Understanding the physiology of the cardiovascular system Flashcards
what are the components of the cardiovascular system
- cardiopulmonary unit
- left and right side
- pulmonary artery and vein
- arteries, arterioles, capillaries, venules and veins
- portal systems
- intra-renal circulation
- intra-coronary circulation
- intra-cranial circulation
what are portal systems. give examples
an arrangement by which deoxygenated blood collected from are from a set of capillaries passess through a large vessel or vessels to another set of capillaries before it returns to the systemic circulation
e.g., -> hepatic portal system -> hypothalamic + anterior pituitary (hypophyseal)
hypophyseal
hypothalmic and anterior pituitary portal system
stroke volume
the volume of blood pumper by the left ventricle per beat. denoted by SV
cardiac output
the volume of blood pumped by the heart per unit time. measured as L/min and denoted by Q
perfusion
the passage of blood through the circulatory system to the body’s tissues. measured as ml of blood/min/g of tissue
preload
the degree to which the left ventricle is filled at the end of diastole, just prior to systolic contraction. measured as mL and denoted as EDV
contracticity
the innate ability of the myocardium to contract
afterload
the resistance against which the L ventricle must eject the SV from the heart. measured as aortic pressure during systole divided by cardiac output
compliance
the ability of the blood vessel to expand and contract with changes in pressure. measured as unit of volume change per unit of pressure change. denoted by C
functions of the cardiovascular system
- rapid connective transport of O2, glucose, amino acids + fatty acids, vitamins, water, waste products of metabolism, i.e., CO2, urea, creatinine.
- homeostatic control- hormones and temperature
factors that affect heart rate
atrial reflex, autonomic innervation, hormones
atrial reflex
The Bainbridge reflex (aka, atrial reflex) occurs when the heart rate increases in response to a rise in atrial pressure. This is a compensatory mechanism since increased right atrial pressures frequently result from elevated left heart pressures from decreased cardiac output.
factors that affect stroke volume
venous return, filling time, autonomic innervation, hormones, vasodilation/vasoconstriction
what factors affect preload
venous return, filling time
what factors affect contractility
autonomic innervation and hormones
what factor affects afterload
vasodilation/vasoconstriction
factor that affects end diastolic volume
preload
factors that affect end systolic volume
preload, contractility and afterload
stroke volume formula
EDV-ESV
formula for Q
HR x SV
define frank-starling mechanism
the SV of the heart increase in response to an increase in the vol of blood in the ventricles before contraction when all other factors remain constant
what do each of the four corners on the frank-starling graph stand for
- mitral valve closes
- Aortic valve opens
- Aortic Valve closes
- Mitral Valve closes
an increase in preload, afterload or contractility would lead to an ____ in EDV, _____ in ESV and ____ in stroke volume
- increase
- decrease
- increase
a decrase in preload, afterload or contractility would lead to an ____ in EDV, _____ in ESV and ____ in stroke volume
- decrease
- increase
- decrease
what are the two main extrinsic controls of circulation
- autonomic: sympathetic and parasympathetic
2. RAAS System
where are the parasympathetic control centres/nerves locate
brain stem, cranial nerves, sacral outflow, end organ ganglia, postganglionic (ACh + adrenergic, non-cholinergic (NANC) transmitters)
where are the sympathetic control centres/nerves located
brain stem, spinal cord, preganglionic fibres (ACh), spinal ganglia, postganglionic fibres (NA), distant ganglial (coeliac + hypogastric ganglia and the adrenal medulla)
sympathetic stimulation of the blood vessels would lead to ….
vasoconstriction
ionotropy
contractility
chronotropy
heart rate
dromotropy
velocity of the AV node
agonism of a1 , a2 and b1 receptors would ______ iontropy, chronotopy and dromotropy and cause _______
increase, vasoconstriction
agonism of b2 receptors would _______ ionotropy, chornotropy and dromotropy and cause ________
decrease, vasodilation
when is RAAS system triggered
drop in blood pressure or blood volume
RAAS mechanism
- angiotensin is released by the liver
- renin produced by the kidney acts on the angiotensin and forms angiotensin I
- ACE is released by the lungs+ kidneys that converts angiotensin I to angiotensin II
- Angiotensin II acts on the adrenal gland to release aldosterone
- Aldosterone acts on the kidneys to stimulate reabsorption of NaCl and H2O.
- Angiotensin II also acts on the blood vessels and stimulates vasoconstriction
what cells produce renin
juxtaglomerular cells in the afferent arteriole of the renal glomerulus.
what stimulates the production of renin by the kidneys
- sympathetic nerve activation (acting via the b1 receptor)
- renal artery hypotension (caused by systemic hypotension or renal artery stenosis)
- decreased sodium delivery to the distal tubules of the kidney sensed by the cells in the Macula Densa
what cells produce ACE and what is it’s purpose
vascular endothelium, especially in the lungs contain ACE and that cleaves Ang-I to Ang-II
what are the two receptors that Ang-II acts on
T1 receptors- vasoconstriction, cell proflieration, inflammatory responses, blood coagulation, extracellular matrix remodelling
T2 receptors counteract these effects
actions of Ang-II on the CVS
- constricts resistance vessels thereby increase SVR and arterial pressure
- stimulates sodium transport (reabsorption) at several renal tubular sites, thereby increasing sodium and water retention
- acts on the adrenal cortex to release aldosterone
- stimulates thirst
- facilitates noradrenaline release from sympathetic nerve endings and inhibits it reuptake
- stimulates cardiac hypertrophy and vascular hypertrophy
actions of aldosterone on the CVS
- affects the final part of electrolyte and water absorption within the nephron before acretion in the urine
- increases the amt of sodium reabsorbed from the distal tubule and collecting duct of the kidney
actions of adrenaline on the CVS
stimulates all major receptors- a1, a2, b1, b2. at low concentrations in b2 selective, it causes vasodilation and at higher concentrations, it stimulates the other adrenergic receptors causing vasoconstriction and this increases heart rate and contractility. also causes renal arterioles vasoconstriction, reducing blood flow to the glomeruli and nephrons
when is Antidiuretic hormone or Arginine vasopressin released
during hypovolaemic shock
where is Antidiuretic hormone or Arginine vasopressin synthesised
hypothalamus and released from the posterior pituitary gland
what is Antidiuretic hormone or Arginine vasopressin released in response to
reduction in plasma volume, and an increase in plasma osmolarity
ADH affect on CVS
acts via V1 receptors to cause arteriolar constriction
ADH affect on kidney
acts via V2 receptors to cause increase in the amt of water reabsoprtion by renal tubules
natriuretic peptide
produced, stored and released by atrial myocytes due to atrial distention. acts in response to high renal Na+ excretion and in response to increased stretching of the atrial blood volume.`
two kinds of natriuretic peptides produced by the heart
BNP, ANP
