Neurophysiology

• What is a recommended textbook for physiology?

  Physiology at a Glance
• What makes a membrane excitable?

  Ion channels and membrane potential
• What is the basis of the membrane potential?

  Distribution of ions across the membrane
• Why are ion channels important for membrane excitability?

  They allow ions to flow across membranes

  
• How can ionic equilibria be applied to the membrane potential?

  By predicting ion flow and membrane charge
• What do the terms depolarisation and repolarisation refer to?

  Changes in membrane potential
• What is the membrane resting potential?

  The stable voltage across the membrane at rest
• How is the Nernst equation used in physiology?

  To calculate equilibrium potentials for ions

  
• What is cell excitability based on?

  Bioelectricity and ion channel activity
• What are the key properties of ion channels?

  Selective, modulated, and can be gated

  
• How do ion channels transport ions?

  Through passive transport involving ionic gradients

  
• What is the role of ionic gradients in excitability?

  They create the potential for ion flow
• What is the typical concentration of Na+ inside and outside the cell?

  20 mM inside, 145 mM outside

  
• What is the typical concentration of K+ inside and outside the cell?

  150 mM inside, 4 mM outside

  
• What is the typical concentration of Ca++ inside and outside the cell?

  0.0001 mM inside, 2.5 mM outside

  
• What happens when an ion channel opens?

  Ions can flow across the membrane

  
• What does increasing the 'open probability' of channels do?

  Increases ion flow across the membrane
• What is the equilibrium (reversal) potential?

  The point where ion flow stops
• What is the equilibrium potential for K+ under physiological conditions?

  -95 mV
• What is the equilibrium potential for Na+ under physiological conditions?

  +61 mV
• What is the equilibrium potential for Ca++ under physiological conditions?

  +137 mV
• What is the equilibrium potential for Cl- under physiological conditions?

  -65 mV
• What does the Nernst equation help predict?

  The equilibrium potential for specific ions

  
• How is the Nernst equation simplified for monovalent positive ions?

  $EmV =$$61.5 \times \log_{10} \left(\frac{[ion]_{out}}{[ion]_{in}}\right)$
• How do you calculate EmV for K+ under normal physiological conditions?

  Using the simplified Nernst equation
• What happens to EmV for K+ in hyperkalaemia?

  It increases due to higher K+ concentration
• What does a bolus of KCl solution IV imply for a patient?

  It can disrupt the membrane potential
• What is the Goldman (GHK) equation used for?

  To predict membrane potential

  
• What varies in the Goldman equation?


  Permeability for each ion
• What determines if a channel is open or not?

  The gating mechanism of the channel
• What are the types of gated channels?

  Ligand-gated and voltage-gated channels
• What underlies membrane depolarisation or repolarisation?

  The opening and closing of ion channels
• What does ionic current flow underlie?

  The action potential in neurons
• What states of the membrane should be described during action potential?

  Depolarisation, repolarisation, and resting

  
• Why is the resting potential for cells negative?

  Due to K+ exit during repolarisation
• What keeps the membrane potential closer to K+ equilibrium?

  K+ being the main permeant ion at rest
• What maintains the ionic gradient at rest?

  The Na+/K+ ATPase pump
• What is the effect of ATP levels on the Na+/K+ ATPase pump?

  Low ATP levels can impair its function
• What does cell membrane excitability depend on?

  Ionic gradients and ion channel activity

  
• What do changes in membrane potential indicate?

  Flow of ions and action potential generation