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OCR Biology > Module 5: Communication and homeostasis > Flashcards

Module 5: Communication and homeostasis Flashcards

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1
Q

Define homeostasis. Why is it important in organisms?

A

Process of maintaining constant internal body conditions despite external changes. It ensures the maintenance of optimal conditions for enzyme action and cell function.
Factors controlled by homeostasis include conc of glucose in blood, body temp, blood pH.

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2
Q

What is negative feedback? (homeostasis)

A

Action taken by the body to return something to a normal level after deviation e.g. controlling body temp.

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3
Q

What is positive feedback?

A

Amplifies a response to a stimulus, causing it to deviate further from the normal range e.g. blood clotting.

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4
Q

Both the nervous system and endocrine system work together to prepare the body for action by …

A
  1. Increasing heart rate.
  2. Stimulating the breakdown of glycogen.
  3. Redistributing blood to the core.
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5
Q

What is cell signalling? Why is this important for us?

A

Where cells communicate with each other by releasing chemicals that has an effect on another cell (target cell). For example, cells in nervous system communicate by secreting neurotransmitters that send signals to adjacent cells such as nerve or muscle cells.
Also, cells of pituitary gland secrete ADH to kidneys to maintain water balance. Hormones travel in blood and act as signals to distant cells.
In order to survive.

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6
Q

Explain what happens to sodium and potassium ions across a neurone cell membrane at the resting potential.

A
  1. Sodium-potassium pumps (by active transport) move move 3 sodium ions out of the neurone for every 2 K+ ions moved in. ATP needed to do this.
  2. When the cell is at rest, most K+ channels are open, so they allow facilitated diffusion of K+ out of the neurone, down their conc gradient. Therefore the membrane is permeable to K+, so some diffuse back through the potassium ion channels.
  3. The sodium ion channels are closed at rest. So the membrane isn’t permeable to sodium so they can’t diffuse back in. This creates a Na+ electrochemical gradient as there’s more positive Na+ outside the cell than inside.
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7
Q

The nervous system …
The endocrine system …

A

Provides an instant response.
Sustains this response.

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8
Q

What is adrenaline?

A

Amino acid derivative so it can’t enter the target cell. It must cause an effect within the cell without entering it.

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9
Q

Where are the adrenal glands found?

A

On top of each kidney.

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10
Q

What does middle region in an adrenal gland produce?

A

Cortisol - for stress management. It also works with insulin to maintain blood glucose levels. Also helps maintain blood pressure. Regulates metabolism.

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11
Q

What is the function of the adrenal cortex?

A

Controlled by pituitary gland and uses cholesterol to manufacture corticosteroid hormones.

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12
Q

Explain what happens to the body when you are hot.

A
  1. Sweat - water evaporates from skin to cool it down.
  2. Hairs lie flat - less insulating air is trapped. Heat can be lost more easily. ERECTOR PILI MUSCLES relax.
  3. Vasodilation - ARTERIOLES near surface of the skin dilate. More heat is lost from skin.
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13
Q

Explain what happens to the body when you are cold.

A
  1. Shiver - increase respiration in muscles so more thermal energy is released.
  2. More adrenaline and thyroxine are produced so more metabolism.
  3. Hairs lie flat - traps an insulating layer of air to prevent heat loss. ERECTOR PILI MUSCLES contract.
  4. Vasoconstriction - ARTERIOLES near surface of skin contract.
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14
Q

Thermoreceptors in skin …
Thermoreceptors in hypothalamus …

A

Detects external temp.
Detects temp of blood.

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15
Q

What is the function of thermoreceptors?

A

Send impulses along sensory neurones to the hypothalamus, which sends impulses along motor neurones to effectors. The effectors respond by returning the body back to normal.

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16
Q

Why are you more hungry when you’re cold?

A

Higher metabolic rate, so more glucose for respiration of contracting muscles as you shiver.

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17
Q

What is the first and second messenger for adrenaline?

A

1st - adrenaline that transmits a signal around the body.
2nd - cAMP transmits signal inside the cell.

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18
Q

What is an ectotherm?

A

Depends on external heat sources. Their body temperature changes if temp in environment changes.

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19
Q

What is an endotherm?

A

Uses internally generated heat to maintain body temperature, regardless of environment.

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20
Q

Mammals are …
Reptiles/fish/amphibians are …

A

Endotherms.
Ectotherms.

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21
Q

Thermoreceptors are found in the …

A

Thermoregulatory centre in hypothalamus.

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22
Q

What happens during vasodilation/constriction?

A

ONLY the sphincters contract, the vessels don’t. The vessel lumen dilates/constricts.

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23
Q

Define negative feedback.

A

Returns a change back to its normal value, to ensure a set point.

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24
Q

Define homeostasis.

A

Maintaining internal environment and adjusting to changing external conditions.

25
Q

Define stimulus.

A

Change in an organisms internal or external environment.

26
Q

Define receptor.

A

A cell that detects a specific stimulus.

27
Q

What is the integrating centre?

A

Region in the brain, usually the hypothalamus, that signals part of the body to respond to stimuli.

28
Q

What is an effector?

A

Organ or cell that acts in response to a stimulus.

29
Q

State the order of transmission of a message around the body.

