Principles of Human Anatomy and Physiology, 11e1 Chapter 16 Sensory, Motor & Integrative Systems

Principles of Human Anatomy and Physiology, 11e2 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, 11e3 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, 11e4 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, 11e5 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, 11e6 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, 11e7 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, 11e8 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, 11e9 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, 11e10 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, 11e11 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, 11e12 Free nerve endings found around follicles, detects movement of hair Hair Root Plexus

Principles of Human Anatomy and Physiology, 11e13 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, 11e14 Ruffini Corpuscle Found deep in dermis of skin Detect heavy touch, continuous touch, & pressure

Principles of Human Anatomy and Physiology, 11e15 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, 11e16 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, 11e17 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, 11e18 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, 11e19 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, 11e20 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