Neurotransmission Flashcards
Resting membrane potential voltage
-80 mv
Threshold voltage
-55 mv
Which communicates faster?
Chemical or electrical synapse
electrical
Slower, more controlled communication
chemical synapse
Primary cellular communication forms
Chemical (NTs)
Electrical (passive/active conduction)
Chemical communication uses
NTs
Synapse/synaptic cleft is located between…
the nerve terminal
&
post synaptic membrane
If we open Na channels on the post synaptic membrane, what happens?
depolarization
T/F
Normally, ICF is polarized.
True
When negative voltage becomes more positive, it is called
depolarization
more positive/closer to 0
Allows nearly instant binding of NT to post-synaptic membrane
synapse is very small
pre & post synaptic membranes very close together
Neurons act as _____. They take info coming in and will fire/not fire, depending on ____ & ____.
integrating engines
timing
sequence
Synapse locations
can synapse on:
dendrite
body
axon
terminal
only thing neurons can do
decide whether to fire or not fire
electrical communication
Passive Conduction
Active Conduction
T/F
Very few places in the brain have true electrical conduction.
True
T/F
Changes in voltage when ions enter the dendrite = change sensed at the cell body.
False
cell body senses only fraction of change that happens at dendrite d/t ion diffusion
(passive conduction)
(Active/passive) conduction utilizes brownian motion.
passive
disruption of charge
as ions diffuse, some of charge is lost
[ ] drops
what increases disruption of charge?
more fluid
longer distance to travel
disruption of charge occurs in (passive/active) conduction
passive
Cl- influx can bring the potential to
-90
active conduction
pass signal down the axon itself
constantly regenerated
voltage DOES NOT DIMINISH (like passive)
(active conduction)
as charge passes along, triggers ______ channels to open.
voltage-gated Na
Wavelike, marching of charge down axon
active conduction
normal resting state (negative charge) is restored by
opening of K channels
K exits
T/F
A wave of depolarization travels down the axon, opening Na channels on one side of the axon, followed by K channels on the other side.
False
Na and K channels are intermixed on the axon
T/F
Na channels on the post-synaptic membrane are voltage gated.
False
Na channels on axon are
restores particular ion [ ]
Na/KATPase
3 Na out
2 K in
Na/KATPase
what comes in?
what goes out?
3 Na out
2 K in
Na/KATPase makes ICF more (-/+)
-
T/F
the neuron requires a separate signal to trigger repolarization
False
occurs automatically in response to voltage changes
Influx of Na+ changes voltage to
-40
boutons
nerve terminals
Dendrites (actively/passively) transmits info to cell body.
passively
A neuron’s ribosomes are located in the
cell body/soma
To fire an axon, we stimulate the ___
axon hillock
axon hillock attaches….
axon and cell body
Neuron
ligand channels/receptors
(axon hillock)
receptor zones inside cell
react to particular substance
produces it in nucleus
releases via ribosome/biochem mechanism
T/F
The axon hillock features voltage gated Na channels
false
ligand gated
axon = voltage gated
Intracellular ligand channels in the axon hillock are associated with ___ channels.
Na
How do Na ions enter the axon hillock?
- particular substance binds to intracellular receptor zone (ligand gated)
- substance released intracellularly
- interacts with receptor zone
- opens Na channel
At the axon hillock, a substance binds to & interacts with an intracellular receptor, opening its associated Na channel. This is an example of a ______ gated channel.
ligand
not voltage
axon = voltage gated
ligand gated vs voltage gated channels
-what opens them
-location
Initiation of a signal occurs by activating (ligand/voltage) gated Na channels at the axon hillock.
ligand
- stimulate ligand-gated Na channels (hillock)
- Na enters, increasing voltage
- stimulates the adjacent voltage-gated channels (axon)
_____ gated Na channels initiate positive depolarization at the ____ ____ that is sensed by the ____ gated Na channels adjacent to them.
ligand
axon hillock
voltage
T/F
Ca channels can be voltage gated
True
present esp at nerve terminal
triggers fusion of vesicles with terminal membrane
Ca influx
T/F
vesicle membranes are made of the same material as the membrane on the outside of the nerve terminal
True
fusion creates weak point
terminal absorbs vesicle membrane
pulls open
forces contents into synapse
Mechanism
Fusion of vesicle and terminal
(made of same material)
1. fusion creates weak point
2. terminal absorbs vesc. memb.
