the nervous system. definition -- it is an organ system containing a network of specialized cells...
TRANSCRIPT
The nervous system
The nervous system
Definition
--It is an organ system containing a network of
specialized cells called neurons that coordinate the actions of an
animal and transmit signals between different parts of its
body
nervous system
Structural Classification of the Nervous System
-- In most animals the nervous system consists of two parts, central and peripheral .
--The central nervous system of vertebrates (such as humans) contains the brain and
spinal cord . --The peripheral nervous system consists of
sensory neurons, clusters of neurons called ganglia, and nerves connecting them to each
other and to the central nervous system .
Functions of the Nervous System
1 .Sensory input – gathering information
To monitor changes occurring inside and outside the body (changes = stimuli)
2 .Integration
to process and interpret sensory input and decide if action is needed.
3 .Motor output
A response to integrated stimuli
The response activates muscles or glands
Nervous Tissue: Type of cellsThe nervous system contains two main categories or types of cells:
neurons and glial cells.
1 .Neurons --Cells specialized to transmit messages (electrically excitable cell
that transmits information by electrical and chemical signaling).
--A typical neuron possesses a cell body (often called the soma), dendrites, and an axon .
Dendrites and axon are thin structures that arise from the cell body, often extending for hundreds of micrometers and branching
multiple times, giving rise to a complex "dendritic tree ."
--The cell body of a neuron frequently gives rise to multiple dendrites, but never to more than one axon, although the axon
may branch hundreds of times before it terminates .
Neuron Anatomy
Cell body
Nucleus
Dendrites
Axon
--Dendrites conduct impulses toward the cell body, while axons conduct impulses away from the cell body.
Functional Classification of Neurons
(A )Sensory (afferent) neuronsCarry impulses from the sensory receptors
(B )Motor (efferent) neurons
Carry impulses from the central nervous system
(C )Interneurons (association or relay neurons)
Found in neural pathways in the central nervous system as they connect sensory and motor neurons.
3 main types of nerve cells
sensory neurone
relay neurone
motor neurone
Sensory neurons
Carries impulses from receptors e.g pain receptors in skin to the CNS( brain or spinal
cord)
Relay neuron
Carries impulses from sensory nerves to motor nerves.
Motor neuron
Carries impulses from CNS to effector e.g. muscle to bring about movement or gland to bring about secretion of hormone e.g
ADH
2 .Glial cells --They are non-neuronal cells that provide support and nutrition, maintain
homeostasis, form myelin, and participate in signal transmission in the nervous system.
--A very important type of glial cell (oligodendrocytes that produce myelin sheath around nerve fibers in the central nervous system, and Schwann cells in the peripheral nervous system) generates layers of a fatty substance called myelin that wraps around axons and provides electrical insulation which allows them to transmit action potentials much more rapidly and efficiently.
Neuroglia vs. Neurons
Neuroglia divide.Neurons do not.
Most brain tumors are “gliomas”.
Most brain tumors involve the neuroglia cells, not the neurons.
Consider the role of cell division in cancer!