Biology Topic 2 Unit 1

Unit 2 Topic 1

What is homeostasis

an organism keeps its internal conditions stable, even when the outside environment is changing

what happens when i touch a hot object

When you touch a hot object:

1. Stimulus → The heat from the hot object is the stimulus.

2. Receptor → Heat/pain receptors in your skin detect the stimulus.

3. Sensory neuron → Carries the nerve impulse from the receptor to the central nervous system (CNS).

4. Central nervous system → The brain and spinal cord process the information and coordinate a response.

5. Motor neuron → Carries a nerve impulse from the CNS to the muscles.

6. Effector → The muscles in your arm/hand act as the effector.

7. Response → Your muscles contract, causing you to quickly pull your hand away from the hot object.

types of receptors

• Thermoreceptors

  • Detect changes in temperature.

  • Found mainly in the skin.

  • Detect whether something is hot or cold.

  • Example: Feeling the heat when you touch a hot object.

• Mechanoreceptors

  • Detect physical forces such as touch, pressure, vibration, stretching and movement.

  • Found in the skin, muscles, joints and inner ear.

  • Example: Feeling pressure when someone touches your arm.

• Photoreceptors

  • Detect light.

  • Found in the retina of the eye.

  • There are two main types:

    • Rods – help you see in low light and detect movement.

    • Cones – detect colour and allow detailed vision.

• Chemoreceptors

  • Detect chemicals.

  • Found in places such as the nose, tongue and blood vessels.

  • Help detect smells, tastes, oxygen levels and carbon dioxide levels.

  • Example: Detecting the smell of food.

• Nociceptors (pain receptors)

  • Detect potential or actual tissue damage.

  • Found throughout the skin and many internal tissues.

  • Respond to things such as extreme heat, extreme cold, pressure or chemicals.

  • Example: Feeling pain when you touch a very hot surface.

what are effectors

Parts of the body which carry out responseswhen they receive signals from the nervous system or hormones

The two main types of effectors are:

• Muscles – contract or relax to produce movement.

  • Example: When you touch something hot, your arm muscles contract, pulling your hand away.

• Glands – release substances such as hormones, enzymes or sweat.

  • Example: Sweat glands produce sweat when your body gets too hot.

3 types of glands

• Pituitary gland = Controls many other endocrine glands; growth and reproduction

• Thyroid gland = regulates metabolism and energy use

• Pancreas = Produces insulin and glucagon to regulate blood glucose

• Thyroid gland = regulates metabolism and energy use

• Testes = produces testosterone

3 types of muscle

• Skeletal Muscle

• Smooth Muscle

• Cardiac Muscle