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NAS > WEEK 8 > Flashcards

WEEK 8 Flashcards

1
Q

What is the Autonomic Nervous System?

A

Involuntary division of NS

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2
Q

Three sub-divisions of ANS are

A

Sympathetic, Parasympathetic (and Enteric NS)

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3
Q

What are the two general actions of the ANS?

A

Constancy (homeostasis) and Intermittent change in bias (promotes excretory mechanisms of the body as & when necessary/appropriate)

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4
Q

What are three effector organs of the ANS?

A

Smooth and Cardiac muscle (myogenic-generate own electrical activity), and Secretory glands

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5
Q

What is a ganglion?

A

A collection of cell bodies and glial cells in PNS

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6
Q

What is the general anatomical layout of the ANS?

A

Pre-ganglionic neurone (soma in CNS, axon in PNS) synapses with Post-ganglionic neurone via Post-g soma which forms ganglia, Post-ganglionic neurone synapses with effector

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7
Q

General structure of autonomic signal outflow in Parasympathetic NS

A

ACh released by Pre-g axon terminal, acts on nAChRs on autonomic ganglion in walls of effector organ or near branches of CNV. ACh released by Post-g axon terminal, acts on muscarinic ACh receptors on effector organ

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8
Q

General structure of autonomic signal outflow in Sympathetic NS

A

ACh released by Pre-g axon terminal, acts on nAChRs on autonomic ganglion which form paraveretebral chain or pre-vertebral ganglia. Noradrenaline or adrenaline released from Post-g axon terminal, acts on alpha- or beta-adrenoreceptors

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9
Q

Characteristics of autonomic innervation of organs

A

most receive dual innervation of SNS and PNS, most effects of SNS and PNS are reciprocal (opposing actions), autonomic tone (level of contractility) varies between SNS and PNS

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10
Q

Characteristics of autonomic fibres from cranio-sacral sources

A

Parasympathetic function with soma found in specific, named cranial nuclei (incl. vagal nuclei) or S2-S4 spinal cord segments

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11
Q

How do axons of cranial nuclei travel to periphery?

A

Hitch-hiking on cranial nerve fibres (CNIII (midbrain), CNVII, CNIX, CNX (medulla))

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12
Q

Characteristics of autonomic fibres from thoraco-lumbar sources

A

Sympathetic function, from all neural segments of spinal cord between T1 and L2

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13
Q

What are two disorders resulting from imbalances of autonomic outflow to visceral organs due to CNS lesions?

A

Quadriplegia (paralysis of arms and legs) and Paraplegia (loss of sensation and movement in legs and parts of trunk)

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14
Q

Where are the pre-ganglionic neurones of parasympathetic autonomic outflow to viscera found?

A

Dorsal vagal motor neurones or spinal segmental nerves of S2-S4

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15
Q

Why is lateral horn in spinal cord seen from T1-L2 (+S2-S4)?

A

Collection of cell bodies of pre-ganglionic sympathetic (+parasympathetic) neurones

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16
Q

What is the difference between pre-vertebral and paravertebral chains of ganglia?

A

Pre-vertebral runs in front of vertebrae, Paravertebral runs lateral to vertebrae

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17
Q

What are the sensory components of the ANS?

A

viscera (eg. baroreceptors) and somatosensory/external environment-involves somatic and autonomic integration

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18
Q

How do autonomic motor components differ from somatic components in terms of effector innervation?

A

SNS=skeletal muscle by alpha-motor neurones

ANS=smooth/cardiac muscles and glandular tissue via sympathetic and parasympathetic neurones

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19
Q

What is the difference between no. of neurones between CNS + effector in SNS and ANS?

A

SNS=1

ANS=2 (pre- and post-ganglionic neurones)

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20
Q

What is the difference in action on target tissue between the SNS and ANS?

A

SNS=precise action to effector

ANS=widespread action to target tissue due to pre-ganglionic neurone innervating collection of post-ganglionic neurones

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21
Q

What is the difference in neurotransmitter release in SNS and ANS?

A

SNS=discrete (precise) release

ANS=diffuse (widespread) release via many varicosities (bulges) containing neurotransmitter-containing vesicles

22
Q

What are the exceptions to the general neurotransmitters released by Sympathetic NS?

A

Sweat glands and Adrenal medulla

23
Q

How do sweat glands innervation by ANS differ from convention?

A

Single innervation by Sympathetic NS, Post-ganglionic axon terminal releases ACh instead of noradrenaline

24
Q

How does the adrenal medulla innervation by ANS differ from convention?

