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Physiological concepts > Wk6 - ANS > Flashcards

Wk6 - ANS Flashcards

1
Q

Is the ANS a division of the PNS or CNS?

A

PNS

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2
Q

Is the ANS an efferent or affarent division of the PNS?

A

efferent

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3
Q

Describe the neurons of the ANS, including what their innervations (simple answer)

A
  • visceral affarent and efferent neurons

- innervate (thus regulate) cardiac muscle, smooth muscle, glands

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4
Q

What system does the ANS pair with to maintain the internal environment of the body?

A

endocrine system

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5
Q

What singular structure regulates both the ANS and endocrine system?

A

hypothalamus

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6
Q

What are the 2 main branches of the ANS, and when do these dominate?

A
  1. SNS - fight or flight situations

2. PNS - rest or digest situations

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7
Q

Recent research suggests a third division to the ANS, known as what?

A

the enteric nervous system (ENS)

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8
Q

What does the ENS consist of?

A

Myenteric and mucosal plexuses of the GIT.

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9
Q

Briefly, explain the impact the CNS has on the ENS?

A

The ENS functions independently of extrinsic input; including that from the brain/ SC (CNS).

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10
Q

4 functions of the ENS?

A

“GIMM”

  1. Motility
  2. Gastric acid secretion
  3. Intestinal water & electrolyte transport
  4. Mucosal blood flow
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11
Q

Can the CNS influence visceral activity of the GIT?

A

Yes! Although to a limited extent, the CNS’ influence is really just the modulation of on-going events.

(note: Was your answer no? Don’t get confused between whether or not the CNS can affect the ENS, and whether or not the CNS can affect visceral activity. CNS cannot influence the ENS, however CNS can influence the visceral activity of the GIT. The ENS isn’t the all decider of gut activity, remember it’s only recently discovered!)

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12
Q

How is the CNS informed of visceral activity in the GIT?

A

visceral affarent neurons to the spinal cord and medulla.

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13
Q

Differentiate between the following terms:

Affarent and efferent.

A

Remember ‘E’ for Exit, as in away from CNS.

Affarent - towards CNS (or towards organ for BV’s)
Efferent - away from CNS (or away from organ for BV’s).

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14
Q

Define the following term(s):

Viscera.

A

The internal organs in the main cavities of the body (general term, meaning to do with organs).

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15
Q

Differentiate the SNS and PNS in regards to energy expenditure.

A

PNS - conserves and stores energy in regular situations. This is achieved by promotion of digestion and absorbtion of food, through increased secretions/ peristalsis.

SNS - uses energy in excess for emergency situations. This includes increased HR, RR, CO etc, in response to fear rage or sudden exercise. There’s no point in having heaps of chemical energy inside the body if you’re dead!

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16
Q

Explain how the efferent path (toward effector) differs between the somatic and autonomic NS.

A

Somatic - a singular somatic motor neuron (myelinated) travels to effector. No ganglion. Neurotransmitter is ACh.

Autonomic - ganglion (mass of cell bodies) exist in efferent path. There is therefor a preganglionic neuron (myelinated) and a postganglionic neuron (unmyelinated). The neurotransmitter within the autonomic ganglion is ACh, whereas the neurotransmitter at the effector is ACh or NE.

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17
Q

Explain the parasympathetic response at the following effector organ(s):

a. ) pupil
b. ) salivary glands
c. ) heart

A

a. ) pupil - constrict
b. ) salivary glands - watery secretion
c. ) heart - slower HR

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18
Q

Explain the parasympathetic response at the following effector organ(s):

a. ) lungs
b. ) digestive tract
c. ) endocrine pancrease
d. ) exocrine pancrease

A

a. ) lungs - bronchioles constrict
b. ) digestive tract - increased motility and secretion
c. ) endocrine pancrease - stimulates insulin secretion
d. ) exocrine pancrease - increased enzyme secretion

