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Neuropharmacology:
Definition, 2 Categories
- study of drugs that alter processes controlled by the nervous system
- 1. peripheral NS drugs
- 2. central NS durgs
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Axonal Conduction
- conducts an action potential down axon of a neuron
- from neuron, down axon, to axon terminal
- rare method of drugs, nonselective, only local anesthesia is effective
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Synaptic Transmission
- sythesis, storage, release, binding, termination
- process by which info is carried accross the synaptic gap
- most common, allows for selectivity
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5 Steps in Synaptic Transmission
- Transmitter Synthesis: from precursor molecules
- Transmitter Storage: vesicles w/in terminal
- Transmitter Release: vesicles fuse w/terminal membrane
- Receptor Binding: reversible bind to postsynaptic cell receptor
- Termination of Transmission: removed from gap
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3 Methods of Termination of Synaptic Transmission
- Reuptake (axon terminal "pumps" transmitters in)
- Enzymatic Degradation
- Diffusion away from synaptic gap
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Agonist vs. Antagonist
- Agonist: drugs that directly activate receptors (increase response)
- Angtagonist: prevents receptor activation (decrease response)
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Primary Response to Activation:
Beta 1 and Beta 2
- Beta 1
- --increased heart rate
- --increased force of cardiac contraction
- Beta 2--increased cardiac output
- --bronchodilation
- --elevation of blood glucose
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3 Main Elements of a Feedback Loop, Process
- 1. a sensor
- 2. an effector
- 3. neurons connecting the sensor to the effector
- sensor monitors status of physiologic process
- info sent to CNS
- info integrated w/other relevant info
- signals/instructions sent from CNS along nerves of ANS to effector
- effector makes appopriate adjustments
- whole process is called a "REFLEX"
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3 Types of Info Needed for PNS Drugs
- 1. Identify type(s) of receptors through which the drug acts
- 2. the normal response to activation of those receptors
- 3. whether the drug increases or decreases receptor activation
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Divisions of the Nervous System
- 1. Central NS
- 2. Peripheral NS
- --A. Somatic Motor System
- --B. Autonomic Nervous System
- ------I. Sympathetic Nervous System
- ------II. Parasympathetic Nervous System
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3 Principle Fxns of Autonomic NS
- 1. regulation of the heart2. regulation of secretory glands (salivary, gastric, sweat, broncial)
- 3. regulatoin of smooth muscles (of bronchi, blood vessels, urogenital system, GI)
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7 Functions of PNS:
"housekeeping" (conserve energy, digest food, excrete waste, control vision)
- 1. slow HR
- 2. incr. Gastric Secretion
- 3. empty Bladder
- 4. empty Bowels
- 5. focus Eye for Near Vision
- 6. constrict Pupil
- 7. contract Bronchial Smooth Muscle
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3 Main Fxns of SNS
- regulate Cardiovascular System
- regulate Body Temperature
- implement Fight or Flight
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3 Homeostatis Objectives Achieved by SNS
- maintain bloodflow to brain
- redistribute bloodflow during exercise
- compensate for loss of blood, primarily by cause vasoconstriction
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SNS regulation of Body Temperature (3)
- 1. regulates bloodflow to the skin
- ---dilates surface vessels (heat loss)
- ---constricts cutaneou vessels (conserve heat)
- 2. promotes secretion of sweat
- 3. induces piloerection (conserve heat)
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SNS Fight or Flight Response (5)
- 1. Incr. HR and Incr. BP
- 2. Shunting blood away from skin and viscera and into skeletal muscles
- 3. Bronchodilation to improve oxygenation
- 4. Dilation of Pupils
- 5. Mobilizing stored energy, thereby providing glucose for the brain and fatty acids for muscles
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SNS vs. PNS:
eye, tears, saliva, lungs, heart, gut, liver, bladder
- SNS:
- Eye:dilates pupil
- Tear Glands: no effect
- Salivary Glands: inhibits salivary production
- Lungs: dilates bronchi
- Heart: speeds up rate
- Gut: inhibits peristalsis
- Liver: stimulates glucose production
- Bladder: inhibits urination
- PNS:
- Eye: contricts pupils
- Tear Glands: stimulates tear production
- Salivary Glands: stimulates saliva production
- Lungs: constricts bronchi
- Heart: slows down rate
- Gut: stimulates peristalsis
- Liver: stimulates bile production
- Bladder: stimulates urination
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Baroreceptor Reflex
- Most important in ANS
- Regulates Blood Pressure
- 1. Baroreceptors in Carotid Sinus + Aortic Arch monitor changes in BP and send info to brain
- 2. in response, brain send impulse along nerves in ANS, instructing heart &blood vessels how to behave in response to change in BP
- Decreased BP: reflex vasoconstriction to incr. BP
- Increased BP: reflex vasodilation to decr. BP
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3 Neurotransmitters of Peripheral NS
(plus possible 4th)
- 1. Acetylcholine: employed at most junctions of PNS
- 2. Norepinephrine: released by practically all postgang. neurons of SNS (only exception is sweat gland[ACh])
- 3. Epinephrine: major transmitter released by adrenal medulla
- 4. Dopamine
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Cholinergic Receptors
- mediate responses to ACh (at all jxns where ACh is the transmitter)
- --ganglia of ANS
- --neuromuscular jxn
- --organs regulated by PNS
- Subtypes:
- Nicotinic N
- Nicotinic M
- Muscarinic
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Adrenergic Receptors
- mediate responses to Epi and NE (at all jxns where they are the transmitters)
- Subtypes:
- Alpha 1
- Alpha 2
- Beta 1
- Beta 2
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