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PERCEPTION & COORDINATION
The Anatomy & Physiology of the nervous system
Sympathomimetics
• Drugs that stimulate the sympathetic nervous system and mimic the sympathetic neurotransmitters (norepinephrine, epinephrine).
• They act on one or more adrenergic receptors sites located on the cells of smooth muscles such as the heart, bronchiole walls, gastrointestinal tract, urinary bladder, and ciliary, muscle of the eye.
The Anatomy & Physiology of the nervous system
SympathomimeticsClassification
The Anatomy & Physiology of the nervous system
Sympathomimetics
Epinephrine• Administered SC, IV, topically, or by
inhalation. It is not to be given orally as it is metabolized quickly in the GI tract resulting to inadequate serum levels.
• It is frequently used in emergencies to combat anaphylaxis.
• It is a potent inotropic drug that causes the blood vessels to constrict; thus blood pressure increases, the heart rate increases, and the bronchial tubules dilate.
The Anatomy & Physiology of the nervous system
Sympathomimetics
Albuterol Sulfate (Proventil, Ventolin)
• Selective beta2 adrenergic receptor agonist which response is bronchodilation.
• Used primarily in asthmatic patients
The Anatomy & Physiology of the nervous system
Sympathomimetics
Isoproterenol HCl • Activates both beta1 and beta2
receptors. It is more specific than epinephrine becauseit acts on two different adrenergic receptors but is not completely selective.
• Used to control asthma
The Anatomy & Physiology of the nervous system
Sympathomimetics
Clonidine (Catapres) and Methyldopa (Aldomet)
• They are selective alpha2 adrenergic drugs that are used primarily to treat hypertension.
• They regulate the release of norepinephrine by inhibiting its release.
• They cause cardiovascular depression by stimulating alpha2 receptors in the CNS leading to a decrease in blood pressure.
The Anatomy & Physiology of the nervous system
Sympatholytics
• Drugs that block the effects of the adrenergic neurotransmitters. They act as antagonists to the adrenergic agonists.
• Inhibits the release of the neurotransmitters norepinephrine and epinephrine.
The Anatomy & Physiology of the nervous system
Sympatholytics
Alpha-Adrenergic Blockers• Drugs that block or inhibit a
response at the alpha-adrenergic receptor site.
• They are divided into 2 groups: selective alpha-blockers (those that block alpha1) and nonselective alpha-blockers (those that block alpha1 and alpha2).
The Anatomy & Physiology of the nervous system
Sympatholytics
Beta-adrenergic Blockers• These drugs cause a decrease in
heart rate and a decrease in blood pressure.
• They are divided into 2 groups: selective beta-blockers (those that block beta1) and nonselective beta-blockers (those that block beta1 and beta2).
The Anatomy & Physiology of the nervous system
Sympatholytics
Adrenergic Neuron Blockers• Drugs that block the release of
norepinephrine from the sympathetic terminal neurons.
• Its clinical use is to decrease blood pressure. They are potent antihypertensive agents.
• Examples of this drugs are guanethidine monosulfate (Ismelin) and guanadrel sulfate (Hylorel).
The Anatomy & Physiology of the nervous system
Parasympathetic Nervous System
• The parasympathetic system dominates control of many visceral effectors under normal, everyday conditions.
• The ANS is responsible for regulation of internal organs and glands, which occurs unconsciously.
The Anatomy & Physiology of the nervous system
Parasympathetic Nervous System
• The two types of receptors are1. muscarinic receptors - stimulates
the smooth muscles and slow heart rate
2. nicotinic receptors - stimulates skeletal muscles for contraction
The Anatomy & Physiology of the nervous system
Parasympathetic Nervous System
STRUCTURE• Parasympathetic
preganglionic neurons – dendrites and cell bodies are located in the gray matter of the brainstem and the sacral segments of the spinal cord.
The Anatomy & Physiology of the nervous system
Parasympathetic Nervous System
STRUCTURE• Parasympathetic
preganglionic neurons – axons extend some distance before terminating in the parasympathetic ganglia located in the head and in the thoracic and abdominal cavities close to the visceral effectors that they control
The Anatomy & Physiology of the nervous system
Parasympathetic Nervous System
STRUCTURE• Parasympathetic
postganglionic neurons – dendrites and cell bodies lie in the outlying parasympathetic ganglia, and their short axons extend into the nearby structures.