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19
Q

Explain the parasympathetic response at the following effector organ(s):

a. ) urinary bladder
b. ) sex organs
c. ) uterus

A

a. ) urinary bladder - release of urine
b. ) sex organs - erection
c. ) uterus - PNS effect depends on stage of uterine cycle

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20
Q

Explain the sympathetic response at the following effector organ(s), including what type of receptor is involved:

a. ) pupil
b. ) salivary glands
c. ) heart

A

a. ) pupil - dilate, α
b. ) salivary glands - mucus and enzyme secretion, α and β2
c. ) heart - increased HR and force of contraction, β1

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21
Q

Explain the sympathetic response at the following effector organ(s), including what type of receptor is involved:

a. ) arterioles
b. ) veins
c. ) lungs
d. ) digestive tract

A

a. ) arterioles - constrict, α
b. ) veins - dilate, β2
c. ) lungs - bronchioles dilate, β2
d. ) digestive tract - decreased motility and secretion, α1 and β2

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22
Q

Explain the sympathetic response at the following effector organ(s), including what type of receptor is involved:

a. ) exocrine pancrease
b. ) endocrine pancrease
c. ) kidney
d. ) urinary bladder

A

a. ) exocrine pancrease - decreased enzyme secretion, α
b. ) endocrine pancrease - inhibits insulin secretion, α
c. ) kidney - increased renin secretion, β1
d. ) urinary bladder - urinary retention, α1 and β2

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23
Q

Explain the sympathetic response at the following effector organ(s), including what type of receptor is involved:

a. ) adipose tissue
b. ) sweat glands
c. ) sex organs
d. ) uterus
e. ) lymphoid tissue

A

a. ) adipose tissue - fat breakdown, β
b. ) sweat glands - localised sweating, α
c. ) sex organs - ejactulation (males), α
d. ) uterus - depends on stage of uterine cycle, α1 and β2
e. ) lymphoid tissue - general inhibition, α1 and β2

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24
Q

Provide some examples of effector organs not affected by parasympathetic stimulation? (5)

A
  1. arterioles/ veins
  2. adrenal medulla
  3. kidney
  4. adipose
  5. lymphoid
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25
Q

Provide an example of effector organ not affected by sympathetic stimulation? (don’t spend too long on this question)

A

trick question; no general effector organ of the body is immune to sympathetic stimulation

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26
Q

What are the 6 physiological differences between PNS and SNS? (essay size)

A
  1. SNS has widespread effect - due to preganglionic fibres synapsing onto MANY postganglionic neurones, and the adrenal medulla which releases NE & E.
  2. PNS has discrete control - contrasting to the SNS, the PNS preganglionic fibres synapse with few postganglionic neurones.
  3. SNS has adrenal medulla - PNS has no such comparable organ.
  4. PNS postganglionic fibres release only ACh - in contrast to this the SNS most often releases NE, however does release ACh to some organs (ie. sweat glands)
  5. SNS is energy spending - prepares the body for emergencies.
  6. PNS is energy conserving/ storing - dominates in ‘everyday life’.
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27
Q

What type of receptor is found on the cell body of the postganglionic neurone?

A

nicotinic receptor

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28
Q

What type of receptor is found on the surface of the target tissue, considering this tissue is innervated by the SNS?

A

adrenergenic receptor

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29
Q

What type of receptor is found on the surface of the target tissue, considering this tissue is innervated by the PNS?

A

muscuranic receptor

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30
Q

What neurotransmitter is transmitted between pre & postganglionic neurones?

A

ACh

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31
Q

What neurotransmitter is transmitted between the postganglionic neuron and target tissue, considering this target tissue is innervated by the SNS?

A

Norepinephrine (NE) most of the time, occasionally ACh (ie. if effector is sweat gland).

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32
Q

What neurotransmitter is transmitted between the postganglionic neuron and target tissue, considering this target tissue is innervated by the PNS?

A

ACh

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33
Q

What is the primary structure responsible for maintenance of homeostasis?

