Lecture 1 Flashcards
What is the function of Glial cells?
Maintains homeostasis nourishment and regulation
Bipolar neuron
1 dendrite and 1 axon
Multipolar neuron
Multiple dendrites and 1 axon
(these are the most common)
what are the types of Glial cells, (the glue of the nervous system)
Macroglia
and
Microglia
Astrocyte is a ___glia and it is
Macroglia
Star shape cells that include neural signalling
Oligodendrocyte and Schwann cells are a type of ___glia and they do what?
Macroglia
Forms myelin sheath
Which cells are the only supporting cells of the PNS
Schwann cells (Form the myelin of the PNS)
Oligodendrocytes form the myelin of the CNS
Action potential is always the same strength: True or false
True
It is all or none, regardless of the stimulus strength
What is the membrane potential of a neuron
-70mV
Extra cellular fluid is ____
Whereas intracellular fluid is ____
at resting potential
Extracellular: Positive
Intracellular: Negative
Cell membrane is more permeable to ____ than sodium
Potassium
Why? More channels open for potassium than sodium
What are the 4 types of ion channels?
Leak
Modality Gated
Ligand Gated
Voltage Gated
The Na - K pump which requires ATP does what?
2 K+ into the cell
3 Na+ out of the cell
True or false: It is harder to stimulate a nerve in a hyperpolarized state vs a depolarized state
True
A stim has to reach the potentia of ____ to produce an action potential
-55mV
An action potential travels in ____ direction
one direction only!
During the rising depolarization phase what happens to the charge?
The charge goes from -70 to +30
During the falling repolarization phase, what happens to the charge?
the charge goes from +30 to -70
What happens to the charge during the hyperpolarization phase
The charge goes from -70 to -90
What channels open during depolarization?
Sodium (Na+) channels open and sodium enters which leads to a more positive charge
What channels open during repolarization
Potassium channels open and potassium exits which leads to a more negative charge since K+ is leaving.
meanwhile sodium channels close
Depolarization only occurs where in salatory conduction?
Nodes of Ranvier
What is continuous conducton?
AP propagates along unmyelinated axon, one by one
What is salatory conduction
action potential spreads quickly throughout myelinated regions
What is the speed of a Nerve AP?
0.5ms to 2ms
What is the resting potential of skeletal and cardiac muscle?
-90mv
How long does a muscle AP last?
1-5ms
(Less duration that cardiac/smooth muscle)
Cardiac and smooth muscle AP lasts how long?
10-300ms longer duration
What is the resting potential of smooth muscle
-20 to -50mv
How much faster is nerve conduction compared to conduction velocity of skeletal muscle?
x18 faster
What function do the microglia play in the nervous system?
Microglia = The Immune system of the CNS
Myelin shealths do what to AP transmission speed?
Increase the speed
More sodium (NA+) is usually present ____ the cell
Outside
The resting membrane potential is established when….
The movement of K+ outside the cell equals the movement of K+ inside the cell
What is a “leaky gate” ion channel
Small amounts of ions constantly diffuse through the membrane
What is a modality-gated ion channel?
*present in sensory neurons only
Opens in reaction to mechanical/chemical/temp stimulus
What is a ligand-gated ion channel?
Opens when neurotransmitter binds to post-synaptic receptors, generating local potentials
What is a voltage-gated ion channel?
Opens in response to electrical charge
More NA and CL is typically found ____ (inside/outside) the cell and more anions and potassium is found _____
outside
Inside
By what 3 mechanisms is the dynamic equillibrium maintained
negative charged anions trapped inside neuron
passive leak of K+ and NA+
Na and K Pump that brings in 2 K+ and expels 3 NA+, powered by ATP
During initial depolarization, small changes in membrane voltage trigger _____
Voltage-gated NA(Sodium) channels
During depolarization, when voltage-gated NA+ channels let sodium in, what happens to the neurons charge
It goes from negative to positive, and an action potential is generated
What channels cause hyperpolarization and why?
Potassium channels. They remain open letting additional K+ out, which leads to the neurons charge going from -70 to -90
This is because K+ channels are slower to respond to AP depolarization
The refractory period of neurons can either be…
Absolute or Relative
In absolute- it will not respond to stimuli until the refractory period is over
In relative, it may respond to a stronger stimuli
What is the benefit of the refractory period of neurons
Prevents backflow of action potentials
What are 3 factors that affect action potential speed?
Diameter of axon- Larger means faster, allows more current to flow
Myelin- leads to less loss of current to surroundings
Temp- warm membranes react faster
What happens at the Nodes of Ranvier?
Saltatory conduction: AP leaps from node to node
Are Peripheral sensory and motor axons myelinated or unmyelinated?
Myelinated
Short axons in gray matter of CNS
Some visceral autonomic axons
Some pain fibers
These are all examples of ______ fibers
Thin unmyelinated fibers
Remember gray matter = nonmylinated
Spatial vs temporal summation
Spatial summation involves simultaneous signals coming from multiple presynaptic neurons being received by a single postsynaptic neuron.
Temporal summation involves a single presynaptic neuron rapid-firing signals to a postsynaptic neuron.
Where is the location of voltage gated Na channels?
Node of Ranvier