The Anatomy & Physiology of the nervous system
Autonomic Neurotransmitters
The Anatomy & Physiology of the nervous system
PNS Neurotransmitters(Postganglionic Neurons-Effectors}
• Acetylcholine • 2 Types of Receptors
a) Muscarinic – stimulates smooth muscles (Cardiac Muscle)
b) Nicotinic – stimulates skeletal muscles (neuromuscular)
The Anatomy & Physiology of the nervous system
Parasympathetic Responses
The Anatomy & Physiology of the nervous system
Parasympathomimetics(Cholinergics)
• These are drugs that stimulate the parasympathetic nervous system.
• They mimic the parasympathetic neurotransmitter acetylcholine.
The Anatomy & Physiology of the nervous system
ParasympathomimeticsClassification
The Anatomy & Physiology of the nervous system
Parasympathomimetics
Direct-Acting CholinergicsBethanicol Chloride,
Metoclopramide HCl, Carbachol• They are primarily selective to the
muscarinic receptors and are nonspecific because the muscarinic receptors are located in the smooth muscles of the GI and genitourinary tracts, glands, and the heart.
The Anatomy & Physiology of the nervous system
Parasympathomimetics
Direct-Acting Cholinergics• Eye: pilocarpine• These drugs constricts the pupils
of the eyes thus opening the canal of Schlemm to promote drainage of aqeous humor. This is used to treat glaucoma by relieving fluid (intraocular) pressure in the eye.
The Anatomy & Physiology of the nervous system
ParasympathomimeticsClassification
The Anatomy & Physiology of the nervous system
Parasympathomimetics
Indirect-Acting Cholinergics• demecarium bromide, echothiophate
iodide, isoflurophate• These group of drugs do not act on
receptors, instead they inhibit or inactivate the enzyme cholinesterase, thus permitting acetylcholine to accumulate at the receptor sites. Thus they are called cholinesterase inhibitors or anticholinesterases.
The Anatomy & Physiology of the nervous system
2 Types of Indirect-Acting Cholinergics
Reversible Cholinesterase Inhibitors
• Ex. ambenonium chloride, edrophonium chloride
• These drugs are used 1. to produce papillary constriction in the
treatment of glaucoma2. to increase muscle strength in clients
with myasthenia gravis.
The Anatomy & Physiology of the nervous system
2 Types of Indirect-Acting Cholinergics
Irreversible Cholinesterase Inhibitors
• Ex. neostigmine, neostigmine methylsulfate, pyridostigmine bromide
• These are potent agents because their effect are long lasting. With irreversible inhibitors the bond between the irreversible cholinesterase inhibitor and cholinesterase are permanent.
The Anatomy & Physiology of the nervous system
Parasympatholytics(Anticholinergics)
• Drugs that inhibit the actions of acetylcholine by occupying the acetylcholine receptors.
• The major responses to anticholinergics are a decrease in GI motility, a decrease salivation, dilation of pupils (mydriasis), and an increase in pulse rate.
The Anatomy & Physiology of the nervous system
Parasympatholytics(Anticholinergics)
The Anatomy & Physiology of the nervous system
Parasympatholytics(Anticholinergics)
Atropine• Atropine acts on the muscarinic
receptor, but they have little effect on the nicotinic receptor.
The Anatomy & Physiology of the nervous system
Parasympatholytics(Anticholinergics)AtropineUses of Atropine1. Pre-operative medication to decrease
salivary secretions2. Antispasmodic drug to treat peptic
ulcers because it relaxes the smooth muscles of the GI tract and decreases peristalsis
3. Agent to increase the heart rate when bradycardia is present.
4. This can also be given as an antidote for muscarinic agonist poisoning.
The Anatomy & Physiology of the nervous system
Disorders of the Autonomic Nervous System
1. Stress-Induced Disease– Heart Disease – Digestive Problems– Reduced resistance to disease
2. Neuroblastoma – is a malignant tumor of the sympathetic nervous system. –Occurs in the developing nervous systems of young children and metastasizes rapidly to other parts f the body.
