physpharm_semester_2_20240426001353 Flashcards
Name the path of blood through the pulmonary circuit starting at the superior and inferior vena cava
- superior/inferior vena cava
- right atrium
- tricuspid valve (right AV valve)
- right ventricle
- pulmonary valve
- pulmonary artery
-pulmonary capillaries (on alveoli)
-pulmonary vein - left atrium
- mitral valve (bicuspid)
- left ventricle
- aortic valve
- aorta
What are the two types of Myocardial cells?
- Contractile (Cardiomyocytes)
- Nodal and Conducting
Nodal and Conducting Cells characteristics
- self excitable (ability to generate action potentials)
- minimal actin and myosin
What is the threshold for a nodal cell to conduct an action potential?
-40mV
Charge of the cell during 1)Depolarization and 2)Repolarization
Depolarization - cell is more positive than RMP
Repolarization - returns back to RMP
Main differences between action potentials in a neuron vs a nodal cell
- Neuron AP is generated and conducted much faster
- In depolarization of a neuron - Na+ rushes in
In depolarization of a myocardial nodal cell - Na rushes in but then right when repolarization starts, Ca rushes in to hold contraction for a bit
What is considered to be the pacemaker of the heart?
SA Node (Sinoatrial node)
- in right atrium
- fastest to excite = generation of APs
What is the conducting system path for action propagation through the heart?
1) SA Node –> Atrial Muscle –> AV Node –> Bundle of His –> Left and Right bundle branches –> Purkinje fibres –> Ventricular Muscle
What is occurring in the heart during each phase of the PQRST cycle?
P - Atrial Depolarization
QRS - Ventricular depolarization
T - Ventricular repolarization
How are cardiomyocytes different than skeletal muscle?
- Branched cells
- Lots of Mitochondria
- Electrically connected
How does a cardiomyocyte action potential that stimulates muscle contraction work?
- Sodium enters, causing very rapid depolarization
- Potassium gates open to start initial repolarization
- Calcium gates open to cause the plateau and to cause contraction of muscle due to calcium induced calcium release in SR
- longer contraction of muscle due to Ca gate staying open (plateau)
- Calcium gates close, and repolarization occurs
What are the Cardiac Cycle phases?
1) Atrial systole
2) Isovolumetric ventricular systole - no blood ejection, ventricular pressure increasing but valves closed
3) Ventricular systole - blood ejected from ventricles
4) Isovolumetric ventricular diastole - contraction of ventricles stopped, AV valves still closed
5) Late ventricular diastole - AV valves open, volume increasing
What is the average number of APs and the average heart rate of a human?
AP - 100 per minute
Heart Rate
- 70/min for male
- 80/min for female
Cardiac Output = ?
Cardiac Output = Stroke Volume x Heart Rate
What is the average intrinsic rate of the SA Node?
100 AP/min
What is the average heart rate for the average human?
Males - 70 beats/min
Females - 80 beats/min
True/False - The parasympathetic nervous system is the rest and digest stimulus pathway of the body
True
Parasympathetic - Rest and Digest
Sympathetic - Fight or Flight
PNS molecule and receptor
Molecule - Acetylcholine (ACh) from the postganglionic neuron
Receptor - Muscarinic receptors
SNS molecule and receptor
Molecule- Norepinephrine (from postganglionic neuron) and Epinephrine (from adrenal medulla respectively)
Receptor - Beta 1 (B1) Adrenergic receptors
Where are the SNS and PNS receptors located in the heart?
- the SA node, AV Node, and ventricular muscle
- notably large amount of B1 adrenergic receptors in ventricular muscle
What do the muscarinic receptors do?
- Increase K permeability
- Decrease Na and Ca permeability
- Result of this is that the stroke volume is lower due to weaker contractions
What do the Beta 1 adrenergic receptors do?
- Increase Na and Ca permeability
- Triggers pathway that opens SR Ca channels
- Stronger contractions so larger stroke volumes
End Diastolic Volume
Amount of blood in ventricle after atrial systole before ventricular systole
- point at which volume of blood in the ventricle is the highest
End Systolic Volume
Amount of blood in ventricle after ventricular systole
- point at which volume of blood in ventricle is the lowest
Stroke Volume = ?
