NERVOUS SYSTEM & SENSES TEACHER COPY
FUNCTIONS OF THE NERVOUS SYSTEM What are the three functions of the Nervous System? 1. Receives information about what is happening inside and outside of your body 2. Directs how your body responds to information- 3. Helps maintain homeostasis- ex. Eating when hungry How does your body do this? 1. Stimulus- a change in the environment that causes an reaction 2. Response- what your body does in reaction to the stimulus
THE NEURON Neurons or nerve cells carry information through your nervous system. The message that a neuron carries is a called a nerve impulse Neurons has a large cell body that contains the nucleus, threadlike extensions called dendrites and an axon. Dendrites carry impulses to the cell body Axons carries impulses away from the cell body. Dendrites Cell Body Axons
DIFFERENT KINDS OF NEURONS There are three kinds of neurons found in the body 1. Sensory neurons- pick up stimuli from the internal or external environment 2. Interneurons- receives the nerve impulses from sensory neurons and carries it to other interneurons or motor neuron. 3. Motor neurons- sends an impulse or response to a muscle or gland in the body.
HOW NERVE IMPULSES TRAVEL 1. Receptors pick up stimuli form the environment. The receptors trigger nerve impulses in sensory neurons. 2. The nerve impulse passes from sensory neuron to interneurons in the brain 3. Impulses travel from the interneuron to travel along thousands of motor neurons that lead to muscles. Muscles carry out the response.
THE SYNAPSE The junction where one neuron can transfer an impulse to another is called a synapse A nerve impulse must cross the gap between the axon and the dendrite of the next neuron. The axon tips release chemicals that carry the impulse across the gap.
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DIVISIONS OF THE NERVOUS SYSTEM Your nervous system has two divisions that work together 1. Central nervous system- brain and spinal cord 2. Peripheral nervous system- all the nerves outside of the central nervous system
THE BRAIN Your brain has 100 billion interneurons! There are three main regions of the brain that receive and process information. These are the cerebrum, cerebellum and brain stem. Cerebrum Cerebellum Brain stem -Largest part of the brain -interprets input from the sense, controls movement, carries out complex mental processes - Second largest part of your brain - Coordinates your muscles and balance -Controls involuntary actions
THE CEREBRUM The cerebrum is divided into right and left halves. The right half sends messages to the skeletal muscles on the left half of your body and vice versa. Certain areas of the cerebrum are associated with small, touch, taste, hearing and vision as well as movement, speech, written language and abstract thought.
VISION Your eyes respond to the stimulus of light. They convert that stimulus into impulses that your brain interprets, enabling you to see. So how do you see things? Rays of light passes through the clear tissue called the cornea. Then the light rays continue through a fluid filled chamber behind the cornea and reaches the pupil. The pupil is the opening where light enters the eye. The size of the pupil is adjusted by muscles in the iris which is the colored circle around the pupil.
VISION The light rays continue to pass through the pupil and to the lens. The lens focuses the light similar to a camera. After passing through the lens the light rays strike the retina which is the layer of receptor cells that lines the back of the eye. The retina contains 130 million receptor cells that respond to light. There are two types of receptors 1. Rods- work best in dim light to see black, white, and shades of gray. 2. Cones- work best in bright light and allows you to see colors. Brain pop Vision
VISION What colors do you see?
VISION What s going on here
VISION What direction is she spinning Clockwise counterclockwise
SMELL & TASTE The sense of smell and taste work closely together. Both depend on chemicals in food or in the air. The chemicals trigger responses in receptors in the nose and mouth. Nerve impulses travel to the brain where they are interpreted as smell or taste The nose can distinguish at least 50 basic odors where as there are only five main taste sensations 1. Sweet 2. Sour 3. Salty 4. Bitter 5. umami
TASTE AND SMELL The Miracle berry
HEARING AND BALANCE Your ears are the sense organs that respond to the stimulus of sound. The ears convert the sound to nerve impulses that your brain interprets. Sound is produced by vibrations. The vibrations cause particles like gas molecules in the air to vibrate and carry the sound. These sound waves enter the ear first at the area called the outer ear. This funnel shaped structure gathers sound waves
HEARING AND BALANCE At the end of the ear canal vibrations reach the eardrum which is the start of the middle ear. Your eardrum vibrates when sound strikes it similar to a drum. Vibrations pass from the eardrum to the three smallest bones in the body the hammer, anvil, and stirrup. The vibrations are passed from the hammer to the anvil then to the stirrup.
HEARING AND BALANCE The stirrup vibrates against a thin membrane that covers the inner ear which channels the vibrations into the fluid in the cochlea. The cochlea is a snail-shaped tube lined with receptor cells that respond to sound. When the fluid vibrates it stimulates these receptors. Sensory neurons send nerve impulses to the cerebrum through the auditory nerve Above the cochlea are the semicircular canals which are responsible for your sense of balance. tone test