10, 11 and 12 - Autonomic Nervous System Flashcards Preview

Physiology Exam 1 > 10, 11 and 12 - Autonomic Nervous System > Flashcards

Flashcards in 10, 11 and 12 - Autonomic Nervous System Deck (172):
1

What is the autonomic nervous system?

The portion of the nervous system that controls most visceral functions and accommodates coordinated responses to external stimuli

2

Are autonomic disorders being sufficiently considered, suitably investigated and appropriately managed in clinical practice?

NOOOOOO

3

What accounts for these issues with ANS disorders?

Symptoms are so variable

4

What does the central nervous system consist of?

Brain
Spinal cord

5

What does the peripheral nervous system consist of?

Somatic nervous system
Autonomic nervous system

6

What are the two parts of the somatic nervous system?

Somatic efferent nerves which innervate skeletal muscles
Somatic and visceral afferent nerves

7

What are the three components of the autonomic nervous system?

Sympathetic division (SANS)
Parasympathetic division (PANS)
Enteric division (which is closely interconnected with SANS and PANS)

8

In the sympathetic division of the ANS, the preganglionic fibers are _________ compared to the postganglionic fibers.

Short

9

In the parasympathetic division of the ANS, the preganglionic fibers are ________ compared to the postganglionic fibers

Long

(long pre, short post)

10

Why do parasympathetic fibers have longer presympathetic fibers?

Because they synapse in the wall of the visceral organs, so they have to travel a long way to get there (long pre) but they are very close after they synapse (short post)

11

What is the one exception to the two-neuron organization of the ANS? (meaning there is a pre and post ganglionic nerve)

The adrenal medulla

12

Why is the adrenal medulla an exception?

It is considered to be a giant ganglion that does not have post-gaglionic fibers (there fore there is only one nerve, the presynaptic nerve)

13

What does the adrenal medulla release?

- Epinephrin
- Norepinephrin
- Dopamine
- Peptides

14

Where are these neurotransmitters released?

Directly into the blood stream

15

Is activation of the ANS involuntary or voluntary?

Involuntary

16

Can responses to a stimuli in the ANS be excitatory, inhibitory or both?

Both

17

What spinal levels contribute to the sympathetic division of the ANS?

The throaco-lumbar section (T1-L3,4) as well as some cranial nerves

18

At the spinal level, where do the autonomic neurons lie?

The intermediolateral cell column (AKA lateral horn)

19

Where is the intermediolateral cell column located?

Between the dorsal and ventral horns

20

Where do axons from preganglionic sympathetic neurons exit the spinal cord?

VENTRAL roots along with axons from somatic motor neurons

21

From the ventral root, the preganglionic sympathetic neurons branch away from the somatic motor neurons and enter the ____________

White communicantes

22

Why is the white communicantes white?

Because most preganglionic sympathetic axons are myelinated, making the white communicantes appear white

23

What is a paravertebral ganglia?

Along the length of the sympathetic trunk are ganglia known as paravertebral ganglia. The ganglia are distinguished as cervical, thoracic, lumbar, and sacral and, except in the neck, they closely correspond to number to the vertebrae.

24

What is a prevertebral ganglia?

Sympathetic ganglia which lie between the paravertebral ganglia and the target organ

25

What is the specialized ganglia?

There are four:
- Superior cervical ganglion
- Celiac ganglion
- Superior mesenteric ganglion
- Inferior mesenteric ganglion

26

There are three modes of innervation in the sympathetic division of the ANS. What are they?

The preganglionic neuron goes to the...

1 - paravertebral OR prevertebral ganglion then becomes a post-ganglionic neuron which then goes to the target organ

2 - specialized ganglion then goes to the target organ

3 - organ directly (adrenal medulla)

27

The parasympathetic division of the ANS emerges from two separate regions of the CNS. What are they?

CRANIO-SACRAL

28

What does the cranial outflow consist of?

Preganglionic fibers in certain cranial nerves

29

Which cranial nerves contain parasympathetic fibers?

Oculomotor nerve
Facial and glossopharyngeal nerves
Vagal nerve

30

Where do the ganglia for parasympathetics coming from cranial outflow lie?

The ganglia lie close to the target organs

31

What does the sacral outflow consist of?

Parasympathetic fibers destined for the pelvic and abdominal viscera emerge from the spinal cord ina bundle of nerves known as the nervi erigentes

32

Where are these parasympathetic fibers destined for?

- Bladder
- Descending large intestine
- Rectum
- Genetalia

33

Where do the sacral outflow of parasympathetic nerve synapse?

In scattered pelvic ganglia

34

What is unique about the pelvic ganglia?

They carry both sympathetic and parasympathetic fibers - the two divisions are NOT anatomically distinct in the pelvic region

35

What is the enteric nervous system?

A collection of nerve plexuses that surround the gastrointestinal tract, including the pancreas and biliary system

36

We say that the enteric nervous system is "sandwhiched" between the ______________

The layers of the gut

37

The enteric nervous system is connected by a ____________

Dense meshwork of nerve fibers

38

What does the myenteric plexus of the enteric nervous system control?

Motility

39

What does the submucosal plexus of the eteric nervous system control?

Ion and fluid transport

40

Where does the enteric nervous system receive input from?

Both the sympathetic and parasympathetic divisions

41

Can the enteric nervous system funciton normally WITHOUT extrinsic input?

YES!

42

One of the characteristics of the autonomic nervous system is DUAL INNERVATION. What does this mean?
***

Most organs receive both sympathetic and parasympathetic innervation, meaning that the actions of the organ are controlled by BOTH systems

43

What are the exceptions to the dual innervation?

ONLY sympathetic
- Hair follicles
- Thermoregulatory sweat glands
- Liver
- Adrenal glands
- Kidney

44

There is one place in the body where the sympathetic and the parasympathetic innervations produce SIMILAR rather than opposing effects. Where is this?

Salivary glands

45

How many somatic nerves release acetylcholine?

ALL OF THEM

46

How many of the preganglionic fiers of the ANS release acetylcholine?

ALL OF THEM

47

Do all post-ganglionic fibers have the same receptors and respond the same way to ACh?

No...

48

What receptor is found at all of the ganglion?

Nicotinic receptors

49

Where does the variability come from?

You will have a different response based on the receptors on the target organs

50

What do parasympathetic POSTganglionic fibers release? (we know their preganglionic fibers release ACh)

Post ALSO release ACh

51

What do sympathetic POSTganglionic fibers release?

They are andrenergic (epinephrine/norepinephrine) or dopaminergic (dopamine)

52

At what part of the body are postganglionic sympathetic fibers dopaminergic (release dopamine)?

Renal vascular smooth muscle

53

What is the exception to the rule of postganglionic sympathetic fibers?

Thermoregulatory sweat glands

54

What do postganglionic sympathetic fibers release at sweat glands?

Acetylcholine because the sweat glands possess muscarinic (muscle) receptors (meaning they respond to acetycholine)

55

What does cholinergic neurotransmission mean?

Its a shorter way of saying acetylcholine neurotransmission

56

There is a general four step method of cholinergic neurotransmission. What is it?

1 - Synthesis of the neurotransmitters at the pre-synaptic terminal
2 - Storage of the neurotransmitter
3 - Release of the neurotransmitterand actions of the transmitter at the receptor sites
4 - Termination of the transmitter's action

57

What are the three steps that happen in the initial synthesis step of cholinergic neurotransmission?

Occurs at the presynaptic terminal...

1 - Uptake of choline by the choline transporter (CHT)

2 - Conjugation of acetylCoA (mito) plus choline with the enzyme choline acetyltransferase (ChAT)

3 - Final product of acetylcholine is formed

58

There is an experimental drug being tested that blocks the synthesis of acetylcholine. What step does it function at?

The uptake of choline - it blocks the choline transporter (CHT)

59

What is the enzyme that conjugates the acetylCoA to the choline?

Cholineacetyltransferase (ChAT)

60

Describe the storage step in cholinergic neurotransmission

ACh is transported into a storage vesicle by a second carrier called the vesicle-associated transporter (VAT) where it remains until secretion

61

What experimental drug is working to prevent acetylcholine storage?

Vesamicol

It attempts to block the VAT or vesicle-associated transporter

62

What is the first step in the release of acetylcholine from a presynaptic terminal

Depolarization of the nerve terminal

63

What happens after the presynaptic termianl has been depolarized?

Voltage-dependent Ca++ enters the presynaptic terminal

64

What does the Ca++ do once it enters the terminal?

