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Pharmacology > Lecture 2: Autonomic Nervous System > Flashcards

Lecture 2: Autonomic Nervous System Flashcards

1
Q

Define agonist and antagonist.

A

Agonist: binding of drug to receptor results in a response

Antagonist: binding of drug to receptor is not associated with a response. The drug has an effect only by preventing an agonist from binding.

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2
Q

Compare competitive and non-competitive antagonists.

A

Competitive antagonist: binding of the drug to receptor is reversible and the drug competes with an agonist for the binding site

Non-competitive antagonist: the drug opposes the action of an agonist but does so without competing with it for the binding site. The agonist may bind, but will not have an effect.

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3
Q

Affinity?

A

Ability/strength with which a drug will bind to a receptor

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4
Q

Potency?

A

The amount of a dose required to produce a particular effect. The potency compares the relative dose of various agonists required to produce the same magnitude of effect.

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5
Q

Efficacy?

A

The maximum effect an agonist can achieve. This can also be described as the capacity of a drug to achieve a therapeutic effect.

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6
Q

What are the two major divisions of the nervous system? Describe each.

A

CNS (central) and PNS (peripheral)

CNS

  • Consists of brain, brain stem and spinal cord
  • Processing center for nervous system
  • Receives information from and sends info to the PNS

PNS

  • All of the nervous system that is located outside of the CNS
  • Subdivided into autonomic and somatic systems
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7
Q

What is the function of the somatic nervous system? What are the anatomical components?

A

It is responsible for transmitting sensory information as well as for voluntary movement. It consists of cranial and spinal nerves.

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8
Q

Define the two major types of neurons in the SNS.

A

Sensory neurons (afferent) - carry information from the nerves to the CNS

Motor neurons (efferent) - carry information from brain and spinalcord to skeletal muscle fibers throughout the body

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9
Q

Define the autonomic nervous system. Give examples of activities it is in control of.

A

The part of the PNS responsible for regulating involuntary body functions. It is under subconscious (autonomic) control.

It controls breathing, visceral function, blood pressure, gut motility and secretions by innervating cardiac and smooth muscle, glands and GI neurons.

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10
Q

What are the main actions of the sympathetic nervous system?

A
  • Heart rate increase
  • Blood pressure increase
  • Digestion decrease
  • Secretions decrease
  • Airways open
  • Pupils open/dilate (mydriasis)
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11
Q

What are the main actions of the parasympathetic nervous system?

A
  • Heart rate decrease
  • Blood pressure decrease
  • Digestion increase
  • Secretions increase
  • Airways constrict
  • Pupils constrict (miosis)
  • Emptying of bowel and bladder
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12
Q

What are the six neurotransmitters most commonly involved in the actions of therapeutically useful drugs? Which two are primary in the ANS?

A
  1. Acetylcholine
  2. Dopamine
  3. Epinephrine
  4. Histamine
  5. Norepinephrine
  6. Serotonin

Acetylcholine and norepinephrine are the primary two for ANS.

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13
Q

Describe what neurotransmitters are released at pre and post-ganglionic neurons for the parasympathetic and sympathetic nervous systems. (Most of the time).

A

Parasympathetic nerves release acetylcholine in the ganglion as well as at their target end organs and receptors.

Sympathetic nerves release acetylcholine in the ganlgion and norepinephrine at their target end organs and receptors.

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14
Q

What is the exception to the norm for sympathetic postganglionic NT?

A

Muscarinic receptor of sweat gland responding to Ach under control of sympathetic system. This is uncommon. Most sympathetic receptors are alpha and beta and respond to NE.

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15
Q

Compare the lengths of pre and post-ganglionic fibers for sympathetic vs parasympathetic.

A

Pre-ganglionic fibers are short for sympathetic neurons and long for parasympathetic. Post-ganglionic fibers are long for sympathetic (allowing for a diffuse response) and short for parasympathetic (allowing for a targeted, localized response).

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16
Q

Describe the effects of curare on the nervous system.

A
17
Q

Describe the different kinds cholinoceptors.

A

Cholinergic receptors or cholinoceptors are activated by ACh and include nicotinic and muscarinic receptors.

Muscarinic receptors are found at parasympathetic post-ganglionic organs/receptors and sympathetic sweat glands.

Nicotinic receptors are found in ganglia and in the somatic nervous system on skeletal muscle.

18
Q

Describe direct acting vs indirect acting cholinergic agonists.

A

Direct acting are formulated to activate muscarinic receptors.

Indirect acting increase the availability of acetycholine at cholinergic receptors. An example would be anti-cholinesterases to prevent the breakdown of ACh.

19
Q

Describe direct cholinomimetics and their cardiovascular effects.

A

Direct stimulation of muscarinic and nicotinic receptors (end organ muscarinic).

Cardiovascular effects: Decreased heart rate and contractility. Decreased blood pressure.

20
Q

Describe all of the other cholinomimetic effects on the body.

A

Bronchioles: contrict

Bladder: muscles constrict, sphincters relax = urination

GI Tract: rest and digest

Salivary: secretions increased

Eye: Pupil constricts, reduced light entering eye, near vision

21
Q

What are some potential adverse effects of cholinomimetic drugs?

