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OCR Biology A Level > 5.1.1 Communication and Homeostatsis > Flashcards

5.1.1 Communication and Homeostatsis Flashcards

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1
Q

Why do multicellular organisms need communication systems?

A
  • animals and plants need to respond to changes in their internal and external environment
  • they also need to coordinate the activities of different organs
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2
Q

Why do we need to keep our temperature?

A
  • low temperatures mean little kinetic energy
  • so chemical reactions involving enzymes slow down which can result in death
  • high temperatures can use enzymes to denature
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3
Q

Why do we need to keep our water potential constant?

A

If blood has lower water potential than tissue fluid, water moves into cells via osmosis, causing cells to burst

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4
Q

Why do we need to keep pH constant?

A
  • pH affects the amount of H+ ions
  • causing the tertiary structure of enzymes to change
  • 3D shape of active site changes
  • substrate can’t bind to form ES complexes
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5
Q

Why do we need to keep our blood glucose levels constant?

A

Dissolved glucose in large amounts can affect the water potential of the blood

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6
Q

How does communication occur in the human body?

A
  • the nervous system communicates with muscular system in order to move away or towards a stimulus
  • brain communicates with rest of the body through the nervous system
  • circulatory system works with nervous to maintain gas levels in blood + body temperature
  • hormones releases from glands to circulatory system communicate with other glands to maintain internal environment
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7
Q

Define homeostasis

A

Maintennance of a stable internal environment within a narrow range despite external environment conditions changing

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8
Q

What makes a good communication system?

A
  • covers the whole body
  • allows cell to communicate with each other
  • is specific
  • is rapid
  • can cause short term and long term effects
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9
Q

Define stimulus

A

A change in internal or external environment that causes a response

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10
Q

Define response

A

A change in behaviour or physiology due to a stimulus

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11
Q

Define physiology

A

Function of organs and organ systems, and how they work within the body to respond to changes

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12
Q

What are receptors and give examples

A

Detect stimuli and communicate with effectors
- retina
- hypothalamus
- pancreas

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13
Q

What are effectors and give examples

A

Cause a change to bring the body back to its normal level. Work through negative feedback mechanisms
- hormones
- nervous impulses

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14
Q

What is cell signalling

A

Communication and co-ordination between cells that allows cells to work together to trigger a response or a reaction inside the cell

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15
Q

Define negative feedback

A

Corrective homeostatic mechanism that works to restore any detected change in the internal environment to a set point/norm. It maintains a system around a set point/norm. (Leads to homeostasis)

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16
Q

Explain the process of negative feedback

A
  1. Stimulus changes away from norm
  2. Receptor detects change from norm
  3. Communication systems informs effector
  4. Effector (muscle or gland) produces change/response to reverse change from set norm
  5. Response to return system to point norm
  6. System at set point
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17
Q

Define positive feedback

A

When an initial biological change is increased further or exaggerated
(can be harmful or beneficial)

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18
Q

Explain the process of positive feedback

A
  1. Set point/norm
  2. Change away from set point
  3. Receptors detect change
  4. Communication system informs effector
  5. Effector reacts
  6. Change away from set norm
19
Q

Give examples of positive feedback

A

Labour
1. Cervix stretches
2. Causes pituitary gland to secrete oxytocin hormone which increases contractions
3. More contractions = more oxytocin
4. Continues until baby is born

Blood clotting
1. Blood vessel is damaged
2. Platelets stick to damaged area
3. They release factors that initiate blood clotting mechanism which attracts more platelets

Hypothermia
1. Lower body temperature reduces the kinetic energy of molecules
2. Enzyme activity reduces so less metabolic heat is produced
3. Body temperature drops even more

20
Q

Give key details about endotherms

A
  • animals (mammals + birds)
  • use heat from metabolic processes inside the body to maintain body temperature
  • metabolic processes include aerobic respiration
  • fur + hair to reduce heat loss (or scales)
  • mainly use physiological responses to thermoregulate, use a few behavioral responses
21
Q

Give advantages and disadvantages of endotherms

A

Advantages
- body temperature meaintained within a narrow range with changing environmental temperature
- organisms can be active despite external temperature
- can inhabit colder environments

Disadvantages
- large energy intake required to maintain high levels of metabolism/respiration
- more time spent feeding and finding food
- less food used for growth

22
Q

How is heat lost and gained in the body?

A

Lost
- radiation to environment
- evaporation of water to vapour
- convection of heat into air currents
- conduction of heat through skin

Gain
- radiation from environment
- metabolic activities mainly from liver

23
Q

What part of the brain is involved in temperature

A

Thermoregulatory centre; Area called the hypothalamus
- split into two parts:
Heat gain centre - activated by a fall in blood temperature
Heat loss centre - activated by a rise in blood temperature

24
Q

What thermoreceptors does the thermoregulatory center receive inputs from?

