homeostasis/thermoregulation/osmoregulation

Course Objective & Description

Tick when done

Homeostasis: procees of keeping the environment inside the body constant.

1

Describe the components of a feedback system – stimulus, receptor, modulator (control centre), effector, response, feedback (negative).

Stimulus: a change in the environment.

Receptor: the stimulus is detected by sensory cells.

Message: sensory cells generates a message in the form of a nerve impulse of hormone.

Modulator: a control centre processes the message receives from the receptor.

Message: a new message is sent out by modulator.

Effector: muscles or glands receives the message from the modulator.

Response: the effector organ bring about an appropriate reaction.

Feedback: response changes the orginal stimulus.

Aspects of internal environment:

▹    Core body temperature

▹    pH and concentration of dissolved substances in body fluids

▹    Concentration of glucose in the blood.

▹    Concentration of oxygen and carbon dioxide in the blood and other body fluids

▹    Blood pressure

▹    Concentration of metabolic wastes

Homeostasis Mechanism: work to maintain homeostasis:

 main sensory and controlling body systems:

-       Nervouse system: fast process

-       Hormonal system: slower

*both operate through feedback systems.

Feedback loops: are cicurlar in which the body respond to a stimulus, with the response altering original stimulus. Can be negative or positive depending on whether the response decreases or increases original stimulus.

Thermoregulation

2

Describe how heat is generated in the body.

Gained from surrounding by conduction and radiation

Heat from body processes (metabolism), especially respiration of liver and muscle cells.

 Radiation: transfer of heat from one object to another without direct contact: e.g. gain of heat when sitting in the sun or loss of heat from the body in a cold room.

Conduction: heat transfers to another object through physical contact(energy passes fro molecule to molecule when in contact). E.g. placing hands in warm water to heat them up.

-       Body processes – metabolism (cell respiration and excerise.

-       Heat gained from the environment/ conduction/radiation.

-       Illness.

-       Increase in secretion of adrenaline from the adrenal medulla.

-       Stress or emotions.

-       Increased thyroxine levels.

-       Medications.

3

Describe how heat can be lost from the body.

Radiation, conduction and convection to surroundings. Evaportation of water from skin and lungs; warm air breathed out; warm unrine and faeces.

-       Evaporation- water from the skin and lungs.

-       Warm air breathed out.

-       Voiding of warm urine and faeces.

-       Radiation of body heat to the cooler surroundings.

-       Heat loss to the environment- conduction and convection.

4

State that the normal body temperature of humans is approximately 36.7⁰C. = homeothermic

cells function optimally at this temperature- increased body tmep acan cause nerve malfunction and change the structural integrity of protein and enzymes.

-       A constant body temperature is achieved by a balance between heat gain and heat loss.

5

Describe the location of the thermoreceptors in the body (both peripheral and central).

Central: located in the hypothalamus – detects the temperature of the internal environment.

Peripheral: located in the skin and in some mucous membranes – detects temperature changes in the external environment and sends this information to the hypothalamus.

6

Describe how heat can be transferred by radiation, conduction and convection.

Radiation: transfer of heat from one object to another without direct contact: e.g. gain of heat when sitting in the sun or loss of heat from the body in a cold room.

Conduction: heat transfers to another object through physical contact(energy passes fro molecule to molecule when in contact). E.g. placing hands in warm water to heat them up.

Convection: flow of warm, less dense air upwards, which is replaced by cooler, more dense air. The faster the flow, the faster the cooling. E.g. electric fans help to move warm air away from our skin to be replaced with cool air.

7

Explain how evaporation of sweat can lead to cooling the body.

Heat is removed from the body when liquid is converted to a vapour.

It absorbs heat from the body, causing a cooling effect  because of the process of changing from a liquid to a gas requires energy.

8

Describe how the body responds to a fall in body temperature. (Include both physiological* and behavioural responses.)

Physiological:

The body starts to shiver and any blood vessels near the skin vasoconstrict. Increase in metabolic rate.

Behavioural:

We wear thicker warmer clothes, take warm showers, decrease body surface area(by hudling in a ball), sit in front of a heater/fire.  Increase activity.

9

Describe how the body responds to a rise in body temperature. (Include both physiological* and behavioural responses.)

Physiological:

The body starts sweatin increase heat loss by evaporative cooling, the blood vessels in the skins surface vasodilate- increasing heat loss vie radiation.

Behavioural:

Wear less/lighter clothes, take cool shower, sit in shade, fan and reduce voluntary activity. Spreading out limbs(increasing body surface area.

10

Explain the terms vasodilation and vasoconstriction.

