Presentation on theme: "This powerpoint will help you with your WS and with the computer based activity. You do not need to memorize this info, just understand it as we discuss."— Presentation transcript:
This powerpoint will help you with your WS and with the computer based activity. You do not need to memorize this info, just understand it as we discuss it. Later: you will have a reference sheet to look at while you do your WS. This is a class set so please do not take them with you. It is also available on the webpage along with this powerpoint.
Neurotransmitter: A chemical or peptide substance that transmits nerve impulses across synapses (space between two neurons), that effect motor coordination, mood, behavior, and other physiological activities, such as heart rate. Different types of NT have different actions based on tissue type, receptor type, etc.
Scientists have identified at least fifty neurotransmitters in the nervous system, and there may be several dozen more. There are four groups of neurotransmitters: 1) acetylcholine, 2) amino acids, 3) biogenic monoamines, and 4) neuropeptides.
Neurotransmitters are classified as excitatory or inhibitory according to their effects on postsynaptic membranes. Excitatory : if activation of the receptor causes depolarization of the membrane and promotes action potential generation. Inhibitory : if the activation of the receptor causes hyperpolarization and depresses action potential generation Important Point: So: release of an NT may cause something to happen OR cause it not to happen!! AND an action potential may cause something to happen OR cause it not to happen!!
After the release of the NT: It is necessary to turn OFF the signal to control the activity at the synapse Enzymatic Breakdown: An enzyme can break down the neurotransmitter chemical into its component parts, Reuptake: the presynaptic neuron can have transporters, which suck the neurotransmitter up back into the synaptic buton, either to be shoved back into vesicles, or to be degraded
A. Disrupt the synthesis of neurotransmitter. A drug can block a cell's ability to manufacture the neurotransmitter, thus decreasing its availability. B. Disrupt the transport of neurotransmitter to axon terminal. Once a neuron has manufactured a neurotransmitter, the transmitter needs to be stored in vesicles near the terminal end of the neuron for it to be released. A drug can block this transportation from occurring, thus decreasing the neurotransmitter's availability. .
C. Affect storage of the neurotransmitter. A drug can make the storage vesicles "leaky", allowing neurotransmitter to be destroyed within the cell. This will reduce the availability of the neurotransmitter in the synapse. D. Cause premature release of neurotransmitter. By forcing neurotransmitter into the synapse without the nerve firing, the immediate effect will be an increase in neurotransmitter availability in the synapse. If this happens for too long, the forced release will outstrip the neuron's ability to manufacture the neurotransmitter, leading to decreased availability in the long run.
E. Blocks reuptake of neurotransmitter. By stopping the releasing cell from taking the released neurotransmitter back into the cell, the neurotransmitter remains available within the synapse. F. Disrupt the actions of enzymes. By stopping the enzymes from breaking down released neurotransmitters, the neurotransmitter remains available within the synapse.
Let's check this idea using one neurotransmitter as an example: norepinephrine. As you may recall, norepinephrine is an excitatory neurotransmitter that has effects in the sympathetic nervous system and in the brain. In the brain, norepinephrine has mood and other effects. Increased levels of norepinephrine result in increased sympathetic nervous system activity, such as increased heart rate and blood pressure, and is related to heightened emotional arousal, including excitement and anxiety. Decreased levels of norepinephrine result in decreases in sympathetic nervous system activity and are related to feelings of lethargy and depression.