Lecture 14: Autonomic nervous system 2

Question 1

Why does the CNS need information from the periphery?

Answer 1

to report on the state of the internal environment, i.e., specialised sensors, visceral sensory nerves (visceral afferents)

Question 2

Why does the CNS need circuits?

Answer 2

to interpret signals, decide on the most suitable outcome, activate the appropriate sympathetic or parasympathetic nerves with the correct sequence and timing and integrate with behavior and higher order functions

Question 3

What do the sensory and integrative CNS centres involved in autonomic function have key roles in?

Answer 3

many complex functions, e.g. stress, pain, sickness, behaviors

Question 4

What are the divisions of the nucleus of the solitary tract in the medulla?

Answer 4

there is a rostral gustatory division and a caudal visceral sensory division

Question 5

What is the role of the caudal part of the nucleus of the solitary tract in the medulla?

Answer 5

receives sensory input (from sensors and sensory nerves) that provide information about various tissues and the environment

Question 6

What is the role of the nucleus tractus solitarius (NTS)?

Answer 6

major integrative centre for autonomic function

Question 7

How is information from the NTS distributed?

Answer 7

provides feedback to reflexes that control organ/tissue function and provide information to higher centres to drive more complex responses (coordinated behaviour: visceral, somatic, endocrine; emotion)

Question 8

What information does the hypothalamus receive?

Answer 8

sensory inputs (e.g. visceral afferents, visual, olfactory)
contextual information from other brain regions
hormonal signals (access via circumventricular organs)

Question 9

What does the hypothalamus integrate with?

Answer 9

higher cortical and limbic systems (emotion, fear, anxiety, motivation, etc.)

Question 10

What are examples of outcomes of the hypothalamus?

Answer 10

feeding / water balance
thermoregulation
circadian rhythms / sexual function
coordinated activation of the fight-or-flight response

Question 11

How does the hypothalamus work?

Answer 11

compares situation to biological set points, then adjusts behavior, autonomic and endocrine function

Question 12

What are the primary issues of spinal cord injury?

Answer 12

partial or complete loss of ascending and descending connections with the brain, therefore no way of sensing or responding properly to changes in the environment or the body’s needs

Question 13

What are the secondary issues of spinal cord injury?

Answer 13

spinal and peripheral nerve circuits can remodel or degenerate
unregulated organs can undergo changes, including altered trophic signaling to peripheral nerves

Question 14

What is the overall impact of spinal cord injury?

Answer 14

not simply subtractive but adds new problems due to neural and non- neural changes

Question 15

What are examples of problems caused by spinal cord injury?

Answer 15

cardiovascular dysregulation, bladder and bowel problems, sexual dysfunction and disrupted thermoregulation

Question 16

When does autonomic dysreflexia occur?

Answer 16

occurs when spinal cord injury at or above spinal level T6

Question 17

What is autonomic dysreflexia?

Answer 17

acute hypertensive episode triggered by peripheral signals such as bladder/bowel distension, urinary tract infection, nociceptor activity -> stroke, seizure, death

Question 18

What is the mechanism of autonomic dysreflexia?

Answer 18

sensory activity triggers vasoconstrictor reflex e.g. brain detects rise in BP but it cannot control it
-> BP cannot be counterbalanced as normal by brain regulation of sympathetic and parasympathetic pathways

Question 19

What is visceral pain?

Answer 19

pain originating from internal organs

Question 20

What is most of our current understanding of pain mechanisms and therapies based on?

Answer 20

biology of somatic pain (skin, skeletal muscle, bone, joint), especially the biology of somatic sensory neurons and their communication with the spinal cord

Question 21

How is the neurobiology of visceral sensory neurons very different from somatic neurons?

Answer 21

most visceral sensory activity is not perceived
visceral nociceptors have more extensive branching
visceral sensory activity can elicit unique sensations (e.g. bloating, nausea)

Question 22

How is visceral pain perceived?

Answer 22

visceral pain is perceived as diffuse, imprecisely localised or
referred

Question 23

How are nociceptors different in organs? What is the implication of this?

Answer 23

respond to more diverse stimuli
send different types of messages
can be involved in normal autonomic reflexes
therefore, many visceral pain states are accompanied by over-activity of autonomic nerves

Question 24

What is the challenge of treating visceral pain?

Answer 24

to devise therapies that reduce visceral pain without disrupting the normal autonomic reflexes

Question 25

What is bioelectronic medicine?

Answer 25

swapping drugs with devices (modulation of visceral nerves)

Question 26

What is the goal of bioelectronic medicine?

Answer 26

to regulate activity of neural pathway relevant to specific organ/disease function (‘neuromodulation’)

Question 27

What are the requirements for bioelectronic medicine?

Answer 27

detailed maps of visceral nerve circuits, computational models of visceral nerve function and devices suitable for attaching to moving organs or visceral nerves