Binds to calmodulin

65

What does the Ca++ calmodulin complex associate with (2 things)

VAMP (vesicle associated membrane proteins)
SNAP (synaptosome associated proteins)

66

Botulinum toxin functions at this point during the release of acetylcholine. What does it block?

SNAPs - synaptosome-associated proteins

67

What is the final step of acetylcholine release?

The vesicles fuse to the membrane and the neurotransmitter is released via exocytosis

68

The action of acetylcholine must be terminated once it has had a chance to function... How is it terminated?

First, rapid hydrolysis of ACh to form choline and acetate

Second, choline re-uptake into the terminals

69

What cleaves the ACh into acetate and choline?

Acetylcholine esterase (AChE)

70

What blocks the cleavage action of AChE?

AChE inhibitors

71

Receptors for acetylcholine fall into two categories. What are they?

1 - Muscarinic receptors
2 - Nicotinic receptors

72

What type of receptors are muscarinic receptors?

G protein receptors

73

What happens when the type of G protein in a muscarinic receptor is different?

You get a different response

74

What are nicotinic receptors?

Transmembrane ion channels that consist of five subunits forming a funnel around the mouth of a central core

75

What happens to a nicotinic receptor when ACh is bound?

The mouth of the channel is closed

76

What happens when more than ACh is bound to a nicotinic receptor?

- Conformational change
- Opening of the channel
- NA+ and K+ flow down their gradients
- NA+ influx can create a depolarization and action potential leading to muscle contraction

77

There are two autonomic activities of the eye that we discussed. What are they?

Aqueous humor production
Autonomic pupil sphincter control

78

What type of muscarinic receptor is activated in the eye during these two activities?

M3 receptor

79

Aqueous humor is produced by...

The epithelium of the ciliary processes

80

What are the processes of the pupil sphincter?

- Ciliary muscle allows for near accommodation and the opening of the canal of Schlemm (parasympathetics)

81

What type of receptors would you find in the heart?

M2 receptors predominate, but M3 receptors are also present

82

What is the heart regulated by? Simulation or inhibition?

INHIBITION
***Know this***

83

What does it mean that the heart is regulated by inhibition?

If you ACTIVATE the parasympathetics of the nervous system, you DECREASE the cardiac activity

84

What are the effects of decreasing cardiac activity?

Slow heart reaction, slow contraction of the heart muscles

This is why we rub the eyes to slow the heart

85

What type of receptors are found in the vesicular bladder?

A LOT of M3 receptors

86

If a patient is overdosing on M3 receptor drugs, what is a symptom you will see?

Incontinence and problems with voiding

87

Activation of an MC receptor in the bladder facilitates urination by...

Contracting muscles
Relaxing the trigone
Inhibiting the sphincter

88

Is vascular smooth muscle innervated the same or differently from visceral smooth muscle?

Different

89

How is visceral smooth muscle innervated?

Just by nerve innervation

90

How is vascular smooth muscle innervated?

By BOTH nerve input and endothelial input

91

What is vascular tone controlled by?

Perivascular nerves as well as endothelial factors

92

What happens when an M3 muscarinic receptor is activated in a blood vessel?

It depends on whether or not the endothelium is in tact

93

What happens when an M3 muscarinic receptor is activated in a blood vessel with an INTACT endothelium?

VASODILATION

94

What causes the vasodilation?

Effects of M3 activation on endothelial cells leads to production of endothelium-derived relaxing factors

95

What happens when an M3 muscarinic receptor is activated in a blood vessel with a DAMAGED endothelium>

VASOCONSTRICTION

96

What causes the vasoconstrictuion?

Direct effects of M3 activation on vascular smooth muscle cells causes vasoconstriction (unopposed by NO produced from endothelial M3 activation)

97

What type of muscarinic receptors are found in sphincters?

M3

98

What is the effect of the activation of an M3 receptor found in sphincters?

Mostly relaxation

99

What is the exception to this rule?

The lower esophageal sphincter contracts

100

What type of muscarinic receptors are found in glands?

M3

101

What is the effect of the activation of an M3 receptor found in a gland?

Secretion (sweat for thermoregulation)
Salvation
Lacrimation

102

How would you damage an endothelium so that vasoconstriction would occur instead of vasodilation of vessels?

Smoking
High cholesterol
Diabetes

103

What types of ganglia have nicotinic receptors?

Autonomic ganglia

104

What is the net effect of ganglionic nicotinic receptor activation?

