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Biology > Homeostasis > Flashcards

Homeostasis Flashcards

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1
Q

Outline the ways in which the structures of a sensory and motor neurone are the same (4)

A
  • Dendrites
  • An axon
  • A cell body with a nucleus
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2
Q

Explain the effect sweating has on the body during a fever (temp rise) [2]

A
  • Sweating secretes a fluid onto the skin surface which evaporates and has a cooling effect on the body
  • Water has a high latent heat of vaporisation
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3
Q

Suggest why shivering occurs during a fever (1)

A

As the new body temp is higher, shivering helps raise the temp of the internal environment

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4
Q

Alcohol makes people feel warmer but causes vasodilation.

Why is it bad for people with hypothermia to drink alcohol (2)

A

Vasodilation is the widening of arterioles whereby there is an increase in the blood flow near the skin surface thus resulting in heat being loss from the body through radiation

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5
Q

Outline the role of synapses in the nervous system (3)

A
  • Acts as a chemical bridge between neurones whereby impulses can be sent. This enables cell signalling and communication
  • Ensures transmission of neurones in one direction
  • A single neurone can send an impulse to many neurones
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6
Q

Name one chemical that transfers a nerve impulse to one neurone to another (1)

A

DOPAMINE

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7
Q

What does the endocrine gland do (1)

A

It releases hormones directly into the blood in order to regulate conditions

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8
Q

Name one hormone that will increase heart rate (1)

A

Adrenaline

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9
Q

State one way in which the nervous system decreases heart rate (1)

A

It passes an impulse along the parasympathetic nerve

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10
Q

Describe how the negative feedback system is used to control blood glucose concentration (6)

A

Receptor cells detect a change in the blood glucose conc.

IF HIGHER
• Beta cells will release insulin

  • This will result in a higher absorption of glucose BY EFFECTOR CELLS which occurs through glucose transport proteins in the plasma membrane whereby glucose is then converted into glucagon
  • This means that more glucose will be used during respiration

IF LOWER
• Alpha cells will release glucagon

• Glucagon then get converted into glucose in a process known as glucagonolysis

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11
Q

Define homeostasis (2)

A

Homeostasis is the maintenance of a constant/steady internal environment at a set point level regardless of the external environment

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12
Q

How does the pancreas act as an endocrine gland (3)

A
  • It secretes hormones directly into the blood
  • Beta cells release insulin
  • Alpha cells release glucagon
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13
Q

How does the pancreas act as an exocrine gland (3)

A
  • It releases enzymes into the bile duct
  • This release is triggered by hormonal stimulation
  • and results in pancreatic secretions into the gut/small intestine
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14
Q

Suggest how the adrenaline molecule can cause different effects in different target tissues (2)

A
  • Different tissues have different adrenaline receptors

* causing cAMP to either increase or decrease

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15
Q

What part of the brain is responsible for the control of body temperature (1)

A

The thermoregulatory centre in the HYPOTHALAMUS

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16
Q

What are receptors (in terms of temp) [1]

A

They are SENSORY CELLS that detect changes in skin temp and in the temp of the blood flowing through the hypothalamus

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17
Q

Where are the chemicals secretes by endocrine glands transported to by the blood (1)

A

EFFECTORS

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18
Q

Name the endocrine tissue in the pancreas that is responsible for the secretions of hormones (1)

A

ISLETS OF LANGERHAN

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19
Q

Identify the specific cell type in pancreatic tissue that secrete the hormone insulin (1)

A

BETA CELLS

20
Q

State where in the pancreatic cell insulin molecules are synthesised (1)

A

Ribosomes

ROUGH ENDOPLASMIC RECTICULUM

21
Q

What happens after the synthesis of an insulin molecule until it is ready to be secretes from the pancreatic cell (3)

A
  • Transported to the golgi
  • where it is modified in the Golgi
  • packages in to Golgi vesicles and transported to the plasma membrane
22
Q

What cell in the pancreas secretes glucagon (1)

A

Alpha

23
Q

What does the hormone glucagon do and when does it occur (2)

A

Glucagon is converted to glucose in a process known as glucagonolysis and occurs when blood glucose concentration is low

24
Q

State where core body temperature is monitored (1)

A

The thermoregulatory centre in the hypothalamus

25
Q

Name the type of sensory cells in the skin that detect change in environmental temp (1)

A

Thermoreceptors

26
Q

Explain why elephants have larger, thin ears which they move back and forth when they’re hot (2)

