The nervous system

1. The Human Nervous System

2. Lesson 1: The Human Nervous System
Learning Intentions:
• Describe the role and function of the two major divisions of the nervous
system: CNS and PNS
• Describe the role and function of the Somatic Nervous System including
the roles of the motor, sensory and interneurons

3. Today’s lesson
-Central Nervous System CNS
-Peripheral Nervous System PNS
-Somatic division of PNS
Next Lesson
-Autonomic division of PNS
(sympathetic and parasympathetic)

5. Central Nervous System
CNS
- The central nervous system is that part of the nervous system that
consists of the brain and spinal cord.
- The brain is the centre of the nervous system in all vertebrate and
most invertebrate animals. The brain controls the other organ systems
of the body, either by activating muscles or by causing secretion of
chemicals such as hormones and neurotransmitters.
- The spinal cord is the main pathway for information connecting the
brain and peripheral nervous system.

6. Peripheral Nervous System
PNS
-Peripheral means outside the centre or in the surrounding areas.
-The peripheral nervous system (PNS) is comprised of all the neurons outside the central
nervous system.
-It is located mainly in the body (with the exception of the spinal cord), although the cranial
nerves in the head (outside the skull) are also part of the peripheral nervous system. These
are the only nerves in the PNS that enter the brain (CNS) without going via the spinal cord.
-The PNS provides the pathway from the brain and spinal cord to all other parts of the body
(including the internal organs and glands).
-It allows two-way communication between the CNS and all other areas.
-The peripheral nervous system is separated into two other divisions, which are distinguished
by their different functions. These are the somatic nervous system and the autonomic
nervous system.

7. Somatic Nervous System
SNS
The somatic nervous system is involved in all skeletal muscle activity
enabling you to perform voluntary actions such as writing, texting,
chewing, talking, goal-shooting, riding a surfboard and dancing.

8. Sensory neurons (also called afferent neurons) are specialised nerve cells
that receive and carry sensory messages. These neurons generally respond
only to a particular type of stimulation. For example, sensory neurons in the
eyes respond only to light, but not to other types of stimulation such as
mechanical energy (sound), odours (smell) or pressure (touch).
Sensory
Neuron

9. Motor neurons (also called efferent neurons) are specialised nerve
cells that carry messages to skeletal muscles causing them to
contract or relax
Motor
Neuron

10. Interneurons (also called connecting neurons) perform the important
function of making the connection between sensory and motor neurons,
which rarely ever connect directly. They are found only in the CNS and they
are the most abundant type of neuron in the brain.
Interneuron

12. Acronym SAME
Somatic Nervous System: Sensory and Motor Neurons
Sensory (afferent) neurons carry messages from body to CNS
Motor (efferent) neurons carry messages from CNS to body
(sensory afferent motor efferent)