Unit 2: Neurophysiology Flashcards
1
Q
The nervous system is one of two key __________ _________
A
control structures (the other being the endocrine system)
2
Q
List some functions of the nervous system related to information
A
receives info, integrates info, and transduces info
3
Q
What is the pathway of signalling in order
A
stimulus, sensor, afferent pathway, integration centre, efferent pathway, target, response
4
Q
What are the two main parts of the nervous system
A
CNS (central nervous) and PNS (peripheral nervous)
5
Q
What is the CNS made up of
A
brain & spinal cord
6
Q
What is the PNS made up of
A
sensory (afferent) and motor (efferent) neurons (parts of nervous system outside of the brain/spinal cord)
7
Q
What are the two cell types of the nervous system
A
neurons and glial cells
8
Q
What are neurons
A
information messengers that generate and transmit signals over long distances
9
Q
What are neurons made up of
A
soma, dendrites, axon, and axon terminals
10
Q
What is the soma of a neuron
A
“cell body” of the neuron, that contains the nucleus and all biosynthetic materials
11
Q
Why is the soma of a neuron so important
A
center for all chemical processes that keeps the neuron functioning and alive
12
Q
Clusters of cell bodies in the CNS are called
A
nuclei
13
Q
Clusters of cell bodies in PNS are called
A
ganglia
14
Q
What are dendrites
A
the projections of the soma that receive information (dendron = “tree”; look like the ‘branches’ of the soma)
15
Q
What direction do dendrites relay info
A
TOWARD the soma (opposite to axons)
16
Q
What is an axon
A
cytoplasmic extension that relays information
17
Q
What are bundles of axons in the CNS called
A
tracts
18
Q
What are bundles of axons in the PNS called
A
nerves
19
Q
In which direction do axons relay info
A
AWAY from the soma (opposite to dendrites)
20
Q
What is an axon terminal
A
self-explanatory; the ends of an axon that connect the neuron to other cells
21
Q
What is the state of an axon terminal and what process does it contribute to
A
presynaptic: contributes to the synapse
22
Q
What is a synapse
A
the region where an axon terminal connects to its postsynaptic target cell
23
Q
What is the state of the target cell in relation to synapse
A
postsynaptic
24
Q
What is the connection between the presynaptic axon terminal and the postsynaptic target cell
A
synaptic cleft
25
What are the 5 structural classifications of neurons
1. pseudounipolar
2. bipolar
3. anaxonic
4. multipolar-CNS
5. multipolar-efferent
26
What are pseudounipolar neurons
somatic sensory neurons
- axon and dendrites fuse during development into a single long process
27
What are bipolar neurons
smell/vision sensory neurons
- single axon & dendrite
28
What are anaxonic neurons
interneuron with no apparent axon (anaxonic - meaning not axonic)
29
What are multipolar-CNS neurons
interneuron of the CNS
- highly branched neurons with numerous dendrites
- no long extension for the axon
30
What are multipolar-efferent neurons
contains 5-7 dendrites and a single long axon (similar to multipolar-CNS but has one extension vs none)
31
What are the 3 functional classifications of neurons
1. Afferent neurons
2. Interneurons
3. Efferent neurons
32
What does the term interneuron mean
in the CNS
33
What are afferent neurons
receive info from the receptor cells and transmit sensory info TOWARD the CNS
- cell bodies located outside the CNS
- has long cytoplasmic extensions that transmit info to the cells
34
What are interneurons
located inside of the CNS (96% of all neurons), which transmit info within the CNS and integrate information received by afferent neurons and transmit signals to efferent neurons
(basically the connection of signalling info from afferent to efferent)
- main role is to figure out what to do with information and transmit the signal forward
35
What are efferent neurons
receive info FROM interneurons and carry AWAY from CNS
