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Anatomy and Physiology, Sixth Edition

Rod R. SeeleyIdaho State UniversityTrent D. StephensIdaho State UniversityPhilip TatePhoenix College

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

*See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.

Chapter 14Chapter 14

Lecture OutlineLecture Outline**

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Chapter 14

Integration ofNervous System Functions

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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

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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

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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

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Sensory Nerve Endings in Skin

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Two-Point Discrimination

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Muscle Spindle and Golgi Tendon Organ

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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

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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

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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

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Dorsal-Column/Medial-Lemniscal System

• Carries sensations of– Two-point

discrimination

– Proprioception

– Pressure

– Vibration

• Tracts– Fasciculus gracilis

– Fasciculus cuneatus

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Spinocerebellar System

• Carry proprioceptive information to cerebellum

• Actual movements can be monitored and compared to cerebral information representing intended movement

• Tracts– Posterior

– Anterior

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Sensory Areas of Cerebral Cortex

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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

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Somatic Sensory Cortex

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Primary Motor Cortex

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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

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Descending Spinal Pathways

• Indirect– Synapse in some

intermediate nucleus rather than directly with lower motor neurons

– Tracts• Rubrospinal

• Vestibulospinal

• Reticulospinal

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Cerebellar Comparator Function

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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

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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

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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

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Long-Term Potentiation

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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

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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