Physiology and Pharmacology of the ANS

Question 1

What are the Principal Efferent Outputs of the CNS?

Answer 1

Autonomic - exocrine glands, smooth muscle, cardiac muscle, metabolism, host defence

Somatic - Skeletal muscle (diaphragm + respiratroy muscle)

Neuroendocrine - growth, metabolism, reproduction, development, salt + water balance, host defence.

Question 2

Autonomic Nervous system can be subdivided into?

Answer 2

Sympathetic - activated during a threatening (fight or flight) situation in which you need to be really active

Parasympathetic - you don’t need to be active so you’re allowing various other activities to take place under the influence of the parasympathetic nervous system

Question 3

Principal Targets + Functions of the Autonomic Nervous system?

Answer 3

Eye:
S: Dilation
PS: Constriction + Contraction

Salivary Glands:
S: thick secretion
PS: watery

Skin:
S: Piloerection + Increased Sweating

Trachea + Bronchioles:
S: Dilation
PS: Constriction

Heart:
S: increased rate + contractility
PS: decreased rate + contractility

GI:
S: Decreased motility + tone
PS: Increased motility, tone + secretions

Blood Vessels:
S: Dilatation

Liver:
S: Gluconeogenesis + Glycogenolysis

Adipose:
S: Lipolysis

Kidney:
S: Increased Renin secretion

Uterus+Bladder:
S: constriction of sphincter
PS: relaxation

Question 4

What are the 2 main outflows of the PNS?

Answer 4

CRANIOSACRAL OUTFLOW

TOP OUTFLOW = 4 Cranial Nerves:
Oculomotor (CN III)
Facial (CN VII)
Glossopharyngeal (CN IX)
Vagus Nerve (CN X)

BOTTOM OUTFLOW (Sacral region)
SPLANCHNIC NERVE - reproductive organs

pre-ganglionic fibres synpase in the CNS

Question 5

What are the Outflows of the Sympathetic Nervous System?

Answer 5

THORACOLUMBAR (T1-L3) OUTFLOW

• pre-ganglionic fibres leave SC and join together in row of linked ganglia (SYMPATHETIC GANGLIA) next to the spinal cord
• possible to activate whole chain from one part.

Question 6

Which tissues and organs are innervated by both S + PS?

Answer 6

Some tissues and organs are innervated by both the sympathetic and parasympathetic (lacrimal glands, salivary glands, heart and lung)

Question 7

How does innervation to the adrenal medulla differ?

Answer 7

The adrenal medulla ONLY receives pre-ganglionic fibres and instead of activating a post-ganglionic fibres (like all other sympathetic pathways), in this case Chromaffin cells are stimulated to release catecholamines into the general circulation

Question 8

Describe how the parasympathetic outflow is pre-ganglionic?

Answer 8

• The pre-ganglionic parasympathetic fibres go close to or actually in to the tissue that it is innervating so the pre-ganglionic fibres of the PARASYMPATHETIC nervous system tend to be LONG
• POST-GANGLIONIC fibres tend to be SHORT

Question 9

Describe Sympathetic outflow

Answer 9

• SHORT PREGANGLIONIC FIBRE

- LOOOONG POST-GANGLIONIC FIBRE to the innervated tissue.

Question 10

Describe Autonomic Innervation of the GastroIntestinal Tract?

Answer 10

Sympathetic activity = decrease in motility + tone, stimulation of sphincter contraction and inhibition of secretory activity

Parasympathetic activity = increase in motility + tone, relaxation of sphincters, stimulation of secretory activity.

Question 11

Describe Neurotransmitters used by the Autonomic Nervous System?

Answer 11

• Acetylcholine - produced from Acetyl-coA + choline
• Noradrenaline
  (Adrenaline = hormone produced by the sympathetic nervous system)
• These are catecholamines -derived from the amino acid tyrosine, these have the basic structure of a hydroxylated phenyl ring

Question 12

How does the Parasympathetic Nervous System use neurotransmitters?

Answer 12

Pre+Post Ganglionic nerves release Acetylcholine.

Question 13

Sympathetic Nervous System and Neurotransmitters?

Answer 13

• Preganglionic fibres = Acetylcholine

- Majority of post-ganglionic fibres = noradrenaline
acetylcholine –> sweat glands

Question 14

Types of receptor in the parasympathetic nervous system?

Answer 14

Nicotinic - ion channel linked receptor. ACh binds to the receptor, opens and Na+ influx –> depolarisation of post-ganglionic neuron
- Fast transmission.

Muscarinic - GPCR, Slower transmission.

Question 15

Receptor types of the sympathetic nervous system?

Answer 15

Nicotinic ACh Receptors in the post-ganglionic neurons and in the adrenal medulla.

Adrenergic receptors - GPCRs (noradrenaline acts on these)

Question 16

Describe the Acute Stress Response?

Answer 16

• Stress is detected by the hypothalamus
• Relayed down to the sympathetic nervous system
• mass discharge of sympathetic neurons
• links between sympathetic ganglia = mass simultaneous firing of the post-ganglionic fibres to their targets
• stimulation of the adrenal medulla = adrenaline discharge

Tachycardia 
Splanchnic bed vasoconstriction 
Increased metabolic rate  
Sweating  
Pupil dilation 
Increased blood glucose concentration 
Increased mental alertness