Chapter 8 Human Physiology

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. CNS Consists of: Brain Spinal cord Receives input from sensory neurons. Directs activity of motor neurons. Association neurons maintain homeostasis.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Embryonic Development Groove appears in ectoderm to fuse to form neural tube: Neural tube: CNS Forebrain: Telencephalon and diencephalon Midbrain: unchanged Hindbrain :Metencephalon and myelencephalon Part of ectoderm where fusion occurs becomes neural crest. Neural crest: Ganglia of PNS

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Embryonic Development Cavities of brain (ventricles) become filled with CSF. Cavity (central canal) of spinal cord also filled with CSF. CNS composed of gray and white matter. Gray matter found in the cortex and within nuclei. White matter (myelin) consists of axon tracts.

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Cerebrum Telencephalon. Largest portion of brain. Responsible for higher brain functions.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cerebral Cortex Frontal: Precentral gyri: Involved in motor control. Body regions with the greatest number of motor innervation are represented by largest areas of motor cortex.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Parietal Lobe Primary area responsible for perception of somatesthetic sensation. Body regions with highest densities of receptors are represented by largest areas of sensory cortex.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cerebrum Temporal: Interpretation of auditory centers that receive sensory fibers from cochlea. Interpretation and association of auditory and visual information. Occipital: Primary area responsible for vision and coordination of eye movements. Deep insula: Involved in memory.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Electroencephalogram (EEG) Measured synaptic potentials produced in cell bodies and dendrites. Used clinically do diagnose epilepsy and brain death.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. EEG Patterns Alpha: Person is awake, relaxed, with eyes closed. Beta: Produced by visual stimuli and mental activity. Evoked activity. Theta: Common in newborn, not found in healthy adult.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. EEG Patterns Delta: Common during sleep and awake infant. In awake adult indicate brain damage. Sleep: REM (rapid eye movement): Dreams occur. Low-amplitude, high-frequency waves. Similar to beta waves. Non-Rem (resting): High-amplitude, low-frequency waves.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Basal Nuclei Also called basal ganglia. Contains: Corpus striatum: Caudate nucleus Lentiform nucleus: Putman and globus pallidus Masses of gray matter composed of neuronal cell bodies. Function: Control of skeletal muscles. Control of voluntary movements.

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Cerebral Lateralization Cerebral Dominance. Specialization of one hemisphere. Left hemisphere: More adept in language and analytical abilities. Right hemisphere: Limited verbal ability. Most adept at visuospatial tasks.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Language Broca’s area: Involves articulation of speech. In damage to Broca’s area, comprehension of speech in unimpaired. Wernicke’s area: Involves language comprehension. In damage to Wernicke’s area, language comprehension is destroyed, but can still speak. Angular gyrus: Center of integration of auditory, visual, somatesthetic information.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Emotion and Motivation Limbic system: Center for basic emotional drives. Closed circuit between limbic system, thalamus and hypothalamus. Amygdala produces rage and aggression. Amygdala and hypothalamus produce fear. Hypothalamus contains feeding and satiety centers. Hypothalamus and limbic system involved in the regulation of sexual drive and behavior. Hypothalamus and frontal cortex function in goal directed behavior.

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Memory Short-term: Memory of recent events. Medial temporal lobe: consolidates short term into long term memory. Hippocampus is critical component of memory. Acquisition of new information, facts and events requires both the medial temporal lobe and hippocampus.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Memory Long-term: Requires activation of genes, leading to protein synthesis. Growth of dendritic spines. Formation of new synaptic connections. Cerebral cortex stores factual information. Prefrontal lobes involve retrieval of parts of memories from different areas of the brain to use as a whole.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Diencephalon Comprised of the: Thalamus Hypothalamus Pituitary gland

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thalamus Composes the majority of the diencephalon. Forms most of the walls of the 3 rd ventricle. Acts as relay center for all sensory information (except olfactory) to the cerebrum

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hypothalamus Contains neural centers for hunger, thirst, and body temperature. Contributes to the regulation of sleep, wakefulness, emotions and sexual performance. Stimulates hormonal release from anterior pituitary. Produces ADH and oxytocin. Coordinates sympathetic and parasympathetic reflexes.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pituitary Gland Posterior pituitary: Releases ADH and oxytocin. Anterior pituitary: Regulates secretion of hormones of other endocrine glands.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Midbrain Contains: Corpra quadrigemina Cerebral peduncles Substantia nigra Red nucleus Functions: Visual reflexes. Relay center for auditory information. Motor coordination.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hindbrain Metencephalon: Pons: Contains the apneustic and pneumotaxic respiratory centers. Cerebellum: Receives input from proprioceptors. Participates in coordination of movement.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hindbrain Myelencephalon (medulla): All descending and ascending fiber tracts between spinal cord and brain must pass through the medulla. Vasomotor center: Controls autonomic innervation of blood vessels. Cardiac control center: Regulates autonomic nerve control of heart. Regulates respiration with the pons.

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Ascending Spinal Tracts Convey sensory information from cutaneous receptors, proprioceptors and visceral receptors to cerebral cortex.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Descending Spinal Tracts Pyramidal tracts descend directly without synaptic interruption from cerebral cortex to spinal cord. Fine movements. Reticulospinal tracts (extrapyramidal): Gross motor movement.

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Reflex Arc Stimulation of sensory receptors evokes AP that are conducted into spinal cord. Synapses with motor neuron. Conducts impulses to muscle and stimulates a reflex contraction. Brain is not directly involved.