The document provides an overview of the nervous system, detailing its structure, components, and classifications into the central (CNS) and peripheral nervous systems (PNS). It explains the roles of neurons, including their characteristics and types such as afferent and efferent neurons, and describes the synaptic transmission of nerve impulses via neurotransmitters. Additionally, it outlines the structural components of neurons, including the cell body, dendrites, and axons, and the significance of myelin sheaths.

1. ANATOMY AND PHYSIOLOGY 2
BTPOTC

2. THE NERVOUS SYSTEM
PREPARED BY REBECCA DORDUNU

3. INTRODUCTION
• The nervous system is a complex network of
nerves and cells that carry messages to and
from the brain and spinal cord to various
parts of the body.
• Organization of nervous tissue within the
body enables rapid communication
between different parts of the body.

4. THE NERVOUS SYSYTEM

5. The Nervous System
The nervous system consists of :
Brain
The Spinal Cord
Nerves.

7. CLASSIFICATION OF THE NERVOUS SYSTEM
• The nervous system can be grouped
into:
The Central Nervous System (CNS)
Peripheral Nervous System (PNS)

9. THE CENTRAL NERVOUS SYSTEM
(CNS)
• The Central Nervous System is made
up of:
The brain
Spinal cord

10. THE PERIPHERAL NERVOUS SYSTEM
• The peripheral nervous system (PNS)
consisting of all the nerves outside
the brain and spinal cord
• It is made up of:
The Somatic
The Autonomic nervous systems.

11. THE PERIPHERAL NERVOUS SYSTEM cont.
• The autonomic nervous system has
two parts:
Sympathetic
Parasympathetic

12. NERVOUS
SYSTEM
PERIPHERAL
NERVOUS
SYSTEM
AUTONOMIC
NERVOUS
SYSTEM
SYMPATHETIC
NERVOUS SYSTEM
PARASYMPATHETIC
NERVOUS SYSTEM
SOMATIC
NERVOUS
SYSTEM
CENTRAL
NERVOUS
SYSTEM
BRAIN
SPINAL
CORD

13. THE NEURON

14. THE NEURON cont.
• The nervous system consists of a vast
number of cells called neurones which
are responsible for conductivity.
• These neurones are supported by a
special type of connective tissue called
the neuroglia.

15. THE NEURON cont.
• The function of the neuroglia cells:
They support the neuron
They protect the neuron
They prevent harmful substances
from entering the nerve cell.
They have phagocytic properties

16. THE NEURON cont.
• Neurones are commonly referred to
simply as nerve cells.
• Bundles of axons bound together are
called nerves.
• Nerve cells vary considerably in size
and shape but they are all too small
to be seen by the naked eye.

17. Characteristic of a nerve cell
• Neurones have the characteristics of:
irritability
conductivity

18. Characteristic of a nerve cell cont.
1. Irritability is the ability to initiate nerve impulses
in response to stimuli from:
outside the body, e.g. touch, light waves
inside the body, e.g. a change in the
concentration of carbon dioxide in the blood
alters respiration; a thought may result in
voluntary movement
2. Conductivity means the ability to transmit an
impulse

19. Functional characteristics of the nerve cell
• Afferent/ sensory neurons: they transmit
impulses from the periphery to the central
nervous system (CNS)
• Efferent/ Motor neurons: these transmit
impulses away from the CNS to some
effector organs, usually skeletal
muscle ,visceral muscle or gland.
• Connector neurons: they transmit impulses
from one part of the CNS to the other.

20. Types of efferent neuron
• Motor neuron: they transmit impulses that
leads to contraction of skeletal muscles.
• Secretory neuron: they transmit impulses that
lead to secretion of gland. It causes the gland
to secrete their content.
• Accelerator and inhibitory neurons: they
supply smooth muscle and cardiac muscle
with impulse that speeds or slows activity
respectively.

