This document discusses the nervous system. It describes how the nervous system coordinates the activities of the body and is divided into the central nervous system (brain and spinal cord) and peripheral nervous system (nerves and supporting cells). Information flows from receptors that detect stimuli through sensory neurons to the central nervous system, which processes the information and sends messages through motor neurons to organs and glands. Neurons are the basic functional units and transmit electrical signals called action potentials. The document also describes the structure of neurons, types of neurons, synapses, and reflex arcs.

1. Nervous system
2.49 -2.53
Pages: 144 to 157

2. 2.49: Coordination
Cells and organs of the body don’t work
independently.
Their activities are coordinated = they work
together carrying out various functions at certain
times and at certain rates.
Coordination is achieved through two systems:
- The nervous system
- Endocrine system = hormones system
( see text book page: 144, comparison between
Nervous and endocrine system)

3. Nervous system
It is divided into two main systems:
- Central nervous system (CNS):
Brain and spinal cord
- Peripheral nervous system:
Nerves and supporting cells
Nerve cells are called: Neurons

4. Nervous system
Information flows along the nervous system as follows:
- A receptor detects a change in condition ( stimulus)
- A massage is carried from the receptor to the CNS by a sensory
neuron.
- After processing, a massage is sent from CNS to an organ (effector)
that carry out the response by a motor neurons.

5. Peripheral nervous system: gathers information
and sends it to the central nervous system.
Input
Central nervous system: Process the information
and form a response.
Output
Peripheral nervous system: Carries the response
of the central nervous system to target cells (
glands or muscles)

6. Nervous system
 Nervous system is made mainly up of nerve cells.
 Nerve cells are called: Neurons
 The messages carried by the nervous system are electrical
impulses called action potentials.
 Nervous system impulses are transmitted by neurons

7. Neuron

9. Structure of neurons
Cell body: is the largest part that contains the nucleus
and much of cytoplasm.
Dendrites: branched extensions which receive impulses
from other neurons and carry them to the cell body.
Axon: long fiber that carries impulses away from the cell
body.
Myelin sheath: insulating membrane that protect the axon
and prevent the electrical current from leaving the axon.
Nodes: where axon membrane exposed. Impulses jump
from one node to the other

10. Types of neurons
 There are three types of neurons according to the
direction in which an impulse travels:
1- Sensory neurons: carry impulse from the sense
organs such as eyes and ears to the spinal cord and
the brain.
2- Motor neurons: carry impulse from the brain and the
spinal cord to the muscles and the glands.
3-Interneurons (connecting neurons) they connect the
sensory and the motor neurons.

12. Synapse

13. The synapse
In the nervous system, a synapse is a structure that let
a neuron to pass an impulses to another cell (neural or
target cell)
cleft
-Synaptic cleft:
the space that
separates the axon
terminal from, the
adjacent cell.
- Neurotransmitter:
Chemical that
transmit an
impulse across a
synapse to another
cell

14. 2.50: Reflex arc

15. 2.51: Muscles can work as effectors: Joints in the
skeleton allow movement (Synovial joint)
ligament

16. Antagonistic muscles