16.1 - Principles of homeostasis

Question 1

What is the definition of homeostasis?

Answer 1

The maintenance involving physiological control systems that maintain the internal environment within restricted limits

Question 2

What is the internal envirnoment of an organism?

Answer 2

It is made up of tissue fluid

Question 3

What does the tissue fluid do?

Answer 3

Bathe each ce;;,supplying nutrients and removing wastes

Question 4

Why is it importance to maintain this tissue fluid at optimum levels?

Answer 4

• Protects the cells from changes in eztenral environment, therby giving the organism a degree of independence

Question 5

What does homeostasis involve?

Answer 5

Trying to maintain the chemical make-up, volume and other features of the blood and tissue fluid within restrictied limits

Question 6

What does homeostasis ensure?

Answer 6

Cells of the body are in environment that meets their requirements and allows them to function normally despite external changes

(this does not mean that there are no changes)

Question 7

What is homeostasis abiility?

Answer 7

There is continous fluctuation brought by the variation in internal and external conditions, such as changes in temperature, pH and water potential

This changes occur around optimum point

Its ability to reutnr to optimum point so maintain organisms in balanced equilibrium

Question 8

The importance of homeostasis

What are enzymes?

Answer 8

• Control the biochemical reactions within a cell and other proteins
• e.g such as channel proteins are sensitive to changes in pH and temperature

Question 9

What happens if there is any changes to the factors?

Answer 9

This will reduce the rate of enzyme

or

may even prevent them from working altogether

eg by denaturing them

even small fluctuations in temperature or pH can impair the ability of enzymes to carry out their roles effectively

Question 10

Why is it important to maintain a fairly constant internal enivornment for enzymes?

Answer 10

So reactions can take place at a suitable rate

Question 11

What happens if water potential changes?

Answer 11

• Changes of water potential of blood and tissue fluids may cause cells to shrink and expand(even to bursting point) as a result of water leaving or entering by osmosis
• In both instances - cells cannot operate normally

Question 12

Why is maintaing water potential in organisms important?

Answer 12

• The maintenance of constant blood glucose concentration is essential for constant water potential
• Constant blood glucose concentration also ensures a reliable source of glucose for respiration by cells

Question 13

Why is it important for organisms ability to maintain a constant internal environment?

Answer 13

• More independent of changes in external environment
• May have wider geographical range
  
  • greater chance of finding food,shelter etc.
• These type of mammals are found in hot arid deserts to cold frozen polar regions e.g penguins

Question 14

Series of control mechanisms

control of self-regulating system features

Answer 14

1. Optimum point
2. Receptor
3. Coordinator
4. Effector
5. Feedback mechanisms

Question 15

What is the first step of control mechanisms?

Answer 15

1. Optimum point is the point at which system operates best, this is monitored by a receptor

Question 16

What is the second step of control mechanisms?

Answer 16

1. Receptor which detects any deviation from the optimum point (i.e. stimulus) and informs the coordinator

Question 17

What is the third step of control mechanisms?

Answer 17

• Coordinator, which coordinates information from receptors and sends instructions to an approriate effector

Question 18

What is the fourth step of control mechanisms?

Answer 18

• Effector, often a muscle/gland which brings about the changes needed to return the system to an optimum point
• This returns to a normality creates a feedback mechanism

Question 19

What is the fifth step of control mechanisms?

Answer 19

• Feedbackmechanisms - by whcih a receptor responds to a stimulus created by change to the system brought along by the effector

Question 20

What is negative feedback?

Answer 20

• Change produced by the control system leads to a change in the stimulus detected by the receptor and turns the system off

Question 21

When does positive feedback occur?

Answer 21

• When there is a deviation from an optimum causes changes in result in an even greater deviation from the normal one

Question 22

What is an example of positive feedback?

Answer 22

• Stimulus leads to a small influx of sodium ions
• Influx increases the permeability of the neurone membrane of sodium ions
• More ions enter causing a further increase in permability and even more rapid entry of ions
• (stimulus brings about large and rapid response)

Question 23

What can change in water potential also effect?

Answer 23

Concentration of enzxyme and substrates as well as rate of reaction

Question 24

Why do control systems have many receptors and effectors?

Answer 24

• Allows them to have separate mechanisms that each produce a positive movement towards optimum
• Allows a greater degree of control of particular cotrol factor being regulated

Question 25

What is a general feature of homeostasis?

