Hormones and the endocrine system

Lerne es beim Spielen

Beantworte diese Fragen für Energie, dann angle und erkunde. Kein Konto nötig.

Für Lehrkräfte: sofort einsetzbare Lektionsfolien, Lernnotizen für Hormones and the endocrine system (MYP Biology, Year 4) — nutze sie in deiner Lektion oder starte das Thema als interaktive Klassenaktivität, die deine Lernenden als Live-Spiel spielen.

Lektionsnotizen

Big idea: chemical messengers keep the body in balance

Big idea (key concept): Relationships. The glands, the blood and the body's cells form a relationship: the glands send a signal, and only certain cells are able to receive it.
Related concept: Balance. Many hormones work in pairs or in loops that keep conditions such as blood glucose and metabolic rate steady, even when you eat, rest or exercise.
Global context: Identities and relationships. Hormones help to decide how you grow, how you react to danger and when you reach puberty. They are part of what shapes each person.
A hormone is a chemical messenger. It is made in an endocrine gland (a gland with no duct), released directly into the blood, and carried round the whole body in the blood plasma.
A hormone only affects its target cells. Target cells have receptor molecules with a shape that matches the hormone. Cells with no matching receptor ignore it, even though it reaches them.
Nervous and hormonal control compared. The nervous system uses electrical impulses along neurones: the response is very fast, short-lived and acts on a precise place. The hormonal system uses chemicals in the blood: the response is slower, longer-lasting and often acts on several parts of the body.

The main endocrine glands

The pituitary gland at the base of the brain is sometimes called the master gland, because it releases hormones that control other glands. It releases FSH and LH (reproduction), TSH (the thyroid), ADH (water balance) and growth hormone.
The thyroid gland in the neck releases thyroxine, which controls metabolic rate. The adrenal glands, above the kidneys, release adrenaline.
The pancreas releases insulin and glucagon, which control blood glucose. The ovaries release oestrogen and progesterone, and the testes release testosterone.
Hormones in the menstrual cycle (a brief look). FSH from the pituitary makes an egg mature in the ovary and makes the ovary release oestrogen. Oestrogen repairs and thickens the lining of the uterus. LH from the pituitary causes ovulation, the release of the egg, about the middle of the cycle. Progesterone keeps the uterus lining thick.
Hormones control growth, development, reproduction and the balance of conditions inside the body. You will meet blood glucose control in more detail in the next topic.

Adrenaline and thyroxine

Adrenaline is released by the adrenal glands when you are frightened, excited or stressed. It prepares the body for fight or flight.
Adrenaline makes the heart beat faster and breathing faster, which sends more oxygen and glucose to the muscles. It causes the liver to release glucose into the blood, and widens the pupils. Blood is diverted towards the muscles, away from the digestive system.
The effects start within seconds but fade after a few minutes, because the hormone is broken down and removed from the blood. It acts more slowly than a nerve impulse, but its effect lasts longer.
Thyroxine is released by the thyroid gland. It controls metabolic rate: how fast the cells use energy. It is needed for normal growth and development.
Thyroxine is controlled by negative feedback. If the level of thyroxine in the blood falls, the pituitary releases more TSH, which tells the thyroid to release more thyroxine. When the level rises again, less TSH is released. The level stays close to the set point.

The negative feedback cycle

Insulin and glucagon: two hormones, one balance

Cells need a steady supply of glucose for respiration. If the level of glucose in the blood is too high or too low, cells and organs are harmed. The pancreas detects the level and releases the right hormone.
After a meal, blood glucose rises. The pancreas releases insulin. Insulin makes body cells take up glucose and makes the liver convert glucose into glycogen (a storage carbohydrate). Blood glucose falls back towards normal.
Between meals or during exercise, blood glucose falls. The pancreas releases glucagon. Glucagon makes the liver break down glycogen into glucose and release it into the blood. Blood glucose rises back towards normal.
This is negative feedback: the response reverses the change that triggered it. Two hormones with opposite effects give very precise control, as if a driver can both accelerate and brake.
If blood glucose control fails, the level can stay too high. This is the cause of diabetes, which is studied in the next topic.

Insulin and glucagon control blood glucose

Plant hormones: auxin and tropisms

Plants also use hormones. Auxin is made in the tips of shoots and roots. It controls growth in a particular direction.
A tropism is a growth response of a plant to a directional stimulus. Phototropism is a response to light and gravitropism is a response to gravity. Growing towards the stimulus is positive, and growing away from it is negative.
Phototropism in a shoot: light from one side makes auxin move to the shaded side. Auxin makes cells elongate, so cells on the shaded side grow longer than cells on the lit side, and the shoot bends towards the light. This helps the leaves to absorb more light for photosynthesis.
Gravitropism: in a shoot lying on its side, auxin collects on the lower side and makes cells there elongate, so the shoot grows upwards (negative gravitropism). In a root, auxin collects on the lower side too, but here it slows elongation, so the upper side grows faster and the root bends downwards (positive gravitropism).
Auxin has uses in farming and gardening: some synthetic auxins are used as selective weedkillers that harm broad-leaved weeds but not cereals, and as rooting powder for cuttings.

Auxin and phototropism in a shoot tip

Think like a scientist: does the shoot tip detect the light?

Question: which part of a young shoot detects light, and which part bends? Use identical seedlings (for example cress or oat seedlings) with light shining from one side only.
Compare four treatments: A, intact seedlings; B, the tip removed; C, the tip covered with a small foil cap; D, the tip uncovered but the lower part covered with foil. The independent variable is the treatment. The dependent variable is how much the shoot bends (angle) or grows (mm) after a set time.
Control variables: the species and age of the seedlings, the light intensity and its distance, the temperature, the water supply and the time.
To make results reliable, use at least five seedlings per treatment and calculate a mean. Say what you would do about any result that looks like an anomaly.
Inquiry task 1: predict the result for each treatment A to D and explain your predictions using auxin. Inquiry task 2: a student uses one seedling per treatment and concludes that the tip makes auxin. Evaluate the evidence and suggest two improvements.

Folien

Step through every slide for this topic — plus flashcards and revision notes — with a free account.

REGISTRIEREN — GRATIS ANMELDEN

Übungsfragen

Gratis-Vorschau — 8 von 50 Fragen. Registriere dich, um alle zu sehen.

1.What is a hormone?
Easy
- AA muscle that carries out a response
- BA chemical messenger carried in the blood
- CA cell that detects a stimulus
- DAn electrical impulse in a neurone
2.How do hormones travel to their target organs?
Easy
- AThrough the air
- BAlong neurones
- CAlong the digestive system
- DIn the blood plasma
3.Hormones are made by endocrine glands.
Easy
True or false?
4.What is a target cell?
Easy
- AA cell that has receptors matching a particular hormone
- BA cell found only in the brain
- CA cell that destroys hormones
- DA cell that makes every hormone in the body
5.Which gland makes insulin?
Easy
- AThe adrenal glands
- BThe pituitary
- CThe thyroid
- DThe pancreas
6.Which glands release adrenaline?
Easy
- AThe pancreas
- BThe ovaries
- CThe adrenal glands
- DThe thyroid
7.Match each gland to the hormone it releases.
Easy
- Thyroid
- Adrenal glands
- Ovary
- Pancreas
- Insulin
- Thyroxine
- Oestrogen
- Adrenaline
8.Complete the sentence.
Easy
Thyroxine controls the body's ____ rate.

