University:
Glendale Community College
Course:
BIO160 | Introduction to Human Anatomy and Physiology
Academic year:

2022
Views:

4

Pages:

28
Author:

Madilyn Huerta

Functions of the Lobes of the Cerebrum • Frontal Lobe: voluntary motor functions and areas for motivation, planning, memory, emotion, social judgment and aggression. • Parietal Lobe: sensory reception and integration. • Occipital Lobe: the visual center of brain and creates a visual map of the world. • Temporal Lobe: contains areas for hearing, smell, learning, memory, visual recognition and emotional behavior. • Insula functions are still being studied. Accidental Lobotomy of Phineas Gage • Accidental destruction of ventromedial region of both frontal lobes changed his personality from a quiet, reliable, hard-working person to an irreverent, profane and fitful person. • Neuroscientists believe that planning, moral judgement, and emotional control are functions of the prefrontal cortex of the frontal lobe. Phineas Gage’s life mask and skull Warren Anatomical Museum Phineas Gage with the tamping rod that was driven through his head in an accident in 1848 Digital renderings of Gage's skull showing the trajectory of the rod and the fiber pathways in the left hemisphere. Connectogram of a healthy brain Connectogram of Phineas Gage's brain “Connectograms are circular diagrams depicting the brain's major white matter tracts. In these diagrams, the major brain regions - the frontal lobe, insula, limbic system, temporal lobe, parietal lobe, occipital lobe, brain stem and cerebellum - are color-coded and arranged on the outer ring of the diagram, according to their position from the front. Cerebral White Matter • White Matter of the brain consists of myelinated axons. • Most of the volume of the cerebrum is composed of “tracts” of axons (white matter). • Types of tracts: – projection tracts extend vertically between brain and spinal cord. – commissural tracts (like the corpus callosum) cross from one cerebral hemisphere to the other – association tracts connect lobes of each hemisphere to each other Tracts of Cerebral White Matter Cerebral Cortex Gray Matter • Gray Matter of cerebral cortex is a 3 mm thick layer of neurons. • Cortex is primarily composed of 2 types of cells in 6 layers: – stellate cells have dendrites projecting in all directions – pyramidal cells have triangular-shaped somas (pyramidal) and have an axon that passes out of one layer into another area of the brain basic functional areas Functional Regions of Cerebral Cortex Somesthetic Sensation • Sensory signals travel up tracts in the spinal cord to the Somatosensory Area which is in the postcentral gyrus of the cerebral hemispheres. Sensory Homunculus • The area of the postcentral gyrus of the cerebral cortex dedicated to the sensations of various body parts is proportional to how sensitive that part of the body is. Sensory Association Areas • Association areas interpret sensory information. • Somesthetic Association Area (parietal lobe) – position of limbs, location of touch or pain, and shape, weight and texture of an object • Visual Association Area (occipital and temporal lobes) – identify the things we see – faces are recognized in temporal lobe • Auditory Association Area (temporal lobe) – remember the name of a song or identify a person by his/her voice Special Senses • Special senses are located in the head and employ very specialized sensory receptors. • Special Senses include: – – – – – Vision Equilibrium Hearing (auditory) Taste (gustatory) Smell (olfactory) • These senses are projected to specialized regions of the brain. Motor Control • Intention to contract a skeletal muscle begins in the motor association area of frontal lobes and is relayed to the Primary Motor Area. • The Primary Motor Area consists of Pyramidal Cells in the precentral gyrus. • Signals are sent out through the spinal cord to muscles of contralateral (opposite) side. Motor Homunculus • The area of the cortex dedicated to the motor control of various body parts is proportional to the number of motor units in a region. Language • Aphasia is a language deficit resulting from lesions in Wernicke’s and Broca’s areas (usually in the left hemisphere) • Lesion to Broca’s area results in nonfluent aphasia – slow speech, difficulty choosing words, sparse vocabulary • Lesions on other side of brain opposite of Broca’s area result in aprosody – flat, emotionless speech. • Lesion to Wernicke’s area results in fluent aphasia – normal speech but excessively wordy and makes little sense • Lesion opposite Wernicke’s area causes difficulty recognizing the emotional content of another person’s speech (for example, not getting a joke) • Other deficits: speech and understanding speech are normal but text and pictures make no sense Language Centers People with primary visual agnosia may have one or several impairments in visual recognition without impairment of intelligence, motivation, and/or attention. Vision is almost always intact and the mind is clear. Some affected individuals do not have the ability to recognize familiar objects. They can see objects, but are unable to identify them by sight. However, objects may be identified by touch, sound, and/or smell. For example, affected individuals may not be able to identify a set of keys by sight, but can identify them upon holding them in their hands. Primary visual agnosia results from damage to the parietal and temporal lobes of the brain. Symptoms develop due to the inability to retrieve information from those damaged areas that are associated with visual memory. Lesions may occur as a result of traumatic brain injury, stroke, tumor, or overexposure to dangerous environmental toxins (e.g., carbon monoxide poisoning). In some cases, the cause of the brain damage may not be known. Symptoms may vary, according to the area of the brain that is affected. Limbic System • Loop of cortical structures composed of the amygdala, hippocampus, fornix and cingulate gyrus • Important in emotional processing and in memory. Much still poorly understood. Cerebral Lateralization • Left hemisphere is more categorical – specialized for spoken and written language, sequential and analytical reasoning (math and science), analyze data in linear way • Right hemisphere is more representational – perceives information more holistically, perception of spatial relationships, pattern, comparison of special senses, imagination and insight, music and artistic skill • Highly correlated with handedness – 91% of right-handed people have a categorical left hemisphere A 33-year old male who went to the hospital complaining of a headache was found to have 12 nails embedded in his skull from a suicide attempt with a nail gun. Some of the nails were 1.5” long and others were 2” long and surgeons removed them with needle-nose pliers and a drill. The man at first told doctors he had a nail gun accident, but later admitted it was a suicide attempt while under the influence of methamphetamine. Journal of Neurosurgery April, 2006