A

Innervated by Pre-ganglionic neurone which stimulates release of adrenaline (+NorA) from Chromaffin cells in adrenal medulla into the bloodstream which bind to non-innervated adrenergic receptors

25
Q

Functions of Sympathetic NS

A

alert and active, defence response=fight/fright/flight

26
Q

Functions of Parasympathetic NS

A

rest and digest, energy conservation, digestion, emptying (bladder/bowel)

27
Q

How does ANS work in most organs?

A

Dual innervation and antagonistic action of SNS+PNS

28
Q

How is the smooth muscle GI tract influenced by antagonistic SNS and PNS action?

A

SNS=decreased motility, decreased digestion

PNS=increased motility, increased digestion

29
Q

How is the cardiac muscle of the heart influenced by antagonistic SNS and PNS action?

A

SNS=increased HR

PNS=decreased HR

30
Q

Give an example of dual innervation and antagonistic action, but to different muscles

A

Smooth muscle of Pupil-dilation:
SNS=contraction of radial muscle
PNS=relaxation of circular muscle
(opposite for constriction)

31
Q

Give an example of dual innervation but action isn’t antagonistic

A

Exocrine glands-Salivary glands
Both SNS and PNS cause excitatory (secretory) action, causing increased saliva secretion. However, due to differences in vasomotor tone via SNS and PNS, SNS causes sticky, thick saliva (low in volume) whereas PNS causes watery saliva (high in volume)

32
Q

How is vasomotor tone controlled in most blood vessels?

A

Sympathetic NS
Increased SNS=vasoconstriction
Decreased SNS=vasodilation

33
Q

What is the exception in vasomotor tone control?

A

Blood vessels of head and reproductive organs
SNS=vasoconstriction
PNS-vasodilation

34
Q

What is the exception in blood vessel diameter control in heart and skeletal muscle vessels?

A

Increased SNS activity body-wide causes vasodilation as adrenaline binds to high volume of beta-adrenergic receptors located there

35
Q

Example of SNS and PNS working together

A

male sex organ:
PNS=erection
SNS=ejaculation
(has to occur in this order)

36
Q

Two examples of somatic and autonomic interaction

A 
Focusing eye on a near object:
ANS=pupil/lens adjustment
SNS=eye movements
Response to cold:
ANS=vasoconstriction
SNS=shivering
37
Q

What is the role of the Enteric NS?

A

intrinsic innervation of GI tract (oesophagus to rectum)

38
Q

What are the two major plexuses of ganglion cells and fibre bundles in ENS?

A

Superficial->Deep
Submucosal (Meissner’s) plexus between submucosa and circular muscle-stomach and intestines only
Myenteric (Auerbach’s) plexus between circular and longitudinal muscle-full length of GIT

39
Q

Types of neurones of Enteric NS

A

Afferent (mechano/chemoreceptors), Interneurones (excitatory or inhibitory) and Efferent (secretomotor)

40
Q

How is the GI tract set up based on the types of Enteric NS neurones?

A

Short reflexes to predominantly occur (involves neurones only in GI tract)

41
Q

What do enteric reflexes do?

A

Control motility, secretion and blood flow to gut

42
Q

Motor reflex of Enteric NS

A

Controlled by myenteric plexus (eg. Peristalsis-initiated by mucosal stimulation, causes contraction behind and relaxation in front of bolus of food)

43
Q

Secretory reflex of Enteric NS

A

Controlled by submucosal plexus

44
Q

Blood flow control in Enteric NS

A

Controlled by myenteric and submucosal plexuses via vasoactive neurotransmitters which influence smooth muscle contraction

45
Q

What is the reflex integration with CNS in Enteric NS?

A

ENSSNS/PNSCNS

afferent->

46
Q

What is the main characteristic of long reflexes in Enteric NS?

A

CNS influence (eg. sphincter control over defaecation-not present in children as they have short reflex)

47
Q

What are the causes of ENS dysfunction?

A

Age (decrease in no. and function of neurones)

Disease (Pathology-ENS specifc or general to NS, Function)

48
Q

Give three examples of ENS specific diseases

A

Chaga’s disease (toxin causing neurone death)
Achlasia (failure to open lower oesophageal sphincter when swallowing)
Hirschprung’s disease (known as megacolon due to halting of peristalsis in distal colon)

49
Q

Give three examples of general neurological conditions affecting Enteric NS

A

Parkinson’s disease (Enteric neurones believed to be entry site of ‘Pathogen’)
Peripheral neuropathies
Myasthenia Gravis

50
Q

What is IBS and how does it relate to the Enteric NS?

A

Irritable Bowel Syndrome due to dysfunctional interaction between CNS and ENS (Gut-brain axis)

51
Q

Define outflow

A

The position where the pre-ganglionic autonomic fibres exit the CNS

NAS (9 decks)

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