Updated: Oct 23, 2019
Step by step - describe a nerve signals way from a dendrite in one nerve cell to an axon terminal in another. Use as many appropriate terms as possible!
The job of the nerve cell is to receive a stimuli through its dendrite propagate it along one direction, conduct it
through the axon and transmit it to the next through the axon terminals to the dendrite of the postsynaptic neuron, which will continue the action potential to its own axon terminal and so on. The depolarization is prevented from going backwards because of the Na channels (in this case) refractory state of which the channels will go through, being unable to open again.
An electrical pulse is needed, as a stimulus given to the dendrite and the electrical impulse has to be strong enough and re amplified throughout the process to remain with the same strength throughout the impulse process.
A stimulus needs to be passed the threshold, in order to send an action potential, otherwise the voltage response of the cell will be proportional to the stimulus electrical pulse. During the neuron's resting phase only the leak Ka channels are open in order to maintain the resting phase and charge difference from the inside and outside. As an action potential is made, the voltage gated Na channels in the membranes of the axon open in response to the depolarization and Na ions get into the membrane along the concentration gradient, changing the charge from the resting phase -70mV to a positive charge in the inside and negative one on the outside, being the rising phase called depolarisation. By +40 mV the Na channels will go into refractory state and unable to open again until the charge is back to its resting phase and the voltage gated K channels open instead in order to restore the resting phase equilibrium again. The hyperpolarization occurs because a lot of voltage gated K channels are open making the refractory state become more negative than the resting phase. The neuron reaches back to the resting phase as the K leak channels open to help balance out the charges back to its original phase.
The action potential by now has reached the presynaptic terminal, which causes the voltage gated Ca ion channels to open and Ca ions diffuse in causing the synaptic vesicles to release acetylcholine (or some other neurotransmitter) by exocytosis that will diffuse out of the presynaptic terminal across the synaptic cleft and bind to the ligand gated Na ion channels that will be forced to open and Na
ions will diffuse through changing the charge on the inside to positive, enough to reach threshold in order to cause an action potential through the post synaptic neuron to continue the stimulus.
Describe how the fact that drugs such as cocaine and alcohol are similar to neurotransmitters are important to their function and outline how neonicotinoids work as a pesticide.
Drugs and alcohol can disrupt or enhance one's neurotransmitters within the brain. Neurotransmitters can be
carrying inhibitory messages across the synapses, while others carry excitatory messages. So one drug can make your neurotransmitters more enhances, inhibited or exaggerated. Antagonistic drugs however interfere with the transmission of the message thus decreasing the neurotransmitters effect on the body.
A neonicotinoid pesticide are very toxic for insects and specially beneficial species such as bees. They block specific neurons in insects, but are less harmful to warm blooded animals.
They both act and look like a neurotransmitter, thus they connect to the postsynaptic neurons receptor, either blocking an action potential or triggering one and interfering the body's natural response to the external/internal environment.
PROPAGATION OF NERVE IMPULSE