Blood pressure 2 Flashcards
Define blood pressure
pressure exerted by circulating blood upon the
walls of blood vessels. Force applied to the vessel walls.
What is flow rate of blood?
volume of blood flowing through a specific vessel - or organ - over a peroid of time (L.min)
Directly proportional to pressure gradient
Inversely proportional to vascular resistance
What causes resistance to blood flow?
- Vessel dimensions
Length
Radius
Blood ‘rubbing’
Greater the surface area = Greater the resistance
why does length cause resistance to blood flow?
brain near the heart (shorter distance)
define cardiac output
volume of blood pumped by the heart
how to calculate cardiac output?
CO = heart rate x ventricle stroke volume = dm3/min, L/min
Define peripheral resistance?
resistance of arteries and arterioles to blood flow
Any factor causing WHAT to change will result in a change in blood pressure?
cardiac output
peripheral resistance
Mean Arterial Blood Pressure (MAP) is clinically defined as?
perfusion pressure
what is perfusion pressure normally?
70-110 mmHg
what is skin perfusion pressure?
local pressure in the microscirculation
What is the function of skin perfusion pressure (SPP)?
Predicting wound healing
Amputation level determination, in particular major amputations
sympathetic affect on regulation of blood pressure?
increased HR and BP
parasympathetic affect on regulation of blood pressure?
decreased HR and BP
What do baroreceptors influence?
Influences heart and blood vessels to adjust pressure and
total peripheral resistance
what are the most important baroreceptors located?
- Carotid sinus – arterial BP to the brain
- Aortic arch baroreceptors – major arterial trunk
what do baroreceptors generate?
continuously generated action potentials in response to ongoing pressure in the arteries.
increased arterial pressure =
increased rate of neuronal firing
decreased arterial pressure =
decreased rate of neuronal firing.
Where is the integrating centre located?
medulla oblongata
what does the integrating centre contain?
Cardiac, respiratory, vomiting and vasomotor centres
What does the integrating centre receive?
Receives afferent impulses from peripheral organs
decreased heart rate and vasodilation = ?
decreased blood pressure
increased heart rate + vasocontriction = ?
increased blood pressure
what affects heart rate and vasoconstriciton/dilation?
- Carotid sinus & aortic arch baroreceptors affects rate of afferent firing.
- Medulla oblongata regulates synpathetic and parasympathetic activity to control vasocons/dila.
What neurons are involved in parasympathetic (rest/digest) division and sympathetic divisions (fight/flight) ?
rest/digest = cholinergic neurons
fight/flight = initially cholinergic then noradrenergic neurons post synapse.
what do post synaptic noradrenergic neurons in the sympathetic division bind to?
binds to muscle (a and b receptors).
what do post synaptic cholinergic neurons in the para-sympathetic division bind to?
binds to muscle (m receptors)
Many other factors contribute to BP modulation (Acutely & chronically) which are?
O2 & CO2
Hypothalamic activity
Autonomic ‘fast’
Hormonal ‘slow’
RAAS
Endothelial-derived relaxing factor
Bradykinin
Histamine
Body composition
Gender
Many others
norepinephrine and epinephrine are both known as…
catecholamines
name of channels in sinoatrial node cells ?
funny channels
what are M receptors?
Muscarinic
define micturition
the act of urination
What are the Two types of acetylcholine receptors (AChR) ?
Nicotinic AChRs
Muscarinic AChRs important in parasympathetic activity
Where are chemoreceptors located?
Located in carotid and aortic arteries
What are chemoreceptors sensitive to?
… Sensitive to low O2 or high acid levels in the blood
If blood pressure is low, what hapens to circulation?
circulation is less efficient
If blood pressure is low, circulation is less efficient. What happens as a result?
- PO2 decreases
- PCO2 increases
- H+ increases
Chemoreceptors send…
…impulses via sensory nerves to
the medulla oblongata
What is the hypothalamus responsible for?
Metabolic processes & activities
body temperature, hunger, thirst, sleep, circadian cycles, etc.
Hypothalamic Neural Control of SMS?
Projections to areas of the
SMS = Increase or decrease sympathetic activity.
e.g.
Hypothermia shivering
Hyperthermia vasodilation
What sections of the hypothalamus inluence antidiuretic hormone
- Paraventricular Nucleus of Hypothalamus (PVN)
- Supraoptic Nucleus (SON)
where is the Paraventricular Nucleus (PVN) of the Hypothalamus located?
Location: Located in the hypothalamus.
Paraventricular Nucleus (PVN) of the Hypothalamus function?
Produces and regulates the release of ADH and other hormones. It plays a key role in fluid balance and stress response.
Supraoptic Nucleus (SON) located?
Also found in the hypothalamus, adjacent to the PVN.
Supraoptic Nucleus (SON) function?
