cardio Flashcards
The cardiovascular system transports materials throughout the body
– From external environment: nutrients, water, and gases
– Materials between cells: hormones, immune cells, antibodies
Waste eliminated by cells:
- CO2, heat, metabolic waste
blood vessels
- arteries: away from heart. mainly oxygenated
- veins: towards the heart. mainly deoxygenated
- capillaries
- portal system joins two capillary beds in series
heart
– Septum divides heart into two halves (left and right)
– Atrium receives blood returning to heart
– Ventricle pumps blood out of heart
blood
cells and plasma
pulmonary arteries
- only artery that carries deoxygenated blood
- carries blood from heart to lungs
pulmonary veins
- carries oxygenated blood from lungs to left atrium
aorta
- biggest artery
- highest pressure
- lot of force and pressure bc it is right next to the heart
inferior and superior vena cava
- inferior = below
- superior = above
- attach to right atrium
pulmonary circuit
- right side of the heart
- pump blood to lungs
- deoxygenated
systemic circuit
- left side of heart
- pump blood to the rest of the body
- oxygenated
4 chambers of the heart
- 2 atrium – pump blood to ventricles
- thin walled upper chambers
- 2 ventricles
- thick walled lower chambers
atrioventricular valves
– Between atria and ventricles
– Chordae tendineae prevent eversion during ventricular contraction
▪ Attached to valve flaps from papillary muscles
– Tricuspid valve on the right side
– Bicuspid valve (mitral valve), on the left side
semilunar valves
– Between ventricles and arteries
– Aortic valve
– Pulmonary valve
The coronary circulation supplies blood to the heart
- Coronary arteries: carry oxygen
- Coronary veins: carry deoxygenated
pericardium
- CT sac that surrounds the heart
pericardial fluid
- pericardium sits in this
How blood travels
– Aorta and pulmonary trunk carry blood from heart
– Vena cava and pulmonary veins return blood to heart
– Deoxygenated: vena cava → right atrium → right ventricle → pulmonary trunk
– Oxygenated: pulmonary veins → left atrium → left ventricle → aorta
autorhythmic cells (pacemakers)
– Signal for contraction
– Smaller and fewer contractile fibers compared to contractile cells
– Do not have organized sarcomeres
- function without the CNS
- generate own action potentials
contractile cells
– Striated fibers organized into sarcomeres
- actual myocardial cells that actually contract as the action potential moves thru the intercalated disks
cardiac muscle
- Smaller and have single nucleus per fiber
- Branch and join neighboring cells through intercalated disks
- Gap junctions
- T-tubules are larger and branch
- Sarcoplasmic reticulum is smaller
- Mitochondria occupy one-third of cell volume – more in cardiac bc we need more ATP. heart never gets tired –> needs constant ATP
Waves of the ECG
– Three waves
▪ P wave: depolarization (contraction) of the atria – always from SA node
▪ QRS complex: wave of ventricular depolarization (contraction)
- more force from ventricles bc we have to push blood farther
–Atrial repolarization (relaxation) is part of QRS (can’t see this bc of the magnitude of the QRS
▪ T wave: repolarization (relaxation) of the ventricle
– Two segments
▪ P-R segment: AV nodal delay – time AV node is holding on to action potential (contraction)
▪ S-T segment: ventricular and atrial relaxation
- higher = heart attack and lower = HAD a heart attack
electrical events of the cardiac cycle
- Mechanical events lag behind electrical events: contraction follows action potential
- ECG begins with atrial depolarization, atrial contraction at the end of P wave
- P-R segment electrical signal goes through AV node and AV bundle
- Q wave end: ventricular contraction begins and continues through T wave
conducting system of the heart – how action potentials spread thru cardiac muscles
- SA node fires action potential and atria depolarizes (contracts)
- Electrical signal goes to AV node
- AV holds on to action potential (slows down conduction)
- Once it knows blood is all out of the atria, AV node sends off the action potential thru bundle of his to contract ventricles
purkinje fibers
- transmit electric signals down the atrioventricular bundle (AV bundle or bundle of His) to left and right bundle branches.
SA node, AV node, Purkinje fibers
- SA node sets the pace of the heartbeat at 70 bpm
– AV node (50 bpm) and Purkinje fibers (25–40 bpm) can act as pacemakers under some conditions
– AV node delay with slower conductional signals through nodal cells
what do electrical signals coordinate?
