The autonomic nervous system Flashcards

1
Q

what is the autonomic nervous system ?

A

A collection of motor neurones (efferents) in the central and peripheral nervous system that innervate smooth muscle, cardiac muscle and glands to regulate their activity

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2
Q

what are the three 3 subdivisions of the autonomic nervous system ?

A

Enteric
– Sympathetic
– Parasympathetic

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3
Q

whats the enteric nervous system ?

A

Works autonomously to control the activity of the GIT
• Consists mainly of the myenteric plexus
• Receives autonomic innervation from the parasympathetic and sympathetic divisions

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4
Q

what do you think of when you read sympathetic

A

fight or flight

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5
Q

what do you think of when you read parasympathetic

A

rest and digest

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6
Q

difference between cranial and spinal nerves?

A

Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), in contrast to spinal nerves (which emerge from segments of the spinal cord)

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7
Q

where does the parasympathetic nervous system originate ?

A

in the brainstem and sacral spinal cord

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8
Q

what do the sacral preganglionic neurons not join with ?

A

the spinal nerve

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9
Q

what do cranial preganglionic neurons travel with ?

A

axons in the cranial nerves

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10
Q

give me four examples of cranial nerves

A

vagus (X): lungs, heart, stomach, small intestines, liver
occulomotor(III) pupil size, lens strength
facial (VII): salivary glands
glossopharyngeal (IX): smooth muscle and glands of throat, viscera of thorax and abdomen

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11
Q

regarding the parasymptateic nervous system: are preganglionic fibres long or short and are they branched ?

A

long and branched

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12
Q

where is the ganglia of the parasympathetic nervous system ?

A

located on or close to their target organs

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13
Q

what are the properties of the postganglionic neurons of the parasympthathetic nervous system ?

A

short projections to innervate their target organs

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14
Q

regarding the parasympathetic nervous system.. whats the type of receptor in the ganglion

A

nicotinic cholinergic receptor (ionotropic)

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15
Q

regarding the parasympathetic nervous system.. whats the type of receptor in the effector organ

A

muscarinic cholinergic receptor (M1-5)

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16
Q

where does the sympathetic nervous system arise from ?

A

from the thoracic and upper lumbar cord

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17
Q

properties of preganglionic neurones in the sympathetic nervous system

A

short un branching preganglionic neurons

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18
Q

where is the ganglia located in the sympathetic nervous system ?

A

close to the vertebral column

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19
Q

properties of postganglionic neurones in the sympathetic nervous system ?

A

long branching projections to innervate their target organs

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20
Q

where do sympathetic preganglionic neurones arise from ?

A

the lateral horn of the spinal grey matter and they axons leave through the ventral root, travel via the white rami to enter the sympathetic chain

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21
Q

what do sympathetic neurons do after entering the sympathetic chain

A

Synapse with postganglionic neurones in the sympathetic chain
– Travel along the sympathetic chain before leaving along a nerve to innervate an outlying ganglion or the adrenal gland
– Leave the sympathetic chain to innervate a collateral ganglion

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22
Q

what would sympathetic innervation of blood vessels result in ? whats the neurotransmitter involved

A

vasodilation.. epinephrine

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23
Q

what would sympathetic innervation of cardiac muscle result in ?

A

contraction.. epinephrine is the neurotransmitter

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24
Q

whats receptor type does the preganglionic neuron synapse in the sympathetic nervous system ?

A

nicotinic cholinergic receptor

25
Q

what receptor type does the postganglionic neuron synapse with in the sympathetic nervous system ?

A

adrenergic receptor.. a and beta adrenoceptors

26
Q

what are adrenergic receptors ?

A

The adrenergic receptors (or adrenoceptors) are a class of G protein-coupled receptors that are targets of the catecholamines, especially norepinephrine (noradrenaline) and epinephrine (adrenaline).

27
Q

what are other transmitters are often co-released in autonomic neurones

A

neuropeptides (VIP, NPY, substance P) and small molecules like 5-HT, ATP and NO

28
Q

what are the 3 main classes of muscarinic cholinergic receptors ?

A

5 types encoded by 5 different genes (M1- M5)

M1 receptors: generally an excitatory effect e.g stimulation of vagus nerve causes secretion of gastric acid

M2 receptors: generally inhibitory effect e.g in heart and on nerve terminals of CNS and peripheral neurones e.g. slowing of heart via vagus nerve

M3: in secretory glands and smooth muscle. generally excitatory e.g. contraction of visceral smooth muscle

29
Q

what are adrenergic receptors spit into ?

A

split into alpha and beta

alpha are excitatory
beta can be excitatory or inhibitory

30
Q

whats the effect of symp on the eye

A

pupil dilation

31
Q

whats the effect of symp on lacrimal gland ?

A

no effect

32
Q

whats the effect of psymp on lacrimal gland ?

A

secretion of tears

33
Q

in the SAN what do beta adrenergic receptors do ?

