NERVOUS SYSTEM
CONTROLLING AND COORDINATING SYSTEM OF THE BODY
Cantains:
exitable cells - Neurons
Non- excitable cells - Neuroglial cells
Classification:
Structurally :central nervous system
Peripheral nervous system
Functionally :
Somatic nervous system
Autonomic nervous system
CNS : Brain ,spinal cord
PNS : 31 spinal nerve ,12 pairs of cranial nerves , associated ganglia.
STRUCTURE OF NEURON:
DENTRITE
- conduct impulses towards the cell body
- Usually multiple in number .
AXON(axis cylinder)
- Conduct impluses away from the body
- Only 'ONE' axon is present in a neuron
BASIC TYPES OF NEURONE:
- Pseudo unipolar neuron's :
- only one process.
- After arising from the cell body ,it immediately divides into 2 process.
- Ex: sensory nerve
2. Bipolar neuron's :
- Two processes , one axon and extra is dendron
- Ex: nose ,retina
3. Multipolar neuron's:
- One axon and multiple dendrites .
- All motor neuron's are multipolar.
- Motor Neuron's:
- Efferent neuron's and multipolar .
- Carry impulses from CNS to effector structures.
- Sensory neuron's:
- Afferent neuron's and pseudo unipolar .
- Carry implulses from sensory receptors to CNS.
Neuroglial cells
- Astrocytes
- Present at the site of blood brain barrier
- They are the glycogen stress, in the central nervous system.
- Oligodendrocyte
- From myelin sheet around the axon in CNS.
- Microglial
- Are phagocytic in function
- Found around blood vessel.
- Ependymal cells
- Lining the cavity in brain and spinal cord
- Schwann cell
- Provide myelin sheat for PNS
PERIPHERAL NERVE
- Nerves are composed of bundles of nerve fibres.
- Each nerve fibre is an axon with its covering
- Each nerve fibres is covered by endoneurium
- Bundles of nerve fibre is covered by perineurium.
- Whole nerve is covered by epineurium.
SPINAL NERVES
- Cervical : 8
- thoracic : 12
- Lumbar : 5
- Sacral : 5
- Coccygeal : 1
Typical spinal nerve
- Arises from the spinal cord as a rootlets.
- Anterior root consisting of motor (efferent) fibres from the cell body in the anterior horn of spinal cords.
- Anterior and posterior joining together to form mixed spinal nerve, and it emerges to inter vertebral foramen.
- Divides into ventral and dorsal rami
- Dorsal rami: supplies skin and muscles of the back.
- Ventral rami : supplies the skin and muscles of limbs of anterior part of the body.
MYELINATION AND ITS SIGNIFICANCE:
- Myelination is a process in which a neuroglial cell surrounds a portion of the axon or dendrite to support the facilitated conduction of impulses.
- In central nervous system (CNS) oligodendrocyte is responsible for the myelination
- In peripheral nervous system ( PNS) Schwann cells are responsible for the myelination.
- Dermatome:
- Area of skin supplies by one segment of spinal cord
- Myotome :
- Amount of muscle supplied by segment of spinal cord.
CRANIAL NERVE's
- Nerves which arises from brain stem
- Olfactory
- Optic
- Oculomotor
- Trochlear
- Trigeminal
- Abducent
- Facial
- Vestibulo cochlea
- Glossopharyngeal
- Vagus
- Accessory
- Hypoglossal
Nerves attached to spinal cord
- 31 pairs of spinal nerves
- Ventral root
- Dorsal root
Internal features
- Grey matter - 'H' shaped / butterfly shaped
- Ventral horn
- Dorsal horn
- Intermediate region
- Central canal
- Grey commissure
- Lateral horn - thoracic.
- White matter
- Nerve fibre : mostly myelinated .
- Made of trads : ascending / descending.
- Anterior of funiculus.
- Lateral funiculus
- Posterior funiculus
AUTONOMIC DIFFERENCE
Sympathetic division | Parasympathetic division | |
Pupil dilate | EYES | Pupil contract |
Decrease | SALVATION | Increase |
Accelerates | HEART | Slow |
Inhibits | DIGESTION | Activates |
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