For this assignment you will get an opportunity to learn about the various components of biological psychology while gaining insight into a self-selected disease or disorder. Se

Hormones and Drugs.html

Hormones and Drugs

Like neurotransmitters, hormones are endogenous substances (chemicals that exist in the body) that influence the body and bring about changes in organs. Unlike neurotransmitters, hormones are secreted by the endocrine glands into the bloodstream so that the hormones can spread throughout the body and make a long-distance change. You can think of a released hormone as dispersed pinecone seeds in a river after they fall from a tree. Pinecone seeds can flow with the river, go just about anywhere, and get picked up by anything that is receptive to them. Like neurotransmitters, hormones must bind to a receptor for a change to occur. However, hormones are different from neurotransmitters because the changes that hormones make are often more long-term.

Psychoactive drugs are exogenous substances that are introduced into a person's body; they are called psychoactive because they can alter the mind. Some of these substances, such as amphetamines, alter behavior by releasing neurotransmitters like dopamine when they attach to specific receptors in the brain. Other drugs such as heroin (a powerful opiate drug that can alter one's sense of mood and perception of pain) actually bind to the body's opiate receptors, mimicking the endogenous chemicals. Exogenous opiates and other drugs that have similar mechanisms of action not only bind but also can activate the receptors as if they were the neurotransmitter. When a substance can mimic the brain's neurotransmitter, it is called an agonist. Taking an agonist is like using a copy of the key that opens the door to your house. It is not the brain's natural chemical, but it acts exactly the same.

Nerves.html

Nerves

Each of us has about one hundred billion neurons in our 3-pound brain. Neurons are responsible for sending messages within certain localized areas and they are the means of communication in the brain. All of your bodily functions, including your movements and thoughts, are dependent on neuronal functions. Let’s examine what neurons look like and how they work.

The dendrites, connected to the soma (cell body) of a neuron, receive information from other neurons. Like a tree, these dendrites have branches called dendritic arborizations (note: arbor means tree). Dendrites are the starting point for the electrical impulse that enables neurons to communicate. In addition, like a tree, neurons have something similar to a trunk. The trunk of a neuron projects from the cell body and is called an axon. The electrical signal that starts at the dendrites is propagated from the cell body down the axon to the end. Many neurons also have a coating on their axons, which is called myelin. Myelin, made by glia cells, helps the electrical current move faster down the axon. Because myelin coats the axon, it is somewhat analogous to the bark of a tree. However, myelin has breaks in the sheath, which make the electrical current move faster as it jumps from one break to another.

The last part of the tree analogy involves the roots. Similar to the roots of a tree, the axon terminals branch out, and the ends of the branches are referred to as terminal buttons (pronounced boo-tons). The neuron releases chemicals from the buttons, and the released chemicals are then able to cause reactions in other neurons.

Additional Materials

View a Pdf Transcript of Various Types of Neurons

Neurotransmitters.html

Neurotransmitters

What happens when the neurotransmitter is released from the neuron? A chemical diffuses through a fluid-filled space referred to as a synaptic cleft and other neurons that are in the vicinity have an opportunity to receive the neurotransmitter. They will receive it if it binds to a receptor on their dendrites.

Regardless of how a specific neurotransmitter works, if it is going to make a change in another neuron, it will have to bind to a receptor located on the dendrites of the receiving cell, the postsynaptic neuron. You can think of receptors as having a particular shape, and only certain neurotransmitters can fit in the receptors. It is similar to how a key fits in a lock.

Just as a key has to have the right shape to make the lock turn, a neurotransmitter has to have the proper shape to activate the receptor to cause a change. A neurotransmitter's ability to fit into the receptor and stay bound is called affinity, and its ability to activate the receptor is called efficacy.

Additional Materials

View a Pdf Transcript of Release of a Neurotransmitter

View a Pdf Transcript of Neurotransmitters and Their Functions