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The Brain Central sulcus Frontal lobe Parietal lobe Parietooccipital notch Occipital lobe Lateral fissure Temporal lobe Preoccipital notch Supplementary motor area (programming of complex movement) Primary motor cortex (Voluntary movement) Premotor cortex Central sulcus (coordination of complex movements) Prefrontal association cortex Somatosensory cortex (Somesthetic sensation and proprioception) Posterior parietal cortex (integration of somatosensory and visual input) Parietal lobe (planning for voluntary activity; decision making; personality traits) Wernicke’s area (speech understanding) Frontal lobe Parietal-temporal-occipital association cortex Broca’s area (speech formation) (integraton of all sensory inputimp in language) Primary auditory cortex Occipital lobe Limbic association cortex (motivation, emotion, memory) Temporal lobe Primary visual cortex Sensory Motor Cranial nerves = Motor fibers = Sensory fibers I-Olfactory nerve Retina Mucosa of nasal cavity II- Optic nerve III- Oculomotor nerve Olfactory bulb V- Trigeminal nerve IV - Trochlear nerve Sensory—face and head Sensory— taste buds on anterior tongue VII - Facial nerve The Senses Major Sensory Receptors in the Human Body Table 12.1 p. 409 • Category and type of receptor Photoreceptors vision Chemoreceptors taste smell internal senses Mechanoreceptors touch/pressure/pa in hearing balance body position Thermoreceptors temperature Examples of receptor Stimulus rods and cones in the eye visible li ght taste buds on the to ngue olf actory receptors in the nose osmoreceptors in the hypothalamus receptors in the carotid artery and aorta food particles in sali va odour molecules low blood volume receptors in the skin hair cell s in the inner ear hair cell s in the inner ear proprioceptors in the muscles and tendons, and at the joints mechanical pressure sound waves fluid movement muscle contraction, stretching, and movement heat and cold receptors in the skin change in radiant energy blood pH Sensory Receptors • When receptors are triggered, they open up Na+ and K+ channels to trigger an action potential The Sense of Sight • The Eye Photoreceptors (eye) • The image-forming eyes of vertebrates focus detailed images of the visual field onto dense arrays of photoreceptors that transduce the visual image into neuronal signals. Eye structure Focusing Photoreceptors (eye) • Vertebrates have two types of photoreceptors, rod cells and cone cells. In humans, the fovea contains almost exclusively cone cells, which are responsible for color vision but are not very sensitive in dim light. • Color vision is based on the fact that different cone cells contain different isomers of opsin, which give them different spectral absorption properties. Photoreceptors (eye) • Photosensitivity depends on the absorption of photons of light by rhodopsin, a photoreceptor molecule that consists of a protein called opsin and a light-absorbing prosthetic group called retinal. • Absorption of light by retinal is the first step in a cascade of intracellular events leading to a change in the membrane potential of the photoreceptor cell. Overview animation Photoreceptors (eye) • The innermost layer of the retina consists of the ganglion cells, which send their axons in the optic nerve to the occipital lobe of the brain. • Between the photoreceptors and the ganglion cells are neurons that process information from the photoreceptors. QuickTime™ and a TIFF (U ncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (U ncompressed) decompressor are needed to see this pi cture. Photoreceptors (eye) • When excited by light the photoreceptor cells hyperpolarize and release less neurotransmitter onto the neurons with which they form synapses. They do not fire action potentials. Excellent overview animation The Sense of Sound • The auditory system for mammals involves several specialized structures found in the ear – pinna collect and funnels sound waves to the auditory canal – tympanic membrane (eardrum), vibrates in response to sound waves. – movements of the tympanic membrane are amplified through a chain of ossicles that conduct the vibrations to the oval window. – Movements of the oval window create pressure waves in the fluid-filled cochlea. animation of the ear QuickTime™ and a TIFF (U ncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (U ncompressed) decompressor are needed to see this picture. The Ear • The basilar membrane running down the center of the cochlea is distorted by sound waves at specific locations that depend on the frequency of the sound. Animation • These distortions cause the bending of hair cells in the organ of Corti, which rests on the basilar membrane. Animation basilar membrane • Receptor potentials in hair cells cause them to release neurotransmitter, which creates action potentials in the auditory nerve Good overview animation Balance and equilibrium Your sense of balance relies on the movement of fluid In the sacule and utricle and semicircular canals • Movement of the head in one plane (static) is monitored by the sacule and the utricle – nerve impulses triggered by movement of otoliths against hair receptor due to gravity Balance animation Balance and equilibrium • Rotation of the head is monitored by movement of fluid in the 3 semicircular cells and their ampulla • Movement of fluid causes cillia on the hair cells in the ampulla to move which will lead to the membrane to depolarize and pass the signal onto the brain – Motion sickness is caused by rapid continuous movement of these fluids Rotation animation Sensory Receptors • Specialized ends of sensory neurons that receive a specific type of stimulus Types of Receptors • General receptors found in the skin Receptors in Skin Touch – Meissner’s copuscles (light touch) – Pacinian corpuscle • deep pressure, vibration, rapid – Ruffini’s corpuscule (continuous pressure) The Sense of Smell • Odorant molecules enter the nasal cavity and bind to specific chemoreceptors called olfactory sensory cells • The binding of these molecules trigger ion channels to open, allowing ions to flow, thus creating the depolarization of the membrane Animation The Sense of Smell The Sense of Smell The Sense of Taste • Chemicals found in foods bind with specific chemoreceptors (taste buds) on the tongue Animation Homeo & NS Unit Exam • 39 M.C. • 4 N.R. • 1 S.A. (12) marks • Lots of Structure and function • Apply knowledge to new situations/conditions