The document summarizes the organization and function of the nervous system. It discusses how the nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS). It also describes the basic components of neurons, including the cell body, dendrites, axon, and myelin sheath. It explains how neurons communicate via graded potentials and action potentials in response to stimuli and how synapses facilitate communication between neurons.

1. NEUROSCIENCENEUROSCIENCE
CHAPTER 1CHAPTER 1
ORGANIZATION OF NERVE CELLSORGANIZATION OF NERVE CELLS
By Hermizan Bin HalihanafiahBy Hermizan Bin Halihanafiah

2.  The nervous system senses changes in our internal
& external environments, coordinates and
integrates this data, and initiates & transmits action
potentials.
 Together with endocrine system maintaining
homeostasis.
 It must detect changes in & around the body.
 The nervous system is organized into two (2) basic
component:
◦ Central nervous system (CNS) – Brain and Spinal
Cord
◦ Peripheral Nervous System (PNS) – 12 pairs
Cranial Nerves, 31 pairs of spinal nerves, ganglia

3. Functionally can be divided into:
1. Sensory nervous system
◦ Somatic nervous system
◦ Autonomic nervous system
1. Motor nervous system
◦ Somatic nervous system
◦ Autonomic nervous system
1. Enteric Nervous System

4. 1. Sensory function
 Sensory receptor detect stimuli (internal and external stimuli) and
then carried in to the spinal cord and brain.
2. Integrative Function
 Integrates (processes) sensory information by analyzing and storing
the information.
 Important integrative function is perception. Perception is a
conscious awareness of sensory stimuli and occurs in the brain.
3. Motor function
 Once sensory information is integrated, the nervous system will elicit
an appropriate motor response by activating effectors (muscle and
gland) through cranial and spinal nerves.
 This stimulation causes the muscles contract and glands to secrete.

5. 1. NEURON – main function unit
2. NEUROGLIA – supportive cell

6.  Posses electrical excitability
 Able to respond to a stimulus and convert it into an action potential
 A stimulus initiate the conduction of action potential (impulses).
 Action potential is an electrical signal that propagates along the
surface of the membrane of a neuron.
 Consist :
- Cell Body
- Dendrite
- Axon
- Axon Hillock
- Axon Terminal
- Myelin Sheath
- Nodes of Ranvier
- Schwann cell
Neuron

7. Axon Hillock
Node of Ranvier

9.  Contain nucleus surrounded by cytoplasm
 Cell bodies within the central nervous system (CNS) are frequently
cluster into region called nuclei.
 Cell bodies in the peripheral nervous system (PNS) occur in cluster
called ganglia.
 Function: integrate nerve impulse, metabolic centre.

10.  Processes emerging from the cell body.
 In many neurons its form a tree shaped array of
processing extending from the cell body.
 Function: Receive information from receptor or other
neurons and send it to the neuron cell body or soma.

11.  Structure: Long, cylindrical and joint the cell body at a
cone shaped, extend from the axon hillock.
 Nerve impulses arises from axon hillock and initial
segment, called trigger zone where the action
potential begin.
 Function: Send impuls from cell body towards another
neuron, muscles fiber or a gland.

13. AXON HILLOCK
 Specialized part of the cell body (or soma) of a
neuron that connects to the axon.
 Function: initiate the propagation of the action
potential.
AXON TERMINAL (end bulb)
 Small knobs at the end of an axon (synaptic end
bulb) that release chemicals called
neurotransmitters.
 Function: conducts electrical impulses (called
"action potentials") away from the neuron's
cell body, to transmit those impulses to other
neurons

14. MYELINE SHEATH
 Consists of lipid and protein – myeline sheath.
 Axon surrounded with fat – myelinated.
 Schwann cells and oligodendrocyte cells
 Axon without covering – unmyelinated.
 Function: insulator - Increase the speed of nerve
impuls conduction.
NODES OF RANVIER
 The gaps formed between myelin sheath cells
long the axons
 Function: facilitate the rapid conduction of nerve
impulses – saltatory conduction

17.  Smaller than neuron
 More numerous than neurons
 Do not generate impulses
 Function: support, protect furnish nutrients to
neuron.
 Can be divided into:
◦ Neuroglia of the CNS (4 types)
◦ Neuroglia of the PNS (2 types)

18. 4 types of cells:
 Astrocytes
 Oligodendrocytes
 Microglia
 Ependymal cells

19.  Star shaped, have many processes and largest
and most numerous neuroglia.
 FUNCTIONS of Astrocytes
1. Strengthen and support neuron
2. Isolate neurons from harmful substances in
blood. (BBB)
3. In the embryo, regulate the growth, migration
and interconnection among neurons in the
brain.
4. Maintain appropriate chemical environment
for generation of impulses. (K+ buffering).