EDV - ESV
Factors controlling stroke volume
1) Autonomic Nervous System
2) Preload on Heart
How does the ANS control stroke volume?
SNS - higher stroke volume due to stronger contractions
PNS - lower stroke volume due to weaker contractions
How does preload on heart affect stroke volume?
Increase in Preload = Increased Stroke volume
- Preload increase = EDV increase
- EDV increase due to increased venous return
(Review) What is an agonist and antagonist?
Agonist - binds to receptor and has an effect on the cell
Antagonist - binds to receptor but has no effect on the cell
What is a cholinergic agonist?
Binds to and activates the muscarinic receptors
- elicits PNS effect on heart (slower HR)
- example: nicotine
What does an acetylcholinesterase inhibitor do?
Inhibits the enzyme acetylcholinesterase, which is supposed to break down acetylcholine
- therefore, ACh is not broken down and PNS is active for longer
What is the effect of Anticholinergics (cholinergic antagonist)?
- prevent Ach from binding to the muscarinic receptors
- prevent PNS activation
What is the effect of adrenergic agonists?
- bind to beta 1 adrenergic receptors (which are all GPCRs) which activates the SNS
- quickens HR
- example: EpiPen
What is the effect of adrenergic antagonists (Beta Blockers)?
- prevent epinephrine and norepinephrine from binding to adrenergic beta 1 receptors
- prevents heart rate from speeding up
- beta blockers usually end in -olol
What is bradycardia?
Condition where the heart is beating too slow
Difference between first generation and second generation beta blockers
First generation - non-selective as to which beta 1 adrenergic receptors it binds to in the body
Second generation - cardioselective
What is a heart Arrhythmia?
A condition where the heart is beating too slow (bradycardia), too quickly (tachycardia), or irregularly (fibrillation)
3 types of arrhythmias
- Supraventricular arrhythmias
- Ventricular arrhythmias
- Bradyarrhythmias
What are the two main reasons arrhythmias occur?
- issue generating action potentials
- issue conducting action potentials
3 main ways arrhythmias can be treated
- Beta blockers
- Channel Blockers (K, Ca, or Na)
- Pacemakers
In what direction does blood flow in during circulation?
High pressure to low pressure
Organization of blood vessels in order from leaving the heart
Arteries - arterioles - capillaries - venules - veins
Characteristics of arteries
- Large diameter
- Thin walls (relative to the diameter)
- Very elastic
- Low resistance
Characteristics of arterioles
- small diameter
- thick walls (relative to the diameter)
- lots of smooth muscle (innervated by SNS)
- CONTROLS BLOOD FLOW
MAP = ?
TPR x CO
Characteristics of capillaries
- one cell thick
- extremely thin walls - allows for gas exchange (diffusion)
- low blood pressure
Two types of capillaries
- Continuous capillary (less permeable)
- Fenestrated capillary (more permeable due to pores connecting it straight to the tissue)
What are Starling forces?
- forces which dictate filtration and reabsorption in the capillaries
- many different forces due to different molecules and gradients
What is edema?
- swelling due to excess fluids accumulating in tissue
- due to excess filtration from capillaries
Characteristics of veins
- large diameter
- very thin walls compared to diameter
- very low blood pressure
- smooth muscle innervated by SNS
What is the skeletal muscle pump in veins?
- smooth muscle in veins constrict in order to bring blood back to the heart
- special valves prevent back flow
- SNS can cause these smooth muscles to contract faster/harder
How does the SNS increase blood flow through venous return?
- innervates smooth muscles in veins (alpha adrenergic receptors)
- faster/stronger contractions = higher EDV (preload)
- higher EDV = increased stroke volume = increase CO
What are the three types of mechanisms used to regulate blood flow?
- Neural mechanisms (SNS and PNS)
- Humoral mechanisms (substances in blood)
- Local (tissue environment)
True/False - The PNS innervates blood vessels and slows blood flow using direct blood vessel control
False
- Only SNS innervates blood vessels (alpha adrenergic receptors)
What are 4 humoral molecules which regulate blood flow?