3. pulls vesc. open
4. contents into synapse
5. vesicle memb incorporated into nerve terminal
6. terminal constantly being pinched off to make more vesicles
2 types of axons
myelinated
nonmyelinated
myelinated sheaths of PNS
schwann cells
wrap their membrane around axon
Schwann cells ___ the axon, bc cell membrane is made of ___ material
insulate
lipid
Schwann cells/myelin sheaths, prevent penetration of ___.
ions
(myelinated axon)
the only place ions can enter
nodes of Ranvier
(gaps between myelin sheaths)
myelin is made up of ….
EC membrane
myelinated axon benefits
-less energy required
-faster conduction
“saltatory conduction”
jumps current between nodes
(myelinated axon)
Na channels are only located…
in the nodes of Ranvier
(gaps between myelin sheaths)
T/F
Most nerves are myelinated.
True
T/F
Most nerves in the periphery are myelinated.
True
T/F
All motor nerves are myelinated
True
Motor neurons only synapse in the periphery at…
their final point of contact (the muscle)
(myelinated/non-myelinated) nerves are more likely to be disrupted by ion channels/current in ECF.
non-myelinated
(myelinated/non-myelinated) have less ion channels, so there is less transport of ions, and thus requires (more/less) energy for Na/KaTPase
myelinated
less energy
T/F
all nerves have the same resting potential
False
but
all within same range -60 to -90
⭐️
normal ion [ ]
When Na enters cell, voltage becomes
-40 to -30
depends on how much enters
⭐️
Primary contributor to resting charge is
K+ channels
Which ion is a secondary messenger?
Ca
only channel open at rest (-70 mv)
K+ channels
-70 is negative enough to where we can keep K in the cell
electromotive forces = diffusional forces
electromotive force
charges of ECF/ICF and charge of ion interact to either facilitate or inhibit movement across membrane
entrance is opposed by electromotive force but aided by diffusional force
Cl-
- charge & - ICF = repels
[ ] gradient: High ECF, low ICF = facilitates
entrance is aided by electromotive force and diffusional force
Na+
+ charge & - ICF = facilitates
[ ] gradient: High ECF, low ICF = facilitates
Why does Na enter so rapidly?
electromotive force & diffusional force favors its entrance into cell
exit is inhibited by electromotive force but aided by diffusional force
(as K is leaving the cell)
K+
+ charge & - ICF = holds it inside cell
[ ] gradient: high ICF, low ECF = facilitates exit
Why does more Na enter cell than K exiting?
Na entrance aided by electromotive & diffusional forces
K exiting only favored by diffusional forces
T/F
All K and Na channels open at the same voltage.
False
but they work the same way
How can K gradients be kept in balance if the channel is open at rest?
at rest = -70
-70 is negative enough to where we can keep K in the cell
electromotive forces = diffusional forces
At ___ mv, there is no net movement of K b/c…
-70 mv
electromotive forces = diffusional forces
Dendritic Conduction is an example of (passive/active) conduction.
passive
Axonal Conduction is an example of (passive/active) conduction.
active
Axonal = active
restores chemical equilibrium
Na/K/ATPase
Signal initiated at ____ by ….
axon hillock
internally ligand-gated Na+ channels
T/F
In order for the action potential to travel across the axon, there must be a fully positive charge.
