Homeostasis Talkie time and Recap This Powerpoint is

Homeostasis Talkie time and Recap This Powerpoint is hosted on www. worldofteaching. com Please visit for 100’s more free powerpoints

Competencies: 1. explain how some organisms maintain steady internal conditions that possess various structures and processes (STEM_BIO 11/12 -IVi-2) 2. describe examples of homeostasis (e. g. , temperature regulation, osmotic balance and glucose levels) and the major features of feedback loops that produce such homeostasis (STEM_BIO 11/12 -IVi-3)

(15 mins) Film Viewing https: //www. youtube. com/watch? v=-a. Rut 2 kyks. Q Buzz Session 1. What is Homeostasis? 2. How does our body maintain balance? 3. Re-Explain the example in the video about homeostasis? 4. Can you give or think of another example?

Physiology Science of body functions n Teleological vs Mechanistic views n Teleological – the why, explains purpose of a physiological process n Mechanistic – the how, explained in terms of cause and effect of physiological process n n Example: shivering n Teleological - shivering elevates a low body temperature n Mechanistic - when body temperature drops below normal, a reflex pathway causes involuntary oscillating skeletal muscle contractions which produce heat

Levels of Organization n n n Chemical Cellular Tissue Organs System Level Organismic Level

Levels of Structural Organization n Chemical Level - atomic and molecular level n n Cellular level - smallest living unit of the body Tissue level n n Group of cells and the materials surrounding them that work together on one task 4 basic tissue types: epithelium, muscle, connective tissue, and nerve

Levels of Structural Organization n Organ level - consists of two or more types of primary tissues that function together to perform a particular function or functions n Example: Stomach n n n Inside of stomach lined with epithelial tissue Wall of stomach contains smooth muscle Nervous tissue in stomach controls muscle contraction and gland secretion Connective tissue binds all the above tissues together System - collection of related organs with a common function, sometimes an organ is part of more than one system Organismic level - one living individual

Body Systems Groups of organs that perform related functions and interact to accomplish a common activity essential to survival of the whole body n Do not act in isolation from one another n Human body has 11 systems n

Body Systems

Body Systems

Homeostasis n Defined as maintenance of a relatively stable internal environment n Does not mean that composition, temperature, and other characteristics are absolutely unchanging Homeostasis is essential for survival and function of all cells n Each cell contributes to maintenance of a relatively stable internal environment n

Basic Cell Functions n n Sensing and responding to changes in surrounding environment Control exchange of materials between cell and its surrounding environment n n 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 n n Body cells are in contained in watery internal environment through which life-sustaining exchanges are made Extracellular fluid (ECF) - Fluid environment in which the cells live (fluid outside the cells) n Two components: n n n Plasma Interstitial fluid Intracellular fluid (ICF) - Fluid contained within all body cells

Homeostasis

Balancing the Internal and External Environment Cells, the fundamental units of life, exchange nutrients and wastes with their surroundings: The intracellular fluid is “conditioned by”… the interstitial fluid, which is “conditioned by” … the plasma, which is “conditioned by” … the organ systems it passes through. ICF ISF plasma organs internal environment external environment

Homeostasis n n 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

Maintenance of Homeostasis n Nervous system n n n Controls and coordinates bodily activities that require rapid responses Detects and initiates reactions to changes in external environment Endocrine system n n Secreting glands of endocrine regulate activities that require duration rather than speed Controls concentration of nutrients and, by adjusting kidney function, controls internal environment’s volume and electrolyte composition

Homeostasis Factors homeostatically regulated include n Concentration of nutrient molecules n Concentration of water, salt, and other electrolytes n Concentration of waste products n Concentration of O 2 = 100 mm. Hg and CO 2 = 40 mm. Hg n p. H = 7. 35 n Blood volume 4 -6 L and pressure 120/80 n Temperature = 37 o C

Control of Homeostasis n Homeostasis is continually being disrupted by n External stimuli n n Internal stimuli n n n heat, cold, lack of oxygen, pathogens, toxins 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

