Autonomic Nervous System Chapter 16, 17, 18, 19, 20 Clinical Drug Therapy
Nervous System • Two main divisions • Central Nervous System or CNS • Peripheral Nervous System or PNS
Central Nervous System or CNS • Brain and spinal cord: receives and processes incoming sensory information and responds by sending out signals that initiate or modify a process.
Peripheral Nervous System or PNS • Includes all the neurons and ganglia found outside the CNS • Afferent (sensory): modify motor output • Efferent:
Afferent Neurons • Afferent neurons carry sensory input from the periphery to the CNS and modify motor output through the reflex arc.
Efferent Neurons • Efferent neurons carry motor signals from the CNS to the peripheral areas of the body.
ANS / SNS • Autonomic nervous system controls involuntary activities of smooth muscle, secretory glands and the visceral organs of the body such as the heart (involuntary activities of smooth muscle) • Somatic nervous system innervates the skeletal muscles and controls voluntary movement
Autonomic Nervous System • Sympathetic Nervous System • Para sympathetic System • Enteric System
The Race Horse and the Cow Sympathetic Nervous System Parasympathetic
Sympathetic System • Fight or Flight – stimulated by physical or emotional stress (exercise or work), pain, hemorrhage, intense emotions, temperature extremes
Sympathetic Nervous System • Protective mechanisms designed to help person cope with the stress or get away from it.
Neurotransmitters • Neurotransmitters • Acetylcholine: skeletal muscle • Norepinepherine: stress response
Norepinephrine and epinephrine • Both always present in the blood. • Norepinephrine varies according to the amount of stress present and will cause transient changes in heart rate and systemic arteries and veins. • Epinephrine is a constant in regulating heart rate, vasoconstriction in systemic arteries and veins and vasodilation of muscles and liver.
Dopamine • Adrenergic neurotransmitter – essential for normal brain function. • Studies focus on connection between dopamine malfunction in schizophrenia and Parkinson’s Disease. • Role of dopamine in drug addition to drugs: stimulants and depressants.
Protective Mechanisms • Intensity of response depends on Norepinephrine and epinephrine • Fight or flight
Body Responses • Increase in blood pressure and cardiac output. • Increase blood flow to brain, heart and skeletal muscles. • Decrease blood flow to skin and organs not needed for “flight”. • Increase in glycogen for energy, mental activity, muscle strength, blood coagulation, respiratory rate, pupil dilation to aid vision, and increase in sweating.
Fight of Flight Response • Can be a problem if the body stay in the “fight or flight” mode. • Type A personalities? • High stress environment? • Medications may be needed reduce the physiologic body responses.
Parasympathetic Nervous System Rest and Digest Save energy Decreased heart rate
Adrenergic Receptors • Norepinephrine and epinephrine interact with two adrenergic receptors • Alpha and beta • Alpha 1 • Alpha 2 • Beta 1 • Beta 2
Alpha 1 • Alpha 1 receptors allows calcium ions to move into the cell and produce muscle contraction.
Location Blood vessels Kidney Intestinal smooth muscles Genitourinary Eyes = blinking Pregnant uterus = contractions Male sexual organs = sexual function Effects of stimulation Vasoconstriction Release of renin (kidney) Relaxation Alpha 1
Location Nerve endings Vascular smooth muscles Pancreatic beta cells Platelets Effects of stimulation Inhibits release of Norepinephrine Vasoconstriction Inhibit insulin secretion Aggregation or clotting Alpha 2
Location Heart Kidneys Effects of stimulation Increase heart rate, force of contraction, automaticity and rate of atrial-ventricular function Increased renin release Beta 1
Location Bronchioles Blood vessels Gastrointestinal tract Liver Urinary bladder Pregnant uterus Effects of stimulation Vasodilation Decreased motility and tone Glycogenolysis Relaxed detrusor muscle (bladder muscle) Relaxation of uterus Beta 2
Location Blood vessels of kidney, heart, and other viscera Effects of stimulation Vasodilation Dopamine
Parasympathetic Nervous System Functions stimulated by PNS: Resting, reparative, or vegetative function
Body Responses • Dilation of blood vessels in skin • Decrease heart rate (bradycardia) • Increase secretion of digestive enzymes • Constriction of smooth muscle of bronchi • Increase in sweat glands • Contraction of smooth muscles of urinary bladder • Contraction of smooth muscle of skeletal system
Neurotransmitter • Acetylcholine • Two types of cholinergic receptors • Nicotinic: located in motor nerves and skeletal muscles • Muscarinic: located in internal organs, cardiovascular, respiratory, GI and GU
Autonomic Drugs • Drugs used due to their ability to stimulate or block activity of the sympathetic or parasympathetic nervous system.