A

Receptors in the hypothalamus measure blood temp (internal)
Peripheral thermoreceptors in the skin monitor external temp

25
Q

How do animals conserve heat physiologically?

A

Vascoconstriction: Decrease diameter of arteriole lumen to reduce blood flow to the capillaries in the skin of the organism, reducing heat loss through skin by radiation, conduction, convection

Raising of hair - erector pili muscles in the skin contract, pulling hairs/ feathers up trapping a layer of still air, acting as an insulator

26
Q

How do animals conserve heat through behavioural mechanisms?

A
  • shelter from the wind
  • animals huddle together to maintain core body temperature
27
Q

How does penguins huddling minimise heat loss?

A

Penguins exchange heat energy with each other (radiation)
Change position so the same penguins aren’t always in the middle

28
Q

How do penguins adjust their feet temperature?

A
  • shunt vessel that connects arteriole carrying blood towards feet
  • when penguin is too cold muscles restrict the arterioles so less blood flow to feet = reducing heat loss from blood
  • when penguin is too warm arterioles allow more blood flow to feet = cools them down
29
Q

How are penguin feathers specialised?

A
  • short, broad, closely spaced; keeps water away from the skin
  • tufts of down on the feather shafts provide insulative properties
30
Q

List physiological ways of generating heat

A

Shivering - involuntary rhythmic muscle contractions release metabolic heat
Release of adrenaline and thyroid hormones
Increased metabolic rate - heat generate from metabolic activity of live cells

30
Q

List behavioural ways of generating heat

A

Basking in the sun - increases heat gain by radiation

31
Q

List physiological ways of losing heat

A

Vasodilation - increase in arteriole lumen diameter near surface of skin - increases blood flow allowing more heat loss by radiation, convection, conduction
Increased sweating - water in sweat evaporates from skin surface, requiring energy in heat form - reducing core body temp
Panting - Heat lost by evaporation in fur covered animals
Lowering of body hair - erector pili muscles relax - lower hairs = reduced layer of insulating air

32
Q

List behavioural ways of losing heat

A
  • avoiding heat of the day
  • sheltering in burrows or shade to prevent gain of heat from radiation
33
Q

Explain the negative feedback process of vasodilation in hot temperatures

A
  1. External environment temperature increases
  2. Peripheral thermoreceptors stimulated
  3. Nerve impulses conducted to hypothalamus
  4. Thermoregulatory centre in hypothalamus also detects change in blood temperature
  5. Vasodilation of arteriole lumen
  6. Pre-capillary sphincter muscle relax
  7. More blood in surface capillaries and less in inner blood vessel
34
Q

Explain how sweating reduces core body temperature and why is is an efficient mechanism

A

Sweat produced from glands allows heat energy to pass to sweat from blood to skin - sweat evaporates removing heat from the body and cools the body down

Water has a high latent heat of vaporisation, so a lot of energy is needed to evaporate the water

35
Q

List behavioural adaptations for regulating temperature

A
  • basking in sun (too cold)
  • digging burrows (too hot or cold)
  • period of aestivation (Summer deep sleep to avoid heat stress)
  • wallowing in water or mud (too hot)
36
Q

List anatomical adaptations for regulating temperature

A
  • large ears + wrinkly skin; increases SA= increases heat loss
  • pale fur reflects radiation - decreasing heat gain
  • thick layer of insulating fat - reduces heat loss
37
Q

Define ectotherm

A

Organisms that mainly rely on external/environmental sources of heat to regulate their body temperature
- only a few use their own metabolism to control their body temperature
- all invertebrates, fish, reptile, amphibians

38
Q

Give advantages and disadvantages of being an ectotherm

A

Advantages
- less food & energy needed
- less time feeding + finding food
- can survive longer without eating
- greater proportion of energy used for growth or reproduction

Disadvantages
- less active in lower temperatures (can’t live in cold climates)
- may need to warm up in morning (greater risk of predation when lower temp)
- less able to hunt for food when body temp low

39
Q

How can ectotherms gain heat?

A
  • basking in the sun
  • orientate body to sun or warm ground
  • change body shape to maximise exposure
  • alter colour to increase absorption
40
Q

How can ectotherms lose heat?

A
  • bathe in water or find shade in burrow
  • orientate body away from sun
  • reduce contact with ground
  • increase breathing movements
41
Q

List physiological responses some ectotherms can use to control their temperature

A
  • black pigment helps absorb enough heat radiation to survive cold water
  • can alter heart rate to increase/decrease metabolic rate to generate more/less metabolic heat
42
Q

Why are ectotherms not extinct yet or evolved to have hair?

A

They require much less to eat as don’t need to fuel metabolic ways of regulating temperature

OCR Biology A Level (20 decks)

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