Vasodilation: is the widening of blood vessels, allowing for increase blood flow .

Vasoconstriction: is the narrowing of blodd vessels, allowing for reduction of blood flow through the blood vessels.

11

Describe the relationship between the level of thyroxine and body temperature.  ******

Thyroid hormone plays an important role in keeping bodily temperature stable when the outside temperature changes. In the cold, an increase in thyroid hormone leads to an increase in basal metabolic rate and heat generation. This is reversed in the heat

12

Explain why piloerection is ineffective in humans as a means of preventing body temperature from falling:

As humans have relativel sparse body hair, especially in comparison to our early human ancestors or other mammals adapted to cold climates. The amount and thickness of body hair in huams are not sufficient to provide significant insulations against cold temperatures.

The thin layer of body hair we possess does not provide enough insulation to significantly affect body temperature.

Glucose (Blood Sugar) Regulation (Chapter 5 and Chapter 8)

13

Explain the relationship between glucose and glycogen.

-       Glycogen is storen in the liver and skeletal muscles.

-       Glucose is a simple monosaccharide.

-       Glycogen is broken down into glucose and glucose is created into glycogen.

14

Explain the role of the liver in the regulation of blood sugar

-       Liver converts glucose into glycogen for storage.

-       Converts glycogen into glucose for release into the blood.

-       * most of the livers blood supply comes through the heptic portal, (brings blood directly from stomach, spleen, pancrease, and small and large instestines.

-       The heptic portal vein carries the glucose to the liver.

Glucose may be:

-       Be removed from the blood by the liver to provide energy for liver functioning Be removed by the liver and/or muscles and converted into glycogen for storage

-       Continue to circulate in the blood, available for body cells to absorb and use as a source of energy (cellular respiration)

-       Be converted into fat for long-term storage it it is in excess of that required to maintain both normal blood sugar and tissue glycogen levels

Glycogensis(lowers blood glucose levels(insulin)). Glucose into glycogen – storage in liver and skeletal muscle cells.

Glycogenolysis: rasies blood glucose levels (glucagon): glycogen into glucose – into the bloodstream.

Gluconeogenesis: raises blood glucose levels (glucagon): fats and amino acids into glucose – into the bloodstream.

15

Describe the possible fate of glucose absorbed in the small intestine.

Digestion (Breaking Down Carbohydrates into Glucose)

• Enzymes involved: 

  • Salivary and pancreatic amylase → Break down starch into monosaccharides 

• End product: Glucose 

Absorption into the Bloodstream

• Glucose is absorbed through the walls of the small intestine (ileum) into the capillaries of the villi.

• This happens via active transport and facilitated diffusion: 

  • Uses active transport (with sodium) to move glucose into intestinal cells.

  • Moves glucose from the epithelial cells into the bloodstream via facilitated diffusion.

Transport to the Liver via the Hepatic Portal Vein

• Once in the bloodstream, glucose travels to the liver via the hepatic portal vein.

• In the liver, glucose may: 

  • Be stored as glycogen (glycogenesis).

  • Remain in the bloodstream for use by body cells.

  • Be converted into fat for long-term storage if in excess.

Regulation by Insulin and Glucagon

• After absorption, blood glucose levels rise, triggering the pancreas to release insulin.

• Insulin allows glucose to enter body cells for cellular respiration or storage.

• When blood glucose levels drop, glucagon is released to break down glycogen and release glucose into the blood.

Summary

• Glucose is absorbed in the small intestine via active transport & facilitated diffusion.

• It enters the bloodstream and travels to the liver via the hepatic portal vein.

• Insulin regulates glucose uptake into cells, while glucagon prevents hypoglycemia.

16

Describe the regulation of blood sugar levels by the hormones insulin and glucagon*.

Glucagon: raises blood glucose level:

-       Achieved though glycogenolysis and gluconeogensesis.

-       Insulin: lowers blood glucose level.

-       Achieved through glycogenesis,

-       Lipogenesis: promotes protein synthesis- requiring energy = blood glucose utilized.

-       Accelerating the transport of glucose from the bood into the body cells, especially those of the skeletal muscles.

17

Define the following terms: glycogenesis, glycogenolysis and gluconeogenesis.

-       ‘genesis’ = to make/to begin

-       ‘lysis’ = to split apart/breakdown

-       Glycogenesis – to make glycogen (glucose --> glycogen) INSULIN

-       Gluconeogenesis – to make glucose from non- carbohydrate sources (amino acids --> glucose or fats --> glucose) GLUCAGON

-       Glycogenolysis – to breakdown glycogen (glycogen --> glucose) GLUCAGON

18

Describe the effects of adrenalin and cortisol (a glucocorticoid) on blood sugar concentration.

