Flashcards in Chapter 7+8 Deck (33):
Two types of electrical signals in neurons
Graded potentials (short-distance)
Action potentials (short- and long distance)
What is resting membrane potential?
Neurons exhibit an electrical voltage difference across the membrane
4 types of ion channels
Mechanically gated Channel
Explain leak gate channels
Always open and are responsible for the resting membrane potential
Explain volatage-gated channels.
They open and close in response to changes in the membrane potential
Explain Ligand gated channels
Open and close in response to the binding of a chemical messenger to a specific receptor in plasma membrane
What is a graded potential: two states
Small deviations from the resting state.
Hyperpolarized (inside more negative)
Depolarized (inside less negative)
Where does graded potential mainly occur?
Occurs mainly in the dendrites of sensory neurons and cell body of a neuron
What does the sign of the membrane potential always refer to?
Potential inside the cell relative to the potential outside.
Resting membrane potential negative or positive?
What is hyperpolerization ?
membrane potential becomes more negative
What is depolarization?
less negative membrane or to a positive potential.
What is repolarization?
When the membrane returns to resting membrane potential following a depolarization
First phase of action potential? Caused by what?
Depolarization. Caused by rapid inrease in permeability to sodium
What is the second phase of an action potential? What increases
Repolarization. Potassium permeability increases.
Electrical resting state of -70 is due to what?
Unequal distribution of ions across cell membrane
Relative permeability to Na+ and K+
What is the refractory period?
Period of time during which no action potential can be generated( right after)
What is the absolute refractory period?
No act. pot. can propagate, Bigger diameter axons mean longer time of this period. Happens during depolarization phase plus most of the re polarization phase.
What is the relative refractory period?
Immediately after absolute part, possible for second action potential if stimulus is much stronger. Due to increased permeability of potassium channels.
How does propagation of nerve impulses move
From dendrites to axon terminal
What is the difference between mylinated axon and unmylinated
Unmyelinated has slow process called continuous conduction, myelinated is fast process called salvatory conduction
Steps of continuous conduction
Starts when the threshold is reached (–55mV)
Na+ is moving into cytosol and in the ECF (current)
Local current spreads in all directions, passes the axon hillock and reaches initial segment
Action Potential propagates along the axon
Three components of saltatory condution
Impulse leaps from node to node (Ranvier node)
Schwann Cell and Ranvier node allow a faster transmission along the axon
Allows to open a smaller number of channels
What effect does axon diameter have on conduction speed?
Smaller diameter= faster conduction
Two types of signal transmissions at synapses
Electrical synapse:Action potentials conduct directly between adjacent cells through gap junctions
Faster communication and better synchronization
Structured with pre- and post-synaptic neurons
Impulse goes until end bulb
Depolarization opens voltage-gated Ca+ channels
Triggers vesicle movement through the layer (neurotransmitters)
Neurotransmitters diffuse through the cleft
Binding of Neurotransmitters with receptors triggering ion flow across post-synaptic layer
Ion flow triggers the post-synaptic potential
If threshold is reached than back to the step one
Removal of neurotransmitter occurs how?
Diffusion (pass through synapse cleft)
Enzymatic degradation (specific enzymes break down neurotransmitters)
Uptake by cells (actively transported back into the neuron)
What is spatial and temporal summation
Spatial summation results from several pre-synaptic end bulbs. Generally comes from two or more neurons
Temporal summation results of rapid successions of impulse from one neuron
Acetylecholine released by what
PNS and CNS (excitatory and inhibitory effects)
Ex of amino acid and released from where
Glutamate, asparate (release by CNS – excitatory effect)
Catecholamines, serotonin (involve in skeletal muscle tone, lymbic system, sensory aspects
When ATP breaks down its residue (ADP, AMP) serves as neurotransmitters in CNS and PNS.