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The Autonomic Nervous System Flashcards

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1
Q

What is the general function of the autonomic nervous system?

A
  • controls the:
  • efferent motor control of skeletal muscle
  • cardiovascular system
  • respiratory system
  • digestive system
  • urinary system
  • reproductive systems
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2
Q

What does the parasympathetic nervous system have a stimulatory effect on?

A
  • eye = constricts pupil
  • salivary glands
  • lungs = constricts airways
  • stomach
  • pancreas
  • gallbladder
  • bladder
  • genitals = erection
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3
Q

What does the parasympathetic nervous system have an inhibitory effect on?

A
  • the heart
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4
Q

What does the sympathetic nervous system have a stimulatory effect on?

A
  • eye = dilates pupil
  • skin
  • lungs = dilates airways
  • heart
  • liver
  • adrenal gland
  • genitals = ejaculation
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5
Q

What does the sympathetic nervous system have an inhibitory effect on?

A
  • salivary glands
  • stomach
  • pancreas
  • gallbladder
  • bladder
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6
Q
A
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7
Q

Are the actions of the autonomic nervous system voluntary or involuntary?

A
  • mainly involuntary
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8
Q

What are most of the organs innervated by?

A
  • the SNS and PNS
  • their actions are almost always opposite
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9
Q

How does autonomic outflow of the SNS & PNS provide coordinated control over the organs of the body?

A
  • afferent information from autonomic receptors is sent to the CNS
  • to inform the integrated response of the autonomic nervous system
  • to disturbances in blood pressure or blood gases
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10
Q

What are the three major divisions of the autonomic nervous system?

A
  • sympathetic
  • parasympathetic
  • enteric
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11
Q

Where are the control and integration centres for the SNS & PNS?

A
  • the brain stem
  • these central areas generate the command signals that exit the CNS
  • VIA THE CRANIAL NERVES,
    OR - TRAVEL DOWN THE SPINAL CORD TO EXIT VIA SPINALROOTS
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12
Q

What do the neurones from the brainstem synapse with before they exit?

A
  • PREGANGLIONIC NERVES
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13
Q

What happens when the preganglionic nerves exit the CNS?

A
  • they synapse with GANGLIA
  • the nerves they synapse onto are called POSTGANGLIONIC NERVES
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14
Q

What do the postganglionic nerves do?

A
  • they synapse onto the end organ / target organ
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15
Q

Why is them synapsing to the end organ different to skeletal muscle innervation?

A
  • in skeletal muscle innervation
  • the nerve exits the spinal cord
  • travels directly to the skeletal muscle with no further synapse
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16
Q

What does the synapse in the autonomic nervous system offer?

A
  • further opportunity for the command signals to be modified
  • by a local reflex nerve activity
  • as there may be several preganglionic nerves converging onto a single postganglionic nerve
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17
Q

What is the neurotransmitter released by preganglionic nerves within the ganglia?

A

ACETYLCHOLINE

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18
Q

What is the transmitter released by the postganglionic nerves in the SNS?

A

NORADRENALINE

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19
Q

What is the transmitter released by the postganglionic nerves in the PNS?

A

ACETYLCHOLINE

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20
Q

What is the sympathetic division?

A
  • preganglionic cell bodies in the spinal cord between T1 & T2 and that exit the anterior root of the cord, into the spinal nerve
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21
Q

What are the three regions the preganglionic nerves can pass to?

