Biology B11: Hormonal Coordination

Hormones

Proteins produced by glands

• Chemical messages

Endocrine system

Composed of glands which secrete hormones directly into the bloodstream

How does the endocrine system work?

1. Glands secrete hormones into the BS

2. Blood carries hormones to target organ, where it produces an effect

Endocrine system vs nervous system:

1. Uses

2. Travels down what/carried in?

3. Signalling speed

4. Effect

Compared to the nervous system the effects are slower but act for longer

Endocrine:

1. Hormones (chemicals)

2. Bloodstream

3. Slow

4. Longer lasting effect

Nervous:

1. Electrical impulses

2. Neurones

3. Fast

How do hormones travel?

Via the blood

Hormones that give a rapid response + function

1. Insulin - controls blood glucose

2. Adrenaline - prepares body for fight / flight

Slow acting hormones with long term effects examples

1. Growth hormones

2. Sex hormones

Glands in the endocrine system

1. Pituitary

2. Thyroid

3. Adrenal

4. Pancreas

5. Ovary (F)

6. Testis (M)

What hormones do these glands produce?

1. Pituitary

2. Thyroid

3. Adrenal

4. Pancreas

5. Ovary (F)

6. Testis (M)

1. ADH, FSH, TSH

2. Thyroxine

3. Adrenaline

4. Insulin + glucagon

5. Oestrogen, progesterone

6. Testosterone

Pituitary gland

• Master gland in the brain

• Secretes several hormones into the blood in response to body conditions

• Pituitary hormones → act on other glands to stimulate other hormones to be released to bring abt effects

In response to what does the pituitary gland secrete hormones?

Changes in the internal environment

Role of ADH

Affects amount of urine produced by the kidney

What can hormones released by the pituitary gland do?

1. Direct effect on the body (ADH, growth hormone)

2. Affect other endocrine glands + stimulate them to realise hormones → cause a specific effect (FSH, TSH)

Follicle-stimulating hormone (FSH)

Stimulates ovaries to make oestrogen (F sex hormone)

TSH

Stimulates thyroid gland to make thyroxine (controls rate of metabolism)

Why is glucose needed in every cell?

Release energy by respiration

• Conc of glucose in blood must be constant (homeostasis)

What monitors + controls blood glucose concentration?

Pancreas

Glucose

Sugar used in respiration

Glycogen

Storage carbohydrate in the liver + muscles

Glucagon

Hormone that stimulates the liver to break down glycogen to glucose

Why may a person’s blood glucose concentration be high?

After eating a carbohydrate rich meal

How does the body respond to high blood glucose concentration to return it to its normal level (homeostasis)?

1. Pancreas produces insulin (hormone)

2. Insulin triggers glucose to move from the blood into

   body cells

3. + Triggers liver + muscle cells convert excess glucose into glycogen for storage

What can insulin do?

Trigger:

1. Glucose to move from the blood into BC

2. Liver + muscle cells to store excess glucose as glycogen

What substance does the pancreas release and why?

Hormones (insulin + glucagon)

• To regulate glucose levels if too high/low

What happens to excess glucose when glycogen stores in the liver and muscle cells are full?

Converted to lipids + stored

Cause of obsesity?

1. Eating lots of food → build-up of glucose

2. More than liver + muscles can store as glycogen

3. More and more stored as lipids

What causes blood glucose concentration to fall?

1. Exercise

2. Fasting (eg in between meals)

How does the body respond to low blood glucose concentration to return it to its normal level (homeostasis)?

1. Pancreas releases glucagon into the BS

2. Triggers liver cells to convert glycogen → glucose

3. Glucose released into blood

How do insulin and glucagon form a negative feedback cycle?

Controls GC but have opposite effects

• GC rises → insulin released → GC falls

• GC falls → glucagon released → GC rises

Type 1 diabetes

Pancreas fails to produce sufficient insulin

• So uncontrolled high blood glucose levels

How does the graph showing the blood glucose concentration of people with type 1 diabetes vs no diabetes show the effects of type 1 diabetes?