- cell bodies located within CNS
- cytoplasmic extensions transmit information to the effectors/targets
36
What are glial cells
associated with neurons as helpers, but do not carry signals over long distances like neurons do, they communicate only with each other and with nearby neurons
37
What are the two ways glial cells contribute to neuron function
1. aid in nerve impulse conduction
2. maintain the microenvironment around neurons
38
What are the 2 PNS glial cell types
Schwann cells & satellite cells
39
What do Schwann cells form
myelin (layers of membrane)
40
What is myelin
layers of membrane that act as an electrical insulator (formed by Schwann cells in the PNS)
41
What are satellite cells
non-myelinating Schwann cells
42
What do satellite cells do instead of create myelin
support nerve cell bodies (soma)
43
What do Schwann cells secrete
neurotrophic factors
44
What is the node of ranvier
section of unmyelinated axon membrane between two Schwann cells
45
What is the myelin sheath
Schwann cells wrapped around a single PNS axon
46
What are the 4 types of CNS glial cells
1. oligodendria (oligodendrocytes)
2. astroglia (astrocytes)
3. microglia
4. ependymal cells
(review figures 2.4 & 2.5**)
47
What are oligodendrocytes
CNS version of Schwann cells
- wrap around axons & forms myelin to insulate CNS axons
48
What are astrocytes
small star-shaped cells that contact blood vessels and neurons to maintain the microenvironment to help maintain homeostasis in extracellular fluid
49
What are microglia
small specialized immune cells (like macrophages) that function to remove damaged cells and foreign invaders
50
What are ependymal cells
epithelial cells that produce cerebral spinal fluid (CSF)
- creates selectively permeable barriers between compartments of the brain
51
Review and write out the concept map for the nervous system unit
(found on LEARN page under concept maps)
51
**Review and write out the concept map for the nervous system unit
(found on LEARN page under concept maps**)
nervous system = CNS and PNS
CNS = brain & sinal cord
PNS = afferent (sensory) & efferent (motor)
Efferent (motor) = somatic & autonomic
Autonomic = sympathetic & parasympathetic
52
What is the ONLY target of somatic motor neurons
skeletal muscle
53
What are the main targets of autonomic motor neurons
cardiac muscle & smooth muscle
(main focus for this course, but there are others eg. adipose tissues)
54
How do neurons transmit electrical impulses
via energy, stored as an electrochemical gradient
55
The human body is electrically ____________
neutral
56
Separating positive and negative charges requires ________
energy
57
How does the body specifically separate charges
the cell membrane acts as an electrical insulator
58
A difference in charge between the ICF and the ECF creates an ____________ ________________
electrical gradient
59
What structure allows for movement of charge through the membrane
ion channels
60
The difference of +ve (cations) vs -ve (anions) charge between inside and outside of cell is called...
membrane potential
61
What does it mean when saying all living cells have a membrane potential?
they are polarized electrically (to varying extents)
62
Which cells are able to use changes of membrane potential to complete a function
excitable cells
(eg. neurons are excitable b/c changes in membrane potential allow them to relay information)
63
What unit is membrane potential quantified in
millivolts (mV)
64
What two factors determine membrane electrical properties
1. an unequal distribution between the inside (ICF) and outside of the cell (ECF)
- eg. Na+, Ca2+, & Cl- are higher in ECF while K+ is higher in ICF [anions (large, negatively charged proteins) usually higher in ICF]
2. selective movement of these ions across the membrane
- eg. because of size, anions cannot move across membrane
65
IN CLASS REVIEW: Clusters of cell bodies in the PNS are known as...