A

hypothalamus

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34
Q

The effect brought about by the hypothalamus is dependant on which region of the structure is stimulated. Describe the effect if the hypothalamus is stimulated…

a. ) Anteriorly
b. ) Posteriorly

A

a. ) Anteriorly - influence PNS responses

b. ) Posteriorly - influence SNS responses

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35
Q

Aside from the hypothalamus, what other regions of the brain may influence autonomic responses?
(note: this question regards region based upon function, not actual names like pons etc).

A

Lower brain centres…

  • vasopressor vasodilater
  • cardio-accelerator
  • cardio-decelerator
  • respiratory centres
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36
Q

Explain what is meant by the following general term(s):

Reticular Formation

A

the Reticular Formation is the collective term for all the lower brain centres which, like the hypothalamus, can influence the autonomic response. These include:

  • vasopressor vasodilater
  • cardio-accelerator
  • cardio-decelerator
  • respiratory centres
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37
Q

Explain what autonomic controls the following structure exhibits:
Hypothalamus.

A
  • water balance
  • temperature
  • hunger

(I believe the hypothalamus does more, but it’s Phil’s lecture/ unit)

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38
Q

Explain what autonomic controls the following structure exhibits:
Pons.

A
  • respiration
  • cardiac effects
  • vasoconstriction
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39
Q

Explain what autonomic controls the following structure exhibits:
Medulla

A

Respiration.

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40
Q

The heart is innervated by both SNS and PNS fibres.

Where do SNS postganglionic fibres arise from?

A

the cervical and upper thoracic portions of sympathetic trunks.

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41
Q

How do sympathetic fibres travel within the heart?

A

fibres pass through cardiac plexuses –> terminate on SA and AV nodes & general myocardium

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42
Q

What division of the ANS effects the cardio-acceleratory centre of the heart, and what is the effect?

A

SNS stimulates cardio-acceleratory centre, stimulating increased HR and contraction strength

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43
Q

How do parasympathetic fibres travel toward the heart?

A

via the vagus nerve

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44
Q

How do parasympathetic fibres travel within the heart?

A

parasympathetic fibres (of vagus nerve) synapse with postganglionic neurons in cardiac plexuses, then these postganglionic neuron’s fibres travel to the SA and AV node.

(note: the myocardium is NOT under any PNS innervation, what can you therefor infer about the effect of the PNS on the heart? PNS only affects HR, not contraction strength!)

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45
Q

What is the effect of PNS stimulation on the heart?

A

a decrease in HR.

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46
Q

Cardiovascular reflexes rely on pressure receptors known as baroreceptors. Where are these found?

A
  • carotid sinus

- aortic arch

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47
Q

Explain the step-by-step process of a cardiovascular reflex, beginning with an elevated BP. (8 steps)

A
  1. Elevated BP
  2. Increased AP firing of baroreceptors in carotid sinus and aortic arch
  3. Increased AP firing in affarent nerves
  4. Stimulation of cardiovascular centre (pons)
  5. Three fold response brought about by CVC:
    a. ) decreased sympathetic cardiac nerve activity
    b. ) decreased sympathetic vasoconstrictor nerve activity
    c. ) increased parasympathetic nerve activity
  6. Decreased HR and SV, artereolar and venous vasodilation
  7. Decreased CO and TPR
  8. Deceased BP back to homeostatic levels.
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48
Q

The cardiovascular reflex (response) to increased MAP includes 3 changes within the cardiovascular centre, done in an effort to reduce CO/ TPR, and therefor MAP.

What are these 3 changes brought about by the CVC?

A

a. ) decreased sympathetic cardiac nerve activity
b. ) decreased sympathetic vasoconstrictor nerve activity
c. ) increased parasympathetic nerve activity

49
Q

Briefly explain the Bainbridge right atrial reflex.

A
  1. sensory nerve endings in wall of right atrium and walls of vena cavae become stimulated by increased venous pressure
  2. inhibition of the vagus nerve occurs, reducing parasympathetic outlflow to the heart
  3. also stimulates heart to bring about cardiac acceleration.

