Synapses Flashcards
Why is Chemical Conduction slower than Electrical Conduction?
Electrical synapse has no time gap
Chemical synapses have a delay because of the synaptic cleft
Differentiate Based on Ion Flow:
Electrical Synapse
Chemical Synapse
E: Bidrectional
C: Unidirectional
3 Different Types of Intercellular Communication
Paracrine
Endocrine
Synaptic
Synaptic Transmission Pathway
- Nerve is Stimulated
- AP travels down to terminal end causing depolarization of pre-synaptic membrane
- Voltage gated Ca channels in pre-synaptic membrane open
- Ca ions from extracellular compartment enters, increasing intracellular Ca concentration
- Ca ions bind to synaptic vesicles containing NT causing their release from the actin cytoskeleton (Via Synapsin)
- Synaptic vesicles move toward and dock at the presynaptic membrane
- Interaction with docking proteins creates a fusion pore through which NT pass by exocytosis
- NT released from presynaptic membrane, transverses the synaptic cleft, and binds to its receptors at the postsynaptic membrane
Function: VAMPs
- Sensitive to Ca2+
- Serves as a sensor for vesicle to move towards pre-SM
Function: Synapsin
Connects vesicles to actin filament
Discuss the role of calcium ions in synaptic transmission
They are essential to release neurotransmitters
Define: Excitatory Postsynaptic Potential
Depolarization of a membrane that increases excitability of the cell
Drives membrane towards the threshold, making it more positive
Define: Localized Ligand-Gated Event
A single EPSP generally does not produce an AP, more are needed to reach firing level
Define: Inhibitory Postsynaptic Potential
Depolarization or hyperpolarization of a membrane that decreases the cells excitability
Major Ions Involved in:
EPSP
IPSP
EPSP: Na
IPSP: Cl, K
Peripheral Synapses are purely?
Excitatory
Central Synapses are Excitatory or Inhibitory?
Both
Is a Neuromuscular Junction a Peripheral or Central Synapse?
Peripheral
[Peripheral vs. Central Synapse]
Connections
Peripheral: 1 Motor Neuron -> Several Muscle Fibers
Central: Multiple Connections
[Peripheral vs. Central Synapse]
Ion Channels
Peripheral: Single
Central: Different Ion Channels
[Peripheral vs. Central Synapse]
Type of Input
Peripheral: Excitatory Only
Central: Excitatory and Inhibitory
[Peripheral vs. Central Synapse]
Neurotransmitter
Peripheral: Acetylcholine Only
Central: Different Types
Define: Temporal Summation
Overlap in time of firing neurons resulting in an AP
Define: Spatial Summation
Overlap in location of synaptic potentials that can result in an AP
Define: Long-Term Potentiation
Increased Ca causes increase in NT which strengthens the post-SM
Lasts for several hours-days
Define: Posttetanic Potentiation
Repetitive stimulation of pre-synaptic membrane increases postsynaptic membrane potential
When impulse is removed, there is still a small increase in amplitude of postsynaptic potentials for some time because of opened calcium-gated channels
2 Types of Postsynaptic Inhibition
Indirect
Direct
Define: Direct Postsynaptic Inhibition
Inhibitory neuron releases inhibitory NTs causing increase in Cl- conductance, results in hyperpolarization
Define: Indirect Postsynaptic Inhibition
Refractory Period
Define: Pre-synaptic Inhibition
Inhibitor acts on the excitatory axon and decreases its capacity to deliver an excitatory impulse
Results in a hyperpolarization of the ending such that if a normal impulse arrives, it still cannot fire
Function: Acetylcholine
Control of movement
Cognition
Autonomic control
[Acetylcholine]
Inhibitory in?
Excitatory in?
Inhibitory: Heart
Excitatory: Neuromuscular Junction
Function: Catecholamine
Feeling or Emotion
Alertness
Pain Modulation
Vasoconstriction/Dilation in Smooth Muscles of BVs
Function: Dopamine
Control of Movement
Affect
Reward
Function: Serotonin
Rousal (from sleep)
Mood
Modulation of Pain
Gut Regulation
Function: Glutamate
General Excitation
General Sensation
Function: Glycine
General Inhibition
Function: GABA
General Inhibition
Effect: Tetanus Toxin
Binds with docking proteins inhibiting release of NTs
May inhibit inhibitory neurons causing spastic motions
Effect: Botulinum Toxin
Inhibits muscle contractions
Botulinum types and where they bind
A&E: Docking protein SNAP25
B, D, F & G: Synaptobrevin
C1: Syntaxin
Effect: Conotoxin
Acts on synapses
Treatment for pain and seizures in epileptic patients
Define: Ionotropic Receptors
Contain ion channels that allow passage of specified ions through membrane
“Fast” Synaptic Transmission
Define: Metabotropic Receptors
Coupled to G-Protein that serves as second messengers that affect ion channels
“Slow” Synaptic Transmission
Fast synaptic transmission uses what receptors?
Ionotropic Receptors
Slow synaptic transmission uses what receptors?
Metabotropic Receptors
