The cells of the nervous system and neurotransmitters at synapses Flashcards
What is the function of dendrites
receive nerve impulses and pass them to the cell body
What is the function of cell body
contains the nucleus and most of the cytoplasm
control the cells metabolism and contains ribosomes
What is the function of axon
carries nerve impulses away from a cell body
What is the myelin sheath
a layer of fatty material surrounding the axon
What is the function of a myelin sheath
the myelin sheath increases the speed of impulse conduction (transmission)
What is myelination
the development of myelin round axon fibres of individual neurons
When does myelination occur
continues from birth to adolescence
The neurons in the spinal cord transmitting impulses to the lower body are not fully myelinated until about 2 years of age.
what is the result of this
responses to stimuli in the first 2 years of life are not as rapid or coordinated as those of an older child or adult
Certain diseases damage or destroy the myelin sheath what can this lead too
a loss of muscular coordination
What is the function of Glial cells
produce the myelin sheath
support neurons
What is a synapse
A gap between two neurons
Where do neurons connect with other neurons or muscle fibres at
Synaptic cleft
What are the chemicals that relay the impulse across the synapse called
Neurotransmitters
What is needed for neurotransmitter synthesis
ATP
Describe neurotransmitters
They are released into the cleft on arrival of an impulse
They diffuse across the synaptic cleft and bind to receptors on the membrane of the postsynaptic cleft
What is the role of vesicles at a synapse
vesicles store neurotransmitters in the axon ending of the presynaptic neuron and release them at the synapse when an impulse arrives
Name two neurotransmitters
acetylcholine
noradrenaline
What is the role of receptors at the synapse
neurotransmitters bind with receptors and receptors determine whether signal is excitatory or inhibitory
For the impulse to continue across the synapse what is needed
a threshold/minimum number of neurotransmitters is needed
Why do neurotransmitters need to be removed from the synapse
to prevent continuous stimulation of post synaptic neurons
How are neurotransmitters removed from the synapse
by enzyme degradation or reuptake
Give an example of a neurotransmitter removed by an enzyme
acetylcholine is broken down by an enzyme to non active products
Give an example of a neurotransmitter removed by uptake
noradrenaline is removed by reuptake and stored in vesicles ready for reuse
What happens if there is insufficient secretion of neurotransmitter
synapses can filter out weak stimuli arising from insufficient secretion of neurotransmitters
What is meant by the term summation with reference to nerve impulses
a series of weak stimuli trigger an impulse
because a threshold of neurotransmitters has been reached
What determines whether a signal is excitatory or inhibitory
receptors
Where do neurons connect with other neurons, muscle fibres and endocrine glands at
synapse
Where are neurotransmitters stored an released
stored in vesicles and released into the synaptic cleft
What happens on arrival of an electrical impulse
neurotransmitters diffuse across the cleft and bind to receptors on the postsynaptic nerve ending
Describe acetyl choline mode of action leave
always excitatory at skeletal muscle
elsewhere excitatory or inhibitory depending on type of receptor present
Describe noradrenaline and dopamine mode of action leave
excitatory or inhibitory depending on type of receptor present
What type of neural pathway gives the best chance of neurotransmitter molecules to reach the threshold and trigger an impulse
converging neural pathway
Describe how an impulse is transmitted between two neurons
vesicles release neurotransmitters
neurotransmitters diffuses across the synaptic cleft
neurotransmitter bind to receptor
a minimum number/ threshold of neurotransmitter is required
