BTEC Applied Science Unit 9B: Homeostatic control of body systems

BTEC Applied Science Unit 9B: Homeostatic control of body systems. Homeostasis- The constant maintenance of a constant internal environment within an organism. One’s body needs to sustain its internal condition at certain levels to function. Homeostasis is called the preservation of internal conditions such as pH, temperature, and salt concentration in a stable equilibrium. Homeostasis is also known as a process of self-regulation by which an organism seeks to preserve equilibrium when adapting to the optimal environment for its survival. For example: homeostatic helps maintain optimal conditions for enzyme action and all cell functions, which then helps metabolic reactions to occur at appropriate rates. What will happen if homeostatic dysfunctions for theenzymes? As metabolic reactions involve enzymes, change in temperature such as increased body temperature will denature enzymes preventing the enzymes from conducting metabolic reactions effectively. What will happen if fault occurs in metabolic reaction? This will cause the organism to either have adequate or inadequate number of vital substances required to remain healthy. This helps us understand the significance of homeostasis’s role in an organism. Feedback and control Homeostasis calls for a high degree of monitoring and control; to detect internal and external changes and respond stimuli, hormones and nervous system communicate to bring about changes that brings symptoms back to the correct level. How is does hormones and nervous system helps homeostatic? The endocrine and nervous system are crucial for homeostasis. Endocrine transmits information through hormones which travels through the blood. Endocrine glands pass secretion directly into the blood stream rather than flowing a long duct. Slower messages are sent through hormones which allows more than one tissue, organ, or organ system to be targeted as it is carried around the body. Whereas Exocrine glands contain ducts that transport secretion from the glands to its surface. (Figure 1: the endocrine system) The nervous system uses nerve cells which transfers information as electrical impulses. Rapid messages are sent by the nervous system unlike endocrine. (Figure 2: the nervous system) These feedback mechanisms are used to track and control conditions within the organisms. There are two main feedbacks called negative feedback and positive feedback: Negative feedback The mechanism that reverses the change in internal conditions is called negative feedback; reverses change inside the organism through the effectors restoring the change back to the optimum. (Figure 2.1) Mechanism of negative feedback  The optimal point for the organism is tracked by the receptors.  They send signals to a co-ordinator (hormones or nervous system) when the receptors sense some changes away from the optimum.  The co-ordinator (hormones or nervous system) then determines which response is sufficient and sends signals to the effectors to carry it out.  Effectors bring about a transition that allows the internal regulatory changes to their optimal conditions. How does co-ordinated response work? Signals are obtained from several diverse sources by co-ordinators, these need to be evaluated before producing a response to function effectively. For example, signals can come from several various receptors that covers diverse types of stimuli and all this must be evaluated before sending the affecting signals. For example, there are temperature receptors in both the skin (e.g., Arms) and in the hypothalamus (found deep within the brain). As we exercise, we sweat, which lowers the skin temperature if the co-ordinator just. used skin information, it will. work to boost the body temperature when we exercise, but instead the co-ordinator usehypothalamic as well as skin information to make an effective appropriate response. (Figure 3: negative feedback in a central heating system) An example of negative feedback The hypothalamus in the brain regulates body temperature. The reaction is that the body starts to sweat to try to reduce the temperature down to the correct amount if the hypothalamus senses that the body is too hot. Sweating will stop until the body temperature is back to the correct amount. Conversely, if the hypothalamus senses that the body is too cold, the reaction is that the body starts shivering to attempt to lift the temperature up to the correct amount. The shivering will stop until the body temperature is up to the correct amount. Positive feedback Contrary to the negative feedback, positive feedback is the opposite: every change away from the sixed point is increased. A significant, unstable changes within the organism is caused by this mechanism. It is typically harmful, but there are instances when for example, its useful for action potential in neurons: nerve cells need to be able to transmit electrical impulses for communication along their axon length, they rely on positive feedback to function, influx of sodium ions triggers depolarisation during action potentials, which results in the opening of more voltage-gated sodium channels, resulting in even more depolarisation. (Figure 3.1: positive feedback) (Figure 4: positive feedback during labour) An example of positive feedback loop When the head of the foetus pushes up against the cervix in childbirth, it activates the nerves that tell the brain to activate the pituitary gland, which then releases oxytocin. Oxytocin triggers the contraction of the uterus. This brings the foetus ever closer to the cervix, leading to the development of more oxytocin before birth happens and the baby leaves the womb. Breastfeeding is also a positive feedback loop; the pituitary gland of the mother releases more of the hormone prolactin as the baby suckles, which allows more milk to be produced. Role of hormones and glands Endocrine glands- glands that release hormones directly into the blood are endocrine. (Figure 5: 12 endocrine glands in both female and male body) What is the importance of these three areas in the function of glands? Thermoregulation- This is regulated to maintain the temperature, which is normally 37 ° C, at which the enzymes of the body function best. Glucose regulation- This is regulated to provide a steady supply of glucose to cells for respiration. It is regulated by glucose release and storage, which is controlled by insulin in turn. Water balance- To protect cells, this is regulated by preventing too much water from entering or leaving them. Water content is regulated by the loss of water from:  Lungs - as we breathe out.  Skin - by sweating.  Body - in the urine produced by the kidneys. There are major endocrine glands, but I will go into detail with only 3 endocrine glands:  Pituitary endocrine gland Pituitary gland is found within the base of the brain. They secrete 5 types of hormones into the bloodstream: - Growth hormone - Prolactin hormone - antidiuretic hormone - Thyroid stimulating hormone - Adrenocorticotropic hormone which functions in controlling many other glands such as thyroid. (Figure 6)  Thyroid endocrine gland Thyroid gland is found underneath the larynx in the neck. They secrete 1 type of hormone into the bloodstream: - Thyroxine hormone which functions in the regulation of the metabolic rate. (Figure 7)   Pan c reas; an exocrine and endocrine gland Pancreas is found in the abdomen. Exocrine’s function in pancreas: secretes alkaline mucus which functions to neutralise stomach contents as they enter the duodenum. Endocrine’s function in pancreas: secretes insulin and glucagon which functions in blood and glucose’s regulation. (Figure 8) The pancreas acts both in an endocrine and exocrine gland. The Islets of Langerhans have an endocrine function that includes secreting insulin directly into the blood from beta cells and glucagon from alpha cells. The pancreas' exocrine