Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology A-Level > Homeostatic Control, Excretion and Thermoregulation (Chapter 14) > Flashcards

Homeostatic Control, Excretion and Thermoregulation (Chapter 14) Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What is homeostasis?

A
  • The maintenance of internal conditions despite variations in the external environment, within narrow limits us
  • It uses control systems in the body to keep internal conditions near constant
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does homeostasis require?

A
  • Information about the conditions inside the body and the surroundings, which are detected by sensory cells
  • This information to be transferred between different parts of the body
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Name 6 physiological factors controlled in homeostasis in mammals

A

1) core body temperature
2) metabolic wastes especially CO2 and urea
3) blood pH
4) blood glucose concentration
5) water potential of blood
6) concentration of CO2 and O2 (respiratory gases) in the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the internal environment of an organism?

A

All conditions inside the body/conditions in which the cells function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the immediate environment for a cell?

A

The tissue fluid that surrounds it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are 3 features of tissue fluid that influence cell activities?

A

1) temperature
2) water potential
3) concentration of glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does temperature influence cell activities?

A
  • Low temperatures slow down metabolic reactions

- At high temperatures, proteins (incl enzymes) are denatured and cannot function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How does water potential influence cell activities?

A
  • If the water potential decreases, water may move out of cells by osmosis, causing metabolic reactions in the cell to slow or stop
  • If the water potential increases, water may enter the cell, causing it to swell and maybe burst
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How does the concentration of glucose influence cells activties?

A
  • Glucose is the fuel for respiration ∴ lack of it causes respiration to slow or stop, depriving the cell of an energy source
  • Too much glucose may cause water to move out of the cell by osmosis, again disturbing the metabolism of the cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How does homeostasis work?

A

By controlling the composition of blood and ∴ the composition of tissue fluid (using different control mechanisms for different aspects of the blood and tissue fluid)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What do most control mechanisms in living organisms use to maintain homeostatic balance?

A

A negative feedback control loop, involving a receptor and effector (muscles and glands)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How does negative feedback work?

A

1) the receptor detects stimuli (external or internal) that are involved with the condition being regulated
2) these receptors send information (input) about the changes they detect through to nervous system to a central control in the brain or spinal cord
3) the central control instructs an effector to carry out an action (output)
4) continuous monitoring of the factor by receptors produces a steady stream of information to the control centre that makes continuous adjustments to the output
5) ∴ the factor fluctuates around a particular set point (ideal value)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the aim of negative feedback?

A

To keep changes in the factor within narrow limits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the actions of negative feedback called and why?

A
  • Corrective actions because their effect is to correct and reverse the change
  • An increase in the factor results in something happening that makes the factor decrease and vice versa
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why do homeostatic mechanisms involve negative feedback?

A
  • Because it minimises the difference between the actual value of the factor and the set point
  • The factor never stays exactly constant, but fluctuates a little above and below the set point
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What two coordination systems in the body transfer information between different parts of the body?

A

Nervous and endocrine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How is information transferred in the nervous system?

A

Information in the form of electrical impulses is transmitted along neurones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How is information transferred in the endocrine system?

A

Chemical messengers called hormones that travel in the blood, in a form of long-distance cell signalling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is thermoregulation?

A

The control of body temperature, involving both the endocrine and nervous system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is excretion?

A

The removal of unwanted products of metabolism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What two excretory products are formed in humans in much greater quantities than others?

A

1) CO2

2) Urea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How is CO2 an excretory product?

A

1) it is produced continuously by cells respiring aerobically
2) the waste CO2 is transported from the respiring cells to lungs in the bloodstream
3) gas exchange occurs within the lungs and CO2 diffuses from the blood into the alveoli - it is excreted in the air we breathe out

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How is urea an excretory product?

A

1) it is produced in the liver from excess amino acids and transported to the kidneys, in solution in blood plasma
2) kidneys remove urea from blood and excrete it, dissolved in water, as urine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What happens when more protein is eaten than is needed?

A
  • The excess cannot be stored in the body, however amino acids provide useful energy
  • To make use of this energy, the liver removes the amino groups
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is deamination?

A

The process where the liver removes the amino groups from amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What happens during deamination?

A
  • The amino group (-NH2) of an amino acid and an extra hydrogen atom are removed and combine to produce NH3 and a keto acid
27
Q

Where does deamination take place?

A

In liver cells

28
Q

What happens to NH3 formed in deamination?

A

1) it is converted immediately to urea, which is less soluble and less toxic, by combining it with CO2 in the urea cycle
2) urea diffuses from liver cells into the blood plasma
3) as blood passes through the kidneys, urea is filtered out and excreted

29
Q

Why must NH3 be immediately converted to urea?

A

It is very soluble and highly toxic ∴ this prevents damage from NH3 building up in the blood

30
Q

What is the equation for deamination?

A

amino acid (-2H+H2O) = keto acid + NH3

31
Q

What is the structure of a keto acid?

A

C bonded to: double bond O, R and COOH

32
Q

What happens to the keto acid produced in deamination?

A

It may enter the Krebs cycle and be respired, converted to glucose or converted to glycogen/fat for storage

33
Q

Why must all of the urea made each day be excreted?

A

Because otherwise its concentration in the blood would build up and become dangerous

34
Q

What is urea?

A

The main nitrogenous excretory product of humans

35
Q

What other nitrogenous excretory products do we produce small quantities of?

A

Mainly creatinine and uric acid

36
Q

What is uric acid made from?

