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Anesthesiology > Peripheral Nervous System > Flashcards

Peripheral Nervous System Flashcards

1
Q

Discuss properties of A-beta fibers

A

A-beta fibers are myelinated second largest fibers responsible for proprioception, touch, and pressure

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2
Q

Discuss properties of A-alpha fibers

A

A-alpha fibers are myelinated large fibers with fast conduction speeds.

The motor (efferent) control muscle length and force of contraction

The sensory (afferent) control proprioceptin

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3
Q

Discuss the properties of a-gamma fibers

A

A-gamma fibers are myelinated 3rd largest fibers responsible for skeletal muscle tone

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4
Q

Discuss properties of a-delta fibers

A

A-delta fibers are myelinated small fibers responsible for temperature and sharp prickling pain sensation

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5
Q

Discuss B fibers

A

B fibers are myelinated preganglionic autonomic neurons responsible for various autonomic functions

First fibers to be blocked by LA

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6
Q

Discuss sC fibers

A

sC fibers are small unmyelinated postganglionic sympathetic neurons responsible for various autonomic functions

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7
Q

Discuss dC fibers

A

dC fibers are small unmyelinated afferent (sensory) neurons responsible for temperature and throbbing pain

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8
Q

List the different nerve fiber type in order of size and conduction speed.

A

A-alpha, A-beta, A-gamma, A-delta, B, sC, dC

Nerves with LARGER diameter conduct AP faster than fibers with smaller diameter

Myelinated fibers conduct AP faster than unmyelinated fibers

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9
Q

Discuss the anatomy of the sympathetic nervous system

A

The sympathetic thoracholumbar nervous system arises from T1-L2(3) and the cardio accelerator fibers are from T1-T4

Most sympathetic presynaptic neurons synaps with post ganglionic fibers at the paravertebral ganglia formed by the inferior cervical and first thoracic ganglia

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10
Q

What are the S/S if Horners syndrome?

A

Ipsilateral miosis, ptosis, flushing, increased skin temperature, enophathalamos, and nasal congestion due to stellate ganglion blockade.

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11
Q

Discuss where sympathetic preganglionic fibers arise and how the intersect the white and gray rami communicans

A

Sympathetic preganglionic fibers arise from the intermediolateral horn of the spinal cord. All Sympathetic PREganglionic fibers pass though the white rami, while some but not all POSTganglionic fibers pass through the grey rami. PREganglionic white rami are distributed to spinal nerves from T1-L2. Gray rami are distributed to ALL spinal nerves from the ganglia. Gray rami allows coordinated massive discharge of the sympathetic nervous system

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12
Q

Describe the synthesis of epinephrine

A

Tyrosine -> dopa -> dopamine -> norepinephrine -> epinephrine (only in adrenal medulla)

Norepinephrine is stored in presynaptic vesicles. In the adrenal medulla NE is 20% and Epi is 80% of totals storage

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13
Q

Describe events of sympathetic neurotransission

A

1) AP arrives at sympathetic nerve terminal
2) Depolarization opens Ca+ channels and ca+ rushes into cell.
3) Ca+ unites with calmodulin to cause NE filled vesicles to merge with cell membrane and spill NE into synaptic cleft
4) presynaptic alpha 2 receptors activated by NE cause a decrease in NE release (neg feed back loop)
5) NE diffuses down concentration gradient to post synaptic membrane receptors
6) adrenergic receptor activation causes ion channels to open, or activation of adenylate cyclase
7) NE diffuses away from receptors (1st step in termination) NE is actively reuptaken inside presynaptic terminal (80%) small amounts are metabolized by MAO in the synaptic cleft, and small amounts diffuse into the blood stream and are metabolized by COMT

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14
Q

Sympathetic nervous system activation acts to:

A

Increase HR, CO, BP, blood glucose, dilate bronchial tree, shunt blood away from intestine and viscera to supply skeletal muscle

Flight or flight

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15
Q

Discuss location and activity of alpha-1 receptors

A

Alpha-1 receptors are found a variety of tissues (vascular smooth muscle, glands) and are inervated by sympathetic postganglionic neurons. Stimulation is usually excitatory

Arterial and venous constriction, increased preload, SV, CO,and BP

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16
Q

Discuss location and actively of alpha-2 receptors

A

Found on PREsymaptic nerve terminals of sympathetic postganglionic neurons, but also found in post synaptic membranes of brainstem and peripheral tissue.

stimulation of sympathetic postganglionic, presynaptic nerve varicosities inhibits the release of NE (neg feed back loop). Stimulation of postsynaptic receptors in the brainstem inhibits sympathetic outflow.
Stimulation of receptors in the substantial gelatinosa of the spinal cord promotes analgesia

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17
Q

Discuss location and function of beta-1 receptos

A

found in heart, kidney, and adipose tissue. Stimulation is excitatory –> increased HR, CO, contractility –> increased CO and BP

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18
Q

Discuss location and function of beta-2 receptors

A

Found in smooth muscle and in glandular tissue. Stimulation is inhibitory –> vasodilitation, bronchodilation, relaxation of pregnant uterus, glycogenolysis, and gluconeogenisis.

beta-2 receptor stimulation promotes hyperglycemia, and hypokalemia

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19
Q

Discuss the renin-angiotensin-aldosterone System

A

85% of resting BP Is controlled by renin.

