Sensory, Motor and Integrative Systems Chapter 16 Sensory, Motor and Integrative Systems

Nervous System Functions Chapter 16 Integration of Nervous System Functions

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

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

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

Sensory Nerve Endings in Skin

Two-Point Discrimination

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

Muscle Spindle and Golgi Tendon Organ

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

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

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

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

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

Sensory Areas of Cerebral Cortex

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

Somatic Sensory Cortex

Primary Motor Cortex

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

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

Cerebellar Comparator Function

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

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

Memory Sensory Short-term Long-term 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

Long-Term Potentiation

General CNS Disorders Infections Other disorders 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

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