Autonomic Nervous System II

Question 1

Describe how the ANS differs from the somatic NS

Answer 1

Effectors, Efferent pathways, Target organ responses

Question 2

Describe the effectors of the somatic NS and ANS

Answer 2

SNS: Skeletal muscles
ANS: Cardiac, smooth muscles and glands

Question 3

Describe the efferent pathways of the Somatic NS

Answer 3

Motor neuron cell bodies in CNS/axons extend in spinal/cranial nerves all the way to skeletal muscles they activate

Question 4

Describe the structure of somatic motor fibres

Answer 4

Usually large diameter, heavily myelinated fibres that conduct impulses rapidly

Question 5

Describe the efferent pathways of the ANS

Answer 5

Use 2-neuron chain to its effectors

Usually conduct nerve impulses more slowly than somatic nerves

Question 6

Describe the target organ response of the somatic NS and ANS

Answer 6

Somatic - Always excitatory on NMJ through nAChr

Autonomic - Excitatory/Inhibitory responses of target tissue

Question 7

Describe autonomic NTs

Answer 7

ANS only has 2 main NTs: ACh, Noradrenaline

Question 8

What is the main enzyme involved in synthesis via ACh and NA?

Answer 8

ACh: Cholineacetyltransferase
NA: Dopamine-b-monooxgenase

Question 9

What is the main enzyme involved in breakdown via ACh and NA?

Answer 9

ACh: Cholinesterase enzymes
NA: Monoamine oxidase

Question 10

What is the site of breakdown via ACh and NA?

Answer 10

ACh: Extracellular - Metabolism at synaptic cleft
NA: Intracellular - Metabolism inside neurons

Question 11

Describe the preganglionic neurons of ANS NTs

Answer 11

Always ACh and excitatory

Question 12

Describe the postganglionic neurons of ANS NTs in terms of PS/S

Answer 12

PS: ACh, Cholinergic neurons, Excitatory or inhibitory effects
S: Primarily NA, Adrenergic neurons, Excitatory/Inhibitory effects

Question 13

Describe the adrenal medulla

Answer 13

Preganglionic sympathetic neurons innervate adrenal medulla cells (cholingeric neurons)
Stimulation of AMCs cause release of A/NA into bloodstream
Activation occurs in emergencies

Question 14

Describe the signal transduction processes in cholinergic receptors - nAChR

Answer 14

In all autonomic ganglia (postgang)

LG ion channel - Stimulation causes cation flow to postgang neuron (excitatory)

Question 15

Describe the signal transduction processes in cholingeric receptors - Muscarinic

Answer 15

On all target organs innervated by PSNS
G-Protein coupled receptors
5 main subtypes (M1-5_
Diversity of effects - Relax cardiac muscle, contracts smooth muscle)

Question 16

Describe the differences of nicotinic and muscarinic receptors

Answer 16

N: Ionotropic, Fast excitatory signalling (ms)
M: Slower signalling (secs), Effects depend on signalling pathway

Question 17

Describe adrenergic receptors - alpha/beta receptors

Answer 17

On target organs innervated by SNS
2 subtypes of adrenegic receptors (a/b receptors)
Both subtypes are GPCRs - Activation linked to second messenger pathways

Question 18

Describe the differences between alpha and beta receptors

Answer 18

A: High affinity for NA, Mediate excitatory effects
B: Binds NA/A, Mediate relaxation/dec activity (except on cardiac tissue its excitatory)

Question 19

Describe ANS functional rules

Answer 19

S/PSNS produce opposite effects in GI smooth muscle, heart rate, bladder
Sweat glands/blood vessels only regulated by S innervation
Bronchial smooth muscle only has PS innervation
Ciliary muscle of eye only regulated by PS innervation
Salivary glands innervated by both S/PS to produce similar effect

Question 20

Describe the changes caused by fight or flight response

Answer 20

Heart rate increase
Heart contractility increased
BP increased
Long sight vision increased
O2 delivery to muscles inc
Energy stores activated
Skeletal muscle activity inc

Question 21

Describe what studies on the PSNS show

Answer 21

Studies shows PSNS exhibits dominant activity during non-REM sleep

Question 22

Describe the visceral reflex - The baroreceptor reflex

Answer 22

Carotid artery pressure falls, baroreceptor firing rate in wall falls
Afferent neuron firing dec
Vagal PS firing to heart dec
Heart rate inc, systemic bp rises, brain oxygenated maintained (postural hypotension avoided)

Question 23

What is the ANS vital for?

Answer 23

Short term body homeostasis

Question 24

How is the autonomic function finely controlled?

Answer 24

Using distinct transmitter and receptor systems