Lecture 24: Respiration

Question 1

Describe the locations and functions of each of the major respiratory centers

Answer 1

DRG: dorsal respiratory group
VRG: ventral
PRG:pontine
BotC:botzinger comlpex
Pre-botzinger complex

DRG and VRG are medullary respiratory

Apneustic and pneumotaxic centers are pontine resp grp

Question 2

Which resp. Center establishes the ramp signal?

Answer 2

Dorsal respiratory system

Begin weakly, increase steadily for about 2 seconds , cease abruptly for about 3 sec.

Question 3

Explain the usual method for controlling the rate of respiration

Answer 3

PRG (pneumotaxic center) is the switch off point of the inspiratory ramp.

DRG initiates the inspiration.

Question 4

What is the function of the hering-breuer inflation reflex? Where does it begin?

Answer 4

This reflex is a protective mechanism to prevent excess inflation of the lungs.

It begins w/ stretch receptors in the muscular portions of the walls of the bronchi and bronchioles.

Question 5

Define apneusis:

Loss of function of which respi. Center leads to apneusis?

Answer 5

Failure to turn off inspiration.

Failure of Pontine-aponeuristic group [PRG]

Question 6

How do the responses of chemoreceptors to hypercapnia or hypoxia differ from responses to these factors by most neurons?

Answer 6

Used to maintain homeostasis of O2, CO2,

*Chemoreceptors INCREASE their rate of activity when hypoxia or hypercapnia occur.

PCO2 and H+ are mainly responsible for regulating ventilation for PO2 btw 60 and 80 mm Hg

Question 7

List and compare functions of central chemoreceptors and peripheral chemoreceptors

Answer 7

Central: indirectly sensitive to CO2 levels-pH change. Kidneys increase blood bicarb levels.

Peripheral: sensitive to [ ] O2, CO2, and H+ ions:
Carotid bodies-stretch, glomus and sustentacular cells.

Question 8

Describe functions of glomus cells and sustentacular cells

Answer 8

Type I cells: chemosensors: PO2-dependent K+ Chanel’s result in K+ efflux w/ PO2 is high, leading to hyperpolarizations of the cells.
Decrease in PO2, closes chanel and results in depolarization that opens Ca+ channels, leading to neurotransmitter release.

Type II cells: sustentacular cells: play a support role like glial cells.

Question 9

Describe location, function, and effects of the following kinds of receptors:

• slow adapting pulmonary stretch
• mechanoreceptors
• J receptors

Answer 9

• slow adapting pulmonary stretch: located w.in airways of lungs. Sensitive to stretch of airway. Prevent airways from being over stretched. Not important @ rest.
• mechanoreceptors: rapidly-adapting pulmonary stretch receptors. W/in airway. Sensitive to irritation, foreign bodies in airway and stretch. Responsible for cough reflex. Can override normal resp control mechanisms.
• J receptors: juxtaposition. Sensory endings- sensitive to pulmonary edema. Small neurons that carry various stimulus including pain. Stimulation leads to cough, tachypnea.

Question 10

Describe cheyne-stokes breathing and discriminate btw hypernea and apnea

Answer 10

Increasingly deeper and rapid breathing (hyperpnea)
Followed by gradual decrease
Resulting in temporary stop(apnea)

REPEAT.
Repeats 30 sec to 2 minutes.

Question 11

Define central sleep apnea syndrome

Answer 11

Abnormalities of the resp. Neuromuscular apparatus. Caused by damage to central resp. Centers.

Question 12

What conditions can lead to cheyne-stokes breathing?

Answer 12

• long delay in transport of blood from the lungs to the brain such as might occur in CHF.
• Increased negative feedback such as might occur in brain damage.