neurophysiology

• membrane potential is the difference in electrical charge across the plasma membrane
• leak channels are always open
• Resting membrane potential is when there is more K+ inside the cell and more Na+ outside the cell
• the potential to do work comes from signals
• resting membrane potential is -70mV and is maintained by the sodium-potassium pump
• Depolarization is when the inside of membrane becomes less negative (the graph goes upward).
• Hyperpolarization is when the inside of the membrane becomes even more negative than resting membrane potential.
• Repolarization is the return to resting potential from depolarization. This is when the inside of membrane becomes more negative (graph goes back downward)
• graded potentials eventually decay over time
• refractory periods are when the action potentials are not able to be generated as the ion channels remain closed
• synaptic cleft is the gap between one neuron and another neuron
• in neural synapses a electrical signal has to be changed to a chemical signal
• voltage gated Calcium channels open, allowing for neurotransmitters to be released
• Calcium entering the cell triggers exocytosis of synaptic vesicle contents
• neurotransmitter binding initiates a response in the post synaptic neuron (cell)
• the presynaptic membrane depolarizes due to calcium influx
• neurotransmitters follow principles of protein-based (lipophobic)

  ligand action. This includes triggering the second messenger cascade and triggering chemically gated ion channels
• GABA is the primary inhibitory neurotransmitter in the brain.
• Glutamate is the primary excitatory neurotransmitter in the brain.
• neurotransmitters can be either excitatory or inhibitory depending on the receptor
• neurotransmitters are influenced by drugs and diseases
• The equilibrium potential created by K+ is -90 mV
• rapid Na+ entry depolarizes the cell
• continuous conduction is when a wave of electrical current passes down the axon. The action potential follows in the direction of the current going from dendrites to cell body length
• the spaces in between the myelin sheath on the axon are called nodes of ranvier. Here there are Na+ channels here (voltage gated)
• Refractory periods are where ion channels remain closed and no action potential is generated. They are also voltage gated
• during the absolute refractory period no stimulus can trigger another action potential (the action potential is greater than Na+ and K+ permeability)
• refractory period is the time between action potentials, in which it is short in both the the neuron and heart
• The post synaptic cite is located at the dendrite
• excitatory postsynaptic potentials (EPSP) depolarize the membrane while inhibitory (IPSP) ones hyperpolarize it.
• EPSP's open Na+ channels and IPSP's open Cl- channels
• Temporal summation is when two subthreshold potentials are added together to produce a larger threshold that can initiate a action potential
• Inhibition can occur when one inhibitory neuron fires while two excitatory neurons fire. There is either 1 action potential or 0 action potentials
• Things like our fingers have low convergence while the leg or thigh may have high convergence
• The axon terminal has voltage gated Ca+ channels. When the ion enters the cell it triggers neurotransmitter release (through exocytosis). Ca+ levels are low in the cell and high outside the cell
• Neurotransmitters bind to receptors on the post synaptic membrane which causes an EPSP or IPSP
• neurotransmitters follow principles of protein based (lipophobic) ligand action. This allows them to trigger chemically gated ion channels and can trigger the secondary messenger cascade.
• Acetylcholine (ACh) is a neurotransmitter used by the brain and motor neurons that does not get reused. It is degraded by acetylcholinesterase (AChE)
• Acetylcholine has are 2 types of receptors: nicotinic which are ion channels Na+ and Ca+ (excitatory) and muscarinic which are coupled with G proteins (inhibitory).
• locations of ACh are neuromuscular junctions, the CNS, and the ANS