CHAPTER 9Nervous Tissue

NERVOUS TISSUE Nervous tissue is found in the brain, spinal

cord, and nerves. It is responsible for coordinating and

controlling many body activities. It stimulates muscle contraction, creates

an awareness of the environment, and plays a major role in emotions, memory, and reasoning.

To do all these things, cells in nervous tissue need to be able to communicate with each other by way of electrical nerve impulses.

NERVOUS TISSUE Nervous tissue is responsible for

sensing "stimuli" and transmitting "signals" to and from different parts of the body.

Neurons are the basic unit of nervous tissue.

A NEURON CONSISTS OF TWO MAJOR PARTS: 1. Cell Body - contains the neuron's nucleus

and associated cytoplasm/organelles. Also known as soma, cyton or perikaryon

2. Nerve Processes - are "finger-like" projections from the cell body that are able to conduct and transmit signals.

There are two types: 1. Axons: typically carry signals away from the cell body. 2. Dendrites: typically carry signals toward the cell body.

NEUROGLIA

Supporting tissue intermingled with the essential elements of nervous tissue especially in the brain, spinal cord, and ganglia.

Functions include providing support for the brain, assisting in nervous system repair

and maintenance, assisting in the development of the

nervous system and providing metabolic functions for

neurons.

THERE ARE SEVERAL TYPES OF GLIA PRESENT IN THE NERVOUS SYSTEM OF HUMANS: Astrocytes are found in the brain's capillaries and

form the blood-brain barrier that restricts what substances can enter the brain.

Microglia are extremely small cells of the central nervous system that remove cellular waste and protect against microorganisms.

Oligodendrocytes are central nervous system structures that wrap some neuronal axons to form an insulating coat known as the myelin sheath.

Schwann Cells are peripheral nervous system structures that wrap some neuronal axons to form an insulating coat known as the myelin sheath.

CLASSIFICATION OF NEURONS ACCORDING TO THEIR STRUCTURE, 1. Unipolar Neurons. have only a

single process or fibre which divides close to the cell body into two main branches (axon and dendrite). Because of their structure they are often referred to as unipolar neurons.

2. Multipolar Neurons, which have numerous cell processes (an axon and many dendrites) are often referred to as multipolar neurons.

3. Bipolar Neurons. are spindle-shaped, with a dendrite at one end and an axon at the other . An example can be found in the light-sensitive retina of the eye.

THERE ARE THREE MAIN TYPES OF NEURONS, CLASSIFIED ACCORDING THEIR FUNCTION

Sensory Neurons move from the receptor to the Central Nervous System. Afferent neuron.

Motor Neurons move from the Central Nervous System to the effector muscle.

Interneurons (also known as connector neurons or association neurons) are those that connect sensory neurons to motor neurons.

End of Presentation

EXAM, EXAM, EXAM