-       The adrenal cortex, under the influence of ACTH produced by the anterior pituitary gland, secretes glucocorticoids- cortisol.

-       The adrenal medulla, under the control of the autonomic nervous system secretes adrenaline/noradrenalines.

Cortisol: is a glucocortiod.

-       Increases blood sugar levels.

o   Stimulates the conversion of glycogen into glucose(glycogenolysis)

o   Increases the rate at which amino  acids are converted into glucose, in the liver (gluconenogenesis).

o   Proteins are broken down in the muscle cells and the amino acidsa are transported to the liver and converted into glucose.

-       Adrenalin increases blood sugar levels.

o   Stimulates the conversion of glycogen into glucose (gluconenogenesis).

o   Lactic acid is converted to the cells surface become more sensitive.

19

Explain the term hyperglycaemia and the possible causes:

Hyperglycemia: abnormally high blood glucose level

Symptoms:

-       Being excessively thirsty

-       Passing more urine

-       Feeling tired and lethargic

-       Always feeling hungry

-       Having cuts that heal slowly

-       Itching, skin infections

-       Blurred vision

-       Weight change (Type 1 – weight loss)

20

Distinguish between diabetes type 1 and type 2 (Chapter 8 pages 207 - 209.)

• Diabetes is a disease characterized by abnormally high levels of blood glucose.

• Diabetes results from the body being unable to maintain the blood sugar level in homeostatic balance.

• Neither form of diabetes can be cured; however, both types can be managed through diet, exercise and the use of insulin

• There are several different types of diabetes. The most common are:

• Diabetes mellitus – Type 1 (Insulin dependent)

  • Also known as early onset diabetes because it often occurs in young people under the age of 30.

  • Occurs because there is a fault in the immune system that destroys the beta cells. The pancreas therefore stops making insulin.

  • Treated with daily injections of insulin.

  • Life-threatening if untreated.

• Diabetes mellitus – Type 2 (Adult onset)

  • Also known as late onset diabetes because it typically occurs in older people under the age of 30.

  • Type 2 is the most common form of diabetes (85-90%).

  • Occurs because the body cells become less responsive to insulin.

  • Treated by dietary control, exercise and insulin injections.

  • Life-threatening if untreated.

21

Explain how gene therapy and synthetic hormones can be used to treat diabetes mellitus

TYPE 1 DIABETES

• Insulin-dependent diabetes (juvenile diabetes)

• Usually begins in childhood 

• 10-15% diabetics suffer from type 1.

• Fault in person’s immune system causing the destruction of the Beta Cells in the Islets of Langerhans of the pancreas

• Person does not produce insulin 

• Person cell’s usually respond to insulin normally so the disease can managed by giving the person insulin

• Insulin taken by mouth will be digestive in alimentary canal therefore it must be injected (not a cure

• Long term effects of this disease can be: kidney failure, heart attack, stroke, amputations, blindness or nerve damage

TYPE 2 DIABETES

• Non-insulin-dependent or adult onset diabetes

• Usually develops in people > 45years

• Increasing in numbers of younger people

• Type 2 diabetics can produce insulin but their cells do not respond to it

• Lifestyle disease.

• Lifestyle factors that increase risk of developing Type 2 diabetes:

  • Lack of physical exercise

  • Being overweight or obese

  • A diet regularly high in fat, sugar, salt and low in fibre

  • High blood pressure

  • High blood cholesterol

  • Smoking

• Develops gradually, often no symptoms or they are not noticed

• Cells do not take up glucose (don’t respond to insulin)

• No cure, diagnosis early leads to more chance of successful management

  • Careful diet, regular exercise, maintain healthy weight, monitor blood glucose, sometimes medication

• If untreated: heart disease, stroke, kidney disease, eye problems, nerve damage and skin and foot problems

Osmoregulation (Chapter 6)

22

Distinguish between intracellular fluid, blood plasma and intercellular fluid (tissue fluid/interstitial fluid).

Intracellular Fluid (Cytosol) 

• Fluid contained within the cells of an organism 2/3 of total body water 

Extracellular Fluid 

• Fluid that is outside the cells of an organism 1/3 of total body water 

Plasma 

• 1/4 of extracellular fluid The fluid part of the blood 

Intercellular Fluid (Tissue Fluid/Interstitial Fluid) 

• 3/4 of the extracellular fluid 

• Lymph, cerebrospinal fluid, synovial fluid in joints, fluids of eyes and ears, fluid in the chest and abdominal cavities and around the heart, fluids of the alimentary canal, kidney filtrate

23

Explain how nutrients, wastes and water move between cytoplasm and vascular fluids. (Hint: explain the role of tissue fluid and the process of diffusion.)