Similar to the PVN, it produces ADH and releases it into the bloodstream through the neurohypophysis.
where is Antidiuretic Hormone (ADH) / Arginine Vasopressin synthesised?
Synthesized in the PVN and SON.
where is Antidiuretic Hormone (ADH) / Arginine Vasopressin released into?
Released into the bloodstream via the neurohypophysis (posterior pituitary gland) in response to increased plasma osmolality or low blood volume.
where are Water Channels (Aquaporin-2) located?
Present in the cells of the distal tubule and collecting duct of the nephron.
action of Water Channels (Aquaporin-2)?
ADH binds to receptors on these cells, leading to an increase in the expression and insertion of aquaporin-2 channels into the apical membrane.
Water Channels (Aquaporin-2)
- Location: Present in the cells of the distal tubule and collecting duct of the nephron.
- Action: ADH binds to receptors on these cells, leading to an increase in the expression and insertion of aquaporin-2 channels into the apical membrane.
What is the effect of this?
This increases water permeability, allowing more water to be reabsorbed from the urine back into the bloodstream, resulting in increased urine osmolality (more concentrated urine).
where are Urea Transporters found?
Found in the inner medullary portion of the collecting duct
what affect does ADH have on urea transporters?
- ADH increases the cell surface expression of urea transporters.
- Effect: This enhances the reabsorption of urea, contributing to the osmotic gradient that facilitates further water reabsorption.
Whats does the Renin-angiotensin-aldosterone system (RAAS) regulate?
Regulates:
i. Body’s salt balance
ii. Water retention
iii. Blood pressure
whats renin synthesised and stored as ?
Synthetized & stored as pro-renin in juxtaglomerular cells
Renal sympathetic activity (adrenaline/noradrenaline) is controlled by…
… B1 adrenergic receptors
How does renin convert to angiotensin I ?
Renin substrate cleaves angiotensinogen to produce angiotensin I
What is angiotensinogen ?
α-2-globulin produced constitutively by the liver and adipose tissue.
Angiotensinogen+Renin→?
AngiotensinI
Angiotensin I is then converted to…
… angiotensin II by the action of the angiotensin-converting enzyme (ACE), primarily in the lungs.
Angiotensinogen is located mainly in…
…lung capillaries but also found in lower levels in endothelium (brain, testis, etc) and kidney epithelial cells
Angiotensin II - Central nervous system effects
Increases thirst sensation (dipsogenic) & Increases desire for salt
peripheral affects of angiotensin II?
- Stimulates release of aldosterone
- Vasoconstriction (activates IP3 ↑ intracellular Ca++)
- Na+/H+ exchanger in proximal tubules
Na+ reabsorption
H+ excretion
bicarbonate (HCO3−) reabsorption
whats aldosterone?
Steroid, mineralocorticoid hormone
where is aldosterone produced?
Zona glomerulosa of adrenal cortex
what does aldosterone bind to?
Nuclear mineralocorticoid receptors (MR) in distal tubule and collecting ducts of the nephron
Whats the function of aldosterone?
- Upregulates basolateral Na+/K+
pumps - Upregulates epithelial sodium channels (ENaCs), increasing apical membrane permeability for Na+
aldosterone stimulates…
…Na+ and water reabsorption from the gut,
salivary and sweat glands in exchange for K+
Aldosterone allows secretion of …
…H+ in exchange for Na+ in the intercalated
cells of the cortical collecting tubules, regulating plasma bicarbonate (HCO3−) levels and its acid/base balance.
what causes decreased blood pressure?
Dehydration, blood losses, anaphylaxis, etc.
what does ACE stand for?
Angiotensin-Converting Enzyme
Where is ACE produced?
lungs
What is the main cause of hypertension?
obesity
describe adipose tissue in obesity?
adipose tissue poorly vascularised
Obesity affect on vascular resistance 🥶😶🌫️😳?
Vascular resistance dramatically increased
Obesity affect on cardiac output?
Compensatory increased Cardiac Output
Obesity affect on perfusion pressure?
Decreased perfusion pressure
Obesity causes…
…hypoxia, which causes inflammation
whats hypoxia?
Hypoxia is a condition where the body’s tissues do not receive adequate oxygen supply at the tissue level
Why is inflammation caused by obesity a problem?
Deterrent to healing & wound breakdown
Acute affects of physical activity?
Increased blood pressure, heart frequency,
cardiac output
Chronic affects of physical activity?
Skeletal muscle – highly vascularized
Increases muscle mass – angiogenesis
Decreases vascular resistance
Decreases diastolic blood pressure
Muscle is highly…
… vascularised
One pound of muscle contains …
… about 6.5 miles of blood vessels
adipose tissue is poorly…
…poorly vascularised 🥹
- leads to vascular resistance.
