Chapter 7: Maintaining an Internal Balance Unit 3: Homeostasis Chapter 7: Maintaining an Internal Balance

What is Homeostasis? The body’s attempt to adjust to a fluctuating external environment. Body maintains a constant balance or steady state. The system of balance requires: constant monitoring and feedback about body conditions.

Homeostatic Control Systems The system has three functional components: A monitor A coordinating center A regulator

What are the functions? 1. Monitor Section 7.1: Pages 334-337 What are the functions? 1. Monitor Located in the organs and signals a coordinating center when it detects an organ is working outside its normal limit 2. Coordinating Center Relays information to the corresponding regulator 3. Regulator Works to restore the normal balance

An Example: When you exercise… Section 7.1: Pages 334-337 An Example: When you exercise… Carbon dioxide levels increase and Chemical receptors in the brain are stimulated  Monitor Nerve cells from the brain relay the message via impulses to the organ  Coordinating Center Muscles increase the depth and rate of breathing which flushes the excess carbon dioxide  Regulator

Homeostasis is often referred to as dynamic equilibrium. Section 7.1: Pages 334-337 Homeostasis is often referred to as dynamic equilibrium. The homeostatic mechanism ensures that all body systems function within a tolerable range. This includes monitoring and regulating fluctuations in blood glucose, body temperature, blood pressure and blood pH.

Section 7.1: Pages 334-337

Section 7.1: Pages 334-337 Feedback Loops There are two types of feedback systems that exists within the body: a) Negative Feedback System – mechanism that makes adjustments to bring body back to acceptable range b) Positive Feedback – mechanism that perpetuates the system and moves the controlled variable even further away from its steady state Think… (-) = resisting change or compensating (+) = reinforcing the change

Section 7.1: Pages 334-337 Negative Feedback System Suppose you like your house a certain temperature…

Positive Feedback System: The Birthing Process Section 7.1: Pages 334-337 Positive Feedback System: The Birthing Process Decrease in progesterone Initiates contractions Contractions release the hormone oxytocin This release strengthens contractions Contractions keep building

Section 7.2: Pages 338-341 Thermoregulation

Ectotherms Endotherms Section 7.2: Pages 338-341 Thermoregulation: This describes the body’s ability to maintain a temperature range where cells can function Ectotherms Endotherms Ectotherms depend on air temperature to regulate metabolic rate  activity is partially dependant on environment Ectotherms – most fish, amphibians, and reptiles Endotherms maintain a constant body temperature regardless of the surrounding temperature They increase cellular respiration to compensate for heat loss Endotherms – mammals and birds

Section 7.2: Pages 338-341 The Hypothalamus It is the region of the vertebrate brain that is responsible for numerous nerve and hormone functions The “thermostat” An example of the coordinating center in the homeostatic control system.

How to deal with stress: the hot and cold kind

How to deal with stress:

Section 7.2: Pages 338-341 Quick Review:

The Importance of Excreting Wastes Section 7.3: Pages 342-345 The Importance of Excreting Wastes

Section 7.3: Pages 342-345 Getting Rid of Wastes Average Canadian consumes more protein than is required to maintain tissues and promote cell growth Excess protein  Converted into carbohydrates The proteins contain nitrogen which has two hydrogens attached = toxic

Section 7.3: Pages 342-345 Deamination AMINO ACID

Deamination: Flushing it Out Section 7.3: Pages 342-345 Deamination: Flushing it Out There are three types of waste products: ammonia, urea and uric acid. Deamination of amino acids results in NH3 (a toxic, water-soluble gas) Ammonia plus carbon dioxide results in  urea which is 100,000 times less toxic than ammonia An additional waste product results from the breakdown of nucleic acids, such as DNA  uric acid

Section 7.3: Pages 342-345 Water Balance The kidney helps maintain water balance when water is lost due to urine, perspiration, increased physical activity and exhaled air They are also responsible for filtering wastes from the blood.

Excretion for the Simple and Complex Section 7.3: Pages 342-345 Excretion for the Simple and Complex In unicellular and primitive multicellular organisms, wastes are expelled directly into the environment and carried away by water How do primitive organisms maintain fluid retention? The contractile vacuole maintains osmostic balance by pumping water out of the cell

Excretion for the Multicellular Section 7.3: Pages 342-345 Excretion for the Multicellular Triple-layered organisms such as insects, worms and mammals, cannot directly expel wastes because: - not every cell interacts with the environment - not every cell is designed to remove wastes (cell specialization) Resolution? - wastes are transported to cells that are capable of excretion and removed or stored by the excretory system

Any Questions?