4.3-5.1 ANS

Question 1

What is the purpose of the ANS

Answer 1

Critical for controlling bodily functions, including regulation of all organs and most tissue (doesn’t innervate neurons in the brain and skeletal muscle to an extent)

Question 2

What can the ANS be called

Answer 2

• Involuntary NS (outside our conscious control)<br></br>• Visceral motor system (plus blood vessels, sweat glands etc.)

Question 3

Cellular Targets of Autonomic Nerves

Answer 3

• Smooth and cardiac muscle (causes excitation/inhibition)<br></br>• Epithelial transport of ions (results in absorption/secretion across the epithelium)<br></br>• Hormone and mucous secretion (e.g. gut, pancreas, salivary glands)<br></br>• Metabolism (e.g. adipose tissue, liver)<br></br>• Immune cells<div>some tissues have autonomic innervation, but no identified function)</div>

Question 4

Primary components of the ANS: Sympathetic, Parasympathetic (1), Enteric (2)

Answer 4

“<div>Sympathetic, Parasympathetic<br></br></div><div><br></br></div>- Sympathetic and parasympathic NS havecomponents in the CNS and PNS<br></br>(Can’t function without the CNS)<div><br></br><div>ENS</div><div><br></br><div><div><span>- ENS </span>is entirely within gastrointestinal tract (Don’t need CNS)</div><div>- Has its own sensory, motor and interneurons, forning a complete reflexive circuit but it can be infleunced by sympathetic and parasymthetic systems<br></br><div><br></br></div><div><br></br></div></div></div></div></div>”

Question 5

Organisation of the SNS and PSNS (4) Basics

Answer 5

“• Preganglionic neuron has its cell body in the CNS (brain stem and spinal cord)<br></br>• Preganglionic axon projects into the PNS<br></br>• In the PNS, preganglionic and postganglionic neurons synapse in an autonomic ganglion<br></br>• Postganglionic neurons axon project to the organ (effector tissue)<div><br></br></div><div><img></img><br></br></div>”

Question 6

Location of Neurons in the ANS: Sympathetic NS (Preganglionic neuron and Postganglionic neuron)

Answer 6

“Preganglionic neuron cell bodies are located in the thoracolumbar<br></br>region of the spinal cord.<div><br></br></div><div>Postganglionic neuron cell bodies are located in ganglia close to the spinal cord<div><br></br></div><div><img></img><br></br></div><div><img></img><br></br></div></div>”

Question 7

Location of Neurons in the ANS: Parasympathetic NS (Preganglionic neuron and Postganglionic neuron)

Answer 7

“Preganglionic neuron cell bodies are located in the brain stem and sacral part of the spinal cord (cranio-sacral)<br></br>Postganglionic neuron cell bodies are located in ganglia close to or in the effector organ<div><img></img><br></br></div><div><img></img><br></br></div>”

Question 8

NTs involved in SNS and PSNS: Preganglionic Neurons

Answer 8

“• Both sympathetic and parasympathetic preganglionic neurons release ACh<br></br>• Binds to nicotinic receptors on postganglionic neurons<div><br></br></div><div><img></img><br></br></div>”

Question 9

NTs involved in SNS and PSNS: Postganglionic Neurons. Including the updated view

Answer 9

“• Sympathetic postganglionic neurons release: (a) NA, binds to α or β adrenoreceptors in effector tissues; (b) ACh, binds to muscarinic receptors in effector tissues<br></br><br></br>• Parasympathetic postganglionic neurons release ACh, which binds to<br></br>muscarinic receptors in effector tissues<br></br><div><br></br></div><div><img></img><br></br></div><div><br></br></div><div>Updated View:</div><div>• Many subtypes of ACh and NA receptors in tissues<br></br></div>• Many other NTs in the ANS (e.g. nitric oxide, ATP, peptides etc.)<br></br>• Co-transmission = more than 1 NT is released from a synapse”

Question 10

Function of SNS: Conventional View

Answer 10

“Fight-or-flight”: Mass activation of many sympathetic pathways at once to overcome or escape from a major threat (e.g., increase HR)

