Homeostasis: Similarities and Dissimilarities between Nervous and Endocrine Systems - Essay Example

Homeostasis Introduction: Homeostasis is, in fact, maintenance of an environment. In medical science, it is an ability of human body to keep internal environment at or around (with very narrow range) a level in which various systems of the body can perform smoothly. Through this property human body responds to different types of disturbances of homeostasis efficiently so that health is maintained. Thus internal environment of the body is maintained by a close surveillance system and timely response to any change which may affect homeostasis. This adjustment of physiological systems within the body is called homeostatic regulation (Wikiepedia 2007). As body needs to respond to any disturbance in the internal milieu very quickly therefore initial response of the body is a reflex response usually takes place through peripheral controlling systems, especially nervous system. Failure of homeostasis causes diseases disease and sometimes death. Control of homeostasis: Major systems controlling homeostasis in the body are nervous system and endocrine system. These systems have got their own specific characteristics which make them integral components which help maintain homeostasis: Nervous system usually acts faster, in milliseconds, as compared to hormonal system. Homeostasis is usually controlled involuntarily i.e. automatically except in some situations in which this control becomes voluntary especially control by nervous system. Endocrine system is controlled by nervous system; hypothalamic-pituitary system plays an important part in this control. Nervous system utilizes electrical neurotransmitters while chemical transmitters are utilized by endocrine system. Nervous system: Autonomic nervous system (sympathetic and parasympathetic arms) works along with brainstem and hypothalamus in maintaining the internal milieu of the body. Endocrine system: Major endocrine glands, with their hormones, involved in homeostasis are (bloom & Lazerson; BYB4) 1. Pituitary: various hormones regulate other organs; 2. Gonads: estrogen and progesterone; testosterone. These steroids affect reproduction and reproductive behavior. 3. Thyroid: thyroxin increases metabolic rate; 4. Parathyroid: calcitonin retains calcium; 5. Adrenal cortex: corticosteroids - adaptation to stress; 6. Adrenal medulla: adrenaline - adaptation to stress; 7. Pancreas: insulin - regulation of blood glucose level. Physiological set points There are some physiological set points related to various systems in the body. Whenever there is disturbance to these set points body responds to this change and tries to bring the situation back to normal. This reversal of disturbance or change is necessary to keep an individual healthy and alive. Some of these conditions or parameters are: Body temperature: regulated close to 37 C Blood pH: kept at 7.4 Arterial blood pressure: maintained around 120/80 mm Hg Maintenance of blood glucose level Maintenance of fluids and salts, osmoregulation Central nervous system (CNS), autonomic nervous system (ANS) and endocrine systems work together to maintain these parameters within normal limits. Any change in the set points is detected and recognized by these systems and efficiently maintained by these systems with the help of feedback system. Initially, most of the time, nervous control takes this initiative of maintaining homeostasis o short term basis; afterwards, endocrine system takes the responsibility of responding change in the internal milieu. Homeostatic system functions following the "feedback mechanisms". Although, negative feedback system is utilized most of the time but in a limited number of situations positive feedback also gets itself involved (Wikipedia 2007; Biology Online). All feedback systems work in a systematic and well organized way, the major components of a feedback systems are: Sensors; Signal transmitters; Control center and Effectors. Sensors are directly involved in the situation, which disturb the internal environment of the body they relay signals to the central control area. In central control area, the received information is processed and appropriate instructions are sent to the effectors. These effectors act in a way, after receiving instructions, so that the resultant situation keeps or attempts to keep the internal environment of the body within normal limits (Bloom & Lazerson; BYB4). Similarities between nervous and endocrine systems As these both the systems work with the help of members of their systems, so pathways involved and the actors are different but the ultimate outcome is the same. Regulation of body temperature Receptors in hypothalamus detect temperature of blood while those receptors present in the periphery on skin they detect external temperature. When temperature is low, an individual feels cold and starts shivering. Shivering is, in fact, is a reflex response of the body in which muscles contract swiftly and produce heat in an attempt to bring the temperature to normal. Erector pili muscles contract enabling hair to trap air. Vasoconstriction of capillaries especially cutaneous vessels and divert blood to the internal organs to conserve heat. In long term conditions, thyroid gland gets stimulated and increases basal metabolic rate (BMR) by releasing T3 and T4 hormones. High BMR increases body temperature (Bloom & Lazerson; BYB4). Control of blood pressure Blood pressure is controlled by reflexes (baroreceptor reflex) and kidney. Whenever some stands up, suddenly, from lying position one feels dizziness as pressure in aorta falls because blood flows to lower limbs. Heart rate increases as a reflex response an increases the stroke volume out put. This in turn increases the cardiac output and eventually blood pressure. Kidneys maintain blood pressure on long term basis. Salt and water retention helps restore blood pressure. Sodium content is controlled by Na pump in response to aldosterone. This is controlled by rennin-angiotensin. In response to Na retention, water is resorbed osmotically. Thus blood volume increases which improves blood pressure. For water to be resorbed, water channels presence is necessary in renal tubules. Opening/closing of these channels is under control of anti-diuretic hormone (ADH). When there has enough water been resorbed then these channels are closed and no more water is brought in. (Bloom & Lazerson; BYB4) Dissimilarities between nervous and endocrine systems There are some situations in which one system may be involved. Usually, it happens in long term situations when only endocrine system may be responding to the change in body condition. In such situations, although, nervous system may not be totally excluded because of its over all controlling task but its role may not be as much prominent as that of endocrine system. In timing of caloric homeostasis, there are two hormones which are mostly involved, insulin and leptin. Secretion of leptin by adipocytes is related to mass of fat present in the body. Leptin acts through membrane receptors present in hypothalamus. This stimulation results in generation of satiation signals. In the states of starvation, more energy expenditure than conservation, mass of fat is consumed and thus reduces. This situation resulted in reduction of leptin and insulin secretion and thus stored energy is utilized (Berg 2002). Conclusions: Homeostasis is an important monitoring and controlling system in the body required for the efficient functioning of human body. Lack of homeostatic control may lead to real devastating situation. Nervous system, being the major controlling system of the body is responsible to carry out this task along with endocrine system. These two system works under their own unique ways with the help of their transmitters, electric transmission (neurotransmitters) in nervous system while chemical transmission in endocrine system. Usually, nervous system works as a first line system to respond any change in the homeostasis through reflex pathways and if the situation persists then endocrine system also gets involved to make adjustments appropriate for the efficient functioning of the body. References: Bloom & Lazerson, Homeostasis: maintaining the Internal Environment. Chapter 6. Retrieved from http://lifesci.rutgers.edu/auerbach/BMlec15.pdf 'Homeostatis', Wikipedia: the free encyclopedia. Retrieved November 9, 2007 from http://en.wikipedia.org/wiki/Homeostasis Berg JM, Tymockzo JL & Stryer L 2002, 'Caloric Homeostasis: A means of regulating body weight', Biochemistry, 5th edition. Retrieved November 9, 2007 from http://www.ncbi.nlm.nih.gov/books/bv.fcgihighlight=homeostasis&rid=stryer.section.4355#4365 'Biology Online',Physiological homeostasis. Retrieved November 10,2007 from http://www.biology-online.org/4/1_physiological_homeostasis.html 'A2 Biology Revision Course', Questionbase 50 megs.com. retrieved November 10, 2007 from http://lanther.co.uk/notes/BYB4.pdf Read More