57 Neural Control of Respiration and CV

Question 1

What does the CAROTID BODY (peripheral chemoreceptor) detect for RESPIRATION?
What does the CENTRAL chemoreceptors detect for RESPIRATION?

Answer 1

Carotid body: PaCO2, pH, PaO2 (mostly PaO2)

Central: PCO2 and pH

Question 2

What does the CAROTID SINUS detect for CARDIOVASCULAR feedback?

Answer 2

Blood pressure

Question 3

Note: we need blood FLOW, but we regulate blood PRESSURE

Answer 3

.

Question 4

What brainstem tract is involved in signals from the carotid body and the carotid sinus?

Answer 4

Nucleus Tractus Solitarius (NTS)

However, the neurons from each are separate.

Question 5

What are some examples of “higher” CNS areas that influence the respiratory and cardiovascular systems (4)?

Answer 5

Insular Cortex
Amygdala
Paraventricular Nucleus
Lateral Hypothalamus

Question 6

What are brainstem tracts and nuclei that are involved in respiratory and cardiovascular systems (6)?

Answer 6

Nucleus Tractus Solitarius (NTS)
Nucleus Ambiguus
Rostral VentroLateral Medulla (RVLM)
Caudal VentroLateral Medulla (CVLM)

also: Periaqueductal Gray, and Parabrachial Region

Question 7

What are intrinsic regulators of the heart and blood vessels?
What aspects of the heart and blood vessels are regulated by the brainstem?

Answer 7

Intrinsic: pacemakers and autoregulation of pressure
Extrinsic: contractility and vascular smooth muscle tension

Question 8

T/F The heart will keep beating if the head is cut off, but the lungs will stop breathing.

Answer 8

True. Respiration requires the brainstem as its ‘pacemaker.’

Question 9

What is SUDEP?

Answer 9

Sudden Unexpected Death in Epilepsy

Cause unknown. Possibly apnea, hypoxemia, and altered sympathetic regulation.

Question 10

How do emotions affect heart rate and even sudden death?

Answer 10

Emotions through the amygdala can affect heart rate and even cause death
Extreme sympathetics can affect ventricular fibrillation
Extreme parasympathetics can cause extreme bradycardia (Note: keep these patients supine for increased venous return)

Question 11

Describe SYMPATHETIC activity and BLOOD PRESSURE in

non-REM and REM sleep stages.

Answer 11

In NREM, sympa and blood pressure DECREASE

In REM, there are SPORATIC INCREASES of sympa and blood pressure.

Question 12

Describe the circumstances of circadian sudden death?

Answer 12

Peaks at 4 to 6 AM when the combination of sympathetic activity increases (to wake you up) plus REM sleep stage increases sympa and blood pressure

Question 13

Explain the sympathetic hypertension theory.

Name one example of intermittent stress (note: this is a physical stress, not a social stress)

Answer 13

Intermittent high stress leads to vascular smooth muscle contraction.
Eventually, this contraction leads to hypertrophy of the smooth muscles and heart.
This permanently increases blood pressure.
e.g. Sleep apnea

Question 14

What are the three clusters of neurons in the brainstem that control respiration?

Answer 14

Pontine Respiratory Group (PRG)
Dorsal Respiratory Group (DRG)
Ventral Respiratory Group (VRG)

Question 15

What makes up the Pontine Respiratory Group?

Answer 15

Parabrachial and Kolliker-Fuse nuclei in the rostral dorso-lateral pons

Question 16

Where is the Dorsal Respiratory Group?

Answer 16

NTS

Question 17

What is part of the Ventral Respiratory Group?

Answer 17

Nucluus Ambiguus

Pre-Botzinger complex

Question 18

All together, what are the three clusters of neurons and their locations and subgroups in the brainstem that control respiration?

Answer 18

Pontine Respiratory Group (PRG): Parabrachial and Kolliker-Fuse nuclei in the rostral dorso-lateral pons
Dorsal Respiratory Group (DRG): NTS
Ventral Respiratory Group (VRG): Nucluus Ambiguus and Pre-Botzinger complex

Question 19

What is the proposed “pace maker” of the respiratory rate?

Answer 19

the Pre-Botzinger complex

Question 20

What is the roles of the hypoglossal and genioglossal in respiration?

Answer 20

Keep the tongue out of the way

Question 21

What are the general inputs to the brainstem for feedback regulation of respiration rate (4)?

Answer 21

Carotid body: PaCO2, pH, PaO2 (mostly PaO2)
Central: PCO2 and pH
Vagus: lung and airway receptors
Chest wall: muscle receptors

Question 22

Extra credit: What are the locations of the presumed central chemoreceptors for respiration (7)?
(The point is that they are spread out over many areas)

Answer 22

RTN: Retrotrapezoid nucleus
Medullary Raphe
Nucleus of the Solitary Tract (NTS)
Locus Ceruleus
Fastigial Nucleus of the Cerebellum
Rostral Aspect of the Ventral Respiratory Group (VRG)
Hypothalamic Orexin neurons

Question 23

Explain three examples of “higher” brain centers overriding the brainstem respiratory rate.

Answer 23

1) Sleep can cause hypoventilation and apnea (even without obstruction)
2) Emotion can cause hyperventilation
3) Volition can override breathing rates via corticospinal tracts

Question 24

Explain the numbness and tetany that is caused by hyperventilation.

Answer 24

Numbness and tingling of the fingers and carpopedal spasm (tetany) are caused by decreased plasma Ca ions from respiratory alkalosis which causes Ca bindng to plasma proteins

Question 25

What is Sudden Infant Death Syndrome (SIDS)? What age is peak? What neurotransmitter deficiency?

Answer 25

Peak incidence at 2-6 months due to cardiovascular and/or respiratory failure Serotonin deficiency is indicated Overall cause remains unkown

Question 26

Summary 1:

Answer 26

Summary 1: The heart beat originates at the SA node but cardiovascular function and blood pressure regulation depend on an autonomic control system that modulates sympathetic and parasympathetic activity to heart and resistance vessels based on feedback from the baroreceptors that detect changes in blood pressure. We monitor and regulate the blood pressure.

Question 27

Summary 2:

Answer 27

Summary 2: Respiration originates within medullary neurons that drive motor output via the phrenic nerve to diaphragm and other respiratory muscles. The level of ventilation is determined by a control system the modulates respiratory motor activity based on feedback from chemoreceptors in the carotid body and in the brain. We monitor and regulate the PaCO2.

Question 28

Summary 3:

Answer 28

Summary 3: The basic brainstem neuron groups involved in these two control systems are located close together but are not identical. The NTS receives afferent input from carotid body and carotid sinus. The source of sympathetic control is the RVLM. The nucleus ambiguous contains most respiratory neurons a subset of which may be the respiratory pacemakers.

Question 29

Summary 4:

Answer 29

Summary 4: Neuronal activities from parts of the CNS rostral to the brainstem can impinge upon these brainstem cardiorespiratory control sites and cause mischief. Seizures represent an abnormal form of neuronal activity, which can cause death presumably via cardiorespiratory effects (SUDEP). Profound emotional experiences can also cause death. Sleep is associated with cardiorespiratory events of surprising malevolence.