Transcript Chapter 3
Chapter 16 Sensory, Motor & Integrative Systems Principles of Human Anatomy and Physiology, 11e 1 INTRODUCTION • The components of the brain interact to receive sensory input, integrate and store the information, and transmit motor responses. • To accomplish the primary functions of the nervous system there are neural pathways to transmit impulses from receptors to the circuitry of the brain, which manipulates the circuitry to form directives that are transmitted via neural pathways to effectors as a response. Principles of Human Anatomy and Physiology, 11e 2 Sensory Modalities • The classes of sensory modalities are general senses and special senses. – The general senses include both somatic and visceral senses, which provide information about conditions within internal organs. – The special senses include the modalities of smell, taste, vision, hearing, and equilibrium. Principles of Human Anatomy and Physiology, 11e 3 Process of Sensation • Sensory receptors demonstrate selectivity – respond to only one type of stimuli • Events occurring within a sensation – stimulation of the receptor – transduction (conversion) of stimulus • vary in amplitude – generation of impulses when potential reaches threshold – integration of sensory input by the CNS Principles of Human Anatomy and Physiology, 11e 4 Sensory Receptors • Receptor Structure may be simple or complex – General Sensory Receptors (Somatic Receptors) • no structural specializations in free nerve endings that provide us with pain, tickle, itch, temperatures • some structural specializations in receptors for touch, pressure & vibration – Special Sensory Receptors (Special Sense Receptors) • very complex structures---vision, hearing, taste, & smell Principles of Human Anatomy and Physiology, 11e 5 Structural Classification of Receptors • Free nerve endings – bare dendrites – pain, temperature, tickle, itch & light touch • Encapsulated nerve endings – dendrites enclosed in connective tissue capsule – pressure, vibration & deep touch • Separate sensory cells – specialized cells that respond to stimuli – vision, taste, hearing, balance Principles of Human Anatomy and Physiology, 11e 6 Classification by Stimuli Detected • Mechanoreceptors – detect pressure or stretch – touch, pressure, vibration, hearing, proprioception, equilibrium & blood pressure • Thermoreceptors detect temperature • Nociceptors detect damage to tissues • Photoreceptors detect light • Chemoreceptors detect molecules – taste, smell & changes in body fluid chemistry Principles of Human Anatomy and Physiology, 11e 7 Classification by Location • Exteroceptors – near surface of body – receive external stimuli – hearing, vision, smell, taste, touch, pressure, pain, vibration & temperature • Interoceptors – monitors internal environment (BV or viscera) – not conscious except for pain or pressure • Proprioceptors – muscle, tendon, joint & internal ear – senses body position & movement Principles of Human Anatomy and Physiology, 11e 8 Adaptation of Sensory Receptors • Change in sensitivity to long-lasting stimuli – decrease in responsiveness of a receptor • bad smells disappear • very hot water starts to feel only warm • Variability in tendency to adapt: – Rapidly adapting receptors (smell, pressure, touch) • specialized for detecting changes – Slowly adapting receptors (pain, body position) • nerve impulses continue as long as the stimulus persists – Pain is not easily ignored. Principles of Human Anatomy and Physiology, 11e 9 Itch and Tickle • Itch and tickle receptors are free nerve endings. – Tickle is the only sensation that you may not elicit on yourself. Principles of Human Anatomy and Physiology, 11e 10 Meissner’s Corpuscle • Dendrites enclosed in CT in dermal papillae of hairless skin • Discriminative touch & vibration-- rapidly adapting • Generate impulses mainly at onset of a touch Principles of Human Anatomy and Physiology, 11e 11 Hair Root Plexus •Free nerve endings found around follicles, detects movement of hair Principles of Human Anatomy and Physiology, 11e 12 Merkel’s Disc • Flattened dendrites touching cells of stratum basale • Used in discriminative touch (25% of receptors in hands) Principles of Human Anatomy and Physiology, 11e 13 Ruffini Corpuscle • Found deep in dermis of skin • Detect heavy touch, continuous touch, & pressure Principles of Human Anatomy and Physiology, 11e 14 Pacinian Corpuscle • Onion-like connective tissue capsule enclosing a dendrite • Found in subcutaneous tissues & certain viscera • Sensations of pressure or high-frequency vibration Principles of Human Anatomy and Physiology, 11e 15 Referred Pain • Visceral pain that is felt just deep to the skin overlying the stimulated organ or in a surface area far from the organ. • Skin area & organ are served by the same segment of the spinal cord. – Heart attack is felt in skin along left arm since both are supplied by spinal cord segment T1-T5 Principles of Human Anatomy and Physiology, 11e 16 Proprioceptive or Kinesthetic Sense • Awareness of body position & movement – walk or type without looking – estimate weight of objects • Proprioceptors adapt only slightly • Sensory information is sent to cerebellum & cerebral cortex – signals project from muscle, tendon, joint capsules & hair cells in the vestibular apparatus – receptors discussed here include muscle spindles, tendon organs (Golgi tendon organs), and joint kinesthetic receptors (Figure 16.4). Principles of Human Anatomy and Physiology, 11e 17 Muscle Spindles • Specialized intrafusal muscle fibers enclosed in a CT capsule and innervated by gamma motor neurons • Stretching of the muscle stretches the muscle spindles sending sensory information back to the CNS • Spindle sensory fiber monitor changes in muscle length Principles of Human Anatomy and Physiology, 11e 18 Golgi Tendon Organs • Found at junction of tendon & muscle • Consists of an encapsulated bundle of collagen fibers laced with sensory fibers • When the tendon is overly stretched, sensory signals head for the CNS & resulting in the muscle’s relaxation Principles of Human Anatomy and Physiology, 11e 19 Joint Receptors • Ruffini corpuscles – found in joint capsule – respond to pressure • Pacinian corpuscles – found in connective tissue around the joint – respond to acceleration & deceleration of joints Principles of Human Anatomy and Physiology, 11e 20