Lecture 10 - Heart Flashcards
What are the 3 layers of the heart from superior to deep?
- pericardium
- myocardium
- endocardium
What are the layers of the pericardium? (4)
-superior fibrous pericardium
-parietal layer
-pericardial cavity
-visceral layer
What are the functions of the pericardium?
-protects + anchors heart
-stops over-expending
-frictionless movement
What is the myocardium?
cardiac muscle forming the bulk of heart
What are the functions of the myocardium?
-support great vessel + valves
-direct AP
-fibrous skeleton of heart
What is the endocardium?
-inner myocardial surface
What are the functions of the endocardium?
-continuous w/ vessels leaving and entering the heart
-one cell
What are the vessels that return blood to the heart?
-superior/ inferior venae cavae (no O2) –> right atria
-left/right pulmonary veins (O2 full) –> left atria
What are the vessels that take blood away from the heart?
=ascending aorta <– left ventricle
-brachiocephalic
-left common carotid
-subclavian arteries
=pulmonary trunk <– right ventricle
-left/ right pulmonary artery (no O2)
What are the anterior vessels that supply the exterior of the heart?
-right coronary artery
-marginal artery
-left coronary artery
-circumflex artery
-left anterior descending/ intraventricular
What are the anterior vessels that drain the exterior of the heart?
-anterior cardiac vein
-small cardiac vein
-great cardiac vein
Draw out the heart from the front view
-have fun look up photo
What are the posterior vessels that supply the exterior of the heart?
-left circumflex artery
-right coronary artery
-posterior intraventricular artery
What are the posterior vessels that drain the exterior of the heart?
-posterior cardiac vein
-middle cardiac vein
-small cardiac vein
-coronary sinus
Draw out the heart from the back view
-have fun
What are the atrial walls made of?
pectinate
What is the pulmonary circuit of the blood flow?
- right atrium
- tricuspid valve
- right ventricle
- pulmonary semi-lunar valves
- pulmonary trunk to arteries
- lungs
What is the systemic circuit of blood flow?
- pulmonary veins
- left atrium
- bicuspid valves
- left ventricle
- aortic semi-lunar valves
- aorta
- circulatory system
What is it called when there is a blockage in the heart?
myocardial infarction
What is the solution to myocardial infarction?
=anastomosis
-provide alternative routes given an artery gets blocked
-deliver blood
-useless when ventricles work
Where does the coronary sinus empty into?
right atrium
What is the anatomy of the heart valves?
-draw
-atrioventricular valve (AV) (tricuspid/mitral)
-chordae tendinae
-papillary muscles
Cardiac vs skeletal?
-form
-short/fat
-lay cylindrical
How is cardiac muscle interconnected?
intercalated disks
= flow ions
=desmosomes and gap junctions
Cardiac vs skeletal?
-nuclei
-1/2 nuclei
-multinuclei
Cardiac vs skeletal?
-interconnected
-intercalated disks
-motor unit grouping
Cardiac vs skeletal?
-cell to cell influence
-automaticity
-independence
Cardiac vs skeletal?
-mitochondrion
-20-40%
-2-5%
Cardiac vs skeletal?
-Ca2+ distribution
-low t-tubule, simple
-many t-tubule, elaborate
Cardiac vs skeletal?
-sarcoplasmic reticulum
-less developed
-complex
Cardiac vs skeletal?
-energy consumption
-aerobic
-anaerobic
What would happen if the cardiac muscles had a long absolute refractory period?
-tetanic contractions = stop heart pumping
What is the 3 step cardiac depolarization?
-draw
- Na+ influx
- Ca2+ influx
- K+ influx
-drawing = look at notes
What is considered the pacemaker of the heart?
sinoatrial node
-fastest
-located at the top right atrium
What are the 5 steps of action potential generation of the heart?
- sinoatrial node
- atrioventricular node
- bundle of His
- right & left bundles
- Purjinki fibres
Draw out and label the 6 parts of the cardiac pacemaker potential
- slow Na+ open
- Ca2+ open
- Ca2+ close & K+ open
- permeability change
- pacemaker potential
- action potential
-drawing = look at notes
What is the parasympathetic innervation of the heart?
-decrease depolarization
-K+ more permeable
-diastolic potential more negative
What is the sympathetic innervation of the heart?
-increase depolarization and repolarization
What are the 2 cardiovascular centres of the medulla oblongata?
-pathway
-function
=cardioacceleratory
-motor nerves to the heart
-increase rate and force of the heartbeat (nodes + muscle)
=cardioinhibitory
-dorsal vagal nucleus medulla
-inhibit impulse from vagus (nodes)
What is an ECG?
-what do?
=electrocardiogram
-records electrical changes during heart activity
What does an ECG look like?