A
  1. Sympathetic chains either side of the spinal cord
  2. Collateral ganglia in the abdomen or pelvis
  3. Adrenal medulla
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22
Q
  1. Sympathetic chains either side of the spinal cord:
A
  • they synapse at the same spinal level, where they emerge from the cord = 1a
  • or may course up or down the chain for a level or two, before synapsing = 1b
  • postganglionic nerves then innervate organs in the skin and organs in the head or thorax
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23
Q
  1. Collateral ganglia in the abdomen or pelvis
A
  • they pass through the chains via sympathetic nerves to collateral ganglia further away in the abdomen or pelvis
  • the postganglionic nerves innervate viscera = heart, lungs, GI tract etc
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24
Q
  1. Adrenal medulla
A
  • they pass through to the adrenal medulla
  • where they synapse onto the chromaffin cells
  • which release ADRENALINE or NORADRENALINE into the blood stream
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25
What do the postganglionic nerves do then?
- originate in one of the sympathetic chain ganglia / collateral ganglia - travel to innervate various organs - they can be longer than the ones in the PNS - they are unmyelinated, thin C fibres - vulnerable to damage in diseased states
26
What has to happen in order for sympathetic innervation of skin?
- postganglionic nerves pass back from the sympathetic chain and re-enter a spinal nerve - to innervate blood vessels, sweat glands, piloerector muscles & adipose tissue
27
What does the SYMPATHETIC nervous system control?
- eye - sweat glands - heart - respiratory tract - liver - gi tract - kidney - bladder - vas defers - blood vessels - adipose tissue - piloerector muscles - adrenal medulla - metabolic - cardiovascular
28
Eye:
- contracts the radial muscle of the pupil to dilate it
29
Sweat glands:
- increased sweat production, acetylcholine
30
Heart:
- increases rate of the pacemaker in SAN - increases heart rate = beta-1-receptors - increases force of contraction = beta-2 receptors
31
Respiratory tract:
- dilates airway smooth muscle
32
Liver:
- increases glucose release & glycogenolysis
33
GI tract:
- decreases motility by reduced peristalsis & increased sphincter tone
34
Kidney:
- reduces renal blood flow & renal output
35
Bladder:
- allows storage by relaxing the body of bladder - contracts sphincter
36
Vas deferens:
- ATP-mediated contraction during ejaculation
37
Blood vessels:
- vasoconstriction = binding to alpha-adrenoceptors - vasodilation = when binding to beta-adrenoreceptors
38
Adipose tissue:
- increased lipolysis and FFA in blood
39
Piloerector muscles:
- makes hair stand up
40
Adrenal medulla:
- release of adrenaline and noradrenaline
41
Metabolic:
- increases production & mobilisation of glucose into blood - increases metabolic rate
42
Cardiovascular:
- increases blood pressure due to increased cardiac output and arterial vasoconstriction
43
Where do preganglionic nerves from the thoracic segments pass directly into?
- the adrenal medulla
44
Where is the adrenal medulla?
- it is glandular tissue that lies superior to the kidney in close proximity, but it has a separate nerve and blood supply
45
What do the preganglionic nerves synapse on to?
- CHROMAFFIN cells - which are like postganglionic nerves as they release catecholamines - but these cells release them directly into the blood supply so they act as hormones
46
What does this then activate?
- the receptors associated with sympathetic nerves & the ones associated with neuromuscular junctions - so there is more widespread effects
47
Why are the widespread effects useful?
- they last much longer than nerve activated responses - as there are enzymes in the blood to break down the catecholamines
48
What do the CHROMAFFIN cells do?
- release adrenaline and noradrenaline, in a ratio of 5:1
49
What does the release of noradrenaline & adrenaline do from the chromaffin cells?
- affects target organs in a similar way to individual stimulation via the SNS nerves - except all at once
50
Why are the metabolic effects much greater?
- due to adrenaline having a much greater effect on metabolism than noradrenaline - when the adrenal medulla releases catecholamines, it supplements SNS effects - important for flight & fight responses
51
What is the neuroneffector junction?
- the junction between sympathetic nerves and a target organ - different from the neuromuscular junction - the neuromuscular junction is between the alpha-motor neurone & skeletal muscle
52
What is there a lack of in the terminal region of the postganglionic nerve?
- no synaptic knob
53
What does the nerve do?
- branches to penetrate the outer layers of the end organ
54
What are the knobbly enlargements on the terminal regions called and what are they for?
- VARICOSITIES - they contain vesicles where the neurotransmitter is stored - they pass over target organs cells - intra-junctional and extra-junctional receptors
55
What is the predominant transmitter for the SNS?
NORADRENALINE
56
What are the two main families / receptors for noradrenaline?
- alpha - beta
57
What are these receptors sensitive to?
- a number of chemicals with similar structures = catecholamines = adrenaline, noradrenaline
58
What does the alpha-receptor have a greater affinity for?
- noradrenaline
59
What does the beta receptor have a greater affinity for?
ADRENALINE
60
What makes the alpha and beta receptors different?
- the G proteins in the membrane to which they are coupled - each G protein activates different second messengers - so they can produce different effects on the target cell - that is why the same transmitter can have different effects in different tissues - as it depends on the receptors present
61
Example of adrenaline action:
- injection of IV adrenaline is likely to drop blood pressure - it will bind to adrenoreceptors on blood vessels, causing vasoconstriction at alpha-adrenoreceptors and vasodilation at b-adrenoreceptors - BUT, as beta-2 adrenoreceptors are more abundant in skeletal muscle they dominate over the alpha-adrenoreceptors effects in the rest of the body - so the overall effect is that blood pressure is lowered
