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OCR A Biology > Unit 5 - Communication and Homeostasis > Flashcards

Unit 5 - Communication and Homeostasis Flashcards

1
Q

The need for communication systems

A

Respond to changes in the internal and external environment

Coordinate the activities of different organs

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2
Q

How we respond to changes

A

Hormonal

Neuronal

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3
Q

Cell communication

A

Process by which a cell detects and responds to signals in its environment. It is the way in which cells interact w/ their environment and other cells around them

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4
Q

Properties of a good communication system

A

Covers entire body
Be v. spp in the communication
Rapid
Enable both long and short-term responses

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5
Q

Methods of cell signalling

A

Chemical or neuronal

Affecting distant or nearby cells

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6
Q

Types of cell signalling

A 
Autocrine
Gap Junction
Synaptic
Paracrine
Endocrine
Contact - dependent
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7
Q

Ending communication

A

Reuptake by cells
Broken down by neurotransmitters
Messenger removed from liver e.g. hormone

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8
Q

Response

A

A change in behaviour or physiology as a result of a change in the environment

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9
Q

Stimulus

A

Any change in the environment that causes a response

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10
Q

Effector

A

An organ or cell that acts in response to a stimulus

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11
Q

Receptors

A

An organ or cell able to detect and respond to environmental stimuli and transmit an impulse to a sensory nerve

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12
Q

Homeostasis

A

The maintenance of a constant or near constant internal environment within a narrow limit even though the environment’s changing

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13
Q

Homeostatic control and principle

A 
Stimulus 
Receptor
Communication pathway 
Effector 
Response
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14
Q

Negative feedback

A

Varying physiological value is returned to its mean value by the controlling mechanism

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15
Q

Positive feedback

A

Varying physiological value is pushed above its mean value by the controlling mechanism

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16
Q

Why should body temp be kept constant

A

To keep enzymes working at their optimum and so that they don’t denature at higher temps

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17
Q

Why should blood glucose conc. be kept constant

A

To supply sufficient glucose to tissues for respiration without decreasing the water potential of the blood too much
Contributes to oncotic pressure (forming tissue fluid)

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18
Q

Why should blood salt levels be kept constant

A

To maintain water potential and blood pressure

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19
Q

Why should the water potential of blood be kept constant

A

To maintain blood pressure and to ensure cells are in the correct conditions

20
Q

Why should the blood pressure be kept constant

A

To ensure it is high enough to deliver blood efficiently but without damaging blood vessels

21
Q

Why should the carbon dioxide levels be kept constant

A

CO2 reacts w/ water to form an acid - change in pH can alter protein structure and effect enzymes activity

22
Q

Behavioural adaptations of ectotherms when its too hot

A

Finding shade
Reduce contact/decrease SA exposed to the sun
Burrow underground

23
Q

Behavioural adaptations of ectotherms when its too cold

A

Basking in the sun
Finding a hot surface to lie on
Increase SA exposed to sun

24
Q

Adaptations of endotherms when its too hot

A 
Sweat 
Vasodilation
Hairs and feathers lie down 
Panting 
Decrease respiration rate
No shivering
25
Q

How does panting cool down endotherms

A

Lose heat through water vapour

26
Q

How does decreased respiration rate cool down endotherm

A

Respiration is an exothermic reaction

27
Q

Vasodilation

A

Sphincters open
Increase in diameter of lumen of arteriole to increase blood flow
Heat is lost through radiation

28
Q

Vasoconstriction

A

Sphincters closed
Decrease in diameter of lumen of arteriole to decrease blood flow
Heat is conserved through radiation

29
Q

Thermoregulatory centre

A

Located in hypothalamus concerned mainly w/ the regulation of heat production, inhibition and conservation to maintain a normal body temp

30
Q

Periphery temp receptors

A

Receptors monitor temp of extremities (early detection for hypothalamus)

31
Q

Adaptations of endotherms when its too cold

A

Vasoconstriction
Contraction of erector pilli attached to base hairs
Increase respiration
Involuntary muscle contraction

32
Q

Neuronal signalling

A

Uses interconnected networks of neurons that signal to each other across synapse junctions
Conduct a signal v. quickly and enable rapid response to stimuli that may be changing quickly

33
Q

Hormonal signalling

A

Glands secrete hormones into the bloodstream which bind to receptors on spp cells so the desired response in produced
Enables longer term responses

34
Q

Endocrine Signalling

A

Signals are transmitted over longer distances e.g. gland to brain through the blood (insulin)

35
Q

Paracrine Signalling

A

Cytokines diffuse through tissue fluid and act locally on nearby cells
No involvement of blood
Signal conc. gradient determines how cells act
Taken up by cells or degraded by enzymes (short lived)

36
Q

Autocrine Signalling

A

Hormonal/ chemical messenger (autocrine)
Binds to autocrine receptors on that same cell, leading to changes to cells
Can promote proliferation and therefore cause a tumour

37
Q

Contact dependent signalling

A

Signalling molecule is not secreted but bound to plasma membrane
Interacts w/ receptor
Particularly important between immune cells (APCs)

38
Q

Synaptic Signalling

A

Electrical signalling

Presynaptic terminal, synaptic terminal, postsynaptic membrane

39
Q

Gap Junction Signalling

A

Communicate directly w/ immediate neighbour through gap junctions
Gap junctions connect the cytoplasm via protein channel
Allow the passage of ions and small molecules and coordinated contraction of cardiac muscle

40
Q

Endotherms

A

Birds and mammals
Control temp within strict limits
Variety of mechanisms to control temp
Largely independent of external temp

41
Q

Ectotherms

A

Reptiles, fish, amphibians
Body temp fluctuate w/ fluctuations in the external temp
Relies on behavioural mechanism

42
Q

Advantages of endothermy

A

Largely independent of external temp
Activity still possible when external temp is cold
Ability to inhabit warmer and colder parts of the world

43
Q

Disadvantages of endothermy

A

Significant part of the energy intake is used in maintaining body temp when cold
More food required to be able to respire

44
Q

Advantages of ectothermy

A

Can survive long periods of time w/ out eating

Greater proportion of energy can be used for growth

45
Q

Disadvantages of ectothermy

A

Unable to generate internal heat through respiration
Incapable of activity during winter
Have to warm up in the day (risk of predators)

OCR A Biology (42 decks)

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