A 25-year-old lady comes to OPD with chief complaints of weakness and fatigability. Generally, during the morning she does not feel any significant weakness but, as day passes and she get involved in routine household works, weakness gradually starts to increase. The condition improves by some rest or sleep. She also reports double vision and difficulty in swallowing.
Physical examination – Ptosis, diplopia, proximal muscle weakness, normal deep tendon reflex, no sensory impairment.
What is the diagnosis?
Why does rest improve the symptoms?
How to manage the condition?
What is the physiological basis of the management?
Call Girl Coimbatore Prisha☎️ 8250192130 Independent Escort Service Coimbatore
NMP-1.pptx
1. Structure and
functions of neurons
Dr. Sai Sailesh Kumar G
Associate Professor
Department of Physiology
NRIIMS
Email: dr.goothy@gmail.com
2. Case study
A 25-year-old lady comes to OPD with chief complaints of
weakness and fatigability. Generally, during the morning she does
not feel any significant weakness but, as day passes and she get
involved in routine household works, weakness gradually starts to
increase. The condition improves by some rest or sleep. She also
reports double vision and difficulty in swallowing.
3. Case study
Physical examination – Ptosis, diplopia, proximal muscle
weakness, normal deep tendon reflex, no sensory impairment.
What is the diagnosis?
Why does rest improve the symptoms?
How to manage the condition?
What is the physiological basis of the management?
4. Introduction
A neuron is the structural and functional unit of the nervous system
What do u mean by structural and functional unit????
Primary function is to receive the stimuli and transmit it to other neuron
or tissue
Neuron is excitable cell
What do you mean by excitable cell???
7. Cell body
Also called as soma/perikaryon
Contains nucleus and cytoplasm
Nucleus has one nucleolus
Sometimes maybe two nucleoli
Centrioles are absent ( Neuron can not regenerate)
8. Cell body
Cytoplasm has cell organelles like Nissl granules, mitochondria, Golgi
complex, lysosomes and cytoskeletal proteins
Soma contain genetic information
Soma is capable of protein synthesis
Soma at one end gives small branching processes called dendrites
At other end a long process called axon
9. Dendrites
Numerous short extensions from Soma
Increase cell surface area by many folds for receiving information
Receive incoming signals from other cells and transmit to the cell body
At some areas of the brain they cause protein synthesis
10,000 dendrites per neuron approximately
10. Axon
Axon forms the nerve fiber
What is the difference between neurons and nerve fibers???
Long tubular process that extends away from the cell body to transmit
output signals to target organs.
Axons carry impulses away from the cell body
11. Axon
Cytoplasm – Axoplasm
Contains mitochondria, Golgi apparatus, cytoskeletal proteins
Axon raises from area called axon hillock or initial segment
AP is generated in a motor neuron at the axon hillock
AP is generated in a sensory neuron at the first node of the Ranvier
12. Axon
The plasma membrane of axon is called axolemma
The terminal part of axon loses myelin and divides into several
branches – Telodendria
The endings of telodendria form bulb like enlargements called terminal
buttons or synaptic knobs
The synaptic knobs contain the vesicles filled with neuro transmitters
13. Axon
There are two type of axons
Myelinated axons
Unmyelinated axons
Myelin sheath in the peripheral nervous system is formed by Schwann
cells
In CNS, myelination is done by oligodendrocytes
14. Myelinogenesis
The axon remains suspended by a fold of Schwann cell membrane
called mesaxon
Mesaxon greatly elongated and spirally wraps around the axon several
times
Lipids get deposited between the adjacent layers of membrane and
the myelin sheath is formed
15. Myelinogenesis
Outside the myelin sheath, a thin layer of Schwann cell cytoplasm persist
This forms an additional sheath called neurilemma
Sensory fibers of the dorsal column tract first get myelinated in 4th to 5th
months of intra-uterine life
Corticospinal tract starts myelination at 2 months of age and completes
about 2nd year of life
18. Uses of myelin sheath
It increases the speed of conduction
It reduces energy expenditure by the cell
Provides protective covering to axon
Responsible for color of the white matter of brain and spinal cord
19. Multiple sclerosis
Autoimmune disease
Patchy destruction of myelin
Decreased conduction velocity
Effects on both sensory and motor neurons
It affects females twice as much as males
20. Multiple sclerosis
Weakness in lower limbs
Spasticity
Numbness
Urinary incontinence
Blurring of vision
Difficulty in speech and deglutition
21. Multiple sclerosis – Treatment
Use of corticosteroids to reduce inflammation
Administration of drugs
Immuno supression
Preventing the attack of the immune system on the myelin sheath
Depleting B lymphocytes
22. Unmyelinated axons
Do not have a myelin sheath
Nerve impulses travels uniformly along the axolemma
Conduction is slow
Consumes more energy
All post-ganglionic fibers of ANS
23. Transport in the Axon
The axon does not have the ability to synthesize proteins
Hence, the proteins formed in the cell body are transported through the
axon by the axoplasmic flow
Movement from the cell body to axon terminal – orthograde transport
Movement from axon terminal to the cell body – retrograde transport
Growth factors, tetanus toxin, herpes virus, poliovirus – retrograde transport
24. Transport in the Axon
Slow axonal transport – materials move at a rate of 1-5 mm per day
Movement is from axoplasm to axon terminal
Fast axonal transport – materials move at a rate of 200-400 mm per
day
Movement in both directions
25. Trans neuronal transport
Trophic substances like NGF are transported across the synapse to
the presynaptic membrane of another neuron
Helps in maintenance of synaptic contacts
26. Functions of the neurons
The cell body and dendrites serve as receptor zones to receive the
information
Axon hillock/ initial segment is for generation of action potential
Axon for transmission of nerve impulse
Axon terminal for discharge of NT
27. Cell body
It maintains the functional and anatomical integrity of the axon
The proteins associated with synaptic transmitters are synthesized in
Nissil granules of the cell body
Transported to axon terminal by axonal flow
29. Axon
The axon hillock/ initial segment is the site where the action potential
is generated
The long axonal process propagates action potentials from the cell
body to the axon terminal
30. Axon terminal
It contain the neuro transmitters in the vesicles
The arrival of action potentials at membrane of axon terminal results in
the release of NT
31. Factors affecting the growth of neurons
Neurotrophins
Trophic proteins to the neurons
They promote nerve growth and survival
Produced by nerves, muscles, glands and astrocytes
Nerve growth factor, Neurotrophin-3, 4, 5
Brain derived neurotrophic factor (BDNF)
32. Factors affecting the growth of neurons
Nerve growth factors
First neurotrophins to be identified
Promotes growth and survival of sympathetic nerves and some sensory
nerves
Decreases apoptosis of neurons acting through tyrosine kinase A receptors
Made up of 2 alpha, 2 beta and 2 gamma units
33. Types of neurons
According to the arrangement of axons
Unipolar neurons: have single processes.
Found in ANS and cerebellum
Pseudounipolar neurons: axon after originating from soma, splits into
central and peripheral processes
DRG
34.
35. Types of neurons
According to the arrangement of axons
Multipolar neurons: have many processes.
Spinal motor neuron
38. Types of neurons
According to the function
Sensory neurons
Carry impulses from receptors to the CNS
Also called afferent neurons
39. Types of neurons
According to the function
Motor neurons
Carry impulses from CNS to the target organs
Also called efferent neurons
40. Types of neurons
According to the dendritic pattern
Pyramidal cells
These cells spread like pyramids
Hippocampal pyramidal neurons
41.
42. Types of neurons
According to the dendritic pattern
Stellate cells
Radial-shaped spread of dendrites occurs in these cells
Cortical stellate cells
43.
44. Neuroglia
The nervous system contains several types of supporting cells
called neuroglia
Astrocytes
Oligodendrocytes
Microglia
Ependymal cells
45. Lambert –Eaton Syndrome
Autoimmune disease
Antibodies formed against voltage gated calcium channels
Decreased calcium influx
Decreased Ach release
EPP not sufficient to cause AP
Muscle weakness