Unit 2.4: Cell-to-cell Communication Flashcards
What are the 3 components of the synapse?
- presynaptic cleft - axon terminal
- synaptic cleft - space between cells
- postsynaptic cleft - membrane
What are the 2 types of synapses?
- Electrical
2. Chemical
What are electrical synapses?
Gap junctions allow direct electrical signaling between cells
These synapses are uncommon and occur mainly in CNS
What are chemical synapses?
Information is carried via neurotransmitter one cell to another
Vast majority of synapses
What is the synapse called between a neuron and an effector?
Neuroeffector
What are the events at the synapse?
- AP depolarization wave travels down the axon and depolarizes the axon terminal in the presynaptic cell
- This depolarization wave triggers the opening of voltage-gated Ca2+ channels in the presynaptic cell membrane
- Calcium entry signals synaptic vessels in presynaptic cell to release neurotransmitters
- Neurotransmitters diffuse across synaptic cleft
- Binds with specific receptors on postsynaptic membrane
- Receptor-neurotransmitter complex opens ion channels in postsynaptic cell membrane
- Results in depolarization or hyperpolarization
- Bound neurotransmitter is degraded/diffuses back in synaptic cleft
- Neurotransmitter is stored in presynaptic vesicles until next action potential
What’s the kiss and run?
Docking protein interacts with the vesicle
Ca2+ comes in, docking protein opens a space in vesicle and releases neurotransmitters
When signal stops, it closes and goes back to axon
What are the 2 responses neurotransmitters can create in the postsynaptic cell?
- Direct responses
2. Indirect responses
What are direct responses?
Fast synaptic potential
Response is quick and does not last long
Via interaction with an ion channel
What are indirect responses?
Slow synaptic potential
Responses is slow but lasts longer
Via signal transduction mechanisms, uses G proteins via a 2nd messenger response system
What are the 6 types of neurotransmitters?
- Acetylchoine
- Biogenic amines
- Amino acids
- Neuropeptides
- Purines
- Gases
What are acetylecholines?
Synthesized from choline & acetyl CoA
Catalyzed by enzyme choline acetyl transferase (CAT)
What are neurons that secrete or have receptors for ACh called?
Cholinergic
What are the 2 types of cholinergic receptors?
- Muscarinic, coupled to G-proteins, slower response
2. Nicotinic, receptor operated channels, faster response
What are biogenic amines?
contain an amine group (NH2)
derived from single amino acids
What are amino acids in CNS?
most abundant neurotransmitter in CNS
Glutamate, aspartate = released at excitatory synapses
Glycine, gamma-aminobutyric acid (GABA) = released at inhibitory synapses
What are neuropeptides?
Variety of peptides secreted by the nervous system
What are purines?
Nucleotides that act as neurotransmitters
What are examples of purines?
adenosine, AMP, ATP
What do purines bind to?
Purinergic receptors in the CNS and other excitable tissues
What are gases?
Nitric oxide (NO) is an unstable gas synthesized from oxygen & arginine Catalyzed by Nitric Oxide Synthase
How is NO stored?
not stored in vesicles, release is controlled via NOS regulation
How is NO degraded?
Degrades quickly on its own, no enzyme assistance
How is the neurotransmitter inactivated?
- Neurotransmitter can diffuse away from the synapse
2. neurotransmitter could be inactivated by enzymes in the synaptic cleft
What is acetylcholine degraded by?
Acetylcholine sterase
Where is the greatest variety of neurotransmitters found?
CNS
What are the 2 main neurotransmitters found in PNS?
- Acetylcholine
2. Norepinephrine & Epinephrine