Answer 25

* Seperate mechanisms that control depatures from different directions from original state

Question 26

An example Importance of information is provided by receptors is analysed by the coordinator before action is taken

Answer 26

* Temperature receptors in skin may signal that the skin itself is cold and the body temperature should be raised * However, information from regions in the hypothalamus in brain indicate blood temperature is above normal * May happen during strenous exercise when blood temperature rises but sweating cools down the skin * Control centre must coordinate the action of effectors * e.g sweatubg would be less effective in cooling the body if not accompaind by vasodilation

Question 27

What are endotherms?

Answer 27

Animals such as birds and mammals derive most of their heat from metabolic activities that take place inside their bodies

Question 28

What are ecotherms?

Answer 28

Some animals obtain an proportion of their heat from sources outside of their bodies namely the enivrionment

Question 29

Why do ectoherm's body temperature fluctuate with the environment?

Answer 29

Many ecotherms gain heat from the environment

Question 30

How do ecotherms adapt to the environment?

Answer 30

Control body temperature by adapting their behaviour to changes in external temperature

Question 31

How do ecotherms exposing themselves to the Sun

Answer 31

* In order to gain heat lizards orienate themseleves so the maximum surface area of the body is exposed to the warning rays of the Sun

Question 32

What are examples of ecotherms?

Answer 32

* Reptiles e.g lizards

Question 33

How do ecotherms adapt by taking shelter?

Answer 33

* Lizards will shelter in the shade to prevent over-heating when the Sun's radiation at peak * At night they retreat into burrows in order to reduce heat loss when external temperature i slow

Question 34

How do ecotherms adapt by gaining warmth from the ground?

Answer 34

Lizards will press their bodies against areas of hot ground to warm tehmselves up When required temperature is reached, they raise themseleves off the ground on their legs

Question 35

What do most endotherms gain most of their heat from?

Answer 35

* Internal metabolic activities

Question 36

Do their body temperature stay the same despite fluctuates in the external environment?

Answer 36

Yes

Question 37

What is the importance of mammals having small surface area to volume raito in cold climates?

Answer 37

* They tend to have a small low surface area to volume raito * In warmer climates they have ears , thick fur or fat layers to insulate the body

Question 38

How do mammals adapt in cold climates using vasoconstriction?

Answer 38

* The diamter of the arterioles near the surface of the skin is made smaller * This reduces the volume of the blood reaching the skin surface through the capillaries * Most blood entering the layers of fat and so loses lttle heat to the environment

Question 39

How do mammals adapt in cold climates using shivering?

Answer 39

* The muscles of the body undergo involuntary rhythmic contractions that produce metabolic heat

Question 40

How do mammals adapt in cold climates raising of hair?

Answer 40

The hair erector muscles in the skin contract, raising the hairs on the body This enables a thicker layer of still air , which is a good insulator to be trapped next to skin , insulation and conversing heat in mammals with thick hair

Question 41

How do mammals adapt in colder climate by having an increased metabolic rate?

Answer 41

* In cold conditions, more of the hormones that increase metabolic rate are produced * Respiration is increased so more heat generated

Question 42

How do mammals adapt in cold climates decreased sweating?

Answer 42

* Sweating is reduced * or * ceases altogether in cold conditions

Question 43

How do mammals adapt in cold climates using behavioural mechanisms?

Answer 43

* Sheltering from the wind, basking in the sun and huddling altogether help animals to mantain core body temperature

Question 44

How do mammals in hot climates adapt using vasodilation?

Answer 44

* The diameter of the arterioles near the surface of the skin become larger * Allows warm blood to pass close to the skin surface through capillaries * Heat from body is then radiated away from the body

Question 45

How do mammals in hot climates adapt using increased sweating?

Answer 45

* To evaporate water from the skin surface requires energy in the form of heat * In relatively hairless mammals e.g humans is an effective way of losing heat * Mammals with fur, cooling achievged by evaporation of water from mouth and tongue during panting * High specific latent vaporisation makes water sweating an effective way to lose heat

Question 46

How do mammals in hot climates adapt lowering the body hair?

Answer 46

* The hair erector muscles in skin relax and elasticity of skin causes them to flatten against the body * This reduces the thickness of the insulating layer and allows more heat to be lost to the environment when the internal temperature is higher than external

Question 47

How do mammals in hot climates adapt using behavioural mechanisms?

Answer 47

* Avoiding the heat of the day by sheltering in burrows and seeking out shade to help to prevent the body temperature from rising