False
does not need to be positive
it just becomes less negative
Channel plugs exist in…
a tri-state
hysteresis
oscillation occurring in a physical process
(structure goes back and forth between 2 forms)
Also:
Lag between plasma [ ] & drug rcptr [ ]
Tri-state allows the system to ___ itself.
reset
Existing in a tri-state prevents ____
hysteresis
Increases conduction rates
- Myelination
-Decreased Capacitance
-Saltatory Conduction - Higher resting potential (less - = closer to having Na ch open)
- Increasing Na+ channel density
- Increasing Axonal diameter (less resistance to impulse’s flow; fit more ions)
Capacitance
movement of ions across a membrane
Myelination (decreases/increases) capacitance
decreases
(can only move ions at nodes of ranvier)
Ions in smaller diameters have less movement/slow down d/t…
interact with membrane and other charges
T/F
Small diameter increases conduction rate.
False
decreases conduction rate
Synaptic Transmission occurs at
bouton/nerve terminal
Terminal membrane is gradually lost and is replenished by…
synthesized in cell body
transported down axon to terminal
T/F
Vesicles are usually composed completely of NTs
False
NT maybe primary substance
other components present (ie: proteins)
Vesicles contain ____ neurotransmitter
1 quanta of
1 quanta = ___ NTs
5,000-10,000
Vesicles are reformed by an (endo/exocytotic) process, and can then be refilled
endocytotic
(pinching off)
When wave of depolarization reaches nerve terminal, what happens?
-Ca channels open
-Ca influx (down its gradient)
-triggers S.R. to dump its Ca into ICF
-S.R.’s ion pump dumps into ECF
-very quickly taken back up w/ extra Ca that came in
Most ICF Ca is located in…
sarcoplasmic reticulum
multifolded tissues that store lots of Ca inside
sarcoplasmic reticulum
The surface of the sarcoplasmic reticulum has many _____
Ca ion pumps
What causes the large increase in Ca [ ] at the nerve terminal?
SR dumps its Ca into ICF
(not the Ca channels that are triggered when depolarization reaches terminal)
When Ca pumps complete their fxn at nerve terminal, the ICF has ____ Ca.
nearly net 0
Axon fibrils
rotating fibers
transport mechanism
ie: vesicles from soma –> terminal
How to make vesicles
- vesicles produced in cell body
- transported down axon
- filled & used at terminal
-OR-
endocytotic process (pinching off membrane)
T/F
Vesicles hold a consistent # of NTs
False
Primary Excitatory NTs (7)
Acetylcholine
Norepinephrine, Epinephrine
Dopamine
Serotonin (at ionophoric 5-HT3)
Glutamic Acid
Aspartic Acid
Most numerous primary excitatory NTs
Glutamic Acid, Aspartic Acid
Serotonin is excitatory at ____ but inhibitory at _____
excite: ionophoric 5-HT3
inhibit: G-protein type receptors
“excite my ions!”
Primary Inhibitory
Gamma Amino Butyric Acid (GABA)
Glycine
Serotonin (at G-protein type receptors)
resting state/region of next AP
Na+ channel is closed
membrane potential -
refractory
Na+ channel inactive
membrane potential -
depolarized
Na+ channel open
membrane potential +
Na+ enters the channels when the region is ____
depolarized
Na+ channels are open when…
the region is depolarized
Na+ channels are inactive when…
refractory
(the AP just passed over this region)
Na+ channels are closed in the resting state and when…
its the next region the AP will trigger
When is membrane potential +?
depolarization
When _____, the Na+ channel plug goes into the lumen d/t …
refractory/inactive
adjacent Na ions change channel shape
T/F
ACh is inhibitory
False
All volatile agents are highly potent inhibitors of _____ receptors
nicotinic acetylcholine (nAChr)
T/F
NTs are voltage dependent
True
requires influx of Ca++ into the presynaptic terminals
T/F
Myelination increases capacitance, leading to faster conduction.
False
decreases capacitance
(Capacitance: movement of ions across membranes)
Myelination requires less energy b/c…
conserves membrane potential with less ion transfer
less energy needed to reestablish Na+/K+ concentration gradients
Ca Channels on the bouton are ___ gated
voltage
Afferent nerve fibers
Type A fibers: largest diameters, fastest; myelinated; divided into alpha, beta, gamma, delta
Type B fibers: smaller diameter; myelinated
Type C fibers: smallest diameter; unmyelinated; slow pain, pruritis, temperature sensation
transmission (impulses btwn neurons) is mediated by ___ while transduction (AP) is conducted by ___.
