Chapter 5 : The Endocrine System Flashcards Preview

Daphne VCE Biology 2016 > Chapter 5 : The Endocrine System > Flashcards

Flashcards in Chapter 5 : The Endocrine System Deck (52)
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1
Q

What is inter-cellular fluid? State examples.

A

Inter-cellular fluid is the fluid located inside the cells, mainly the cytosol.

2
Q

True or False.

The internal environment of a multicellular organism is mostly made of tissue fluid.

A

True.

3
Q

What is the internal environment of a multicellular organism made of?

A

Extracellular fluid.

4
Q

Define homeostasis.

A

Homeostasis is the condition of a relatively stable internal environment, maintained within narrow limits.

5
Q

Name some of the variables maintained under homeostasis.

A

Blood pH level, blood glucose level, blood volume and pressure, body temperature, ion concentration, etc.

6
Q

Define negative feedback.

A

Negative feedback is a response mechanism in which a response produced in the opposite direction counteracts the effect of the stimulus (either by raising or lowering the stimulus), returning the body back to its normal state.

7
Q

State the sequence for negative feedback.

A

Stimulus (an object or event that causes a change) - receptor - control center - effector - response.

8
Q

State the (detailed) process for negative feedback.

A

A change in a key variable is detected (stimulus), and a signal is produced. The signal is detected by a receptor (sensor) and is transmitted to the control center. The control center sends another signal to the target organ, gland or muscle (effector). The effector responds to the signal by producing a response in the opposite direction to counteract the effect of the stimulus. The original signal decreases and the process continues until it is switched off.

9
Q

Name an example of negative feedback.

A

For example, bright light (stimulus) falls onto your eyes (sensor). The muscle in the eyes (effector) constricts (response), so that less light can get into your eye, and vice versa.

10
Q

How is homeostasis maintained?

A

Through negative feedback systems, which are mainly the endocrine and nervous systems.

11
Q

What is the hypothalamus?

A

The hypothalamus is a small gland located at the base of the brain. It detects changes in blood passing through it, and is involved in water balance in blood, temperature regulation and blood pressure regulation. The hypothalamus can send messages through nerves or produce hormones.

12
Q

Define positive feedback.

A

Positive feedback is a response mechanism that increases the effect of the stimulus, moving the body further away from its normal state.

13
Q

Name the hormones that control blood glucose regulation.

A

Insulin (increases blood glucose level) and glucagon (decreases blood glucose level).

14
Q

Where is the hormone glucagon produced?

A

Glucagon is secreted by alpha cells in the pancreas.

15
Q

Name examples of positive feedback.

A

Contractions during childbirth, the production of clotting factors in blood after an injury, etc.

16
Q

Where is the hormone insulin produced?

A

Insulin is secreted by beta cells in the pancreas.

17
Q

What happens when blood glucose level reduces below normal?

A

Glucagon is secreted by alpha cells in the pancreas, and released into the bloodstream, where it targets mainly the liver and muscle cells. Glucagon binds to receptors located on the surface of the plasma membrane, and uses cAMP as a second messenger. cAMP activates a range of other proteins. Responses include the inhibition of the secretion of insulin by beta cells, resulting in the decrease uptake of glucose by the cells, glycogen in the liver being converted into glucose and released into the bloodstream and stored fat being converted into carbohydrates.

18
Q

What happens when blood glucose level rises above normal?

A

Insulin is secreted by beta cells in the pancreas, and released into the bloodstream, where it targets mainly liver and muscle cells. Insulin binds to kinase receptor located on the surface of the plasma membrane, which also acts as a second messenger. The kinase receptor activates a range of other proteins. Responses include increasing the rate of glucose uptake by cells, converting glucose into glycogen to be stored in the liver, glucose and glycogen being converted into fat and the inhibition of the secretion of glucagon, resulting in the decrease conversion of stored glycogen into glucose.

19
Q

What is extracellular fluid? State examples.

A

Extracellular fluid is the fluid located outside the cells, such as tissue fluid (interstitial fluid) and blood plasma.

20
Q

Define signalling molecules.

A

Signalling molecules are molecules that enable cell communication, such as hormones, neuro-hormones and neurotransmitters.

21
Q

Name the types of cell signalling.

A

Autocrine, paracrine, endocrine and contact dependent signalling.

22
Q

What is autocrine signalling?

A

Cell signalling from neighboring cells of the same type or within the cell itself, such as immune signalling.

23
Q

What is paracrine signalling?

A

Cell signalling from nearby cells of different types. It has short-lived local effects and the signal molecule will diffuse through the extracellular fluid into the other cell, such as neurotransmitter signalling.

24
Q

What is endocrine signalling?