A

The breakdown of purines from nucleotides

37
Q

What is creatine made from and what does it do?

A
  • Creatine is made in the liver, from certain amino acids
  • Much of it is used in muscles, in the form of creatine phosphate, where it acts as an energy store, however some is converted to creatinine and excreted
38
Q

What do all mammals do (in relation to heat)?

A
  • They all generate heat and have ways to retain it in their bodies
  • They have physiological methods to balance heat gain, retention of body heat and heat loss so that they can maintain a constant body temperature
  • ∴ they are not dependent on absorbing heat from their surroundings and can be active at any time of day or night, whatever the external temperature
39
Q

What are animals that rely on external sources of heat when cold?

A

Inactive

40
Q

How is the heat generated in mammals released?

A

Much of it is released during respiration

41
Q

Where is lots of heat produced in mammals and what happens to this heat?

A
  • Much of the heat is produced by liver cells that have a huge requirement for energy
  • The heat they produce is absorbed by the blood flowing through the liver and distributed around the rest of the body
42
Q

Where is the hypothalamus?

A

In the brain

43
Q

What is the hypothalamus?

A

The central control for body temperature

44
Q

What does the hypothalamus receive?

A
  • A constant input of sensory information about the temperature of the blood and of the surroundings
  • Information from receptors in the skin that monitor changes in skin temperature
45
Q

What is the core temperature?

A
  • The temperature inside the body that remains very close to the set point (37 degrees in humans)
  • The temperature that the hypothalamus monitors
  • This temperature fluctuates a little, but is kept within very narrow limits
46
Q

What temperature is the first to change if there is a change in the temperature of the surroundings?

A

Skin temperature ∴ receptors in skin give an early warning about a possible change in core temperature

47
Q

What happens when the core temperature decreases or the temperature receptors in the skin detect a decrease in the temperature of the surroundings?

A

The hypothalamus sends impulses that activates physiological responses (or uses adrenaline?)

48
Q

What are the physiological responses in response to an decrease in temperature?

A

1) vasoconstriction
2) shivering
3) raising body hairs
4) decreasing the production of sweat
5) increasing the secretion of adrenaline

49
Q

How does increasing the secretion of adrenaline increase core temp?

A

Adrenaline released from the adrenal gland increases the rate of heat production in the liver

50
Q

How does vasoconstriction increase core temp?

A

1) muscles in the walls of arterioles that supply blood to capillaries near the skin surface contract
2) this narrows the lumens of the arterioles and reduces the supply of blood to the capillaries so that less heat is lost from the blood

51
Q

How does shivering increase core temp?

A

The involuntary contraction of skeletal muscles generates heat which is absorbed by the blood and carried around the rest of the body

52
Q

How does raising body hairs increase core temp?

A

1) muscles are the base of hairs in the skin contract to increase depth of fur ∴ trapping air close to the skin
2) air is a poor conductor of heat ∴ a goof insulator of heat

53
Q

How does decreasing the production of sweat increase core temp?

A

This reduces the loss of heat by evaporation from the skin surface

54
Q

What are behavioural responses to cold and what are they brought about by?

A
  • Curling up to reduce SA exposed to the air, huddling together, finding a source of warmth, putting on warm clothing
  • Brought about by higher centres in the brain stimulated by the hypothalamus
55
Q

What happens when the core temperature increases or the temperature receptors in the skin detect an increase in the temperature of the surroundings?

A

The hypothalamus increases the loss of heat from the body and reduces heat production

56
Q

What receptors detect a change in core temp?

A

Central thermoreceptors

57
Q

What are the physiological responses in response to an increase in temperature?

A

1) vasodilation
2) lowering body hairs
3) increasing sweat production

58
Q

How does vasodilation help to decrease core temp?

A

The muscles in the arterioles in the skin relax, allowing more blood to flow through the capillaries so that heat is lost to the surroundings

59
Q

How does lowering body hairs help to decrease core temp?

A

Muscles attached to the hairs relax so they lie flat, reducing the depth of fur and the layer of insulation

60
Q

How does increasing sweat production help to decrease core temp?

A
  • Sweat glands increase the production of sweat which evaporates on the surface of the skin ∴ removing heat from the body
  • Water has a high latent heat of vaporisation ∴ as sweat evaporates it removes a lot of heat energy
61
Q

What are behavioural responses to heat?

A
  • Resting or lying down with limbs spread out to increase the body surface exposed to the air, wearing loose fitting clothing, turning on fans, air conditioning, taking cold drinks
62
Q

What happens when the environmental temperature decrease gradually e.g. the approach of winter in temperate climates?

A

1) the hypothalamus releases a hormone which activates the anterior pituitary gland to release thyroid stimulating hormone (TSH)
2) TSH stimulates the thyroid gland to secrete the hormone thyroxine into the blood
3) thyroxine increases the metabolic rate which increases heat production e.g. in the liver
4) when temperatures rise again, the release of TSH is reduced ∴ less thyroxine is released

63
Q

What is an example of positive feedback which is bad?

A

1) if a person breathes air that has a very high CO2 content, this produces a high [CO2] in the blood
2) this is sense by CO2 receptors, which cause the breathing rate to increase
3) ∴ the person breathes faster, taking in even more CO2, which stimulates the receptors even more, so a person breathes faster and faster

64
Q

What is an example of positive feedback which is good?

A

Transmission of nerve impulses

Biology A-Level (44 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions