Nerves

objectives Nerves copy this nerves help us react to our surroundings and control our behaviour. key parts of the nervous system include senses, neurones, brain, spinal cord, and effectors. understand what is meant by a reflex describe the pathway of information from stimulus to response.

starter www.xtcidearecords.co.uk

How fast are nerve signals? do NOT copy this The brain can respond to touch, smell or taste stimuli in just 0.1 seconds, but sound and vision take longer. Nerve impulses travel at up to 320 mph and take just 0.02 seconds to reach the brain. Photo credit: © 2006 Jupiterimages Corporation

can you catch a fiver? if not, why not? unless you guess when to close your fingers and risk going too early, you must wait until your eye detects movement of the note. This is the STIMULUS. A signal is then sent at up to 320mph from the back of the eye to the brain. The brain is the COORDINATOR, and it decides what to do. It sends a signal along more nerves to your muscles in your fingers telling them contract. The muscles are the EFFECTOR. The movement of your fingers is the RESPONSE. all this takes time, probably too much for you to catch the note but you can get better with practise, also other things can affect your reaction times

can you catch a fiver? if not, why not? stimulus light from note receptor eye nerve coordinator brain nerve effector muscles in fingers response movement of fingers copy this page ! learn keywords all this takes time !

Interpreting signals How can you find your reaction time? 1. Extend your arm over the edge of a table and have a partner hold a ruler between your fingers at the 0 cm mark. 2. The partner drops the ruler – catch it between your fingers and thumb as quickly as possible. Teacher notes The following table contains data to convert distance into a reaction time: Distance on ruler Time 5 cm 0.10 sec (100 ms) 10 cm 0.14 sec (140 ms) 15 cm 0.17 sec (170 ms) 20 cm 0.20 sec (200 ms) 25.5 cm 0.23 sec (230 ms) 30.5 cm 0.25 sec (250 ms) 43 cm 0.30 sec (300 ms) 61 cm 0.35 sec (350 ms) 79 cm 0.40 sec (400 ms) 99 cm 0.45 sec (450 ms) 3. Repeat the test 10 times, recording the results and calculate the mean (average) distance. Then convert the distance into a reaction time.

Common reflexes What types of reflexes do you know?

What are reflexes? the CNS is the brain and spinal cord Reflexes are fast, automatic protective control systems that link a stimulus to a response. a stimulus could be pain or heat or a loud sound a response could be blinking or moving away Reflex reactions happen without you thinking– they are involuntary. This is because the central nervous system (CNS) sends electrical signals to the muscles FROM THE SPINAL CORD before the brain can pick up the message. copy this page ! learn keywords

What are neurones? Neurones are specialized cells that conduct electrical impulses through the body. A nerve is a bundle of many nerve fibres enclosed within a protective sheath. Nerve fibres are the long axons of neurones together with any associated tissues. nerve nerve fibre

What do neurones look like? Neurones are elongated cells consisting of a cell body and long, thin axon. dendrites myelin sheath cell body axon Thin projections called dendrites extend from the cell body and connect with other neurones, allowing electrical impulses to pass from one to the other. The axons of most neurones are wrapped in an insulating lipid layer called the myelin sheath. Why is this important?

What are sensory neurones? Sensory neurones transmit messages from sense receptors, such as the eye or nose, to the brain or spinal cord. cell body nerve impulse from sense organ nerve impulse to CNS

What are motor neurones? Motor neurones transmit messages from the brain and spinal cord to the muscles and glands. cell body muscle

what are the differences and similarities what are the differences and similarities? (use the pictures to help) do this in groups of 4 ( one picture each) copy and complete motor neurones sensory neurones

end of part one on nerves I’ll be back !

A reflex arc

copy this page ! learn it carefully

What is a synapse? A synapse is a junction between two neurones across which electrical signals pass. The human body contains up to 500 trillion synapses. presynaptic cell postsynaptic cell

The release of neurotransmitters from a synapse When a nerve impulse arrives at the end of one neurone it triggers the release of neurotransmitter molecules from synaptic vesicles. synaptic vesicle neurotransmitter molecules copy this page ! learn it carefully

Continuing the impulse The neurotransmitters diffuse across the synaptic cleft and bind with receptors on the next neurone, triggering another impulse. synaptic cleft nerve impulse receptor

pass the zap 17 students have a card with a word or two on. you must arrange yourself in the correct order, facing the front of the class some cards are at the same time as others

True or false?

What can go wrong?

Multiple-choice quiz

homework b1a.1a b1a.1c

extra questions 1) What do these words mean: - stimulus - response - effector 2) What is the special name given to the nerve that carries the impulse from the receptor to the brain or spinal cord? 3) What is the special name given to the nerve that carries the impulse from the brain or spinal cord to the effector? 4) What is the name given to the brain and spinal cord together? 5) Write the chain of events for the following scenario: ‘a stupid year 11 boy has just thrown a pen towards a year 7 boys face. What does the year 7 boy do? Is it a reflex or does he have to think about doing it?’