Cardiac Conduction System Flashcards
What is the systole?
Contraction phase
What is the diastole?
Relaxation phase
What does the sinotrial node do?
It is the pace maker
- Creates an impulse
- Creates atrial systole
How does the Cardiac Conduction System work?
- Sinotrial Node (SAN) creates an impulse which creates atrial systole
- Impulse reaches Atrioventricular Node (AVN) (0.1-0.2s)
- Impulse sent down bundle of HIS
- Goes to Purkinje Fibres which causes ventricular systole
What does the AVN node do?
Atrioventricular Node (AVN) holds the impulse from thee SAN for 0.1s-0.2s then releases the impulse into the bundle of HIS
What does the bundle of HIS do?
Spreads out the impulse released from the AVN into the Purkinje Fibres
What do the Purkinje Fibres do?
Causes the ventricles to contract (ventricular systole)
What is the mnemonic for the Cardiac Conduction System? SAABPV
Sally Always Aims Balls Past Vicky
- SAN
- Atrial Systole
- AVN
- Bundle of HIS
- Purkinje Fibres
- Ventricular Systole
What is the Sympathetic System?
A part of the autonomic nervous system that speeds up heart rate
What is the Parasympathetic System?
A part of the autonomic nervous system that decreases heart rate
What are Chemoreceptors?
Tiny structures in the carotid arteries and aortic arch that detect changes in blood acidity causes by an increase or decrease in the concentration of carbon dioxide.
Increased concentration of carbon dioxide will stimulate the sympathetic nervous system, causing heart to beat faster.
What are Baroreceptors?
Special sensors in tissues in the aortic arch, carotid sinus, heart and pulmonary vessels that respond to changes in blood pressure to either increase or decrease heart rate.
What are Proprioceptors?
Sensory nerve endings in the muscles, tendons and joints that detect changes in muscle movement.
At start of exercise they detect an increase in muscle movement which sends an impulse through the sympathetic nervous system to the SAN to increase heart rate.
What is Myoglobin?
An iron-containing muscle pigment in slow-twitch muscle fibres which has a higher affinity for oxygen than haemoglobin.
It stores the oxygen in muscle fibres which can be used quickly when exercise begins.
What is Haemoglobin?
An iron-contains pigment found in red blood cells, which combines with oxygen to form oxyhemoglobin.
Red blood cells carry oxygen to the areas needed in the body.
What is systolic pressure?
The pressure in the arteries when the ventricles are contracting.
What is blood pressure?
The force entered by the blood against the blood vessel wall
Blood flow x resistance
What is diastolic pressure?
The pressure in the arteries when the ventricles are relaxing
Chemoreceptors simplified
• Chemoreceptors
• Increase in CO2
• Increase in heart rate
Baroreceptors simplified
• Baroreceptors
• Increase in blood pressure
• Decrease in heart rate
Proprioceptors simplified
• Proprioceptors
• Increase in muscle movement
• Increase in heart rate
What is Adrenaline?
A stress hormone that is released by the sympathetic nerves and cardiac nerve during exercise which causes an increase in heart rate.
What is Stroke Volume?
The volume of blood pumped out by the heart ventricles in each contraction
What is the diastole phase?
When the heart relaxes to fill with blood
What is the ejection fraction?
The percentage of blood pumped out by the left ventricle per beat
Starlings Law simplified
• Increased venous return
• Greater diastolic filling of the heart
• Cardiac muscle stretched
• More force of contraction
• Increased ejection fraction
Starlings Law
The greater the venous return the greater the subsequent force of contraction
What is the Bohr Shift
When an increase in blood carbon dioxide and a decrease in pH results in a reduction of the affinity of haemoglobin for oxygen.
Additional oxygen release from haemoglobin at lower blood pH.
What 3 factors are responsible for the increase in dissociation of oxygen from haemoglobin?
• Increase in blood temperature
- Higher temperature = readily dissociation
• Partial Pressure of carbon dioxide increase
- Oxygen dissociates faster
• pH
Venous Return Definition
The return of blood to the right side of the heart via the vena cava
Cardiac Conduction System definition
The conduction system involves the electrical impulses that cause the cardiac cycle of the heart. The cardiac muscle is myogenic, meaning it generates its own impulses.
