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Integrative Functions

Integrative Functions. Chapter 15. Introduction. There is continuous communication among the brain, spinal cord and the peripheral nervous system. The communication is over tracts and nuclei that link the brain with the rest of the body. Synapses magnify or suppress the sensations

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Integrative Functions

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  1. Integrative Functions Chapter 15

  2. Introduction • There is continuous communication among the brain, spinal cord and the peripheral nervous system. • The communication is over tracts and nuclei that link the brain with the rest of the body. • Synapses • magnify or suppress the sensations • opportunities for divergence

  3. Sensory pathways • Sensory receptors: specialized cells or dendritic processes that monitor conditions in the body or external environment. • When stimulated they pass information the CNS. This is called sensation and arrives in the form of action potentials in an afferent fiber. • Three types of receptors: exteroceptors (ext. env.), proprioceptors (track positions of bones and joints) and interoceptors (int. env.). • Receptors for general senses: nociceptors, thermoceptors, mechanoreceptors & chemoreceptors.

  4. Organization of Sensory Pathway • The posterior column pathway carries fine touch, pressure and proprioceptive sensations. • The axons within the fasciculus gracilis and fasciculus cuneatus (in spinal cord) and relay information to thalamus via medial lemniscus. Before they enter the medial lemniscus, the axons decussate to the opposite side of the brain stem. • The spinothalamic pathway-for poorly localized sensations of touch, pressure, pain and temp. The axons involved decussate in the spinal cord and ascend within the ant. And lat. Spinothalamic tracts to the nuclei in thalamus.

  5. Sensory Pathways • The spinocerebellar pathway, including the posterior and anterior spinocerebellar tracts, carries sensations to the cerebellum concerning the position sof muscles , tendons and joints.

  6. Motor Pathways • Somatic motor pathways always involve an upper motor neuron -whose soma lies in a CNS processing center- and a lower motor neuron-soma is located in motor nucleus of brain stem or spinal cord. • The neurons of the primary motor cortex are pyramidal cells. The pyramidal system provides voluntary muscle control-corticobulbar and corticospinal tracts. • The extrapyramidal system (EPS) consists of several other centers-motor commands for subconscious level processing. Its outputs descend via the vestibulospinal, tectospinal, rubrospinal and reticulospinal tracts.

  7. Motor Pathways • Vestibulospinal tract: carry inforamtion related to maintraining posture and balance. • Tectospinal tracts: change the position of the eyes, head, neck and arms in response to light, noise, sudden movements. • Rubrospinal tracts: carry motor responses to spinal motor neurons. • Reticulospinal tracts: varies according to the region stimulated.

  8. Cerebral Nuclei & Cerebellum • The cerebral nuclei adjust the motor commands issued in other processing centers through synapses in the thalamus. • The cerebellum regulates the activity along both the pyramidal and extrapyramidal motor pathways. The integrative activities performed by neurons in the cerebellar cortex and nuclei are essential for precise control of movements.

  9. The EEG • An EEG is a printed report of the electrical activity of the brain over time. • It can be used to check a variety of clinical conditions.

  10. Higher-Order Functions • These are performed by the cerebral cortex and involve complex interactions among areas of the cerebral cortex and between the cortex and other areas of the brain. • Involve conscious and unconscious information processing. • Are subject to modification and adjustment over time.

  11. Memory • Memory can be classified into short-term or long-term. Short-term memories are short-lived and long-term last much longer. • Long-term memories are further classified into secondary (fade with time) and tertiary (part of consciousness). • Conversion from short-term to long-term memory is memory-consolidation. The amygadoloid body and the hippocampus are essential to memory consolidation.

  12. Consciousness • In deep sleep -slow wave or non-REM sleep-the body relaxes and cerebral activity is low. During rapid eye movement -REM- sleep active dreaming occurs. Periods of REM and deep sleep alternate throughout the night. • Consciousness is determined by interactions between the brain stem and cerebral cortex. One of the most important brain stem components is the reticular activating system (RAS).

  13. Brain Chemistry and Behavior • Changes in the normal balance between two or more neurotransmitters can profoundly alter brain function. • The most important neurotransmitters are: acetylcholine, norepinephrine, GABA, dopamine, serotonin, histamine, substance P, enkephalins and endorphins. • Self-awareness, personality. Characteristic of the brain as an integrated system.

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