This solves the increased venous pressure as a rised venous pressure means too much blood in veins. So reduce PNS and increased cardiac acceleration will empty these veins of there pooled blood (?)

50
Q

Explain the influence of the SNS on the following organ(s):

Lungs.

A
  • sympathetic postganglionic fibres form networks around the bronchi/ BV of the lungs.
  • SNS stimulation induces dilation of airways
51
Q

Explain the influence of the PNS on the following organ(s):

Lungs.

A
  • postganglionic fibres of the PNS form plexuses around brochi/ BV of lungs
  • PNS stimmulation induces constriction of airways, as well as increased glandular secretion into the lungs
52
Q

Explain the influence of the SNS on the following organ(s):

Gut.

A
  • inhibit peristalsis
  • inhibit glandular secretion
  • cause contraction of sphincters
53
Q

Explain the influence of the PNS on the following organ(s):

Gut.

A
  • preganglionic neurons terminate onto postganglionic neurons in the myenteric (Auerbach’s) and submucosal (Meissner’s) plexuses
  • stimulate peristalsis
  • relax sphincters
  • stimulate secretion
54
Q

Autonomic pathways consist of 2 neurons (pre & postganglionic), which synapse within a ganglion. The postganglionic neuron then transmits impulse to effector, most of the time the neurotransmitter for which is ACh.

This is essentially the same process which occurs where?

A

At the motor end plate (neuromuscular junction), which causes subsequent contraction of skeletal muscle. A process which occurs through the somatic nervous system.

(note: the ‘same process’ refers to the electrical -> chemical message from the postganglionic fibre to effector, NOT to the pre and postganglionic fibres. The ANS is characterised with having a ganglion of cell bodies outside the spinal cord, the somatic nervous system is NOT).

55
Q

Briefly detail the abundance of the neurotransmitter Acetylcholine (ACh) within the nervous system.

A
  • released at ALL preganglionic ANS nerve endings
  • released by MOST postganglionic PNS nerve endings
  • released by SOME postganglionic SNS nerve endings (not many, postganglionic SNS is often NE)
56
Q

ACh is released at near all preganglionic ANS nerve endings, and the vast majority of postganglionic nerve endings within the PNS. However, the majority of postganglionic nerve endings within the SNS involve the release of NE instead of ACh.

Provide some examples of effector organs which are exceptions to this case (that is, postganglionic neurons within the SNS which are cholinergic)?

A
  • sweat glands

- vasodilatory neurons to BV within sk muscle.

57
Q

Explain what is meant by the following general term(s):

Cholinergic.

A

Term used to describe neurons in which ACh is the active neurotransmitter.

58
Q

What are the 2 main types of receptors for neurotransmitters (NT) within the ANS?

A
  1. Cholinergic receptors

2. Adrenoreceptors

59
Q

Cholinergic receptors refers to those receptors for ACh. This group can be further subdivided into what 2 types of receptors?

A
  1. Nicotinic

2. Muscarinic

60
Q

Briefly, how do nicotinic receptors bring about change in the postsynaptic neuron? (general answer)

A

Nicotinic receptors exhibit direct action upon the ion channels of the postsynaptic neuron, to bring about a change to membrane potential.

61
Q

Where are nicotinic receptors found?

A
  • ALL postganglionic neurons of both PNS and SNS
  • motor end plate of sk muscle
  • chromaffin cells of adrenal medulla

(note: remember that the first statement is referring to pre to postganglionic nerve transmission, NOT the transmission at the end of the postganglionic fibre with its effector)

62
Q

The mode of action of nicotinic receptors within the ANS is highly similar to what?

A

the mechanisms which occur at the motor end plate (MEP) of skeletal muscle; it primarily involves changes in ion permeabilities, due to the ligand-gated channel which is the nicotinic receptor!

(remember: nicotinic receptors are the ones present at the motor end plate of skeletal muscle, so it makes alot of sense that it’s a highly similar mode of action).