Control of Homeostasis

Homeostatic Control Systems n In order to maintain homeostasis, control system must be able to Detect deviations from normal in the internal environment that need to be held within narrow limits n Integrate this information with other relevant information n Make appropriate adjustments in order to restore factor to its desired value n

Homeostatic Control Systems n Control systems are grouped into two classes n Intrinsic controls n Local n controls that are inherent in an organ Extrinsic controls n Regulatory mechanisms initiated outside an organ n Accomplished by nervous and endocrine systems

Homeostatic Control Systems Feedforward - term used for responses made in anticipation of a change n Feedback - refers to responses made after change has been detected n n Types of feedback systems n Negative n Positive

Feedback Loops: Types n Negative feedback loop original stimulus reversed n most feedback systems in the body are negative n used for conditions that need frequent adjustment n n Positive feedback loop original stimulus intensified n seen during normal childbirth n

Negative Feedback Loop n Negative feed back loop consists of: Receptor - structures that monitor a controlled condition and detect changes n Control center - determines next action n Effector n n n receives directions from the control center produces a response that restores the controlled condition

Negative Feedback Loop

Negative Feedback Loop

Homeostasis – Negative Feedback Loop n Blood glucose concentrations rise after a sugary meal (the stimulus), the hormone insulin is released and it speeds up the transport of glucose out of the blood and into selected tissues (the response), so blood glucose concentrations decrease (thus decreasing the original stimulus).

Homeostasis of Blood Pressure n n Baroreceptors in walls of blood vessels detect an increase in BP Brain receives input and signals blood vessels and heart Blood vessels dilate, HR decreases BP decreases

Positive Feedback during Childbirth Stretch receptors in walls of uterus send signals to the brain n Brain induces release of hormone (oxytocin) into bloodstream n Uterine smooth muscle contracts more forcefully n More stretch, more hormone, more contraction etc. n Cycle ends with birth of the baby & decrease in stretch n

Role of Body Systems in Homeostasis

Glossary Maintain – keep up. n Constant – the same. n Internal – inside the body. n Environment – surroundings of the body. n Feedback - a cycle in which the output of a system “feeds back” to modify or reinforce the actions of the system in order to maintain homeostasis. n

Glossary n Negative feedback - a change causes system 1 to send a message to system 2 to restore homeostasis. When system 1 detects that system 2 has acted, it stops signaling for action and system 2 stops (turned off). n Positive feedback - the original stimulus is promoted rather than stopped. Positive feedback is rarely used to maintain homeostasis. An example of positive feedback is childbirth.

What is Homeostasis? n Body cells work best if they have the correct Temperature n Water levels n Glucose concentration n n Your body has mechanisms to keep the cells in a constant environment.

What is Homeostasis? The maintenance of a constant environment in the body is called Homeostasis

Controlling body temperature All mammals maintain a constant body temperature. n Human beings have a body temperature of about 37ºC. n E. g. If your body is in a hot environment your body temperature is 37ºC n If your body is in a cold environment your body temperature is still 37ºC n

Controlling body temperature n Animals with a large surface area compared to their volume will lose heat faster than animals with a small surface area. Volume = _______ Surface area = ______ Volume : Surface area ratio = ___________

Controlling body temperature Volume : Surface area ratio = 1: 6 For every 1 unit of heat made, heat is lost out of 6 sides Volume : Surface area ratio = 1: 5 For every 1 unit of heat made, heat is lost out of 5 sides

Controlling body temperature Volume : Surface area ratio = 1: 6 Volume : Surface area ratio = 1: 5 The bigger the Volume : Surface Area ratio is, the faster heat will be lost.

Penguins huddling to keep warm

What mechanisms are there to cool the body down? 1. Sweating n 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. n n

Sweating The skin

What mechanisms are there to cool the body down? 2. Vasodilation n Your blood carries most of the heat energy around your body. There are capillaries underneath your skin that can be filled with blood if you get too hot. This brings the blood closer to the surface of the skin so more heat can be lost. n This is why you look red when you are hot!

This means more heat is lost from the surface of the skin If the temperature rises, the blood vessel dilates (gets bigger).

