Heart & ECG Flashcards
What is the role of the heart?
- pumps blood through vessels to many organs
- blood transports O2 and nutrients and removes waste CO2
- performs sensory and endocrine functions which regulate variables in the heart such as blood volume and pressure
ULTIMATE ROLE - “to provide adequate blood flow to all of the organs and tissues of the body”
What is the role of the right atrium?
Removes blood from systemic circuit
systemic = bodily
What is the role of the right ventricle?
Pumps blood to pulmonary circuit
pulmonary = lungs
What is the role of the left atrium?
Receives blood from pulmonary circuit
pulmonary = lungs
What is the role of the left ventricle?
Pumps blood to systemic circuit
systemic = bodily
What are the role of the valves?
- Allows for uniderectionality.
- Maintains pressure in the heart
What is the septum?
muscle that separates the right and left atria.
Describe the route of blood through the heart.
- Deoxygenated blood enters the right atria through superior and inferior vena cava.
- Blood enters the right ventricle through the the atrio-ventricular valve into the right ventricle.
- Blood exits the right ventricle into the pulmonary artery though the semi lunar valve.
- Blood travels to the lungs where it becomes oxygenated and releases CO2.
- Blood travels from the lungs to the left atrium though the pulmonary vein.
- Blood travels from the left atria to the left ventricle through the atrioventricular valve.
- Blood travels from the left ventricle to the aorta through the semi lunar valve.
Define Myogenic
Signals itself- doesn’t require input from the brain
Define Autorhythmicity
Generates its own rhythm
What are Pacemaker cells
Spontaneously create action potentials.
Define Systole
The phase of the heartbeat when the heart muscle contracts and pumps blood from the chambers into the arteries.
Define Diastole
The phase of the heartbeat when the heart muscle relaxes and allows the chambers to fill with blood.
What are contractile cells
They are responsible for contraction of the heart muscle.
Where are pacemaker cells located?
Located in the SAN (found in the upper right atrium) And in the atrioventricular node (found near the tricuspid valve in inter-atrial septum)
What do conduction fibres do?
conduct the action potential through the myocardium. The action potential travels of speeds of 4m/s. Conduction fibres have low electrical resistance
What forms the conduction system of the heart
Pacemaker cells+ conduction fibres= conduction system of the heart
what is the passage of an action potential
pacemakers –> conduction fibres –> contractile cells, this is possible because all cardiac cells are connected by gap junctions, inside intercalated disks
what are desmosomes, where are these found?
protein fibres which form physical bonds between cells to resist mechanical stress. This enables myocardium to resist stretching, as occurs every time heart fills with blood
found inside Intercalated disks
Describe the Initiation and Conduction of an Impulse during a Heartbeat
1) Impulse initiated in SA node –> AV node via conduction fibres and through most of atrial muscle
2) AV node transmits AP less rapidly, therefore delayed by 0.1 seconds
3) AV node –> atrioventricular bundle (bundle of His) in interventricular septum
4) Signals split into left and right branches to ventricles
5) From the bundle branches, signals travel through a network of branches known as Purkinje fibres which spread through ventricular myocardium
Describe the electrical activity in pacemaker cells
- Pacemaker cells fire AP spontaneously - doesn’t have a steady resting potential.
- After AP, pacemaker cell immediately depolarises slowly until membrane potential reaches threshold, which triggers next AP.
- Slow depolarisations are known as pacemaker potentials
- Changes in membrane permeability to different ions.
Cardiac contractile cells -
- Responsible for the contraction of the heart.
- The depolarisation/repolarisation of these cells are different to the pacemaker cells.
What does an Electrocardiogram (ECG) record?
• “Records the spread of electrical current through the heart as a function of time through the cardiac cycle.”
What is Einthoven’s triangle
Equilateral triangle surrounding the heart.
Right arm, left arm and left leg.
Electrodes are connected to an oscilloscope.