The nervous system is a complex combination of nerve cells, which controlling and coordinating all aspects of behavior and is important in homeostasis (Bradley & Calvert 2011). Nerve cells coordinate information received from different sources and transport this information to other cells (Bradley & Calvert 2011). Functional units are built of sets of nerve cells and they are dealing with specific types of information (Bradley & Calvert 2011). Some of them will be responsible for processing of sensory information and other handle motor functions (Bradley & Calvert 2011). The nervous system deals with coordination of movement, higher thinking processes, memory, emotions, sensory information and control essential functions such as breathing (Bradley & Calvert 2011). The nervous system is defined as a brain, spinal cord and peripheral nerves (Bradley & Calvert 2011).
The most important function of the endocrine system is to maintain homeostasis (Bradley & Calvert 2011). Humans belong to a group of endothermic animals that must maintain constant body temperature Native Remedies (2012) [ONLINE]. Ectothermic animal’s temperature has wider range and depends on various conditions. Humans have the ability to function normally, while ectothermic animals can feel lethargic in lower temperatures Native Remedies (2012) [ONLINE].
Thyroid Function
An excellent example of homeostasis controlled by endocrine system is thyroid function that is responsible for regulation of energy consumption, calcium in the blood and protein production Native Remedies (2012) [ONLINE].
The hypothalamus perceives the insufficiency of thyroid hormones such as thyroxine and triiodothyronine and releases hypothalamin.
Hypothalamin then activates anterior pituitary cells, which are responsible for secretion Native Remedies (2012) [ONLINE]. The anterior pituitary relases the hormone that is responsible for thyroid stimulation called thyrotropin and starts producing more thyroxine Native Remedies (2012) [ONLINE]. Approx 80 % of thyroxine will change into triiodothyronine. If there is higher level of thyroid hormones, the hypothalamus will correct the measure to “set point” Native Remedies (2012) [ONLINE].
If the glands of the endocrine system are affected by hypo or hyper function, this then would be classified as the main cause of disease such as hypothyrodoism and hyperthyrodoism (over or under production of thyroid hormone) Native Remedies (2012) [ONLINE].
Regulation of plasma glucose.
Regulation of plasma glucose is also based on hormonal feedback. After meal consumption, glucose is absorbed from small intestine and this causes higher level of glucose in plasma (Bradley & Calvert 2011). Extended raised level of plasma glucose can damage the body in particular the blood vessels in the kidney and retina (Bradley & Calvert 2011). Therefore I is important to keep level of glucose in the normal range such as 4.5-5.6 mmol/l (Bradley & Calvert 2011).
A glucose level is detected by beta cells located in pancreas glands (Bradley & Calvert 2011). The beta cells hold vesicles, which are responsible for storage of insulin (Bradley & Calvert 2011). Glucose penetrates the beta cells and secretes insulin into the bloodstream (Bradley & Calvert 2011). Secretion of insulin is aroused when plasma glucose level reach above 5 mmol/l (Bradley & Calvert 2011). Insulin would then be transported through bloodstream to its aim tissue such as liver or skeletal muscles. Insulin links to its receptor and corrects the amount of glucose in the cells of these tissues (Bradley & Calvert 2011). As soon as the level of glucose is brought back to the normal range the secretion of insulin is shut down (Bradley & Calvert 2011). The main disease which can be caused by this abnormality is diabetes ( hyperglycaemia) (Bradley & Calvert 2011). If the situation is the other way around, and glucose level is lower then normal range, then another type of cells called alpha will produce hormone called glucagon (Bradley & Calvert 2011). This hormone will stimulate liver to convert glycogen into glucose that is then transported into the blood stream (Bradley & Calvert 2011).
(Bradley & Calvert 2011).
Fig.1 Feedback loop on the control of glucose (Bradley & Calvert 2011).
Thermoregulation
Constant temperature of human body is very important for the correct function of body systems (Bradley & Calvert 2011). If the temperature reaches 41C and above, then proteins start to denatured and metabolic systems stops to function (Bradley & Calvert 2011). If the temperature reaches 32C then energy production is very low which results in poor cells function (Bradley & Calvert 2011). Temperature regulation is an excellent example of neural homeostatic mechanism and is obtained through performance of autonomic nervous system (Bradley & Calvert 2011). The hypothalamus is the main regulatory center located in the brain. The change in the temperature is detected by the temperature of the blood, which travels through that centre (Bradley & Calvert 2011). The peripheral temperature is monitored by neural impulse from thermoreceptors in the skin, which reacts to cold and warm (Bradley & Calvert 2011). The hypothalamus contain a different type of cells which response to either lower or higher temperature (Bradley & Calvert 2011). If the body detects a different temperature then different mechanism such as metabolic, neural, behavioral will response by heat production and regulation of the heat in periphery (Bradley & Calvert 2011).
