BIOL 2401 DR. WELCH CHAPTER 16: SENSORY, MOTOR, & INTEGRATIVE SYSTEM I. Sensation conscious or subconscious awareness of internal & external changes. Define perception. Primary function of. Why isn t blood pressure consciously perceived? A. Sensory Modalities unique type of sensation (ex. Touch, pain, vision, hearing, etc.); sensory neuron attached conducts only the specific modality assigned to the receptor attached. Why? Grouped into 2 classes: 1. General Senses = somatic & visceral a. Somatic tactile touch, thermal, pain, & proprioception. Refer to p. 610-615. Define proprioception. b. Visceral pertains to internal organs. List examples. 2. Special Senses - List the 5 special senses. B. Process of Sensation 1. Stimulation of Sensory Receptor must occur in receptive field. 2. Transduction of Stimulus sensory neuron converts energy in a stimulus into graded potential which vary in amplitude. See Section 12.3. Each sensory receptor exhibits selectivity. 3. Generation of Nerve Impulse graded potential threshold CNS (first-order neuron) 4. Integration of Sensory Input specific region of CNS receives & integrates sensory nerve impulse. a. Cerebral Cortex conscious perception; if it doesn t then no consciousness of sensation. C. Sensory Receptors classed by microscopic structure, location, & type of stimulus detected. 1. Microscopic Structure Give examples of the following. Refer to Fig. 16.1 p. 608 & Table 16.1 p. 609 a. Free Nerve Ending (FNE) bare dendrites; pain, temp, itch & tickle (some touch) p. b. Encapsulated Nerve Endings vibration, pressure & some touch c. Separate Cells special senses 2. Types of Potential in response to stimuli amplitude of both vary with intensity of stimulus a. Generator meet threshold Action potential (FNE, encapsulated NE & olfactory receptors) b. Receptor synaptic vesicles release NT into synaptic cleft (Separate cells) 3. Location of Receptors a. Exteroceptors located on or near integumentary; detect external stimulus. List examples. b. Interoceptors located in b.v., viscera, muscles, & nervous system; detects internal environment. Usually not perceived. c. Proprioceptors located in muscle, tendons, joints & inner ear; provide information about body position, muscle length & tension, as well as position & movement of joints. Define kinesthesia & weight discrimination. 4. Type of Stimulus Detected Define adaptation. Give examples of rapidly & slowly adapting receptors. a. Mechanoreceptors deformation, stretch, binding of cells. b. Thermoreceptors temp change c. Nociceptors List types of pain & localization. d. Photoreceptors detects light; retina e. Chemoreceptors taste, smell, & body fluids f. Osmoreceptors sense osmotic pressure. Define osmotic pressure & review osmosis. II. Somatic Sensations distributed unevenly; highest density located in tip of tongue, lips, & fingertips. Cutaneous sensation. Refer to Fig. 16.2 p 615 A. Tactile mechanoreceptors in skin or subq; Encapsulated attached to type A fiber. 1. Touch 2 types of rapidly adapting & 2 types of slow adapting receptors. a. Meissner Corpuscles (rapid) attached to large, myelinated A fibers; located in dermal papillae of hairless skin; onset of touch. List locations where they are abundant. b. Hair Root Plexuses (rapid) FNE attached to large, myelinated A fibers activated by slight movement of hair follicles. c. Merkel Discs/ Type I (slow) located in ; plentiful in fingertips, hands, lips, & external genitalia. d. Ruffini Corpuscles/ Type II deep in dermis, ligaments & tendons. Present in and abundant in. Most sensitive to. 1
2. Pressure sustained over larger area in deeper tissues. 3. Vibration rapidly repetitive signals. a. Meissner Corpuscles low ƒ b Pacinian Corpuscles high ƒ 4. Itch FNE attached to type C fiber; bradykinins or antigens in mosquito saliva = vasodilation d/t inflammatory response. 5. Tickle FNE attached to type C fiber. Why is it that in most cases someone else can tickle you but you can t? B. Thermal FNE detect temperature 1. Cold Receptors located in ; Attached to medium, myelinated type A fibers (Activated 50-105 o F) 2. Warm Receptors not as abundant as cold receptors; located in attached to small unmyelinated C fibers. (Activate 90-118 o F) C. Pain protective function; signals noxious conditions which can be chemical, mechanical or thermal. What 3 chemicals can stimulate nociceptors? Why does pain persist even after cause has been removed? Temperature elicits pain between 10 o C -48 o C. What is referred pain vs. phantom limb sensation? D. Proprioception knowing where your joints are in space. 