All Basics about Classification of nervous system

1. Dr. VINAY PATIDAR
Assist. Professor
R.N. Kapoor Memorial Homoeopathic Hospital &
Medical College, INDORE
TOPIC
“ CLASSIFICATION OF NERVOUS SYSTEM”

2. CONTENT
 FORMATION OF A NERVE
CLASSIFICATION OF NERVOUS SYSTEM ARE FOLLOWING:
 STRUCTURAL CLASSIFICATION:
 BASED ON POLARITY
 FUNCTIONAL CLASSIFICATION:
 BASED ON CONDUCTION DIRECTION
 BASED ON NEUROTRANSMITTER PRODUCTION
 BASED ON UNIQUE SHAPE AND FUNCTION

3. FORMATION OF A NERVE
 Neurons: Collectively form a nerve.
 Fascicles: A nerve is usually made up from a variety of
fascicles.
 Perineurium & endoneurial fluid: Each fascicle is encased by
perineurium. Inside the fascicle are a Group of axons bathed
in endoneurial fluid.
 Interfascicular epineurium: Between the fascicles is a fatty
material called the interfascicular epineurium. The nerve is
then wrapped in the main epineurium.

4. STRUCTURAL CLASSIFICATION
 BASED ON POLARITY :
Unipolar :
 type of neuron in which only one protoplasmic process (neurite)
extends from the cell body.
 Found mostly in invertebrate
 In humans mostly found in dorsal root ganglia
Pseudo unipolar :
 contains an axon that has split into two branches; one branch runs
to the periphery and the other to the spinal cord.

5. STRUCTURAL CLASSIFICATION (Cont.)
Bipolar:
 An axon and a single dendrite on opposite ends of the soma are specialized sensory neurons
for the transmission of special senses, hence abundant in sensory pathways for smell, sight,
taste, hearing and vestibular functions.
Multipolar:
 An Axon along with more than two dendrites.
 Multipolar neurons constitute the majority of neurons in the brain.
 Subdivided in to golgi-I and golgi-II types.
 Includes motor neurons and interneurons.

6. FUNCTIONAL CLASSIFICATION
 BASED ON CONDUCTION DIRECTION :
 Afferent neurons :
 Also called sensory neurons.
 Convey information from tissues and organs into the
central nervous system.
Efferent neurons :
 Also called as motor neurons.
 Carry nerve impulses away from the central nervous
system to effectors such as muscles or glands.

7. FUNCTIONAL CLASSIFICATION (Cont.)
 According to their targets, motor neurons are classified into three broad categories:
Somatic motor neurons, Special visceral motor neurons, General visceral motor neurons.
 Somatic motor neurons are further divided in to:
 α motor neuron (innervating extrafusal muscle fiber) and
 γ motor neuron (innervating intrafusal muscle fiber)
Interneuron :
also called as relay neuron or local circuit neuron.
connects afferent neurons and efferent neurons in neural
pathways.

8. FUNCTIONAL CLASSIFICATION (Cont.)
 BASED ON NEUROTRANSMITTER PRODUCTION :
 Cholinergic neurons :
 Secreting acetylcholine.
 GABAergic neurons :
 secreting gamma amino butyric acid.
 Glutamatergic neuron :
 secreting glutamate.
 Dopaminergic neurons :
 secreting dopamine. Loss of dopamine neurons in the substantia nigra has been linked
to Parkinson's disease.
 Serotonergic neurons :
 secreting serotonin. Lack of serotonin at postsynaptic neurons has been linked to
depression.

9. FUNCTIONAL CLASSIFICATION (Cont.)
 BASED ON UNIQUE SHAPE AND FUNCTION:
 Betz cells:
 large motor neurons located within the fifth layer of the grey matter in the primary motor
cortex.
Purkinje cells :
 some of the largest neurons in the human brain, found within the Purkinje layer in the
cerebellum.
Renshaw cells :
 Neurons with both ends linked to alpha motor neurons. Target of the toxin of Clostridium tetani

10. FUNCTIONAL CLASSIFICATION (Cont.)
 BASED ON UNIQUE SHAPE AND FUNCTION (Cont.):
 Pyramidal neurons (pyramidal cells) :
 Type of neurons with triangular soma found in areas of the brain including cerebral cortex, the
hippocampus, and in the amygdala.
 Basket cells :
 Inhibitory GABAergic interneurons found in several brain regions: the molecular layer of the
cerebellum, the hippocampus, and the cortex.