This depends on the balance the ganglia has between sympathetic and parasympathetic innervation

105

Where would you find Nn nicotinic receptors?

AdreNal medulla
AutoNomic ganglia

106

Where would you find Nm nicotinic receptors?

NeuroMuscular junction

107

What is the response when the Nn nicotinic receptor is activated at the adrenal medulla?

Secretion of epinephrin and norepinephrine

108

What is the response when the Nn nicotinic receptor is activated at the autonomic ganglia

Simulation

The net effects depend on PANS/SANS innervation and DOMINANCE

109

What is the effect when the Nm nicotinic receptor is activated at a neuromuscular jucntion?

Stimulation

Twithc, hyperactivity of skeletal muscle

110

Are Nm and Nn the same thing?

No - they are similar but not identical pharmacologically

111

Case study: flower causing pupil to dilate

Inhibition of M3 receptor on pupil
The sphincter inhibits parasympathetics
No contraction of the pupil is possible
DIlation is seen

112

What is andrenergic neurotransmission?

Andrenergic neurons also transport a precursor molecule into the nerve ending, then synthesize the catecholamine transmitter, and finally store it in membrane-bound vesicles

113

Is the process of catecholamine synthesis more complicated or simple in the adrenergic neurons?

Complicated

114

What is the rate limiting step in catecholamine synthesis?

The conversion of tyrosine to dopa

115

What inhiits the rate limiting step of catecholamine synthesis?

A tyrosine analog - METYROSINE

***Know this***

116

What is the final produc in most sympathetic postganglionic neurons?

Norepinephrine

117

In the adrenal medulla and certain areas of the brain, norepinephrine is further converted into ___________

Epinephrine

118

What is the general path to forming the catecholamines?

Tyrosine --> Dopa --> Dopamine --> Norepinephrine -->Epinephrine

This is ONLY in the adrenal medulla

119

Once the catecholamines are formed, they must be stored. How does this happen?

Synthesized catecholamines are transported into vesicles by VMATs (vesicular monoamine transproters)

120

What can inhibit VMATs?

Reserpine *

121

WHat does reserpine cause?

Depletion of the transmitter stores

122

Where does the conversion of norepinephrine to epinephrin take place

In the vesicles if the enzyme is available

123

How are catecholamines released from the presynaptic terminal?

Similar to the release of ACh from cholinergic nerve endings

124

How does termination of the action of catecholamines occur?

Occurs by multiple mechanisms
- Simple diffusion
- Neuronal reuptake
- Extraneuronal uptake

125

Describe simple diffusion

Catcholamines diffuse into the circulationa nd are metabolized

126

Describe neuronal reuptake ***

Catecholamines are taken up at nerve terminals by solute carriers

Norepinephrine = transporter is norepinephrine transporter, NET

127

What does NET do?

It carries norepinephrine and similar molecules back into the cell cytoplasm from the synaptic cleft

128

What else do we call NET?

Reuptake 1 or uptake 1

129

What can inhibit NET?

Cocaine
Tricyclic antidepressant drugs

130

What is the result of inhibiting NET?

Increase of transmitter activity in the synaptic cleft (prolonged activity)

131

Describe extraneuronal reuptake

Catecholamines are taken up via extraneuronal transproters (ENT)

132

What can inhibit ENT?

Many pharmacological agenst such as corticosteroids

133

What type of receptors are adrengeric receptors?

G protein-coupled receptors

134

What is the clinical significance of the adrenergic alpha one receptor?

If you block it, you will see vasodilation and a decreased blood pressure - you can use this clinically

135

What happens when the Ca++ increases near the adrenrgeric alpha one receptor?

Vasoconstriction

136

What happens when the alpha 1 adrenergic receptor is activated in the eye?

***KNOW THIS***

Contraction (the radial (dilator) muscle is affected)

This will lead to mydriasis

137

What happens when the alpha 1 adrenergic receptor is activated in the arterioles of the skin and viscera?

Contraction

This will lead to high diastolic pressure and high afterload

138

What happens when the alpha 1 adrenergic receptor is activated in the veins?

Contraction

This will lead to high venous return and high preload

139

What happens when the alpha 1 adrenergic receptor is activated in the bladder trigone and spincter?

***

Contraction

This will lead to urinary RETENTION

140

What happens when the alpha 1 adrenergic receptor is activated in the male sex organ?