3 types: 1. Muscle Spindle (slow) skeletal muscle; detects muscle length d/t stretch. Define muscle tone. a. Intrafusal Muscle Fiber anchors the spindle; aligned parallel. Sensory receptor. Fine motor control have more muscle spindles than more forceful muscles. What is the only skeletal muscle to lack muscle spindles? Review stretch reflex. i. Cerebral Cortex allows conscious perception of limb position & movement. ii. Cerebellum used to coordinate muscle contractions. b. Gamma Motor Neurons motor neuron near both ends of the intrafusal fibers & adjusts the tension in the muscle spindle to length changes. What is the function of this arrangement? c. Extrafusal Motor Fiber large type A fiber supplies α motor neuron 2. Tendon Organs protect muscle from excessive stretch. Review GTO reflex. 3. Joint Kinesthesia Receptors located within & around articular capsules of synovial joints. Adjust reflex inhibition of adjacent muscles when excessive strain is placed on the joint. III. Somatic Sensory (Ascending) Pathways PNS CNS. Consists of 3 neurons First-Order Neuron somatic sensory receptor (spinal & cranial nerves) brain stem or spinal cord. Second-Order Neuron brain stem/ spinal cord thalamus (major relay station) Third-Order Neuron thalamus primary somatosensory area (post-central gyrus) of cerebral cortex. 3 general pathways: Define decussation. A. PCML (posterior/ dorsal) aka Posterior Column-Medial Meniscus - Touch, pressure, & vibration Lower Limbs & Lower Truck 3 rd Thalamus Midbrain (Medial Lemniscus) 2 nd Medulla (Gracilis Nucleus) Medulla (Gracilis Nucleus) 1 st Spinal Cord - Gracilis Fasciculus Upper Limbs & Upper Truck, Neck & Posterior Head 3 rd Thalamus Midbrain (Medial Lemniscus) 2 nd Medulla (Gracilis cuneate) Medulla (Gracilis cuneate) 1 st Spinal Cord - Cuneate Fasciculus 2
B. Anterolateral (Spinothalamic) pain, temp, itch & tickle. Limbs, Truck, Neck & Posterior Head 3 rd Thalamus Midbrain Medulla 2 nd Anterolateral (Spinothalamic) Tract Spinal Cord Posterior Horn 1 st Spinal Cord Posterior Horn C. Trigeminothalamic Pathway tactile, thermal, pain & proprioception Face, Nasal Cavity, Oral Cavity & Teeth 3 rd Thalamus Midbrain 2 nd Medulla & Pons Medulla & Pons 1 st Trigeminal Ganglion D. Anterior & Posterior Spinocerebellar Pathway Proprioception allowing unconscious coordinated, smooth & refined movements; maintains posture & balance. Doesn t decussate. What causes syphilis and results if untreated? IV. Somatic Motor (Descending) Pathways CNS PNS. Consists of different types of neurons: A. Lower Motor Neurons () cell bodies in brain stem & spinal cord goes thru spinal/ cranial nerves to innervate skeletal muscle. Spinal nerve limbs & trunk (p. 506-511); cranial nerves face & head. (p. 564) 1. Local Circuit Neurons interneurons; help coordinate rhythmic activity in specific muscle groups. Give an example. B. Upper Motor Neuron (UMN) from cerebral cortex are essential for movements. From brain stem (red nucleus, vestibular nucleus, superior colliculus & reticular formation) regulates muscle tone, controls posture & helps with balance & orientation of head & body. 1. Basal Nuclei Neurons helps initiate & terminate movements, suppresses unwanted movements & establishes normal tone. 2. Cerebellar Neurons Monitors differences between intended & actual movements, reduces errors, coordinates movement; helps maintain balance & posture. Complete the following: Lesion To: Type paralysis Reflexes Effected Muscle Tone Side Effected Pathological Reflex UMN (cerebral cortex) C. Named Pathways - UMN to in 2 descending pathways Direct & Indirect. Innervate skeletal muscle. 1. Direct Motor (Pyramidal) Pathways to directly from cerebral cortex. a. Corticospinal Pathways voluntary muscles of limbs & trunk i. Lateral Corticospinal Pathway (90%) muscles of distal limbs; responsible for precise, agile, & highly skilled movements of hands & feet. List examples. Neuron Right Side Left Side UMN Cerebral Cortex (Precentral Gyrus) Midbrain (Cerebral Peduncle) Medulla (Pyramid) 90% Medulla (Pyramid) Spinal Cord (Lateral Corticospinal Tract) Spinal Cord (Anterior Horn) 3