A
  • Large surface area maximises heat loss

* Thin so blood vessels are near the skin meaning heat can be loss through radiation

27
Q

Explain why penguins living in cold climates have shunt blood vessels that carry blood away from their feet (1)

A

Blood flow being diverted from feet means less heat can be loss from the penguin

28
Q

Describe the way in which an endothermic mammal prevents its body temp from decreasing when the external temp decreases (6)

A

Thermoreceptors in the skin detect a change in temp / are stimulated by the decrease in external temp and sends impulses to the hypothalamus

  • vasoconstriction is the narrowing of arterioles whereby less blood flows near the skin meaning less heat can be loss from the body through radiation
  • hairs stand erect in order to trap an insulating layer of air so less heat is loss through convection
  • metabolism is increased in order to gain heat from energy created
29
Q

What is homeostasis needed for (3)

A
  • REGULATION OF CORE TEMP
  • BLOOD GLUCOSE CONCENTRATION
  • BLOOD pH
30
Q

Why is homeostasis needed for the regulation of core body temp (2)

A
  • At temperatures exceeding optimal level, enzymes begin to denature
  • At temperatures below optimal level, enzyme activity is slower due to less collisions
31
Q

Why is homeostasis needed for the regulation of blood pH (1)

A

High acidity results in the release of H+ ions that denature enzymes

32
Q

Why is homeostasis needed for the regulation of blood glucose concentration (2)

A
  • When high, water moves out of cell by osmosis due to more water being outside cell
  • When pow, water moves in cell and could potentially result in the cell bursting
33
Q

What is meant by a negative feedback system (1)

A

When conditions deviate from set point level and are reversed to restore optimum conditions

34
Q

What is meant by a positive feedback system (1)

A

When a change from set point level is amplified and reinforced by effectors which respond to further increase the level away from the set point

35
Q

Why is positive feedback useful

A

To rapidly increase or activate something

36
Q

What are the advantages of being an ectothermic (4)

A
  • They need less food
  • Less if their food is used during respiration
  • More of the energy and nutrients gained rom food can be converted for growth
  • They can survive without food for a long period of time
37
Q

Name a disadvantage of being an ectotherm (1)

A

They are less active in colder conditions, making them vulnerable and at a higher risk from predators

38
Q

Why is cell communication essential (2)

A

It is vital for the survival of an organism whereby it needs to be able to detect and respond to changes in its internal and external environment

39
Q

In multicellular organisms, what is the change necessary for survival triggered by (1)

A

The NERVOUS and ENDOCRINE system

40
Q

Name the elements needed for the negative feedback system to work (3)

A
  • SENSORY RECEPTORS e.g. thermoreceptors to detect a change from set point level in the internal environment
  • EFFECTORS e.g. muscles or glands that can produce a response

When a change is detected, the receptors pass the message via the nervous or endocrine system to the effectors to produce a response to restore optimum conditions

41
Q

Why do hairs lie flat when body temp is high (1)

A

Hairs lying flat results in the insulating layer of air being reduced

And so therefore, more heat is loss by conduction

42
Q

Why do blood vessels dilate when body temp is high (1)

A

Vasodilation is the widening of arterioles which increases blood flow near the skin surface. This means that’s heat can be loss from the body through radiation

43
Q

Why is metabolic rate decreased when body temp is high (1)

A

So that less metabolic heat is gained

44
Q

Describe how insulin is released through the opening and closing of K+ and Ca+ channels [EXOCYTOSIS (6)]

A

1) The cell membrane has K+ and Ca+ channels whereby the K+ channels are normally open so K+ flows out
2) When blood glucose concentration is high, the glucose moves into the cell
3) Glucose is metabolised to produce ATP and this ATP closes the K+ channels
4) The accumulation of K+ inside the cell alters the potential difference across the cell membrane - the inside becomes less negative
5) The change in potential difference opens the Ca+ channels
6) The Ca+ cause the vesicles of insulin to fuse with the cell membrane, releasing insulin by EXOCYTOSIS

45
Q

Which part of the chloroplast is the metabolic pathway involving CO2 located in (1)

A

STROMA

46
Q

Explain why the theoretical rate of photosynthesis is not achieved at higher light intensities (2)

A

At high light intensity, light is no longer the limiting factor and temperature becomes the limiting factor because it involves enzymes

47
Q

Name 3 adaptation of a plant that lives in the shade/low light intensity (3)

A

More chloroplasts

More thylakoids in chloroplasts

Larger surface area of leaves

Biology (8 decks)

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