A

increase heart rate

34
Q

in the SAN what do M2

A

decrease heart rate

35
Q

in the AVN what does Beta adrenergic receptors do ?

A

increase conduction

36
Q

in the AVN what does M2 do

A

decrease conduction

37
Q

in the ventricle what does Beta adrenergic do ?

A

increase contraction

38
Q

what does beta 1 aderenrgic do ?

A

decrease Blood pressure

39
Q

what happens during fight or flight ? sympathetic NS

A
Sympathetic NS – fight or flight
• Increased delivery of oxygen and glucose to muscles
– Inc HR and SV Inc CO
– Vasodilation at muscles
– Vasoconstriction at viscera
– Glucose release into blood
– Inc light entering eye – better visual acuity
increase respiration 
diversion of blood to muscles
40
Q

what happens during rest and digest ?

A
Conserve body resources
– dec HR to lower BP
– Inc secretion of enzymes
– Inc digestion and GI motility
– Promote removal of waste products
41
Q

What is the baroreflex ?

A

The baroreflex is the fastest mechanism to regulate acute blood pressure changes via controlling heart rate, contractility, and peripheral resistance.
The baroreflex provides a rapid negative feedback loop in which an elevated blood pressure reflexively causes the heart rate to decrease and also causes blood pressure to decrease.

42
Q

what are the higher centres involved in autonomic control ?

A
spinal cord, 
brainstem 
hypothalamus 
forebrain 
amygdala
hippocampus 
many other
43
Q

what recognises potential danger ? we’re talking about fight or flight response here

A

forebrain

44
Q

what initiates and maintains the response ?

A

hypothalamus

45
Q

what des hypothalamus do ?

A

Activates sympathetic
• Inhibits parasympathetic
• Alters sensitivity of baroreflex
• Promotes cortisol secretion

46
Q

whats the definition of the autonomic nervous system ?

A

motor neurons that originate from the CNS that regulate the activity of smooth, cardiac muscle and glands and neurons in the gastrointestinal tract (enteric nervous system)

47
Q

where are preganglionic cell bodies found ?

A

Preganglionic cell bodies are found in the spinal cord from T1 to L3 segments.

48
Q

where do preganglionic nerve fibres pass in the sympathetic nervous system ?

A

Their fibres pass via the white rami communicantes to sympathetic chain (paravertebral) ganglia which are arranged on each side of the cord

49
Q

what may the axons of the preganglionic nerves synapse with ? sympathetic nervous system

A

The axons of preganglionic neurones may: i) synapse with postganglionic neurons in one or more of the paravertebral ganglia; ii) synapse in peripheral ganglia (prevertebral/collateral : e .g., coeliac and mesenteric); iii) synapse on adrenaline producing cells of the adrenal medulla.

50
Q

what may the axons of the postganglionic nerves synapse with ?sympathetic nervous system

A
The axons of postganglionic neurones with cell bodies located in the sympathetic chain either: (i) pass back into spinal nerves (via grey rami) to innervate vascular
smooth muscle (blood vessels of skin and skeletal muscle), sweat glands or piloerector muscles of hairs of the skin; ii) pass into visceral nerves (e.g., cardiac, splanchnic, renal sympathetic nerves).
51
Q

where do the preganglionic nerves of the parasympathetic nervous system originate from ?

A

Preganglionic fibres originate from cranial (III, VII, IX and X) and sacral
(S2-S4) regions

52
Q

where are the cell bodies of the postganglionic nerves of the parasympathetic system ?

A

adjacent to or within the effector organ hence the axons are short

53
Q

which neartransmitter excites postganglionic nerve cells in the ganglia of the para and symp nervous system

A

acetylcholine

54
Q

which neurotransmitter is released by the postganglionic nerves in the sympathetic nervous system ?

A

noradrenaline.

55
Q

which neurotransmitter is released by the postganglionic nerves in the parasympathetic nervous system ?

A

acetylcholine

56
Q

what is the ANS concerned with ?

A

maintaining homeostasis

57
Q

give me 6 actions of the sympathetic nervous system ?

A
  1. increases heart rate and force of cardiac contraction resulting in an increase cardiac output
  2. relaxes smooth muscle of airways (via the action of circulating adrenaline) leading to a decrease in airway resistance,
  3. causes pupils to dilate
  4. increases blood glucose via action adrenaline from adrenal medulla 5. piloerection
  5. decreases activity of the gastrointestinal tract
58
Q

give me 4 examples of the parasympathetic nervous system ?

A
  1. decreases heart
  2. constricts smooth muscle of airways (leading to an increase in airway resistance) 3. causes s pupils to constrict
  3. increases activity of the gastrointestinal tract
59
Q

give me some areas of the brain that are involved in controlling the output of the ANS

A

medulla, pons, midbrain The activity of these is influenced by, and influences hypothalamic and cortical areas.