Neurons Flashcards
(50 cards)
1
Q
neuron types (3)
A
- sensory neuron
- interneuron
- motor neuron
2
Q
neuron structure
A
structural variation:
- can be very long or short
3
Q
neuron components (3)
A
- cell body
- dendrites
- axon
4
Q
neuron cell body
A
- maintains the normal cell functions of the neuron
5
Q
neuron dendrites
A
- receive incoming information
6
Q
neuron axons
A
- communicate electrical signals across long distances
7
Q
where do electrical signals occur in neurons
A
- dendrites, cell body, axon, and synapse
8
Q
glial cells (2)
A
- support and surround neurons to maintain them
- required for proper neuron functioning
9
Q
neural reflex pathways (2)
A
- simplest neural pathways
- don’t involve brain or consciousness
10
Q
sensory neuron
A
- afferent neurons that send signals toward the CNS
11
Q
motor neuron
A
- efferent neurons that send signals away from the CNS
12
Q
sensory receptors and membrane potential (2)
A
- incoming stimulus causes change in conformation of receptor protein
- causes a signal within the cell that ultimately changes membrane potential
13
Q
what determines signal intensity in neurons (2)
A
- frequency of action potentials; # of action potentials/time
- more pressure to neuron when there is higher intensity
14
Q
graded potentials (3)
A
- occurs in dendrites and cell body
- only travel short distances
- vary in magnitude and sign
15
Q
action potentials (3)
A
- occur in axons
- all or none (always look the same within the cell)
- can be regenerated and conducted along long distances
16
Q
synaptic potentials (2)
A
- action potentials arriving at synapse
- cause the release of neurotransmitters
17
Q
what causes electrical signals in neurons
A
- graded, action, and synaptic potentials all result in changes in the membrane potential of the cell
18
Q
depolarization (2)
A
- becoming more positive
- smaller difference between inside and outside of cell
19
Q
hyperpolarization (2)
A
- becoming more negative
- bigger difference between inside and outside of cell
20
Q
membrane potential (3)
A
- voltage differences across the membrane
- always reported as charge inside relative to outside
- in both animals and plants, inside of the cell is more negative than outside at rest
21
Q
Nernst equation
A
- allows you to calculate the equilibrium potential of any ion
22
Q
how do we predict the direction of ion movement
A
- compare the equilibrium potential of that ion with the membrane potential of the cell
23
Q
permeability importance (2)
A
- final membrane potential is a weighted average of the equilibrium potentials of the ions and permeability provides the weighting factor
- increased permeability for an ion will increase its weight/importance
24
Q
why do we only consider Na+, K+ and Cl- in the Goldman equation
A
- permeability of the membrane to other ions is extremely low under resting conditions
25
permeability and equations
- when permeability to one ion is much higher than to other ions, the Nernst and Goldman equations are the same
26
what is the function of changes in membrane potential (2)
- can act as signals within cells
- occur in many cell types in both animals and plants; animals have nerves and tissues that are specialized for electrical signalling
27
what causes changes in membrane potential
- change in the membrane permeability (channels opening and closing)
28
how is permeability regulated
- gated ion channels
29
how do gated ion channels work
- open and close in response to incoming signals
30
what causes a graded potential
- binding of neurotransmitter to a receptor
31
what sets the size of a graded potential
- depends on amount of neurotransmitter
- more neurotransmitter = more channel opening/closing = larger change in permeability = larger change in membrane potential
32
why can graded potentials only travel short distances
- intracellular resistance and leakage of ions across the membrane cause the signal to degrade with distance; gets weaker as it travels
33
how are action potentials triggered (3)
- graded potentials in the dendrites and cell body alter membrane potential in the axon hillock (trigger zone)
- membrane potential must exceed the threshold potential
- results in action potentials in the axon
34
threshold potential
- 55 mV
35
resting potential
- 70 mv
36
spatial summation (3)
- graded potentials originating at different locations can influence the net change in membrane potential, allowing the neuron to reach threshold
- many positive close together grade potentials can cause the neuron to reach threshold
- positive and negative graded potentials can cancel each other out
37
changes in permeability that occur during the action potential
- large increase in Na+ permeability
- followed by increase in K+ permeability
- occurs due to the opening of voltage-gated channels
38
when do Na+ voltage-gated channels open
- when the membrane is depolarized
39
positive feedback of Na" voltage-gated channels (3)
- positive feedback causes rapid depolarization
- Na+ channel activated gates open -> Na+ enters the cell -> more depolarization -> more gates open
- feedback loops closes after a certain amount of channels close
40
how does Na+ channel density affect neuron function (2)
- higher density of voltage-grated Na+ channels creates lower threshold required to trigger an action potential
- increases excitability
41
how do neurons return to resting MP
- inactivation gate on the VG Na+ channel
- VG K+ channels are not required, but are helpful and are responsible for the hyperpolarization phase of the action potential
42
absolute refractory period (2)
- inactivation gate closed
| - no new action potential is possible
43
relative refractory period (3)
- inactivation gate open
- new action potential possible, but less likely because neuron is hyperpolarized
- only occurs in neurons with VG-K+ channels
44
what is the purpose of the refractory periods
- makes it less likely for many action potentials to occur consecutively
45
action potential propogation (2)
- action potentials spread as a wave of depolarization; an electronic current flow
- this triggers actions potentials to be re-generated in nearby regions of the membrane
46
if a neuron is depolarized in the middle of the axon, which direction would the resulting action potential travel? (2)
- in both directions because the inactivation gates are open on both sides
- normally, it will travel toward the synapse due to inactivation gates closing behind it
47
myelin (4)
- formed by Scwhann cells wrapped around axons
- insulates the axon
- allows charge to spread further down the axon without degrading (decreasing below threshold) so that fewer action potentials are needed to send signals
- causes saltatory conduction
48
saltatory conduction
- apparent "leaping" of action potential from node to node
49
synapses (2)
- can be chemical or electrical
| - neurotransmitters are rapidly removed from the synapse
50
chemical synapses
- convert electrical signals to chemical signals
| - neurotransmitters are released into the synapse when VG Ca+ channels open
