CB7 - Animal Coordination, control and homeostasis

Where are hormones produced?

In the endocrine glands.

Role of hormones in body

Enables you to respond to changes that occur in your body.

How are hormones transported?

Hormones are transported around the body through the blood.

Common hormones and targets of pituitary gland hormones

ACTH → Adrenal Cortex

FSH + LH → Ovaries/Testes

Growth Hormone → All tissues

Common hormones from the thyroid gland/adrenal gland+ target organs

Thyroxine → most tissues

Adrenaline → heart, blood cells and liver

Common hormones from pancreas + target organs

Insulin → Muscle and liver

Glucagon → liver

Common hormones from testes/ovaries + target organs

Oestrogen → ovaries, uterus and pituitary gland

Progesterone → uterus

Testosterone → testes, pituitary gland

Importance of hormones

Responsible for reacting to changes in your body, allowing you to maintain the homeostasis required for your body to function correctly.

Effect of adrenaline

Adrenaline acts on heart muscle, causing it to contract more rapidly and strongly to increase heart rate and blood pressure.

It acts on blood vessels leading to the muscles, widening them, increasing blood flow to the muscle. Blood vessels leading to other organs narrow to reduce blood flow to these.

Acts on the liver so that cells change glycogen into glucose to increase blood sugar concentration.

How does adrenaline prepare the body for a fight or flight response?

Increasing heart rate and blood flow to the muscles allows more oxygen and glucose to be supplied for aerobic respiration and more energy to be released. increasing blood sugar levels also provides more glucose for aerobic respiration.

Metabolic rate

The rate at which energy stored in food is transferred by all the reactions in the body to keep you alive.

Effect of thyroxine on metabolic rate

Causes heart cells to contract more rapidly and strongly and increases the rate at which carbohydrates and proteins are broken down inside cells (increase metabolic rate).

How does a negative feedback system work?

Increasing the amount of a substance results in changes that bring about a decrease in the amount of that substance being released into the blood and vice-versa.

How does negative feedback control the production of thyroxine?

Having lower tower than normal levels of thyroxine in the blood stimulates the hypothalamus to release TRH, thus stimulate the pituitary to release TSH which in turn triggers the thyroid gland to release thyroxine and vice versa.

Why are negative feedback mechanisms important in living organisms?

They stop the body from overproducing a substance. When levels return to normal, the negative feedback loop stops production of the substance, thus helps to conserve energy and resources for other processes, as well as stopping diseases that could be cause by incorrect amounts of the hormone.

What happens during the menstrual cycle?

A cycle of changes in the female reproductive system that happen over a period of 28 days. Days 1-5: Uterus lining breaks down and is lost with an unfertilised egg cell. Day 11: Uterus lining thickens again. Days 13-15: Ovulation occurs, releasing an egg. Days 16-28: Uterus lining continues to thicken and an egg cell travels along the oviduct to the uterus.

Function of oestrogen in the menstrual cycle

Repairing and thickening the uterus lining

Function of progesterone in the menstrual cycle

Maintain thickness of the uterus lining.

How are barrier methods used as contraception?

Condoms - placed over erect penis, prevents sperm entering the vagina so cannot fertilise egg.

Diaphragm or cap - placed over cervix to prevent sperm entering uterus and fertilising egg.

How can hormones be used as contraception?

Hormone pill or implant - release hormones to prevent ovulation and thickens mucus at the cervix making it difficult for sperm cells to pass through.

Success rate of male condom, diaphragm or cap, hormone/implant

Male condom - 98% success rate

Diaphragm or cap - 92-96% success rate

Hormone/implant - >99% success rate (but doesn’t prevent STIs)

How do changes in hormones effect the uterus wall, ovulation, and menstruation?

Increasing oestrogen helps thicken the uterus wall and increasing progesterone helps maintain the thickness. When the levels of these hormones fall menstruation is triggered causing the shedding of the wall.

How do oestrogen, progesterone, FSH and LH interact in the menstrual cycle?

FSH and LH are released from the pituitary gland when there are high levels of oestrogen. When the amounts of progesterone increase it inhibits the production it inhibits the production of FSH and LH.

Describe examples of Assisted Reproductive Technology

Clomifene therapy - A drug which increases FSH and LH in the blood to trigger release of an egg.

IVF - Overcomes problems like blocked oviducts or lack of sperm production. This involves external fertilisation of the egg before it is implanted into the woman’s uterus.

How is clomifene is used to stimulate ovulation?

Increases concentration of FSH and LH in the blood. FSH stimulates growth and maturation of the egg follicle and LH helps trigger ovulation.

How are hormones used in IVF treatment ?

Egg cell maturation and release is stimulated with FSH and LH. This egg can then be removed and fertilised in the lab before being re-implanted.

Homeostasis

Controlling the internal environment of the body at stable levels.

Why is it important that the internal environment is constant?

Maintains optimal conditions for enzyme action throughout the body, as well as all cell functions. It is the maintenance of a constant internal environment despite changes in internal an external conditions.

Role of insulin

As blood glucose rises, it triggers cells in the pancreas to make insulin. Insulin causes cells in the muscles and liver to absorb glucose and store it as glycogen, lowering the blood concentration.

Role of glucagon

Causes liver cells to convert glycogen back to glucose which is released into the blood, made in pancreas.

How are type 1 and type 2 diabetes caused?

The pancreatic cells that normally produce insulin do not. This is due to insulin producing cells being destroyed by the immune system. This means that blood glucose levels are higher than normal.

Either insulin producing cells do not produce enough insulin, or the target organs (liver and muscles) do not respond to it.

How can type 1 and type 2 diabetes be controlled?

Insulin injections to the fat layer below skin can bee used to help lower blood glucose levels.

Controlled diet (low sugar) and exercise. Severe cases require medication that increases the response to insulin or reduces the amount of glucose secreted from the liver.

Correlation between body mass and type 2 diabetes

As the number of people who have type 2 diabetes has increased, the average body mass has also increased.

How is waist:hip ratio connected to body mass?

As people increase in mass, they tend to develop more fat on their waist compared to their hips. This indicates a poorer diet and lower exercise so as the waist to hip ratio increases so does the risk of having type 2 diabetes.

Correlation between body mass and type 2 diabetes

In men, being overweight does not increase the chance of you having type two diabetes (percentage of males with it doesn’t increase). However, being obese does. In women increasing body mass always correlates to an increased chance of having type two diabetes.

Thermoregulatuon

Control of body temperature in order to maintain an internal temperature of 37C.

Importance of thermoregulation in enzyme activity

Enzymes in the body have an optimum temperature of 37C. If temperatures increase or decrease from this then enzymes will work at a slower rate. If the temperatures get too high, enzymes will denature, changing the shoe of their active site resulting in them no longer functioning.

Role of skin in thermoregulation

Contraction in erector cells in the skin dermis cause has to stand upright and trap air next to the skin when cold. Blood flow to the surface of the skin is also reduced to stop heat loss when cold. When too hot sweat forms on top of the skin and evaporates helping to cool the skin.

Role of hypothalamus in thermoregulation

The hypothalamus receives signals from temperature receptors in the body. If it detects blood or brain temperature changes it will send signals to different areas of the body to bring about changes that will help return the body temperature to normal.

Role of muscles in raising low body temperature

Muscles contract and relax rapidly to cause shivering, some of the energy released in respiration during shivering helps warm the body up.

Role of changing blood vessel diameter in thermoregulation

When it is cold nerve impulses sent to the blood vessels cause them to narrow, reducing blood flow to the surface of the skin. When it is hot the blood vessels widen bringing warm blood to the surface of the skin causing it to transfer energy to the surroundings.