Homeostasis and Response

What is homeostasis?

Regulation of internal conditions to maintain optimal function in response to internal and external changes.

Why is homeostasis important?

It maintains optimal conditions for enzyme action and all cell functions.

Which conditions does homeostasis control in the human body?

Blood glucose concentration, body temperature, and water levels.

What are the three parts of a control system?

Receptors, coordination centres (brain/spinal cord/pancreas), and effectors (muscles/glands).

What is the function of the nervous system?

To detect stimuli and coordinate responses so the body can react to its environment.

What is the CNS made of?

The brain and spinal cord.

How is information passed in the nervous system?

As electrical impulses along neurones.

What is the correct order of response in the nervous system?

Stimulus → Receptor → Coordinator → Effector → Response

What is a reflex action?

A rapid, automatic response that bypasses the conscious brain.

Why are reflexes important?

They protect the body from harm by reacting quickly to danger.

What are the three types of neurones in a reflex arc?

Sensory neurone, relay neurone, and motor neurone.

What is the role of a sensory neurone?

Carries electrical impulses from receptors to the CNS.

What is the role of a relay neurone?

Transfers signals within the CNS (usually spinal cord).

What is the role of a motor neurone?

Carries impulses from the CNS to effectors.

What practical investigates reaction time?

Required Practical 6 – Investigating the effect of a factor on human reaction time.

What is the endocrine system?

A system of glands that secrete hormones directly into the bloodstream.

What is a hormone?

A chemical messenger carried in the blood to target organs.

How do hormones compare to nerves?

Slower-acting but longer-lasting.

What is the ‘master gland’?

The pituitary gland – it controls other glands.

Name six endocrine glands.

Pituitary, thyroid, pancreas, adrenal gland, ovary, testes.

What monitors blood glucose levels?

The pancreas.

What happens when blood glucose is too high?

The pancreas releases insulin, which moves glucose from the blood into cells or stores it as glycogen.

What happens when blood glucose is too low?

The pancreas releases glucagon, which converts glycogen back into glucose.

What type of feedback controls blood sugar?

Negative feedback.

What is Type 1 diabetes?

A condition where the pancreas doesn't produce enough insulin.

How is Type 1 diabetes treated?

With insulin injections.

What is Type 2 diabetes?

A condition where cells stop responding to insulin.

How is Type 2 diabetes treated?

With a controlled diet and exercise.

What hormone triggers female puberty and egg release?

Oestrogen.

What hormone triggers male puberty and sperm production?

Testosterone.

What does FSH do?

Causes an egg to mature in the ovary.

What does LH do?

Stimulates the release of the egg (ovulation).

What do oestrogen and progesterone do in the cycle?

Maintain the uterus lining.

What hormone methods of contraception are there?

Pill (inhibits FSH), injection, implant, patch (release progesterone).

What non-hormonal methods of contraception exist?

Condoms, diaphragms, IUDs, spermicides, abstinence, sterilisation.

How do fertility drugs work?

They contain FSH and LH to stimulate egg release.

What is IVF?

In vitro fertilisation – eggs fertilised in lab then embryos implanted into uterus.

What are the problems with IVF?

Emotional/physical stress, expensive, low success rate, multiple births.

What is adrenaline?

A hormone released in stress/fear that increases heart rate and boosts oxygen/glucose delivery.

What is thyroxine?

A hormone from the thyroid that controls metabolic rate.

How is thyroxine regulated?

By negative feedback.