Integration of

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Chapter 14

• Integration of
• Nervous 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
• Merkels disk Light touch, superficial pressure
• Hair follicle receptor Light touch, bending of
  hair
• Pacinian corpuscle Deep cutaneous pressure,
  vibration and proprioception
• Meissners corpuscle Two-point discrimination
• Ruffinis 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
• Wernickes area Sensory speech
• Brocas area Motor speech
• Aphasia Absent or defective speech or language
  comprehension

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Brain Waves and Sleep

• Electroencephalogram (EEG) Record of brains
  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
• Alzheimers 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