When GC rises it stays at a high level

• As pancreas can’t produce sufficient insulin

Treatment of type 1 diabetes

Insulin injections

Type 2 diabetes

Body cells stop responding to insulin produced by the pancreas

• Blood glucose levels rise too high

Treatment of type 2 diabetes

1. Carbohydrate controlled diet

   • Prevents BGC rising too high

2. Regular exercise

3. Losing weight

Risk factor for type 2 diabetes

Obesity

Obese person → diet high in carbs → overproduction of insulin → resistance to it

How can type 1 diabetes cause you to loose weight?

1. Less insulin → glucose can’t enter body cells → tired + lack energy

2. Fat + protein broken down instead for fuel

When a person with type 1 diabetes injects themselves with insulin, how does it help them?

1. Converted to glycogen in the liver

2. Prevents GC from getting too high (allows glucose to be taken into body cells)

3. When GC falls, glycogen → glucose

Negative feedback

Help maintain conditions in the body within an optimal narrow range

• Detect level of substance has ↑/↓ → triggers response to bring back og level

• Controls: blood glucose level, core body temp, menstrual cycle

How does negative feedback work

NF response causes the opposite of the initial change

• Level rises → changes occur to reduce it → original level

• Level falls → changes occur to increase it → original level

Adrenal glands

• Produce adrenaline during times of fear + stress → released into blood

• Not controlled by negative feedback loop

How do the adrenal glands work?

1. Produce adrenaline during times of fear/stress

2. Adrenaline released into the blood

How does adrenaline prepare the body for flight or fight

Increase heart rate

• So more O2 + glucose delivered in blood to brain + muscles (needed for AR)

Thyroid gland

• Base of neck

• Releases thyroxine hormone

Role of thyroxine

1. Stimulates body’s basal metabolic rate

   • Body’s chemical reactions happen faster

2. Growth + development

What is the level of thyroxine in the blood controlled by?

Negative feedback

How does the negative feedback cycle respond to decreased levels of thyroxine in the blood?

• Level of thyroxine in blood monitored by brain

Pituitary gland releases TSH hormone into BS

• TSH triggers thyroid gland to release more thyroxine into the blood

What happens if level of thyroxine are too high?

• Release of TSH is inhibited

• → Less thyroid released from thyroid gland

Are adrenaline and thyroxine controlled by negative feedback?

1. Adrenaline - no

2. Thyroxine - yes

Primary sexual characteristics

Ones you are born with

• Reproductive organs → ovaries/testes

Role of reproductive organs

Produce male/female sex hormones + gametes (sex cells) that join tog in reproduction

Male reproductive hormone

Testosterone produced by testes

Testosterone

Stimulates sperm production by testes

Main female reproductive hormone

Oestrogen produced by ovaries

What happens once puberty begins in females?

1. Eggs in ovaries start to mature

2. Every 28 days an egg is released- ovulation

Ovulation

Ovaries release an egg

What happens during the menstrual cycle (explain w/o hormones)

1. Every 28 days ovulation

2. To prepare, uterus (womb) lining becomes thick + spongy

3. Same time eggs mature in ovaries

4. 14 days after egg enters uterus

5. Sperm present → egg fertilised → implanted into uterus wall → develop into baby

6. Egg not fertilised → egg + uterus lining released 14 days after ovulation (period)

How does the uterus lining prepare for ovulation?

Becomes thick and spongy

Period

When the egg is not fertilised so egg + uterus lining released

Follicle-stimulating hormone (FSH)

• Causes egg to mature in ovary

• Stimulates ovary to produce oestrogen

Luteinising hormone (LH)

Stimulates the egg to be released, ovulation

Oestrogen

• Causes uterus lining to develop

• Inhibits release of FSH

• Stimulates release of LH

Progesterone

• Maintains uterus lining (keeps thick in case fertilised egg implants)

• Inhibits release of FSH + LH

How do hormones interact during the menstrual cycle?

