Sensory Receptors

(a) Receptor is afferent neuron.(b) Receptor regulates afferent neuron. To CNS Afferent neuron To CNS Receptor protein Sensory receptor Stimulus Neurotransmitter Sensory receptor cell Stimulus Stimulus leads to neuro- transmitter release. Figure 50.3

Figure 50.4a (a) Single sensory receptor activated Gentle pressure Sensory receptor More pressure Low frequency of action potentials per receptor High frequency of action potentials per receptor

Figure 50.4b (b) Multiple receptors activated Sensory receptor Gentle pressure More pressure Fewer receptors activated More receptors activated

Gentle pressure, vibration, and temperature Connective tissue Hair Pain Epidermis Dermis Hypodermis Nerve Hair movement Strong pressure Figure 50.5

Figure Papillae Papilla Taste buds (a) Tongue Key Sweet Salty Sour Bitter Umami Taste bud Sensory neuron Sensory receptor cells Food molecules Taste pore (b) Taste buds

Figure Odorants Brain Nasal cavity Receptors for different odorants Plasma membrane Odorants potentials Action Olfactory bulb Bone Epithelial cell Chemo- receptor Cilia Mucus

Sclera Suspensory ligament Cornea Iris Pupil Aqueous humor Lens Vitreous humor Optic disk Central artery and vein of the retina Optic nerve Fovea Retina Choroid Figure 50.17aa

Retina Neurons Photoreceptors Rod Cone Optic nerve fibers Ganglion cell Amacrine cell Bipolar cell Horizontal cell Pigmented epithelium Figure 50.17ab

CYTOSOL INSIDE OF DISK Retinal Opsin Rhodopsin Figure 50.17bb

Figure Light Inactive rhodopsin Active rhodopsin Transducin Phosphodiesterase INSIDE OF DISK Disk membrane CYTOSOL GMP cGMP Na  EXTRA- CELLULAR FLUID Plasma membrane Dark Light Hyper- polarization Time 0  40  70 Membrane potential (mV)

Outer ear Middle ear Inner ear Skull bone Malleus Incus Stapes Semicircular canals Auditory nerve to brain Cochlea Eustachian tube Round window Oval window Tympanic membrane Auditory canal Pinna Figure 50.10a

Figure 50.10b Cochlear duct Bone Auditory nerve Vestibular canal Tympanic canal Organ of Corti

Figure 50.10c Tectorial membrane Basilar membrane Hair cells Axons of sensory neurons To auditory nerve

Figure 50.10d 1  m Bundled hairs projecting from a hair cell

Figure Tympanic membrane Cochlea Stapes Base (a) Round window Point A A A 10 Tympanic canal Basilar membrane Point B B B 20 Point C C C 30 Apex Vestibular canal Oval window Axons of sensory neurons (b) Distance from oval window (mm) 6,000 Hz 1,000 Hz 100 Hz Relative motion of basilar membrane

Semicircular canals Vestibular nerve Vestibule Utricle Saccule PERILYMPH Fluid flow Cupula Hairs Hair cell Nerve fibers Body movement Figure 50.13