C3.1 - feedback control and peristalsis Flashcards
Where does sensory input for feedback control of ventilation come from?
Sensory input comes from chemo-receptors in the medulla, which monitor pH changes in the blood.
- Blood pH is regulated to stay within the narrow range of 7.35 to 7.45.
What is an example of causes of pH changes?
Causes of pH changes in the blood include exercise, which leads to increased ventilation rate and breath volume.
What determines heart rate at rest?
Pacemakers/Sinoatrial node
What is the function of a baroreceptors?
Baroreceptors monitor the blood pressure through ateriol distension.
- Found within the arterty walls
What is the function of chemoreceptors?
Chemoreceptors monitor blood pH and concentrations of oxygen and carbon dioxide.
- Found outside the blood vessels, monitoring blood in capillaries.
Where are receptors located?
These receptors are located in the aortic arch and branches of the carotid arteries.
What do the receptors initiate?
These baroreceptors and chemoreceptors initiate electrical impulses (action potentials) that move to the medulla.
What occurs to the heart rate during activity?
During activity, increases respiration rate requires additional oxygen and the removal of more carbon dioxide, which requires a higher heart rate and stroke volume.
What happens when when respiration rates increase?
- concentration of oxygen decreases
- concentration of carbon dioxide increases
- the pH decreases as carbon dioxide dissolves to form carbonic acid
What does the frequency of impulse depend on?
The frequency of impulse depends on the relative concentration of H+ detected.
What is the feedback control of ventilation rate?
1) Exercise increases the rate of cellular respiration.
2) This increases the production of carbon dioxide.
3) Carbon dioxide reacts with water to form carbonic acid, which dissociates to release H+, which decreases the pH of the blood.
4) Chemoreceptors in the aorta and carotid arteries detect this, and send impulses to the medulla.
- These receptors are also in the brain region itself.
5) The medulla sends impulses to the diaphragm and intercostal muscles, to increase contraction frequency.
6) This increases ventilation rate, maintaining the concentration gradients, causing faster diffusion in gas exchange.
How is sensory input co-ordinated through the medulla?
The medulla receives impulses from baroreceptors and chemoreceptors.
- It co-ordinates responses and sends nerve impulses to the heart to change the heart’s stroke volume and heart rate.
What is the response of the heart if respiration rate increases?
If the respiration rate increases, the medulla sends impulses through the sympathetic nerve to the pacemaker cells of the heart, accelerating the heart rate and increasing stroke volume.
What is the response of the heart when respiration rate decreases?
If the respiration rate decreases, the medulla sends impulses through the vagus nerve to the pacemakers cells of the heart, decelerating the heart rate and decreasing the stroke volume.
What is the response of the heart when blood pressure is too high?
If the blood pressure is too high, the medulla sends impulses to decrease the heart rate and stroke volume.
What is the response of the heart when blood pressure is too low?
If the blood pressure is too low, the medulla sends impulses to increase heart rate and stroke volume.
What is the role of the CNS in the digestive system?
Initiation of swallowing of food and egestion of faeces is under voluntary control by the central nervous system (CNS).
What is the role of the ENS in the digestive system?
Peristalsis occurs between the mouth and anus, through the alimentary canal, is under involuntary control by the enteric nervous system (ENS).
What is the importance of the ENS?
The action of the ENS ensures passage of material through the gut, from the lower oesophagus all the way to the rectum is coordinated.
What is the process of peristalsis?
1) Food moves through the alimentary canal in boluses.
2) The peristaltic reflex uses sensory, relay and motor neurons to move each food bolus along the alimentary canal.
What occurs behind a bolus?
Behind a bolus, motor neurons release excitatory neurotransmitters and cause contraction of the smooth muscle of the gut walls.
What occurs ahead of a bolus?
Ahead of a bolus, motor neurons release inhibitory neurotransmitters, which relax the smooth muscle and allow the bolus to slide through the widened lumen.
What is stroke volume?
Volume of blood expelled by the heart in one cardiac cycle.
