Ch. 8 Homeostasis of Gas Concentrations and Heart Rate Flashcards
What is the formula for cardiac input
HR x stroke volume
What does b.p depend on (2)
o cardiac output- as cardiac output increases, blood pressure increases
o diameter of blood vessels- constriction of blood vessels increases pressure and dilation decreases blood pressure
Six steps of heart contraction
- SA send impulse that spreads over both atria
- Atrium contracts
- Stimulus reaches AV node
- AV node sends out own impulse> travels down fibres in septum
- Impulse spread through ventricles
- Ventricles contract
What system influences heart rate
- Influenced by ANS
Explain the cardiac regulating systems role in influencing heart rate
o Medulla Oblongata sends impulse through network of cells (that have axons in heart and blood vessel walls)= cardiac regulating centre
o Reaches para/sympathetic neurons that carry impulses to the SA and AV
what is the difference of the two ANS nerves in heart rate
- Sympathetic= noradrenalin > increase heart rate and stroke volume
- Parasympathetic= acetylcholine > decrease rate and strength of contractions
at rest and during activity, which systems are dominant
o At rest: parasympathetic dominant
o Active: sympathetic dominant
What acts on cardiac centre
Sensory impulses from receptors in cardiovascular system
- Some receptors = chemoreceptors in aortic and carotid bodies and in medulla oblongata
during exercise, what response is brought on and what does it do
- Anticipatory response (brought about by ANS)> release adrenaline>
o Diameter of blood vessel change, h.r. + stroke volume increase
Explain glucose, breathing and heart rate effect of long distance race
o mental stress= blood glucose rise
o in anticipating of increased muscle activity= h.r. + b.p. increase
- race begins=
o breathing rate + depth increase
o cardiac output increase
o blood glucose= high level
o increase blood supply to skeletal (not to internal)
What muscles cause air to move in and out and what stimulates each
- Diaphragm= stimulated by phrenic nerve
2. Intercostal muscles= stimulated by intercostal nerves
what occurs if theres an injury to phrenic or intercostal nerves
- origin at spinal cord at level of neck and thorax
o If injury to this region= complete paralysis in muscles that ventilate lungs
does oxygen have a large role in regulation of breathing
no requires low levels for major effect
What two receptors detect changes in oxygen levels
o Peripheral chemoreceptors (= groups of cells within walls of carotid and aortic arteries) = aortic and carotid bodies
o Central chemoreceptors (in medulla oblongata)
Explain process when decrease in oxygen levels
- Large decrease in [O2] stimulates central chemoreceptors >
- Nerve impulses transmitted to respiratory centre >
- Stimulate transmission of messages to diaphragm + intercostal muscles
- rate of breathing
Explain process when increase in co2 levels
- Increase in both chemicals [ ]> stimulate central and peripheral chemoreceptors
- Nerve impulse transmitted to respiratory centre
- Increased breathing rate
what is the two responses of co2
- Longer response (takes several minutes):
o Most sensitive chemoreceptors= medulla oblongata - Immediate response:
o Stimulation of aortic and carotid bodies
o Associated with hydrogen ion concentration
what occurs when H content increases
ph decreases, breathing rate increases
what does a decrease in pH stimulate
o chemoreceptors in aortic and carotid > transmit impulse to respiratory centre= breathing rate
how are humans able to control breathing rate
o voluntary control via connections from cerebral cortex to descending tracts in spinal chord
o voluntary control // bypass respiratory centre
♣ protective device as enables to prevent irritating gases + water from entering lungs
why can’t we stop breathing forever
o build-up of CO2 in blood stimulates inspiratory centre to send impulses to inspiratory muscles
what is hyperventilating
extremely rapid or deep breathing; may result in dizziness and even fainting due to the loss of carbon dioxide from the blood
what can cause hyperventilation
voluntarily, or physical stress or emotional pain
why does hyperventilation correct itself
o usually corrects itself as [O2] means chemoreceptors not stimulated // no urge to breathe until CO2 normal
