A scientist records the electrical activity of a single myelinated sensory neurone. Under maximum stimulation, the neurone is found to have an absolute refractory period of 2.5 ms and a relative refractory period of 1.5 ms.
What is the maximum theoretical frequency of action potentials that can be transmitted along this neurone, and what is the primary molecular mechanism that ensures the action potential only propagates in one direction along the axon?
400 s−1400\text{ s}^{-1}400 s−1; the sodium voltage-gated ion channels immediately behind the active zone are in an inactivated state.
400 s−1400\text{ s}^{-1}400 s−1; the sodium-potassium pump actively transports three sodium ions out of the axon for every two potassium ions in.
250 s−1250\text{ s}^{-1}250 s−1; the sodium voltage-gated ion channels immediately behind the active zone are in an inactivated state.
250 s−1250\text{ s}^{-1}250 s−1; the potassium voltage-gated ion channels remain open, causing hyperpolarisation.
39 exam-style questions on OCR GCSE Biology 3.1 Coordination and control – the nervous system, covering 3.1.1 Structure of the nervous system, 3.1.2 Coordinated response, 3.1.3 The reflex arc, 3.1.4 Structure of the eye, 3.1.5 Defects of the eye, 3.1.6 Structure and function of the brain, 3.1.7 Difficulties of investigating brain function, and 3.1.8 Limitations in treating nervous system damage. Each one has a worked solution and a mark scheme showing where the marks go.