Axons are long nerve processes which carry nerve impulses from the Soma to other neurons, they vary in length but can become almost as long as half of the human body.
The soma (body) of the neuron contains the nucleus which acts as the cell's control centre, these contain many small neurofibrils which project from the nucleus into the dendrites.
Dendrites are short, thick processes which branch out of the soma in a tree like manor. They conduct nerve impulses to the soma.
The three categories of neurons:
Afferent (Sensory) Neurons have the dendrites connected to receptors such as the eyes, ears etc. These receptors change the information they receive into electrical impulses that are transmitted to other neurons. In sensory neurons the axons are connected to other neurons.
Efferent (Motor) Neurons have the dendrites connected to other neurons, the axons are connected to effectors. Effectors are either glands or a muscle cell that is the receiving end of the nerve impulse. The nerve, when excited will cause the effector to react (move, contract, or secrete etc).
Internuncial Neurons have both the dendrites and the axons are connected to other neurons. They are sometimes referred to as connector neurons.
Internuncial neurons are found throughout the body, but especially in the spinal cord and brain.
Properties and characteristics of Neurons:
Normally the electrical impulses (messages) travel through a neuron in only one direction.
The axon may be surrounded by a 'coat' of lipids (fats) and proteins known as the myelin sheath which acts as an insulator.
Neurons are specialist cells that have lost the ability to reproduce themselves. Once the soma of a neuron has died the entire neuron dies, and can never be replaced.
Repair of damaged neurons only occurs in myelinated neurons.
white matter are coloured by myelin, consisting of many neurons supported by neuroglia.
grey matter is soma and dendrites or bundles of unmyelinated axons and neuralgia.
Two cells which are in direct contact can send signal to each other across gap junction. For cells which are not in direct contact, there is a number of ways through which these cells communicate, these basically include: paracrine signalling and endocrine signalling. In paracrine signalling, a cell secrete a chemical substance which have effect on a nearby cell while in endocrine signalling, hormones are released into the circulatory system, which convey them to the target cells.
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A. dissociative identity disorder
<span>Physical activity lowers the risk of depression and cognitive decline in adults.
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It seems like a dream about your teeth falling out of your mouth would be bad news. ... The dream can represent everything from a major life change to lack of self esteem; from the fear of getting older to money issues; from symbolizing rebirth to regretting something you've said.
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