Basic heart stuff
Transport & distribute essential substances under dynamic physiological conditions
Remove metabolic byproducts from tissues
maintenance fluid balance
Regulate body temperature
What does an electrocardiogram do? how does it do it?
Cardiac impulse spreads through the heart -> a portion spreads out across the surface of the body
Recording and reference electrodes placed on the body in a specific orientation can record an ECG
Parasympathetic aspects of the heart?
Rest and Digest
Project from cranial and sacral nerves
vagus nerve (x) innervates the heart directly
tonic firing in heart, slow down heart rate
Cholinergic signaling
Baroreceptors are located where? what do they do?
Atria, aorta, and carotid arteries
Detect stretch (increase stretch engages afferents that activate vagal efferents, decrease stretch disengages same afferent signals)
Myogenic (mechanical) for blood flow regulation steps?
helps buffer against BP fluctations
Stretch detectors - increase pressure to decrease diameter
VSM drives the response
Systemic circulation vs pulmonary circulation?
systemic = left side of heart pumps oxygenated blood, pumps blood to body for nutrient and gas exchange with tissues
pulmonary = right side of heart pumps de-oxygenated blood, pumps blood to lungs for gas exchange with external environment
The waves of an ECG include? aspects of each wave?
Right atrium depolarizes
p wave = left atrium depolarizes and atrium contracts
PR interval = wave spreads through AV node and AV bundle, conduction velocity between SA and AV nodes
QRS wave = ventricular depolarization & contraction, contraction begins just after Q through T wave, masks atrial repolarization
then there is ventricular repolarization
Sympathetic aspects of the heart?
fight or flight
project from thoracic and lumbar nerves
ganglia located near the spine
not targeted
sympathetic nerves innervate heart, arteries, veins and adrenal glands
Tonic firing
Cholinergic signaling at ganglia, adrenergic signaling at the organ, neurohumoral signaling
RAAS is?
regulation of blood volume and SVR -> CO and MAP
juxtaglomerular cells associated with afferent renal artery are primary site for renin release
Endothelial shear stress helps with?
Helps maintain tone
helps enhance blood flow delivery
respond to external environments
produces dilation in most arteries
produces constriction in brain
relays signal to VSM
Path of blood through circulation is?
Vena cava -> Right atria -> right ventricle -> pulomary arteries -> lungs -> pulmonary veins -> left atria -> left ventricle -> aorta -> systemic arteries -> capillaries -> systemic veins
What is a Sacromere?
Contractile unit of cardiomyocyte
increase stretch to increase force of contraction
Optimal length to produce maximal force
operating point
Properties of the autonomic system of the heart
Vagus (PNS) nerve innervates SA and AV nodes
adrenergic nerves are more diffuse
the location that generates action potentials at the highest frequency sets the pace
the only way to slow the heart rate down is to reduce the frequency and conduction of AP
muscular components of cardiac function are modulated by adrenergic vs vagal nerves
The two equations for blood flow are?
q = (change)P/R
R = 8Ln/(pi)r4
Metabolic/neurogenic (intrinsic) blood flow regulation steps?
Neurotransmitters elicit dilation
target = VSM + endothelium
matches flow to metabolism
Highly localized to active neurons
May include neurogenic spill over
predominantly in brain and muscle
The conduction system of the heart includes?
Autorhythmic cells - pacemaker (SA and AV node, generate APs spontaneously, fastest rate sets the pace), Conduction fibers (spread throughout the heart, generate APs spontaneously but at a much slower rate)
AP spread through gap junctions
The phases of the Frank starling mechanism?
Phase A: Diastole, LV filling
Phase B: systole, isovolumetric contraction
Phase c: systole, ejection period
Phase D: Diastole, isovolumetric relaxation
Adrenergic nerves release NE
adrenals release NE (20%)
NE acts on a1-adrenergic receptors
a1-adrenergic receptors are located in arteries and veins
a1-adrenergic receptors activate the IP3 pathway, increases intracellular Ca2+ and causes vasoconstriction
NE mediates a-constriction, Target = VSM, systemic response helps maintain blood pressure
or
EPI elicits modest dilation but can stimulate vasoconstriction, Target = VSM, Systemic response attenuates a-mediated vasoconstriction
Endothelial blood flow regulation - differences in steps between ACh Bradykinin and Insulin vs Insulin Cytokines and thrombin?
A & B & I = redistribution of blood flow, responds to & produces dilators, responds to & produces constrictors, Relays signal to VSM, (note on NO)
I & C & T = Redistribution of blood flow, responds to & produces dilators, Responds to & produces constrictors, Relays signal to VSM, (note on feedback, NO vs ET1 status)
The impulse conducting system path is?
Autorhythmic cells generate action potential spontaneously, Conduction fibers spread impulses throughout the heart, impulse travels from cell-cell via gap junctions
depolarization/ impulse wave = SA node -> Across atria -> AV node -> AV bundle/L/R bundle branches -> purkinjie fibers -> recovery
How many sounds does the heart make? how?
Predominant sound caused by vibration of valves, chordae tendineae and reverberation of flow in a closed chamber
S1 = closure of mitral and tricuspid valves at the beginning of isovolumetric contraction
S2 = Closure of aortic and pulmonic valves at the beginning of isovolumetric relaxation
S3 = inflow during diastole, oscillation of blood in ventricles
S4 = vibration of ventricular wall during atrial systole/contraction
Sympathetic activation of adrenals stimulates the release of EPI and NE
Split is 80-20, in favour of EPI
EPI acts on B2 adrenergic receptors
B2 adrenergic receptors are located in arteries
B2 adrenergic receptors activate the cAMP pathway, inhibits MLCK and causes dilation
Neurohumoral signaling for blood flow regulation steps?
Ang II and ADH cause constriction
Target = VSM
Systemic response - helps maintain blood pressure
Why does going from rest -> heavy aerobic exercise affect cardiac output, renal and skeletal blood flow?
The muscles start working which means is needs more O2 and uses more CO2 so the heart pumps O2 out quicker & CO2 in quicker causing the increase in Q
fight vs flight causes NE to act on the heart which increases heart size
Skeletal needs more O2 delivery, constrict all arteries that supply kidneys but dilate muscle arteries, a lot of ACh being released at neuromuscular junctions
Renal = decreases - so less blood goes to the kidneys since blood does not need to be filtered during exercise, constriction of blood vessels