Topic 6 Flashcards
Where is the SAN
Wall of the right atrium
What is the SAN?
Like a pacemaker
Sets rhythm of heartbeat
Sends out regular waves of electrical activity to atrail walls
Role of non conducting collagen tissue
Prevents waves of electrical activity from being passedd directly from the atria to the ventricles
Where do waves of activity from SAN travel to?
AVN
What is the role of the bundle of His?
Conducting waves of electrical activity to finer muscle fibres in left / right ventricle walls
- purkyne fibres
What is the role of the purkyne fibres?
Carry waves of electrical activity into ventrical walls
Simultaneous contraction
From thw bottom up
What controls heart rate?
Medulla oblongata
How does medulla oblongata control heart rate?
Control rate at which SAN fires
What are baroreceptors and chemoreceptors?
Baroreceprors = pressure receptors Chemoreceptors = chemical receptors
Where are baroreceptors located?
What stimulates them?
- Aortic arch, carotid sinus
- stimulated by high and low blood
pressures
Where are chemoreceptors located?
What do they monitor?
- medulla oblongata Monitor - oxygen level in blood - carbon dioxide level - pH
How do action potentials from receptors reach CNS?
Action potentials from these receptors are sent to medulla oblongata along sensory neurones
What happens once impulse reaches medulla oblongata?
Information processed
Action potential sent to SAN along sympathetic / parasympathetic neurones
Neurotransmitters released onto SAN, determines wether heart rate speeds up / slows down
How does exercise trigger increase ini breathing rate?
Decreasing blood pH
What causes increase in pH during exercise?
Level of carbon dioxide increases
What detects change in pH?
Chemoreceptors
How do chemoreceptors detecting pH increase breathing rate?
Decrease in pH
Action potential to medulla oblongata
Medulla oblongata sends more frequent action potentials to intercostal muscles / diaphragm
Cardiac output equation
Cardiac output (cm3 min-1 = heart rate (bpm) x stroke volume (cm3)
