lecture 3 LOs Flashcards
what do competitve antagonsits do to the potency, and how does the dose/response curve chage
reduces potency, shifts the curve
what do non competitve antagonists do to the dose/response curve
change the shape of the curve
often prevent agonist from acieing maximal effect, irrespective of how much agonsit is available
physiological antagonism def
two drugs interact to reduce the effectiveness of both
additive effects def
both drugs work together to create an effect which is equal to the sum of the two drugs
potentiation def
combination of two drugs produces effects greater than the sum of the individual effects
drug tolerance def
diminished response to a drug after repeated exposure
cross tolerance def
tolerance to one drug can diminish effectiveness of another drug (usually one that works on a similar mechanism)
characteristics of drug tolerance
revisable when drug use stops
dependent on dose/frequency of drug use and drug taking environment
may occur rapidly (acute tolerance), after long periods of chronic use, or never
several different mechanisms explain multiple forms of tolerance
metabolic (drug-dispositional) tolerance def
repeated drug use reduces the amount of drug available at the target tissue (body/liver becomes more efficient at metabolizing drug, less drug gets to sites of action)
functional (pharmacodynamic) tolerance def
changes in cell function compensates for repeated drug exposure. typically occurs at site in brain/body where drug exerts its effects (like receptor sensitivity to the ligand decreases)
behavioural tolerance def
pavlovian conditioning can impact tolerance
brain makes associations between the drug effects and the context where they occurred
conditioned tolerance def
tolerance is maximal when drug is given in environments similar to those where drug effects previously experienced
conditioned tolerance study (rats)
give rats 20 shots of alcohol in one environment (over 20 days). on test day one group gets alc in same context and other gets alc in different context. rats who received in same context displayed tolerance and in different context there was no tolerance
three main parts of neuron
soma (cell body): nucleus and all other organelles. all proteins are made here and transported to more distant targets
dendrites: extensions that receive info (inputs). composed of shafts (main branches) and spines (smaller bumps where most synaptic connections reside)
axon: extension that conducts electrical signals from the cell body to the terminal boutons (outputs). one neuron may have multiple projection sites via axon collaterals
glial cell def
not exitable cell, but play key role that influences neural activity and transmissions (structural support, ion concentration around cells, reuptake of certain NTs)
projection (principle) neuron def
main integrating/processing neurons of a brain region. axons project out of region in which its soma resides and/or to local neurons within the same region
interneurons def
cell whose axon remain within a particular brain region that can connect to projection neurons and other interneurons
smaller than projection neurons
usually inhibitory, often use GABA or ACh as transmitter
excitatory neurons often can connect to both inhibitory interneurons and other excitatory cells via collaterals
receptor def
initial site of action of neurotransmitters (or drugs)
enzymes def
metabolize NTs and other functions
ion channels allow
charged molecules and amino acids, glucose, etc
which can only move through ion channels
Na+, K+, Cl-, Ca2+
gated channels:
normally closed, open in response to specific stimuli. tend to stay open for a brief period before closing
what does opening a channel excite or inhibit
excite: Na+, Ca2+
inhibit: K+, Cl-
when does voltage gated open
when electrical potential across membrane is altered
may open when cell depolarizes, some open when cell is hyperpolarized
when does ligand gated open
when ligand binds to receptor
2nd messenger is special case of ligand gated channel. activated by attachment of phosphate group on intracellular side of receptor
resting membrane potential
is negative, driven primarily by high conc of positive ions (Na+, Ca2+, K+) outside the cell, and higher conc of negative ions inside the cell
Action potential def and steps
occurs when neurons depolarize to a threshold
depolarization causes voltage gated Na+ channels to open, causes Na+ to enter cell
AP causes voltage gated K+ channels to open, K+ exits cell and hyperpolarizes it causing Na+ and K+ channels to close
local potentials
often induced via depolarization or hyperpolarization
excitatory or ihibitory post synaptic potentials
caused by local potentials
local potentials grading
larger stimulus = greater magnitude of hyperpolarization or depolarization
action potential grading
all or nothing
peripheral nervous system components
somatic: controls voluntary muscles, delivers sensory input to the brain
autonomic system (ANS): regulates internal environment by innervating smooth muscles (intestines and bladder), cardiac muscles and glands (adrenal, salivary). also controls digestion, BP, body temp, and other functions
autonomic nervous system divisions
sympathetic: fight or flight. dominates in times of stress, excitement, exertion. increases heart rate, BP, blood flow to skeletal muscles, adrenal secretion
parasympathetic: dominates when energy reserves can be conserved. increases digestion, storage of glucose and other nutrients, slows heart rate and decreases respiration.
what do ANS neurons use as transmitters
norepinephrine and acetylcholine
spinal cord sends which transmitter to where
Ach to sympathetic ganglia and adrenal glands
typically excitatory, acts on nicotinic receptors
sympathetic ganglia send what transmitter where
norepinephrine to organs
where else is NE secreted
blood stream. can be excitatory or inhibitory depending on the receptor subtype
when drugs increase/decrease NE activity what do they tend to cause
increase or decrease in sympathetic activation
when drugs increase Ach or stimulate nicotonic receptors, what do they cause
sympathetic functioning
parasympathetic uses which transmitter exclusively
ACh
spinal cord projects to where
para-sympathetic ganglia
muscarinic antagonists do what
reduce parasympathetic function
muscarinic agonists do what
increase the parasympathetic function
