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231 > Lecture 16: Autonomic Nervous System > Flashcards

Lecture 16: Autonomic Nervous System Flashcards

1
Q

How many forms of nervous input are there?

A

4

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2
Q

What are the four forms of nervous input?

A

somatic sensory
visceral sensory
special sensory
endocrine

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3
Q

How many forms of nervous output are there?

A

3

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4
Q

What are the three forms of nervous output are there?

A 
somatic motor
autonomic motor (sympathetic, parasympathetic and enteric)
endocrine
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5
Q

What does autonomic motor output control?

A

blood vessels, the bladder, gut motility

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6
Q

What does the endocrine part of nervous system consist of?

A

adrenal glands modified to be a part of the nervous system

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7
Q

Output from the sympathetic autonomic pathway comes from where?

A

the thoracic - lumber region of the spinal cord.

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8
Q

In the sympathetic autonomic pathway, there is the sympathetic chain ganglia. Where are these (including the modifications)?

A

they run parallel to the spinal cord

there are some modifications such as the adrenal medulla

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9
Q

The adrenal medulla is a modified collection of post-ganglionic sympathetic cells that release adrenaline. How do these differ from other sympathetic autonomic ganglia?

A

the adrenal medulla is modified ganglion so that the post-synaptic cells that normally release NE onto the target cell release adrenaline instead

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10
Q

Output from the parasympathetic autonomic pathway comes from where?

A

higher regions of the spinal cord such as the brainstem, especially the vagus nerve from the 10th cranial nerve

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11
Q

What is the vagus nerve?

A

it is a large nerve containing multiple fibres branching multiple times containing also sensory nerves coming back in to the autonomic nervous system as well as efferent fibres going to organs so it branches multiple time and innervates the body from top to bottom

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12
Q

What does the vagus nerve famously control?

A

multiple elements within viscera

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13
Q

Sensory input comes in from where in the spinal cord?

A

the dorsal root

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14
Q

Many organs have dual innervation by what?

A

sympathetic and parasympathetic nervous systems which act in opposite directions (eg. to increase or decrease heart rate)

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15
Q

In the gut, the sympathetic, parasympathetic and enteric nervous systems act together for what?

A

fine control of gastrointestinal functions

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16
Q

Visceral afferent are where?

A

in the vagus nerve, or enter the central nervous system through dorsal roots

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17
Q

The parasympathetic nervous system is responsible for what?

A

rest and digest

faint or freeze

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18
Q

The sympathetic nervous system is responsible for what?

A

fight or flight

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19
Q

Describe the sympathetic nervous system

A

The first synapse is in the paravertebral and prevertebral ganglia of the sympathetic ganglia. ACh is released from the short preganglionic fibre to the long postganglionic fibre. NE is released into the smooth muscle
Except the adrenal medulla which is supplied by preganglionic sympathetic ACh fibres direct from the CNS and this releases NE.

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20
Q

Describe the parasympathetic nervous system

A

There is a long preganglionic fibre and a short postganglionic fibre and ACh is released at this synapse. ACh is released at the target organ

21
Q

Where is the parasympethetic nervous system distributed?

A

less widely, to viscera (mainly via the vagus nerve), salivary glands, eye but NOT to skin or muscles

22
Q

Where is the sympathetic nervous system distributed?

A

widely distributed to salivary glands, eye, skin, viscera and muscles

23
Q

What receptors receive ACh at the synapse between the preganglionic nerves fibres and postganglionic nerve fibres in both the sympathetic and parasympathetic nervous system. What sort of receptors are these?

A

nicotinic AChR which are ionotropic receptors

24
Q

What receptors receive ACh at the synapse between the postganglionic nerves fibres parasympathetic nervous system. What sort of receptors are these?

A

muscarinic AChR

these are metabotropic receptors

25
Q

Where does the adrenal medulla release NE?

A

into the circulation

26
Q

What sort of receptors are on the effector organ to receive NE from the postganglionic fibre in the sympathetic nervous system?

A

they are several subtypes of α and β adrenergic receptors

27
Q

Where can a good summary of the receptors in the sympathetic and parasympathetic nervous system be found?

A

slide 9/10

28
Q

How does nicotine affect the AChR?

A

nicotine binds to the nicotinic receptors so smoking activates the post-ganglionic fibres of both the sympathetic and parasympathetic nervous system and it depends on which one dominates to determine whether you get relaxed or agitated

29
Q

How does the poison from the mushrooms affect the parasympathetic nervous system?

A

they are toxic for the muscarinic receptors in the parasympathetic nervous system

30
Q

How many layers does the ENS have?

A

2

31
Q

What does the ENS respond to?

A

local chemical and mechanical stimulation

32
Q

What does the ENS regulate?

A

motility, secretion and endocrine signalling, through local reflexes

33
Q

Although the activity of the ENS is autonomous, what is it influenced by?

A

parasympathetic and sympathetic inputs, that indirectly increase and decrease intestinal activity respectively

34
Q

What are the two layers of the ENS called?

A

the myenteric plexus and the submucosal plexus

35
Q

How does the ENS work?

A

in the gut wall, there are receptors that respond by action potential generation to distension/stretch of mucosa of the muscle wall

36
Q

How does the ENS control motility?

A

by influencing smooth muscle excitability

37
Q

Describe how motility in smooth muscle in controlled in the ENS

A

There is spontaneous oscillation in the membrane potential of many smooth muscles. In the gut, they are coupled together in synctium so if there is activity in one region of the gut, there may be direct communication with other cells to have coordinated synthesis in collections of muscle cells

38
Q

Describe the contraction of the smooth muscle in the gut

A

There is a spontaneous depolarisation that exceeds threshold to cause an action potential to open Ca2+ channels to engage with excitation. There is a resulting contractile force

39
Q

How can we control the number and force of contraction?

A

by controlling the overall membrane potential and allowing spontaneity to occur by controlling the number and force of contraction

40
Q

Local ENS reflexes do what?

A

propel food along the gut

41
Q

There are no inhibitory motor neurons that tell smooth muscles to relax. Instead, what is there?

A

you either tell the motor neuron connected to those muscle fibres to generate action potentials (contraction) or you suppress the motor neuron output to the muscle (relaxation)

42
Q

What are three neurotransmitters that can cause relaxation of smooth muscles?

A

NO
ATP
VIP
(anally as it is relaxation)

43
Q

What does ATP acting in the neurotransmitter do in the brain?

A

it makes us sleepy which is why caffeine wakes us us because it acts as an antagonist to the ATP receptors

44
Q

What are two neurotransmitters that can cause contraction of smooth muscles?

A

ACh
substance P
(orally as it is contracting)

45
Q

What do the sensory neurons in the myenteric plexus do?

A

sense the stretch of the gut due to something being inside it

46
Q

What are sensory neurons in the submucosal plexus sense?

A

detecting mechanical stimuli and chemicals coming from the food

47
Q

What is serotonin released in response to?

A

activation of the enterochromatin cells and it activates the sensory neuron

48
Q

What does the sensory neuron activated by serotinon do?

A

it allows relaxation by inhibiting the motor neuron via the myenteric plexus (anally) and allows contraction by activating the motor neuron via the submucosal plexus (orally)

49
Q

How does depression treatment affect the gut?

A

The treatment prevents reuptake of serotonin so there is enhanced gut motility

231 (41 decks)

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