Lecture 4: CV Pathophysiology II Flashcards
CO = ?
HR * SV
What is a normal MAP?
100 mmHg
factors that increase heartrate
positive chronotropic effect
factors that decrease heartrate
negative chronotropic effect
factors that increase contractility
positive inotropic effect
factors that decrease contractility
negative inotropic effect
increased EDV leads to increased SV
Frank-Sterling mechanism
stretching of muscle cells allows more actin/myosin cross bridges to form, causing more tension and increasing contractility
length-tension relationship
the degree of stretch of the muscle prior to contraction
preload
What does increasing EDV do to the preload?
increases it
What does hypertension do the contractility and SV?
decreases both (heart must pump against higher arterial pressure)
the load that the heart must pump against
afterload
Which receptors monitor BP?
venous, atrial, and arterial baroreceptors
What are some problems that can arise with the electrical system of the heart?
- SA node irregularities
- AV blocks
- abnormal activation of SNS or PNS
- atrial fibrillation
What are some problems that can arise with the cardiac muscle of the heart?
- unable to relax or expand
- unable to generate sufficient force to eject blood
What are some of the problems that can arise with venous return (preload)?
- central venous pressure too low due to abnormal vasodilation
- low blood volume
- high blood volume (kidney reacting to heart failure)
What are some of the problems that can arise with afterload?
- stiffening of large arteries with age (arteriosclerosis)
- increase in resistance in smaller arteries
How does the filtrate in the glomerulus compare to plasma?
its much lower in concentration of proteins
What are some factors that alter GFR?
- changes in MAP
- contraction of renal arteries
How does contraction of afferent and efferent arterioles affect GFR?
- contraction of AFFERENT decreases GFR by decreasing pressure
- contraction of EFFERENT increases GFR by increasing pressure
when the macula densa cells in the nephron detect a change in Na+/Cl- levels and triggers vasodilation/vasoconstriction of the afferent arteriole to compensate
tubuloglomerular feedback
Describe the differences of sodium and water reabsorption across the nephron.
proximal tubule - 65-75% of sodium reabsorbed; water follows
loop of Henle - 15-20% of sodium reabsorbed (only sodium)
distal tubule - variable; controlled by aldosterone and ADH
What are the most important sensors of BP?
- carotid baroreceptors
- juxtaglomerular apparatus
- macula densa
What is the pathway for renin?
juxtaglomerular apparatus –> renin + angiotensinogen (from liver) –> angiotensin I + ACE (on endothelial cells) –> angiotensin II
What are the effects of angiotensin II?
- increases thirst
- vasoconstriction (decreased blood flow to kidneys)
- increases levels of ADH and aldosterone
What can trigger renin release?
- SNS activity
- decrease in intrarenal BP
- input from macula densa (decreased Na+/Cl- levels)
- angiotensin II (negative feedback)
What are the functions of aldosterone and where does it come from?
- produced by adrenal cortex
- controls activity of Na+/K+/ATPase pumps on the distal tubes and collecting duct
- increases ion reabsorption thus water retention
- aldosterone is also triggered by high extracellular K+ levels
What is atrial natriuretic hormone and what is its function?
- made by atria of the heart (response to stretch/increase blood volume)
- cardio-protective –> lowers plasma volume
- dilates glomerular afferent arterioles = increased Na+ excretion
- inhibits Na+ reabsorption in collecting ducts
Where does ADH/vasopressin come from and what is its function?
- produced by posterior pituitary
- increases reabsorption of water in the distal tubules and collecting ducts by making them permeable to water (aquaporins)
- contraction of smooth muscle throughout body increases MAP
What stimulates/inhibits the release of ADH?
Stimulates: increase in plasma osmolarity, decrease in blood volume, angiotensin II, certain drugs
Inhibits: decrease in plasma osmolarity, increase in blood volume, atrial natriuretic peptide, certain drugs/alcohol
What controls thirst centers in the brain?
- activity of osmoreceptors
- activity of blood volume receptors and baroreceptors
- angiotensin II
What is autotransfusion?
- a decrease in capillary hydrostatic pressure causes fluid to move from interstitium to capillaries; automatic
- activation of SNS –> mobilizes glucose stores –>increase osmolarity promoting fluid reabsorption
How does the baroreceptor reflex kick in during a hemorrhage?
- detects a drop in BP
- increases HR/SV and increases vasoconstriction
How do the kidneys react to a hemorrhage?
- drop in blood pressure decrease GFR
- increase in vasoconstriction also decreases GFR
- ALSO macula densa senses decrease in Na+/Cl- levels
- stimulates renin release
- leads to increase aldosterone/ADH/angiotensin II
- increased thirst
How do kidneys respond to heart failure?
- initially, react same as hemorrhage
- overtime, heart cannot keep up with increase preload
- leads to peripheral and pulmonary edema
How can heart failure be managed/treated?
- low sodium diet (reduces fluid retention
- diuretic drugs
- vasodilators (decrease afterload)
- ionotropic drugs (increase SV, stresses heart)
- synthetic atrial natriuretic hormone (ANP, reduces blood volume)
when someone feels like they are going to pass out but then recover
perisyncope
MAP = ?
CO * TPR
syncope due to blood loss, loss of other fluids, or heat stress
hypovolemic hypotension
syncope due to a fall in BP after standing up, triggering the baroreceptor reflex (response does not occur properly)
postural hypotension
syncope triggered by strong emotion; decrease in SNS and increase in PSN lowers MAP
vasovagal syncope
syncope due to problems with cardiac rhythm and electrical conduction pathways; most worrisome
cardiogenic syncope
What happens during syncope?
- drop in blood pressure leads to disruption of oxygen/nutrient/blood delivery to reticular activating system
- RAS is responsible for keeping you “awake”
What are symptoms of syncope?
- light-headedness
- blurry or dark vision
- fainting
- symptoms disappear/get better when changing posture
- paleness
- clammy and cold hands
- sweating
