The Heart Flashcards
What does the Vena Cava do?
It carries deoxygenated blood from the lungs to the left atrium.
What does the Aorta do?
It carries oxygenated from the lungs to the left atrium
What does the Pulmonary Vein do?
It carries deoxygenated blood to the lungs from right ventricle to lungs
What does the Pulmonary Artery do?
It carries oxygenated blood from the left ventricle to the rest of the body
What two systems is the nervous system split into?
The CNS (central nervous system) and the peripheral nervous system
What is the CNS made up of?
Brain and Spinal cord
What is the peripheral nervous system made up of?
The neurones (that connect the CNS to the rest of the body)
What two systems is the peripheral nervous system made up of?
Autonomic and Somatic nervous systems
What does the somatic nervous system control?
Conscious activities e.g. running
What does the autonomic nervous system control?
Unconscious activities e.g. digestion
What two systems is the autonomic nervous system split into?
The sympathetic and the parasympathetic nervous system
What does the sympathetic nervous system do?
It is the ‘fight or flight’ system that gets the body ready for action
What does the parasympathetic nervous system do?
It is the ‘rest and digest’ system that calms the body down.
The cardiac muscle is ‘myogenic’ - what does this mean?
The heart can contract and relax without receiving signals from nerves.
What is the sinoatrial node (SAN)?
A small mass of tissue in the wall of the right atrium
It is a natural pacemaker
How does the SAN act as a natural pacemaker?
sets the rhythym of the heartbeat by sending out regular waves of electrical activity to the atrial walls.
Give the mechanism of a heartbeat?
SAN sends signal to atrial walls - they both contract at the same time
The waves of electrical activity are transferred to AVN. (slight delay)
Then passed to bundle of His –> Purkyne tissue –> walls of left and right ventricle –> contract simultaneously (from bottom up)
What is the AVN?
Atrioventricular node which is reponsible for passing the waves of electrical activity onto the Bundle of His
Why is there a slight delay before the AVN reacts?
To ensure that the atria have emptied before the ventricles contract.
What is the bundle of His?
Group of muscle fibres
What does the bundle of His do?
It conducts the waves of electrical activity between the ventricles to the apex (bottom of heart)
What is the Purkyne tissue?
The bundle of His splits into finer muscle fibres in the left and right ventricle walls.
What does the Pyurkyne tissue do?
Carries the waves of electrical activity into the muscular walls of the right and left ventricle, causes them to contract simultaneously, from bottom up.
What prevents the wave of electrical activity from being passed directly from the atria to the ventricles?
A band of non-conducting collagen tissue
EXAM TIP - REMEMBER
There is a delay BEFORE the AVN reacts
NOT
that there is a delay in the wave of electrical activity reaching the AVN
Silly Ants Have Pants
San, Avn, bundle of His, Purkyne fibres
What does the medulla do?
Unconsciously controls the rate at which the SAN fires
Animals needs to alter their heart rate in order to…
respond to internal stimuli.
Give some internal stimuli which alters heart rate:
pH, CO2 conc, O2 conc, blood pressure
What are internal stimuli detected by?
Pressure receptors (baroreceptors)
Chemical receptors (chemoreceptors)
Where are baroreceptors found?
Aorta & Carotid artery
What stimulates baroreceptors?
High and low blood pressure
Where are chemoreceptors found?
Aorta, carotid artery and medulla
What do chemoreceptors do?
Monitor O2 levels, CO2 levels and pH levels in blood
Response to high blood pressure:
Baroreceptors – Sensory neurone – Medulla – PARASYMPATHETIC NEURONE – ACETYLCHOLINE – binds to receptors on SAN = hr slows, reduced blood pressure(bp) back to normal(btn)
Response to low blood pressue:
Baroreceptors – sensory neurone – medulla – sympathetic neurone – noradrenaline – binds to receptors on SAN =hr speed up, increases bp btn
What are acetylcholine and noradrenaline?
Neurotransmitters
Response to High O2, low CO2/ high pH
Chemoreceptors – Sensory neurone – Medulla – Parasympathetic neurone – Acetylcholine – receptors on SAN = hr slows down, O2,CO2,pH levels btn
Response to Low O2, high CO2 / low pH
Chemoreceptors – sensory neurone – medulla – sympathetic neurone – noradrenaline – receptors on SAN = hr speeds up, O2,CO2,pH levels btn
Structure the answer should follow: What happens when … high/low bp, high/low pH
Chemo/baroreceptors detect chemical changes/high or low bp
Sends impulses along sensory neurone to the medulla, which sends impulses along the (para)sympatheric neurones which secrete acteylcholine/noradrenaline. This binds to the receptors on the SAN which causes heart rate to inc/decrease and change to go back to normal.
EQ - Exercise causes an increase in heart rate - describe the role of receptors and of the nervous system in this process.
Chemoreceptors detect the rise in CO2/fall in pH / baroreceptros high bp
Send impulses to cardiac centre/medulla
More impulses to SAN
By sympathetic nervous system
Remember if O2 conc is high, pH is also high (which means CO2 is low) and…
If O2 conc is low, pH is also low (CO2 will be high)
How do valves (atrioventricular valves) maintain a unidirectional flow of blood?
Pressure in atrium is higher than in the ventricle causing the valve to open
Pressure in ventricle is higher than the pressure in the atrium causing valve to close.
When does a valve open?
When the pressure above the valve is higher than the pressure below the valve.
When does a valve close?
When the pressure below the valve is higher than the pressure above the valve.