Effect of Drugs • Drugs that act of ANS usually affect the entire body. • Effects depend on whether you are trying to stimulate or inhibit function.
Receptor Activity • Drugs are developed to stimulate or inhibit particular subtypes of receptors. • More selective on particular body tissues. • Decrease adverse effects on other body tissues – side effects.
Simulation of SNS • Stimulation of sympathetic nervous system can be divided into drug classifications: • Adrenergic • Sympathomimetic • Alpha and beta adrenergic agonists
Agonist • In pharmacology an agonist is a substance that binds to a specific receptor and triggers a response in the cell.
Blockage of SNS • Drugs that inhibit sympathetic nervous system are classified as • Antiadrenergic • Sympatholytic anticholinergic
Stimulation of PNS • Parasympathetic nervous system stimulation drug classifications • Cholinergic • Parasympathomimenic • Cholinomimetic
Blocking of PNS • Drugs that inhibit parasympathetic stimulation are classified as: • Anticholinergic • Parasympatholytic • Cholenergic blocking drugs
Classifications: SNS • Sympathetic nervous system drug classifications • Adrenergic - stimulating • Antiadrenergic - blocking
Classifications: PNS • Parasympathetic nervous system drugs • Cholinergic • Anticholinergic
Adrenergic Drugs Chapter 17
Adrenergic Drugs • What do they do? • Stimulation of the sympathetic nervous system.
Mechanism of Action • Three mechanisms: • Directly with alpha 1 or beta-adrenergic receptors on surface membrane. • Indirect effects of postsynaptic adrenergic receptors. • Mixed action – combination of action on direct and indirect receptor.
Heart • Direct stimulation of receptors • Alpha 1 - Vasoconstriction of blood vessels which increases blood pressure – pressor or vasopressor effect. • Beta 2 - increased force of myocardial contraction - Increased speed of electrical conduction in the heart.
Lungs Asthma and COPD (Chronic Obstructive Pulmonary Disease): Beta 2 drugs or bronchodilators are used to relieve broncho-constriction and broncho-spasm.
Pregnancy • Adrenergic drugs used to relax uterine muscles in preterm labor.
OTC Adrenergic Drugs • Common cold: anti-histamines • Allergy: nasal or oral to relieve nasal congestion
Adrenergic Drugs • Epinephrine • Pseudoephedrine – Sudafed • Isoproterenol (Isuprel) • Phenylephrine (Neo-Synephrine) • Clonidine (antihypertensive)
How does one choose a drug? • How emergent is the situation • PO or IM or IV
Allergic Response • Runny nose, itchy eyes, cough • Asthma: Cough with bronchospasms, difficulty breathing or SOB (shortness of breath) • Anaphylactic shock – edema of airway
Allergy Response • Nasal congestion, itchy eyes, non-productive cough • Seasonal response to environmental causes • Commonly mixed with other drugs in cold medications
Pseudoephedrine • Therapeutic classification: allergy, cold, and cough remedies, nasal drying, and decongestants. • Indications: symptomatic management of nasal congestion associated with acute viral upper respiratory tract infection. Most often used in combination with other drugs. • Action: stimulates Alpha and beta-adrenergic receptors – vasoconstriction in respiratory tract mucosa – possible bronchodilation • Therapeutic effects: reduction of nasal congestion, and swelling of nasal passages.