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Biology > Homeostasis - Breaking Out In A Sweat > Flashcards

Homeostasis - Breaking Out In A Sweat Flashcards

1
Q

What is homeostasis?

A

The maintenance of a constant internal environment

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2
Q

Why would metabolic rate decrease if the body temperature became too high?

A
  • Enzymes would become denatured due to them vibrating too
  • This breaks the hydrogen bonds that hold together the 3D shape
  • Loss of 3D shape means active site has changed shape so no longer works as a catalyst
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3
Q

Give an example of negative feedback in the body

A

The controlling of body temperature

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4
Q

How is temperature controlled in mammals?

A
  • Thermoreceptors in the skin detect a change in temperature
  • The receptors send impulses along sensory neurons to the hypothalamus (brain)
  • The hypothalamus then sends impulses along motor neurons to effectors

-The effectors restore body temperature to normal
eg hair errector muscles contract when body temperature is too low

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5
Q

What is the process called of maintaining body temperature?

A

Thermoregulation

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6
Q

What feedback mechanism is stimulated when the body increases in temperature?

A

Sweat glands secrete sweat

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7
Q

What feedback mechanisms are inhibited when there is an increase in body temperature?

A
  • Contraction of arterioles - this means they are relaxed and dialated
  • Hair errector muscles - relax so hair lies flat
  • Liver - reduces metabolic rate
  • Skeletal muscle - relax so no shivering
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8
Q

What feedback mechanisms are stimulated when there is a decrease in body temperature?

A
  • Arterioles contract - this means they constrict, reducing blood flow
  • Hair errector muscles contract - hair raises
  • Liver - increases metabolic rate
  • Skeletal muscles contract - this causes shivering
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9
Q

What feedback mechanisms are inhibited when there is a decrease in body temperature?

A

Sweat glands - no sweat produced

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10
Q

How can skin control body temperature?

A
  • Sweating
  • Raising or flattening hair
  • Route of blood flow via vasoconstriction and vasodilation
  • Shivering
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11
Q

What is shivering and how does it maintain body temperature?

A
  • Shivering is the uncontrolled contraction of normally voluntary muscles
  • Energy is transferred to muscle tissue
  • This results in more respiration and therefore heat
  • Heat production can increase six-fold
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12
Q

Describe what happens in vasoconstriction

A
  • Muscles in the arteriole walls contract
  • This means the arterioles constrict, reducing blood flow to the surface capillaries
  • The shunt vessel, located further below the surface of the skin, dialates so more blood flows through it
  • This means blood is travelling further away from the skin’s surface so less energy is lost via radiation, conduction and convection
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13
Q

Describe what happens in vasodilation

A
  • Muscles in the arterioles walls relax so the arterioles dilate
  • The shunt vessel constricts, reducing the amount of blood flowing through it
  • More blood is travelling closer to the skin’s surface so more energy is lost via radiation, conduction and convection
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14
Q

What will happen to metabolic reactions if body temperature falls below or rises above the normal range?

A
  • Low temperatures cause a decrease in metabolic reactions as enzyme-controlled reactions slow
  • High temperatures cause an initial rise in metabolic rate but then declines as the enzymes become denatured
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15
Q

Name things that must be controlled by the body through homeostasis

A
  • Glucose concentration
  • Ion concentration
  • CO2 concentration
  • Water levels
  • pH of blood
  • Temperature of the blood
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16
Q

What are the homeostasis control mechanisms trying to maintain?

A
  • The norm value of a condition
  • This is usually the optimum for that condition

eg body temperature is 37°C

17
Q

What stimulates effectors to return a condition to the norm value?

A

-Nerve impulses or hormones from the control centre

18
Q

What is negative feedback?

A

-The mechanism that restores a condition back to the norm value

19
Q

Explain how negative feedback would act to restore a decreasing population to the norm for the environment

A
  • A fall in population below the norm reduces competition
  • This increases available food
  • The population increases back to normal
20
Q

How are hormone levels controlled?

A

By negative feedback

21
Q

Describe how testosterone levels are maintained

A
  • A change in testosterone levels is detected by the hypothalamus
  • A decrease in testosterone causes gonadotropin-releasing hormone to be produced by the hypothalamus
  • This stimulates the pituitary gland to release hormones that stimulate the testes to synthesise testosterone
22
Q

What is positive feedback? Give an example of it occuring in the body

A
  • Output from the control centre moves the condition further from the norm value
  • In child birth - there is a constant increase in contractions which increases the pressure in the uterus, until the baby is born
23
Q

How is a clot forming an example of positive feedback?

A
  • Platelets stick to exposed collagen in the wall and each other
  • They release chemicals that attract more platelets
  • This continues until a clot has formed
24
Q

A marathon runner feels cooler after dousing himself in water. How does this help to cool him?

A

-Increased energy lost by conduction and evaporation

25
Q

Why does high humidity make marathon running more dangerous?

A
  • Less evaporation occurs
  • Less energy lost by sweating
  • Harder for athletes to keep their bodies at a safe temperature
26
Q

How does convection play a part in homeostasis?

A
  • Air next to the body will be warned by heat from the skin

- The warm air expands and rises, taking the energy with it, and is replaced by cooler air

27
Q

How does body hair reduce heat loss?

A
  • Hair traps a layer of air next to the skin
  • This acts as a thermal insulator
  • It reduces the heat lost by convention as the air can not be replaced by cooler air
28
Q

Cats (including the big cats) can only sweat from the skin surface of their paws and nose. What other method might a cheetah rely on for transfer of energy to the environment?

A
  • Evaporation from gas exchange surfaces; panting

- Lowering of body hairs to increase heat lost by radiation, conduction and convection

29
Q

Why is heat normally lost to the surroundings?

A

Because the human body temperature is usually higher than the surroundings

30
Q

What can happen to core body temperature in very cold environments?

A

-Decrease as the body loses thermal balance due to excessive cooling

31
Q

What happens when core body temperature starts to fall?

A
  • Hypothalamus detects change

- Tries to regulate internal temperature by increasing metabolic rate and slowing energy loss

32
Q

What would be the major route of energy loss for a cross-channel swimmer?

A

Conduction

33
Q

Swimming the channel means spending between 10-20 hours in water that is usually between 13-16°C. What mechanisms are used to maintain body temperature and enable survival without a wetsuit?

A
  • Shivering increases metabolism which transfers more energy to body cells
  • Nerve impulses to the arterioles in the skin cause vasoconstriction which means blood travels further from the skin surface so less energy is lost by radiation, conduction and convection
  • Respiration in muscles transfers more energy to body cells

Biology (20 decks)

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