Homeostasis PDF

+-----------------------------------+-----------------------------------+ | Homeostasis | | +===================================+===================================+ | NP4203 Introduction Applied Life | | | sc...

+-----------------------------------+-----------------------------------+ | Homeostasis | | +===================================+===================================+ | NP4203 Introduction Applied Life | | | science | | +-----------------------------------+-----------------------------------+ | **What is Homeostasis?** | **How does the body respond to | | | change?** | +-----------------------------------+-----------------------------------+ | - Maintenance of a constant | - Maintain -- to keep up | | environment in the body | | | | - Constant -- the same | | - Body cells work best if they | | | have the correct balance | - Internal -- inside the body | | | | | - Body has mechanisms to keep | - Environment -- surroundings | | the cells in a constant | of the body | | environment | | +-----------------------------------+-----------------------------------+ | **Physiological variables** | **Maintenance of homeostasis is | | | through feedback** | +-----------------------------------+-----------------------------------+ | - Core temperature | - **Feedback system** -- cycle | | | of events which the status of | | - Water and electrolyte | a body condition is | | concentration | continually monitored, | | | evaluated, changed, re- | | - Ph (acidity /alkalinity) of | monitored, re-evaluated | | body fluids | | | | | | - Blood glucose level | | | | | | - Blood and tissue oxygen and | | | carbon dioxide level | | | | | | - Blood pressure | | +-----------------------------------+-----------------------------------+ | **2 Types of Homeostatic control | 1. **Negative feedback System** | | mechanism** | | +-----------------------------------+-----------------------------------+ | 2. Negative feedback mechanism | | | | | | 3. Positive feedback system | | +-----------------------------------+-----------------------------------+ | **Homeostasis is maintained by | **Negative feedback summary** | | feedback system -- Example of | | | positive feedback** | | +-----------------------------------+-----------------------------------+ | - Most common feedback system | - Prevents sudden, severe | | is negative | changes in the body | | | | | - Pressure of baby head during | - Reduced the actions of the | | labour results in an increase | effector | | contraction -- positive | | | feedback system | - Corrects the set point | | | | | | - Causes opposite of bodily | | | disruption to occur | | | | | | - Limits chaos in the body by | | | creating stability | | | | | | - Most common type of feedback | | | loop | | | | | | - Examples: body temperature, | | | blood pressure and glucose | | | regulation | +-----------------------------------+-----------------------------------+ | **Positive feedback summary** | **Controlling body temperature** | +-----------------------------------+-----------------------------------+ | - Increases (accelerates) the | **Why are newborn babies prone to | | action of the body | develop hypothermia?** | | | | | - Produces more chaos in the | - Animals with large SA | | body | compared to their volume will | | | lose heat faster than animals | | - Few types necessary for our | with small surface area. | | survival | | | | | | - Positive feedback mechanism | | | are short lived | | | | | | - Controls only infrequent | | | events that do not require | | | continuous adjustments | | | | | | - Considered to be uncommon | | | loop | | | | | | - Example: blood clotting and | | | childbirth | | +-----------------------------------+-----------------------------------+ | **Temperature control** | **What mechanisms are there to | | | cool the body down?** | +-----------------------------------+-----------------------------------+ | - Hypothalamus | 1. **Sweating** | | | | | - Under 5 years -- labile | - when body is hot -- sweat | | homeostatic control | glands are stimulated to | | | release sweat | | - Temperature varies during the | | | day eg. 37.5 at 14.00 = | - The liquid sweat turns into a | | pyrexia | gas (it evaporates) | | | | | - But at 02.00 = pyrexia | - To be able to do this, it | | | needs heat | | - Brown fat | | | | - It gets that heat from your | | | skin | | | | | - 4% of baby fat mass | - As your skin loses heat, | | | cools down | | - Around | | | kidneys, adrenals, muscles | | | and body vessel of neck, | | | mediastinum, scapular and | | | axillae until 10 years of age | | +-----------------------------------+-----------------------------------+ | **Vasodilation** | **What mechanisms are there to | | | warm the body up? | | | Vasoconstriction** | +-----------------------------------+-----------------------------------+ | - Your blood carries most of | - Opossite of vasodilation | | the heart energy around the | | | body | - Capillaries underneath your | | | skin gets constricted (shut | | - Capillaries underneath your | off) | | skin that can be filled with | | | blood if too hot | - Takes the blood away from the | | | surface of the skin so less | | - Brings the blood closer to | heat can be lost | | the surface of the skin so | | | more heat can be lost | | | | | | - Why you look red when your | | | hot | | +-----------------------------------+-----------------------------------+ | **Piloerection** | **Negative feedback loops** | +-----------------------------------+-----------------------------------+ | - When the hair on skin stands | | | up | | | | | | - Sometimes called goose bumps | | | | | | - Hair trap a layer of air next | | | to the skin which is then | | | warmed by body heat | | | | | | - Air becomes an insulating | | | layer | | +-----------------------------------+-----------------------------------+ | **Maintaining blood glucose | **If there is too much glucose in | | Level** | the blood,** | +-----------------------------------+-----------------------------------+ | - Cells need stable level of | - Insulin converts some of it | | glucose in the blood | to glycogen | | | | | - Excess glucose gets turned |  | | into glycogen and stored in | | | the liver | | | | | | - Regulated by 2 hormones | | | (chemicals) from the pancreas | | | called: | | | | | | | | | | | | - Insulin | | | | | | - Glucagon | | +-----------------------------------+-----------------------------------+ | **If there is not enough glucose | **Controlling water Levels** | | in the blood,** | | +-----------------------------------+-----------------------------------+ | - Glucagon converts some | - The control of water levels | | glycogen into glucose | Is carried out by the KIDNEYS | | | | |  | - Closely linked to the | | | excretion of urea | | | | | | - Urea is waste product made | | | when liver breaks down | | | protein that are not needed | | | by the body | | | | | | - Urea contains the element | | | Nitrogen | +-----------------------------------+-----------------------------------+ | **Controlling water content** | **Reabsorbing water** | +-----------------------------------+-----------------------------------+ | - The amount of water | - If there have too little | | reabsorbed into the blood | water in blood, produce very | | vessels in the kidney is | concentrated urine -- very | | controlled by the hormone ADH | little water | | | | |  | - If you have too much water in | | | your blood, produce more | | | dilute urine -- lots of water | +-----------------------------------+-----------------------------------+ | **Control of blood pressure** | **What is Homeostasis?** | +-----------------------------------+-----------------------------------+ | - Homeostasis through | - Maintenance of a constant | | regulating blood pressure | environment in the body is | | mechanism: heart rate, water | called Homeostasis | | balance, respiratory rate and | | | blood sugar level. | | +-----------------------------------+-----------------------------------+