Control of Breathing and Heart Rate Flashcards
What muscular changes occur when we inhale?
Outer intercostal muscles contract
Diaphragm contracts
Thorax volume increases
Lung pressure decreases
= air is drawn into the lungs
What muscular changes occur when we exhale?
Outer intercostal muscles relax
Diaphragm relaxes
Internal intercostal muscles contract
Thorax volume decreases
Pressure of lungs increases
= air leaves lungs
Where is the ventilation centre found?
Un the medulla oblongata of the brain
What happens to control breathing in and out?
Breathing in
Impulse travels from inhilation centre —> motor neurone —> lungs
- causes outer intercostal muscles + diaphragm to contract
- activates stretch receptors when air drawn in; sends impulse back to ventilation centre to tell it to exhale
Breathing out
- inhilation centre is inhibited, exhalation centre activated
- causes outer intercostal muscles + diaphragm to relax
- stretch receptors now inactive; no signal sent to inhibit inhilation centre so cycle restarts
How is blood pH controlled during respiration?
Respiration produces CO2 and lactic acid
- CO2 dissolves into blood plasma to produce carbonic acid
- lowers pH
- drop in pH detected by chemoreceptors in the medulla
- impulses are sent to the lungs, increasing rate and depth of breathing
- more oxygen breaks down lactic acid into pyruvate
- more CO2 taken to the lungs to diffuse out as conc gradient is maintained
What is tidal volume?
The volume of air we breathe in and out (~ 0.5dm^3 at rest)
What is vital capacity?
Maximum volume of air we can inhale and exhale
What is minute ventilation and how is this calculated ?
Volume of air taken into lungs in 1 minute
= tidal volume x no of breaths
Define cardiac output and how this is calculated?
Volume of blood pumped by the heart in one minute
= stroke volume x heart rate
What is stroke volume?
Volume of blood pumped out of L ventricle each time it contracts
What controls the cardiac output ?
Cardiovascular control centre in medulla
Which nerves control heart rate?
Sympathetic nerve increases heart rate (sympathetic NS)
Vagus nerve decreases heart rate (parasympathetic NS)
What changes does adrenaline cause?
Binds to receptors on target organs
- including SAN, which increases heart rate to prepare body for physical demands
Dilates arterioles supplying skeletal muscle and constricts arterioles supplying digestive system + non-essential organs —> maximises blood flow to active muscles
How is the heart controlled during high levels of exercise?
- increased respiration = more CO2 + lactic acid
- blood pH drops, detected by chemoreceptors in medulla
- nervous impulses sent to cardiac control centre
- sent down sympathetic NS to SAN, secreting noradrenaline
- SAN fires more impulses across heart
= so HR increases
How is the heart controlled during low levels of exercise?
- decreased respiration = less CO2 + lactic acid
- blood pH increases
- nervous impulse sent to cardiac control centre
- nerve impulse sent down parasympathetic NS to SAN, secreting acetylcholine
- SAN fires less impulses across heart
- heart rate decreases