In response to low BP the kidney releases renin –> converting angiotensinogen ( produced in the liver) into angiotensin-I, in the lungs ACE converts angiotensin-I to angiotensin-II –> causes vasoconstriction, and release of aldosterone from adrenal gland, aldosterone promotes K+ excretion in exchange for Na+ retention, Na+ retention results in fluid expansion and combined with vasoconstriction in increased BP

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20
Q

Phenylephrine

A

Alpha-1 +++

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21
Q

Clonidine

A

Minimal alpha-1 with strong alpha-2

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22
Q

Isoproterenol

A

Strong beta-1 and beta-2

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23
Q

Doubutamine

A

Strong beta-1

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24
Q

Terbutaline

A

Minimal beta-1 strong beta-2

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25
Q

Ritodrine (yutopar)

A

Minimal beta-1 strong beta-2

26
Q

Epinephrine

A

Strong alpha-1, weak alpha-2 strong beta-1and beta-2

Leads to increased SBP (beta-1), decreased DBP (beta-2 vasodilation more pronounced than alpha-1 constriction at low doses), an increased in HR (beta-1) MAP is variable

27
Q

Norepinephrine

A

Alpha-1 alpha-2 and beta-1

Leads to increased SBP (beta-1) increased DBP (alpha-1) and increased MAP

28
Q

Dopamine

A

Alpha-1, alpha-2, beta-1 and minimal beta-2

29
Q

Ephedrine

A

Indirect acting, strong alpha and weak beta

30
Q

Metarminol (aramine)

A

Indirect acting, strong alpha and wean beta

31
Q

Sympathetic stimulation of heart

A

Beat-1
SA node increase HR
AV node increase conduction
Muscle fibers increase contractility

32
Q

Sympathetic stimulation of arterial blood vessels

A

Alpha-1
Vasoconstriction and inc. SVR in most systemic blood vessels

Beta-2
Vasodilation and decreased SVR in skeletal muscle vessels

33
Q

Sympathetic stimulation of veins

A

Alpha-1

Vasoconstriction increased preload

34
Q

Sympathetic stimulation of lungs

A

Beta-2

Bronchodilation and increased secretions

35
Q

Sympathetic stimulation of kidney

A

Beta-1
Increased renin release

Alpha-1
Decreased renin release

36
Q

Sympathetic stimulation of Liver

A

Beta-2
Gluconeogenisis
Glycogenolysis

37
Q

Sympathetic stimulation of uterus

A

Beta-2
Muscle relaxation

Alpha-1
Contraction

38
Q

Sympathetic stimulation of Na-K ATPase pump

A

Beta-2

Hypokalemia

39
Q

What are the side effects of Ritodrine (Yutopar)

A

Tachycardia, Hypokalemia, hyperglycemia (ketoacidosis is a risk in insulin dependent diabetics), and pulmonary edema

Crosses placenta side effect to fetus

40
Q

What are the actions and uses of Phenoxybenzamine (Dibenzyline)?

A

Phenoxybenzamine, is a long acting non-selective alpha-adrenergic antagonist it is used to control BP in patients with pheochromocytoma

41
Q

What are the uses and action of Yohimbine?

A

Yohimbine is a selective alpha-2 adrenergic antagonist used to treat ED

42
Q

What are the uses and action of timolol

A

Non-selective beta-1and beta-2 antagonist

43
Q

What are the uses and action of propranolol?

A

Non-selective beta antagonist.

Generally to be avoided in patients with irritable airways due to possible bronchoconstriction

44
Q

What are the uses and action of Esmolol

A

Non-selective beta blocker, very short acting because it’s metabolized by plasma non-selective esterases

45
Q

What are the uses and action of Labetalol?

A

Competitive antagonist at alph-1 and beta-1 and beta-2. Alpha to beta 1:7

May be used to TX hypertensive emergencies or to produce controlled hypotension. Decreases HR, contractility, and SVR

46
Q

Discuss the anatomy of the parasympathetic nervous system

A

The parasympathetic craniosacral nervous system out flow arrives from

Oculomotor cranial nerve (III) from midbrain
Facial cranial nerve (VII) from the pons
Glossopharyngeal nerve (IX) from medulla
Vagus nerve (X) from medulla
S2-S4
47
Q

What are the responses to Parasympathetic stimulation to the eye.

