The Nervous System and Reflexes
Your nervous system is basically your body's electrical wiring. The central nervous system (brain and spinal cord) coordinates everything, while neurons carry electrical impulses like biological cables. Sensory neurons bring information from receptors to your CNS, whilst motor neurons carry commands to muscles and glands.
Reflex actions are your body's emergency responses that bypass your brain for speed. When you touch something hot, the signal goes: receptor → sensory neuron → spinal cord → motor neuron → muscle. This happens automatically before you even realise what's going on!
Synapses are tiny gaps between neurons where electrical impulses trigger the release of neurotransmitters - chemical messengers that jump across to continue the signal.
Remember: Reflexes are automatic, rapid responses that don't involve conscious thought - they're survival mechanisms!
Hormones and Homeostasis
Hormones are chemical messengers produced by glands and transported in your blood to target organs. The pituitary gland is like the master controller, whilst other glands like the thyroid (controls metabolism) and pancreas (manages blood sugar) have specific jobs.
Homeostasis keeps your internal environment stable through negative feedback loops. When blood glucose gets too high, your pancreas releases insulin to help cells absorb glucose and convert excess into glycogen for storage. When levels drop too low, glucagon does the opposite - converting stored glycogen back into glucose.
Adrenaline from your adrenal glands prepares you for 'fight or flight' by increasing heart rate and breathing, plus releasing glucose for quick energy. Meanwhile, thyroxine from your thyroid regulates your metabolic rate and influences growth and development.