Vasoconstrictors (stimulus is a decrease in BP)
- ADH
- Angiotensin ll
Vasodilators (stimulus is an increase in BP)
- Atrial natriuretic peptide
- Histamine
Can epinephrine cause vasoconstriction AND vasodilation?
Yes
Vasoconstriction - by binding to alpha adrenergic receptors on blood vessels
Vasodilation - by binding to Beta 2 adrenergic receptors on heart, increasing blood flow indirectly causing blood vessels to dilate due to increased blood flow
The two local mechanisms that control blood flow
Myogenic Theory - increased blood pressure means arterioles stretch, so arterioles contract back after stretching to original state or smaller to control blood flow
Metabolite Theory - change in metabolic needs/metabolites in the blood = higher/lower blood flow
What are the receptors which detect changes in MAP and send signals to the CV centre in the medulla called?
- baroreceptors (mechanoreceptors)
Where are the mechanoreceptors that regulate MAP located?
- walls of aortic arch and the carotid arteries
How does the nervous system adjust the MAP when the it decreases?
- SNS activation
- heart pumps faster and harder = more CO
- Blood vessels constrict = higher TPR
How does the nervous system adjust the MAP when it increases?
- PNS activation
- Heart pumps slower and weaker = lower CO
- PNS activated = no SNS activation on vessels meaning vasodilation = lower TPR
What is hypertension?
- high blood pressure
Blood pressure >140 mm Hg
Targets for treating hypertension
- lowering TPR
- lowering CO
Treatments for hypertension
- beta blockers (block SNS activity on heart)
- Calcium channel blockers
- Angiotensin-converting enzyme inhibitors (ACE inhibitors)
- Angiotensin ll receptor blockers (ARBs)
How do calcium channel blockers help treating hypertension?
- Calcium channel blockers block calcium from entering smooth muscle on arteries = no vasoconstriction and decreased BP
How do ACE inhibitors help treat hypertension?
- prevents angiotensin l going to angiotensin ll
- angiotensin ll leads to high BP by narrowing vessels
- angiotensin 2 stimulates aldosterone production which increases blood pressure
- therefore, stopping this reaction from taking place will decrease BP
What are the two types of calcium channel blockers?
- dihydropyridines (less effect on heart) and non-dihydropyridines (more effect on heart)
How do angiotensin receptor blockers help treat hypertension?
- blocks angiotensin ll from binding to its receptor
- usually, angiotensin ll binding to the receptor causes vasoconstriction, so stopping that from happening will lower blood pressure
What are the three mechanisms of hemostasis?
- vasoconstriction around site of injury
- platelet aggregation to stop bleeding (primary hemostasis)
- coagulation cascade to form stable blood clot (secondary hemostasis)
Why do platelets aggregate at a site of injury?
- platelets adhere to collagen, which is exposed when a vessel is injured
- when platelets contact collagen, they become active, sending chemical mediators (important one is called thromboxane) to recruit other platelets to the site of injury
What is the final and most important product of the coagulation cascade?
- Fibrin
How can aspirin prevent a heart attack or a dangerous blood clot?
- aspiring blocks enzyme responsible for release of thromboxane
- results in less platelets activated and congregated
- smaller/no blood clot formed
What is Warfarin?
-Vitamin K important for synthesis of some clotting factors
- antagonist drug for vitamin K
- therefore, it stops clotting by blocking vitamin K from binding to receptors, inhibiting clotting to continue
What is the functional unit of the kidney?
-The nephron
Two major structures of the nephron
- Renal corpuscle (where filtration of blood occurs)
- Tubule (where the filtered fluid is processed)
Main 5 parts of the nephron
- renal corpuscle
- proximal tubule
- Loop of Henle
- distal convoluted tubule
- collecting duct
Two types of nephrons
- Cortical nephrons (in cortex)
- Juxtamedullary nephrons (very close to medulla but still in cortex) - help in ability to produce more concentrated urine
What is the site of filtration of blood that produces filtrate?
