L26 Fundamentals of Cardiovascular and Renal Physiology Flashcards
what is important to note after deoxygenated blood has exited alveoli capillaries?
it is still relatively high in oxygen
what happens blood flow in increased temperatures?
blood flow increases, loses heat at skin surface, sweating
how is blood flow physically regulated?
vasodialation(encourages flow) and constriction(limits flow) of arterioles (away from heart)
what are sphincters?
present in capillaries, when relaxed blood flows easily through all capillaries
when are sphinchters contracted?
when we don’t require as much blood flow to our tissues example sitting down
where is water found in the body?
2/3 within cells, 1/3 outside in plasma and interstitial fluid
what 2 systems compose the circulatory system?
cardiovascular system(heart and blood vessels) and lymphatic system
where are lympathic capillaries?
surrounding blood/ cardiovascular capillaries
why are lympathic vessels and capillaries ‘blind ending’?
they bring lymph fluid to subclavian vein which joins with vena cava - returning it to cardiovascular system
what does the lymphatic system do?
drains fluid from tissue and returns leaked plasma to blood vessels, also absorbs digested fats and acts as immune defence via lymph nodes
what would happen without lymphatic system?
20L of blood loss a day by capillaries, lymphatic system returns 3L a day
how does fluid leak from capillaries?
Starling Law/ Forces
what is the Starling Law?
narrow thin walled capillary - blood pressure exerts against walls causing leakiness
20L of blood lost a day due to Starling Law, 3L returned by lymphatic system, what about the rest?
17L returned by plasma proteins and osmotic pressure
what is oedema?
build up of fluid in tissues
known as hypoxia if it occurs in lungs
-can occur from lack of plasma proteins (dysfunctional kidney and liver)
or by increased capillary permeability caused by histamine
how are kidneys involved in osmoregulation?
regulate composition of plasma
what is urine?
filtered plasma?
what is the kidney’s primary function
filtering blood, urine is just a by-product
Describe how Kidneys filter the blood
1) Filtration - blood is filtered, filtrate is formed
2) filtrate undergoes reabsorption
3) filtrate undergoes secretion (non-essential solutes and wastes added)
4) excretion - exits body as urine
what does the kidney consist of?
cortex(outer), medulla(inner), renal artery and vein
what are nephrons?
individual functional units within the kidney that allow filtration of blood
what is Bowman’s capsule?
it contains a network of capillaries known as glomerulus which allows filtration
where does blood enter kidney’s nephrons?
it enters via renal arter into afferent arteriole into the glomerulus
Describe the process of blood filtration
1) blood enters glomerulus capillary network and undergoes filtration
2) efferent arteriole leaves glomerulus, filtrate goes through nephron’s proximal convoluted tubule
3) filtrate goes through loop of Henle (descending followed by ascending limb)
4) filtrate goes through distal tubule and into collecting duct
is the capillary system containing blood, separate from filtrate system in nephron?
YES, diffusion between pathways takes place
what does the filtrate contain in Bowman’s capsule?
water, salts, glucose, amino acids, nitrogenous waste, vitamins
what does the proximal tubule reabsorb?
ions, water and nutrients
what does descending loop of henle absorb?
water through aquaporin channels
what happens in ascending loop of henle?
salt diffusion/ reabsorption - filtrate is v dilute
what happens in distal tubule?
K+ and NaCl, H+ and HCO3- concentrations are regulated, pH regulation of blood
what happens in collecting duct?
filtrate is carried through medulla to renal pelvis and reabsorption of solutes and water occurs
urine is hyperosmotic to body fluids what does this mean?
there is less water in it compared to blood plasma
what are aquaporins?
water holes
what regulates the kidney function?
endocrine and nervous system
what part of blood filtration in kidney requires active transport?
1) proximal tubule (H+, HCO3-, K+)
2) ascending loop of henle (NaCl)
3) distal tubule (NaCl, K+, H+, HCO3-)
4) collecting duct (NaCl)
what molecule/fluid only requires pasisve transport during blood filtration in the kidneys nephrons?
H2O and urea
what hormones from endocrine system effect blood filtration in kidneys?
ADH/ vasopressin
where is ADH secreted?
posterior pituitary gland
what effect does ADH have on blood filtration?
modifies water absorption, increases presence of aquaporins in collecting duct - reduces water urine volume
what happens when ADH is inhibited by alcohol?
increased volume of dilute urine - dehydration
what happens when there is too much water being reabsorped into blood?
posterior gland inhibits production of ADH
how does ADH activate aquaporin formation?
1) ADH binds to receptor of collecting duct cell membrane
2) cAMP secondary messenger is activated
3) cAMP activates PKA
4) PKA activates storage vesicles containing aquaporins to bind with membrane via exocytosis
what happens when osmolarity increases above a set point?
positive negative feedback - osmoreceptors in hypothalamus detect change and ADH secretion increases
what is high blood osmolarity?
blood has higher solute content - not as dilute
when does the blood have high osmolarity?
after profuse sweating
when does the blood have low osmolarity?
after drinking a lot of water
what are major contributors to blood pressure?
blood osmolarity and blood volume
when monitoring blood pressure when do you recieve lowest pressure?
when the sound is no longer audible in stethoscope - pressure in cuff is below 70mmHg
when monitoring blood pressure when do you recieve highest pressure?
when you can hear audible stethoscope, pressure in cuff drops just below 120mmHg
