The Lobes Of The Brain Biology Essay

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Frontal Lobe- the largest lobe, located beneath the frontal bone of the skull and rests on orbit of the eye in the anterior cranial fossa of the skull. The major functions ascribed to the frontal lobe are conscious thought, abstract thinking, information storage or memory, and the initiation of motor activity. The gyrus immediately in front of the central sulcus, the precentral gyrus, has been identified as the primary motor are of the cerebrum. Secondary and supplementary motors areas also have been identified in the frontal lobe. The frontal eye fields have been identified for the initiation of conjugate, voluntary deviation of the eyes to the opposite sides. The prefrontal are of the frontal lobe is believed to be concerned with affective reactions to the present based on experience. The broca's area, which is located in the left hemisphere and is critical for motor control of speech. The fontal lobe is also responsible in the large part for a person's affect, judgment, personality and inhibitions.

Parietal Lobe- are located beneath the parietal bones of the skull within the middle cranial fossa. The parietal lobes includes the primary somatosensory area of the brain which general sensory information from the opposite side of the body is being processed(right-left orientation), also functions as localization of sensory information to the body surface and secondary somatosensory area that is thought to be involved in less discriminative aspects of sensation. Much of the parietal cortex constitutes the somesthetic association cortex which allows familiar objects to be recognized by holding or touching them, largely based on experience. Other functions of the parietal lobe include information processing, spatial orientation, perception of stimuli, pain and touch sensation.

Temporal Lobe- is located in the middle fossa beneath the temporal bone. The major function of the temporal lobe is localized in the primary auditory area and plays a role in memory of sound and music. The auditory association cortex of the temporal lobe is important in language function. The hippocampus is located medially in the temporal lobe which is involved in emotion and sexual behavior. Also hippocampus is responsible for processing recent memory and formation of long-term memory.

Occipital Lobe- is wedge shaped and extends from parieto-occipital fissure. The occipital lobe contains the primary visual cortex for the perception and interpretation of visual input from the eyes. The lateral surface of the occipital lobe is the visual association cortex, which stores information from previous visual experiences.

Limbic lobe- is a ring of cortical tissue that is mostly composed of the cingulated gyrus and the parahippocampal gyri of the temporal lobe; it is partially hidden by the brain stem. This system is important in emotional responses, memory, and fundamental behaviors that ensure the survival of the species.

How does the aging process impact the neurological system?

Structural and Physiologic changes

A loss of neurons occurs, leading to decrease in the number of synapse and neurotransmitters. This result in slowed nerved conduction, repetitive movements, tremors and response time.

Brain weight is decreased and the ventricle size increases to maintain cranial volume.

Cerebral blood flow and metabolism are reduced, leading to slower mental functions.

Temperature regulation becomes less efficient, leading to impairment in ability to adapt to environmental temperature.

Decrease in oxygen supply, changes in basal ganglia by vascular changes, leading to changes in gait and ambulation and diminished kinesthetic sense.

Motor Alterations

Decrease in muscle bulk with atrophy, leading to decrease in strength and agility and difficulty maintaining balance.

Decrease in electrical activity, leading to decrease in speed and intensity of neuronal reflexes.

Sensory Alterations

Decreased in sensory receptors caused by degenerative changes and involution of fine corpuscles of the nerve endings. This results in diminished sense of touch, inability to localize stimuli and decrease in appreciation of touch, temperature and peripheral vibrations.

Decreased peripheral vision and constricted visual field occur due to degeneration of visual pathways, resulting in disorientation, especially at night where there is little or no light in the room.

There is atrophy of taste buds leading to malnutrition or weight loss.

Degeneration and loss of fiber in olfactory bulb resulting to diminished sense of smell.

Nerve cells in the vestibular system of the inner ear, cerebellum degenerate resulting in poor ability to maintain balance and widened gait.

Alteration in Reflexes

Decrease in deep tendon reflexes

Decrease in sensory conduction velocity as result of myelin sheath degeneration leading to sluggish reflexes and slowing of reaction time.

Alteration on Reticular Formation

Modification of hypothalamic function, reduction in stage IV sleep leading to increase frequency of spontaneous awakening together with tiredness, interrupted sleep and insomnia.

Alteration in Autonomic Nervous System

Morphologic features of ganglia, slowing of ANS responses resulting in orthostatic hypertension and systolic hypertension.

Compare and contrast the sympathetic and parasympathetic nervous systems in terms of function.