If the temperature decreases, the sympathetic nervous system increases its activity by narrowing blood vessels located near the body surface and diverts blood away from vessels underneath the epidermis of the skin- this process reduces heat loss from the skin surface (Bradley & Calvert 2011). The muscles that are connected to hair follicles are activated and start to contract resulting the hair to “stand out” (goosebumps) (Bradley & Calvert 2011). Then skeletal muscles are activated and start to rapidly contract and relax resulting in shivering (Bradley & Calvert 2011). In consequences metabolic activity is highly stimulated which will result in heat production (Bradley & Calvert 2011). Also hormones such as thyroid hormone and adrenaline will be released to speed up metabolism in liver and produce more heat (Bradley & Calvert 2011). Also behavioral mechanism will be stimulated which will result in looking for shelter or wearing warm clothes (Bradley & Calvert 2011). Babies hold also thermoregulatory mechanism, which contain a special adipose tissue known as brown fat (Bradley & Calvert 2011). When this tissue is activated, a protein in the mitochondria takes away the product of the citric acid cycle from electron transport chain, and the energy is changed to heat instead of producing ATP (Bradley & Calvert 2011).
If the temperature is increased, peripheral blood vessels expand and help the blood flow near the skin and loose more heat by radiation (Bradley & Calvert 2011). Also, sweat glands are stimulated and releasing sweat onto skin surface for further heat loss due to evaporation (Bradley & Calvert 2011). The muscles connected to the hair follicles will remain flat and close to the skin surface to support more heat loss through evaporation (Bradley & Calvert 2011). The hormones production such as adrenaline and thyroid will be decreased, which will result in slow metabolism (Bradley & Calvert 2011). Also behavioral mechanism will be activated such as hiding from the heat (Sun) searching for a shade or reducing the amount of clothes worn (Bradley & Calvert 2011). Fever (pyrexia) is a response to the body to fight an infection (Bradley & Calvert 2011). High temperature improves the action of immune system and minimizes the ability for microorganism to replicate (Bradley & Calvert 2011). Those microorganism release toxins, which stimulating production of protein IL-1 from the immune system’s cells (Bradley & Calvert 2011). IL-1 interacts with blood vessels in the hypothalamus and activates production of prostaglandinE2, which decreases the fairing of warm sensitive neurons (Bradley & Calvert 2011).
Fig.2 Temperature Regulation (Bradley & Calvert 2011).
Summary
Both nervous and endocrine systems, endlessly monitor and control cells in our bodies, however there are slight differences and similarities in the way they both work (Bradley & Calvert 2011). Within the nervous system transmission of information is fast and can take as little as milliseconds (Bradley & Calvert 2011). This is due to sensory receptors, which immediately sends information from the nerves to the brain (Bradley & Calvert 2011). Within the endocrine system monitoring and controlling of our body is achieved by circulatory system so it reacts slower and can take up to hours, days or even weeks to obtain an effect (Bradley & Calvert 2011). The endocrine system can affect many organs and tissues (Bradley & Calvert 2011). In regards to similarities, several different types of chemicals used by both systems such as adrenaline Onteora (2012) [ONLINE]. Some effects of both systems can have impact on the same organs and tissues Onteora (2012) [Online]. Both systems have the ability to regulate each other Onteora (2012) [ONLINE]. Sometimes
those two systems can be defined as neuroendocrine to emphasize the importance of their function in human body. (Bradley & Calvert 2011).
Understanding of homeostasis is an important part to understand human physiology and maintain healthy well-being (Bradley & Calvert 2011).
References:
Bradley, P. & Calvert, J. (2011) Biology for medical sciences. 4th ed. Newcastle upon Tyne: Scion
Native Remedies. (2012) Endocrine systems and homeostasis [ONLINE] Available from: www.nativeremedies.com [accessed 20th February 2012]
Onteora. (2012) Chemical Regulation [ONLINE] Available from: www.onteora.schoolwires.com [accessed 20th February 2012]
Thibodeau, G. & Patton, K. (2008) Structure and function of the body. 13thed. Missouri: Mosby Elsevier
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