-name the parts
-what does each part indicate?
-p-wave = atrial depolarization
-QRS complex = ventricular depolarization
-t-wave = ventricular repolarization
(image in notes)
What can be identified in the S-T segment?
myocardial ischemia (blockage of coronary artery)
What can be identified in the Q-T interval?
ventricular arrhythmia (twitch instead of pump)
How many standard limb leads are there?
-what does the diagram look like?
12
-in notes
What does systole indicate?
action of pumping out (contracting)
What does a diastole indicate?
action of filling in (relax)
What comes first the systole or diastole?
atrial systole then diastole, ventricular systole then diastole
What are the steps during ventricular diastole: mid to late diastole? (7 steps)
-pressure atria > pressure ventricle
-AV valve open, SL valve closed
-80% ventricular filling, AV start close
-P wave = atrial systole
-atrial pressure increase
-20% of blood enters the ventricles (EDV)
-atrial diastole
What diagnostic can be determined at the QRS complex?
-if big = hypertrophy
What does the ECG look like for sinus rhythm?
-draw
-normal consistent ECG
(image in notes p.53)
What does the ECG look like for ventricular fibrillation?
-draw
-inconsistent, different sized and close waves with no structure
(image in notes p.53)
What does the ECG look like for a 2nd-degree heart block?
-draw
-distanced repetition, very large but thin QRS
(image in notes p.53)
What does the ECG look like for a nonfunction SA node?
-draw
-super small waves, inconsistent separation
(image in notes, p.53)
What are the steps that occur during ventricular systole? (6)
-QRS complex and T-wave
-ventricles contract
-AV valves close
-isovolumetric contraction
-SL valves open
-ventricular ejection
What are the steps to isovolumetric relaxation? (5)
-early diastole
-ventricles relax
-pressure decreases
-backflow = SL valves close (dicrotic notch)
-ESV
What are the steps to return to the beginning of the cardiac cycle? (4)
-atria diastole
-pressure atria > pressure ventricles
-AV valves open
-restarts
What are the 4 phases of the cardiac cycle?
- ventricular diastole
- ventricular systole
- isovolumetric relaxation
- back to 1
How long is each cardiac cycle?
0.8 secs
How long is each atrial systole?
0.1 sec
How long is each ventricular systole?
0.3 sec
How long is the quiescent period?
0.4 sec
State the 2 driving forces of the cardiac cycle.
-blood flow controlled by pressure changes
-blood flow from high to low pressure through any openings
What is it called when the resting heart rate is over 100bpm?
tachycardia
What is it called when the resting heart rate is under 60bpm?
bradycardia
What is the first heart sound?
closure of AV valves = start ventricular systole
What is the second heart sound?
closure of SL valves = end ventricular systole
What are 3 reasons for heart murmurs + sound?
-valve obstruction -> high pitch
-valve insufficiency -> sound when not supposed to
-pulmonary valve stenosis -> turbulent and noisy
What is the equation for cardiac output?
CO = SV(EDV-ESV) x HR
CO - cardiac output
SV - stroke volume
EDV - end diastolic volume
ESV - end systolic volume
HR - heart rate
What is cardiac output meaning?
amount of blood pumped from left ventricle into aorta per minute
What is the average CO for a healthy male?
5L/min
How does CO change?
-fit person
-well-trained marathon runner
-4-5 times higher
-7 times higher
What is the cardiac reserve?
-the difference between at rest and when really pushed
What are the 4 ways heart rate is determined?
-autonomic fibres (symp=NE & para=Ach)
-circulating hormones (Epinephrine)
-plasma electrolytes (Ca2+/Na+ & K+/H+)
-body temp (hot & cold)
(increase & decrease)
What are the resting conditions of the heart rate?
-parasympathetic NS is dominant
Why does tachycardia lead to reduced CO?
-not adequate filling = EDV goes down
What is the Frank-Starling Law of the Heart?
-preload (heart will pump whatever volume of blood it receives)
-afterload (pressure ventricles must overcome to force open valves and eject blood)
What are the preload details?
-wide range
-EDV proportional to SV
-ventricles beat-to-beat independent by FS mechanism
-ventricles pump same amount over time
What are the afterload details?
-healthy = 80mm in aorta, 10mm pulmonary trunk
-hypertension = increased ESV and SV because hard to push out
State 2 types of extrinsic influences on stroke volume.
- contractability
- Ca2+ influx
I. sympathetic stimulation
II. drugs (digoxin)
III. parasympathetic NS
How to increase stroke volume?
=increase EDV
-increase venous return (exercise & decrease HR)
=decrease ESV
-increase contractibility (epinephrine, thyroxine, Ca2+)
How to increase heart rate?
=increase sympathetic
=decrease parasympathetic
-exercise, fright, anxiety
