Coordinating Body Responses

The nervous system plays a crucial role in coordinating the body's responses to stimuli. This process involves several key components:

1. Stimulus: A change in the environment detected by receptors.
2. Receptor: Converts the signal into electrical impulses.
3. Sensory neurone: Transmits impulses to the central nervous system.
4. Central nervous system: Processes information (spinal cord or brain).
5. Motor neurone: Carries signals to the effector.
6. Effector: Produces the response (muscle or gland).

Vocabulary: A synapse is a junction between two neurons across which electrical impulses must pass.

Highlight: Reflexes are automatic responses that help avoid danger or harm, occurring rapidly and without thought.

Example: The reflex arc bypasses the brain to produce a quicker response, keeping you safe in potentially dangerous situations.

The Endocrine System and Hormones

Hormones are chemical messengers produced by endocrine glands and transported in the blood to target organs. They can be fast-acting (e.g., adrenaline) or slow-acting (e.g., sex hormones).

Key endocrine glands and their functions:

1. Adrenal gland: Produces adrenaline, which prepares the body for "fight or flight" responses.
2. Ovaries: Produce estrogen and progesterone, regulating the menstrual cycle and female reproductive functions.
3. Pancreas: Produces insulin to control blood glucose levels.
4. Pituitary gland: Produces various hormones, including anti-diuretic hormone (ADH) and reproductive hormones.
5. Thyroid gland: Produces thyroxine, which controls metabolic rate.
6. Testes: Produce testosterone, regulating male reproductive functions.

Example: The pancreas produces insulin, which targets the liver to control blood glucose levels.

Highlight: Hormones are transported in the blood to reach their target organs and bring about specific effects.