A

The pupil constricts (miosis)

48
Q

What are the responses to Parasympathetic stimulation to the heart?

A

Decreased HR, conduction speed, contractility

49
Q

What are the responses to Parasympathetic stimulation to smooth muscle

A

Bronchoconstriction, gallbladder contraction, increased motility, contraction of bladder destructor muscles

50
Q

What is the effect on secrearions in response toare the Parasympathetic stimulation?

A

Increased salivary, pharyngeal, laryngeal and bronchial secretions. Increased gastric acid secretions. Increased secretions of digestive enzymes and bicarbonate from pancrease and small intestine

51
Q

What the action of pilocarpine and what is it used for

A

Pilocarpine is a parasympathetic used to treat some forms of glaucoma

52
Q

What are the cholinesterase inhibitors?

A 
Endrophonium (Tensilon)
Neostigmine (prostigmin)
Pyridostigmine (Mestinon, Regonol)
Physostigmine (Antilirium)
Echothoiphate (Echodide, Phospholine)
53
Q

What is the mechanism of action of the cholinesterase inhibitors and what are they used for?

A

Cholinesterase inhibitors inhibit both true AchE and plasma AchE. Since true AchE is found postsynaptically these agent have postsynaptic activity. They act indirectly by raising the concentration of Ach.

Muscarinic effects: bradycardia, increased gastry secretions, hyperperistalsis, miosis, salivation
Nicotinic effects: stimulation of autonomic ganglia and neuromuscular junction

Uses: NMB reversal, tx anticholinergic syndrome, myasthenia gravis, Alzheimer’s, ileus, glaucoma, atonic bladder

54
Q

What is the significance of the effect that cholinesterase inhibitors have on plasma AchE?

A

Neostigmine and pyridostigmine but not endrophonium, produce marked prolonged inhibition of plasma AchE. Succinylcholine and mivacurium would have prolonged effects. A result.

55
Q

What is cholinergic syndrome and how is it treated?

A

Cholinergic syndrome can be a result of organic pesticides, “nerve gas”, or excess physostigmine. Symptoms include:

Muscarinic: Miosis, difficulty focusing, salivation, bronchoconstriction, bradycardia, ABD cramps
Nicotinic: Weakness mild to paralysis
CNS: dysphoria, confusion, ataxia, seizure, coma

Treatment: atropine, pralidoxime (reactivates Ach) and diazepam for seizures

56
Q

How will excessive doses of acetycholinesterase inhibitors effect nondepolarizing neuromuscular blocked?

A

In excess doses acetycholinesterase inhibitors can paradoxically potentate the blockade

57
Q

What are the antimuscarinic agents and what is their mechanism of action?

A

Atropine, scopolamine and glycopyrolate combine with muscarinic receptors and prevent Ach from interacting with the receptors, acting as competitive inhibitors

Lead to responses opposite those seen with parasympathetic stimulation

58
Q

What is anticholinergic syndrome and how is it Tx?

A

Anticholinergic syndrome may develop in response to high doses of atropine or scopolamine.

Central manifestations include: mania, hallucinations, delirium, drowsiness, come, agitation, disorientation.
Peripheral manifestations include: blurred vision,dry mouth, tachycardia, flushed skin, rash over face and neck, and hypotension.

Pediatric and elderly most sensitive

Tx with physostigmine 15-60mcg/kg IV (lipid soluble and will cross BBB)

59
Q

What is the effect of antimuscarinic agent on esophageal sphincter tone?

A

Tone is decreased –> increasing the likelihood of reflux

60
Q

Describe the process of bronchial smooth muscle relaxation via beta-2 stimulation

A

1) First messenger (ie Terbutaline) binds to beta-2 receptor
2) Gs activates adenylate cyclase
3) adenylate cyclase transforms ATP to cAMP ( second messenger)
4) cAMP activates protein kinase resulting in Bronchodilation
5) phosphodiesterase breaks down cAMP ending dilation

Phosphodiesterase inhibitors such as aminophylline block the breakdown of cAMP therefore promoting dilation

61
Q

Describe the process of bronchial smooth muscle relaxation via nitric oxide

A

1) First messenger Nitric oxide diffuses into cell
2) NO activates GTP into cGMP resulting in Bronchodilation

Nitroglycerin and nitroprusside promote bronchodilation by donating NO and increasing cGMP

62
Q

Describe the process of bronchial smooth muscle constriction via muscarinic activation

A

1) Ach bings to muscarinic receptor activating protein G
2) Protein G activates phospholipiase-C transforming PIP into IP3
3) IP3 stimulates release of intracellular Ca+ stores into the sarcoplasm activating the contractile mechanism

Atropine and the inhaled antimuscarinic agent ipratropium (atrovent) produce Bronchodilation by competitively inhibiting muscarinic receptors

Anesthesiology (5 decks)

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