Autonomic & Somatic Nervous Systems Flashcards
What does sympathetic stimulation produces?
Increase in heart rate
Increase in blood pressure
RBCs pour into circulation from spleen
Blood flow shifts from skin & splanchnic region to skeletal muscle (causes pallor)
Blood glucose increases (glycogen in the liver is broken down into glucose, but insulin is also released)
Bronchiolar smooth muscle relax and pupils dilate
Intestinal smooth muscle relaxes but sphincters contract.
Activation of the renin-angiotensin-aldosterone system
What does cholinergic stimulation produce?
Salivation: stimulation of salivary glands
Lacrimation: stimulation of lacrimal glands
Urination: relaxation of internal sphincter muscle of urethra and contraction of the detrusor muscles
Gastrointestinal: upset. Smooth muscle tone causes GI problems (inc. diarrhea)
Emesis: vomiting
-Miosis: stimulation of papillary constrictor muscles.
What is Acetylcholine (ACh)?
Acetylcholine (ACh) is the neurotransmitter at the ganglia (both sympathetic and parasympathetic), at the postganglionic parasympathetic ending, and in the somatic nervous system.
What does acetylcholinesterase do?
breakdown Acetylcholine
What is Norepinephrine?
Norepinephrine is the neurotransmitter at the synapse between the postganglionic sympathetic neuron and the effector tissue. (Exception is the sweat glands where Ach is released).
What metabolizes NE?
metabolized by catechol O-methyltransferase (COMT) and monoamine oxidase (MAO) in the liver.
What is the difference between MAO-A and MAO-B?
MAO-A appears to be the important enzyme in depression and also the one responsible for adverse effects of MAO inhibitors
MAO-B is important in the metabolism of catecholamines in the brain. Selective inhibitors of MAO-B have been tried in Parkinson’s disease
What are the names of NE receptor sites?
alpha and beta
What are the effects of Alpha-1 stimulation?
Alpha-1 (postsynaptic) (causes contraction, e.g., blood vessels, sphincters, radial muscle of eye) (There are at least 3 receptor subtypes. α1A is found in the prostate gland; α1B is found in the wall of blood vessels.) Vasoconstriction Mydriasis Contraction of GI sphincters Contraction of bladder sphincter
What are the effects of Alpha-2 stimulation?
Alpha-2 (presynaptic) [negative feedback loop inhibiting subsequent release of neurotransmitter]
inhibits insulin release.
What are the effects of Beta-1 stimulation?
Beta-1 (predominately cardiac) Stimulation produces increase in heart rate and strength of contraction.
What are the effects of Beta-2 stimulation?
Beta-2 (predominately non-cardiac) receptors are found on smooth muscle [e.g., bronchi; large blood vessels] causing relaxation. Beta-2 receptors also promote insulin release and, in liver & muscle, gluconeogenesis & glycogenolysis as well as lipolysis in fat cells.
What are the effects of Dopamine-1 receptor stimulation?
Dopamine-1 (postsynaptic) receptor activation is responsible for vasodilation in splanchnic & renal circulations. Stimulation of dopamine receptors in chemoreceptor trigger zone causes nausea and vomiting.
What are the effects of Dopamine-2 receptor stimulation?
Dopamine-2 (presynaptic) receptors initiate a negative feedback loop. {At least five varieties of dopamine receptors are found in brain}
What are Acetylcholine (ACh) receptors?
Muscarinic and Nicotinic
How are Muscarinic receptors located?
Muscarinic - found at postganglionic parasympathetic endings (heart; smooth muscle; glands).
Where are Nicotinic receptors located?
Nicotinic receptors are found in ganglia and at neuromuscular junction. These are not identical, but are identified as
NM, receptors found at the neuromuscular junction in skeletal muscle.
NG or NN receptors found in autonomic ganglia, adrenal medulla, and CNS
What is Bethanechol (Urecholine)?
is a cholinomimetic that is somewhat selective to smooth muscle of the GI tract and the detrusor muscle of the urinary bladder, (It may have a relative affinity for specific muscarinic receptors in the gut). It also increases the tone of the lower esophageal sphincter in patients with reflux esophagitis.
What is Bethanechol (Urecholine) Side effects and contraindications?
Toxicity & side effects:
Initially: Abdominal discomfort, salivation, flushed skin, sweating, nausea, vomiting, and miosis are common.
Toxic reactions: include intense cramping, diarrhea, urination, bradycardia, and bronchoconstriction.
Contraindicated: COPD, asthma, hyperthyroidism, peptic ulcer.
What is Neostigmine and pyridostigmine?
produce reversible inhibition of AChE by formation
are used in the treatment of myasthenia gravis
What are the side effects of Neostigmine and pyridostigmine?
Side effects include nausea, diarrhea, and excessive salivation. Caution in patients with asthma. If muscarinic effects of such therapy are prominent, they can be controlled by the administration of atropine.
Differences between Neostigmine and pyridostigmine?
Pyridostigmine is generally preferred in myasthenia because of its longer duration of action (6 hr vs. 2 hr for neostigmine).
What is Donepezil HCl [Aricept]?
is a centrally acting reversible cholinesterase inhibitor leading to increased levels of acetylcholine in the brain. treatment of mild to moderate dementia of the Alzheimer’s type. Among those who benefit, improvements are seen in quality of life and cognitive functions (eg, memory, thought, reasoning)
What are Donepezil HCl [Aricept] side effects?
Side effects: Most side effects are related to increased cholinergic (muscarinic) effects including sialorrhea, nausea, vomiting, diarrhea, dyspepsia, urinary urgency myalgia, anorexia, ataxia, bradycardia, and bronchoconstriction.
atropine
Anticholinergic (antimuscarinic) drugs competitively antagonize the effects of ACh and other muscarinic agonists at cholinergic postganglionic (muscarinic) sites found in the heart, salivary glands & smooth muscle of the GI and GU tract (simply by binding to and blocking the receptor site)
is used to reverse severe sinus bradycardia
Scopolamine
Anticholinergic (antimuscarinic) drugs competitively antagonize the effects of ACh and other muscarinic agonists at cholinergic postganglionic (muscarinic) sites
has marked CNS depressant effects
What are side effects of Atropinic drugs?
Cardiovascular: The atria of the heart are richly innervated by parasympathetic nerve fibers, and the SA node is very sensitive to muscarinic receptor blockade. Large doses cause progressively increasing tachycardia by blocking vagal effect at the SA node pacemaker (average increase in heart rate: 35-40 beats/minute).
Gastrointestinal: Salivary secretion is particularly sensitive to inhibition by antimuscarinic agents.
Sweat glands: Small doses of atropine inhibit the activity of sweat glands.
Respiratory tract. Atropine decreases secretions in the nose, mouth, pharynx and bronchi. It also blocks vagal-induced bronchoconstriction.
Urinary tract: Muscarinic antagonists decrease normal tone and amplitude of contraction of the ureter and bladder.