The History Of The Neurosensory Biology Essay

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The nervous system is divided into the central nervous system and the peripheral nervous system. The central nervous system contains the brain and spinal cord. It is all enclosed and protected by the cranium and the vertebrae. The nervous system is responsible for the body's ability to interact with the environment and regulation of activities involving the internal organs. It is a complex network of structures that transmit signals between the body's many organs and tissues to the brain. The peripheral nervous system is composed of cranial nerves and the spinal nerves. Peripheral nerves pathways are broke down into afferent pathways. These are ascending pathways that carry sensory impulses toward the central nervous system. The other peripheral nerve pathways are efferent pathways. These are descending pathways, which supply skeletal muscle or organs innervated by specific components of the nervous system by transmitting motor impulses away from the central nervous system. With the function of the peripheral nervous system, it can be divided down into the somatic nervous system and the autonomic nervous system. The somatic nervous system consists of pathways that regulate voluntary motor control such as skeletal muscle. The autonomic nervous system is involved with regulation of the internal environment such as the viscera through involuntary control of the organ systems. This system is also further divided into sympathetic nervous system and the parasympathetic nervous system. (Huether &McCance, 2008)

Pain is experienced by the patient through the nervous system. The portions of the nervous system responsible for the sensation and perception of pain is divided into three different areas; afferent pathways, interpretive centers, and efferent pathways. Afferent pathways begin in the peripheral nervous system and travel to the spinal gate in the dorsal horn and then ascend to higher centers in the central nervous system. Interpretive centers are located in the brainstem, midbrain, diencephalon, and cerebral cortex. The efferent pathways descend from the central nervous system back to the dorsal horn of the spinal cord. The sensory process leading to the perception of pain is called nociception. The receptors are free nerve endings that respond to chemical, mechanical, and thermal stimuli. They are found under the skin and within joint and bone surfaces, deep tissues, muscles, tendons, and subcutaneous tissue. The relative sensitivity of pain differs according to the area of the body. There are two major types of nociceptors; A fibers and C fibers which are afferent neurons. The C fibers are responsible for transmission of burning and aching sensations. C fibers are small and transmission is relatively slow and poorly localized. This causes slow pain. A fibers are larger and transmit pain faster and carry well-localized, sharp pain sensations. (Huether & McCance, 2008)

AH has experienced several different types of pain during her life. With her myocardial infarction, she experienced somatogenic pain. This pain has a cause compared to psychogenic pain, which has no physical cause. AH did not describe any referred pain (pain present in an area removed or distant from its area of origin) with this myocardial infarction. AH acute pain with her bilateral hip replacements. This is a protective mechanism that alerts the person to a condition or experience that is immediately harmful to the body. It is categorized as acute pain because of lasting less than six months. AH also experiences chronic pain intermittently currently. It has been present for over six months. This chronic pain is due to her osteoarthritis and is related to the inflammation and injury to her joints. AH does not take any analgesics for this pain besides Ibuprofen at home. She did not state any need to "as needed" analgesics while admitted.

The brain enables an individual to function effectively, express mood, and interact with the external environment. An adequate supply of oxygen to the brain is essential to maintain proper functioning. (Ignatavicius & Workman, 2010) AH's congestive heart failure could cause inadequate blood supply and decreased oxygen to the brain due to the pump not working efficiently. When the brain has this decreased blood and oxygen level, cognitive functioning may change and eventually decline. When the brain recognizes these insufficient levels, compensatory mechanisms turn on to try and fix the present problem. Stimulation of the sympathetic nervous system as a result of tissue hypoxia is the most immediate compensatory mechanism. (Huether &McCance, 2008)

Stimulation of the adrenergic receptors causes an increased heart rate and blood pressure from vasoconstriction. Increased heart rate causes an increased cardiac output since heart rate is a factor along with stroke volume that creates cardiac output. An increase in heart rate is limited in its ability to compensate for decreased cardiac output. Increased heart rate creates an increased oxygen demand by the myocardium. Also, any history of arteriosclerosis can worsen symptoms of heart failure. Stroke volume is also improved since sympathetic stimulation causes venous return to the heart increase. This venous return causes dilation and according to Starlings law, increased myocardial stretch results in forceful contractions. Once there is a point reached however, the stretched cardiac muscle stretches too far and reduces the force of contractions and cardiac output. There are no signs or symptoms of impairment at this time. (Huether & McCance, 2008)

Due to AH taking diuretics (Bumex) to reduce her fluid retention and keep it from increasing, AH is at risk for neurologic impairments from hypokalemia (potassium deficiency). Neurologic symptoms can be generalized weakness, depressed reflexes, and muscular symptoms. AH shows none of these neurologic impairments at this time.

