DEN 206: QUIZ 3

The Autonomic nervous system (ANS) automatically controls involuntary body functions, including

• Blood pressure

• Heart rate

• Breathing

• Digestion and intestinal movement

• Salivary and other glandular secretions

• Pupil size

• Bladder function

Most autonomic messages follow a two neuron pathway

• The brain or spinal cord sends an electrical signal through a PREganglionic neuron

• The PREgangleonic neuron releases acetylcholine (ACh)

• ACh crosses the synapse and binds to a nicotine receptor in a ganglion

• This starts a new electrical signal in the POSTgangleonic neuron

• The POSTgangleonic neuron releases another neurotransmitter at the target organ

• The neurotransmitter binds to a receptor, causing the organ to respond

A GANGLION is:

• a cluster of nerve cells that act as a relay station

A RECEPTOR is:

• a protein on a cell that receives the neurotransmitters message and tells the cell how to respond

PARAsympathetic system

• Nickname - Rest & Digest

• Primary purpose - Conserves energy & maintains routine function

• Origin - Brain stem & sacral spinal cord

• PREganglionic fibers - Long

• POSTganglionic fibers - Short

• PREganglionic neurotransmitter - Acetylcholine

• POSTganglionic neurotransmitter - Acetylcholine

• Target receptors - Muscarinic

SYMPathetic

• Nickname - Fight or flight

• Primary purpose - Prepares the body for stress or emergencies

• Origin - Thoracic & Lumbar spinal chord, T1-L2

• PREganglionic fibers - Short

• POSTganglionic fibers - Long

• PREganglionic neurotransmitter - Acetylcholine

• POSTganglionic neurotransmiter - Usually, norepinephrine

• Target receptors - Alpha & Beta adrenergic

The parasympathetic system supports routine body maintenance:

• Constricts the pupils

• Slows the heart rate

• Constricts the bronchioles & increases respiratory secretions

• Stimulates digestion and intentional movement

• Produces more watery saliva

• Contracts the bladder & promotes urination

The sympathetic system prepares the body to respond to stress

• Dilates the pupils

• Increases heart rate and force of contraction

• Dilates bronchioles

• Slows digestion

• Produces a smaller amount of thick, viscous saliva

• relaxes the bladder, contributing to urinary retention

• Constricts many blood vessels, increasing blood vessels

Acetylcholine

• All sympathetic PREganglionic neurons release acetylcholine (ACh). ACh binds to nicotine receptors in the sympthetic ganglia and starts the POSTganglionic nerve signal.

Norepinephrine

• Most sympathetic POSTganleonic neurons release norepinephrine at the target organ. Norepinephrine binds primarily to ALPHA & BETA adrenergic receptors.

Epinephrine

• The adrenal medulla functions like a large sympathetic ganglion. When stimulated, it releases epinephrine into the bloodstream. Epinephrine travels throughout the body and intensifies the flight or fight response.

The neurotransmitter carries the message, but

the receptor determines how the organ responds

The same neurotransmitter

Can produce different effects depending on which receptor receives it

Receptor: Nicotine

• main location/action - autonomic ganglia

• Result of stimulation - Starts the POSTganglionic nerve signal

Receptor: a1

• Main location/action - Blood vessels

• Result of stimulation - Vasoconstriction and increased blood pressure

Receptor: a2

• Main location/action - Presynaptic nerve endings

• Result of stimulation - Decreases norepinephrine release

Receptor: B1

• Main location/action - Heart

• Result of stimulation - Increases heart rate and force of contraction

Receptor: B2

• Main location/action - Lungs

• Result of stimulation - Relaxes bronchial smooth muscle and opens the airway

Receptor: B3

• Main location/action - Bladder

• Result of stimulation - Relaxes the bladder muscle & promotes urine storage

Drug: Epinephrine

• Stimulates a1, b1, & b2 receptors. It raises blood pressure, stimulates the heart, and opens the airways

Drug: Norepinephrine

• Acts mainly on a1 receptors, producing strong vasoconstriction and increasing blood pressure

Drug: Phenylephrine

• Primarily stimulates a1 receptors

Drug: albuterol & levalbuterol

• Stimulates B2 receptors and quickly open the airways

Drug: Salmeterol

• Is a long acting B2 agonist used for maintenance, not for an acute asthma attack

Drug: Clonidine

• Stimulates a2 receptors, decreasing norepinephrine release and lowering sympathetic activity

Drug: Doxazosin

• Blocks a1 receptors, allowing blood vessels to relax

Atenolol & metoprolol

• Primarily block B1 receptors and slow the heart

Drug: Propranolol & Timolol

• Block both B1 & B2 receptors, blocking B2 may narrow the airways, so these drugs require caution in patients with asthma or COPD

Epinephrine in a local anesthetic stimulates a1 receptors & causes vasoconstriction, This:

• Reduces bleeding

• Slows absorption into the bloodstream

• Keeps the anesthetic near the injection site

• Prolongs the duration of anesthesia

• Reduces the risk of systemic toxicity

Use epinephrine cautiously in pts with:

• Uncontrolled hypertension

• Unstable angina

• Uncontrolled hyperthyroidism

• Recent cocaine or meth use

• Nonselective beta-blocker therapy

Combining epinephrine with nonselective beta block can:

• Produce excessive a1 - mediated vasoconstriction and significant rise in blood pressure

Cholinergic agents are also called

• Cholinergic agonists or parasympathomimetics

Cholinergic agents

• Imitate acetylcholine or increase Cholinergic activity, they deliver additional acetylcholine messages, causing the organs to respond more strongly

Most Cholinergic agents used for xerostomia:

• Stimulate muscarinic receptors and increase parasympathetic activity

• Their effects include:

  • Increased salivary flow

  • Increased tear production

  • Slower heart rate

  • Pupil constriction

  • Increased digestion & intestinal movement

  • Increased urination

  • Bronchial constriction and increased respiratory secretions

Cholinergic Drugs: Pilocarpine (Salagen)

• Stimulates muscarinic receptors

• Increases salivary flow

• Used to treat xerostomia associated with Sjogren syndrome or head & neck radiatiation

Cholinergic Drugs: Cevimeline (Evoxac)

• Stimulates muscarinic receptors

• Increases salivary flow

• Used to treat xerostomia associated with Sjogren syndrome

Adverse reaction of Cholinergic activity produces excessive rest & digest responses

• S- Salivation

• L- Lacrimation

• U- Urination

• D- Deification

Other possible adverse effects

• Excessive sweating

• Nausea or abdominal cramping

• Diarrhea

• Urinary urgency

• Flushing

• Headache or dizziness

• Visual changes

• Bradycardia

• Hypotension

• Bronchospasm or difficulty breathing

Cholinergic Drugs may be contraindicated or require caution in patients with:

• Uncontrolled asthma

• Conditions in which pupil constriction would be unsafe

• Significant cardiovascular disease

• Peptic ulcer disease

• Urinary obstruction

• Gastrointestinal obstruction

Contradictions depend on individual drug

Cholinergic agents can be beneficial because increased salivary flow may:

• Improve speaking and swallowing

• Improve denture comfort

• Reduce oral dryness and mucosal irritation

• Help protect against caries

• Reduce the risk of oral infections associated with xerostomia

Nicotine stimulates:

• Nicotine cholinergic receptors, it is not an anticholinergic drug and is not the same type of cholinergic medication used to treat xerostomia

Initially, nicotine stimulates receptors may increase

• Heart rate

• Blood pressure

• Alertness

• Gastrointestinal

With continued or high exposure:

• The receptors can become desensitized, severe nicotine toxicity can cause respiratory muscle weakness and respiratory failure

Anticholinergic drugs are also called:

• Cholinergic antagonists or parasympatholytics

Cholinergic antagonists:

• Block acetylcholine from binding to muscarinic receptors, the nerve may still release ACh, but the target organ can not receive the message, there for rest & digest activity decreases

Blocking parasympathetic activity produces the following effects:

• Decreased salivary flow

• Increased heart rate

• Decreased digestion and intestinal movement

• Urinary retention

• Dilated pupils and blurred vision

• Decreased respiratory secretions

• Bronchodilation

Cholinergic antagonists drugs: Atropine

• Primary action/use - Muscarinic antagonist used for symptomatic bradycardia and to reduce secretions

• Important effects - Increased heart rate and causes dry mouth

Cholinergic antagonist drug: Scopolamine

• Primary action/use - Muscarinic antagonist used for motion sickness

• Important effects - Dry mouth, blurred vision and drowsiness

Cholinergic antagonist drugs: Dimenhydrinate (Dramamine)

• Primary action/use - Antihistamine with anticholinergic effects used for motion sickness

• Important effects - Dry mouth, blurred vision and sedation

Cholinergic antagonist drugs: Loperamide (Imodium)

• Primary action/use - Opioid receptor agonist that reduces intestinal movement

• Important effects - May cause constipation and dry mouth

Important*

• Lorperamide is not classified as an anticholinergic drug, it is a peripheral opioid receptor agonist, although it can produce similar effects such as reduced intestinal movement, constipation, and dry mouth

Adverse reactions to Cholinergic antagonists

• Can’t see, can’t spit, can’t pee, can’t poop (shit)

• This refers to :

  • Xerostomia

  • Urinary retention

  • Constipation

  • Dilated pupils and blurred vision

Additional adverse effects;

• Tachycardia

• Decreased sweating and heat intolerence

• Drowsiness

• Confusion

• Memory problems

• Increased risk of falls, particularly older adults

Anticholinergic drugs may be contraindicated or require caution in patients with:

• Narrow-angle glaucoma

• Urinary retention or an enlarged prostate

• Gastrointestinal obstruction or ileus

• Tachycardia or certain cardiac arrhythmias

• Myasthenia gravis

• Cognitive impairment, particularly in older adults

Contradictions vary by drug and dose

Xerorostomia is the most important dental effect, reduced saliva increases the risk of:

• dental caries

• root caries

• candidiasis

• mucosal soreness

• difficulty swallowing, chewing or speaking

• halitosis

• Denture discomfort

Management may include:

• Frequent water intake

• Sugar-free xylitol-containing gum or lozenges when appropriate

• Saliva substitutes

• Prescription strength fluoride

• Careful plaque control

• More frequent caries assessments and preventative visits

Anticholinergic drugs with a hygienist

• Should monitor patients’ pulse and blood pressure when appropriate and assess for dizziness, confusion, blurred vision or excessive sedation

Adrenergic agents are also called:

• Adrenergic agonists or sympathomimetics imitate norepinephrine or epinephrine and increase fight-or-flight activity

Pharmacologic effects:

• Depending on the receptor stimulated, adrenergic agents may:

  • Increase heart rate and force

  • Constrict blood vessels

  • Raise blood pressure

  • Dilate the bronchioles

  • Dilate the pupils

  • Decrease digestion

  • Redirect blood toward skeletal muscle

Adrenergic drug: Epinephrine

• Primary receptor - a1, b1, b2

• Main use or effect - Anaphylaxis, cardiac arrest, dental local anesthetics

Adrenergic drug: Norepinephrine

• Primary receptor - Primarily a1 with some b1

• Main use or effects - Severe hypotension and septic shock

Adrenergic drug: Phenylephrine

• Primary receptor - a1

• Main use or effects - Raises blood pressure and relieves nasal congestion

Adrenergic drug: Dopamine

• Primary receptors - b1, a1 at higher doses

• Main use or effect - Supports the heart and raises blood pressure in shock

Adrenergic drug: Albuterol

• Primary receptor - b2

• Main use or effect - Rapid relief bronchospasm

Adrenergic drug: Levalbuterol

• Primary receptors - b2

• Main use or effect -Rapid relief of bronchospasm

Adrenergic drug: Salmeterol

• Primary receptor - b2

• Main use or effect - Long term asthma or COPD maintenance

Chapter 4 core summary:

• Cholinergic agonist - increases ACh activity - more rest & digest , more saliva

• Anticholinergic drug - blocks muscarinic receptors - less rest & digest - dry mouth and increased heart rate

• Adrenergic agonist - activates fight-or-flight messages - heart rate or blood pressure decreases

• The receptor determines the response - a1 squeezes blood vessels, b1 stimulates the heart and b2 opens the lungs

What do neuromuscular blocking agents do

• block communication between nerves and skeletal muscles, causing temporary muscle paralysis and relaxation

The main reason to balance general anesthesia

• Combines drugs that target different goals so that each can be given at a lower dose

Guedel stages of anesthesia

• Stage I - II: Transition to unconsciousness

  • Stage I: Analgesia/Disorientation: Begins with anesthetic administration and ends with loss of consciousness; breathing is regular, and protective reflexes are intact

  • Stage II: Excitment/delerium: Runs from loss of consciousness to automatic regular breathing; irregular respiration, involuntary movement, vomiting, laryngospasm, heightened reflexes may occur (spasmodic movements)

  • Clinical goal: Pass through stage II rapidly rather than maintaining the patient there

• Stage III: Surgical anesthetic depth (4 planes)

  • Plane I: Regular spontaneous breathing; eyelid, conjunctival, and swallowing reflexes disappear

  • Plane II: Corneal and laryngeal reflexes are lost; muscle relaxation and respiratory depression increase

  • Plane III: Intercostal and abdominal muscle paralysis progresses, producing shallow respiration

  • Plane IIII: Intercostal paralysis is complete; diaphragmatic breathing remains but is profo

• Stage IV: Overdose - never a target: Medullary depression causes apnea, severe hypotension or circulatory failure, and fixed dilated pupils; immediate resuscitation is required

Preferred three drugs for general anesthesia

• Propofol (Most Common) - Rapid, smooth induction and maintenance; common adverse effects are hypotension and apnea; it provides no analgesia (no pain relief)

• Etomidate: Rapid induction with relatively little cardiovascular depression; it may cause myoclonus (spasms) and adrenal suppression; no analgesia

• Ketamine (Little bit of everything): Dissociative anesthesia with analgesia; spontaneous breathing and blood pressure are often preserved, but respiratory events can occur; secretions and emergence reactions are possible

Why the other drugs discussed are not the first choice

• they carry higher risks of side effects, potential for dependence, or complex safety profiles compared to first-line treatments