Transmission = Neurotransmitters
Transdxn = channels w/in membrane
Norepinephrine receptor activity
excitatory at A1 receptors
inhibitory at A2 receptors
Inhibited by antiemetic
Serotonin
T/F
etomidate acts on GABAr
True
Coagonist at the N-methyl-D aspartate (NMDA) receptor
glycine
Principle inhibitor neurotransmitter in spinal cord
glycine
increases Cl- into the cell, causing hyperpolarization
T/F
The PNS and SNS are part of the motor aspect of the nervous system.
True
motor portion of ANS:
SNS and PNS
Neurons are surrounded and protected by
glial cells
Types of Glial cells in CNS
Astrocytes: anchor to blood supply; exchange between neurons and capillaries
Microglial cells: immune defense
Ependymal cells: create, secrete, and circulate CSF
Oligodendrocytes: myelin sheath
(CNS glials: “C.A.M.E.O.”)
Types of Glial cells in PNS
Satellite cells: surround & support (like astrocytes)
Schwann cells: myelin sheath
“P.S.S.”
Multipolar neuron
one cell body, one axon, and a bunch of dendrites
Most of our neurons are multipolar neurons, especially motor neurons and interneurons
Bipolar neuron
two processes (“bi-“) with an axon and a single dendrite extending from opposite sides of the cell body
just one process; usually found on sensory receptors
unipolar neuron
How we respond to threats/pain
SENSORY receptors detect stimulus
⬇️
interneuron (CNS; process info (integration)
⬇️
motor neuron
⬇️
sends response to skeletal muscles to contract and pull away
⬇️
React
motor effectors = MOTOR response
determines movement of the ions in/out of the cell
Electrochemical gradient
open in response to physical stretching of the membrane
Mechanically-gated channels
summation
electrical potentials combine at the axon hillock
(process that determines whether or not an AP will be generated by the combined effects of excitatory and inhibitory signals)
T/F
multiple APs can be generated at once
False
one at a time
uniform strength and speed
Restores RMP from hyperpolarized state
NaKATPase
Graded potential
only a few channels open
a little bit of sodium enters the cell
localized slight change in the membrane potential
Action potentials vary in
Frequency
(Less frequent = weak stimulus; more frequent = stronger)
Conduction velocity (speed)
(Myelinated = faster; unmyelinated = slower)
Action potentials don’t vary in
intensity through amount of voltage
T/F
signals can be modified, amplified, inhibited, or split
True
At a synapse this is possible
T/F
Electrical synapses offer immediate communication.
True
Brain outer layer vs inner layer
Outer layer = gray matter
inner layer = white matter
Broca’s area location
left side of frontal lobe
contains Wernicke’s area for written/spoken language
temporal
contains hippocampus and amygdala of limbic system
temporal
The Brainstem connects which two structures?
cerebral cortex to the spinal cord
determines overall level of CNS activity
RAS
sends out reflexive motor signals
midbrain
“Those reflexes are mid, B.”
Limbic system & hypothalamus:
emotions
core temp
___
___
thirst
appetite
short term memory
Hippocampus
sexual and social behavior
Amygdala
Basal ganglia
Inhibitory process is mediated by
dopamine and GABA for skeletal muscle contraction
Ascending/descending tracts in ___ matter
white
Sensory info flows into ___ portion of gray matter; motor info outflow exits from ___ portion
dorsal (posterior)
ventral (anterior)
(S.A.G.’D. : sensory afferent grey dorsal)
T/F
The peripheral nervous system is responsible for integrating sensory information and coordinating both conscious and unconscious activity
False
CNS does this
Meningeal layers
bone
dura matter
arachnoid matter
pia matter