A
  1. Stimulus
  2. Receptor
  3. Integrating centre
  4. Effector
  5. Response
30
Q

Chemoreceptors detect (chemicals) low pH in blood so …

A

Medulla stimulates increased rate and depth of breathing. More removal of CO2 in body, so level of CO2 decreases and blood pH returns to normal.

31
Q

Differences between endocrine and exocrine?

A

Endocrine - produce and secrete hormones into bloodstream like pituitary gland.
Exocrine - secretes through ducts like salivary glands.

32
Q

What is melatonin?

A

Helps you to sleep.

33
Q

Characteristics of nervous system?

A

Faster reaction, more localised, uses nerve impulses/ACTION POTENTIAL, lasts for short time.

34
Q

Characteristics of endocrine system?

A

Slower reaction, spread over a larger area, uses hormones transported in blood, lasts long time.

35
Q

The adrenal glands have …

A

A lot of functions, both nervous and endocrine systems.

36
Q

What is the centre of the adrenal gland called?

A

Medulla - produces peptide hormones.

37
Q

Surrounding the medulla is the …

A

Cortex - produces corticosteroids.

38
Q

Adrenal cortex produces …

A
  1. Mineralocorticoids (aldosterone)
  2. Glucocorticoids
  3. Androgens
39
Q

What does mineralcorticoids like aldosterone do?

A

Controls concentration of Na+ and K+ in blood which helps maintain blood pressure.

40
Q

What is glucocorticoids?

A

Help control metabolism of carbohydrates and proteins in liver . Cortisol is for stress and raises metabolism.

41
Q

Cortisol and aldosterone stimulate breakdown of …

A

Proteins and fats into glucose, so increases amount of energy available to fuel brain/muscles. Also suppresses the immune system and increases blood volume.

42
Q

Androgens are …

A

Sex hormones like oestrogen.

43
Q

Steroid hormones can diffuse directly through the …

A

Phospholipid bilayer as they’re lipid-soluble molecules.

44
Q

Function of the adrenal medulla?

A

Releases adrenaline (non-steroid) in response to shock. Heart rate is increased and blood glucose increased.

45
Q

What is noradrenaline?

A

Increases heart rate, widens pupils, widens air passages in lungs, narrows blood vessels in non-essential organs.

46
Q

Protein hormones cannot diffuse directly through the …

A

Phospholipid bilayer as they’re water soluble molecules, they won’t fit through channel proteins as they’re too large and don’t have specific carrier proteins to enter through.

47
Q

What communication systems are in your body?

A

Nervous system and endocrine system. They regulate body processes through chemical and electrical signals between cells.

48
Q

Neuronal and hormonal systems are examples of …

A

Cell signalling

49
Q

How do red blood cells communicate with the body?

A

They don’t have nuclei or typical signaling mechanisms like other cells; their communication is mainly through chemical transport and gas exchange with oxygen and carbon dioxide.
They bind oxygen in the lungs and release it in tissues, facilitated by haemoglobin. Additionally, RBCs help regulate pH levels and carry signaling molecules, such as nitric oxide, which plays a role in vasodilation and blood flow regulation.

50
Q

How do plants coordinate their growth and responses?

A

Plant hormones (like auxins, gibberellins, cytokinins) regulate growth, development, and responses to environmental stimuli. Auxins promote cell elongation and can direct growth toward light.
Environmental Cues: Plants respond to light (phototropism), gravity (gravitropism), and water availability (hydrotropism), adjusting their growth patterns accordingly.
Also, plant cells communicate through plasmodesmata, allowing the exchange of signaling molecules and nutrients.

51
Q

Hormone receptors:
Antigens:
Signal receptor:
Binding site:

A

Communication between cells.
Cell recognition.
Coordination of actions to trigger a response inside the cell.
Neurotransmitters/antibodies.

52
Q

How do cells communicate with each other?

A

Sending and receiving signals across the cell membrane with receptors.

53
Q

Describe some examples of signalling.

A
  1. Paracrine signalling - between cells that are close together.
  2. Endocrine signalling - between cells that are far apart, which involves the signalling molecule being transported in the circulatory system. The signalling molecules are always hormones.
  3. Synaptic signalling.
  4. Hormonal signalling.
54
Q

What is the difference between excretion and secretion?

A

Excretion - elimination of waste material from the living organisms.
Secretion - transport of material from one part of the body to another.

55
Q

Describe an acinar cell.

A

Specialized exocrine cells in the pancreas and salivary glands. In the pancreas, they produce digestive enzymes like amylase, lipase, and proteases, which are secreted into the small intestine to aid in digestion. In salivary glands, acinar cells produce saliva. These cells are arranged in clusters called acini, which help in the secretion of their products.

56
Q

What are alpha cells in the pancreas?

A

Endocrine cell in the islets of Langerhans. Produces and secretes the hormone glucagon, which converts glycogen to glucose in the liver, raising blood sugar levels when they are low.

57
Q

What are beta cells?

A

Beta cells are endocrine cells in the pancreas that are primarily responsible for producing and secreting insulin. It facilitates the uptake of glucose into cells and promoting its storage as glycogen in the liver.

58
Q

What is cyclic AMP? How is it created/broken down?

A

Signalling molecule derived from ATP and is a secondary messenger. It transmits signals from hormone.
Adenylate cyclase converts ATP to cAMP, while phosphodiesterases break it down.

OCR Biology (11 decks)

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