Nervous system

1. The Nervous System
This presentation is to supplement the reading of the
‘Nervous System’ in your anatomy book

2. Nervous System Main Function:
This communication system controls and coordinates functions throughout
the body and responds to internal and external stimuli.
Our nervous system allows us to feel pain.

3. The Nervous System Consists of:
Brain, Spinal Cord, Nerves and Sense Organs
Sense Organs:
Eyes, Skin, Ears, Nose & Tongue

4. A nerve is an organ containing a bundle of nerve cells called
neurons daisy chained together.
Neurons carry electrical messages called impulses
throughout the body.
A Neuron

5. Neurons are aligned end to end to form a nerve
Direction of flow of the nerve impulse
Neurons never touch each other.
This gap is called a Synapse.

7. Because neurons never touch, chemical signalers called neurotransmitters must
travel through the space called synapse between two neurons. When the nerve
impulse message reaches the end of the neuron (terminals) it is converted to a
chemical messenger (neurotransmitter) and flows across the gap(synapse)
The opposite neuron picks up the chemical massager at the dendrite, and then it
is converted by to an electrical impulse message.
If the neurotransmitter travels to an organ at the end of a nerve, the organ will
act on the message delivered. i.e, a muscle fiber could be sent an impulse to
contract or relax
Axon Synapse Dendrite /Target Organ

8. NeuronTypes
There are three main types of Neurons:
Sensory Neuron: Sends “sense” messages from all over the body to the
brain via the spinal cord
Interneurons: Interpret “sense” messages delivered to the brain, decide on
an action and send its “action” messages to the desired organ(s) via the
Motor Neurons
Motor Neuron:Takes “action” messages away from the brain via the spinal
cord to organs of the body

9. A reflex arc(reflex action) is an
involuntary response where the
“sense” message is processed in the
spinal cord not the brain.
Reflexes protects the body before the
brain knows what is going on.
Reflex Arc(Reflex Action)

10. Central Nervous System (CNS)
Consists of: Brain and Spinal Cord

11. Hypothalamus
Pons-
varoliiBrain Stem
The Brain

12. Functions of the Cerebrum, Cerebellum, Brainstem & Spinal
Cord
Cerebrum: is the largest part of the brain and is composed of right
and left hemispheres. It performs higher functions like interpreting
touch, vision and hearing, as well as speech, reasoning, emotions,
learning, and fine control of movement.
Cerebellum: is located under the cerebrum. Its function is to
coordinate muscle movements, maintain posture, and balance.
Brainstem (Midbrain, Pons varoli, Medulla oblongata: acts as a
relay centre connecting the cerebrum and cerebellum to the spinal
cord. It performs many automatic functions such as breathing,
heart rate, body temperature, wake and sleep cycles, digestion,
sneezing, coughing, vomiting, and swallowing.
The spinal cord: Functions primarily in the
transmission of nerve signals from brain to the body,
and from the body to the brain. It is also a centre for
coordinating many reflexes and contains reflex arcs
that can independently control reflexes.

13. Spinal Cord &
Layers

14. Dura Mater: Surrounds the brain and the spinal cord. It envelops
the arachnoid mater, which is responsible for keeping in the cerebrospinal
fluid.
Pia Mater: The function of the pia mater is to protect the central nervous
system by containing the cerebrospinal fluid, which cushions the brain and
spine.
Arachnoid mater: Connected to the dura mater on the side closest to the CNS, this
middle layer includes a network of fibers and collagen that are part of the suspension
system that helps protect the brain and spinal cord from sudden impact.

16. Peripheral Nervous System(PNS)
Consists of: Sensory division and Motor division
Includes all sensory neurons, motor neurons, and sense organs

17. Organization of PNS
31 Pair of Spinal Nerves
 8 Cervical Pairs
 12 Thoracic Pairs
 5 Lumbar Pairs
 5 Sacral Pairs
 1 Coccygeal Pairs
Cranial nerves (12 pairs)

18. Divisions:
Sensory (afferent) division
 Somatic (skin, muscle, joints) and visceral (organs) sensory
neurons
 Conducts impulses from receptors to the CNS
Motor (efferent) division
 Motor neurons
 Conducts impulses from the CNS to effectors (muscles and glands)

19. Motor Divisions:
Somatic Nervous System
 Voluntary
 Conducts impulses from CNS to skeletal muscles
Autonomic Nervous System
 Involuntary
 Conducts impulses from CNS to cardiac muscles, smooth
muscles, and glands.
Autonomic Nervous System Divisions
 Sympathetic
 Parasympathetic