Control of breathing Central rhythm Lecture 13

Question 1

Describe the muscles used in breathing

Answer 1

Inspiration- diaphragm is the only major inspiratory muscle External muscles- scalene and sternocleomastoid muscle used in exercise, coughing and vomiting Expiration- passive diaphragm relaxation Internal muscles- abdominal and oblique muscle involved only in forced breathing

Question 2

Briefly describe central control of timing breathing and rhythm

Answer 2

PRG in the pons important for timing DRG and VRG in the medulla important for rhythm generation DRG- inspiratory neurones, in the nucleus tractus solitarius (NTS)- spontaneous activity synchronised with breathing VRG- inspiratory/expiratory motor neurones, activity in the DRG excites inspiratory neurones and inhibits expiratory neurones

Question 3

What causes inspiration during quiet breathing?

Answer 3

DRG- self-excitable neurones, repetitively generating action potentials to cause inspiration ➡️C spinal cord ➡️phrenic nerves ➡️diaphragm contracts ➡️inspiration

Question 4

What causes expiration?

Answer 4

Entirely passive DRG inactive➡️ diaphragm relaxes➡️ expiration

Question 5

What neural control causes forced breathing?

Answer 5

Inspiratory neurones in the VRG via the T spinal cord causes other inspiratory muscles to contract Expiratory neurones causes expiratory muscles to contract

Question 6

Describe the involvement of higher brain centres in respiration

Answer 6

Hypothalamus- temperature, fight/flight response Limbic system and cerebral cortex- emotion/pain Motor cortex- limb receptors, excercise

Question 7

Give a brief overview of CNS in respiratory control

Answer 7

Brainstem- automatic- metabolic Cortical- voluntary- behavioural