Chapter 8 Flashcards
What is an electrical synapse
When the pre and postsynpatic cells are touching allowing electrical signals to pass across
What is a chemical synapse
When there is a space between 2 neurons and chemicals are released into the synaptic cleft effecting the postsynaptic neuron
What are the sparks
Electrical synapses
What are the soups
Chemical synapses
What is used for communication within a neuron
Action potentials
What is communication between neurons
Synaptic transmission
Who believed in electrical synapses
Golgi
Who believe in chemical synapses
Cajal
Who devised the first definitive experiment to prove the existence of chemical synapses
Otto Loewi in 1921
How did Otto Loewi determine the existence of chemical synapses
Put 2 frog hearts in separate beakers connected by a tube, one hearts vagus nerve was stimulated causing the heart to contract slower, and eventually the other heart start to contract slower
How many synapses are there per neuron
Thousands
How many synapses are there in the brain
Trillions
Where are electrical synapses more common
Invertebrates
Where are chemical synapses more common
Mammals
True or False:
The number of synapses per neuron varies greatly
True
At an electrical synapse what does activation of the presynaptic cell result in
An action potential in the postsynaptic cell
True or False:
Synaptic transmission at an electrical synapse depolarize the postsynaptic cell above threshold
True
What is the gap junction
Specialized region of contact between 2 cells
What is the gap bridged by
Gap junction channels
What are gap junction channel called
Connexons
What is a connexon made of
6 connexin
Is the stimulation of the postsynaptic cell delayed or virtually instantaneous in an electrical synapse
Virtually instantaneous
What are electrical synapses good for
Things that require an extremely fast response
Does an electrical synapse need to reach threshold for a response in the postsynaptic cell
No they can be graded
Are connexons full channels or hemi-channels and why
Hemi-channels because you need 2 connexons to make a full channel
Are connexons always open
No the shift to open
What connect the 2 connexons
Extracellular loops
True or False:
Electrical synapses allow for direct passage of current between cells
True
What are 2 things electrical synapses are good for
- Escape response
2. Protection
What is an example of the escape response
Goldfish tailwhip
What is an example of protection
Aplysia ink release
What causes the explosive release of ink in the aplysia
Stimulation of the tail and firing of 3 specific neurons synchronously
What is the stimulation of the aplysia tail activating 3 neurons an example of
Divergent communication
Are electrical synapses present in mammals if so where
Yes in the brain
Is there structural continuity to a chemical synapse
Nope
What fills the void between neurons
Synaptic cleft
What do chemical synapses rely on
Diffusion of NT
What is a NT
A chemical that binds to a receptor on the postsynaptic cell
What is the synaptic cleft
Space between 2 cells at the active zone
What is an active zone
Dark areas or postsynaptic density
What are the steps of activity in a chemical synapse (6)
- Action potential arrives
- Ca2+ enters
- Vesicles fuse with presynaptic membrane
- NT is released through exocytosis
- NT diffuses across synaptic cleft
- NT binds to receptors on the postsynaptic cell membrane changing the postsynaptic membrane potential
What are the 2 types of NT receptors
- Ionotropic
2. Metabotropic
What is an ionotropic receptor
Ligand gated ion channel
What is a metabotropic receptor
Stimulation of a second messenger
Does a metabotropic receptor have a pore
Nope
Electrical synapse vs Chemical synapse:
Distance between pre and postsynaptic cell membranes
Electrical: Very close
Chemical: A bit farther
Electrical synapse vs Chemical synapse:
Cytoplasmic continuity
Electrical: Yes
Chemical: No
Electrical synapse vs Chemical synapse:
Components
Electrical: Gap junction channels
Chemical: Vesicles at active zones
Electrical synapse vs Chemical synapse:
Agent of transmission
Electrical: Ion current
Chemical: Chemical transmitter
Electrical synapse vs Chemical synapse:
Synaptic cleft
Electrical: Virtually absent
Chemical: Significant 1-5 mm
Electrical synapse vs Chemical synapse:
Direction of transmission
Electrical: Bidirectional
Chemical: Unidirectional
What are the advantages of chemical synapses (2)
- Each NT can have different effects on the postsynaptic cell
- Allow complex modulation
What are the disadvantages of chemical synapses (2)
- SLOW
2. Expensive
What are the advantages of electrical synapses (3)
- FAST
- Cheap
- Effects are short term
What are the disadvantages of electrical synapses (2)
- Difficult to modulate
2. Effects are short term
