The central nervous system Chapter 13 Anatomy 32 The Central Nervous System I. T
Norman, Royal, Meteorologist has reference to this Academic Journal, PHwiki organized this Journal The central nervous system Chapter 13 Anatomy 32 The Central Nervous System I. The brain The most amazing organ is the brain. On average it weighs 3.3lbs. It is not yet completely understood in addition to no type of technology has been able to mimic it exactly. Directional term: rostrally (toward snout ex. frontal lobe) in addition to caudally (toward tail, ex. brainstem). The brain is protected by meninges. A. Embryonic development of the brain in addition to basic organization- during embryonic development the brain is first as long as med by several vesicles. As the size increases it folds in to accommodate growth resulting in the structure we know. The vesicle known as the telencephalon (endbrain) develops into the cerebral hemispheres. The dienchephalon (interbrain) as long as ms into the thalamus, hypothalamus, epithalamus, in addition to pituitary gl in addition to . The brain stem containing the midbrain, pons, in addition to medullary oblongata arises from three vesicles in addition to the cerebellum develops from the metencephalon (afterbrain). The wrinkles seen on the brain allow a greater number of neurons to fit in a restricted area.
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The brain has clusters of gray matter called brain nuclei in addition to sheets of gray matter on the surface. The remainder of the brain is white matter or fluid filled areas called ventricles. The spinal cord also has a concentration of gray matter that resembles a butterfly in addition to fluid that flows through it. B. Ventricles of the brain- these cavities are filled with cerebrospinal fluid. It travels around the brain, goes down the spinal cord in addition to returns up to the brain. The septum pellucidum separates the two lateral ventricles. The third ventricles lie in the diencephalon in addition to the connecting cerebral aqueduct lies in the mesenchephalon. Finally the fourth ventricle in addition to central canal lie within the hindbrain (brainstem). The fluid also flows through the meninges, connecting to the subarachnoid space is the fourth ventricle via the lateral in addition to median aperatures. C. The cerebral hemisphere- This area of the brain is the largest; it covers the diencephalon in addition to shows deep or shallow wrinkles. The line that divides the cerebral cortex into a left in addition to right half is the median longitudinal fissure. Posteriorly, the cerebral cortex is separated from the cerebellum by the transverse cerebral fissure. Grooves or furrows are called sulci in addition to the twisted brain ridges are gyri. Deep sulci divide the brain into lobes. The central sulcus lies on the frontal plane between the precentral in addition to postcentral gyrus; it separates the frontal in addition to parietal lobes. The parietals in addition to occipital lobes are separated by the parieto-occipital sulcus. The lateral sulcus (actually a fissure) separates the parietal in addition to temporal lobe. In most people the left hemisphere has control of language, math, in addition to logic; it deals with the details of the big picture. The right hemisphere has control of visual-spatial skills, intuition, art in addition to music skills, in addition to emotions; it deals with the big picture. The division of control may be more prevalent in males. Both hemisphere communicate via connecting fiber tracts called commissures.
1. Cerebral cortex-composed of six layers of gray matter (primarily interneurons), it controls consciousness in addition to voluntary movement. Brodmanns structural areas map out different regions of the brain. Studies on brain activity have revealed functional regions of the cerebral cortex in the areas of motor, sensory, in addition to association.
MOTOR AREA: a. Primary motor cortex- also called somatic motor area is along the precentral gyrus in addition to contains pyramidal cells. These as long as m tracts that reach motor neurons, they control precise voluntary motor movements. The axons project in a contralateral path (left brain controls right side of body). Areas that control complex skilled movement contain a larger amount of pyramidal cells. b. Premotor cortex- Lies anterior to precentral gyrus. It controls even more complex movements than the primary motor cortex because it integrates highly processed sensory in as long as mation received from other brain areas. It controls voluntary movement based on spatial arrangement in as long as mation in addition to is involved in planning movements. c. Brocas area- Lies in the left hemisphere (language dominant), it controls speech movements, produces mental images of sounds to be spoken, in addition to may also story short-term memory. Its corresponding side on the right controls the spoken emotional overtones.
