Neurophysiology

• What are neurons considered as in the nervous system?

  Fundamental building blocks
• What do action potentials allow in the body?

  Transmission of nerve impulses
• What is an action potential?

  A rapid, temporary electrical signal
• What is the membrane potential?

  Difference in electrical charge across the membrane
• What is the typical resting membrane potential in neurons?

  Approximately -70 millivolts (mV)
• What happens during hyperpolarisation?

  The inside of the membrane becomes more negative
• What occurs during depolarisation?

  The inside of the cell becomes more positive
• What are the two key physics concepts in neurophysiology?

  Diffusion gradients and electrical gradients
• What is diffusion?

  Random movement of particles from high to low concentration
• What are cations and anions?

  Cations are positive ions; anions are negative ions
• What is the role of sodium (Na+) and potassium (K+) in action potentials?

  Essential for generating action potentials
• What is selective ionic permeability?

  Ability of membranes to allow certain ions through
• What happens when K+ ions diffuse out of the cell?

  Builds up a slight excess of negative charge inside
• What is the equilibrium potential for potassium?

  -90 millivolts (mV)
• What is the equilibrium potential for sodium?

  +60 millivolts (mV)
• What maintains the resting membrane potential?

  The Sodium-Potassium pump
• How long does an action potential last?

  Approximately 2 milliseconds
• What triggers the opening of voltage-gated ion channels?

  Depolarisation of the neuronal membrane
• What is the depolarisation threshold for a neuron?

  -55 millivolts (mV)
• What happens during the rising phase of an action potential?

  More voltage-gated sodium channels open
• What occurs during the falling phase of an action potential?

  K+ channels open, moving towards negative value
• What is the refractory period?

  Time before another action potential can occur
• What are the phases of an action potential?

  1. Depolarisation threshold
  2. Rising phase
  3. Overshoot
  4. Falling phase
  5. Undershoot
  6. Resting state
• How do sodium and potassium concentrations differ inside and outside the neuron?

  • Sodium (Na+): 10 times higher outside (10:1 ratio)
  • Potassium (K+): 40 times higher inside (40:1 ratio)
• What is the role of voltage-gated ion channels in action potentials?

  • Closed at rest
  • Open when membrane depolarises
  • Sodium channels open immediately
  • Potassium channels open after a delay
• How does the Sodium-Potassium pump function?

  • Actively transports Na+ out of the cell
  • Actively transports K+ into the cell
  • Maintains resting membrane potential
• What are the differences between diffusion gradients and electrical gradients?

  • Diffusion gradients: particles move from high to low concentration
  • Electrical gradients: oppositely charged ions attract, like charges repel
• What happens to the membrane potential during an action potential?

  • Rapid depolarisation
  • Rapid repolarisation
  • Hyperpolarisation occurs after repolarisation
• What is the significance of the all-or-none response in neurons?

  • Neuron fires only if depolarisation threshold is reached
  • Ensures consistent action potential generation
• What is dynamic equilibrium in the context of diffusion?

  • Molecules evenly distributed
  • Continuous random movement in all directions
• What is the role of ion channels in neuronal function?

  • Allow selective passage of ions
  • Regulate ion flow during action potentials
• How does the membrane potential change during the phases of an action potential?

  • Depolarisation: moves towards +60 mV
  • Overshoot: approaches Na+ equilibrium
  • Falling phase: moves towards -90 mV
  • Undershoot: hyperpolarised state
• What is the significance of the equilibrium potentials for sodium and potassium?

  • Sodium: +60 mV
  • Potassium: -90 mV
  • Determines membrane potential during rest and action potential