Chapter 3- Biological Foundations of Behaviour September 21st

Chapter 3- Biological Foundations of Behaviour September 21st

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September 21 st , 2011 Chapter 3- Page 70-75 Biological Foundations of Behaviour THE NEURAL BASES OF BEHAVIOUR Neurons Neurons ( specialized cells) are the basic building blocks of the nervous system The nerve cells are linked together in circuits Each neuron has three main parts (1) a cell body (2) dendrites and (3) an axon 1. The Cell Body (soma) Contains the biochemical structures needed to keep the neuron alive Its nucleus carries the genetic information that determines how the cell develops and function 2. Dendrites (branchlike fibres emerging from the cell body) These specialized receiving units are like antennas that collect messages from neighbouring neurons and send them on to the cell body It is there that the incoming information is combined and processed 3. Axon (extends from one side of the cell body) Conducts electrical impulses away from the cell body to other neurons, muscles or glands Each may connect with dendritic branches from numerous neurons Axon branches out at its end to form a number of axon terminals - Neurons vary greatly in shape and size - Regardless of their shape or size, neurons have been sculpted to perform their function of receiving, processing and sending messages - Neurons are supported in their functions by glial cells - Glial cells surround neurons and hold them in place - They also manufacture nutrient chemicals that neurons need and absorb toxic materials that might damage neurons - During prenatal brain development, glial cells sent out long fibres to guide newly divided neurons to their targeted place in the brain - It is the job of the glial cell to protect the brain from toxins Blood-brain barrier prevents many substances, including a wide range of toxins from entering the brain Walls of the blood vessels within the brain are smaller than everywhere else in the body and are covered by a specialized type of glial cell Recent research has also detected that glial cells play a role in modulating the communication among neurons. The Electrical Activity of Neurons Neurons do two important things (1) they generate electricity that creates nerve impulses (2) they release chemicals that allow them to communicate with other neurons and with muscles and glands Nerve activation involves three basic steps At rest, the neuron has an electrical resting potential due to the distribution of positively and negatively charged chemicals (ions) inside and outside the neuron When stimulated, a flow of ions in and out through the cell membrane reverses the electrical charge of the resting potential, producing an action potential or nerve impulse The original distribution of ions is restored, and the neuron is again at rest
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Neurons are surrounded by body fluids and separated from this liquid environment by a protective membrane This cell membrane allows certain substances to pass through ion channels into the cell while limiting passage to others
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