Homeostasis Lecture Notes PDF

 Level of organization and Human body system 1- Chemical 2- Cellular 3- Tissue 4- Organs 5-System Level 6- Organismic Level  Groups of organs that perform related functions and interact to accomplish a common activity essential to survival of the whole body Do not act in isolation...

 Level of organization and Human body system 1- Chemical 2- Cellular 3- Tissue 4- Organs 5-System Level 6- Organismic Level  Groups of organs that perform related functions and interact to accomplish a common activity essential to survival of the whole body Do not act in isolation from one another Human body composed of eleven systems ( 11 system ). The 11 organ systems include the integumentary system (Skin) , skeletal system, muscular system, lymphatic system (immune ) , respiratory system, digestive system, nervous system, endocrine system, cardiovascular system, urinary system, and reproductive systems.  Defined as maintenance of a relatively stable internal environment Does not mean that composition, temperature, and other characteristics are absolutely unchanging Homeostasis is essential for survival and function of all cells Each cell contributes to maintenance of a relatively stable internal environment  Sensing and responding to changes in surrounding environment Control exchange of materials between cell and its surrounding environment Obtain nutrients and oxygen from surrounding environment Eliminate carbon dioxide and other wastes to surrounding environment Perform chemical reactions that provide energy for the cell Synthesize needed cellular components  Homeostasis involves dynamic mechanisms that detect and respond to deviations in physiological variables from their “set point” values by initiating effector responses that restore the variables to the optimal physiological range. Two systems that maintain homeostasis are: Nervous system & Endocrine system  Nervous system controls and coordinates bodily activities that require rapid responses , detects and initiates reactions to changes in external environment Endocrine system : Secreting glands of endocrine regulate activities that require duration rather than speed ,cControls concentration of nutrients and, by adjusting kidney function, controls internal environment’s volume and electrolyte composition  Concentration of nutrient molecules Concentration of water, salt, and other electrolytes Concentration of waste products Concentration of O2 = 100mmHg and CO2 = 40 mmHg pH = 7.35 Blood volume 4-6 L Blood pressure 120/80 Temperature = 37o C Homeostasis is continually being disrupted by: External stimuli : ( heat, cold, lack of oxygen, pathogens, toxins ) Internal stimuli : include ( Body temperature ,Blood pressure , Concentration of water, glucose, salts, oxygen, etc. ) Physical and psychological distresses Disruptions can be mild to severe If homeostasis is not maintained, death may result Homeostatic Control Systems Control systems are grouped into two classes Intrinsic controls Local controls that are inherent in an organ Extrinsic controls Regulatory mechanisms initiated outside an organ Accomplished by nervous and endocrine systems Feedforward - term used for responses made in anticipation of a change Feedback - refers to responses made after change has been detected Types of feedback systems Negative feed back & Positive feed back Types Negative feedback & Positive feedback original stimulus reversed most feedback systems in the body are negative used for conditions that need frequent adjustment Positive feedback original stimulus intensified seen during normal childbirth Negative Feedback Negative feed back loop consists of : 1- Receptor - structures that monitor a controlled condition and detect changes 2- Control Centre - determines next action 3- Effector receives directions from the control center produces a response that restores the controlled condition Explain how organisms maintain homeostasis (e.g., thermoregulation) Thermoregulation –skin and muscles : regulate body temperature Thermoregulation – process of maintaining a steady body temperature Sweating When your body is hot, sweat glands are stimulated to release sweat. The liquid sweat turns into a gas (it evaporates) To do this, it needs heat. It gets that heat from your skin. As your skin loses heat, it cools down. Thermoregulation – process of maintaining a steady body temperature Shivering – Hypothalamus signals skin and muscular, respiratory, and circulatory systems – Blood vessels constrict to reduce blood flow to prevent loss of heat – Muscles contract around pores – Muscles contract causing shivering – Thyroid releases hormones that increase metabolism Explain how organisms maintain homeostasis (e.g., water regulation ) Water Regulation After having a very salty meal  produce concentrated urine to remove excess salts in solution form  extra water is needed to be excreted along with the excess salts  sensation of thirst (drink more water to compensate for the water loss)  Water Regulation The amount of water in the blood must be kept more or less the same all the time to avoid cell damage as a result of osmosis. There has to be a balance between the amount of water gained (from your diet though drinks and food and the water produced by cellular respiration) and the amount of water lost by the body (in sweating, evaporation, feces and urine). This is achieved by the action of the hormone ADH (anti-diuretic hormone).  Water Regulation Part of the brain, the hypothalamus, detects that there is not enough water in the blood. The hypothalamus sends a message to the pituitary gland which releases ADH. This travels in the blood to your kidneys and as a result you make a smaller volume of more concentrated urine. The level of water in your blood increases until it is back to normal. If the level of water in your blood goes up the hypothalamus detects the change and sends a message to the pituitary. The release of ADH into the blood is slowed down or even stopped. Without ADH the kidneys will not save as much water and you produce large volumes of dilute urine. This is an example of negative feedback. Positive Feedback during Childbirth Stretch receptors in walls of uterus send signals to the brain Brain induces release of hormone (oxytocin) into blood stream Uterine smooth muscle contracts more forcefully More stretch, more hormone, more contraction etc. Cycle ends with birth of the baby & decrease in stretch