Role of tissue fluid:

-       Tissue fluid surrounds body cells and acts as a medium for exchanging substances between capillaries (vascular fluids) and the cytoplasm of cells.

-       It forms when plasma leaks out of capillaries due to hydrostatic pressure and provides nutrients to cells.

Nutrient movement (oxygen, glucose, amino acids, etc).

-       Oxygen and nutrients diffuse from capillaries into tissue fluid and then into cells following a concentration gradient.

-       Glucose and amino acids may also be transported by facilitated diffusion or active diffusion.

Waste removal ( carbon dioxide, urea, etc):

-       Metabolic wastes like carbon dioxide and yurea move from cells into tissue fluids and then diffuse into capillaries, where they are transported for excretion.

-       Carbon dioxide diffuse into the blood, where it dissolves in plasma or binds to hemoglobin before being transported to the lungs.

Water movement (osmosis):

-       Water moves by osmosis from areas of low solute concentration (tissue fluid) to areas of hugh solute concetration (inside cels or blood plasma).

-       The lumphatic systems help return excess tissue fluid to the bloodstream, preventing swelling (edema).

24

Define excretion and list the excretory structures and their products:

Excretion:

• the removal from the body of the waste products of metabolism.

• Several organs are involved: lungs (CO2), sweat glands (salts, urea and lactic acid), alimentary canal (bile pigments) and the kidneys (urea).

• The kidneys are the principal excretory organs

• Maintain constant concentration of materials in body fluid

• Removes and excretes toxic nitrogenous waste (urea, uric acid, creatinine)

25

Describe the structure of the nephron.

26

Outline very briefly the processes involved in the formation of urine – filtration, selective reabsorption and tubular secretion.

• Blood enters the glomerulus under high pressure 

Filtration 

• Occurs in the renal capsule 

Selective Reabsorption 

• Mainly in the proximal convoluted tubule – some water and salts are reabsorbed in the loop of Henle and the distal convoluted tubule 

Tubular Secretion 

• In the proximal convoluted tubule and the distal convoluted tubule 

27

Describe where in the nephron water reabsorption occurs

28

Describe the role of ADH (antidiuretic hormone) in maintaining the water balance*.

• Stimulus- Dehydration

  • Decreased blood volume

    • reduced blood pressure

    • increased osmotic pressure

• Receptor

  • Osmoreceptors in hypothalamus → (also activates thirst reflex)

• Modulator

  • Hypothalamus nerve signal to posterior pituitary gland

  • ADH released into bloodstream 

• Effector 

  • DCT and collecting duct

    • Increases permeability of above structures

• Response

  • More water reabsorbed from filtrate

29

Describe the role of the thirst reflex in maintaining the water balance:

-       Water concentration of blood plasma decreases; osmotic pressure of the blood is increased; mouth becomes dry

-       Osmoreceptors in the thirst center of the hypothalamus are stimulated

-       Person feels thirsty

-       Person responds to the feeling of thirst by drinking

-       Water drunk is absorbed into the blood from the alimentary canal

-       Water leaves the blood and the extracellular and intercellular fluids return to their normal concentrations

30

Explain the causes and consequence of dehydration:

• When 2% or more of body fluid lost, can be due to sweating, vomiting or diarrhoea. 

• In elderly, thirst reflex less effective. 

• Can lead to severe thirst, head aches, low blood pressure, dizziness and 
  head aches.

31

Explain the consequences of water intoxication.

• Body fluids become diluted and cells take in extra water due to osmosis. 

• Can happen if you lose lots of water through sweating and replace with 
  plain water. Lightheadedness , vomiting and collapse. 

Gas Regulation (Chapter 6)

32

Write a word equation for cellular respiration.

33

Name the muscles that are responsible for ventilation and name the nerves that stimulate them.

34

Describe the relationship that exists between the concentration of CO₂ in the plasma and the concentration of hydrogen ions (pH) - see equation page 140.

35

Name the chemoreceptors that are stimulated when the oxygen concentration decrease dramatically.

36

Describe how a very low concentration of oxygen in the blood can affect the breathing rate.

37

Describe the regulation of carbon dioxide in the blood (and pH of blood plasma)*.

38

Describe the difference between quiet and active breathing.

39

Explain why it is dangerous to hyperventilate before swimming under water.