SENSORY AREA: a. Primary somatosensory cortex- lies along postcentral gyrus, its involved with conscious awareness of somatic senses. It is capable of spatial discrimination of sensory stimulus, the in as long as mation travels contralaterally. b. Somatosensory association area- lies posterior to primary somatosensory cortex. It integrates sensory input as long as comprehensive underst in addition to ing by relating it to past experience (ex. Feeling a object in addition to guess what it is without seeing it) c. Primary visual cortex- the largest sensory area lies in the medial part of occipital lobe. It receives all visual in as long as mation sent by the eye but has low level of processing, the in as long as mation is sent to opposite sides d. Visual association area- surrouds the primary visual cortex in addition to continues to process in as long as mation obtained by this area. Multiple visual areas exists throughout that brain that allow the in as long as mation to travel anteriorly, one pathway process recognition in addition to the other spatial orientation.
e. Auditory areas- includes the primary auditory cortex that controls conscious awareness of sound received by receptors in the ear. The auditory association area evaluates/ recognizes a sound in addition to stores memory of sound, a specialized area called Wernickes area recognizes spoken words. f. Gustatory cortex- involved in conscious awareness of taste, located in the tongue region of the homunculus. g. Vestibular cortex- involved in conscious awareness of balance, it is found in posterior part of insula. h. Olfactory cortex- involved in conscious awareness of smell, processes by the piri as long as m plate, olfactory tract, in addition to olfactory bulb. A region of the frontal cortex recognizes in addition to differentiates odors. ASSOCIATION AREAS- all areas of the cortex that are not motor or sensory, may also be called higher order processing areas. a. Prefrontal cortex- frontal lobe region anterior to motor areas, its function separates humans from other animals. It is involved in thought, perception, in addition to recall (cognition). It is essential as long as judgment, critical thinking, planning, socializing, in addition to some aspects of emotion. The farther rostrally, the more complex the function. b. General interpretation area- located in the postlateral cerebral cortex, it integrates sensory in as long as mation. Not well understood. c. Language area- large area in left cerebral hemisphere has five identified areas: 1- Brocas, 2- Wernickes, 3-speech comprehension, 4-coordination of auditory in addition to visual aspects of language, 5-word articulation in addition to recognition d. Insula- not well understood, apparently functions in language, balance, visceral functions, behavior as related to cardiovascular activity.
Body map along the Precentral in addition to Postcental Gyrus
2. Cerebral White Matter- These areas are composed of myelinated fibers that as long as m large tracts in addition to connect the two hemispheres. This section lies beneath the gray matter of the cerebral cortex. a. Commisures- commissural fibers connect related gray matter areas between the two hemispheres (run horizontally). These include the corpus callosum. b. Association fibers- horizontal fibers that connect different areas of the same hemisphere. c . Projection fibers- vertical fibers these take sensory in as long as mation to the appropriate area in the cerebral cortex in addition to carry away motor instructions. The as long as m the internal capsule in addition to corona radiate.
3. Basal Nuclei- neural calculators that control movement by cooperating with the cerebral cortex in addition to can estimate time. Their exact function is still unknown but it is know that they send their output to the motor cortex. They include the caudate, the lenti as long as m, the amygdala. D. The diencephalons- surrounded by the cerebral hemisphere it as long as ms the central core of the as long as ebrain. Its structures are paired in addition to composed of gray matter.
PET scan of the brain of an Alzheimers patient. Blue in addition to purple areas show parts of the brain with affected neural activity. Tissue is degenerated as it is invaded by plaques. Patients suffer from dementia in addition to other mental ailments. Infant with spina bifida cystica showing lumbar myelomeningocele (cyst of the meninges)
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