The Senses Chapter 29

Stimulus to Action Potential Sensory receptor: specialized cells/neurons that detect stimuli Sensory transduction: signal is converted to electrical potential Receptor potential: graded action potential Sensory adaptation: becoming desensitized to stimulus

5 types of stimulus Pain receptors make us aware of injury Thermoreceptors in the skin detect heat/cold Mechanoreceptors detect of touch, pressure, motion, stretching and sound Chemoreceptors detect specific chemicals – typically via protein receptors Electromagnetism receptors – sense electro- magnetic fields such as earth’s magnetic field and Light (photoreceptors)

Types of vision Most vertebrates can detect light Eye cups are a common simple form Compound eyes of insects are formed of may ommatidia Ommatidia are individual light Detecting/focusing units that form a mosaic image Vertebrate have a single-lens eye

The eye

Rods and cones Cones enable color vision, but require good lighting Rods are very sensitive to light and enable grayscale night vision Is the eye shown here from a nocturnal or diurnal?

Ears – the hearing half Pinna and auditory canal funnel sound to eardrum Sound is passed via eardrum to bones – hammer, anvil and stirrup Stirrup passes sound to inner ear via the oval window Eustachian tube equalizes pressure with atmosphere via pharynx Hairs within the fluid-filled cochlea transmit vibrations to auditory nerve

Ears – the balance half

Olfactory and Taste Taste and smell are both perceived by chemoreceptors Taste is detected on taste buds of the lounge – neurotransmitters create an action potential Olfactory (smell) is detected by sensory neurons in the nasal cavity – electrical potential created