Chapter 10 - Homeostasis and thermoregulation

Question 1

Homeostasis

Answer 1

The maintenance of a constant internal environment within tolerance limits despite fluctuations in the external environment

Question 2

what is the purpose of homeostatic regulation

Answer 2

To maintain internal factors around a set normal value. When the factors deviate away from the value, homeostatic adaptations will attempt to bring the factor back to the normal value

Question 3

Metabolism

Answer 3

The sum of all the chemical reactions occurring within an organism to maintain life. Includes reactions enabling an organism’s growth, homeostasis and reproduction

Question 4

enzymes

Answer 4

A reusable, biological catalyst that lowers the activation energy of chemical reactions, making them proceed faster. It is a protein that is sensitive to factors such as temperature and pH

Question 5

negative feedback

Answer 5

feedback that reduces the effect of, or eliminates the original stimulus. eg aircon in building

Question 6

receptors

Answer 6

A cell or tissue that detects a stimulus (change in the environment). May be internal or external

Question 7

what are the five main types of receptors

Answer 7

• Chemoreceptors (chemical stimuli - aorta, carotid arteries)
• Mechanoreceptors (mechanical stimuli)
• Photoreceptors (light signals - eyes)
• thermoreceptors (change in temperature - skin, hypothalamus)
• nociceptors (pain)
• Osmoreceptors (osmotic pressure - hypothalamus)

Question 8

Interstitial fluid

Answer 8

fluid that lies in spaces between cells

Question 9

what does the nervous system consist of

Answer 9

• The central nervous system (brain and spinal cord) - receives sensory information from receptors, interprets and processes the information and produces a response
• The peripheral nervous system (sensory and motor neurons) transmit info to and from the CNS

Question 10

what is the pathway of nerve impulses

Answer 10

Follow sensory neurons from source of stimulation, via the PNS to the CNS. Interconnecting neurons located in the CNS relay the electrical impulses from the sensory neurons to the appropriate motor neurons. From the CNS, motor neurons relay information signals via the PNS to the effectors.

Question 11

Afferent

Answer 11

From receptor to CNS

Question 12

Efferent

Answer 12

From the CNS to the effector

Question 13

What are the four differences between the actions of nerves and hormones

Answer 13

• Nervous responses are more rapid than hormonal as nerve impulses travel rapidly along nerve fibres while hormones are transported in the bloodstream
• Nerve impulses bring about an immediate response which lasts for a short time. Hormones are slower acting but can last a considerable time
• Nervous messages are an electrochemical change that travels along membrane of neuron. Endocrine messages are hormones that are transported by blood
• Nervous impulses travel along a nerve fibre to a specific part of the body and often influence just one effector. Hormones travel to all parts of the body and effect a number of different organs

Question 14

example of hormone regulation in humans

Answer 14

ADH secreted by the pituitary gland effecting the kidneys, stimulating the reabsorption of water, helping maintain an appropriate water balance in the body

Question 15

example of hormone regulation in other organisms

Answer 15

Female ring doves coo during courtship to stimulate the release of the hormones that result in egg development.

Question 16

what are the three types of neurons on their function

Answer 16

• Sensory (receptors –> CNS)
• Interconnecting (Sensory neurons –> motor neurons)
• Motor (CNS –> effector)

Question 17

examples of factors that can vary in the environment

Answer 17

Temperature, water availability, nutrients, oxygen and carbon dioxide

Question 18

Positive feedback

Answer 18

feedback model that strengthens and intensifies the effects of the stimulus. EG, blood clotting, childbirth, development of frogs and toads

Question 19

Five parts of a negative feedback model

Answer 19

• Stimulus: change in internal or external environmental factors. Involves a deviation away from normal value
• Receptor: Cell or tissue that detects the stimulus. May be internal or external
• Modulator (coordinating centre): Structure that receives messages from receptors (via sensory neurons), coordinates a response, send instruction to effector
• Effector: Muscle or gland that receives message from control centre and carries out the response
• Response: the action of the effector that counteracts the stimulus
• Negative feedback: factor returns to normal value

Question 20

set point

Answer 20

optimal value for an internal variable such as temperature

Question 21

Tolerance ranges

Answer 21

the range of a factor within which an organism can function and reproduce. If factors go outside of this range, it may be fatal for the organism. LEARN DIAGRAM

Question 22

Optimal range

Answer 22

the narrower range, within an organism’s tolerance range for a particular factor at which the organism functions best

Question 23

Zone of physiological stress

Answer 23

The zone that is outside the optimal range but inside tolerance range. Is not optimal but survival is possible

Question 24

Zone of intolerance

Answer 24

the zone that is outside the tolerance range for survival

Question 25

Internal factors that have a tolerance limit

Answer 25

temperature, nitrogenous waste, water, salts and gases

Question 26

Increase in temperature

Answer 26

- Enzymes denature, leading to slow cell metabolism - Cells can die - Membranes such as cell membranes become too fluid, allowing some unwanted substances into or wanted substance out of cells - Rate of photosynthesis slows