a. ganglia
b. nuclei
c. tracts
d. nerves
e. ganglia and nerves
a. ganglia
(ganglia=soma in PNS, whereas nuclei=soma in CNS)
(tracts=bundles of axons in CNS, nerves=bundles of axons in PNS)
66
What are the 4 types of selective ion channel
K+ channel
Na+ channel
Cl- channel
Ca2+ channel
67
What is higher concentration in ICF
K+
68
What is higher concentration in ECF
Na+, Ca2+, & Cl-
69
What are anions
large, negatively charged intracellular molecules in ICF
70
What are cations
large, positively charged extracellular molecules in ECF
71
Why do anions not move across the membrane
because of their size
72
What are leak channels
passive transport channels (don't require energy input and are not gated)
73
Does K+ or Na+ have a greater concentration of passive channels in the membrane
K+: there are more passive K+ channels so K+ can move much more freely across the membrane compared to Na+
74
What is equilibrium potential
membrane potential that exactly opposes the concentration gradient of an ion (this is where the electrical and chemical forces acting on the ion are equal and opposite)
75
What is the Nernst equation
E(ion) = (61/z) log ([ion]out/[ion]in)
(looks at what the membrane potential would be for the membrane to be permeable to only one ion)
76
What does the value E(ion) represent
equilibrium potential
77
What does the value z represent
electrical charge of the ion
78
What are the equilibrium potentials for K+ and Na+ in a typical neuron
K+ : -90mV
Na+ : +60mV
79
What is the basic concept of the Nernst equation
looks at what membrane potential would be if the membrane was only permeable to one ion
80
What is the deviation between the Nernst equation and living cells
the Nernst equation focuses on only one ion but living cells have multiple ion types crossing the membrane
81
What concentrations do you need to know in order to complete the Nernst equation
concentration of ion IN & concentration of ion OUT
82
What is resting potential
the charge difference between ICF and ECF at rest
83
What is typical resting potential for a neuron
-70mV
84
When is the neuron no longer at resting membrane potential
when it sends a signal
85
What determines a cells resting membrane potential
the concentrations of ions (K+ greater in ICF, and Na+, Cl-, and Ca2+ greater in ECF) and their relative permeabilities to the membrane
86
What is meant by "excitable" in relation to a cell
the cell will change its membrane potential to complete a job
87
The ion contribution to the resting membrane potential is proportional to _______________
permeability
- this means the more permeable to the membrane, the more important it is for resting membrane potential
88
What type of molecule cannot contribute to the resting membrane potential
molecules that cannot move across the cell membrane (ie. Ca2+ because it moves via gated channels)
89
What is the purpose of the GHK equation
predicts membrane potential using multiple ions (more relative to living cells)
90
What does the value Vm represent
resting membrane potential
91
What does P represent
permeability of the membrane to a specific ion
92
What is the permeability of Ca2+ (remember Ca2+ travels via gated channels NOT leak channels)
0; it does not cross the membrane via leak channels (therefore is excluded from membrane potential equations)
93
What does the K+-Na+ pump offset
the passive flow of Na+ and K+ at rest
94
What is depolarization
decrease in membrane potential difference, membrane becomes LESS negative
95
What is hyper polarization
increase in membrane potential, membrane becomes MORE negative
96
What are the 3 types of gated channels
1. mechanically gated: found in sensory neurons (open in response to physical force)
2. chemically gated: respond to ligands like neurotransmitters
3. voltage-gated: respond to changes in voltage (important in conduction of electrical signals along axons)
97
The gated channels in neurons are for which 4 ions
K+, Na+, Ca2+, and Cl-
98
What are the two types of signal generated by neurons
short-distance signals & long-distance signals
99
IN CLASS ACTIVITY: match the ion to its associated change in the membrane...
1)Na+
2)Cl-
3)K+
4)Ca2+
...predicting whether it will hyper-polarization or depolarization the cell
1) depolarizing (adding positive charges will take it from -70 to less negative)
2) hyper-polarize (adding negative charges will take from -70 to more negative)
3) hyper-polarizing (taking away positive charges will make it more negative)
4) depolarizing (adding positive charges will take it from -70 to less negative)
100
What are graded potentials
can be depolarizing or hyper-polarizing, and occur in the dendrites of the neuron
- triggered by opening or closing of ion channels
- started by ions entering the cell from the ECF
101
Why are graded potentials called "graded"
the amplitude of the potential is relative to the strength of the triggering event
102
Why do graded potentials lose strength as they travel
1. current leak: some charges leak back with the depolarization wave
2. cytoplasmic resistance: cytoplasm resists the movement of the current
103
Since graded potentials lose strength as they move, what distance are they travelled
short distances
104
What causes an ion to enter the cell
initiates by ions binding to membrane receptors and opening ion channels
105
What events occur after neurotransmitters bind
Ion channel opens, ions move in/out, and depolarization/hyper-polarization spreads through the cell
106
What determines signal strength
the number of ions entering/exiting the cell
107
As graded potential travels, ________ is decreased
strength
108
What is another (simpler) term for graded potential
signal
109
What is the different type of signalling used for long distances?
