Chapter 16 Sensory, Motor and Integrative Systems

1. Chapter 16 Sensory, Motor and Integrative Systems

3. Chapter 16 Integration of Nervous System Functions

4. Sensation • Senses: Means by which brain receives information about environment and body • General: Distributed over large part of body • Somatic: Touch, pressure, temperature, proprioception, pain • Visceral: Internal organs and consist mostly of pain and pressure • Special senses: Smell, taste, sight, hearing, balance • Sensation or perception: Conscious awareness of stimuli received by sensory receptors

5. Types of Sensory Receptors • Mechanoreceptors: Compression, bending, stretching of cells • Chemoreceptors: Smell and taste • Thermoreceptors: Temperature • Photoreceptors: Light as vision • Nociceptors: Pain • Exteroreceptors: Associated with skin • Visceroreceptors: Associated with organs • Proprioceptors: Associated with joints, tendons

6. Sensory Nerve Endings • Free nerve endings: Cold receptors and warm • Merkel’s disk: Light touch, superficial pressure • Hair follicle receptor: Light touch, bending of hair • Pacinian corpuscle: Deep cutaneous pressure, vibration and proprioception • Meissner’s corpuscle: Two-point discrimination • Ruffini’s end organ: Continuous touch or pressure • Muscle spindle: Proprioception as to muscle stretch and control of muscle tone • Golgi tendon organ: Important in muscle contraction and tendon stretch proprioception

7. Sensory Nerve Endings in Skin

8. Two-Point Discrimination

9. Tactile Localization The ability to determine which portion of the skin has been touched

10. Muscle Spindle and Golgi Tendon Organ

11. Responses of Sensory Receptors • Receptor: Interaction of stimulus with sensory receptor produces a local potential • Primary: Have axons that conduct action potential in response to receptor potential • Secondary: Have no axons and receptor potentials produced do not result in action potentials but cause release of neurotransmitters • Accommodation or adaptation: Decreased sensitivity to a continued stimulus • Proprioceptors • Tonic: Example is know where little finger is without looking • Phasic: Example is you know where hand is as it moves

12. Sensory Nerve Tracts • Transmit action potentials from periphery to brain • Each pathway involved with specific modalities • First half of word indicates origin, second half indicates termination

13. Spinothalamic System • Conveys cutaneous sensory information to brain • Unable to localize source of stimulus • Divisions • Lateral for pain and temperature • Anterior for light touch, pressure, tickle, itch

14. Dorsal-Column/Medial-Lemniscal System • Carries sensations of • Two-point discrimination • Proprioception • Pressure • Vibration • Tracts • Fasciculus gracilis • Fasciculus cuneatus

15. Spinocerebellar System • Carry proprioceptive information to cerebellum • Actual movements can be monitored and compared to cerebral information representing intended movement • Tracts • Posterior • Anterior

16. Sensory Areas of Cerebral Cortex

17. Pain • Types • Referred: Sensation in one region of body that is not source of stimulus • Phantom: Occurs in people who have appendage amputated or structure removed as tooth • Chronic: Not a response to immediate direct tissue injury

18. Somatic Sensory Cortex

19. Primary Motor Cortex

20. Descending Spinal Pathways • Direct • Control muscle tone and conscious skilled movements • Direct synapse of upper motor neurons of cerebral cortex with lower motor neurons in brainstem or spinal cord • Tracts • Corticospinal • Lateral • Anterior corticobulbar

21. Descending Spinal Pathways • Indirect • Synapse in some intermediate nucleus rather than directly with lower motor neurons • Tracts • Rubrospinal • Vestibulospinal • Reticulospinal

22. Cerebellar Comparator Function

23. Speech • Speech area normally in left cerebral cortex • Wernicke’s area: Sensory speech • Broca’s area: Motor speech • Aphasia: Absent or defective speech or language comprehension

24. Brain Waves and Sleep • Electroencephalogram (EEG): Record of brain’s electrical activity • Brain wave patterns • Alpha: Resting state with eyes closed • Beta: During intense mental activity • Theta: Occur in children but also in adults experiencing frustration or brain disorders • Delta: Occur in deep sleep, infancy, and severe brain disorders

25. Memory • Sensory • Very short-term retention of sensory input • Short-term • Information retained for few seconds to minutes • Long-term • Explicit or declarative • Retention of facts • Accessed by hippocampus and amygdaloid (emotional) • Implicit or procedural • Development of skills as riding a bicycle

26. Long-Term Potentiation

27. General CNS Disorders • Infections • Encephalitis: Inflammation of the brain • Rabies: Viral disease transmitted by bite of infected animal • Multiple sclerosis: Possibly involves autoimmune response to viral infection • Other disorders • Stroke: CVA or cerebrovascular accident caused by hemorrhage, thrombosis, embolism • Aneurysm: Dilation or ballooning of an artery • Alzheimer’s disease: Severe type of dementia • Epilepsy: Group of brain disorders that have seizures

28. Effects of Aging on Nervous System • Gradual decline in sensory and motor function • Reflexes slow • Size and weight of brain decrease • Decreased short-term memory in most people • Long-term memory unaffected or improved