NERVOUS TISSUE Flashcards
Origin?
Ectodermal
definition
tissues made up of specialized nerve cells which forms the nervous system of animals.
what is the special property of nervous tissue?
1.excitibility
2.conductivity
Do neurons divide once fully formed?
NO
Two main categories of nervous tissue
1.Neurons
2.Neuroglia
Components of nervous tissue
- Neurons
- Neuroglia
3.Ependymal cells
4.Neuro secretory cells
Basic structural and functional unit of nervous tissue.
Neuron
What does a neuron do?
Transmits impulses all over the body after receiving the impulses from outside world.
Dense connective tissue covering a neuron
Epineurium
Structure of neuron
- Soma/Cell body/Perikaryon
- Cytoplasmic extensions
What is a neuron made of?
bundles of axons called fasciculi with each called fascicle covered by perineurium.
Cell body
main body of neuron, with centrally placed nucleus, mitochondria, ER, Ribosomes, Nissl’s granules, lysosomes
-carries genetic info, regulates activities and maintains the structure
Cytoplasmic extensions
- Axon
- Dendrons
Axon
single, long, unbranched(except terminal end), efferent in nature. Usually covered with myelin sheath made up of Schwann cell, broken at certain intervals called nodes of Ranvier. At terminal ends axon forms many branches called axon terminals and telodendrion which swells at the tip to be called synaptic knobs
Function of Schwann cell
produce myelin sheath
Cell membrane of axon
Axolemma
Cytoplasm of axon
axoplasm
Dendron
numerous short branched nerve process, afferent, Nissl’s granules but no myelin sheath
Function of nodes of Ranvier
Allows diffusions of ions
Difference between axons and dendrons.
1.number
2. Nissl granules
3. myelin sheath
4. branching
5. mode
6. length
Types of nerve cell on the basis of myelin sheath
- Myelinated/medullated
-white matter of brain and spinal cord
-fast conduction
-thicker - Non- myelinated/non-medullated
-grey matter of brain and spinal cord
-slow conduction
-thinner
Types of nerve cell on the basis of number of nerve processes
- Unipolar-single axon only
-nervous system of embryo - Bipolar-one of both in opposite poles
-retina of eye and olfactory nerve - Multipolar- Many dendrites and one axon
-adult central nervous system
Types of nerve cells on the basis of function
1.Afferent/Sensory
-towards CNS
-optic nerve
2.Efferent/Motor
-away from CNS
-Oculomotor nerve
3.Mixed
-Spinal nerve
Neuroglia/glial cells
non-neuronal packing cells between nerve cells
-supports, protects and regulates neurons of CNS and PNS
-50% of brain and 10 times more than neuron
Types of neuroglial cells
- Microgliocytes - small, spindle shaped, phagocytic
2.Astrocytes- star shaped, highly branched processes, regulation of organic and inorganic substances from nearby blood capillaries
3.Oligodendrocytes-produces myelin sheath
functions
- packing material
- insulator between neurons
- nutrition
- memory
- phagocytes
Ependymal cells
Simple cuboidal/columnar cells lined in ventricles of brain and central canal of spinal cord , produces CSF, bears microvilli for regulation and absorption of CSF
Neuro-secretory cells
Special secretory cells found in hypothalamus of the brain.
-secretes neuronal hormones that stimulate the pituitary gland
examples of neuro-secretory cells
FSH, TSH, ACTH, PROLACTIN, MSH, GH
Difference between neuron and neuroglial cells
1.function
2.specialization
3.ability to divide
4. number
5.synapse
6.nerve processes
