage?
Activation of endocrine responses (RAAS activation, vasopressin release, catecholamine release) to increase blood volume, cardiac stimulation and vasoconstriction
OR
SNS activation of baro & chemoreceptors to increase cardiac stimulation, systemic vasoconstriction and fluid & volume redistribution
How does blood flow regulation differ in the pulmonary circulation?
In the lungs, arterioles constrict in regions of low O2 to shunt blood flow to O2-rich areas
This is opposite to most other organs where vessels dilate when O2 falls.
What is the significance of the cardiovascular centre in the medulla oblongata?
It coordinates responses to changes in blood pressure detected by baroreceptors
It influences sympathetic and parasympathetic responses to regulate heart rate and vascular tone.
What happens to blood pressure when the body detects a rise in CO2 levels?
Blood pressure increases due to peripheral vasoconstriction and increased heart rate
This is part of the body’s effort to enhance oxygen delivery to tissues.
Fill in the blank: The _______ is responsible for releasing erythropoietin (Epo) in response to low oxygen levels.
Kidney
Epo stimulates red blood cell formation, helping to increase oxygen-carrying capacity.
What is the effect of increased Na+ loss in urine on blood pressure?
It leads to reduced blood volume and lower blood pressure
This is part of the body’s mechanism to manage high blood pressure.
List the special considerations for local blood flow regulation.
- Coronary Circulation
- Pulmonary Circulation
- Cerebral Circulation
These areas have unique requirements to maintain adequate blood supply under varying conditions.
Which branch of the autonomic nervous system is activated to restore BP in short-term regulation of blood pressure?
Sympathetic branch
SA node & ventricular muscle cells have receptors to receive impulses from the branch = increased HR and SV
Also increases peripheral resistance = higher blood pressure
Describe short term regulation of blood pressure
- autoregulation insufficient to restore homeostasis
- detected by receptors sensitive to pressure/chemical changes i.e. baro/chemo receptors
- activation of cardiovascular centres in CNS in medulla oblongata
- short term increase in BP via SNS activation
- increasing CO and Vasoconstriction
- homeostasis reached
What is the role of baroreceptor reflexes?
Sensitive to changes in pressure (response enhanced by NA/ adrenaline secretion from adrenal glands)
Fall in BP
Baroreceptor inhibition (less activation):
- Cardioacceloratory centre activation = increases HR & CO
- Cardioinhibitory centre inhibition (connected to parasympathetic system) = increases HR & CO
- Vasomotor centre activation = vasoconstriction (constriction of arterioles)
Rise in BP
Baroreceptor stimulation:
- Cardioacceleratory centre inhibition = decreases HR & CO
- Cardioinhibitory centre activation = decreases HR & CO
- Meaning less sympathetic activity and more parasympathetic activity
- Vasomotor centre inhibition = vasodilation
What is the role of chemoreceptor reflexes?
Located in medulla oblongata (CFS) but only sensitive to CO2 and carotid body (blood) but only sensitive to any chemical changes
Coordination of cardiovascular & respiratory response
Rise in CO2
- Respiratory centre activation = increases respiratory rate
- Vasodilation of cerebral vessels (this is an anomaly to general rules) = increases blood flow to brain
Rise in CO2, Fall in O2, Fall in pH (chemical changes)
- Vasomotor centre activation = peripheral vasoconstriction
- Cardioacceleratory centre activation & Cardioinhibitory centre inhibition = increases HR & CO
What is the role of ADH in the endocrine response to LOW blood pressure?
ADH = anti-diuretic hormone
- Fall in BP or increased blood osmolarity
- ADH in pituitary gland
- Increases fluid retention (and increases thirst)
- Increases vasoconstriction
What is the role of Epo in the endocrine response to LOW blood pressure?
Epo = erythropoietin (main hormone to form red blood cells)
- increases vasoconstriction
- increases blood volume
- Epo is in the kidneys
What is the role of the Renin-Angiotensin-Aldosterone system (RAAS) in the endocrine response to LOW blood pressure?
MOST IMPORTANT RESPONSE
- Fall in renal BP detected by kidney
- Produces Renin
- Angiotensinogen from liver combines with renin
- Produces Angiotensin I which is inactivate on its own
- This combines with angiotensin converting enzyme from the lungs
- Produces Angiotensin II = a potent vasoconstrictor (8x more potent) causing vasoconstriction
- Goes through adrenals and becomes aldosterone
- Aldosterone = steroid that regulates fluid collection in kidney
- This increases Na+ reabsorption and fluid retention = increases blood volume
What happens in long term regulation of HIGH blood pressure?
- Rise in BP & volume
- Stretching of cardiac muscle cells in right atrium and ventricle
- Release of natriuretic peptides ANP (from atria) and BNP (from ventricles)
- Renal effects = DECREASES blood volume
- increased Na+ loss in urine (less reabsorbed)
- increased water loss in urine
- reduced thirst - Vascular effects = DECREASES blood pressure
- inhibition of ADH, aldosterone, NA & adrenaline release
- peripheral vasodilation - Homeostasis reached