63
Q

How do nicotinic receptors bring about change in the postsynaptic neuron? (specific answer)

A

The nicotinic (ACh) receptor is a ligand-gated ion channel. It is activated due the binding of 2 ACh molecules, and then facilitates the movement of Na+ and K+ ions down there electrochemical gradients.

This means great Na+ influx and K+ efflux, causing depolarisation of the cell.

64
Q

Nicotinic receptors become activated upon the binding of 2 ACh molecules. Describe the type of channel which is subsequently in operation, due to this occurence.

A

A non-specific, monovalent cation channel is brought into operation. This is the channel allowing movement of Na+ and K+, and subsequent depolarisation of postsynaptic membrane.

65
Q

The cytoplasm of the terminal axon in a neuromuscular junction contains vesicles.

a. ) What is contained within these vesicles?
b. ) How large are these vesicles in diameter?
c. ) What other (important) structure is present in this terminal axon, and why?

A

a. ) What is contained within these vesicles - the neurotransmitter ACh.
b. ) How large are these vesicles in diameter - 3-4 nm.
c. ) What other (important) structure is present in this terminal axon, and why - mitochondria, present to clear synaptic terminals of excess calcium.

(note: answer c.) is not 100% certain, although this is the likely purpose).

66
Q

Do the nicotinic receptors found in the MEP and autonomic ganglia differ - if so, how?

A

Yes, they slightly differ.
An example of this is how only nicotinic receptors within ganglia can be blocked by the drug hexamethonium.

This drug does not affect the nicotinic MEP receptor.

67
Q

What enzyme is responsible for metabolising any ACh which does not bind with postsynaptic receptor?

A

Acetylcholinesterase.

68
Q

Explain what is mean by the following general term(s):

Agonist.

A

A chemical which binds to a receptor, and activates the receptor to produce a biological response.
(basically a NT).

69
Q

Explain the effect the drug ‘curare’ has on nicotinic receptors.

A

Curare antagonises (works against; blocks) the action of the nicotinic receptor, in BOTH the MEP and the ganglia.

70
Q

What chemical(s) are able to activate nicotinic receptors?

A

ACh or nicotine.

71
Q

Briefly, how do muscarinic receptors bring about change in the target organ? (simple answer)

A

Activated muscarinic receptors work by altering the membrane bound G proteins, or through activation of secondary
messengers within their target cells.

72
Q

Where are muscarinic receptors found?

A
  • ALL PNS effector organs in the body

- some effector organs of SNS (sweat glands, vascular smooth muscle in the BV of sk muscle)

73
Q

The mechanism of action of muscarinic receptors is similar to that of what?

A

α1 adrenoreceptors.

74
Q

Muscarinic receptors are found within all PNS effector organs of the body, as well as some effector organs of the SNS. Specifically, what does this include?

A
  • sweat glands innervated by SNS

- the vascular smooth muscle of blood vessels located inside skeletal muscle, which are also innervated by the SNS

75
Q

How do muscarinic receptors bring about change in the target organ, with relation to phospholipase C? (extended answer)

A
  1. Binding of ACh to muscarinic receptor causes activation of phospholipase C.
  2. Phospholipase C increases levels of inositol triphosphate (InsP3) and diacyclglycerol (DAG) within target cell.
  3. Increased InsP3 and DAG free’s up intracellular Ca+2, and higher levels of free intracellular Ca+2 induces specific physiological reactions.
76
Q

Expand the following abbreviation:

DAG

A

diacyclglycerol

77
Q

Expand the following abbreviation:

InsP3

A

inositol triphosphate

78
Q

How do muscarinic receptors bring about change in the target organ, with relation to membrane bound G-proteins? (extended answer)

A

Some muscarinic receptors directly affect the membrane bound G-proteins. For example in the SA node of the heart…

  1. ACh binds to muscarinic receptor
  2. Muscarinic receptor induces G protein subunits to bind directly to K+ channels
  3. This causes rate of spontaneous depolarisation to SLOW, decreasing HR.
79
Q

What catecholamine hormones activate adrenoreceptors?