Question 11

Sympathetic nervous system: FunctionRealistic view (About Fight or Flight)

Answer 11

“Fight-or-flight” concept greatly underestimates the diversity and sophistication of sympathetic control

Question 12

Function of PSNS: Conventional

Answer 12

“Rest-and-digest”: different (not always opposite) actions than required during fight- or- flight

Question 13

Are sympathetic and parasympathetic systems antagonistic? (3)

Answer 13

“<img></img>”

Question 14

CNS integration step one

Answer 14

“Incoming Sensory Information:<div><br></br></div><div>- The caudal part of the nucleus of the solitary tract (NST) in the medulla receives many of the sensory inputs from visceral organs<br></br>- NST is a major integrative centre for autonomic function<br></br></div><div><img></img><br></br></div>”

Question 15

CNS integration step 2

Answer 15

“Information is then distributed to either:<div><br></br>1. Provide feedback to reflexes that control organ/tissue function</div><div><br></br>2. Provide information to higher centres to drive more complex responses (coordinate behaviour of visceral, somatic and endocrine systems)</div><div><br></br></div><div><img></img><br></br></div>”

Question 16

CNS integration: Role of the hypothalamus (Inputs)

Answer 16

Hypothalamus receives:<div><br></br><div>1. Sensory inputs (from visceral afferents, visual afferents, olfactory afferents etc.)<br></br>2. Contextual information from other brain regions<br></br>3. Hormonal signals (access via circumventricular organs)</div><div><br></br></div><div><div><br></br></div><div><br></br></div></div></div>

Question 17

CNS integration: Role of the hypothalamus (Action)

Answer 17

Compares situation to biological set points, then adjusts behavior, autonomic and endocrine function to achieve outcomes (e.g., activation of SNS in fight-or-flight)

Question 18

Spinal cord injury: Impact

Answer 18

Therefore the impact of spinal cord injury is not simply subtractive, but adds new problems due to neural and nonneural changes.

Question 19

Autonomic dysreflexia: ‘symptoms’

Answer 19

Acute hypertensive episode triggered by peripheral signals such as bladder/bowel distension, urinary tract infection, nociceptor activity (even though person may/will not feel pain).<div><br></br>This rapid and potentially extreme hypertension can lead to stroke, seizure, death.</div>

Question 20

Autonomic dysreflexia: mechanism (3)

Answer 20

“1. Sensory activity (1) triggers vasoconstrictor reflex (2)<div>2. Brain detects rise in blood pressure (3) but it cannot control it (as it would if spinal cord was intact).<br></br>3. That is, this reflex cannot be counterbalanced as normal by brain regulation of sympathetic and parasympathetic pathways (4)</div><div><br></br></div><div><img></img><br></br></div>”

Question 21

Bladder DysfunctionPrimary problems (3)

Answer 21

o Incontinence (lack of voluntary control over urination)<br></br>o Uncoordinated voiding (bladder contraction with a closed sphincter)<br></br>o Bladder and renal damage

Question 22

Bladder DysfunctionSecondary problems (3)

Answer 22

o Hypertrophy of bladder muscle from continued overdistension (expansion)<br></br>o Bladder lining (urothelium) acutely degrades but repairs to a leakier form, which is vulnerable to infection<br></br>o Bladder nerves undergo changes

Question 23

What is visceral pain? (1)

Answer 23

Pain originating from internal organs (painkillers are useless)

Question 24

Bioelectronic Medicine: Overview

Answer 24

Overview: Swapping pharmaceuticals for devices<br></br><br></br>

Question 25

Bioelectronic Medicine: Goals (2)

Answer 25

• Goal is to activate or reduce activity of the neural pathway of choice<br></br>• We want to develop miniaturized devices to stimulate/decrease activity of nerves (Target = Vagus Nerve)<div><br></br></div>

Question 26

Bioelectronic Medicine: Challenge (1)

Answer 26

Challenge is that in many peripheral nerves, sensory and autonomic, axons are intermingled