AH is also at an increased risk for having a stroke. A stroke occurs when the blood supply to the brain is changed. This is a medical emergency and can cause many long-term deficiencies such as cognitive changes, weakness, and paralysis. There are several risk factors that put AH in the risk category. Hypertension, sedentary lifestyle, and elderly age place her in this category at this time. (Ignatavicius & Workman, 2010)

Metabolic/Endocrine

The endocrine system is composed of various glands that are located throughout the body. The glands that make up the endocrine system include the hypothalamus, pituitary, parathyroids, thyroid, thymus, adrenals, pancreas, ovaries, and testes. These glands can produce and release hormones (special chemical messengers). Hormones transport specific regulatory information among cells and organs and are integrated into the central nervous system to maintain control. The creating and releasing of hormones into the circulation trigger intracellular responses. Hormones impact growth, development (beginning as a fetus), digestion, and regulate metabolism and reproduction. Feedback systems provide accurate monitoring and control of the cellular environment. Negative feedback systems are important in maintaining hormones within physiologic ranges. When all endocrine glands are working properly, homeostasis in the body occurs. (Huether & McCance, 2008)

The compensatory mechanism that affects the endocrine system from congestive heart failure due to low cardiac output is the secretion of vasopressin. Due to AH's history of congestive heart failure, her endocrine system is affected in this way. When there is decreased cerebral perfusion, the posterior pituitary gland secretes vasopressin also known as antidiuretic hormone (ADH). This hormone causes vasoconstriction and fluid retention, which actually worsens heart failure. AH does not have any other hormone malfunctions during this time.

Immunologic/Integumentary

The integumentary system is composed of the skin, hair, nails, and glands. The skin is the largest organ of the body, and hair, nails, and glands are accessory structures. The primary function of the skin is to protect the body from the environment by assisting as a barrier against microorganisms, loss of body fluids, and mechanical forces. It is our first line of defense. The skin also regulates body temperature and is involved in immune regulation and the activation of vitamin D. Touch and pressure receptors provide important protective functions. (Huether & McCane, 2008)

AH is a clean individual with intact skin. An issue she has however, is that she lives a sedentary lifestyle. This puts her at risk for skin breakdown. At this time there are no signs or symptoms of breakdown present. Patient education was done in regards to the benefits of ambulation and skin barrier creams when needed. AH is also elderly which makes her skin thin and easy to break the barrier. This can allow microorganisms access into her system and cause infection.

The purpose of inflammation and immunity is to meet the human need for protection by neutralizing, eliminating, and destroying organisms that invade the internal environment. These organisms can be infectious and non-infectious. Infectious agents include bacteria, viruses, parasites, and fungi. Non-infectious agents can be pollen, foods, or bee venoms. (Huether & McCance, 2004/2008) Immune system cells use protective actions only against non-self proteins and cells. Immune system cells can distinguish between the body's own self cells and non-self proteins and cells. The immune system cells are the only body cells capable of determining this. Phagocytosis is the process of the leukocytes (white blood cells) in the body ingesting foreign microorgansims. The leukocytes used are neutrophils and monocytes. Inflammation is also called natural immunity. This provides immediate protection against the effects of tissue injury and invading non-self proteins. Inflammation can cause discomfort but it is important in ridding the body harmful organisms. Inflammatory responses help start both antibody-mediated and cell-mediated actions to activate the full immune response.

AH does not have any current infections in her body at this time. Her white blood cells currently are in a normal range. Exact lab values are in the table above. AH's neutrophils and monocytes are above normal levels. An increased neutrophil count could be due to inflammation caused from her osteoarthritis. Increased monocytes could be due to the body sensing there is a risk for infection. Her lymphocytes are also below normal range. This could be due to drug therapy and immune-compromised due to elderly age. Congestive heart failure does have inflammatory properties. In patients who have had a myocardial infarction, heart muscle cell injury causes an immune response. Pro-inflammatory cytokines such as tumor necrosis factor and interleukins are released, especially with left sided heart failure. These substances contribute to ventricular remodeling. (Ignavaticius & Workman, 2010)

Sexual/Reproductive

The structure and function of female reproductive systems depend on steroid hormones, which are called sex hormones. Hormonal effects on the reproductive systems start to begin during embryonic development and continue in varying degrees throughout life. The presence of estrogen and the absence of testosterone cause the two female gonads to develop into ovaries. The female reproductive system is both internal and external. The external genitalia include the vulva, mons pubis, labia majora, labia minora, clitoris, vestibule, and the perineum. The internal genitalia include the vagina, uterus, fallopian tubes, and ovaries. The breasts are also considered part of the reproductive system. In females, the most important reproductive organs are internal. (Ignavaticius & Workman, 2010)

Menopause is the biological end of reproductive ability and can only be applied to the last menstrual period. The actual date cannot be determined until at least one year has passed without menses. The follicles in the ovaries atrophy throughout life. This causes low levels of estrogen and progesterone. Estrogen is needed by bone tissue for calcium uptake. It also increased vitamin D, which is needed for calcium absorption from the intestines. Bone density declines in patients with decreased calcium uptake. (Ignaviticus & Workman, 2010) In AH's case, decreased bone density put her at higher risk for fractures and also causes more complications with her osteoporosis. AH is not taking calcium supplements at this time. AH is also not on any estrogen replacements.

Aging also causes drying, smoothing, and thinning of the vaginal walls. This causes discomfort during intercourse and can cause decreased interest for the patient. When asked about sexual intercourse, AH stated that she had "no interest in sex". This was due to her husband passing away in 1995 and not having any new relationships.

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