A

Cell signalling from cells in distant parts of the body travelling through the bloodstream to the target cell.

25
Q

What is contact-dependent signalling?

A

Cell signalling that targets a cell that is connected by gap junctions.

26
Q

Define signal transduction.

A

Signal transduction involves getting a signal from a target cells exterior to the cells interior during which the cell converts one kind of signal into another, by a series of relay molecules and other proteins. Within a cell, signal transduction amplifies the signal that the original hormone molecule produced.

27
Q

Name examples of the results of signal transduction in cells.

A
  • Altering gene expression, which influences the production of proteins, including enzymes (mainly steroid hormones).
  • Altering the permeability of the cell membrane.
  • Activating/deactivating enzymes, which affects cellular metabolism.
28
Q

Define hormone.

A

A hormone is a chemical that is produced in one part of an organism and transported in the bloodstream to another part where it exerts its effect.

29
Q

True or False.

Hormones always enter the bloodstream, and act on cells that are in another part of the body.

A

False.

They can act on the cell that produced the hormone, or act on nearby cells.

30
Q

If hormones travel through the bloodstream, why don’t all cells of the body respond to that hormone?

A

Only cells with specific receptors for that hormone will respond to the hormone signal.

31
Q

Name the three main types of hormones.

A

Amino acid derivatives, protein (over 200 amino acids) and peptide (under 200 amino acids) hormones, and steroid hormones.

32
Q

Describe protein based hormones in as much detail as possible.

A

Protein based hormones, such as insulin and thyroid gland hormone, are hydrophilic in nature, which means that they travel in the bloodstream but are unable to pass through the cell membrane. Their receptors are located on the surface of the cell membrane, and the response produced is rapid, as the enzymes being activated are already present. However, the duration of the response is relatively short. Transduction method includes the generation of second messenger that alters the activity of enzymes already in the target cell.

33
Q

Describe steroid based hormones in as much detail as possible.

A

Steroid based hormones, such as testosterone, are hydrophobic in nature, which means that they are transported in blood by carrier proteins and are able to pass through the cell membrane. Their receptors are located inside the cytosol of the cell, and the response produced is longer, as the hormone/receptor complex has to interact with DNA to alter the rate of protein synthesis. However, the duration of the response is longer. Transduction method includes altering the rate of gene transcription thereby altering the rate of protein synthesis.

34
Q

True or False.

Hormones last forever.

A

False.
Once their effect has been exerted they are no longer needed. They are degraded by cell enzymes and excreted via the kidneys or faeces.

35
Q

Define pheromones.

A

Pheromones are chemical signalling molecules that are produced by animals, usually insects. They are often used as sex attractants and influence the behavior of members of the same species.

36
Q

True or False.

Pheromones are species-specific.

A

True.

37
Q

True or False.

The action of pheromones is external, and not internal.

A

True.

38
Q

True or False.

Plants lack a nervous system, so their responses are governed by hormones or chemical regulators.

A

True.

39
Q

Name the five main groups of hormones.

A

Auxins (IAA), gibberellins, cytokinins, abscisic acid and ethylene.

40
Q

What is the effect of auxins?

A

Stimulate cell elongation, cell division in the cambium and differentiation of the phloem and xylem. Suppress growth of lateral buds (apical dominance), and mediate trophic responses to light and gravity. Suppress fruit ripening, stimulate growth of flower parts.

41
Q

What is the effect of gibberellins?

A

Promote cell division and cell elongation in plant shoots.

42
Q

What is the effect of cytokinins?

A

Stimulate cell division in the middle layer of cells in leaves.

43
Q

What is the effect of abscisic acid?

A

Generally acts as an inhibitor, promotes stomata closure, particularly during times of water stress. Also stimulates dormancy in seeds and buds.

44
Q

What is the effect of ethylene?

A

Promotes fruit ripening, leaf fall, stress responses.

45
Q

Define tropism.

A

The growth of a plant in response to a specific stimulus, such as light or gravity.

46
Q

Define phototropism.

A

Phototropism is the growth of a plant in response to light.

47
Q

Define geotropism.

A

Geotropism is the growth of a plant in response to gravity.

48
Q

Which part of the plant shows positive geotropism?

A

The roots.

49
Q

Which part of the plant shows negative geotropism?

A

The shoots.

50
Q

Why does a coleoptile bend towards the light?

A

Growing coleoptiles bend toward the light as auxin is more concentrated in the side of the plant that is not exposed to the sunlight, resulting in the elongation of one side of the plant, causing the plant to bend towards the light.

51
Q

Define thighmotropism.

A

Thighmotropism is the growth of a plant in response to touch.

52
Q

Define photoperiodism.

A

Photoperiodism is the growth of a plant in response to seasonal changes in day length.