Renal Corpuscle
Parts of the Renal Corpuscle
Bowman’s capsule - where fluid filters into
Glomerulus - specialized leaky capillaries
Juxtaglomerular apparatus - junction of the tubule and arterioles around Bowman’s capsule
Which arteriole enters the renal corpuscle and which arteriole leaves it?
- enters corpuscle - afferent arteriole
- leaves corpuscle - efferent arteriole
TRICK TO REMEMBER- A COMES BEFORE E (A IS ENTERING, E IS LEAVING)
What are the cells that wrap around the glomerulus call and what do they do?
- called podocytes
- fusion of podocytes to glomerulus due to sticky basal lamina
- podocytes prevent filtration of larger molecules from blood
3 Barriers to filtration
- size of the pores in capillaries
- space between the basal lamina matrix
- slit space between podocytes
What molecules are filtered into Bowman’s Capsule from the glomerulus? (5)
- water, amino acids, glucose, ions, gases
3 Processes that occur in the kidney
- filtration (fluid from blood in glomerulus into Bowman’s capsule)
- tubular reabsorption
- tubular secretion
What is the sum of all the forces in the renal corpuscle called?
Net Filtration Pressure
The 4 Pressures affecting glomerular filtration (HCHC)
- Hydrostatic pressure of glomerular capillaries
- Colloid osmotic pressure of glomerular capillaries
- Hydrostatic pressure of Bowman’s capsule
- Colloid osmotic pressure of Bowman’s capsule
What is the hydrostatic pressure of glomerular capillaries (Pgc)?
- pressure cause by blood flowing into the glomerulus
- promotes filtration
~55mm Hg
What is the colloid osmotic pressure of glomerular capillaries(πgc)?
- pressure caused by the presence of proteins in the glomerulus (in the blood)
- inhibits filtration (osmosis)
~ 30mm Hg
What is the hydrostatic pressure of Bowman’s capsule (Pbc)?
- pressure caused by filtrate remaining in the Bowman’s capsule
- inhibits filtration
~ 15 mm Hg
What is the colloid osmotic pressure of Bowman’s capsule (π bc)?
- pressure caused by the proteins in Bowman’s capsule
- promotes filtration
~ 0 mm Hg
Net filtration pressure = ?
NFP = Pgc - (Pbc + πgc)
= 55 - (15 + 30)
= 10
What is the glomerular filtration rate (GFR)?
- amount of fluid filtered by the kidney in a day
- average value of 180 L/day
Factors affecting GFR
- NFP
- Filtration coefficient (affected by the spaces in between podocytes and integrity of basal lamina)
Two autoregulatory mechanisms to keep GFR constant
- the myogenic response
- tubuloglomerular feedback
How does the myogenic response work?
- afferent arteriole stretches from higher blood pressure, causing stretch sensitive ion channels to open
- smooth muscle cells depolarize and calcium channels open, causing contraction of smooth muscles and vasoconstriction of the arteriole
- blood flow decreases in glomerulus
How does tubuloglomerular feedback work?
- macula densa cells sense increase in ions (Na and Cl) due to increased flow rate
- paracrine signalling (adenosine) from these cells to afferent arteriole
- afferent arteriole constricts, reducing hydrostatic pressure in glomerulus and lowering GFR
GFR = ?
GFR = ([Substance] in urine x Urine Volume) / [Substance] in plasma
What does the filtered load calculate?
- how much of a substance is filtered into Bowman’s capsule in a day
True/False - Everything that gets filtered into Bowman’s capsule and enters the tubule system is excreted from the body
False - Reabsorption and more secretion occurs in the tubule system
What molecules are reabsorbed in the proximal convoluted tubule?
- glucose
- sodium
- water
- amino acids
What is reabsorbed in the Descending Limb of the Loop of Henle?
- Water
What is absorbed in the Thick Ascending Limb of the Loop of Henle?
- Reabsorbs ions
- Na, Ca, Mg, K, Cl
What is absorbed in the Distal Convoluted Tubule?
