when an excitatory synapse brings the membrane potential of the post synaptic neuron closer to the threshold for generating an action potential. Excitatory synapses depolarize the post synaptic neuron.
this depolarization is called an epsp excitatory postsynaptic potential.
describe a fast EPSP
channel linked receptor
caused by the binding of neurotransmitter molecules to their channel linked receptors. ion moves through rapidlly
sodium ions enter, potassuim ions leave
sodium movement is greater
net effect is depolarization
describe slow EPSP
Slow response is mediated through G protien-linked receptors.
direct coupling opens or closes channels, or secondary messenger system (g protien) opens or closes ion channels
uses phosphorylation of a potassium channel
decrease leakage of potassium out of cell
net effect same as fast, that is depolarition
define inhibitory postsynaptic potential IPSP
Hyperpolarize the post synaptic membrane
take membrane potential farther away from threshold for an action potential
can occur by:
closing sodium channels
opening potassium channels
opening chloride channels
define frequency coding
the degree of depolarization does not affect the size of action potentials but rather their frequency
increases in strength of suprathreshold stimuli cause the frequency of action pot. to increase=
when action pot. occur at higher frequency more neurotransmitter is released from neuron
describe the neurotransmitter Acetylcholine, where is located and types of receptors it binds to
acetylcholine is released from neurons both in the central and preriferal nervous systems
binds to multiple cholinergic receptors
Nicotinic cholinergic receptors
Muscarinic cholinergic receptors
Describe Nicotinic Cholinergic Receptors
Direct fast acting
cause excitiory postsynaptic potentials EPSP
Located on skeletal muscle cells
both sympathetic and parasymnpathic
describe muscarinic cholinergic receptors
need G protien ie. Slow response
can open/close ion channels OR activate enzymes
located on effector organs innervated by parasympathetic Nervous system
-Heart slows heart rate
-smooth muschle of digestive tract
-smooth muscles controling the constriction of the pupil of the eye
what is the role of epinephrine/norepinephrine?
binds to adrenergic receptors.
Alpha -a1, a2,
receptors found in CNS and effector organs of sympathetic nervous system
true or false:
epinephrine and norepinephrine are not g protien second messenger receptors (slow response)
they are g protien receptors, and slow
alpha 1 and alpha 2 are located where?
alpha 1 is in smooth muscle of blood vessels of skin, kidney, gi tract and sphincters
decreases blood flow during sympathetic stimulation
alpha 2 decrease activity of gi tract
where are beta 1,2,3 receptors found?
B1- found in cardiac muscle, CNS, and kidneys increased force of contraction in cardiac muscle
B2- respiratory tract, uterus and some blood vessels, inhibitory response, relaxation of smooth muscle of vessels that supply heart and skeletal muscle. dilation of broncholes in lungs
B3-in lipolysis of adipose tissue, excitatory response mobilization of fats