Cardiovascular System Flashcards
Heart Chamber Types
Atrias
Ventricles
Atria
blood reservoir, primer pumps
Ventricles
main force for blood movement through body
RIGHT SIDE
to lungs
pulmonary circuit
LEFT SIDE
to body
systemic circuit
trace BF thru heart
- inferior and superior vena cavae
- right atrium
- tricupsid valve
- right ventricle
- pulmonary semilunar valve
- pulmonary arteries
- lungs
- pulmonary veins
- left atrium
- bicupsid valve
- left ventricle
- aortic semilunar valve
- aorta
3 heart wall layers
- epicardium
- myocardium
- endocardium
epicardium
outer connective tissue
myocardium
middle muscular layer
endocardium
inner, endothelium overlaying a think connective layer
septum
muscular wall separating L and R halves of heart
pericardium
triple layer bad that surrounds and protects heart
purpose of Heart Valves
prevent back flow of blood, ensuring one-way blood flow
Heart Valves open/close passively
open and close passively with pressure of blood against them
AV Valves
- thin walls
- open when pressure in atria higher than in ventricles
- close with retrograde pressure of blood against valves
Purpose of Chorea Tendinae and Papillary Muscles
-chordae tendon attach to pointed ends of cusps, which are attached to papillary muscles (arise from ventricles). when ventricles contract, papillary muscles contract, pulling down on cusps, preventing AV valves from reopening during ventricular contraction and causing leakage of blood into atria
SV valves
- thicker walls
- open when ventricular pressure exceed arterial pressures
- close as blood flows backward and fills cusps
- no chordae tendon or papillary muscles
3 classes of tissue in Myocardium
- Atrial Contractile
- Ventricular Contractile
- Specialized Conductive
Specialized Conductive
little contractile ability ; rhythmicity and varying confection rates
Tissue in myocardium
- striated
- sacromeres
- crossbridge cycle
Synctical Arrangement in Myocardium
Intercalated Disks
- Gap Junctions
- Desosomes
Gap Junctions
diffusion of ions between fibers with very little electrical response
Desosomes
adhering junctions
Major importance of synctical arrangement
that 1 impulse spreads to all fibers in synctium
2 synctia
Atrial and Ventricular
-except for small bundle of specialized its, atria and ventricles separated by fibrous tisue
Autoconduction
create own AP
- no need for innervation
- no fiver type diffs- similar to ST
- all fibers highly oxidative
Autoconduction + Syncytical Arrangement
Autorhythmicity
What allows us to Autoconduct
- Pacemaker potentials and funny currents
- As the membrane depolarized from previous AP, increase negativity causes opening of Na+ channels, depolarizing membrane toward TP
- most conductive fivers can auto conduct
- fibers leakiest to Na+ depolarize fastest setting pace for entire heart
What accounts for plateau in AP
- opening of L (long-lasting) type Ca++ channels
- -prolongedentry of Ca++
- low membrane permeability to K+
- -K+ flows out more slowly
- delays repolarization
refractory periods-significance
- ventricular absolute refractory period is 0.25-0.3 seconds prevent tetany
- atrial refractory periods-0.15 seconds
- -possible for atrial rate to be faster than ventricular rate
Ca++ and contractive force
- high extracellular Ca++ levels enhance contraction
- low extracellular Ca++ levels inhibit contraction
SA Node
- greatest Na+ permeability
- sinus rhythm
- pacemaker
- AP travels outward from SA node in wave-like fashion throughout atria
- interatrial band
- anterior, middle, posterior internal tracts
AV Node
- conducts impulse from atria to ventricles
- bundle of HIS
- bundle branches
- purkinje fibers
Pause duration and purposes of AV Node
delays delivery of signal to ventricles by 0.1 second, allowing time for ventricular filling and AV valve closure
Purpose of specialized ventricular conduction system
-net effect of specialized ventricular conduction system is to allow simultaneous contraction of all parts of the ventricles (6x normal ventricular fiber conduction speed)
Chronotropic Regulation
affects heart rate
Inotropic Regulation
affects contractive force
What greatly affects both chronotropic and isotropic regulation?
exercise.
Frank-Starling Mechanism
-increase in venous return–> increase stretch on cardiac fibers–>increase recoil open contraction–> increase contractive force
Autonomic Nervous System
SNS: Sympathetic Nervous System
PNS: Parasympathetic Nervous System
Sympathetic Nervous System
- Accelerator Nerve
- Physical and Emotional Stress
- NE: associated with increase Na+ and Ca++ permeability—>depolarizes membrane —-> increases Heart Rate
- increase Ca++ permeability—> increase contractive force
Parasympathetic Nervous System
- Vagus Nerve (CN X)
- Vagal Tone
- ACh- Associated with increase in K+ permeability–> hyper polarizes membrane —> decrease Heart Rate
- ACh reduces___ released into cytosol during the “Plateau Phase” of AP and increase the conductance of the Slow Potassium Channels shortening the “Plateau Phase” and hastening depolarization
- -weak compared to the capacity of PNS to modulate HR
Vagal Tone and Body Temperature
high Tb–> increase membrane permeability to Na+ and Ca++—> increase heart rate and contractive force
low Tb–> opposite effect
Vagal Tone and Proprioceptors
when movement detected-SNS stimulation
Vagal Tone and E/NE
- released due to SNS stimulation
- effects same as SNS
Vagal Tone and Baroreceptors
- stretch/pressure receptor in aorta and carotids
- –low BP—> SNS Stimulation
- –high BP—> PNS stimulation
Vagal Tone and Chemoreceptors
- sensitive to chemical concentrations in blood; located in aorta and carotids
- low O2, high CO2, and low pH (high H+)–> SNS stimulations
Diastole
phase of cardiac cycle when myocardium relaxed
Systole
phase of cardiac cycle when myocardium contracted
Atrial Diastole
- pressure in atria before contraction=0 mmhm
- 70% EDV enters passively from atria to ventricles
Atrial Systole
- last 30% filling
- primer pumps for ventricles
- preload: load to which a muscle is subjected before shortening
- closing AV valves end
Ventricular Diastole
- 1st 1/3 rapid filling - 70% EDV
- 2nd 1/3 little filling
- 3rd 1/3 atrial systole-last 30% EDV
- closing AV valves ends
- EDV (End Diastolic Volume) increase from rest to exercise
EDV
End Diastolic Volume
volume of blood in left ventricle at end of ventricular diastole
Ventricular Systole
- isovolumetric contraction
- 1st 1/3-70% of SV ejected
- afterload: the resistance against which left ventricle pumps
- isovolumetric relaxation
- ESV (end systolic volume) decrease from rest to exercise
Isovolumetric Contraction
when semilunar valves open, blood flows quickly and with high P into aorta and pulmonary arteries
ESV
End Systolic Volume
blood remanned in LV at the end of ventricular systole
SV
stroke volume
volume of blood pumped from LV
SV=EDV-ESV
-increase from rest to exercise
EF
Ejection Fraction
proportion of blood pumped out of LV w/each beat
- EF=SV/EDV
- at rest, avg EF=60-70%
- exercise can increase EF to 80-90%
- unhealthy EF <30-40
Q
Cardiac Output
Q=HR*SV
Rest: Q=5 L/min
Exercise: increase Q to 25 L/min
