Key facts & rules

• Nervous system: brain + spinal cord (CNS) + peripheral nerves.
• Reflex arc: receptor → sensory neurone → relay neurone (spinal cord) → motor neurone → effector.
• Synapse: gap between neurones — neurotransmitters carry the signal across.
• Endocrine system: glands secrete hormones into blood — slower but longer-lasting than nerves.
• Insulin: secreted by pancreas → lowers blood glucose (promotes glycogen storage).
• Glucagon: secreted by pancreas → raises blood glucose (promotes glycogen breakdown).
• Adrenalin: 'fight or flight' hormone — increases heart rate, releases glucose.
• ADH: produced by pituitary → increases water reabsorption in kidneys.
• Auxin: plant hormone; accumulates on shaded side → cells elongate → shoot bends towards light (phototropism).