Taste

Papillae Bumps that cover the tongue surface

10,000 taste buds are crammed into the tongue Found in grooves, detect taste 10,000 taste buds are crammed into the tongue

Saliva Water-like fluid that dissolves chemicals in food making them detectable We produce 2-3 pints a day

Types of Taste

Bitter At back of tongue

Sour On sides of tongue

Salty Along sides and tip of tongue

Sweet At tip of tongue

Umami Savory taste of foods like steak and cheese

Review

Smell

Nose Main organ of smell What’s the difference between smelling and breathing?

Nose Receptor cells in the top of the nose detect chemicals in the air

Smell Humans have 5-6 million receptor cells in the nose and can recognize 10,000 different smells Rabbits have 100 million Dogs have 220 million

Nose Olfactory nerves send messages to brain

Smell 80% of what we “taste” is actually smell Foods can lose their “flavor” when we get sick

Smell The nose and mouth are linked at the throat We can smell food as we chew it

Why is smell important?

Touch

Skin The sense organ for touch Largest organ of the body

Two layers:

Epidermis Outside layer made of dead cells

Dermis Inside layer made of living cells

Receptors Most are in the dermis Allow us to feel: Heat Cold Touch Pressure Pain

Heat Receptors Detect heat

Cold Receptors Detect cold

Touch Receptors Detect light touch

Pressure Receptors Detect deep pressure

Pain Receptors Detect pain, found very close to surface of skin

Hair Movement Can feel hairs moving without touching skin

Nerves Receptors connect to nerves throughout the body Sensory Nerves Motor Nerves

Nerves Sensory nerves – collect information and send it to the brain

Nerves Motor nerves – sends messages from brain to body to respond

Try It Receptors, Sensory Nerves, Spinal Cord, Brain, Spinal Cord, Motor Nerves, Muscles

Not worth noticing Brain receives messages all the time, but filters out the less important ones

Sensitivity depends a lot on how close together the receptors are and how deep they are

Sensitive areas Fingertips – about 3,000 touch receptors

Sensitive areas Lips – skin is very thin

Other areas Tongue – lots of pain receptors but not so many hot or cold receptors

Other areas Feet – calluses can make them less sensitive

Not so much… Middle back, legs, elbows

Using our sense of touch

Braille Using raised dots to represent letters and numbers

Braille

Braille M a l i a K u n d e