Neuron And It's Function

Neuron of CNS supported by several varieties of non excitable cells

1. Astrocytes - supporting framework

2. Oligodendrocytes - Formation of myelin sheath

3. Microglia - phagocytosis

4. Ependyma - circulation and absorption of CSF

Name given to the axon or dendrite of a nerve cell

If the stimulus is in subthreshold in magnitude, the nerve fiber doesn't response and no action potentials is produced. If the stimulus is in above the subthreshold the action potentials is developed

The period during which the already excited nerve fiber doesn't response to a second stimulus

ARP- begining of one AP when it's impossible to stimulate the other

RRP - the time after ARP other impulse can be evoked only when the applied stimulus is stronger

The changes occur in the cell body and also in the axon proximal to the injury

- nucleus pushed to periphery ( cellular edema )

- nissl granules become thin, granular, dispered in cytoplasm ( chromatolysis)

- cell body swells ( imbibition of water )

- Golgi apparatus fragments

- neurofibrils disappear

Chemical agent release from the nerve ending that transmit the nerve impulse from the one nerve to the nerve of effector organs

1. Chemical nature ( amine, AA, others )

2. Function ( inhibitory, excitatory, both)

GABA

Dopamine

Serotonin

Glycine

Alanine

Epinephrine

Glutamate

Acetylcholine

Nor epinephrine

Histamine

Prostaglandin

Acetylcholine

Nor epinephrine

Epinephrine

Dopamine

Serotonin

Melatonin

Histamine

GABA

Glycine

Glutamate

Aspartate

ATP

Site of functional contact between neurons and neurons of other effector cell

Structural ( Axosomatic , axodendritic , axoaxonal )

Mode of synaptic transmission ( chemical, electrical)

Depolarisation<AP< impulse is produced in postsynaptic cell

Hyperpolarisation <No AP< No impulse in postsynaptic cell

1.presynaptic nerve terminal

2.exocytosis

3.neurotransmitter diffuse through the synaptic cleft

4. hyperpolarisation

5. Depolarisation

1. Spinal cord level : conduct signal from periphery to the body . Walking movement, control of blood vessels, GI movements

2. Upper Brain level : cerebral cortex. Memory store house . Function associated with lower brain level .

3. Lower brain level : medulla , pons, hypothalamus, thalamus , basal ganglia. It’s control equilibrium, feeding reflex, subconscious control of arterial blood pressure.

1. ACC. Number of processes :

- unipolar: 1 process , invertebrates neuron

- bipolar - 2 process . Retina, cochlear & vestibular ganglia

2. ACC to position : UMN LMN

3.acc. Size of axon : Golgi 1&2

4. ACC. Function : motor - cns to periphery , pyramidal cell , anterior horn cell . Sensory - periphery to cns cranial nerve(1,2,8)

Excitability

Conductivity

All or non Law

Refractory period

Adaptation

Summation

One way conduction

Fatigue

Synaptic delay

Synaptic response inhibition

Facilitation

summation

Occulation

Excitability

Specificity

Adaptation

Law of projection

Law of specific nerve ending

Intensity discrimination

Summation synaptic delay subliminal fringe fatigue facilitation fractionation

Inhibition irradiation recruitment reciprocal innervation occlusion habituation

Nerve cell respond to electrical, chemical, mechanical stimuli but response is always electrical

2 or more sub threshold stimulus applied at the same time

Propagation of action potential from one site of generation to another

Continuous conduction in unmyelinated nerve fiber. Along the axolemma

Discontinuous In myelinated stimulated only at the nodes of Ranveer . AP jumps from one node to another.

The diameter of mammalian peripheral nerve fibre is 6 .

- conducting velocity is direct proportional to diameter of nerve fibre

Protein necessary for growth and survival of neuron

- Astrocyte , muscle

- NT3, NT -4/5 , FGF, NGF

- receptor bind with nerve terminal and initate phosphorylation of tyrosine kinases

- repair nerve cell, facilitate neural development, growth, important role in maintaining nerve tissue and its transmission

The process of changes occurring in the axon distal to the injury .

- Axon swells and breaks into segments (debris) phagocytes by microglial cells

- myelin sheath break down into lipid droplets

- Schwann cell begin to proliferate and form a parallel cord

- if regeneration doesn’t happen Schwann cell and axon replaced by fibrous tissue

In the cns if one group of neuron is injured and the other group serving the same function may also show degenerative changes.

In the cns if one group of neuron is injured and the other group serving the same function may also show degenerative changes.

Destructive changes occurring in the nerve fibre or nerve cell body .

1. Wallerian ( axon distal to injury)

2. Retrograde ( cell body and segment of axon proximal to injury)

3. Transneural

- blockage of blood vessels

-crushing and transaction of nerve fibre

Chemical messenger, which modifies and regulate activities that take place during synaptic transmission.

It’s a time interval between the arrival of impulse at presynaptic terminal and on set of response in post synaptic terminal.

It’s a time interval between the arrival of impulse at presynaptic terminal and on set of response in post synaptic terminal.

When synapse is rapidly and repetitively stimulated, the number of discharge by the postsynaptic neurons decreases

At synapse impulse are received, integrated , discharged.

-The positive increase in the voltage above the resting neural potential , to less negative value

- during this potential the excitability of other neuron to stimuli increased

- RMP -65mv to -45mv

- EPSP +20 mv

Negative increase in voltage below the resting neural potential, the more negative value is called IPSP

Because of this potential the excitability of neuron to other stimuli decreased.

-65 mv to -70 mv

IPSP + 5 mv