Unit 4: Synapses and NeuroTs Flashcards
What is a synapse?
Is the site of communication between two neurons or between a neuron and effector target. It is where the impulse passes over either in a chemical form via neurotransmitters or electrical via transferring ions. They are unidirectional.
Describe how neurotransmitters in a synapse work?
The action potential arrives from the axon hillock. (Depolarisation) When it reaches the terminal button, it opens voltage-gated calcium channels. the influx of calcium interacts with the vesicles (and a province called synapsin) containing neurotransmitters and they move towards the presynaptic membrane and exocytose. The now empty vesicle is taken back to the cell body to be reused.
The neurotransmitters passively diffuse across the synaptic cleft and bind with ligand-gated receptors on the postsynaptic membrane(dendrites). This would either be EPSP IPSP in a neuron or the resultant effect on the effector target.
Removed from the synaptic cleft afterwards
What happens during an excitatory graded potential?
This is known as an ESPS, which is the excitatory postsynaptic potential, meaning that on the postsynaptic neuron sodium channels open up (ligand-gated channels). This means that the neuron is closer to the threshold potential which triggers an action potential.
What happens during an inhibitory graded potential?
This is known as an ISPS, which is the inhibitor postsynaptic potential, meaning that on the postsynaptic neuron potassium channels open up (ligand-gated channels). This means that the neuron is further from threshold potential which doesn’t trigger an action potential. Calcium (CL-) channels may be opened, further dropping membrane potential moving away from threshold potential- hyperpolarisiation
What are neurotransmitters?
Chemical messages that transmit a signal, from a neuron, across the synapse to the target cell and then are removed from the synaptic cleft. They are produced in the cell body and stored at the axon terminal
What are the different types of neurotransmitters and are some examples?
- Amino acids- Glutamate/GABA/Glycine
- Monoamines- Dopamine/Epi/NorEpi (they derive from tyrosine and are sometimes called catecholamines) and serotonin is an indolamine (subclass) and derives from tryptophan
- Ach
Where is Ach used?
it is found at the neuromuscular junction of skeletal muscle (always excitatory), the basal ganglia of the brain, the ganglion for syp and parasym NS (excitatory) and postsynaptic neuron of the parasym NS and sweat glands.
Where is serotonin used(5-HT)?
5-hydroxytryptamine is used to regulate limbic function (emotion/mood, hunger, libido, preception, temperature) and sleep. It also regulates the digestive system. it is an indolamine which is a subclass of monamines.
Where is dopamine used?
Dopamine is produced in the substantia nigra and is used in movement, implicated in reward pathways and addictive pathways (brain releases dopamine in response to pleasurable experiences). It is a monamine and can be classed as a catacholamine.
Where is Norepinephrine used?
It is found in the locus coeruleus, projecting to the brain, and is usde in arousal, attention, anxiety, and decision making. It is also found in the ANS in the postganglionic neurons of the symp NS(excitatory). It is a monamine and can be classed as a catacholemine.
Where is glutamate used?
It is found widely in the CNS and has a primary excitatory function. it is the metabolic precursor of GABA. It is an amino acid
Where is GABA used?
Gamma-aminobutyric acid has a large inhibitory function in the CNS- mainly the brain. most of the time the brain is under heave inhibition otherwise there is seizure-like activity where there is overstimulation of neurons. (alcohol initially decreases GABA effects but alcohol is an inhibitory drug so increases GABA effects long term)
What are opiates and why are they important?
They are drugs that are derived/related to the opium poppy. They can stimulate the release of dopamine (they can also have a secondary effect on norepi and glutamate). This produces a pleasurable feeling associated with the neurotransmitter. They also act on opiate receptors in the brain to increase feelings of pleasure and decrease pain
What are endorphins?
Endorphins are endogenous peptides that the body produces in response to stress. They also stimulate areas of the brain and associated with pleasure and interact with our opiate receptors.
Exercise is a form of stress so the body releases endorphins to counteract pain stimuli.
People in car crashes don’t realise that they are injured due to endorphins.
