Central Nervous System National 4 & 5: Multicellular Organisms

Internal Communication Multicellular organisms are made up of many different tissues and organs Cells do not work independently, so they communicate with each other Also, different tissues and organs need to communicate with each other Communication is usually carried out in 2 ways: - hormones - nerve signals

Learning Outcomes Identify the discrete areas of the brain and understand their functions Identify the different typed of nerves/neurones in the human body Examine the role of each type of nerve/neurone Explain how a reflex action works, and identify examples of this Examine how information is passed from one neurone to another

What is the nervous system composed of? The nervous system is composed of: - the brain - the spinal cord - nerves

The Brain Cerebrum - conscious thought, reasoning, imagination Cerebellum - balance and co-ordination Medulla (brain stem) - heart rate and breathing rate

Brain facts The brain is approximately 75% water It weighs about 3 pounds, BUT uses between 20%-25% of your energy supplies each day Your brain can survive without oxygen for 4-6 minutes before it starts to die There are over 100, 000 miles of blood vessels in your brain There are over 100 billion neurons in your brain It’s not true that humans only use 10% of their brains; each part of the brain has a purpose The slowest speed information passes around your brain is approximately 260 mph The number of internal thought pathways that your brain is capable of producing is one followed by 10.5 million kilometers of standard typewritten zero’s! Brain facts

Central Nervous System (CNS) Consists of the brain and spinal cord 1) Stimulus (change) picked up by receptor 2) Impulse carried along nerve cell (Sensory neurone) to spinal cord 3) CNS processes info & sends a response Impulse carried along nerve cell (motor neurone) to effector organ 4) 5) Effector organ brings about a response

Receptors and effectors Receptors are found all over the body, often as part of sense organs E.g. eyes, ears, skin They work in response to a stimulus The more receptors, the more sensitive an area usually is to a stimulus Effectors are also found all over the body They act in response to the CNS The more effector cells are in a body part, the more it can move or the faster it can act Effectors are often either muscles or glands - muscles respond rapidly - glands respond more gradually

Sight Sense Stimulus Sense organ Sight light eyes

Smell Sense Stimulus Sense organ Smell chemicals nose

Skin Sense Stimulus Sense organ Temperature heat / cold skin Pain damage Pressure force Touch contact

Hearing/balance Sense Stimulus Sense organ Hearing sound ears Balance movement / position part of inner ear

Taste Sense Stimulus Sense organ Taste chemicals tongue and throat

The Reflex Arc A reflex is a rapid, unconscious response to a stimulus e.g. blinking, pulling a hand off a hot surface Receptor cells send an impulse along the sensory neurone to the CNS Relay neurone The relay neurone transfers the impulse to the motor nerve sensory neurone The motor neurone transfers the impulse to the effector cells, to carry out the response motor neurone

What happens in a goalie’s body as he tries to save a goal? The greatest goals of all time

What happens in a goalie’s body as he tries to save a goal? Mark each other’s work: 1 point if they have used any of these words: Eye(s) Brain 2 Points: Nerve(s) Muscle(s) 3 Points: Neurone(s) Receptor(s) Spinal cord 4 Points: Motor (neurone) Sensory (neurone) Use your judgement – any other scientific words that they have used correctly that should get points?

Reflex responses You have been given a series of cards for a series of reflex actions You must arrange them under the following headings Stimulus Receptor Response Co-ordinator Effector Response

How fast are your reflexes?? 1.Using a ruler you have to see how quickly you can catch it. 2. Each person will try three times and record their results in a table 3. We will then collect the class data

Results Name Result 1 (mm) Result 2 (mm) Result 3 (mm) Average (mm)

Who is the fastest - Class results Name Average reflex (mm) Remember Title, label axis, Graph Average reflex (mm) Pupil Name

Transfer of information along neurones Information is carried through the CNS by a series of neurones Information is picked up by a neurone through a dendrite Then it is passed to the cell body It then gets passed towards the next neurone by an axon fibre

Structure of a synapse Between each neurone is a small gap called a synapse To pass information between neurones, a chemical passes across this synapse These chemicals are called neurotransmitters

Re-Cap What is meant by the term reflex action? Give an example of a reflex action. What is the function of the sensory nerve? What part of the brain controls our breathing rate? What part of the brain controls our balance? What part of the brain is responsible for our memory?