20.  Resembles as a astrocytes, but smaller
and contain a fewer processes.
 FUNCTION: Responsible for forming and
maintainning the myelin sheath that
covering the axon.

21.  Small cells, slender processes
FUNCTIONS:
 As a phagocytes.
 Remove cellular debris form during normal
development of the nervous system.
 Phagocytize microbes and damage nervous
tissue.

22.  Cuboidal to columnar cells arrange in a single
layer that posses microvilli and cilia.
 These line the ventricles of the brain and central
canal of the spinal cord (spaces filled with CSF).
 FUNCTION: produce, and assist in circulation of
CSF.

23. 1. Schwann Cells:
 Encircle PNS axon.
 Myelinates a single
axon.
 Participate in axon
regeneration.

24.  Flat cells
 Surrounds the cell
bodies of neuron of
PNS ganglia
 Providing structural
support and regulate
the exchanges of
materials between
neuronal cell bodies
and interstitial fluid.

25. Classification of neuron divided into two:
1. Classification by structural
2. Classification by functional

26. 1. Multipolar neurons
2. Bipolar neurons
3. Unipolar neurons

27.  Have numerous processes.
 Many dendrites
 One axon
 Part sensory neuron, Motor neuron &
interneuron are multipolar neurons

29.  Have 2 processes
 Peripheral processes (dendrite)
 Central processes (axon).
 Found in the special sense organs

30.  Have only one process.
 Have dendrites and one axon.
 The dendrite small and attach to
the axon instead of the neuron cell
body.
 Sensory neuron are unipolar
neuron.
 Functions as a sensory receptors
that detect a stimulus such as
touch, pressure, pain or thermal
stimuli.

31. Functional, neurons are classified to:
1. Sensory (afferent) neurons
2. Interneurons or association neurons
3. Motor (efferent) neurons
CLASSIFICATION OF NEURON
BY FUNCTIONAL

32. Sensory Neuron Motor neuron
Interneuron

33.  Function: Detect a stimulus from receptor and
travel along the axon to the spinal cord and
brain (CNS). It forms an action potential in its
axon and the action potential or nerve impuls.
 Contain sensory receptors at their distal ends
(dendrites).
 Most sensory neurons are unipolar.

34.  Integrate (process) incoming sensory
information from sensory neurons and then elicit
a a motor response by activating the appropiate
motor neurons.
 Located within the CNS between sensory and
motor neurons.
 Most interneuorns are multipolar neuron.

35.  Deliver action potentials away from the CNS
(brain and spinal cord) to effectors (muscles or
gland) in the PNS through cranial or spinal
nerves.
 Most motor neurons are multipolar structure.

36. Physiology of
neuron

37.  Neurons are electrically excitable.
 They communicate each other using two
types of electrical signals:
1. Graded potentials
- used for short distance communication
(receptor potential, postsynaptic
potential, end plate potential)
2. Action potentials
- used for long distance communication

38.  The production of graded potential and
action potential is depends on basic
features of plasma membrane of
excitable cells:
1. Existence of resting membrane
potentials
2. Presence of specific ion channels
* When action potential occurs in a neuron,
it is called a nerve action potential (nerve
impulse)

39.  It is the cell membrane of a non-
conduction or in the resting state.
 The difference in charges on the two sides
of the resting membrane is called the
resting membrane potential.
 This potentials is about – 70 millivolts
(mV)

40.  Transmission of the impulses and action
potential due to movement of ion across the
nervous cell membrane.
 In the resting state the nerve cell membrane is
polarised due to different concentration of ion
across the plasma membrane.
 This condition is called resting membrane
potential.