Mehr Fragen

9.What does adrenaline do to the heart rate?
Easy
- AIt increases it
- BIt stops it
- CIt has no effect on it
- DIt decreases it
10.Adrenaline prepares the body for fight or flight.
Easy
True or false?
11.Which hormone lowers the level of glucose in the blood?
Easy
- AGlucagon
- BThyroxine
- CInsulin
- DAdrenaline
12.Which hormone raises the level of glucose in the blood?
Easy
- AThyroxine
- BInsulin
- CGlucagon
- DOestrogen
13.Insulin and glucagon have opposite effects on blood glucose.
Easy
True or false?
14.Complete the sentence.
Easy
The liver stores glucose in the form of ____.
15.Which system produces the faster response?
Easy
- AThe nervous system
- BBoth are exactly as fast
- CNeither makes a response
- DThe hormonal system
16.Which type of control usually gives the longer-lasting effect?
Easy
- ANerve impulses
- BHormonal control
- CThe pupil reflex
- DReflexes
17.Which plant hormone controls the growth of shoots and roots in response to light and gravity?
Easy
- AGlucagon
- BAdrenaline
- CInsulin
- DAuxin
18.What is a tropism?
Easy
- AA fast movement of a muscle
- BA chemical made in the pancreas
- CA change in blood glucose
- DA growth response of a plant to a directional stimulus
19.Shoots show positive phototropism.
Easy
True or false?
20.Which hormone is released by the testes?
Easy
- AInsulin
- BAdrenaline
- CThyroxine
- DTestosterone
21.Which hormone keeps the lining of the uterus thick after ovulation?
Medium
- ALH
- BFSH
- CGlucagon
- DProgesterone
22.Which row correctly describes hormonal control compared with nervous control?
Medium
- ASlower response, longer-lasting effect
- BSlower response, shorter-lasting effect
- CFaster response, shorter-lasting effect
- DFaster response, longer-lasting effect
23.A hormone reaches every part of the body in the blood, but only some cells respond. Why?
Medium
- AOnly some cells contain a nucleus
- BOnly some cells have a blood supply
- COnly some cells can use energy
- DOnly the target cells have matching receptor molecules
24.Which of these are effects of adrenaline? (select all that apply)
Medium
- AThe thyroid releases thyroxine
- BThe liver releases glucose into the blood
- CThe heart beats faster
- DDigestion speeds up
- EThe pupils become wider
25.Why is it useful for adrenaline to make the liver release glucose?
Medium
- AGlucose makes the heart muscle stop beating
- BGlucose gives the muscles more energy for respiration
- CGlucose widens the pupils directly
- DGlucose carries messages to the brain
26.The level of thyroxine in the blood falls below the set point. What happens next?
Medium
- AThe adrenal glands release adrenaline
- BThe pancreas releases insulin
- CThe pituitary releases less TSH, and the thyroid releases less thyroxine
- DThe pituitary releases more TSH, and the thyroid releases more thyroxine
27.Put these events in order for what happens after a meal that contains a lot of carbohydrate.
Medium
- The pancreas releases insulin
- Blood glucose falls towards normal
- Blood glucose rises
- The liver converts glucose to glycogen and cells take up glucose
28.Put these events in order for what happens when blood glucose falls between meals.
Medium
- Blood glucose rises towards normal
- Blood glucose falls
- The liver breaks down glycogen to glucose
- The pancreas releases glucagon
29.Which of these are effects of insulin? (select all that apply)
Medium
- ABody cells take up glucose from the blood
- BThe pancreas releases glucagon
- CThe liver converts glucose to glycogen
- DBlood glucose level falls
- EThe liver converts glycogen to glucose
30.Why is the control of blood glucose an example of negative feedback?
Medium
- AIt uses the nervous system only
- BThe response makes the change bigger
- CThe response reverses the change that caused it
- DIt only happens during exercise
31.Which hormone from the pituitary gland causes ovulation?
Medium
- AFSH
- BProgesterone
- CInsulin
- DLH
32.Which pair correctly matches a hormone with its role in the menstrual cycle?
Medium
- AProgesterone causes ovulation
- BLH repairs the lining of the uterus
- CFSH makes an egg mature in the ovary
- DOestrogen is released by the pituitary
33.A shoot is lit from the right only. What happens to auxin in the shoot tip?
Medium
- AIt moves to the shaded left side, so cells there elongate more and the shoot bends right
- BIt stays evenly spread, so the shoot grows straight up
- CIt is destroyed on the left side, so the shoot stops growing
- DIt moves to the lit right side, so cells there elongate more and the shoot bends left
34.Why does a root growing sideways bend downwards?
Medium
- AAuxin collects on the upper side and slows elongation there
- BRoots are not affected by auxin at all
- CAuxin collects on the lower side and slows elongation there, so the upper side grows faster
- DAuxin makes the lower side of the root grow faster
35.Auxin makes cells elongate in shoots.
Medium
True or false?
36.Which of these responses is controlled by a hormone rather than by a nerve impulse?
Medium
- ABlinking when dust enters the eye
- BA fall in blood glucose after insulin is released
- CPulling a hand away from a hot object
- DThe pupil getting smaller in bright light
37.
Here is an example set of data for one healthy volunteer's blood glucose after a sugary drink.
Time (minutes) Blood glucose (mmol/dm3)
0 4.8
30 8.6
60 6.9
90 5.6
120 5.0
By how much did blood glucose fall between 30 and 120 minutes?
Medium
38.A student investigates whether light direction affects how seedlings grow. Seedlings in set X get light from the right only. What is the independent variable?
Medium
- AThe direction the light comes from
- BThe height of the seedlings after three days
- CThe type of seed used in each set
- DThe temperature of the room
39.In the seedling investigation, which of these should be a control variable?
Medium
- AThe direction of the light
- BThe age and species of the seedlings
- CThe bending angle of the shoot
- DThe student's prediction
40.Describe how insulin and glucagon work together to keep the blood glucose level steady.
Medium
41.Using the example data after a sugary drink: 0 min 4.8, 30 min 8.6, 60 min 6.9, 90 min 5.6, 120 min 5.0 mmol/dm3. Between which two times did blood glucose fall the fastest, and what does that suggest?
Hard
- A30 to 60 minutes (fall of 1.7), suggesting insulin was having its strongest effect then
- B0 to 30 minutes (rise of 3.8), suggesting glucagon was having its strongest effect
- C90 to 120 minutes (fall of 0.6), suggesting insulin was having its strongest effect
- D60 to 90 minutes (fall of 1.3), suggesting insulin had just begun to act
42.A person touches a hot pan and pulls their hand away. A minute later their heart is still beating fast and they are shaking. Which statement explains both effects?
Hard
- ABoth are caused by insulin released from the pancreas
- BBoth effects are caused by a reflex arc and no hormones are involved
- CThe first is adrenaline and the second is a reflex
- DThe first is a nervous reflex, and the second is adrenaline, which lasts longer
43.Compare the two systems. Which statement is correct?
Hard
- ABoth travel in the blood, but nerves travel more slowly
- BBoth use electrical impulses, but hormones are faster
- CNerve impulses act on many organs and last longer; hormones act on a precise target
- DNerve impulses act on a precise target and are short-lived; hormones can act on many organs and last longer

