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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

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synapses
SYNAPSES

D. C. Mikulecky

Professor of Physiology

http://views.vcu.edu/~mikuleck/

two types of synapse
TWO TYPES OF SYNAPSE
  • ELECTRICAL
  • CHEMICAL
electrical
ELECTRICAL

GAP JUNCTION: PROVIDES PATH FOR IONS TO

FLOW FROM ONE CELL TO ANOTHER

CELL 1

CELL 2

chemical the synapse
CHEMICAL: THE SYNAPSE

INCOMING NERVE

POST SYNAPTIC

NERVE

SPACE

events in cellular communication
EVENTS IN CELLULAR COMMUNICATION

INPUT SIGNAL (CHEMICAL,MECHANICAL, PHOTO,

ELECTRICAL)

RECEPTOR

TRANSDUCER

EFFECTOR

ENZYMES,GENOME,CONTRACTILE FILAMENTS,

SECRETORY GRANULES

RESPONSE (OUTPUT)

SECRETION CONTRACTION/RELAXATION DIVISION

PHAGOCYTOSIS

how are we wired connections between nerve cells
HOW ARE WE WIRED?CONNECTIONS BETWEEN NERVE CELLS

AXON

CELL

BODY

AXON

TERMINALS

AXON

HILLOCK

DENDRITES

the nature of chemical transmission between nerves
THE NATURE OF CHEMICAL TRANSMISSION BETWEEN NERVES
  • PRESYNAPTIC EVENTS
  • POSTSYNAPTIC EVENTS
  • IN THE SPACE
presynaptic events
PRESYNAPTIC EVENTS
  • THE ALL OR NONE ACTION POTENTIAL TRIGGERS THE RELEASE OF CHEMICAL TRANSMITTER
incoming action potential
INCOMING ACTION POTENTIAL
  • DEPOLARIZES
  • TRIGGERS CALCIUM CHANNELS
  • CALCIUM ENTERS THE CELL
the synapse
THE SYNAPSE

INCOMING

ACTION

POTENTIAL

CALCIUM

CHANNEL

•••

RECEPTOR

SYNAPTIC

VESSICLES

•••

•••

•••

•••

•••

ION

CHANNEL

•••

•••

•••

ENZYME

the synapse incoming action potental
THE SYNAPSE: INCOMING ACTION POTENTAL

INCOMING

ACTION

POTENTIAL

CALCIUM

CHANNEL

•••

RECEPTOR

SYNAPTIC

VESSICLES

•••

•••

•••

•••

•••

ION

CHANNEL

•••

•••

•••

ENZYME

calcium influx
CALCIUM INFLUX
  • CAUSES VESSICLES TO BE RELEASED
  • VESSICLES MIGRATE TO MEMBRANE
  • EXOCYTOSIS
  • NEUROTRANSMITTER ENTERS SPACE
the synapse calcium channels open
THE SYNAPSE: CALCIUM CHANNELS OPEN

INCOMING

ACTION

POTENTIAL

CALCIUM

CHANNEL

•••

RECEPTOR

SYNAPTIC

VESSICLES

•••

•••

•••

•••

•••

ION

CHANNEL

•••

•••

•••

ENZYME

the synapse neurotransmitter enters space
THE SYNAPSE: NEUROTRANSMITTER ENTERS SPACE

CALCIUM

CHANNEL

•••

RECEPTOR

•••

SYNAPTIC

VESSICLES

•••

•••

•••

•••

•••

ION

CHANNEL

•••

•••

ENZYME

post synaptic events
POST SYNAPTIC EVENTS
  • IONOTROPIC (LIGAND GATED) CHANNELS
  • VOLTAGE GATED CHANNELS
  • ELECTROPHYSIOLOGICAL PRINCIPLES
ionotropic channels
IONOTROPIC CHANNELS
  • BIND NEUROTRANSMITTER
  • OPEN CHANNEL
  • HYPER OR DE-POLARIZATION
the synapse neurotransmitter binds to postsynaptic receptor
THE SYNAPSE:NEUROTRANSMITTER BINDS TO POSTSYNAPTIC RECEPTOR

CALCIUM

CHANNEL

•••

RECEPTOR

SYNAPTIC

VESSICLES

•••

•••

•••

•••

•••

•••

•••

ION

CHANNEL

•••

•••

ENZYME

how are we wired connections between nerve cells1
HOW ARE WE WIRED?CONNECTIONS BETWEEN NERVE CELLS

AXON

CELL

BODY

AXON

TERMINALS

AXON

HILLOCK

DENDRITES

postsynaptic potentials
IPSPPOSTSYNAPTIC POTENTIALS

EPSP

RESTING

POTENTIAL

TIME

spatial summation
SPATIAL SUMMATION

SIMULTANEOUS

INPUT FROM TWO

SYNAPSES: ABOVE

THRESHOLD

THRESHOLD

TIME

spatial summation1
SPATIAL SUMMATION

SIMULTANEOUS

INPUT FROM TWO

SYNAPSES: ABOVE

THRESHOLD

THRESHOLD

TIME

temporal summation
TEMPORAL SUMMATION

TOO FAR APART IN TIME:

NO SUMMATION

TIME

temporal summation1
TEMPORAL SUMMATION

CLOSER IN TIME:

SUMMATION BUT

BELOW THRESHOLD

THRESHOLD

TIME

the goldman hodgkin katz ghk equation
THE GOLDMAN-HODGKIN-KATZ (GHK) EQUATION

[Ko] + [Nao]

Vm = 60 LOG --------------------------

[Ki] + [Nai]

 IS THE RATIO OF SODIUM TO

POTASSIUM PERMEABILITY

temporal summation2
TEMPORAL SUMMATION

STILL CLOSER IN

TIME: ABOVE

THRESHOLD

THRESHOLD

TIME

how excitation occurs the role of depolarization and hyperpolarization
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)

NEURO TRANSMITTERS
in the space
IN THE SPACE
  • ENZYME “CHEWS UP” LIGAND
  • MASS ACTION CAUSES LIGAND TO DISSOCIATE FROM RECEPTOR
the synapse1
THE SYNAPSE

CALCIUM

CHANNEL

•••

RECEPTOR

SYNAPTIC

VESSICLES

•••

•••

•••

•••

ION

CHANNEL

•••

•••

•••

•••

ENZYME

the synapse2
THE SYNAPSE

CALCIUM

CHANNEL

•••

RECEPTOR

SYNAPTIC

VESSICLES

•••

•••

•••

•••

•••

ION

CHANNEL

•••

•••

•••

ENZYME

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