The nervous system is responsible for maintaining homeostasis in the body. It does this through communication between the brain and body via the central and peripheral nervous systems. The brain is made up of different sections that each perform specific tasks to regulate internal conditions. Within the nervous system, there are sensory neurons that receive information, interneurons that integrate and interpret signals, and motor neurons that activate responses in the body's effectors like muscles and glands. Together these neurons form reflex arcs that allow for rapid involuntary responses essential for homeostasis.

1. HOMEOSTASIS & THE
NERVOUS SYSTEM

2. Objective
• F. Describe the structure of the brain, spinal cord, sensory
and motor neurons and sensory receptors and relate to
their function
Guiding Ideas
• The brain is the control center of the body. The numerous
sections of the brain carry out specific tasks that function
in maintaining homeostasis.
• The nervous system is responsible for relaying messages
to/from the brain to the body.

3. Question!
• Examine the diagrams below. Do you think this is a
survivable injury? Why or why not? Please explain.

4. Phineas Gage

5. THE BRAIN

6. External Features of the Brain

7. Cerebral Cortex - The outermost layer of
gray matter making up the superficial
aspect of the cerebrum.
Cerebral Cortex
Cerebral
Cortex

9. The Brain Stem

10. What does the light blue shaded region
refer to?

11. What does the green shaded organ refer
to?

12. Lobes of the Brain

14. Based on the diagram, damage to which of the
following lobes would result in hallucinations?

15. Based on the diagram, damage to which of the
following lobes would result in mood changes
and/or social differences?

16. Brain Cap Activity: Step 1

17. Step 2:
• Wear and share your caps!

18. NERVOUS SYSTEM

19. The Importance of the
Nervous System
• Communication system that contains 100
billion nerve cells in the brain alone
• Your nervous system is active all the time
• It gets information about the depth of your
breathing, pressure on your skin,
temperature, light, odours etc.
• It controls muscle movements such as
blinking, scratching your nose.
• Memory and language are functions of the
nervous system.
• Hormones require more time than nerves do

20. Vertebrate Nervous Systems
CNS PNS
• Consists of the nerves of the
brain and spinal cord
• Coordinating Center for
incoming/outgoing
information
• Nerves that carry information
between the organs of the body and
the CNS
• Subdivided into: somatic and
autonomic nerves
• Somatic nerves: skeletal muscle,
bones and skin
• Autonomic nerves: special motor
nerves that control internal organs of
the body
• Autonomic nerves  sympathetic and
parasympathetic nervous system

22. The Types of Neurons
Neurons:
• Are the functional units of the nervous system.
• These specialized nerve cells are categorized into three
groups:
1.The sensory neurons
2.Interneurons
3.Motor Neurons

23. 1. Sensory Neurons (afferent neurons)
• Sense and relay information (stimuli) from the
environment to the CNS for processing
• Example: photoreceptors, chemoreceptors and
thermoreceptors

24. 2. Interneurons
• Link neurons within the body
• Predominantly located in the brain and spinal cord
• Integrate and interpret sensory information and
connect neurons to outgoing motor neurons
3. Motor Neurons (efferent neurons)
• Relay information to the effectors
• Effectors include muscles, organs and glands 
because they produce responses

26. Let’s suppose you touch a hot stove…
1. Heat is detected by temperature receptors in the skin
2. A nerve impulse is carried to your spinal cord
3. Sensory neuron  interneuron  motor neuron
4. Motor neuron causes the hand to contract and pull
away from the stove
5. All this happens in less than 1 second, before
information travels to your brain

27. Neural Circuits: Reflex Arc
• Reflexes are involuntary and often unconscious
• The simplest nerve pathway is the reflex arc
• Most reflexes occur without brain coordination
• Reflex arcs contain 5 essential components:
1.Receptor
2.Sensory Neuron
3.Interneuron in the spinal cord
4.The motor neuron
5.Effector

28. Sequence of Events
1. Stimulus causes signal in
sensory receptors
2. Message travels along sensory
neuron
3. Message reaches interneuron
4. Message goes to brain
5. Message travels in the motor
neuron
6. Message causes response
(muscle to contract)

29. Test your reflexes!!
• http://reflextest.net/
• Extra practice and review
• http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/ne
rvesandhormones/thenervoussystemact.shtml