The vas deferens contracts and ejaculation doesn't happen (erection is fine)

141

What happens when the alpha 1 adrenergic receptor is activated in the liver?

High glycogenolysis

142

What happens when the alpha 1 adrenergic receptor is activated in the kidney?

Low renin release

143

What happens when the alpha 2 adrenergic receptor is activated in the prejucntional nerve terminal?

Lower rate of transmitter release and norepinephrine sythesis

144

What happens when the alpha 2 adrenergic receptor is activated in the platelets?

Aggregation

145

What happens when the alpha 2 adrenergic receptor is activated in the pancreas?

Decreased insulin secretion

146

What happens when the beta 1 adrenergic receptor is activated in the SA node of the heart?

Heart rate goes up

147

What happens when the beta 1 adrenergic receptor is activated in the AV node of the heart?

Increase in the conduction velocity

148

What happens when the beta 1 adrenergic receptor is activated in the atrial and ventricular muscles?

The force of contraction, conduction velocity, cardiac output and O2 consumption goes UP

149

What happens when the beta 1 adrenergic receptor is activated in the his-purkinje system?

There is an increase in the automaticity and conductio velocity

150

What happens when the beta 1 adrenergic receptor is activated in the kidney

Renin release increases

151

What happens when the beta 2 adrenergic receptor is activated in the blood vessels?

Vasodilation (distolic BP goes down)

152

What happens when the beta 2 adrenergic receptor is activated in the uterus?

Relaxation

153

What happens when the beta 2 adrenergic receptor is activated in the bronchioles?

Dilation

154

What happens when the beta 2 adrenergic receptor is activated in the skeletal muscle?

Glycogenolysis goes up and contractility goes up

155

What happens when the beta 2 adrenergic receptor is activated in the liver?

Glycogenolysis goes up

156

What happens when the beta 2 adrenergic receptor is activated in the pancreas

Insulin secretion goes up

157

What is the effect of dopaminergic receptor activation in the renal, mesenteric and coronary vasculature?

Vasodilation

158

What is the specific effect in the kidney?

High glomerular filtration rate
High renal blood flow
High sodium excretion

159

What is a homotropic interaction?

The transmitter, by binding to presynaptic autoreceptors, affects the nerve terminals from which it is being released

160

What is a heterotrophic interaction?

One neurotransmitter affects the release of another via actions on heteroreceptors

Example: Norepinephrine affects Ach release & vice-versa

161

There is a heterotrophic interaction in Parkinson's disease. What is it?

Dopamine is reduced in Parkinson's disease
The affect is that ACh is increased

162

How do you treat Parkinson's knowing this?

Either restore the dopamine or inhibit the ACh

163

There are two observed examples of supersensitivity and hyperactivity in chemical transmission. What are they?

- When a nerve is cut, there is supersensitivity downstream
- When a ganglion is blocked for a period of time and then the blocker is removed, you will see hyperactivity of the organs due to supersensitivity

164

Why do we observe this supersensitivity? (2 reasons)

- There is a proliferation of receptors
- There is a loss of the mechanisms that remove the transmitter

165

How is this clinically relevant?

When you take someone off drugs for hypertension (adenoceptor blockers), you will see rebound hypertension following withdrawal of the meds

166

When else would we see this clinically?

When testing for an autonomic disorder...

If you give someone a low dose stimulation and they have an excessive response, they can be diagnosed with an autonomic disorder

167

What is cotransmission?

Neurons release more than one transmitter or modulator, each of which interacts with specific receptors and produces effects, often both pre- and postsynaptically.

168

There are two main functions of the autonomic nervous system. What are they?

1 - Assist the body in maintaining a constant internal environment
2 - Accommodate a coordinated response to an external stimuli

169

How does the ANS assist the body in maintaining a constant internal environment?

- Provides motor control for viscera
- Allows for smooth muscle, cardiac muscle and glands to be regulated
- Allows the autonomic fibers of the peripheral nerves to be accompanied by visceral afferent fibers (originate from sensory receptors in viscera)

170

How does the ANS accommodate a coordinated response to external stimuli?

Examples:
- Pupil response to ambient light
- Fight or flight response

171

Are sympathetic and parasympathetic nervous systems physiological opponents?

NO
***

172

What is the relationship between the sympathetic and parasympathetic nervous systems?
***

They each serve their own physiological function and can be more or less active in a particular organ or tissue according to the need of the moment