Question 27

Decrease in temperature

Answer 27

- Decrease in the activity rate of enzymes, which results in a decrease in metabolic rate - the activity of some other proteins decreases - Membranes such as cell membranes become rigid (instead of fluid), slowing cell membrane transport of substances - mammals can suffer hypothermia, may lose limbs and cannot reproduce

Question 28

increase in Nitrogenous waste

Answer 28

- As nitrogenous wastes build up, they increase in concentration and become more toxic - An increase in ammonia (a base) in the blood can lead to an increase in the pH of body fluids - Enzyme activity can decrease, enzymes will denature if the pH gets too high. - High levels of nitrogenous waste can affect water balance. Cells may lose water to dilute the waste, affecting water homeostasis

Question 29

Nitrogenous waste pathway

Answer 29

Ammonia (highly toxic) --> urea (moderately toxic) --> uric acid (least toxic, little water, energy cost)

Question 30

Hypothermia

Answer 30

A state in which an organism's internal temperature drops below the lower tolerance limit

Question 31

Hypotonic

Answer 31

(water enters cell) At a lower concentration than another solution. When a cell is surrounded by a hypotonic solution, water moves out of the cell via osmosis to dilute the cell, so the cell swells. (animal cells which have no cell wall sometimes burst)

Question 32

Hypertonic

Answer 32

(water leaves cell) At a higher concentration than another solution. When a cell is surrounded by a hypertonic solution, water moves out of the cell via osmosis to dilute the surroundings, so the cell shrinks

Question 33

Isotonic

Answer 33

At the same concentration as another solution. If a cell and its surrounding solution are isotonic, there is no net movement of water between them and the cell maintains a constant volume

Question 34

Plasmolysis

Answer 34

The state of a plant cell in which the cell membrane has pulled away from the cell wall due to water moving out of the cell

Question 35

Physiological adaptations

Answer 35

Related to how an organism, system, organ, tissue or cell functions.

Question 36

Structural adaptations

Answer 36

related to an organism's shape, specialised features and size.

Question 37

Behavioural adaptions

Answer 37

Relate to how the organism acts

Question 38

Physiological processes that maintain an organism's internal environment within tolerance limits

Answer 38

- Reducing carbon dioxide concentration by increasing breathing rate. This passes more blood through lungs, releasing carbon dioxide and blood is oxygenated faster. - The changed internal temperature is detected by thermoreceptors in the hypothalamus which signals to the sweat glands to activate

Question 39

Structural adaptations that maintain an organism's internal environment within tolerance limits

Answer 39

Thick insulating fur that keeps a bear warm, the thin flat leaves of a tree that maximise sunlight capture, the vast capillary network over the alveoli that creates a large surface area for gas exchange

Question 40

Behavioural adaptations that maintain an organism's internal environment within tolerance limits

Answer 40

Burrowing in mud helps desert frogs avoid drying out. In humans, removal of clothing or moving to shade.

Question 41

hyperthermia

Answer 41

A state in which an organism's internal temperature rises above the upper tolerance limit

Question 42

what are endotherms

Answer 42

An animal that uses metabolic processes to generate its own heat to maintain its internal temperature within the tolerance range. Endotherms also have a range of adaptations that serve as mechanisms for controlling heat gain or loss.

Question 43

examples of endotherms

Answer 43

Birds, mammals, some reptiles, fish and insects

Question 44

what are ectotherms

Answer 44

An animal whose body temperature is determined by the external environment. Ectotherms rely on structures and behaviours for thermoregulation. Ectotherms may obtain heat from the sun or from objects in their surroundings, which means their body temperature fluctuates with that of the external environment

Question 45

examples of ectotherms

Answer 45

Amphibians, some reptiles, fish, most invertebrates

Question 46

why do scientists avoid using the terms 'warm blooded' and 'cold blooded'

Answer 46

Because they are misleading. For example, if an ectothermic lizard is basking in the sun, its body temperature may be 'warmer' than an endothermic seal that is using faster metabolism to warm up

Question 47

Costs of endotherms

Answer 47

To maintain a stable internal temperature, they may have a higher metabolic rate, need to spend more energy to maintain a higher metabolic rate. Results in higher food requirements and more time spent finding food

Question 48

costs of ectotherms

Answer 48

Body temperature is dependent on external temperature. These animals are limited to living in environments with less extreme temperatures. They cannot tolerate very high or very low external temperatures

Question 49

benefits of endotherms

Answer 49

Body temp is independent of external temperature. This enables endotherms to live in more extreme environments. They can be active at night or more often during day and cold weather. Being more active may reduce chance of predation

Question 50

benefits of ectotherms

Answer 50

Their heat source is mainly the environment, so there are lower energy requirements for these animals. Therefore they need to consume less food, spend less time hunting, can tolerate larger fluctuations in their internal body temperature compared with endotherms

Question 51

Temperature gradient

Answer 51

Produced when two objects in close proximity have different temperatures due to different amounts of heat energy. this causes heat to travel from the hotter object to the colder object

Question 52

evaporative cooling

Answer 52

A mechanism of heat transfer from an organism to its surroundings. Water on the surface of the skin draws heat energy from the body for the change of state from liquid water to vapour. The vapour diffuses into the surrounding air, taking heat away from the body and cooling the body down