Similarities: The sympathetic and parasympathetic systems are a part of the peripheral nervous system. They are both parts of the autonomic nervous system that act in tandem to maintain a state of homeostasis in the body for the maximum possible time.

Differences:

PARASYMPATHETIC EFFECTS

SYMPATHETIC EFFECTS

Narrowing (constricting) the pupils of the eyes to admit less light

Widening (dilating) the pupils of the eyes to admit more lights

Constricting the trachea and lung airways to reduce volume of each breath

Widening of the trachea and lungs to increase the volume of each breath

Decreasing the rate and force of heart contraction

Increasing the rate and force of heart contraction

Stimulating liver to remove glucose from blood and store it as glycogen or glycogenesis

Stimulating liver to release glucose into blood or glycogenolysis.

Increasing peristaltic movement of the digestive tube

Decreasing peristaltic movement of the digestive tube

Relaxed muscular sphincter of digestive tube

Contracted muscular sphincter of digestive tube

Increasing enzyme secretion by and muscular contraction of stomach

Decreasing enzyme secretion by and muscular contraction of stomach

Increasing speed of movement of food along intestines

Decreasing the speed of movement of food along intestines

Increased blood clotting period

Decreases blood clotting period

Postganglionic fibre secrete acetylcholine as nuerotransmitter

Postganglionic fibre mostly secrete norepinephrine or epinephrine as neurotransmitter

Decreases secretion of sweat

Increased secretion of sweat

Relaxation of arrector pili muscles

Contraction of arrector pili muscles so the hair stand erect, causing "goose flesh"

Causing contraction of bladder wall, opening of sphincter, release of urine

Causing relaxation of bladder wall, closing of sphincter, thereby inhibiting release of urine

WEB OUTPUT

Cause of Nerve Fiber Damage In Multiple Sclerosis Identified

Multiple Sclerosis is a chronic central nervous system disease, primarily in young adults. The myelin of a patient with Multiple Sclerosis leaves a scar. The areas where there is either not enough or no myelin are called lesions. The nerve fiber can break or become damaged as the lesions get worse.

When a nerve fiber has less myelin the electrical impulses received from the brain do not flow smoothly to the target nerve as a result the nerve fibers cannot conduct the electrical impulses at all. The electrical impulses are instructions from the brain to carry out actions, such as to move a muscle. MS is the disability to get your body to do what your brain wants it to.

Researchers have now recognized how the body's immune system contributes to the nerve fiber damage caused by multiple sclerosis, a discovery that can potentially aid earlier diagnosis and enhanced treatment for this chronic disease.

The study reveals how immune system B-cells damage axons during MS attacks by inhibiting energy production in these nerve fiber cells, ultimately causing them to degenerate, relapse and die.

In this study, Dr. Yufen Qin and fellow researchers from UC Irvine's School of Medicine noted an increased level of B-cell antibodies on lesions and in spinal fluid bound to two specific enzymes - Glyceraldehyde 3-phosphate dehydrogenase aslso know as GAPDH and Triose-phosphate isomerase also known as TPI. These two enzymes are necessary for efficient energy production. The researchers believe that the binding of these antibodies to these enzymes - GAPDH, in particular - may subordinate the amounts of ATP available in cells, which eventually can lead to axon cell degeneration and death.

Other recent studies have shown that binding of inhibitors to GAPDH and TPI causes decreased ATP production in neurons, followed by progressive neuronal degeneration and death. Moreover, patients with TPI deficiency can develop progressive neurological disorders like Multiple Sclerosis.

Much MS research is focused on an autoimmune process in which T-cells attack and damage myelin, the fatty insulating tissue of axons. These T-cells do not attack axons themselves; the process of demyelination interrupts electrical impulses that run through these nerve fibers, thus causing MS symptoms like motor dysfunction such as weakness, paralysis, spasticity and abnormal gait, sensory dysfunction such as paresthesias, decreased proprioception and crebellar dysfunction such as tremor, incoordination and ataxia.

Research at UCI and elsewhere has shown that myelin grows back if the T-cell autoimmune response is turned off, and drugs exist or are in development to block demyelination. Axons, in turn, repair very slowly, which implies that B-cell attacks on axons may have a significant impact on the chronic central nervous system damage caused by MS.

Source:

Vasich (2006). Multiple Sclerosis News. Cause of Nerve Fiber Damage In Multiple Sclerosis Identified. Retrieved from http://www.medicalnewstoday.com/articles/54327.php

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