control of respiration

Question 1

control of breathing

Answer 1

average time for an adult to hold their breath is 30-60s
as the build up of blood acidifying CO2 than the lack of oxygen.

Question 3

lung perfusion

Answer 3

the blood supply from pulmonary and systemic circulation.
lots of alveoli to maximise oxygen exchange
they have thin walls and a large surface area for oxygen to diffuse into the bloodstream

Question 4

why is blood supply important

Answer 4

• maintaining blood pressure
• important for the network of capillaries surrounding the alveoli.

Question 5

distribution- carbon dioxide transport

Answer 5

CO2 carried from tissue to lungs
- diffusion from cell to blood across the alveolar membrane due to pressure gradient
- 24x more soluble than O2- no carrier

Question 6

gas transport- haemoglobin

Answer 6

binds 98% of 02 forming oxyhaemoglobin HbO2
binding of one molecule of O2 enables easier binding of subsequent molecules

Question 7

haemoglobin saturation

Answer 7

sigmoidal due to the nature of O2 binding to the Hb

Question 8

benefit of the sigmoidal shape

Answer 8

the amount of O2 in the blood is not affected by small fluctuations in the Po2 in lungs.

Question 9

effects of pH on oxygen saturations

Answer 9

the Bohr effect- the shift in the haemoglobin saturation curve resulting from pH change.
when there is a decrease in pH, oxygen decreases

Question 10

respiratory Quotient

Answer 10

the relationship between the amount of carbon dioxide produced and the oxygen that is absorbed
steady state alveolar ventilation= PCO2

Question 11

effect of 2,3- diphosphoglycerate (DPG)

Answer 11

metabolite of carbohydrate metabolism in erythrocytes
acts as inhibitor which binds to haemoglobin structure

Question 12

what controls respiration

Answer 12

central pattern (voluntary) and voluntary

Question 13

voluntary controlling respiration

Answer 13

cerebral cortex
additionally influences respiratory centre

Question 13

central pattern

Answer 13

inspiratory and expiratory muscles controlled by neurons in the medulla and fine tuned by Pons

Question 14

respiratory centre

Answer 14

integration of sensory information occurs in the Pons to fine tune signals. together they make the respiratory centre

Question 15

medulla oblongata control centres

Answer 15

dorsal respiratory group (DRG) and Ventral respiratory group (VRG)

Question 16

DRG

Answer 16

controls the diaphragm and external intercoastal muscles
involved in inspiration and expiration in quiet breathing.

Question 17

VRG

Answer 17

controls accessory inspiratory and expiratory muscles
involved in inspiration and expiration during forced breathing

Question 18

respiratory reflexes

Answer 18

changes to the basic rhythm of breathing brought about by chemoreceptors and baroreceptors

Question 19

chemoreceptors

Answer 19

respond to changes in Pco2, Po2 and [H+]
central and peripheral locations
most effective in altering ventilation

Question 20

baroreceptors

Answer 20

detect changes in blood pressure
located in carotid body and aortic arch

Question 21

ventilation- the chemistry

Answer 21

sit in the medulla. Ventrolateral surfaces respond to the CO2
and passes messages

Question 22

central chemoreceptors

Answer 22

located on the ventro -lateral surface of the medulla oblongata
monitor composition of cerebrospinal fluid
respond to only a rise in [H+] and pco2
stimulation increases depth and rate of respiration via stimulation of the DRG

Question 23

factors affecting chemoreceptors

Answer 23

• chronic CO2 retention reduces sensitivity of respiratory centre
• H+ also increased by non-respiratory causes such as diabetic ketoacidosis
• other factors affecting chemoreceptors- sleep, age and alcohol and drugs particularly aspirin

Question 24

diabetes causing problems with chemoreceptors

Answer 24

they can loose consciousness from it. reduction of oxygen pressure blow 8ka can become a stimulus for ventilation.

Question 25

peripheral chemoreceptors

Answer 25

located in carotid body and aortic arch- where there is a high blood flow.
- respond to low arterial Po2- HYPOXIA

Question 26

firing of peripheral chemoreceptors

Answer 26

switched on full power only when Po2 gets below 60mm Hg in oxygenated blood
- decreased Po2 not as powerful a stimulator of respiration as increased pco2
- main control is by central chemoreceptors in response to altered pH

Question 27

other stimulators of peripheral chemoreceptors

Answer 27

vascular stasis- decreased blood flow to carotid
cyanide- prevents O2 utilization at tissue level
nicotine- in sufficient amounts
exercise- due to increased [K+]

Question 28

baroreceptors

Answer 28

fibres in the carotid sinuses, aortic arch, atria and ventricles stimulated by increase blood pressure
impulses inhibit respiration via respiratory centre in medulla.