41. neuroscience1kskbsgblhvani
 Resting membrane potential:
◦ Sodium the main extracellular cation.
◦ Potassium the main intracellular cation.
Conduction of nerve impulses

42.  When stimulated, the permeability of the nerve
cell membrane to this ion change.
 Sodium flood into the neuron from extracellular
flud (ECF) causing depolarisation, creating a
nerve impuls @ action potential.
 Depolarisation is very rapid.
 Its passes from the point of stimulation in one
direction only.(away from the point towards the
area of resting membrane potential)
Conduction of nerve impulses

43. neuroscience1kskbsgblhvani

44.  During this process, potassium floods out
of the neuron cell.
 Depolarization results because inward
diffusion of sodium is much greater than
an outward diffusion of potassium
DEPOLARIZATIONDEPOLARIZATION

46. ◦ Voltage gated Na+ channels are closed.
◦ Voltage gated channel K+ are open.
◦ Sodium ion diffusion into the cell stops and K+
diffuse out of the cell, causing repolarisation.
 Resting membrane potential is reestablish after
the voltage gated K+ channels closed.
REPOLARIZATIONREPOLARIZATIONREPOLARIZATIONREPOLARIZATION

47. neuroscience1kskbsgblhvani

50.  Definition of Synapse
◦ The site of communication between 2 neurons
or between neuron and effector cells (muscles
or glands).
 The tips of some axon terminals swell into bulb
shaped structures called synaptic end bulbs.
 Synaptic end bulbs contain many tiny
membrane-enclosed sacs called synaptic
vesicles that store a chemical called
neurontransmitter.

51.  The site of communication between 2
neurons or between neuron and effector cells
(muscles or glands).
 Neuron sending the signal is called the
presynaptic neuron.
 Neuron receiving the message is called the
postsynaptic neuron.

52. Tjere are 2 types of synapse:
1. Electrical synapse
◦ Action potential conducts directly between
adjacent cells through structures called gap
junction.
1. Chemical synapse
◦ neuron releases a neurotransmitter.
◦ Presynaptic and postsynaptic neuron
separated by synaptic cleft.
◦ Postsynaptic neuron receives the chemical
signal – postsynaptic potential.
TYPES OF SYNAPSE

53.  Although the plasma membrane of presynaptic
and postsynaptic neuron in a chemical synapse
are close, they do not touch.
 The synaptic cleft, a space of 20-50 nm that is
filled with interstitial fluid, separated the two
neurons.
 The presynaptic neuron converts an electrical
signal (nerve impuls) into a chemical signal
(release neurontransmitter).
 The postsynaptic neuron receives the chemical
signal and generate an electrical signal
(postsynatic potential).

54. A typical chemical synapse transmits a signal as
follows:
1. A nerve impulse arrives at a synaptic end bulb of a
presynaptic axon.
2. The depolarizing phase of the nerve impulse opens
voltage gated Ca2+ channels, which are present in the
membrane of synaptic end bulbs.
3. Increase [Ca2+] inside the presynatic neuron is the
triggers exocytosis of some of the synaptic vesicles. As
vesicles membrane merge with the plasma membrane,
neorontransmitter molecules released into the synaptic
cleft.

55. 4. The neurontrasmitter molecule diffuse across the
synaptic cleft and bind to neurontransmitter
receptor in the postsynaptic neuron plasma
membrane.
5. Binding of neurontransmitter molecules to their
receptor on ligand-gated channels opens the
channels and allow particular ions to flow across
the membrane.
SIGNAL TRANSMISSION AT
SYNAPSES
SIGNAL TRANSMISSION AT
SYNAPSES

56. 6. As ions flow through the opened channels, the
voltage across the membrane changes. This
change in membrane voltage is a postsynaptic
potential.
7. When a depolarizing postsynaptic potential
reaches threshold, it triggers one or more nerve
impulse.

58.  Synapse between somatic motor neuron and
skeletal muscles fiber.
 Structures of the presynaptic neuron same with
other neurons.
 NT released in the synaptic cleft – Ach.
 The region of the sarcolemma opposite to the
synaptic end bulbs are called motor end plate.
 Within the MEP, there is many ACh receptors.
 Attachment of Ach on its receptor permits influx
Na ions inside muscles fiber, thus generate
action potentials.