Respiration IV

Question 1

What is the BASIC respiratory rhythm pattern generated by?

How do we know this?

Answer 1

Centres in the MEDULLA

Know this because:
- Lesion between the medulla and the pons - maintain basic breathing pattern

• Lesion BELOW the level of the medulla - basic breathing rhythm is LOST

Question 2

What MODIFIES the basic respiratory pattern?

Answer 2

Inputs from various regions of the brain

Question 3

How can breathing be CONSCIOUSLY altered?

Answer 3

• Hyperventilating

- Breath holding

Question 4

What are the 2 respiratory groups in the medulla?

Answer 4

1) DORSAL respiratory group

2) VENTRAL respiratory group

Question 5

What does the dorsal respiratory group in the medulla control?

Answer 5

Inspiration

Question 6

What does the ventral respiratory group in the medulla control?

Answer 6

FORCED inspiration and FORCED expiration

Question 7

How does quiet EXPIRATION occur?

Answer 7

Passive process - elastic recoil

Question 8

Where do the INSPIRATION outputs from the medulla go to?

Answer 8

1) Down the PHERNIC NERVE to control the diaphragm

2) Down the SPINAL NERVES to control the external intercostal muscles

Question 9

Where do the EXPIRATION outputs from the medulla go from/to?

Answer 9

From: the VENTRAL RESPIRATORY GROUP

To:

• INTERNAL intercostal muscles
• ABDOMINAL muscles

Question 10

What complex in the medulla controls the basic breathing pattern?

How do we know this?

Answer 10

PRE-BOTZINGER COMPLEX

Know this because:
The activity in the HYPOGLOSSAL nerve matches the Pre-Botzinger complex output

Question 11

Where is the pre-botzinger complex present?

Answer 11

At the top of the ventral respiratory group

Question 12

What 3 basic types of pattern output does the Pre-Botzinger complex generate?

Answer 12

1) Eupneic
2) Sigh
3) Gasp

Question 13

What is a eupneic breathing pattern?

Answer 13

Basic, standard breathing

Question 14

What happens to the activity of the Pre-Botzinger complex when there is a sigh?

Answer 14

Increase INTENSITY of spike rate

Question 15

What does a sigh help with?

Answer 15

Gas exchange

Question 16

What happens to the activity of the Pre-Botzinger complex when there is a gasp?

Answer 16

Short, rounded activity spike

Question 17

When does a gasp occur?

Answer 17

When there is shortage of oxygen

Question 18

What are the 2 main classes of neurons in the Pre-Botzinger complex?

Answer 18

1) Pacemaker cells

2) Non-pacemaker cells

Question 19

What is the difference between pacemaker and non-pacemaker cells?

Answer 19

Pacemaker - able to generate their OWN rhythmic action potential

Non-pacemaker - NOT able to generate their own rhythmic action potential

Question 20

Describe the activity of the pacemaker cells in the PB complex

Answer 20

1) Spiking phase - slow, background depolarisation called the SODIUM LEAK CURRENT
2) Reaches point where the membrane remains depolarised
3) Activation of a PERSISTANT SODIUM CURRENT
- Causes BURSTING phase of action potentials –> inspiration
4) Eventually, deactivation of the persistant sodium current
5) Repolarisaion back to normal membrane potential
6) No further inspirations until the activation of the persistant sodium current again

Question 21

What is NALCN?

Answer 21

The sodium leak channel

Question 22

What occurs in a mouse with NALCN KO?

Answer 22

No sodium leak - membrane is hyperpolarised:

• Breathing stops for 5 seconds, 5 times in one minute
• Very IRREGULAR breathing pattern
• Don’t survive past 24 hours

Question 23

What does K+ do?

Answer 23

Determine the resting membrane potential through the K+ gradient across the membrane

Question 24

What does increase in K+ cause?

What does this allow?

Answer 24

Depolarisation

More of a chance for the neuron to enter BURSTING activity

Question 25

What does the transition to bursting activity depend upon?