44.

Seedlings were treated as follows, with light from the right only, and their growth was recorded after two days.

Treatment	Result
A: intact	Shoot bent towards the light
B: tip removed	Little growth, no bending
C: tip covered with foil cap	Grew straight up
D: tip uncovered, lower part covered with foil	Shoot bent towards the light

Which conclusion is best supported by these results?

Hard

AFoil makes seedlings grow faster
BThe lower part of the shoot detects the light
CLight has no effect on how seedlings grow
DThe tip detects the light and is needed for the bending response

45.
In a class experiment, shoot growth over two days was measured in five seedlings in each group.
Seedling Tip intact: growth (mm) Tip removed: growth (mm)
1 6 2
2 7 1
3 5 3
4 8 2
5 6 2
How many millimetres greater is the mean growth of the intact seedlings than that of the seedlings with the tip removed?
Hard
46.Why do the effects of adrenaline last longer than the effects of a nerve impulse?
Hard
- ANerve impulses are chemical and hormones are electrical
- BThe hormone stays in the blood until it is broken down or removed, while an impulse is brief
- CAdrenaline travels along neurones, which are slower
- DAdrenaline is made by the nervous system
47.A student wants more reliable results from the seedling investigation. Which changes would help? (select all that apply)
Hard
- AUse at least five seedlings per treatment and calculate means
- BPut the light at a different distance for each treatment
- CUse one seedling per treatment to save time
- DRepeat the whole experiment
- EUse seedlings of the same species and age in every group
48.Explain why adrenaline released from the adrenal glands only changes the activity of some cells, even though it reaches the whole body in the blood.
Hard
49.Plan an investigation to find out whether gravity affects the direction of root growth in seedlings. State what you would change, measure and keep the same, and how you would make the results reliable.
Hard
50.In negative feedback, the response makes the original change larger.
Hard
True or false?

