Download - Nervous system easy introduction
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• General anatomy of nervous system
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Nervous system
• Nervous system integrates these sensory information, store information as memory
Nervous system receives sensory information •From external environment (temperature, vision, sound etc.) •From body (touch, pressure, pain etc.)
Nervous system makes an appropriate response, ex: movement of muscles
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Simple flowchart of nervous system function
Skin > touch > nerve (sensory nerve/afferent
fibre/ascending tract) Brain nerve(motor nerve/efferent
fibres/descending tract) muscle> movement
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CNS : PRINCIPLES ROLES
• Integrate and coordinate incoming and outgoing neural signals
• Carry out higher mental functions such as thinking and learning
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Division of nervous system
• Structurally,• Central nervous
system
Brain Spinal cord
• Peripheral nervous system
Cranial nerves,
Spinal nerves, Autonomic nerves
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Functional divisionSomatic nervous system, is the part of nervous system which control voluntary activities
Autonomic nervous system,
is the part of nervous system concerned with the innervation of involuntary structures, such as the heart, smooth muscle, and glands within the body
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What is the composition of nervous tissue?
1. Neuron ( nerve cell ) 2. Neuroglia
Nerve cell body Processes Dendrite Axon
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Nerve cell body
Nerve cell processesDendrite Axon
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Histological feature of neuronnerve cell body
A centrally placed spherical, unusually large , euchromatic (pale-staining) nucleus with a prominent nucleolus,
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Nissl body unique feature of neuron
Nissl bodies are basophilic granular areas formed by the rER , iron & free ribosomes.
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Golgi complex arranged around the periphery of the nucleus.
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Mitochondria are found through out of the cell body,
dendrites, and axons. They are spherical or rod shaped.
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Axon hillock :
it is the area of cell body which is free of large cytoplasmic organelles. It is a landmark to distinguish between axons and dendrites in both light & TEM microscopes.
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• Dendrites are receptor processes that receive stimuli from other neurons or from the external environment
• Axon are effector processes that transmit stimuli to other neurons or effector cells
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What is gray matter and white matter?
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Grey matter Nerve cell body Neuroglia Blood vessel White matter Nerve processes Neuroglia Blood vessels
Neuroglia Blood vessels
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• Gray matter: Neuron cell bodies Neuroglial cells Blood vessels • White matter: Processes of neuron Neuroglial cells Blood vessels
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Location of gray & white matter in the CNS
• Cerebrum and cerebellum ,
• Outer gray matter
• Inner white matter
• Spinal cord,• outer part
white matter• Inner gray
matter
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Gray matter matter
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Classification of neuronAccording to the polarity
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According to function
Sensory neuron
Motor neuron
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Neuroglia
• The neuron of the central nervous system are supported by several varieties of non excitable cells, which together are called neuroglia.
• They are smaller than the neuron • Number of them 5-10 times greater than the
neuron
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There are four types of neuroglial cells in CNS & two types in PNS:
CNS1. Astrocytes (a) fibrous (b) protoplasmic 2. Oligodendrocytes3. Microglia4. Ependyma
• PNS1. Schwann cells2. Satellite cells.
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Protoplasmic Astrocytes Fibrous Astrocytes
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Oligodendrocytes Microglia
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Ependyma
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Schwann cells:
It have the same function as oligodendrocytes but are located around axons in the peripheral NS.
Axon
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Functions of neuroglia Name of the neuroglia Functions
Astrocytes Formation of blood brain barrier
Oligodendrocyte Myelination of nerve fibers in the CNS
Ependymal cells secrete, circulate and absorbed CSF
Microglia Phagocytic function in inflamed brain (They are inactive in normal brain)
Schwann cells Myelination of nerve fibers in the PNS
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Development of neuroglia
Name of the neuroglia
Functions
Astrocytes Neuroectoderm
Oligodendrocyte Neuroectoderm
Ependymal cells NeuroectodermMicroglia Mesodermal in origin
Schwann cells Neural crest
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What is myelin sheath?
• Axon of neuron is covered by
sheaths which are modified cell
membranes of schwann cells in
PNS and oligodendrocytes in
CNS
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Schwann cells
Axon
Schwann cells undergo spiraling around the axon
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Myelination in the CNS by oligodendrocyte
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Function of myelination
• It acts as an insulator• Helps in impulse conduction
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Ganglia a collection of nerve cell bodies out
side the CNS
1. sensory ganglia of spinal nerves (posterior root ganglia) and cranial nerves
2. autonomic ganglia
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Nucleus: a collection of nerve cell bodies of neuron in the CNS is called nucleus
Example: Dorsal nucleus of vagus nucleus ambiguous, nucleus of tractus solitarius
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Grey matter
White matter
Nucleus
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What is synapse?
• The synapse is the specialised junctions between two or more adjacent neurons.
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How impulse go from one neuron to another ?
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What are the types of synapses?According to the location of synapse in the post
synaptic neurons
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• How nervous system is worked ?
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Simple reflex arc
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Reflex arc
• A reflex may be define as an involuntary response to a stimulus. It depends on the integrity of the reflex arc .
A reflex arc consists of the following anatomical structures:
Location
1) a receptor organ Skin, muscle, or tendon
2) an afferent neuron Posterior root ganglion
3) an effector neuron Example: Lower motor neuron located in the ventral horn of spinal cord
4) an effector organ Example: Skeletal muscle
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Structural organization of reflex may be two types
•Monosynaptic reflex
Incoming axons of the unipolar primary sensory neurons synapse directly on a motor neuron.Example: tendon jerks
•Polysynaptic reflex
In these reflex one or more interneurons, excitatory or inhibitory, intervene between sensory and motor neurons.
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Polysynaptic reflex
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Types of reflex • Reflex may be divided into 4 groups:1) superficial (or skin and mucous membrane) reflexes
Corneal reflexes, gag reflexes2) deep (or myotatic) reflexes Jaw jerk, knee jerk3) visceral ( or organic) reflexes Pupillary reflex4) pathological (or abnormal) reflexes Ankle clonus, Babinski’s sign