HOMEOSTASIS & THE

NERVOUS SYSTEM

Objective

• F. Describe the structure of the brain, spinal cord, sensory

and motor neurons and sensory receptors and relate to

their function

• 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.

Guiding Ideas

Question!

• Examine the diagrams below. Do you think this is a

survivable injury? Why or why not? Please explain.

Phineas Gage

THE BRAIN

External Features of the Brain

Cerebral Cortex

Cerebral

Cortex

Cerebral Cortex - The outermost layer of

gray matter making up the superficial

aspect of the cerebrum.

The Brain Stem

What does the light blue shaded region

refer to?

What does the green shaded organ refer

to?

Lobes of the Brain

Based on the diagram, damage to which of the

following lobes would result in hallucinations?

Based on the diagram, damage to which of the

following lobes would result in mood changes

and/or social differences?

Brain Cap Activity: Step 1

Step 2:

• Wear and share your caps!

NERVOUS SYSTEM

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

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

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

1. Sensory Neurons (afferent neurons)

• Sense and relay information (stimuli) from the

environment to the CNS for processing• Example: photoreceptors, chemoreceptors and

thermoreceptors

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

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

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

Sequence of Events1. 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)

Test your reflexes!!

• http://reflextest.net/

• Extra practice and review

• http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/ne

rvesandhormones/thenervoussystemact.shtml