Physiology 6

Question 1

What is the major rhythmic generator?

Answer 1

Medulla

Question 2

Which neurones generate the breathing rhythm?

Answer 2

Pre-Boltzinger complex

-Located near upper end of medullary respiratory centre

Question 3

Sequence of events giving rise to inspiration?

Answer 3

• Rhythm= generated by Pre-boltzinger complex
• Excites doral resp group neurones
• Fire in bursts
• Firing leads to contraction of inspiratory muscles
• When firing stops=passive expiration

Question 4

What is the bucket handle mechanism?

Answer 4

External intercostal muscle contraction lifts the ribs and moves out the sternum

Question 5

Explain sequence of events in active inspiration during hyperventilation?

Answer 5

• Increased firing of dorsal neurones excites second group
• Ventral respiratory group neurones
• Excite internal intercostals abdominals = forceful expiration

Question 6

What can the rhythm generated in the medulla be modified by?

Answer 6

Neurones in the pons

Question 7

What is the PC and what does it do?

Answer 7

Pneumotaxic centre

• Stimulation of this terminates inspiration
• Stimulated when dorsal respiratory neurones fire
• Inspiration inhibited

Question 8

What happens without a PC?

Answer 8

Breathing is prolonged

Inspiratory gasps with brief expiration (Apneusis)

Question 9

What does apneustic centre do?

Answer 9

Impulses from these neurones excite inspiratory area of medulla and prolong inspiration

Question 10

Respiratory centres are influenced by stimuli received from?

Answer 10

• Higher brain centres (cerebral cortex, hypothalamus)
• Stretch receptors in walls of bronchi/ioles
• Juxtapulmonary receptors
• Joint receptors
• Baroreceptors

Question 11

What do central chemoreceptors and peripheral chemoreceptors relate to?

Answer 11

Chemical control of respiration

Question 12

Examples of involuntary modifications of breathing?

Answer 12

• Pulmonary stretch receptors (Hering bueler reflex)
• Joint receptors reflex in exercise
• Stimulation of respiratory centre by temperature, adrenaline or impulses from cerebral cortex
• Cough reflex

Question 13

Joint receptors modifying breathing?

Answer 13

Impulses from moving limbs reflexly increase breathing

-Probably contribute to increased ventilation during exercise

Question 14

What do peripheral chemoreceptors sense?

Answer 14

Tension of oxygen and CO2 and H+ in blood

Question 15

Where are central chemoreceptors situated?

Answer 15

Near the surface of the medulla of the brainstem

Question 16

What do central chemoreceptors respond to?

Answer 16

H+ of the cerebrospinal fluid

Question 17

Cerebrospinal fluid is more buffered than blood. True or false?

Answer 17

FALSE

-contains less blood and hence is less buffered

Question 18

What is hypoxia at high altitudes caused by?

Answer 18

Decreased partial pressure of inspired oxygen PI02

Question 19

Acute response to hypoxia at high altitudes?

Answer 19

Hyperventialtion

Increased CO

Question 20

Symptoms of acute mountain sickess?

Answer 20

Headache 
Fatigue 
Nausea 
Tachycardia 
Dizziness 
Sleep disturbance 
Exhaustion 
SOB 
Unconsciousness

Question 21

Chronic adaptions to high altitudes hypoxia?

Answer 21

Increased

• RBC production
• 2,3 BPG produced within RBC
• Number of capillaries
• No. of mitochondria

Question 22

What plays a major role in adjusting for acidosis? Examples of situations?

Answer 22

Peripheral chemoreceptors

-Lactic acid during exercise, diabetic ketoacidosis

Question 23

What stimulates peripheral chemoreceptors and what does it cause?

Answer 23

H+

• Hyperventilation
• Increases elimination of CO2 from body