The Synapse and Neurotransmitters Flashcards
Exam 2
What is the purpose of the synapse?
The site of information flow from one neuron to another neuron
Site of communication from a neuron to (2)
- Another neuron
- Effector (muscle cell)
Presynaptic neuron
Neuron that SENDS impulses through the synapse
Postsynaptic neuron
Neuron that RECEIVES information from the synapse
Each ______ of a dendrite has its own _______
spine; synapse
What are the two types of synapses?
- Electrical
- Chemical
Electrical Synapse
Gap junctions; DIRECT FLOW from neuron to neuron
Chemical synapse
Synaptic cleft requires neurotransmitters to transmit signals; SPACE INBETWEEN
Electrical synapses are used for ____________ of cell groups
synchronicity
There is a greater diversity at chemical synapses because
Different neurotransmitters can have different effects
Are there more electrical or chemical synapses?
Chemical
What are the paired channels in Electrical synapses called?
Connexons
What are the proteins that make up the paired channels?
Connexins
Electrical synapses allow a direct or indirect flow?
Direct
A place in the brain that uses electrical synapses is?
The Pons/Medulla
Why do the pons and the medulla use electrical synapses?
Regulating heartbeat and breathing is a synchronous process, which means that all nerves must fire at once
What are the three types of chemical synapses?
- Axosomatic
- Axodendritic
- Axoaxonal
Axosomatic synapses
Axon attaches to cell bodies
Axodendritic synapses
Axon to dendrite
Axoaxonal synapses
Axon to axon
What is the most common chemical synapse?
Axodendritic synapses
Synaptic vesicles are specialized to release _________ into the synapse
Neurotransmitters
Two parts of Chemical synapses
- Axon terminal of postsynaptic neurons
- NTs receptor region on postsynaptic neurons
Synaptic cleft
Fluid-filled space between the pre and post synaptic neuron
NTs can be ________________ or ________________
Inhibitory or excitatory
What channels are in the receptors?
ligand-gate
Excitatory NTs cause
depolarization
Inhibitory NTs cause
hyperpolarization
Steps of synaptic transmission (5)
- Action Potential arrives at the axon terminal
- VG Ca2+ channels open and Ca2+ enters the axon
- Ca2+ entry causes synaptic vesicles to release NT by exocytosis
- NTs diffuse across the synapse
- Binding of NTs opens ion channels, resulting in graded potentials
Is there one or many types of NTs in the synaptic vesicles?
Many types
Without certain ______, the certain NTs will be ineffective
Receptors
Two types of post synaptic potentials
- EPSP
- IPSP
EPSP
Excitatory postsynaptic potential
EPSP leads to ______
depolarization
IPSP
Inhibitory postsynaptic potential
IPSP leads to _______
Hyperpolarization
A strong enough excitatory cell can cause an
action potential
Two types of summation
- Temporal
2.Spatial
Temporal summation
1 presynaptic neuron; rapid repeat EPSPs in the SAME location; add and sum to produce AP
What causes temporal summation?
a high frequency AP being sent by a presynaptic neuron
Spatial summation
2+ Presynaptic neurons; EPSPs in DIFFERENT parts of the neuron
EPSP and IPSP at the same time cause a
return to resting potential
What are the three ways of termination of a NT?
- Reuptake in presynaptic
- Degradation
- Diffusion
What part of the synapse does the reuptake in presynaptic neuron?
By astrocytes or axon terminal
Degradation
Caused by enzymes
Diffusion
Diffuses away from the synaptic cleft; molecules move from high to low
What is a neurotransmitter?
A chemical substance released at the end of a neuron that communicates with another neuron
What is the three criteria for NTs
NT presented, NT released, NT receptors activated
Why is there more chemical synapses than electrical synapses?
Chemical releases NTs which diversify the post synaptic responses
What are the four categories of NTs?
- Amino Acids
- Monoamides
- Small molecules
- Neuropeptides
3 most common amino acids
- GABA
- Glutamate
- Glycine
GABA
CNS-inhibitory
Glycine
CNS-inhibitory
Glutamate
CNS-Excitatory
3 most common types of Monoamides
- Dopamine
- Norepinephrine
- Serotonin
Dopamine
CNS; learning, euphoria; movement
Norepinephrine
CNS; arousal, flight or fight response
Serotonin (5HT)
Sleep, Mood, Wakefulness
Two types of Neuropeptides
- Substance p-pain sensation
2.Endorphin
Endorphin function
decrease pain sensation
What are the two types of receptors?
Metabotropic and Ionotropic
How do Ionotropic receptors work?
NT binds to sensor; Ions flow freely through ion channel
Is ionotropic fast and brief or slow and long?
Fast and brief
How do metabotropic receptors work?
NT binds to a sensor which activates a g-protein inside the cell; G-protein can open and close nearby ion channels
Is metabotropic fast and brief or slow and long?
slow and long
Two types of pathways
- Diverging pathway
- Converging pathway
Divergent pathways
One presynaptic neuron affects a larger number of postsynaptic neurons
Converging pathways
Many presynaptic neurons converge into a smaller number of postsynaptic neurons
What is the main excitatory NT in the adult brain?
Glutamate