1. FSH released by pituitary gland

2. FSH travels in blood to ovaries

3. Makes eggs mature + triggers ovaries to make oestrogen

4. Oestrogen → lining of uterus thickens + stops PG from releasing FSH

5. PG releases LH → triggers ovulation

6. Ovary releases egg then produces progesterone

7. Progesterone → stops PG from releases FSH and LH + keeps uterus lining thick

8. No fertilisation → progesterone levels fall

9. Period → uterus lining + egg released

Why does progesterone stop the pituitary gland releasing FSH and LH

Prevents any more eggs from maturing + being released

Where are these hormones made:

1. LH

2. FSH

3. Oestrogen

4. Progesterone

1. LH → Pituitary gland

2. FSH → Pituitary gland

3. Oestrogen → Ovaries

4. Progesterone → Ovaries

Graphs of hormones during the menstrual cycle

1. Level of FSH rises → triggers ovaries to release oestrogen

2. Level of oestrogen rises → inhibits production of FSH → level of FSH falls

3. Oestrogen triggers release of LH → LH level rises + peaks at day 14

4. LH → ovulation → ovaries release progesterone → progesterone level rises

5. No fertilisation → progesterone falls + period

Where and when is progesterone produced in the menstrual cycle?

By the empty egg follicle in the ovary after ovulation

Days of the menstrual cycle

1. 0-5: old egg + uterus lining leaves body

2. 14 days after, 12-16: ovulation, egg released

3. 14 days after, 20-18, new egg in womb

Menopause

When the supply of eggs in the ovaries runs out

• Can’t have children

Contraception

Ways to prevent fertilisation

Sterilisation

Surgical forms of contraception

Main pros and cons of hormonal methods of contraception

Pros:

1. Lasts a while

Cons:

1. Side effects

2. Doesn’t protect from STIs

Main pros and cons of non-hormonal methods of contraception

Pros:

1. No side effects

Cons:

1. Doesn’t always protect from STIs

Benefits of contraception- general

Prevents:

• Unwanted pregnancies

• Pregnancies that risk the mother’s health

When does infertility occur?

When a couple unable to conceive naturally

• Men → reduced sperm count

• Women → issue with reproductive system (low level of reproductive hormones)

How does a fertility drug work to treat infertility?

Woman has low FSH levels, so:

• FSH + LH given to a women

• Causes her to ovulate more than usual

• Increases chances of her becoming pregnant the normal way (sex)

Causes of infertility

1. Age

2. Obesity

3. Eating disorders

Stages of In Vitro fertilisation to treat infertility

1. Mother treated with FSH + LH → stimulates several eggs to mature + released

2. Eggs collected from mom

3. Sperm from father collected

4. Sperm to fertilise eggs in a lab

5. Fertilised eggs develop into embryos

6. When embryos = tiny ball of cells → 1 or 2 embryos inserted into mother’s uterus

7. Embryos develop in mom the usual way

Benefits of In Vitro Fertilisation (IVF)

1. Gives the women a chance to have a baby of her own

2. Unused eggs used for research

Issues with IVF

1. Low success rates

2. Emotionally + physically stressful

3. Can lead to multiple births → risk to babies + mom

4. Unethical → not all embryos created inserted into mom → many embryos destroyed

What are plants sensitive to?

• Light

• Gravity

Phototropism

When plant shoots grow towards light

• Plants response to light

How do plants use the hormone auxin to grow towards light?

1. Light causes auxin to concentrate on the darker side of the shoot tip

2. Auxin spreads down the shoot

3. So cells on the darker side grow faster than cells on the lighter side

4. Causes the shoot to grow towards the light

Where is auxin produced?

Very tip of the shoot and roots

What does auxin trigger in shoots?

Cell growth

Auxin

Hormone that coordinate + control plant growth in response to light + gravity

What do unequal distributions of auxin cause?

Unequal growth rates in plant roots + shoots

Gravitropism

Plant roots grow towards the force of gravity

• Plant’s response to gravity

How does auxin control gravitropism and make plant roots grow towards the force of gravity?

1. Gravity causes auxin to concentrate on the lower side of the root

2. In roots auxin inhibits cell growth

3. So the lower side grows slower than the upper side

4. Causes roots to grow towards the force of gravity

Role of auxin in shoots vs roots

1. Shoots: promotes cell growth

2. Roots: inhibits cell growth

Giberellins

Important in starting seed germination

Ethene

Controls cell division + ripening of fruits

Why is auxin important in shoots?

• Must grow upwards- away from gravity + towards light

• So leaves can absorb sunlight

Why is auxin important in roots?

• Must grow downwards into the soil- away from light + towards gravity

• To anchor the plant, absorb water + minerals from soil particles

Agriculture

Growing food crops

Horticulture

Growing plants for gardens