CCEA GCSE Biology 1.6 Nervous System and Hormones Exam Questions

About CCEA GCSE Biology 1.6 Nervous System and Hormones

Nervous System and Hormones is one of the largest topics in CCEA GCSE Biology Unit 1. It compares fast, short-lived nervous control with slower, longer-lasting hormonal control. You need the structure of the eye and how it responds to light and distance, the pathway of a reflex arc and how synapses work. The topic then covers homeostasis, including blood glucose control and diabetes, the removal of waste and the control of water balance by the kidneys. Finally it includes how plants respond to light using auxin. Examiners favour reflex arc sequences, explanations of the pupil reflex and accommodation, and comparisons of type 1 and type 2 diabetes.

What you need to know

• Nervous versus hormonal Nerves carry electrical impulses that are very fast, short-lived and targeted. Hormones are chemicals released by glands into the blood; they act more slowly, last longer and can affect several target organs.
• The eye The cornea and lens focus light on the retina, where receptors detect light. In bright light the iris circular muscles contract and the pupil gets smaller. To focus on near objects the ciliary muscles contract, the suspensory ligaments slacken and the lens becomes fatter.
• Reflex arc Stimulus → receptor → sensory neurone → relay neurone (in the spinal cord) → motor neurone → effector (muscle or gland) → response. Reflexes are rapid and automatic, which protects the body.
• Synapses A synapse is a small gap between neurones. When an impulse arrives, a chemical neurotransmitter is released, diffuses across the gap and binds to receptors on the next neurone, starting a new impulse.
• Blood glucose and diabetes Insulin from the pancreas lowers blood glucose by causing the liver and muscles to take in glucose and store it as glycogen. Type 1 diabetes: the pancreas produces little or no insulin; treated with insulin injections and diet. Type 2: the body stops responding properly to insulin; linked to obesity and treated with diet, exercise and sometimes medication.
• Excretion and osmoregulation The kidneys filter the blood, reabsorb useful substances such as glucose and the water the body needs, and remove urea, excess water and salts as urine. Water balance is controlled by the hormone ADH; when the body is short of water more ADH is released and more water is reabsorbed, giving small volumes of concentrated urine.
• Plant hormones Auxin causes phototropism: light causes auxin to collect on the shaded side of a shoot, cells there elongate more and the shoot bends towards the light. Plant hormones are used commercially as rooting powders and selective weedkillers.

Common mistakes in 1.6 Nervous System and Hormones

• Saying that the lens alone focuses light. The cornea does most of the bending; the lens adjusts focus.
• Describing the impulse jumping across the synapse. A chemical transmitter diffuses across the gap.
• Writing that the brain coordinates a reflex. The relay neurone is in the spinal cord, and the response happens without conscious thought.
• Claiming insulin converts glucose to glycogen itself. Insulin causes liver and muscle cells to take up glucose and convert it to glycogen.
• Stating that auxin is destroyed by light or that cells on the lit side grow more. Auxin moves to the shaded side, where cells elongate more.

Try three 1.6 Nervous System and Hormones exam-style questions