Neurones and Synapses 0.0 / 5 ? BiologyCellular processes and structureA2/A-levelCCEA Created by: Football03Created on: 30-03-22 09:55 What are the 3types of neurones? -Sensory -Motor -Connector 1 of 20 What is the function of dendrites? Transmit impulses towards the cell body 2 of 20 What does the negative sign mean? The inside of the cell is negatively charged with respect to the extracellular fluid along the membrane (resting potential ) 3 of 20 When there is a resting potential, what is the neurone said to be? Polarised 4 of 20 What is the potential difference due to? There being an excess of positively charged ions outside the membrane compared to inside 5 of 20 What is the potential difference at rest ? -70mV 6 of 20 What happened when an impulse is transmitted along a neurone ? Depolarisation;inside of the neurone membrane becomes positively charged and outside is now negative 7 of 20 Why does depolarisation occur? The cell surface membrane becomes permeable to Na+ ions (down the concentration gradient) 8 of 20 What is the potential difference at now? (THRESHOLD LEVEL) -55mV 9 of 20 What happens during depolarisation? -More gated ion channels open -Rapid increase in rate of diffusion into the membrane 10 of 20 What is the 'all or nothing rule'? -If threshold is not achieved -Depolarisation not occur -Membrane returns to rest 11 of 20 What happens if threshold level is reached? -Positive ions flood in -Inside membrane is positive -Potential difference of 40mV 12 of 20 What happens at the 'peak' of the action potential? -The recovery phase -Positive ions diffuse&pumped out of neurone 13 of 20 What is the reversal of potential difference known as? Action potential 14 of 20 The refractory period ensures...? No further impulse can occurs gated channels are closed&resting potential not fully restored 15 of 20 What is the slight 'overshoot' stage known as and what occurs here? Hyperpolarisation -the inside of the axon membrane becomes slightly more negative than the normal resting potential 16 of 20 What is the time delay before a second action potential can be transmitted called? Refractory period 17 of 20 Why is the refractory period important? -propagated in a forward direction -sets an upper limit for the frequency of impulses along a neurone -limits the number of action potentials generated in a given time 18 of 20 State 2 features about nerve impulses? -Threshold stimulus -All or nothing response 19 of 20 What happens if the stimulus is below the threshold value? No action potential will be generated 20 of 20
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