A

adrenaline + noradrenaline

80
Q

Adrenoreceptors are present at the effector organ of somatic pathways (neuromuscular junction). However, they are also present within pathways of the ANS.
Are adrenoreceptors present in the target organs of the SNS, the PNS, or both (the whole ANS)?

A

adrenoreceptors are only present in the target tissue of the SNS. That is, the PNS effector organs do not posses adrenoreceptors.
(note: this is intuitive as the PNS is ‘rest and digest’, whereas adrenaline/ NE are related with stimulatory messages).

81
Q

The postganglionic neurons of the SNS will most often release which NT?

A

noradrenaline

82
Q

Where is adrenaline produced, and how does it reach its target organ?

A

Adrenaline is produced in the adrenal medulla, and reaches its target organ(s) through circulation.

83
Q

Two types of adrenergic receptors can be distinguished, what are these?

A

α and β adrenoreceptors

84
Q

Two types of adrenergic receptors can be distinguished, α and β adrenoreceptors. What criteria separates these two groups?

A

Pharmacological criteria; that is, how there action is affected by drugs.

85
Q

Two types of adrenergic receptors can be distinguished, α and β adrenoreceptors. Describe what distinguishes α adrenoreceptors.

A

α adrenoreceptors action is blocked by α blockers, such as phentolamine.

86
Q

Different adrenergic chemicals have different affinity or strength of binding with different adrenoreceptors. Discuss the relative strength of different adrenergic hormones on α adrenoreceptors.

A

Listed from most “active” to least…

  1. Noradrenaline
  2. Adrenaline
  3. Isoprenaline
87
Q

Different adrenergic chemicals have different affinity or strength of binding with different adrenoreceptors. Discuss the relative strength of different adrenergic hormones on β adrenoreceptors.

A

Listed from most “active” to least…

  1. Isoprenaline
  2. Adrenaline
  3. Noradrenaline
88
Q

Two types of adrenergic receptors can be distinguished, α and β adrenoreceptors. Describe what distinguishes β adrenoreceptors.

A

β adrenoreceptors action is blocked by β blockers, such as propranolol.

89
Q

Describe what is meant by the following general term(s):

Isoprenaline

A

Isoprenaline is a synthetic β-adrenergic stimulant.

90
Q

Provide an example of an α blocker, as well as a β blocker

A

α blocker - phentolamine

β blocker - propranolol

91
Q

Adrenoreceptors can be further divided into smaller subgroups, beyond just α and β. What are these?

A

α adrenoreceptors - α1 and α2 adrenoreceptors

β adrenoreceptors - β1 and β2 adrenoreceptors

92
Q

What distinguishes α1 and α2 adrenoreceptors?

A

mechanism of action

93
Q

What distinguishes β1 and β2 adrenoreceptors?

A

physiological effects (these adrenoreceptors have the same mechanism of action)

94
Q

Where are α1 adrenoreceptors found?

A
  • vascular smooth muscle of skin & gut
  • sphincters of GIT & bladder
  • radial muscle of iris
95
Q

Activation of α1 adrenoreceptors is the vascular smooth muscle of skin & gut, sphincters of GIT & bladder, and
radial muscle of iris leads to what?

A

Muscular contraction in each of these tissues.

96
Q

What does the mechanism of action of α1 adrenoreceptors involve?

A

The mechanism of action of α1 adrenoreceptors involves G proteins & the activation of phospholipase C, which intracellular free Ca+2 causing cellular effects.

97
Q

What receptors are more common, α1 or α2?

A

α1

98
Q

Where are α2 adrenoreceptors located?

A
  • walls of GIT
  • presynaptic adrenergic nerve terminals
  • liver cells
  • platelets
  • smooth muscle of BV’s
99
Q

How can NA be

A
  1. Diffusion into the bloodstream; taken elsewhere.
  2. NA can be broken down by monoamine oxidase (within synaptic cleft).
  3. NA can be transported back into the axon (active transport)
100
Q

α2 adrenoreceptors are found on platelets, as well as the smooth muscle of blood vessels. What does there activation induce in these places?

