| Describe the structure of a neuron | Dendrites: receive incoming chemical signals and convert them into graded potentials Cell body (soma): integrates graded potentials coming from dendrites Axon terminals: release chemical messengers that simultaneously influence numerous other cells through synapses. Axon hillock: area of high expression of NaV channels and action potential initiation Axon: carry electrical signals such as action potentials from the cell body to the end of the axon. |
| Explain the concept of threshold depolarization and self-regenerative action potentials | Threshold depolorisation: the state at which a neuron will fire an action potential (approximately -55mV) Self-regenerative action potentials: action potentials are regenerate at the unmyelinated nodes of Ranvier due to the triggering of graded depolorisation which opens Na+ voltage dependent channels, resulting in more Na+ entering the cell. |
| Explain the roles of glial cells, myelin sheath and nodes of Ranvier | Glial cells maintain homeostasis and form myelin in the CNS and also protect neurons, however they DO NOT carry nerve impulses (action potentials) Myelin sheath are fatty tissue sleeves that protect nerve cells and increases the speed of signals transmitted between neurons (action potentials). Nodes of Ranvier facilitate the rapid conduction of nerve impulses |
| Define Saltatory conduction | Depolarisation propagates passively from one node of Ranvier to the next, where the action potential is regenerated The action potential amplitude is maintained over long distances by repeating boosting the signal to full height using the energy in the Na+ gradient, at regularly spaced nodes. |
| Define types of refractory periods | Absolute refractory period: a second stimulus (no matter how strong) will not excite the neuron Relative refractory period: a stronger than normal stimulus is needed to elicit neuronal excitation |
| Explain the significance of Na+ channel inactivation in an axon | Because Voltage-gated sodium channels play an important role in action potentials, it's crucial for these channels to assume a closed-inactivated state as it results in the refractory period and is critical for propagation of action potentials down the axon. |
