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Biology > Chapter 15 - Homeostasis > Flashcards

Chapter 15 - Homeostasis Flashcards

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1
Q

Latent heat of evaporation

A

➜ objects cool down as water evaporates from a surface

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2
Q

Radiation

A

➜ the transmission of EM waves to and from the air, water or ground

  • transfer of heat between two objects through the air
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3
Q

Convection

A

➜ the heating and cooling by currents of air or water, warm air of water rises and cooler air of water sinks setting up convection currents around an organism

  • The transfer of heat through moving air
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4
Q

Conduction

A

➜ the heating as a result of the collision of molecules. Air is not a good conductor of heat but the ground and water are

  • transfer of heat from direct contact between two objects.
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5
Q

Ectotherms behavioural responses

A

behaviour when too cold:
➜ basking
➜ change body shape (increasing surface area)
➜ pressing body against warm ground (conduction)
behaviour when too hot:
➜ finding shade or burrowing
➜change body shape (decreasing surface area)
➜ pressing body against cool surfaces (conduction)

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6
Q

Endotherms behavioural responses (cold)

A

behaviour when too cold:
➜ less sweat - less heat loss
➜ hairs raised - layer of insulating air is trapped
➜ vasoconstriction - less flow of blood to surface so less heat loss
➜ high metabolic rate in liver cells - respiration generates more heat
➜ shivering - skeletal muscles contract - heat generated from respiration

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7
Q

Endotherms behavioural responses (hot)

A

behaviour when too hot:
➜ sweat - evaporates, heat loss, cools blood at surface
➜ hairs lie flat on surface - radiation
➜ Vasodilation - blood flows closer to surface of skin - more heat loss
➜ low metabolic rate in liver cells - respiration generates less heat

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8
Q

Excretion

A

➜ the removal of metabolic waste products from the body
➜ CO2
➜ Urea - (Co(NH2)2) - produced in the liver from ammonia and CO2 (breakdown of excess amino acids by liver)
➜ Bile pigments - formed when haemoglobin is broken down by Kupffer cells (specialised macrophages in the liver)

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9
Q

Egestion

A

➜ the removal of undigested material from the body

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10
Q

Deamination

A
  • removal of an amine group from a molecule
  • body cannot store either proteins or amino acids
  • deaminate amino acids, remove the amino group + converting it to ammonia which is toxic, to urea
  • urea is toxic in ↑ conc but not in blood conc
    -remainder of amino acids can be converted into lipids for storage or cellular respiration
  • ammonia produced is converted to urea in the ornithine cycle

2NH3 + CO2 –> CO(NH2)2 + H2O

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11
Q

Transamination

A

➜ conversion of one amino acid to another

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12
Q

Detoxification

A

➜ a metabolic waste product is converted to water and oxygen by catalase
➜ e.g hydrogen peroxide, ethanol to ethanal

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13
Q

What do animals + plants need to be able to do?

A

Animals and plants need to be able to respond to changes in their internal and external environment and to coordinate the activities of their different organs.

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14
Q

Why is homeostasis important?

A

ensures the maintenance of optimal conditions for enzyme action and cell function

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15
Q

What are the 2 communication systems in mammals that require information to be transferred between different parts of the body?

A
  • nervous system
  • endocrine system
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16
Q

What does the human nervous system consist of?

A
  • central nervous system (CNS) – the brain and the spinal cord
  • peripheral nervous system (PNS) – all of the nerves in the body
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17
Q

What does the nervous system allow us to do?

A

allows us to make sense of our surroundings and respond to them and coordinate and regulate body functions

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18
Q

How is info sent through nervous system?

A

nerve impulses – electrical signals that pass along nerve cells known as neurones

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19
Q

What do neurones do ?

A

coordinate the activities of sensory receptors (eg. those in the eye), decision-making centres in the central nervous system, and effectors such as muscles and glands

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20
Q

What is a hormone?

A
  • a chemical substance produced by an endocrine gland and carried by the blood
  • transmit information from one part of the organism to another and bring about a change -> alter the activity of one or more specific target organs
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21
Q

What is endocrine system?

A
  • endocrine glands that produce hormones in animals are known collectively as that
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22
Q

What is a gland?

A
  • a group of cells that produces and releases one or more substances (secretion)
23
Q

What does homeostatic control mechanisms in organisms use?

A
  • negative feedback to maintain homeostatic balance
24
Q

What does negative feedback control loops involve?

A

-receptor -> detects a stimulus that is involved with a physiological factor
- coordination system (nervous system and endocrine system) –> transfer information between different parts of the body
- effector (muscles + glands) – to carry out a response

25
Q

What is the outcome of a negative feedback loop?

A
  • stimulus is continuously monitored
  • increase in the factor, body responds to make the factor decrease
  • decrease in the factor, the body responds to make the factor increase
26
Q

What do negative feedback loops do?

A
  • reduce the initial effect of the stimulus
27
Q

What do receptors do ?