21. Types of Afferent/Sensory Neurones
• Generalized (touch, pain temp,
movement)
• Specialized (vision, hearing)
• Visceral: internal

22. Mixed nerves
• In the spinal cord, sensory and motor
nerves are arranged in separate groups, or
tracts.
• Outside the spinal cord, when sensory and
motor nerves are enclosed within the same
sheath of connective tissue they are called
mixed nerves

23. THE NEURON cont.
• Each neuron consists of a three major parts.
Cell body
One axon
Many dendrites

24. The cell body
– The cell body also called the soma, is the spherical part of the
neuron that contains the nucleus and is also the site for
general cell function.
– The cell body forms the grey matter of the nervous system.
– They are found at the periphery of the brain and in the centre
of the spinal cord.
– Groups of cell bodies are called nuclei in the central nervous
system and ganglia in the peripheral nervous system

25. Cell body

26. Dendrites
• The dendrites are the many short processes that
receive and carry incoming impulses towards cell
bodies.
• They have the same structure as axons but they are
usually shorter and branching.
• In motor neurons they form part of synapses and in
sensory neurons they form the sensory receptors
that respond to stimuli.

28. Axons
• They conduct impulses away from the body.
• Each neuron has only one axon
• Axons are found deep in the brain and the periphery
of the spinal cord. They are in groups, called tracts.
• They are referred to as nerves or nerve fibres outside
the brain and spinal cord

30. Axons
Axons and dendrites are extensions of cell bodies
and they form the white matter of the nervous
system

31. Structure of an axon
The membrane of the axon is called axolemma and it
encloses the cytoplasmic extension of the cell body.
Large axons and those of peripheral nerves are
surrounded by a myelin sheath
This consists of a series of Schwann cells arranged
along the length of the axon

32. Myelin sheath
• They are white lipid protein complexes that surrounds
many nerve fiber.
• They are arranged in segments along the fiber and the
interval between the various segments are called Nodes
of Ranvier.
• They are mostly continues and it covers the axon

33. Myelinated fibers
• They are those with myelin sheath completely
surrounded and form the white matter of the
brain and the spinal cord.

34. Non- Myelinated fibers
• They are those without the myelin sheath and
together with the cell bodies form the grey matter of
the brain.

35. The neurolemma sheath
• This is a very delicate membrane, formed by the
schwann cells and is found enveloping all the
peripheral nerves.
• It is absent in the central nervous system.
• It surrounds the myelin sheath of myelinated fibers
and the naked cylinders of the non-myelinaled fibers

37. The synapse
• There is always more than one neuron involved in
the transmission of a nerve impulse from its origin to
its destination, whether it is sensory or motor.
• There is no physical contact between these neurons.
• The point at which the nerve impulse passes from
one to another is the synapse

38. The synapse
• At its free end the axon of the presynaptic neuron
breaks up into minute branches which terminate in
small swellings called synaptic knobs, or terminal
boutons.
• These are in close proximity to the dendrites and the
cell body of the postsynaptic neuron.
• The space between them is the synaptic cleft.

39. The neurotransmitters
• In the ends of synaptic knobs there are spherical synaptic
vesicles, containing a chemical (neurotransmitter) which
is released into synaptic clefts.
• Neurotransmitters are synthesized by nerve cells, actively
transported along the axons and stored in the synaptic
vesicles.
• They are released by exocytosis and diffuse across the
synaptic cleft.
• They act on specific receptor sites on the postsynaptic
membranes.

40. The neurotransmitters
• Their action is short lived as immediately they have
stimulated the postsynaptic neuron or effector organ,
such as a muscle fibre, they are either inactivated by
enzymes or taken back into the synaptic knob.
• Usually neurotransmitters have an excitatory effect at
the synapse but they are sometimes inhibitory.
• Nor- adrenaline, gamma amino butyric acid (GABA) and
acetylcholine act as neurotransmitters in the brain and
spinal cord.