synapses
DESCRIPTION
SYNAPSES. D. C. Mikulecky Professor of Physiology http://views.vcu.edu/~mikuleck/. TWO TYPES OF SYNAPSE. ELECTRICAL CHEMICAL. ELECTRICAL. GAP JUNCTION: PROVIDES PATH FOR IONS TO FLOW FROM ONE CELL TO ANOTHER. CELL 1. CELL 2. CHEMICAL: THE SYNAPSE. INCOMING NERVE. POST SYNAPTIC - PowerPoint PPT PresentationTRANSCRIPT
SYNAPSES
D. C. Mikulecky
Professor of Physiology
http://views.vcu.edu/~mikuleck/
TWO TYPES OF SYNAPSE
• ELECTRICAL
• CHEMICAL
ELECTRICAL
GAP JUNCTION: PROVIDES PATH FOR IONS TO FLOW FROM ONE CELL TO ANOTHER
CELL 1 CELL 2
CHEMICAL: THE SYNAPSE
INCOMING NERVE
POST SYNAPTIC NERVE
SPACE
EVENTS IN CELLULAR COMMUNICATION INPUT SIGNAL (CHEMICAL,MECHANICAL, PHOTO,
ELECTRICAL)
RESPONSE (OUTPUT)
SECRETION CONTRACTION/RELAXATION DIVISIONPHAGOCYTOSIS
RECEPTOR
TRANSDUCER
EFFECTORENZYMES,GENOME,CONTRACTILE FILAMENTS,
SECRETORY GRANULES
HOW ARE WE WIRED?CONNECTIONS BETWEEN NERVE CELLS
CELLBODY
DENDRITES
AXON
AXONHILLOCK
AXONTERMINALS
THE NATURE OF CHEMICAL TRANSMISSION BETWEEN NERVES
• PRESYNAPTIC EVENTS
• POSTSYNAPTIC EVENTS
• IN THE SPACE
PRESYNAPTIC EVENTS
• THE ALL OR NONE ACTION POTENTIAL TRIGGERS THE RELEASE OF CHEMICAL TRANSMITTER
INCOMING ACTION POTENTIAL
• DEPOLARIZES
• TRIGGERS CALCIUM CHANNELS
• CALCIUM ENTERS THE CELL
THE SYNAPSE
SYNAPTICVESSICLES
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INCOMINGACTION POTENTIAL
CALCIUM CHANNEL
IONCHANNEL
RECEPTOR
ENZYME
THE SYNAPSE: INCOMING ACTION POTENTAL
SYNAPTICVESSICLES
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INCOMINGACTION POTENTIAL
CALCIUM CHANNEL
IONCHANNEL
RECEPTOR
ENZYME
CALCIUM INFLUX
• CAUSES VESSICLES TO BE RELEASED
• VESSICLES MIGRATE TO MEMBRANE
• EXOCYTOSIS
• NEUROTRANSMITTER ENTERS SPACE
THE SYNAPSE: CALCIUM CHANNELS OPEN
SYNAPTICVESSICLES
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INCOMINGACTION POTENTIAL
CALCIUM CHANNEL
IONCHANNEL
RECEPTOR
ENZYME
THE SYNAPSE: NEUROTRANSMITTER ENTERS SPACE
SYNAPTICVESSICLES
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CALCIUM CHANNEL
IONCHANNEL
RECEPTOR
ENZYME
POST SYNAPTIC EVENTS
• IONOTROPIC (LIGAND GATED) CHANNELS
• VOLTAGE GATED CHANNELS
• ELECTROPHYSIOLOGICAL PRINCIPLES
IONOTROPIC CHANNELS
• BIND NEUROTRANSMITTER
• OPEN CHANNEL
• HYPER OR DE-POLARIZATION
THE SYNAPSE:NEUROTRANSMITTER BINDS TO POSTSYNAPTIC
RECEPTOR
SYNAPTICVESSICLES
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CALCIUM CHANNEL
IONCHANNEL
RECEPTOR
ENZYME
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HOW ARE WE WIRED?CONNECTIONS BETWEEN NERVE CELLS
CELLBODY
DENDRITES
AXON
AXONHILLOCK
AXONTERMINALS
POSTSYNAPTIC POTENTIALS
RESTINGPOTENTIAL
IPSP EPSP
TIME
SPATIAL SUMMATION
TIME
SIMULTANEOUSINPUT FROM TWOSYNAPSES: ABOVETHRESHOLD
THRESHOLD
SPATIAL SUMMATION
TIME
SIMULTANEOUSINPUT FROM TWOSYNAPSES: ABOVETHRESHOLD
THRESHOLD
TEMPORAL SUMMATION
TIME
TOO FAR APART IN TIME:NO SUMMATION
TEMPORAL SUMMATION
TIME
CLOSER IN TIME: SUMMATION BUT BELOW THRESHOLD
THRESHOLD
THE GOLDMAN-HODGKIN-KATZ (GHK) EQUATION
[Ko] + [Nao]Vm = 60 LOG --------------------------
[Ki] + [Nai]
IS THE RATIO OF SODIUM TO POTASSIUM PERMEABILITY
TEMPORAL SUMMATION
TIME
STILL CLOSER IN TIME: ABOVETHRESHOLD
THRESHOLD
EPSP-IPSP CANCELLATION
HOW EXCITATION OCCURS-THE ROLE OF DEPOLARIZATION AND HYPERPOLARIZATION
• SUMMATION CAN DEPOLARIZE THE CELL BEYOND THRESHOLD
• HYPERPOLARIZATION BLOCKS
NEURO TRANSMITTERS
• ACETYL CHOLINE• DOPAMINE• NOREPINEPHRINE• EPINEPHRINE• SEROTONIN
• HISTAMINE• GLYCINE• GLUTAMINE• GAMMA-
AMINOBUTYRIC ACID (GABA)
IN THE SPACE
• ENZYME “CHEWS UP” LIGAND
• MASS ACTION CAUSES LIGAND TO DISSOCIATE FROM RECEPTOR
THE SYNAPSE
SYNAPTICVESSICLES
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CALCIUM CHANNEL
IONCHANNEL
RECEPTOR
ENZYME
THE SYNAPSE
SYNAPTICVESSICLES
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CALCIUM CHANNEL
IONCHANNEL
RECEPTOR
ENZYME