Neural Control and Coordination

The neural system provides rapid, point-to-point coordination among organs, working together with the endocrine system to integrate body functions. Hydra has a simple network of neurons, while insects have a brain and ganglia. The human neural system is divided into the central neural system (CNS), made of the brain and spinal cord, and the peripheral neural system (PNS), made of the nerves associated with the CNS. The PNS has a somatic division and an autonomic division, which is further divided into sympathetic and parasympathetic systems. This chapter describes the neuron with its cell body, dendrites and axon, the types of neurons (multipolar, bipolar and unipolar), and myelinated and non-myelinated fibres. You will learn how a resting potential of about -70 mV is maintained by the sodium-potassium pump, how a nerve impulse is generated by depolarisation and conducted along the axon, and how it crosses electrical and chemical synapses using neurotransmitters. Finally, you will study the human brain: its meninges, forebrain (cerebrum, thalamus and hypothalamus), midbrain and hindbrain (pons, cerebellum and medulla).

Detailed Worksheet: Neural Control and Coordination Section A - Definitions (10 marks) 1. What is a neuron? Name its three main parts. (2 marks) 2. Distinguish between myelinated and non-myelinated nerve fibres. (2 marks) 3. What is the resting potential? What is its approximate value? (2 marks) 4. What is a synapse? Name its two types. (2 marks) 5. What is the corpus callosum? (2 marks) Section B - Calculations and Applications (15 marks) 6. A myelinated nerve fibre conducts impulses at 100 m/s and a non-myelinated fibre at 2 m/s. Calculate the time taken by an impulse to travel 1 m along each fibre in milliseconds. Explain why the myelinated fibre is faster. (3 marks) 7. The sodium-potassium pump moves 3 sodium ions out and 2 potassium ions in for every ATP used. If a neuron's pump uses 1,000 ATP molecules in a second, calculate the number of sodium and potassium ions moved. Why does this make the inside of the axon negative? (3 marks) 8. The membrane potential of an axon changes from -70 mV at rest to +30 mV at the peak of the action potential. Calculate the total change in potential. Which ions cause depolarisation and repolarisation? (3 marks) 9. A neural pathway includes 0.9 m of nerve fibre with a conduction speed of 90 m/s, and 2 synapses each causing a delay of 0.5 ms. Calculate the total time for the signal to pass. (3 marks) 10. Classify the following as part of the forebrain, midbrain or hindbrain: thalamus, corpora quadrigemina, pons, cerebellum, hypothalamus, medulla. State one function of each. (3 marks) Section C - Diagrams (10 marks) 11. Draw a labelled diagram of the structure of a myelinated neuron. (4 marks) 12. Draw a labelled diagram of the sagittal section of the human brain. (3 marks) 13. Draw a labelled diagram of a chemical synapse. (3 marks) Section D - Analysis and Higher-order Thinking (15 marks) 14. Explain the generation and conduction of a nerve impulse along an axon. How do sodium and potassium ions bring about depolarisation and repolarisation? (5 marks) 15. Explain how impulses are transmitted across a chemical synapse. Why is transmission across a synapse one-way, and how does it differ from an electrical synapse? (5 marks) 16. Describe the functions of the major parts of the human brain. Why is the hypothalamus important for both neural and endocrine control? (5 marks) Instructions: Time allowed 2 hours. Attempt all sections. Draw diagrams neatly with labels. Show calculations with units.