ii. Anterior Corticospinal Pathway (10%) controls movement of trunk & proximal limbs. Neuron Right Side Left Side UMN Cerebral Cortex (Precentral Gyrus) Midbrain (Cerebral Peduncle) Medulla (Pyramid) 10% Spinal Cord (Anterior Corticospinal Tract) Spinal Cord (Anterior Horn) Spinal Cord (Anterior Horn) b. Corticobulbar Pathway muscles of head; some decussate. Terminate in nuclei of 9 CN in brain stem: CN III-VII & IX-XII. List types of movements. Discuss cause and effect of ALS. 2. Indirect Motor Pathways to from centers in basal nuclei, cerebellum, & cerebral cortex. 4 pathways: a. Rubrospinal (red nucleus) to contralateral muscle of distal pars of UE; precise movements. b. Tectospinal (superior colliculus) to contralateral head, eyes, & trunk; reflex response to visual/auditory stimulus. c. Vestibulospinal (vestibular nucleus) to ipsilateral trunk & proximal limbs; maintains posture & balance in response to head movements. D. M&L Reticulospinal (reticular formation) to ipsilateral trunk & proximal limbs; maintains posture & muscle tone. D. Roles of Basal Nuclei (BN) influences movement through UMN with cerebellum 1. Initiation & termination of movements. 2. Suppresses unwanted movements. 3. Muscle tone. 4. Influences sensory, limbic, cognitive, & linguistic functions; ex. Attention, memory, & planning. Define all disorders of BN. E. Movement by Cerebellum refer to Fig. 15.2 p. 626 1. Monitoring intention of movement. 2. Monitoring actual movement associated with anterior & posterior spinocerebellar tracts, vestibular apparatus & eyes. 3. Comparing command signals with sensory information 4. Sending out corrective feedback which decrease errors & learning of new skills. V. Integrative Functions of the Cerebrum the processing of sensory information by analyzing, storing it and making decisions. A. Sleep & Wakefulness Define circadian rhythm. Established by hypothalamus. Cerebral cortex very active during wakefulness. How does the NS transition between the 2 states? 1. Arousal awakening from sleep = RAS stimulation which leads to consciousness; stimulation d/t pain, touch & pressure, movements of limbs, bright light or buzz of alarm clock. Why is it that people that die in house fire usually succumb to smoke inhalation? 2. Sleep (7-8 hr period) state of altered consciousness or partial unconsciousness. List sleep deprivation impairment. a. NREM 4 gradual stages; governed by preoptic area of hypothalamus, basal forebrain & medulla i. Stage 1 wakefulness sleep (1-7 min); not sleeping ii. Stage 2 light sleep iii. Stage 3 moderately deep sleep; temperature & BP decrease (20 min) iv. Stage 4 deep sleep; sleep walking occurs in this stage. b. REM 3 to 5 episodes; eyes move rapidly back & forth; occurs approx. Every 90 min. = total 90-120 min in adults. Most dreams occur. Why do infants have longer REM time than adults? i. Involves pons & midbrain; most somatic motor neurons are inhibited. Which ones are not? Ii. ANS increased by parasympathetic division of ANS. How can you tell if erectile dysfunction is psychological? B. Learning & Memory Define plasticity. 1. Learning ability to acquire new information or skills through instruction or experience. 4
2. Memory process of storing & retrieving learned information; includes frontal, parietal, occipital, & temporal lobes; parts of limbic system esp. & ; & diencephalon. Define the following & give examples. a. Immediate memory b. Short-term memory c. Long-term memory What is the difference between anterograde & retrograde amnesia? i. Memory consolidation ii. Only 1% of all information is stored as long term. iii. Anesthesia, coma, ECT and ischemia disrupt retention iv. Long-term potentiation Define. Occurs in hippocampus. Review all Clinical Connections, Disorders: Homeostatic Imbalances, & Medical Terminology (back of chapter). This is only a general outline. There may be material that has been discussed in lecture that is not included in this outline and there may be material on this outline that has not been discussed in lecture. Any material discussed in lecture or listed in this outline is "fair game" for the test. 5