Test 2 Synapse

Synapse (to connect)
How two neurons communicate/How they exchange information
2 types of synapse
1. electrical
Electrical synapse
* simple synapses-cells have direct connections with each other
* Neurons are connected via gap junction-simplest type of cell to cell communication
*No Delay-very fast synapse of exchange of ions between the neurons
Gap Junction
*made of proteins referred to as connexon-which are 6 sided channels
gap junction
During _______ communication ions can diffuse from one cell to the next cell.
Electrical synapses are found in....
1. escape reflex neurons (invertebrates)
2. Epithelial cells (gut)
3. Cardiac muscle cells (heart)
Chemical Synapse
* Has more stages of activity (3 components) and is more complicated than electrical synapse
3 components of Chemical Synapse
1. Presynaptic component or stage
2. Posynaptic component or stage
3. Inbetween these two components or stages is a cleft called synaptic cleft
Chemical Synapses are found in....
* almost all mammalian neurons
Presynaptic Stage
(chemical synapse)
1. invasion of the synaptic terminal by an action potential
2. depolarization of the terminal(cell) - this depolarization results in influx(increase) of calcium ions into the cell
3. Ca++ influx (opening of voltage-gated Ca++ channels)
4. neurotransmitter release (Ca++ dependent, exocytosis of vesicles)
5. diffusion of the neurotransmitter across the synaptic cleft
(from the cell membrane)
(chemical synapse)
*Presyanptice stage
*the entrance of calcium(Ca++) ions into the cell triggers this process which releases the contents of small structures in the cell called vesicles
(chemical synapse)
* contain neurotransmitters -during exocytosis they release their neurotransmitters into the synaptic cleft-this starts the postsynaptic stage
Postsynaptic stage
(chemical synapse)
6. binding of the neurotransmitter to postsynaptic receptors of the cell membrane
7. Binding of neurotransmitters result in the opening of postsynaptic ion channels
8. entrance of the neurotransmitter to postsynaptic neuron
9. changes in postsynaptic membrane potential
10. re-uptake or break down of neurotransmitter to presynaptic, postsynaptic, or other neurons
(Chemical synapse)
When the neurotransmitters go to the vesicles in the presynaptic membrane
Ligand gated channels
open chemical synapse
voltage gated channels
open electrical synapse
graded potential=
can add up-IPSP and EPSP
Sodium Potasssium Active Pump
*active transport pump
*Pump is an electrogeneric pump that generates electricity
**Pumps 3 Na+ ions out of the cell
**Pumps 2 K+ ions into the cell
synaptic bouton
axon terminal
List of neurotransmitters
*serotonin (sleep cycle)
*melatonin (sleep cycle)
* adensoine
Excitatory neurotransmitters in the nervous system
* glutamic acid
*acetylcholine (associated with the heart)
*Aspartic acid
Inhibitory neurotransmitters in the nervous system
Electrical and chemical synapses operational differences
Operational Differences
1. no delay 1. delay
2. bidirectional 2. unidirectional
3. no amplification 3. amplification
4. no sensitivity to 4. sensitivity to
metabolic rate, metabolic rate,
pharmacology, pharmacology,
and temperature and temperature
Electrical and chemical synapses morphological differences
Electrical Chemical
Morphological Differences
5. needs size match 5. no size match needed
6. direct connection 6. synaptic cleft
7. gap junction 7. vesicles
8. no receptors 8. receptors