Unit 2: Week 2 Flashcards
Define BP
BP is the measure of how much force your heart uses to pump blood, measured by pressure in large arteires
What is the normal range for BP?
90/60 140/90
What can result from low BP?
Poor perfusion, inadequate metabolism, eventual necrosis
What can result from high BP?
Capillary damage, loss of fluid in extravascular space
What factors affect BP?
Peripheral resistance- how hard it is to push blood around the CVS
Cardiac output- volume of blood exiting the heart
CO=SVxHR
How viscus the blood is
Circulating blood volume
What is the baroreceptor reflex? how does it work when there is a fall in BP?
The baroreceptor reflex deals with the moment to moment change in BP.
Baroreceptors in the aortic arch and carotid sinus respond to stretch with sends decreased signals from the lower venous return to the medullary cardiovascular control centre. Which activates the sympathetic nervous system
The efferent pathway is then activated from the CNS to the Sinoatrial node- increases heart rate and force of contractions.
The BV undergo vasoconstriction increasing PR and increasing BP
How does the baroreceptor reflex work when there is high BP?
In high BP the baroreceptors send more action potentials to the vasomotor sensor and the parasympathetic nervous system activates, decreasing the rate at which the SA node fires- reducing cardiac output and also dampens the sympathetic tone in blood vessels causing vasodilation.
What are the two regions of the adrenal gland and what are they made of?
The adrenal cortex- outer- mainly hormonal tissue
The adrenal medulla- inner- mainly neural tissue
what are the three zones of the adrenal cortex and what do they secrete?
zona glomerulosa- miniralcorticoids- alodsterone
zona faciculata- glucosecorticoids- cortisol
zona reticularis- gonadochorticoids
screates corticosteroids
What does the adrenal medulla secrete?
chromaffin cells secrete catecholamines- adrenalin and noradrenalin
How does adrenal medulla response work?
It is stimulated by in response to acute stress. The brain sends a nervous response via the thoracolumbar outflow portion of the spinal cord to stimulate chromaffin cells via the preganglionic sympathetic fibres. the secrete catecholamines. they bind to tissue receptors in organ systems to increase force and rate of contractions in the heart and dilate BV in skeletal muscle and constrict BV in the digestive tract.
Adrenaline and noradrenaline eventually metabolise
How does the RAAS work?
A decrease in blood volume, caused by low sodium or dehydration is detected as low pressure by the juxtaglomerular cells in the kidneys and they secrete an enzyme called Renin. Liver cells are also stimulated to make angiotensinogen. Renin converts angiotensinogen into angiotensin 1. AN1 converts to AN2 when passing through the capillaries of the lung where the Angiotensin-converting enzyme is located. AN2 causes SM cells in the BV to contract increasing PR. it also stimulates the adrenal cortex to produce the mineralocorticoid aldosterone. aldosterone caused the kidneys to retain Na+ to which causes a concentration gradient for water to be absorbed back into the BV. aldosterone also decreases K as it is discharged in urine.
How does ANP affect the RAAS?
When there is an elevated blood volume the atria (particularly the R atrium) stretch more and release atrial natriuretic peptide. receptors in arteries dilate to decrease PR. ANP also inhibits aldosterone production to decrease the amount of Na+ in the BV which creates a concentration gradient for water to be moved out of the BV and be expelled in urine.