- Ions
What is absorbed in the Collecting Duct?
- reabsorbs water and ions if necessary
Main types of transporters in the tubule
- channels (aquaporins, sodium channels)
- transporters (glucose transporter, sodium/glucose symporter, antiporters - sodium/hydrogen exchanger)
- primary active transporter (sodium/potassium ATPase)
What is diabetes mellitus?
- high concentration of glucose in urine due to high concentration of glucose in plasma
- tubule cannot absorb all the glucose
- high concentration of glucose in urine = high volume of urine due to osmosis
True/False - Most drugs that are filtered into Bowman’s capsule due to not being bound to proteins are reabsorbed in the tubule system
False - most drugs that enter the tubule system are not reabsorbed
What part of the tubule has many drug transporters which allows for selective secretion of drugs from the blood?
The proximal tubule
True/False - Water balance and salt balance work in tandem and are controlled together.
False - Water and salt balance are controlled independently of each other
If total body water decreases, what happens to the extracellular fluid volume and blood pressure?
- Extracellular fluid volume decreases
- blood pressure decreases
What is ADH?
- Also called Vasopressin
- made in hypothalamus
- stored in pituitary
- peptide hormone
- released due to high plasma osmolarity or low extracellular fluid volume
- causes kidney to filter less water, so less water is excreted
What receptors signal for ADH release?
Osmoreceptors (in hypothalamus) - senses increase in osmolarity in blood, so sends signal to release ADH
Baroreceptors - decrease in blood pressure leads to less action potentials being sent to hypothalamus - causes ADH to be released
What does ADH actually do?
- increases number of aquaporin ll channels on membrane of collecting duct
- more water reabsorbed in collecting duct
What is diuresis?
- increased production of urine
What is natriuresis?
- increased excretion of sodium
What is diabetes insipidus?
- failure to release ADH (neurogenic) or failure of collecting duct cells to respond to ADH (nephrogenic)
What do diuretics do?
- inhibit ADH from binding to receptors (V2 receptors)
- V2 receptor antagonists
What are the two hormone systems that regulate body levels of sodium?
- renin-angiotensin-aldosterone system (RAAS) - for when sodium is low
- atrial natriuretic peptide (ANP) - when sodium is high
What secretes renin?
- juxtaglomerular cells
Two receptor types that detect low sodium
- baroreceptors - carotid sinus baroreceptors signal to JG cells (JG cells are also intrarenal baroreceptors)
- chemoreceptors - Macula densa cells detect low Na and signal to JG cells through paracrine signalling
What is angiotensin ll?
- produced from angiotensin l
- stimulus is renin release
- causes increased reabsorption of Na in the proximal tubule
- also causes vasoconstriction of the afferent and efferent arterioles, therefore decreasing GFR
What is Aldosterone?
- steroid hormone that increases reabsorption of Na and secretion of K in principal cells of the collecting duct
What is the atrial natriuretic peptide (ANP)?
- peptide hormone made by the atrial cells of the heart
- stimulus is high blood pressure (will cause an increase in excretion of Na)
- reduces reabsorption of Na by inhibiting aldosterone release and by vasodilation of the afferent arteriole
What are the mechanisms used to treat high blood pressure?
- reducing water absorption/increase water secretion (Diuretics)
- reducing sodium reabsorption
Types of Diuretics
- V2 receptor antagonists (directly blocking ADH from binding to receptors)
- NKCC2 antagonists (blocks NKCC2 symporter - therefore it prevents ion reabsorption)
NCC antagonists - blocks NCC symporter - therefore it decreases sodium reabsorption)
ACE inhibitors - prevents angiotensin l to ll conversion - therefore, prevents Na reabsorption and promotes vasodilation)
Angiotensin ll receptor blockers - prevents binding of Angiotensin ll to receptor - therefore, decreases sodium reabsorption
Aldosterone receptor blockers - block aldosterone from binding to receptor - therefore, reduces sodium reabsorption and prevents K secretion
Sodium channel blockers - inhibits epithelial sodium channels - therefore, reduces sodium reabsorption and prevents K secretion