A
  • Actions too intense: eg. GI tract motility leading to diarrhea
  • Non-intended actions: bronchoconstriction producing an asthma attack when drug given for atonic bladder
  • Normal compensatory reactions not available for some time after administration: eg. drugs given to constrict the pupils, cannot accomodate to see distant objects or to see in the dark.
22
Q

In what circumstances would cholinomimetic drugs be contraindicated?

A

Drugs are contraindicated in patients with pre-existing conditions that could be exacerbated.

Examples:

  • Severe asthma
  • Parkinson’s
  • Bradycardia and/or hypotension
  • Incontinence
  • Peptic ulcers
23
Q

Describe the actions of anticholinergic or parasympatholytic drugs.

A

Direct acting: Block muscarinic receptors

Indirect acting: Decrease amount of ACh in the synaptic cleft (eg. block creation, block release, increase acetylcholinesterase, decrease or block AChesterase inhibitors

24
Q

Can anticholinergics cross the blood brain barrier? Describe general adverse effects of anticholinergics.

A

Yes they can. This may cause confusion and incoherence.

Adverse effects:

  • Hot as a hare (inhibition of sweating as well as tachycardia increases body tempearture)
  • Blind as a bat (pupils dilated too much, difficult to focus)
  • Red as a beet (body temp, increase in vasodilation)
  • Dry as a bone (inhibition of secretions and sweating)
  • Mad as a hatter (confusion and incoherence from crossing BBB)
25
Q

Talk about the release of epinephrine and norepinephrine. What receptors do they act on?

A

Epinephrine (adrenaline) - generally released systemically from the adrenal medulla in response to stressful stimuli

Norepinephrine (noradrenaline) - released from neurons in the sympathetic nervous system.

Both act on adrenergic receptors throughout the body.

26
Q

What are the four types of adrenergic receptors?

A

Alpha-1

Alpha-2

Beta 1

Beta 2

27
Q

Describe the location and function of Alpha 1 receptors.

A

Found on postsynaptic effector cells such as those on the smooth muscles of the vascular, genitourinary, intestinal, and cardiac systems and in the liver.

Functions:

  • Vasoconstriction at most vascular beds
  • Increased glycogenolysis in the liver
  • Mydriasis (pupil dilation)
  • Constriction of internal sphincter of bladder
28
Q

Describe the location and function of Alpha 2 cells.

A

Found on presynaptic neurons in the brainstem and the periphery.

Functions:

  • Lead to negative feedback and inhibtion of norepinephrine release.
  • Inhibition of insulin release
29
Q

Describe the location and function of Beta 1 receptors

A

Found on the heart, the kidney, and the fat cells.

Functions:

  • Heart - increase the force and rate of contraction
  • Kidney - renin release
  • Fat cells - lipolysis
30
Q

Describe the location and function of Beta 2 receptors.

A

Predominantly present on airway smooth muscles. (Also exist on cardiac muscles, uterine muscles, alveolar type II cells, mast cells, mucous glands, epithelial cells, vascular endothelium, eosinophils, lymphocytes, and skeletal muscles).

Functions:

  • Vasodilation of skeletal muscle and coronary vessels
  • Bronchodilation
  • Increased glucagon release
  • Increased glycogenolysis (muscle)
  • Relaxation of smooth muscle
31
Q

Describe the effect of epinephrine (adrenaline) on adrenergic receptors. Why would it be used during anaphylactic shock?

A

Function: Activates all alpha and beta receptors

Anaphylactic shock - bronchodilation and vasoconstriction to elevate blood pressure

32
Q

How is epinephrine an adjunct to local anesthetics?

A

It causes vasoconstriction and keeps the effect local.

33
Q

How does epinephrine help in acute cardiovascular collapse?

A

Stimulates heart and elevates BP.

34
Q

How does epinephrine help with glaucoma?

A

Vasoconstriction in ciliary body decreases aqueous humour production. Pupil dilation can decrease flow through the canals of Schlemm

35
Q

–A 12-year-old girl presents to the office with a sore throat and fever. She is diagnosed with Strep throat, and is given an IM injection of penicillin. Approximately 5 minutes later, she is found to be in respiratory distress and audibly wheezing. Her skin is mottled and cool, she is tachycardic (rapid heart rate), and her blood pressure has fallen to 70/20 mmHg. You immediately diagnose her as having an anaphylactic reaction to the penicillin and give a subcutaneous injection of epinephrine.

•Case Questions:

–What effect will epinephrine have on this patient’s vascular system?

•Which adrenoceptor primarily mediates the vascular response?

–What effect will epinephrine have on her respiratory system?

•Which adrenoceptor primarily mediates the respiratory system response?

A

Raise blood pressure through vasoconstriction. This is mediated primarily through Alpha-1.

Bronchodilation mediated by receptor Beta-2

36
Q

Postganglionic neurons of the sympathetic division that innervate thermoregulatory sweat glands are

  • A) adrenergic.
  • B) cholinergic.
A

B) Cholinergic

37
Q
  • Which of these functions is NOT affected by parasympathetic stimulation?
  • A) secretion of tears
  • B) secretion of sweat
  • C) secretion of insulin from the pancreas
  • D) secretion of thin, watery, saliva
  • E) secretion of digestive glands
A

B) Secretion of sweat

Pharmacology (5 decks)

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