A
  • detect any deviations from stimuli which results in a corrective mechanism to return the factor back to normal
28
Q

What do positive feedback loops do?

A
  • enhance the effect of the original stimulus
29
Q

What is homeostasis?

A
  • regulation of the internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external changes.
30
Q

What is cell signalling?

A
  • process in which cells communicate with each other
31
Q

Why is cell signalling important?

A
  • allows multicellular organisms to control and coordinate their bodies and to respond to their environments
32
Q

What do cell signalling pathways do?

A
  • coordinate the activities of cells, both between cells that are very close to each other and between cells that are large distances apart within the organism
33
Q

What are the basic stages of cell signalling?

A
  • stimulus is received by a receptor cell
  • stimulus is converted to a signal (chemical) that can be passed on - this process is known as transduction
  • signal is transmitted to a target cell (effector) that can detect it (via receptors in its cell membrane)
  • response is made
34
Q

What are the 2 cell signalling pathways categorised into?

A
  • Paracrine signalling (signalling between cells that are close together)
  • Endocrine signalling (signalling between cells that are far apart, which involves the signalling molecule being transported in the circulatory system)
35
Q

What does transmission of messages in cell signalling pathways require?

A
  • crossing cell surface membranes
36
Q

Why is cell surface membrane important?

A
  • membrane controls which molecules can move between the internal and external environments of the cell
37
Q

Why are signalling molecules are usually very small ?

A
  • for easy transport
38
Q

What do signalling molecules do?

A

binds to the receptor molecule, causing specific changes in the receiving cell

39
Q

What is thermoregulation?

A

control of internal (core) body temperature

40
Q

With regards to the process of thermoregulation, what 2 groups can animals be separated into?

A
  • Endotherms
  • Ectotherms
41
Q

What are endotherms?

A
  • animals that possess physiological mechanisms to control their internal body temperature eg. mammals + birds
    -> they can maintain their body temperatures using heat generated within their body tissues
42
Q

What are ectotherms?

A
  • animals that rely on behavioural adaptations to ensure their internal body temperature does not get too high or low eg. reptiles and amphibians
    -> they regulate their body temperatures by absorbing heat from their environment
43
Q

Vasodilation

A

The warmer the environment, the less heat is lost from the blood at the body’s surface
- increase heat loss by supplying the capillaries in the skin with a greater volume of blood, which then loses heat to the environment via radiation
- Arterioles (small vessels that connect arteries to capillaries) have muscles in their walls that can relax or contract to allow more or less blood to flow through them
- During vasodilation these muscles relax, causing the arterioles near the skin to dilate and allowing more blood to flow through skin capillaries

44
Q

Sweating

A
  • secreted by sweat glands
  • cools the skin by evaporation which uses heat energy from the body to convert liquid water into water vapour
  • sweating is less effective as a cooling mechanism in humid environments, as humid air is less effective at evaporating water
45
Q

How do endothermic animals detect external temperatures?

A

via peripheral receptors

46
Q

What are peripheral receptors?

A
  • thermoreceptors found in the skin and mucous membranes
  • receptors for both hot + cold
  • communicate with the hypothalamus to bring about a physiological response to changing external temperatures
47
Q

How does the hypothalamus also help to regulate body temperature ?

A

monitoring the temperature of the blood flowing through it + initiating homeostatic responses when it gets too high or too low

48
Q

Flattening of hairs

A
  • hair erector muscles (effectors) in the skin relax, causing hairs to lie flat
  • stops them from forming an insulating layer by trapping air and allows air to circulate over skin and heat to leave by radiation
49
Q

Vasoconstriction

A
  • decrease heat loss by supplying capillaries in the skin with a smaller volume of blood, minimising the loss of heat to the environment via radiation
  • muscles in the arteriole walls contract, causing the arterioles near the skin to constrict and allowing less blood to flow through capillaries
  • blood is diverted through shunt vessels, which are further down in the skin and therefore do not lose heat to the environment
  • reduces heat loss from the blood as it flows through the skin
50
Q

Boosting metabolic rate

A
  • Most of the metabolic reactions in the body are exothermic (heat-producing) and this provides warmth to the body
  • In cold environments, the hormone thyroxine (released from the thyroid gland) increases the basal metabolic rate, increasing heat production in the body
51
Q

Shivering

A
  • reflex action in response to a decrease in core body temperature (nervous mechanism)
  • muscles are the effectors and they contract in a rapid and regular manner
  • metabolic reactions required to power this shivering generate sufficient heat to warm the blood and raise the core body temperature
52
Q

Erection of hairs

A
  • hair erector muscles in the skin contract, causing hairs to stand on end
  • forms an insulating layer over the skin’s surface by trapping air between the hairs and stops heat from being lost by radiation
53
Q

What do ectotherms do to heat up?

A
  • ectotherms seek out the sun or warmer surfaces and rest or ‘bask’ in these locations as they warm, until their body temperature has been increased sufficiently
54
Q

What do ectotherms do to cool down?

A
  • ectotherms seek shade/ water

Biology (25 decks)

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