What mechanisms are there to warm the body up? 1. Vasoconstriction n This is the opposite of vasodilation The capillaries underneath your skin get constricted (shut off). This takes the blood away from the surface of the skin so less heat can be lost. n n

This means less heat is lost from the surface of the skin If the temperature falls, the blood vessel constricts (gets shut off).

What mechanisms are there to warm the body up? 2. Piloerection n This is when the hairs on your skin “stand up”. It is sometimes called “goose bumps” or “chicken skin”! The hairs trap a layer of air next to the skin which is then warmed by the body heat The air becomes an insulating layer. n n n

Controlling Glucose levels n n Your cells also need an exact level of glucose in the blood. Glucose moves into the cells for cellular respiration Excess glucose gets turned into glycogen in the liver This is regulated by 2 hormones (chemicals) from the pancreas called: Insulin Glucagon

Glycogen n i l u s n I Glucose in the blood If there is too much glucose in the blood, Insulin converts some of it to glycogen the rest moves into the cells for use in cellular respiration.

Glycogen Glucagon Glucose in the blood If there is not enough glucose in the blood, Glucagon converts some glycogen into glucose.

Diabetes Some people do not produce enough insulin. n When they eat food, the glucose levels in their blood cannot be reduced. n This condition is known as DIABETES. n Diabetics sometimes have to inject insulin into their blood. They have to be careful of their diet. n

Glucose Concentration Glucose levels rise after a meal. Insulin is produced and glucose levels fall to normal again. Normal Meal eaten Time

Glucose Concentration Glucose levels rise after a meal. Diabetic Insulin is not produced so glucose levels stay high Meal eaten Time

Glycogen n i l u s n I Glucose in the blood The glucose in the But there is no Glucose blood insulinincreases. to convert concentration it into glycogen. rises to dangerous levels.

Blood Glucose Feedback Mechanism Pancreas produces Insulin Glucose into cells Out of blood Blood glucose increases ( High ) Homeostasis Blood glucose decreases (Low) Glucose out of cells Into blood Pancreas produces Glucagon

Controlling water levels The control of water levels is carried out by the KIDNEYS. n It is closely linked to the excretion of urea. n Urea is a waste product that is made when the LIVER breaks down proteins that are not needed by the body. n Urea contains the element Nitrogen. n

The kidneys “clean” the blood of waste products and control how much water is kept in the body. The waste products and water make up urine which is excreted via the ureter. “Dirty” blood enters the kidney through the renal artery. Then, several things happen to clean the blood. . .

1. Filtration Blood enters the tubule area in a capillary. The capillary forms a small “knot” near the kidney tubule. The blood is filtered so all the small particles go into the tubule. The capillary then carries on to run next to the tubule.

The kidney tubule now contains lots of blood components including: Glucose: Ions: Water: Urea:

2. Reabsorb sugar The body needs to have sugar in the blood for cells to use in respiration. So all the sugar is reabsorbed back into the capillary.

2. Reabsorb sugar The body needs to have sugar in the blood for cells to use in respiration. So all the sugar is reabsorbed back into the capillary.

3. Reabsorb water Water and ions are the next to be absorbed. It depends on how much is needed by the body.

3. Reabsorb water Water and ions are the next to be absorbed. It depends on how much is needed by the body.

Reabsorbing water If you have too little water in your blood, you will produce very concentrated urine. If you have too much water in your blood, you will produce very dilute urine. (very little water in it) (lots of water in it)

5. Excrete the waste Everything that is left in the kidney tubule is waste: • All the urea • Excess water This waste is called urine. It is excreted via the ureter and is stored in the bladder. Renal vein The “clean” blood leaves the kidney in the renal vein. Ureter

Summary of urine production Urea is a waste product made in the LIVER n Water content of the body is controlled in the KIDNEYS n Urea, water and other waste makes up URINE. n Urine travels down the URETER and is stored in the BLADDER n Urine is excreted through the URETHRA. n

n Temperature regulation, glucose level control and water level control are all examples of NEGATIVE FEEDBACK MECHANISMS.

Application Explain the Diagram