Synapse

Molly Vaughn

Synapses (2nd assignment of CONTROL FREAK)

Motor Neuron p.234 What is a motor neuron? - Muscle fibers are stimulated to contract by motor neurons whose axons are in nerves. The axon of one motor neuron can stimulate from a few to several muscle fibers of a muscle because each axon has several branches. Each branch of an axon ends in an axon terminal that lies in close proximity to the sarcolemma of a muscle fiber. A small gap, called a synaptic cleft, separates the axon terminal from the sarcolemma. This entire region is called a neuromuscular junction.

What is the name neurotransmitter released by motor neurons? - Axon terminals contain synaptic vesicles that are filed with the neurotransmitter acetylcholine. When nerve impulses, traveling down a motor neuron, arrive at an axon terminal, the synaptic vesicles release Ach into the synaptic cleft.

How does botox prevent muscle contraction? - Botox is the trade name for botulinum toxin A, a neurotoxin produced by a bacterium. Botox prevents wrinkling of the brow and skin about the eyes because it blocks the release of Ach into the synaptic cleft, and therefore muscle contraction never occurs.

Cocaine p.268 What does cocaine interfere with at the synapses? - Cocaine is a powerful stimulant in the CNS that interferes with the re-uptake of dopamine at synapse. With continued use, the body makes less dopamine to compensate for the apparent excess in synapse.

What is the effect? - The result is a rush of well being that lasts from 5-30 minutes. Although it seemed at first that cocaine could relieve depression, it soon became apparent that cocaine is extremely addictive and its use is very harmful. During cocaine sprees, the drug is taken repeatedly and at ever-higher doses. The result is sleeplessness, lack of appetite, increased sex drive, tremors, and “cocaine psychosis,” a condition that resembles paranoid schizophrenia. During the crash period, fatigue, depression, and irritability are common along with memory loss and confused state cognition. Drug tolerance leads to withdrawal symptoms, during which cravings for cocaine increase. Cocaine-related deaths are usually due to cardiac and/or respiratory arrest. The combination of cocaine and alcohol dramatically increase the risk of sudden death.

Methamphetamine p.268 What neurotransmitter does meth resemble? - Methamphetamine has a structure similar to that of dopamine, and its stimulatory effect mimics cocaine.

What is the effect? - It reverses the effects of fatigue, maintains wakefulness, and temporarily elevates the mood of the user. After the initial rush, there is typically a statue of high agitation that, in some individuals, leads to violent behavior. Chronic use can lead to what is called amphetamine psychosis resulting in paranoia, auditory and visual hallucinations, self-absorption, irritability, and aggressive, erratic behavior. Drug tolerance, dependence, and addiction are common, and hyperthermia, convulsions, and death can occur.

Heroin p. 268 Where is heroin derived? - Heroin is derived from the resin of sap of the opium poppy plant, which is grown from Turkey to Southeast Asia and in parts of Latin America. Heroin is a slightly addictive drug that acts as a depressant in the nervous system. The opiates, which also include morphine and codeine, have pain-killing effects.

What is heroin converted to that can bind opiate receptors in the brain? - Heroin is the most abused opiate because it is rapidly delivered to the brain, where it is converted to morphine. Morphine binds promptly to opioid receptors, and the result is a rush sensation and euphoric experience.

What do the opiate receptors do? - Opiates depress breathing, activate the reward circuit, block pain pathways, cloud mental function, and sometimes cause nausea and vomiting. Long-term effects of heroin use are addiction, hepatitis, HIV/AIDS, and various bacterial infections because of shared needles.

Marijuana p. 269 What is THC? - THC is tetrahydrocannabinol.