Lernnotizen

## The big idea - **Hormones** are chemical messengers. They keep conditions in the body in **balance** and link glands, blood and target cells (**Relationships**, **Balance**). ## How hormones work - Made in **endocrine glands**, released into the **blood**, and carried to **target cells** that have matching **receptors**. - Compared with the nervous system: **slower**, **longer-lasting**, often **wider** in effect. ## Glands - **Pituitary** (master gland), **thyroid** (thyroxine), **adrenals** (adrenaline), **pancreas** (insulin, glucagon), **ovaries** and **testes**. - Menstrual cycle: **FSH** matures an egg, **oestrogen** thickens the lining, **LH** causes ovulation, **progesterone** maintains the lining. ## Adrenaline and thyroxine - Adrenaline: fight or flight (heart rate up, glucose released, pupils wider). - Thyroxine: metabolic rate, controlled by **negative feedback** with TSH. ## Blood glucose - High glucose: **insulin**, cells take up glucose, liver makes glycogen. Low glucose: **glucagon**, liver releases glucose. ## Plant hormones - **Auxin** makes cells elongate. Phototropism: auxin moves to the shaded side so the shoot bends towards light. Gravitropism: shoots up, roots down. ## Investigating - Change one variable, control the rest, repeat and use a mean. Check for anomalies.

Hormone: A chemical messenger made in an endocrine gland and carried in the blood.
Endocrine gland: A gland that releases hormones directly into the blood.
Target cell: A cell with receptors that match a particular hormone.
Pituitary gland: The master gland at the base of the brain that releases hormones controlling other glands.
Adrenaline: A hormone from the adrenal glands that prepares the body for fight or flight.
Thyroxine: A hormone from the thyroid gland that controls metabolic rate.
Insulin: A hormone that lowers blood glucose by making cells take up glucose and the liver store it.
Glucagon: A hormone that raises blood glucose by making the liver release glucose.
Glycogen: A storage carbohydrate made from glucose in the liver and muscles.
Negative feedback: A control system in which the response reverses the change that triggered it.
Metabolic rate: The rate at which the body's cells use energy.
Ovulation: The release of an egg from the ovary, caused by a surge in LH.
Auxin: A plant hormone that makes cells elongate.
Tropism: A growth response of a plant to a directional stimulus.
Phototropism: Growth of a plant shoot towards light.

Karteikarten

What is a hormone?

A chemical messenger made in an endocrine gland and carried in the blood.

What is an endocrine gland?

A gland that releases hormones directly into the blood.

Why do only target cells respond to a hormone?

Only they have receptor molecules with a shape that matches the hormone.

Compare hormonal and nervous control.

Hormonal is slower, longer-lasting and often wider; nervous is very fast, short-lived and precise.

Which gland is called the master gland?

The pituitary gland.

What does the thyroid gland release?

Thyroxine, which controls metabolic rate.

What does adrenaline do?

Prepares the body for fight or flight: faster heart rate and breathing, glucose released, wider pupils.

Where is adrenaline released from?

The adrenal glands, above the kidneys.

How is thyroxine level controlled?

By negative feedback: low thyroxine makes the pituitary release more TSH.

What does insulin do?

Lowers blood glucose: cells take up glucose and the liver converts it to glycogen.

What does glucagon do?

Raises blood glucose: the liver converts glycogen to glucose and releases it.

What is negative feedback?

A response that reverses the change that triggered it, keeping a condition steady.

What does FSH do?

It makes an egg mature in the ovary and stimulates oestrogen release.

What does LH do?

It causes ovulation, the release of an egg from the ovary.

What is auxin?

A plant hormone made in shoot and root tips that makes cells elongate.

How does a shoot bend towards light?

Auxin moves to the shaded side, so cells there elongate more.

Why does a root grow downwards?

Auxin on its lower side slows elongation, so the upper side grows faster.

How do you make a hormone investigation reliable?

Use many samples, control variables, repeat and calculate a mean.

Unlock all 50 questions, flashcards & more

Erstelle ein Gratis-Konto, um alle Fragen, Folien, Karteikarten und Lernnotizen zu diesem Thema zu sehen.

REGISTRIEREN — GRATIS ANMELDEN

Altklausuren

Altklausuren-Übungen für dieses Thema kommen bald.

Bald verfügbar

Time (minutes)	Blood glucose (mmol/dm3)
0	4.8
30	8.6
60	6.9
90	5.6
120	5.0

Seedling	Tip intact: growth (mm)	Tip removed: growth (mm)
1	6	2
2	7	1
3	5	3
4	8	2
5	6	2