- contraction
Internodal pathway from sinoatrial node (SA node) to atrioventricular node (AV node)
– Routes the direction of electrical signals so the heart contracts from apex to base
SA node
- depolarization begins here
- autorhythmic cells in the right atrium that serve as the main pacemaker of the heart
AV node
- group of autorhythmic cells near the floor of the right atrium
- connected to SA node by internodal pathway
left and right bundle branches
- continue downward to the apex of the heart, where they divide into smaller Purkinje fibers that spread outward among the contractile cells.
apex
- heart angles down to the body while the broader base lies just behind the breastbone or sternum
base
- top of heart
septum
- heart muscle btw ventricles to keep them separate
thoracic cavity
- behind sternum and protected by ribs –> above diaphragm
- heart is on the ventral side of the thoracic cavity
- contains hearts and lungs
- heart is sandwiched btw the lungs
3 layers of the heart
- epicardium: outer layer
- myocardium: cardiac muscle
- endocardium: inner lining
stroke volume
- SV = EDV-ESV –> volume of blood before contraction minus volume of blood after contraction
- amount of blood ejected with each contraction (stroke) –> average = 70 mL
cardiac output
- the amount of blood pumped out of the heart each minuted (CO = HR x SV)
- Normal adult CO = 5 L/min
Ejection Fraction
- percentage of blood volume (EDV) ejected from ventricles per stroke
- normal = 60-70% of volume –> ventricles pump out this much blood
- less than 40% indicates significant impairment
Cardiac Entry is a Feature of Cardiac EC Coupling
- Action potential starts with the heart pacemaker cells
- Ca2+ induced Ca2+ release
– Voltage-gated L-type Ca2+ channels in the cell membrane open
– Ryanodine receptors (RyR) open in the sarcoplasmic reticulum (SR) open in response to inflow of
▪ Called spark Ca2+
– Summed sparks Ca2+ create a signal - Calcium binds to troponin
- Crossbridge cycle as in skeletal muscle
- Relaxation calcium removed from cytoplasm
– Into the SR with Ca2+-ATPase
– Out of cell through the Na+-Ca2+ exchanger (NCX)
Explain how cardiac muscles contract
- electrical signal thru the action potential contracts the heart cells thru the intercalated disks
tetanus
- sustained heart contraction
how are action potentials in cardiac muscle and pacemaker cells different than action potentials in neurons?
- neurons = get action potentials from brain
- cardiac = generate own action potentials thru pacemaker cells
understand why a longer action potential is required for a cardiac muscle cell
- longer bc of Ca2+ inflow
- Ca2+ keeps it at a higher membrane potential (more positive)
- need longer muscle contraction so we don’t get into tetanus
- tetanus: constant state of contraction. heart beat would overlap and there would be no rest period
diastole
- cardiac muscle relaxes
- pressure of ventricles produce when they relax
systole
- cardiac muscle contracts
- pressure of ventricles produce when they contract
phase 1 of cardiac cycle
- The heart at rest: atrial and ventricular diastole
▪ The atria are filling with blood from the vein bc its relaxed
▪ AV valves open –> ventricles fill
phase 2 of cardiac cycle
- Completion of ventricular filling: atrial systole
▪ Atria contract
▪ Last 20% of blood volume driven to ventricles
▪ End-diastolic volume (EDV): volume in ventricle at the end of ventricular relaxation
phase 3 of cardiac cycle
- Early ventricular contraction and the first heart sound
▪ AV valves close
–Vibrations following closure of the AV valves
–“Lub” (closure of AV valves)
▪ No blood in or out (isovolumic ventricular contraction)
▪ Increasing pressure due to ventricular muscle contraction
▪ Concurrent atrial diastole
–Atria relax and blood flows in the atria
phase 4 of cardiac cycle
▪ Semilunar valves open (aortic (goes into aorta) and pulmonic (pulm artery))
▪ Blood is ejected into arteries
▪ End-systolic volume (ESV): volume in ventricle at the end of ventricular contraction
phase 5 of cardiac cycle
- Ventricular relaxation and the second heart sound
▪ Arterial blood flows back towards heart
–Semilunar valves shut –> second heart sound
–“Dup”
▪ Ventricular muscles relax pressure drops (still higher than atrial pressure)
▪ No blood enters or exits (isovolumic ventricular relaxation)
▪ AV valves open when ventricular pressure drops below atrial pressure
how many cardiac cycles does a pressure-volume curve represent?
- one
preload
- degree of stretch
afterload
- combined load of EDV and arterial resistance during ventricular contraction
contractility
- intrinsic ability of a cardiac muscle fiber to contract at any given fiber
heart rate
- time btw two P waves and two Q waves
- parasym = decreases it via vagus nerve
- symp = increases it