A
  • platelet aggregation

- BV constriction

101
Q

Briefly, what does the mechanism of action of α2 adrenoreceptors involve? (summary)

A

α2 adrenoreceptors mechanism of action involves G proteins and the inhibition of adenylyl cyclase, resulting in decreased concentration of cAMP.

cAMP is a “secondary messenger” within the cell

102
Q

Briefly, what does the mechanism of action of α2 adrenoreceptors involve? (steps)

A
  1. Signal molecule (adrenaline/ noradrenaline) binds to G-linked protein receptor (α2 adrenoreceptor).
  2. G protein activates
  3. G protein turns on adenylyl cyclase, an amplifier enzyme
  4. Adenylyl cyclase converts ATP to cyclic AMP
  5. cAMP activates protein kinase A
  6. Protein kinase A phosphorylates other proteins, ultimately leading to the “cellular response” to original stimulus
103
Q

Where are β1 receptors located?

A
  • SA node
  • AV node
  • general myocardium
  • salivary glands
  • adipose tissue
  • kidney
104
Q

What is the effect of activation of β1 adrenoreceptors on the heart?

A
  • increased heart rate (SA node)
  • increased conduction speed (AV node)
  • increased contractility of myocardium
105
Q

Briefly, what does the mechanism of action of β1 adrenoreceptors involve?

A

The mechanism of action of β1 adrenoreceptors involves G proteins and the activation of adenylyl cyclase. This increases the concentration of cAMP.

106
Q

Where are β2 adrenoreceptors located?

A
  • vascular SM of sk muscle & heart
  • walls of GIT
  • walls of bladder
  • bronchioles
107
Q

β2 adrenoreceptors are located in the walls of GIT/ bladder, vascular SM of sk muscle/ heart, and the bronchioles. What does activation of these receptors cause at these tissues?

A

relaxation/ dilatation.

108
Q

β2 adrenoreceptors have a similar mechanism of action to that of what?

A

β1 adrenoreceptors

109
Q

Briefly, what does the mechanism of action of β2 adrenoreceptors involve?

A

The mechanism of action of β1 adrenoreceptors involves G proteins and the activation of adenylyl cyclase. This increases the concentration of cAMP.

110
Q

Briefly, what does the mechanism of action of α1 adrenoreceptors involve?

A

G proteins; activation of phospholipase C to increase [Ca+2]

111
Q

Briefly, what does the mechanism of action of α2 adrenoreceptors involve?

A

G proteins; inhibition of adenylyl cyclase to decrease [cAMP]

112
Q

Briefly describe the structure of the adrenal medulla (what is it)?

A

The adrenal medulla is a modified sympathetic ganglion. It forms the core of the adrenal glands, thus there also exists an adrenal cortex.

113
Q

What activates the adrenal medulla? What does this infer about the control of hormone release?

A

Cholinergic synapses with preganglionic sympathetic axons. This means that hormonal release from the adrenal medulla is under neural control.

114
Q

Excitation of the adrenal medulla (sympathetic) causes the release of a mixture of catecholamines. What does this consist of?

A

80-85% adrenaline

15-20% noradrenaline

115
Q

The catecholamines released by the adrenal medulla act on the same effector organs as the postganglionic sympathetic neurons, however differ in the response which they bring about with them. How so?

A

These catecholamines (A and NA) act on the same effector organs as the postganglionic sympathetic neurons, however are mainly involved with the regulation of metabolic processes (as oppose to causing constriction etc).

116
Q

What type of hormone are A and NA regarded as?

A

metabolic hormones

117
Q

Predominantly, through what type of receptors do adrenaline and noradrenaline initiate there effects?

A

β receptors.

118
Q

Whilst the body is at rest, how much catecholamines does the adrenal medulla release?

A

8-10 ng of catecholamines per kg (body weight) per minute.

119
Q

When in times of stress/ emergency, by what factor can the adrenal medulla increase its catecholamine release?

A

100-200x the resting level of catecholamines can be released.

Physiological concepts (12 decks)

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