1. The Senses
Chapter 29

2. 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

3. 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)

5. 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

7. The eye

9. 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?

10. 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

11. Ears – the balance half

12. 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