Synapse stuff Flashcards
Dendrite
branched nerve fibres which receive nerve impulses and pass them towards a cell body.
Cell body
where organelles such as the nucleus are found.
Axon
a single nerve fibre that carries nerve impulses away from a cell body which is insulated by a fatty sheath
Myelin Sheath
The role of the myelin sheath is to insulate the axon and speed up the transmission of nerve impulses along the neuron. This surrounds axons.
Gial Cells
produce the myelin sheath and support neurons.
Myelin and Myelination
Myelination continues from birth to adolescence.
Certain diseases destroy the myelin sheath causing a loss of co-ordination.
Responses to stimuli in the first two years of life are not as rapid or co-ordinated as those of an older child or adult.
Check topic pitctures
Good
Re-uptake
• Re-uptake – the neurotransmitter is reabsorbed back into the presynaptic neuron and restored inside a vesicle ready to be used again. For example, noradrenaline.
Enzyme degradation
Enzyme degradation – neurotransmitter is broken down by an enzyme into smaller inactive product which are then reabsorbed by the presynaptic neuron and resynthesised into active neurotransmitter.
Neurotransmitter at synapse basic
Neurons connect with other neurons or muscle fibres at a synaptic cleft. Neurotransmitters relay impulses across the synaptic cleft.
Neurotransmitter journey
Neurotransmitters are stored in vesicles in the axon endings of the presynaptic neuron. They are released into the cleft on arrival of an impulse. They diffuse across the cleft and bind to receptors on the membrane of the postsynaptic neuron.
What can receptors determine?
Receptors determine whether the signal is excitatory or inhibitory.
The need for removal of neurotransmitter by enzyme or re uptake
The need for removal of neurotransmitters by enzymes or reuptake to prevent continuous stimulation of postsynaptic neurons.
Weak stimuli
Synapses can filter out weak stimuli arising from insufficient secretion of neurotransmitterS
Threshold
A minimum number of neurotransmitter molecules must attach to receptors in order to reach the threshold on the postsynaptic membrane to transmit the impulse
Summation
Synapses can filter out weak stimuli arising from insufficient secretion of neurotransmitters.
Convergent neural pathways can release enough neurotransmitter molecules to reach threshold and trigger an impulses
Reward pathway activated when
The reward pathway is activated when an individual engages in a behaviour that is beneficial to them, for example eating when hungry
Reward pathway
The reward pathway involves neurons which secrete or respond to dopamine.
Endorphins function
Endorphins are neurotransmitters that stimulate neurons involved in reducing the intensity of pain.
Endorphins produced increases in response to
Endorphin production increases in response to severe injury, prolonged and continuous exercise, stress and certain foods.
Dopamine
Dopamine is a neurotransmitter that induces feelings of pleasure and reinforces particular behaviour by activated the reward pathway in brain
Increased level of endorphins linked to pleasure
Increased levels of endorphins are also linked to the feelings of pleasure obtained from activities such as eating, sex and prolonged exercise.
A and A use
Many drugs used to treat neurotransmitter- related disorders are agonists or antagonists
Agonist
Agonists are chemicals that bind to and stimulate specific receptors mimicking the action of a neurotransmitter at a synapse
Antagonist
Antagonists are chemicals that bind to specific receptors blocking the action of a neurotransmitter at a synapse.
D. What do other drugs do
Other drugs act by inhibiting the enzymes that degrade neurotransmitters (I think this is like competitive inhibition) or by inhibiting reuptake of the neurotransmitter at the synapse causing an enhanced effect.
Recreational Drugs
Recreational drugs can also act as agonists or antagonists.
Recreational drugs affect neurotransmission at synapses in the brain altering an individual’s mood, cognition, perception and behaviOur
R Drugs Reward Pathway
any recreational drugs affect neurotransmission in the reward pathway of the brain.
Drug addiction is caused by repeated use of drugs that act as antagonists.
SAN Lewis acronym Antagonists block specific receptors causing the nervous system to increase both the number and sensitivity of these receptors. This sensitisation leads to addiction where the individual craves more of the drug.
Drug tolerance is caused by repeated use of drugs that act as agonists.
Agonists stimulate specific receptors causing the nervous system to decrease both the number and sensitivity of these receptors. This desensitisation leads to drug tolerance where the individual must take more of the drug to get an effect.