action potential
110
What are characteristics of action potential
- action potentials don't deviate, they are identical (no variation in strength, on or off only)
- action potentials don't diminish in strength as they travel, the signal remains strong the entire distance
111
How is action potential initiated
at the trigger zone (otherwise known as the integrating centre)
112
Where is the trigger zone in a neuron
it varies depending on the type of neuron
113
Where is the trigger zone in sensory neurons
adjacent to the receptor
114
In relation to action potential, if only one action potential occurs, what is the effect on the cell
barely any effect, concentration gradient remains essentially unchanged
- therefore LOTS of action potentials are needed to change the gradient
115
When is the Na+ channel activated during the action potential time frame
at threshold (absolute refractory period)
116
When is the Na+ turned off and when is K+ channel opened during action potential time frame
Na+ closes after threshold, and K+ channels open (absolute refractory period)
117
When do K+ channels close during action potential time frame
relative refractory period
118
Recite the phases of action potential! This is important for the midterm*
do this on a whiteboard and check answers in course notes
119
What are the two key refractory periods
absolute and relative refractory periods
120
When does the absolute refractory period begin
as soon as Na+ channel is opened
121
When does relative refractory period begin
at hyper-polarization (when action potential is lower than -55mV)
if this is unclear look at the graph in course notes and study the curve!
122
What types of channels are the Na+ and K+ channels in action potential
voltage-gates channels
123
What are nodes of ranvier concentrated with?
Na+ channels
124
What is the term used to describe when signals jump from node to node on a myelinated axon
saltatory conduction
125
How is myelin insulation significant
hyperpolarization within the axons is strong enough by the time it hits the next myelinated area
126
Describe the events that occur at the synapse! this is an important concept for the midterm*
check course notes and study this area if unclear
127
What is the space in between the axon terminal and the post-synaptic cell
synaptic cleft
128
When action potential arrives at the axon terminal and the docking protein is activated, what happens?
the docking protein moves off of the axon terminal and becomes a synaptic vesicle, calcium entry from the voltage-gated channels instigates exocytosis of the neurotransmitters, which end up binding to receptors on the postsynaptic cell to relay a signal
129
Summarize somatic, sympathetic, and parasympathetic neurons and their functions. This is important for the midterm*
Read figure 11.9 in course notes and study it
130
What is the target tissue for the autonomic pathway
cardiac and smooth muscle (involuntary muscle types)
131
What is the target tissue for the somatic pathway
skeletal muscle
132
For autonomic pathways, how many neurons are involved?
2
133
Know the receptors released by the pre and post ganglionic neurons and what receptors they each bind to!
134
For parasympathetic preganglionic neurons, what neurotransmitter is released
acetylcholine (binds to nicotinic receptor)
135
For parasympathetic postganglionic neurons, what neurotransmitter is released
acetylecholine (binds to muscarinic receptor)
136
For sympathetic preganglionic neurons, what neurotransmitter is released
acetylcholine (binds to nicotinic receptor)
137
For sympathetic postganglionic neurons, what neurotransmitter is released
norepinephrine (binds to A, B1, and B2 adrenergic receptors)
138
What is another term for sympathetic (think response)
fight or flight
139
For adrenal sympathetic preganglionic neurons, what happens
acetylcholine is released from the axon terminals to the chromaffin cells on the adrenal medulla (on the adrenal gland), then epinephrine is released by the chromaffin cells on the adrenal medulla into the bloodstream
140
For adrenergic receptors, do cells contain multiple types of receptors or just one?
cells only project 1 type of receptor (different cell types have different receptor types)
141
What do B1 and B2 (beta) receptors initiate
cAMP production
142
What do A (alpha) receptors initiate
increase Ca2+ levels in the cytoplasm
143
Nicotinic receptors act via ___ __________
ion channels
144
Muscarinic receptors act via __ __________
G proteins
145
What type of neuron is a chromaffin cell
a modified postganglionic neuron
146
For somatic neurons, what neurotransmitter is released and what receptor is it bound to
acetylcholine, binds to nicotinic receptors (for skeletal muscles)