Answer 25

2 different types of inward current: 1) Persistant sodium current (Inap) 2) CAN cation current (Ican)

Question 26

What is the CAN cation current activated by? When is the CAN cation current activated more?

Answer 26

Ca2+ influx Activated more during the 'sigh' breathing pattern

Question 27

What classes are the pacemaker cells split into?

Answer 27

2 classes: 1) Cadmium SENSITIVE - Neurons relying on Ican for bursting 2) Cadmium INSENSITIVE - Neurons relying on Inap for bursting

Question 28

What alters the background depolarisation of the pacemaker cells? What does this determine?

Answer 28

Altered by inhibitory and excitatory inputs on the neurons of the Pre-Botzinger Determines when the neurons are in spiking phase or in bursting phase

Question 29

What is hypoxia?

Answer 29

LACK of oxygen

Question 30

What impact does hypoxia have on the Pre-Botzinger complex?

Answer 30

Normal breathing --> sighing --> gasping: - Loss of the IPSCs on the Pre-Botzinger complex - Loss of autonomous spiking neurons - Loss of cadmium sensitive neurons - Cadmium insensitive neurons remain

Question 31

What are cadimium insensitive neurons responsible for?

Answer 31

The GASPING pattern of breathing

Question 32

How does the dorsal respiratory group control quiet inspiration?

Answer 32

Sending signals to the inspiratory muscle

Question 33

When is the dorsal respiratory group active?

Answer 33

Spontaneously active: 1) Period of ACTIVITY - Activity in the PB sends signals to the DRG, activating it 2) Shuts OFF - No signalling of the PB to the DRG 3) Period of activity again

Question 34

What happens when the dorsal respiratory group is inactive?

Answer 34

Passive expiration

Question 35

When is the VRG inactive?

Answer 35

During quiet respiration

Question 36

When is the VRG active?

Answer 36

During FORCED inspiration/expiration (eg. exercise)

Question 37

How do signals from the pons act on the PB? What does it regulate?

Answer 37

Can have STIMULATORY or INHIBITORY impacts on the PB To REGULATE the RATE and DEPTH of breathing

Question 38

What are the centres in the pons that send signals to the PB?

Answer 38

1) Pneumotaxic centre | 2) Apeneustic centre

Question 39

What does the Pneumotaxic centre do?

Answer 39

INHIBITORY effect on the INSPIRATORY centre - -> Reducing/shortening inspiration phase - -> Shallower breathing (increase rate, reduce depth)

Question 40

What does the Apneustic centre do?

Answer 40

STIMULATES the INSPIRATORY centre - -> PROLONGS inspiration phase - -> INCREASES DEPTH and REDUCES RATE

Question 41

How is the breathing pattern determined?

Answer 41

- MANY inputs on the PB complex (inhibitory/excitatory) - SUM of all the inputs determine the output of the PB (which controls the basic breathing pattern, gasping, sighing etc)

Question 42

What is the Hering-Breuer reflex? Describe this reflex

Answer 42

Negative feedback loop controlling the stretch of the lung: - Stretch receptors in the lung send signals BACK to the medulla when the diaphragm contracts and the lungs INCREASE in volume - Signal via the VAGUS NERVE to the INSPIRATORY centre - -> SHUTS OFF inspiration, to prevent over-inflation of the lungs

Question 43

What is the 'inspiratory centre'?

Answer 43

The dorsal respiratory group

Question 44

What do CENTRAL chemoreceptors do? How?

Answer 44

Monitor conditions in the CEREBRO-SPINAL fluid such as CO2 and pH Increase in CO2 --> acidification

Question 45

Where are PERIPHERAL chemoreceptors located?

Answer 45

In the carotid body and the aortic arch

Question 46

What do the peripheral chemoreceptors respond to?

Answer 46

Increase in Co2 Decrease in pH Decrease in O2

Question 47

What does the stimulation of the chemoreceptors cause?

Answer 47

Increase in ventilation