62
Catecholamine actions at the receptor can be stopped by one of three mechanisms:
1. It is reincorporated into the pre or post synaptic vesicles 2. It is broken down by enzymes in the synaptic cleft 3. It diffuses away from the receptor, into the synaptic cleft, then to the extracellular fluid
63
Dominant neurotransmitter for SNS?
NORADRENALINE
64
Dominant neurotransmitter for PNS?
ACETYLCHOLINE
65
What is CO-TRANSMISSION?
- the release of more than one transmitter from the presynaptic nerve, specifically in the autonomic nervous system - is very common
66
What does the SNS release noradrenaline with?
- ATP - neuropeptide Y - enhance each others action
67
What are catecholamine receptors?
- proteins spanning the membrane of a cell that binds to a specific transmitter - released by the presynaptic nerve - causing a response within the cell
68
What do catecholamines do?
- bind to adrenoreceptors - are subdivided into groups
69
Alpha has a greater affinity for?
NORADRENALINE
70
Beta has a greater affinity for?
ADRENALINE
71
What are alpha receptors divided into?
- a1 - a2
72
What does a1 stimulation result in?
- increased calcium ions - excitatory in smooth muscle
73
What does a2 result in?
- decrease - inhibits cell activity - associated with presynaptic inhibition
74
What are the beta receptors divided into?
- beta 1-4 - actions are via secondary messengers
75
What are b1 usually?
EXCITATORY
76
What are b2 usually?
INHIBITORY
77
What way does the PARASYMPATHETIC NERVOUS SYSTEM EXIT the CNS?
- differently to the SNS - either from cranial nerves III, V, IX and X = oculomotor, facial, glossopharyngeal, vagus - or from sacral spinal regions = S2-S4
78
Where do these originate?
- from regions in the midbrain down to the medulla
79
Where do the preganglionic nerves exit the CNS?
- they travel close to the target organ - synapse onto short posysynaptic nerves - either in a ganglion near the target or within the walls of the target
80
Where is majority of the PARASYMPATHETIC nervous output?
- from the VAGUS nerve
81
What do PNS nerves from the cranial nerves innervate?
- targets are in the head & neck, via one of the four ganglia
82
Where does sacral outflow innervate in the PNS?
- organs of the lower abdominal & pelvic cavities
83
What are functions of the PNS?
- eye - sweat glands - heart - respiratory tract - liver - gi tract - kidney - bladder - reproductive system - blood vessels - adipose tissue - piloerector muscles - adrenal muscles
84
Eye:
- contracts the circular muscle of the pupil to constrict - constricts ciliary muscle for near sight
85
Sweat glands:
- not associated with temperature regulation - can initiate sweating on the feet in stressful circumstances
86
Heart:
- decreases slope of pacemaker potential in SAN - decreases heart rate - causes reduction in the force of contraction
87
Respiratory tract:
- constricts airway smooth muscle
88
Liver:
- increase in glycogen synthesis
89
GI tract:
- increases motility by increased peristalsis and reduced sphincter tone - secretion of enzyme containing fluids
90
Kidney:
NO EFFECT
91
Bladder:
- allows urination by contracting the body of the bladder - and relaxing the urinary sphincter
92
Reproductive system:
Genital erection
93
Blood Vessels
NO EFFECT
94
Adipose Tissue
NO EFFECT
95
Piloerector muscles
NO EFFECT
96
Adrenal medulla
NO EFFECT
97
What is the classic PNS neurotransmitter
- ACETYLCHOLINE FROM PRE AND POSTGANGLIONIC TERMINALS
98
What are the 2 major receptor types?
- NICOTINIC - MUSCARINIC
99
What are NICOTINIC receptors?
- operate the opening of ion channels, to cause rapid depolarisation - responsible for ganglionic transmission in the SNS and PNS - always excitatory - found at autonomic ganglia & skeletal muscle neuromuscular junctions
100
What are MUSCARINIC receptors?
- coupled to G-proteins and second-messenger transduction - slower than ion channels - subtypes = M1-M5 - found at the PNS
101
WHERE does efferent activity in the SNS & PNS originate?
- the medulla oblongata of the brain stem
102
Why is the efferent activity formed?
- as a result of intrinsic activity in medullary centres - with input from other brain regions - and afferent systems
103
Autonomic reflex arcs:
- control of blood pressure - afferents = baroreceptors, blood volume receptors, chemoreceptors - central control = medulla oblongata - efferents = the heart, blood vessels = effect = cardiac output, blood pressure & venous flow return to normal
104
What does the activity of an autonomically innervated organ reflect?
- a BALANCE of SNS & PNS inputs
105
Example of autonomic tone:
- heart rate - at rest = slow heart rate reflects the dominance of PNS vagus nerve control - exercise = PNS activity declines, SNS activity dominates - in blood vessels = ongoing activity in the SNS maintains a basal tone - vasoconstriction is achieved = increasing SYMPATHETIC activity - vasodilation - BY WITHDRAWING it
106
What is the enteric nervous system for?
- activity in the gut, controls GI tract - extends in gut wall - controls GI movements and secretions
107
What does the Myenteric plexus between circular & longitudinal muscle do?
- controls gi movements
108
What does the submucosal plexus in the submucosa do?
- controls mucosal secretion & local blood flow
109
The fight or flight response:
- number of autonomic responses evoked simultaneously - when a stimulus, stimulates a specific area of the brain = hypothalamic defence area - to evoke a patterned response in the SNS & PNS - increased heart rate & force of contraction - increased vasoconstriction - increase in blood pressure - blood vessels in skeletal muscle = dilate - blood is diverted from muscle to skin - respiratory airways open further - pupils widen - energy subsrates released into the blood - increased mental awareness - increased pain threshold
110
How are all the actions of the fight or flight response brought about?
1. Increased nerve discharge in sympathetic nerves, withdrawal from muscle blood sympathetics 2. Release of catecholamines from adrenal medulla, it compounds sympathetic activation 3. Decreased PNS outflow

The Nervous System (10 decks)

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