Revision the nervous systemPresentation Transcript
The Nervous system
The Nervous System What are its component parts? • Brain • Spinal cord • Nerves What does it do? • Enables you to control your body • Gives you feedback about the world
Look away if you’re squeamish… A dissected brain, spinal cord and sections of major nerves.
How the nervous system worksFor example;If you smell something burning…• Your nose (receptor) detects the stimulus receptor (smell)• Nerve fibres send the message to the brain• Your brain then sends a message to move your body away or to put out the fire! SIMPLES RIGHT!
Lets look at some bits more closely RECEPTORS• Receptors are sensors on the body that detect stimuli• They convert stimuli into electrical signals (messages) called impulses.
EFFECTORSAn effector is any part of the body that produces the response. responseHere are some examples of effectors:• a muscle contracting to move the arm• a muscle squeezing saliva from the salivary gland• a gland releasing a hormone into the blood
The Cells of the Nervous System - Neurones
NERVE FIBRES• Nerve fibres are bundles of nerve cells (neurones) that pass on electrical signals (impulses) to the brain.• From the brain, nerve fibres send impulses to effectors (muscles).
NEURONESThere are three types of neurones1. Sensory neurone – carries impulses from the receptors to the spinal cord.2. Relay Neurone – carries impulses to and from the spinal cord and the brain3. Motor Neurone – carries impulses from the brain to the effector
The route impulses take
The route impulses take Sensory Relay neurone neurones (in brain or spinal cord)Effectors – Motor neurone
Left: sensory neuroneRight: motor neurone
Nerves – bundles of neurones
Sensory Receptors• Information from our environment is received via our senses.• The Eye receives light and transfers this information via our optic nerve to our brain.• Our Ear receives sound and via the auditory nerve sends messages to our brain• Our Skin receives messages about temperature, pain and pressure and via sensory nerves sends this information to our brain.
• The skin and body temperature – the skin helps to keep your body at a constant 37°C +/- 1˚C.• Sweating, shivering, body hair and fat beneath the skin all help this. Also, capillaries in the skin surface open or close to lose heat or keep heat in.• This vasodilation (opening) and vasoconstriction (closing) of blood vessels helps to lose or conserve body heat
cornea Inside the eye protects eye surface and focuses light rayssuspensory ligaments retinahold lens in place senses light lens focuses light on retina iris regulates amount of light entering eye optic nerve ciliary muscles transmits impulses to the change shape of the lens brain
ACTION In bright In dim lightThe way the iris in our light eye adjusts the size •Radial muscles of •Radial muscles of of the pupil in the iris relax. the iris contract. response to bright •Circular muscles •Circular muscles or dim light is a of the iris contract. of the iris relax. reflex action. •Less light enters •More light enters the eye through the the eye through the contracted pupil. dilated pupil. http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystem
Reflex Reactions – bypassing the brain for extra speed
Reflex ReactionsCan you think of any?• Startle reflex – moving away, contraction of arm and leg muscles, blinking, breathing changes• Withdrawal reflex – moving away from potentially harmful influences (e.g. high temperature)• Iris reflex – pupil becomes smaller in bright light
Knee Jerk Reflex
Why the knee jerk reflex?• This reflex is quite useful for walking. Every time you put weight on your foot, your muscles contract to support you. Without this reflex, we would all look silly staggering around, having to consciously think about working our muscles for each step, but with the muscles reacting too hopelessly late to be useful. Chewing gum at the same time would be out of the question.
Endocrine System• As well as sending and receiving messages using our nervous system, we also use our endocrine system to do the same job.• Instead of using electrical impulses however, this system releases chemicals into our blood stem called hormones.• These hormones are not a fast acting as nervous impulses but are longer lasting.
HormonesPituitary gland – FSH, LH (stimulates the release and maturity of follicles during menstruation)Thyroid gland – Thyroxine (regulates the rate of metabolism)Adrenal gland - corticosteroids and catecholamines including cortisol and adrenaline and small amounts of testosterone (regulates stress levels)Pancreas – peptides (regulates the production of shorter active digestive enzymes)Ovary – oestrogen, progesterone and small amounts of testosterone (regulates the growth of eggs and stabilises the growing foetus during pregnancy)Testis – testosterone (plays a key role in the health and well-being of the man)