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Sunday, April 28, 2024

Nervous tissue and nervous system

 Nervous tissue and nervous system 

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Component of nervous tissue:

Neuron and neuroglia  

Parts of a neuron: cell body and process- 1) Dendrite 2) Axon

Classification of neuron:

Classification of neuron
According to the polarity:

1.      unipolar

2.      bipolar

3.      multi-polar

According to function

  1. Sensory neuron: unipolor and bipolor

Motor neuron: multipolor

 Nervous system

Division of nervous system:

•         Structurally / anatomically NS is two types,

1.      Central nervous system: Brain, Spinal cord

2.      Peripheral nervous system: Cranial nerves, Spinal nerves, Autonomic nerves

•         Functionally NS is two types

  1. Somatic nervous system,
  2. Autonomic nervous system,

 

What is the composition of   nervous tissue?

  1. Neuron ( nerve cell )         

       2. Neuroglia

Different parts of neuron: 

             Neuron ( nerve cell )         

             a) Nerve cell body  

             b) Processes  i) Dendrite      ii) Axon

Component of grey and white matter:

 

•         Gray matter: a) nerve cell  bodies

                           b)abundant cell processes

                                 c)glial cells

•         White matter: a) nerve fibres

                             b) glial cells

Location of gray & write matter in the CNS:

•         Brain,

•      outer part or cortex forms by gray matter

•      inner core or medulla forms by white matter

•         Spinal cord,

•      outer part or cortex forms by white matter

•      inner core or medulla forms by gray matter

Classification of neuron
According to the polarity:

1.      unipolar

2.      bipolar

3.      multi-polar

According to function

  1. Sensory neuron
  2. Motor neuron
  3. Inter-nuncial

  Nucleus: a collection of nerve cell bodies in the CNS:

example

Dorsal nucleus of vagus

Nucleus ambiguous,

Nucleus of tractus solitarius

Ganglia: a collection of nerve cell bodies  out side the CNS

             a) sensory ganglia of spinal nerves (posterior root ganglia) and cranial  nerves

             b) autonomic ganglia

Tract: a bundle of nerve fibers (axon) connecting neighboring or distant nuclei of the CNS is a tract

Structure of a peripheral nerve

The nerve trunk is surrounded by a dense connective tissue sheath called the epineurium.

the bundles of nerve fibers are surrounded by a connective tissue sheath, called perineurium

A loose delicate connective tissue covers the individual nerve fiber called endoneurium.

 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

Function of myelination

•         It acts as an insulator

•         Helps in impulse conduction

What is synapse?

•         The synapse is the specialised junctions between two or more adjacent neurons.

What are the types of synapses?
According to the location of synapse in the post synaptic neurons

Q.9. Definition and types of receptors

Receptors : it is a special sensory nerve ending which receives impulse from outside and within the body

Anatomical types of receptors:

Non- Encapsulated: free nerve ending

                                 Merkel’s disc

Encapsulated: Meissner’s corpuscle

                        Pacinian’s corpuscle

                        Ruffini’s corpuscle  

(Functionally five types

  1. Mechanoreceptors:
  2. Thermoreceptors:
  3. Nocireceptors:
  4. Electromagnatic receptors:
  5. Chemoreceptors: )

Q.10. Nervous tissue character:

    1. it is composed of  Neuron  and neuroglial cells
    2. Extracellular matrix is absent

Classification of neuron
According to the polarity:

Myelin sheath of PNS derived from schwann cells

Myelin sheath of CNS derived from oligodendrocytes

Peripheral nerve plexuses

•         Peripheral nerves sometimes divides into branches in their course that join neighboring peripheral nerves form a network of nerves called nerve plexus.

•         Example: brachial plexus, lumbar plexus, sacral plexus etc.

Receptors : it is a special sensory nerve ending which receives impulse from outside and within the body

Functionally five types

  1. Mechanoreceptors:
  2. Thermoreceptors:
  3. Nocireceptors:
  4. Electromagnatic receptors:
  5. Chemoreceptors:

Anatomical types of receptors:

Encapsulated: Pacinian corpuscle

                           Meissner’s corpuscle

                           Non-encapsulated: free nerve ending

Reflex: A reflex may be defined as an involuntary response to a stimulus.

It consists of the following anatomical structures: 1) a receptor organ

2) an afferent neuron

3) an effector neuron

4) an effector organ

 

 Reflex may be divided into 4 groups:

      1) Superficial (or skin and mucous membrane) reflexes

          Corneal reflexes, gag reflexes

      2) Deep (or myotatic) reflexes

           Jaw jerk, knee jerk

      3) Visceral ( or organic) reflexes

          Pupillary reflex

      4) Pathological (or abnormal) reflexes

          Ankle clonus, Babinski’s sign

 


What is gray and whitematter :

Grey matter:

  • Nerve cell  bodies
  •  abundant cell process
  •  Glial cells
  • blood vessels

White matter:

·         Nerve fibres

·         Glial cells

·         blood vessels

Location of grey and white matter:

Inner grey matter and outer white matter: spinal cord

Outer gr 

•         Nucleus: a collection of nerve cell bodies in the CNS: example: nucleus ambiguous ,  nucleus of tractus solitarius  

 

•         Ganglia: a collection of nerve cell bodies  out side the CNS

             a) dorsal root ganglia

             b) celiac ganglia

·         Tract: a bundle of nerve fibers (axon) connecting neighboring or distant nuclei of the CNS is a tract

·         Ascending tract : anterior and lateral spinothalamic tract

·         Descending tract: anterior and lateral corticospinal tract

Q.7. define nerve and discuss structure of peripheral nerve

Nerve: are bundles of nerve fibers surrounded by connective tissue sheaths.

Structure of a peripheral nerve

·         A loose delicate connective tissue covers the individual nerve fiber called endoneurium.

•         the bundles of nerve fibers are surrounded by a connective tissue sheath, called perineurium

•         The nerve trunk is surrounded by a dense connective tissue sheath called the epineurium.

Q. 8. Examples of somatic and autonomic nerves plexuses

•         Somatic nerve plexus: Example: brachial plexus, lumbar plexus, sacral plexus etc.

•         Autonomic nerve plexus: hypogastric nerve plexus

 

Q.9. Definition and types of receptors

Receptors : it is a special sensory nerve ending which receives impulse from outside and within the body

Anatomical types of receptors:

Non- Encapsulated: free nerve ending

                                 Merkel’s disc

Encapsulated: Meissner’s corpuscle

                        Pacinian’s corpuscle

                        Ruffini’s corpuscle  

(Functionally five types

  1. Mechanoreceptors:
  2. Thermoreceptors:
  3. Nocireceptors:
  4. Electromagnatic receptors:
  5. Chemoreceptors: )


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