The Senses

Review! Divisions of the Nervous System

Review: Reflex Reflex: quick, automatic response to a stimulus Allows your body to respond to danger immediately Reflex Arc: includes a sensory receptor, sensory neuron, motor neuron, and effector

Fight or Flight Response Which portion of the PNS is responsible for the fight or flight response? What are some ways that your body responds? What is the evolutionary history to this response? (why did it arise in the first place?) Fight or Flight Video

Sensory Receptors Sensory Receptors: neurons that react to a specific stimulus 5 types of sensory receptors: Pain receptors Thermoreceptors Mechanoreceptors Chemoreceptors Photoreceptors Sensory Receptors are located throughout the body but they are concentrated in the sensory organs (eyes, inner ears, the nose, the mouth, and the skin) The body contains millions of neurons that react directly to stimuli from the environment, including light, sound, motion, chemicals, pressure, and changes in temperature Make link to organ and receptor Located throughout the body but are concentrated in the sense organs Sense organs: eyes, inner ears, the nose, the mouth, and the skin Sensory receptors within each organ enable it to respond to a particular stimulus

Sensory Receptors Pain receptors: Thermoreceptors: Located throughout the body, except in the brain Respond to chemical released by damaged cells Thermoreceptors: Located in the skin, body core, and hypothalamus Detect variations in temperature

Sensory Receptors Mechanoreceptors: Chemoreceptors: Photoreceptors: Located in the skin, muscles, and inner ears Respond to touch, pressure, stretching of muscles, sound, and motion Chemoreceptors: Located in the nose and taste buds Sensitive to chemicals in the external environment Photoreceptors: Located in the eyes Sensitive to light What receptors were we testing at compass station

Vision

Vision Iris: Color portion of the eye Pupil: middle of the iris, allows light to enter eye Lens: Focuses light onto the back of the eye (Retina) Photoreceptors are arranged in a layer onto the retina Rods: Black and white Cones: Respond to different colors Cones are concentrated on the macula fovea Pupil trick with light Tiny muscles in the iris adjust the size of the pupil depending on the amount of light Two types of photoreceptors

Myopia Nearsightedness: Close objects are clear Distant objects are blurry Eye is too long

Hyperopia Farsightedness Distant objects clear Near objects blurry Eye is too short

Blind Spot Area on the retina without receptors that respond to light Located where the optic nerve exits the eye

Vision How we see

Vision Stations Copy the highlighted charts into your Notebook and record your data at each of the stations. For each station, copy the highlighted chart into your Notebook and follow the provided directions. Station 1: Where is your blind spot? Station 2: Optical Illusions: What is real? Station 3: How is your depth perception? Station 4: Reaction Time

Hearing and Balance The ear has two sensory functions: hearing and detecting potential changes associated with movement Vibrations enter the ear through the ear canal The vibrations cause the eardrum to vibrate Vibrations of the oval window create pressure waves in the fluid-filled cochlea Hair cells in the cochlea produce nerve impulses that are sent to the brain through the cochlear nerve Ear infection is a bacterial or viral inflammation of the middle ear Balance is determind by semi-circular canals

Hearing and Balance How we hear

Smell and Taste Smell chemoreceptors in the lining of the nasal passageway respond to specific chemicals and send impulses to the brain through sensory nerves Much of your taste of food is actually smell Taste: chemical sense. Taste buds detect taste 5 tastes: Salty, Bitter, Sweet, and Sour, Umami (meaty) Humans are capable of detecting more than 10,000 different odors

Smell and Taste How we smell and taste

Touch All regions of the skin are sensitive to touch The skin is actually the largest sense organ Skin contains sensory receptors that respond to temperature, touch (pressure), and pain Not all parts of the skin are equally sensitive to touch because not all parts have the same number receptors Greatest density of touch receptors are found on fingers, toes, and face

Touch How are skin perceives touch

Senses Stations Station 1: A penny heard… Station 2: Are you a super taster? Station 3: The Link Between Taste and Smell Station 4: Two Point Touch