Unit 2: Neurophysiology Flashcards
What types of cells make up the nervous system?
neurons
[the functional cell of the NS]
Define “nerve impulse” (describe the different forms of “nerve impulse”).
an electrical signal
- graded potential
- action potential
Describe the basic structural divisions of the neuron.
Describe the myelin sheath
Myelin = insulating layer/sheath that forms around nerves
~allows electrical impulses to transmit quickly and efficiently along the nerve cells.
~If myelin is damaged, these impulses slow down
What does the term “saltatory conduction” mean?
the rapid method by which nerve impulses move down a myelinated axon with excitation occurring only at nodes of Ranvier
Going from slow action potential to very fast electrical transmission to slow AP to fast ET to slow AP , back and forth
Jumping back and forth in between these 2 modes = saltatory conduction [characteristic of a myelinated axon]
textbook definition: jump of action of AP from node to node
Describe the distribution of ions across the cell membrane at rest. How does the cell maintain a “resting potential”?
More potassium inside cell; more sodium outside cell
Cell maintains a resting potential with
~leak channel
~sodium potassium pump [leaky potassium pushed in, sodium kept higher outside cell]
Where in the neuron do you find graded/local potentials?
in dendrites & cell bodies
Compare and contrast the absolute refractory period and the relative refractory period.
When do they occur, what is responsible for their occurrence, and what is the effect of their occurrence?
Absolute RP-
-first half- stage 2 (channels open, inactive)
-2nd half- stage 3 (channels closed, inactive)
~so it is impossible to stimulate another AP bc impossible to stimulate the voltage-gated sodium channels.
Relative RP-
~sodium channel is in its active phase (1), so it is possible to produce a voltage stimulus to open the sodium channel; but also, cell is hyperpolarizing and potassium channels are open; as a consequence, any voltage applied has to overcome potassium’s effect
5 steps of synaptic conduction
1) an AP depolarizes the axon terminal
2) this opens voltage-gated calcium channels and calcium enters the cell
3) calcium entry triggers exocytosis of synaptic vesicle contents
4) NT diffuses across the synaptic cleft and binds with receptors on the post synaptic cell
5) NT binding initiates response in the post-synaptic cell
Compare and contrast the post-synaptic events of primary and second messenger systems
1] receptor channel
~direct or indirect channel
~most common in synapse
direct receptor: NT binds to receptive site on ion channel protein [ion channel is receptor and transporter] protein shape change and opens
indirect channel: the molecule that binds to NT is not the same protein as ion channel [G protein-coupled receptor] Alpha sub unit attaches to channel, opening it.
2] 2nd messenger
~commonly uses cAMP as 2nd messenger; cAMP relays message
Compare and contrast receptor and synaptic potentials.
Receptor potentials
~All properties of graded potential, BUT they are always depolarizing
~graded potentials in dendrites
Synaptic potentials
~When AP arrives at the terminal, there is synaptic communication and a graded potential in the dendrite (this is the synaptic potential- still a graded potential).
~Can be depolarizing/excitatory [can stimulate voltage gated channels to open] [EPSP] or hyperpolarizing/inhibitory [cannot stimulu voltage gated channels to open] [IPSP]
Compare and contrast “EPSP’ and “IPSP”.
2 types of synaptic graded potentials
EPSP- excitatory- depolarizing post synaptic potential
~creates a ripple effect through cell; if at initial segment, amplitude is large enough = action potential
IPSP- inhibitory- hyperpolarizing PSP
~decreases potential that other stimuli will trigger an AP
Define “spatial summation”. Provide an example.
when 2 graded potentials occur at 2 different locations, they are added together at the axon hillock
Define “temporal summation”. Provide an example.
a graded potential is produced, and shortly after another is produced, adding on top of the first one
[separated by time]
What is the significance of the initial segment to summation? What is the significance of summation?
Electrical summation takes place at the initial segment
the deciding point about whether AP occurs or not
_________ do the communication, integration, decision making, memory generating process in the NS
Neurons
The neuron can generate:
a nerve impulse
[electrical signal]
One type of nerve impulse is a graded potential; it is restricted to :
dendrites and cell body of the neuron and does not have transmission capability
A type of nerve impulse, _________________, is the typical example; associated with axons down to terminals; a true transmission form of electrical change/excitation of cell
an action potential
Describe the 3 signaling formats within the NS
cell bodies/ dendrites: graded potential
axons: action potential [rapidly travels down axon]
terminal: neurotransmitter- chemical messengers [no physical contact w/ next neuron]
Describe the center of the neuron
center with nucleus
metabolic cell center = cell body/ soma
the _______________ AKA receivers/receiving end are the input point for signals coming from other cells or from the environment
dendrites
All of the information induced in the dendrites when they receive an input is relayed to
the cell body
> sends out the info in a single axon
Action potentials will travel:
very rapidly down the length of the axon to the terminals