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Ch. 13 Central Nervous System
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Introduction The CNS contains: Brain - encased by cranium
Spinal cord - encased by vertebrae
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Coverings of the brain and spinal cord
Meninges membranes between bone and soft tissue Dura mater – outermost, contains blood vessels Forms periostium of skull bones Forms partitions between lobes of brain and sinuses provides resistance to pathogens Prevents cerebral spinal fluid leaks Arachnoid mater – middle. Thin, avascular Pia mater – innermost, vascular, thin Attached to brain and spinal cord surface. Spaces Epidural-between dura mater and covering of spinal cord. Subdural – between dura mater/arachnoid mater. Contains serous fluid Subarachnoid – between arachnoid and pia. Contains cerebrospinal fluid Purpose – supportive cushion. Headache – dilated vessels in meninges. Meningitis – inflammation of meninges caused by bacteria/virus. Produces fever, headache, and if untreated, death.
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Structure of the Spinal cord
Description and location Structure 31 Segments with a pair of spinal nerves in each segment 8 cervical 12 thoracic 5 lumbar 5 sacral CX - in coccyx Cervical enlargement Lumbar enlargement Plexus - clump Grooves Anterior media fissure Posterior median sulcus White matter – myelinated fibers Gray mater - cell bodies and dendrites of interneurons. (butterfly shaped) Cerebrospinal pressure is measured by needle inserted between lumbar vertebrae in sub arachnoid space. Sample is checked for abnormal constituents.
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Function of the spinal cord
Functions Transmit impulses House spinal reflexes Ascending (sensory) descending tracts (motor) Names of tracts – identify origin and termination of fibers in tract (ex. Spinothalamic tract)
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The myteries of the human brain
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The brain Introduction - largest part of the nervous system
100 billion multipolar neurons. Divisions Cerebrum – largest/higher mental functions Diencephalon – process sensory input Cerebellum-coordinates muscular activity Brainstem-coordinates/regulates visceral activities
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The cerebrum The largest part of the brain
Surface of the brain is marked by convolutions, sulci, fissures. Lobes of the brain are named according to the bones they underlie. 2 hemispheres connected by Corpus callosum Convolutions, sulci, fissures Lobes Frontal Parietal Temporal Occipital Cerebral cortex - thin layer of gray mater - 75% of cell bodies
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Functions of the cerebrum
Higher brain functions Interpretation of sensory input Initiating voluntary muscular movement Memory Integrating information for reasoning Consciousness Language Emotions
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Functional regions of cerebral cortex
Primary motor area-frontal lobes, anterior wall Broca’s area coordinates muscular activity for speech Frontal eye field - controls eye and eye lid movement Sensory areas - interpret sensory input, produce feelings/sensations Association areas interpret sensory impulse, reasoning, judgment, emotions, story memory Cross-over - right side controls left side of body, etc. Interpretive areas-located where lobes come together - higher intellectual processes. Damage Occipital lob - sight and images Temporal lobe - recent memories - inability to form long term memories.
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Hemisphere dominance Both cerebral hemispheres receive/analyze
Most people exhibit dominance of left or right hemispheres. Left hemisphere is dominant in 90% Left hemisphere dominance usually results in being right handed, etc. Non dominant hemisphere specialize in nonverbal function, emotion control/intuitive thinking
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Ventricles and cerebrospinal fluid
Description - series of connective cavities containing cerebrospinal fluid. Continuous with the spinal cord Choroid plexuses Specialized capillaries that Secrete cerebrospinal fluid Comes from lateral ventricles Cerebrospinal fluid Nutritive Protective Pressure - normally constant. Infection /tumor can increase pressure - causes damage
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Diencephalon Location - above brain stem Contains:
thalamus -sorts and directs sensory information - filters non-essential information Hypothalamus - maintains homeostasis/ linked to endocrine system Optic tracts and chasmas - connect sense of sight Infundibulum - attachment for pituitary Pituitary gland - certain hormone production. Pineal gland - puts you to sleep Limbic system - controls emotional experience and expression Guides behavior that increases chance of survival.
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Consists of Midbrain- conveys impulses to and from other parts of the brain Reflex centers Pons-between midbrain and medulla oblongata Regulates rate and depth of breathing Transmits impulses between brain and spinal cord Medulla oblongata - transmits ascending and descending impulses Controls visceral functions - cardiac center - heart rate, blood pressure control, respiratory center, cough and vomiting centers, sneezing Reticular formation-wakes up the cerebral cortex Decreased activity results in sleep, increased - wakefulness Filters sensory impulses If damaged, can’t wake from a coma. Brainstem
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Cerebellum Made of two hemispheres connected in the middle.
Cerebellar cortex - gray matter Communicates with others parts of cns. Integrates sensory information about position of body parts and coordinates skeletal muscle activity to maintain posture.
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language Ability to speak/write words and ability to understand spoken/written words. Speech center – areas in frontal, parietal, temporal lobes. Left cerebral hemisphere contains speech centers in 90% of population Aphasias - damage to speech centers - can’t speak.
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Emotions Limbic system -known as the “emotional brain”
Medial surface of cerebrum and region called hippocampus Connection to olfactory sense
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Memory Cortex stores and retrieves short and long term memory
Repetition is the key to transferring information from short to long term memory If you don’t use it you lose it. Closely connected to limbic system Forgetting is the atrophy of a neural connection that was created when learning took place.
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