Fibers kind of like a harp - Longer at one end than the other - Lower frequency vibrates at apex - Higher frequency vibrates at the base Motion receptors - Can detect gravity - Invertebrates have statocyst to detect motion - Vertebrates - Utricle and saccule detect vertical and horizontal motion - Hair cells with crystals - Membrane moves to impulse - Semicircular canals: angular motion - Cupula movement of fluid Chemoreceptors- taste - Perception of taste: gustation - Sweet, salty, bitter, sour, uname - Sensed by taste buds and other sensors in oral cavity - Salts and K go directly into ion channels - Other three couple with g protein receptors Chemoreceptors-Smell - Receptors in nasal mucosa - Nasal passages - Cilia on dendrites project to axon - Goes directly to cerebral cortex Chemoreceptors pH - Inside the body - Blood pH - Peripheral chemoreceptors - Aortic and carotid bodies - Cerebrospinal fluid - Medulla oblongata - Central chemoreceptors - Increased CO2 in blood decreases pH Photoreceptors-vision
- Eyespot detects light Vertebrate eye structure - Light enters and focuses with cornea and lens - Pupil lets in light - Iris contracts to change pupil size - Ciliary muscle changes lens - Retina: surface of the back of the eye - Layer 1: rods(gray light) and cones (color) - Layer 2: bipolar cells- info sent - Layer 3: ganglion cells send info to brain - Vertebrates have a blind spot Sensory transduction- dark and light - Dark causes depolarization - Light becomes hyperpolarization Uncommon - Snakes : pit organs to detect heat to hunt prey - Fish: electrical currents - Various: magnetic fields Transduction into Nervous System - Stimuli : sound waves - Transduction: receptor potential - Stimulus changes the state of the receptor - Receptor potentials are graded - Transmission - Action potential - Graded potentials degrade over short distances - Stimulates adjoining neurons - Integration - Brain perception Mechanoreceptors - Touch, pressure, blood, pain, temp, vibration - Types - Nociceptors: pain, response to tissue damage - Tonic receptors: duration information, slow but steady during stimulation - The stronger the stimuli the more rapid the action potentials (frequency increases)
- Phasic receptors: convey information about intensity and rate, action potentials increase and diminish very quickly -
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- Spring '08