Man and his environment - National University Tissue .pdf · Copyright © 2004 Pearson Education,...
Transcript of Man and his environment - National University Tissue .pdf · Copyright © 2004 Pearson Education,...
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Dr. Elriah M. Makie 0122858517
Man and his environment
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Nervous Tissue
BSc.M.Sc .MBBS
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Introduction The nervous system is divided into two main parts:
The central nervous system (CNS) comprising the brain and spinal cord.
The peripheral nervous system (PNS) comprising the nerves which run between the CNS and other tissues, together with nerve 'relay stations' termed ganglia
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Introduction The nervous system is designed to deliver rapid and
precise communication between different parts of the body by the action of specialised nerve cells called neurones.
These highly specialised cells are interconnected and function togather and process information and then generate appropriate response signals.
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Introduction Functionally, the nervous system is divided into the
somatic nervous system which is involved in voluntary functions and the autonomic nervous system which exerts control over many involuntary functions.
Histologically, the entire nervous system merely consists of variations in the arrangement of neurones and their supporting tissues.
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Histology of neural tissue
Two types of neural cells in the nervous system:
Neurons - For processing, transfer, and storage of
information
Neuroglia – For support, regulation & protection of
neurons
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Neuroglia (glial cells)
CNS neuroglia:
• astrocytes
• oligodendrocytes
• microglia
• ependymal cells
PNS neuroglia:
• Schwann cells (neurolemmocytes)
• satellite cells
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Classification of neurons
Structural classification based on number of processes:
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Multipolar neuron
• multiple dendrites & single
axon
• most common type
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Bipolar neuron
• two processes coming off cell
body – one dendrite & one axon
• only found in eye, ear & nose
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Unipolar (pseudounipolar)
neuron
• single process coming off
cell body, giving rise to
dendrites (at one end) &
axon (making up rest of
process)
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Classification of neuronsFunctional classification based on type of information & direction of
information transmission:
• Sensory (afferent) neurons –
• transmit sensory information from receptors of PNS towards the
CNS
• most sensory neurons are unipolar, a few are bipolar
• Motor (efferent) neurons –
• transmit motor information from the CNS to effectors
(muscles/glands/adipose tissue) in the periphery of the body
• all are multipolar
• Association (interneurons) –
• transmit information between neurons within the CNS; analyze
inputs, coordinate outputs
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Anatomical organization of neurons
Neurons of the nervous system tend to group together into organized
bundles
The axons of neurons are bundled together to form nerves in the
PNS & tracts/pathways in the CNS. Most axons are myelinated so
these structures will be part of “white matter”
The cell bodies of neurons are clustered together into ganglia in the
PNS & nuclei/centers in the CNS. These are unmyelinated
structures and will be part of “gray matter”
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Anatomical structure of Nerves
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Myelin Sheath is formed by 2 types of Glia The myelin sheath is the wrapping seen
around the axons of some neurons.
Oligodendrocytes – form myelin sheaths on axons in the CNS
Schwann cells – form myelin sheaths on axons in the PNS
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• Gaps between myelin sheath cells are the Nodes of Ranvier.
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Thanks