Biology half-term homework
What is a reflex arc?
A reflex arc is the neural pathway that causes a reflex action. In animals, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. This characteristic allows reflex actions to occur. Reflex action is a rapid automatic and involuntary response to a stimulus which is not under the control of the brain.
If we unknowingly touch a hot object, we immediately move our hand away from it. So moving our hand away on touching a hot iron is an example of reflex action as shown below.
Senses hot object
Response pulls hand away
What is a synapse?
A chemical synapse is a small gap, or commonly referred to ...view middle of the document...
I’ll always be fat." You give up because you feel you are fighting a losing battle. Basically, low serotonin levels attack your ability to "just say no".
The effect of Prozac on the brain?
When serotonin is released from the "sending" nerve cell, the leftover serotonin is normally reabsorbed by an uptake pump. By blocking the uptake pump, Prozac increases the amount of active serotonin that can be delivered to the "receiving" nerve cell. This means that the neurons steep for a longer period of time in the serotonin you already produce. Prozac selectively affects only serotonin which is why Prozac and other similar drugs are called selective serotonin reuptake inhibitors, or SSRIs.
There are other mechanisms as well. The drug blocks the sensor on the axon that tells the cell when enough serotonin has been produced. This causes the axon to release even more serotonin. Finally, over a period of 2-3 weeks, the receiving cell becomes more sensitive to serotonin, and this is the point at which the anti-depressant effect becomes experienced by the...