ANS

Autonomic Nervous System Overview

  • Welcome and Introduction

    • Recorded discussion focusing on the autonomic nervous system (ANS).

    • Importance of memorization for understanding the ANS.

Nervous System Structure

  • Composition of the Nervous System

    • Central Nervous System (CNS) compared to the Peripheral Nervous System (PNS).

    • Components of the PNS include the somatic system and the autonomic nervous system.

Somatic Nervous System

  • Voluntary control of striated muscles.

    • Movement and actions that are under conscious control.

Autonomic Nervous System

  • Definition: Involuntary functions like breathing and heartbeat; automatic functioning.

  • Divisions of the ANS:

    • Sympathetic Nervous System: Initiates fight or flight responses, dealing with stress and danger.

    • Parasympathetic Nervous System: Responsible for rest and digest functions, maintaining homeostasis.

Sympathetic Nervous System

  • Function and Purpose

    • Regulates cardiovascular functions and body temperature.

    • Physiological response includes increased heart rate, blood pressure, and blood flow to vital organs during a perceived danger.

    • Enhanced functions such as bronchodilation (dilation of bronchi) and mobilization of glucose for energy during crisis.

  • Triggers

    • Illness and psychological stress can also elicit sympathetic responses.

  • Illustration: Example of stress-induced responses compared to a threatening scenario (e.g., bear chasing).

Parasympathetic Nervous System

  • Purpose and Function

    • Known as the "rest and digest" mechanism; maintains homeostasis and performs daily housekeeping functions.

  • Effects on the body

    • Allows the body to conserve energy and resources during non-stressful situations.

Neurotransmitters

  • Definition: Chemical messengers transmitting signals from nerve cells to target cells (muscle, glands, organs).

  • Essential functions regulated by neurotransmitters:

    • Heart rate, breathing, sleep cycles, digestion, mood, concentration, appetite, muscle movement.

Key Neurotransmitters

  • Acetylcholine (ACh):

    • Main neurotransmitter for preganglionic messages in both sympathetic and parasympathetic systems.

    • Postganglionic messages in the parasympathetic and somatic systems relating to muscles.

  • Norepinephrine (NE) and Epinephrine (E):

    • Primary neurotransmitters for postganglionic messages in the sympathetic nervous system.

Sympathetic Receptors

  • Alpha Receptors:

    • Alpha 1: Located in blood vessels, prostate, urinary sphincter; responsible for vasoconstriction.

    • Alpha 2: Also involved in feedback inhibition of norepinephrine release.

  • Beta Receptors:

    • Beta 1: Located in the heart, kidney, and eye; increases heart rate and renal function.

    • Beta 2: Located in lungs, airways, liver, and uterus; allows bronchodilation and metabolic effects.

  • Necessity for memorization of these receptor types.

Organ System Interactions

  • Receptors chart comparing sympathetic and parasympathetic effects.

  • Examples of how sympathetic responses enhance visibility, oxygenation, and perfusion through dilation of bronchioles and increasing heart rate in situational stress.

Pharmacological Considerations

Adrenergic Drugs

  • Terms and Identifications

    • Description of sympathetic drugs can include terms like sympathomimetic, adrenergic drugs, etc.

  • Epinephrine:

    • Important emergency drug; acts on all alpha and beta receptors.

  • Blockers:

    • Alpha and beta blockers; prevent receptor activation in therapy for cardiovascular issues.

    • Propranolol: Non-selective beta blocker; inhibits both beta-1 and beta-2 receptors.

    • Metoprolol: Selective beta-1 blocker; affects heart rate without targeting beta-2.

    • Terazosin: Alpha blocker used for BPH and hypertension treatment.

Common Uses and Effects of Adrenergic Drugs

  • Shock Management:

    • Alpha agonists increase blood pressure.

    • Beta agonists increase heart rate and support perfusion.

  • Emergency Situations:

    • Anaphylaxis treatment, increasing blood pressure and facilitating breathing.

  • Side Effects of Adrenergics:

    • Anxiety, increased heart rate, palpitations, hyperglycemia.

    • Caution in populations with existing hypertension, pregnant patients, or in elderly patients.

Cholinergic Drugs

  • Definition: Drugs affecting the parasympathetic nervous system (rest and digest).

  • Mechanism of action promotes functions like urination and gastrointestinal activity.

  • Uses:

    • Urinary retention, glaucoma management, enhancing GI peristalsis.

  • Signs of Toxicity:

    • SLUDGE (Salivation, Lacrimation, Urination, Diarrhea, Gastrointestinal distress, Emesis).

  • Antidote: Atropine for cholinergic crisis.

Anticholinergic Drugs

  • Functionality and Uses

    • Block cholinergic effects, promoting relaxation of smooth muscles; relevant in conditions like COPD, IBS, and pre-procedural medication.

  • Examples: Atropine, Scopolamine, Bentyl.

  • Considerations in patients with glaucoma or BPH due to risks of urinary retention and increasing intraocular pressure.

Nursing Responsibilities

  • Importance of monitoring vital signs during drug administration and evaluating therapeutic outcomes.

  • Knowledge of patient conditions affecting drug efficacy and safety such as BPH or glaucoma.