CSD 431 EXAM 1 QUESTIONS WITH
COMPLETE SOLUTIONS
define diffusion & electrostatic pressure - Answer--*Diffusion*: ions moving from an area
of high concentration to an area of low concentration.
-*Electrostatic pressure*: alike charges repel, opposites attract.
ACTION POTENTIAL - define, what happens, sodium potassium pump - Answer--*A
rapid change in potential when ions that were not able to cross the membrane suddenly
can.*
-A stimulus causes the resting potential to move from -70mV toward 0, and at -55mV
VGICs open (critical threshold level).
-Na+ enters the cell through these VGICs bc of diffusion and electrostatic pressure.
-This causes rapid depolarization in the cell until its charge peaks at +40mV, the peak of
action potential.
---VGICs close around +35mV.
-To get back down to -70, K+ must leave the cell through different VGICs that open
around +35 and close around -60 (re-polarization).
-*sodium potassium pump*: requires *metabolic energy* to pump Na+ out of the cell and
K+ into it. This allows the cell to recover from the chemical transfer that occurred in
action potential.
Adrian - what did he want to know, what was his method, what principle did he establish
? - Answer--Investigated how the cell codes for intensity of stimulation (e.g. light touch
vs. hard slap).
-He takes an electrode (highly conductive wire) to measure action potential in a skin
sensory fiber (which responds to touch) & stimulated the skin with both intensities.
-*Frequency of firing*: for more intense signals, there are more action potentials in a
given time period.
-*All-or-none principle*: action potential either fires or it does not (if it doesn't reach -
55mV)
the synapse - electrical process of communication - Answer--Space between cells = gap
junction.
-One neuron "excites" the next neuron by "jumping" the signal over the synaptic cleft.
-Not much flexibility in the NS this way.
the synapse - CHEMICAL SIGNALING: the process - Answer--1. VGIC in the
presynaptic cell's terminal opens at the peak of action potential.
-2. Ca2+ flows into the terminal through this VGIC.
-3. Influx of Ca2+ causes one vesicle filled with neurotransmitters to migrate and bind to
the presynaptic cell's membrane, creating a little dimple.
-4. Diffusion causes the NT to go out into the synaptic space to the postsynaptic cell's
receptor, which is coupled with a *ligand-gated ion channel*.
, -5. If NT fits, LGIC opens to allow the ions to flow across the membrane.
-6. LGIC is closed when the NT is taken out of the receptor (either by reuptake or
enzymatic deactivation)
the synapse - CHEMICAL SIGNALING: types of neurotransmitters - Answer--Glutamine
= excitatory.
-GABA = inhibitory.
-*Excitatory post-synaptic potential (EPSP)*: makes the action potential in the
postsynaptic cell MORE likely to occur, more likely to reach -55mV and fire.
---Allows positive ions to enter cell and raise the voltage.
-*Inhibitory post-synaptic potential (IPSP)*: makes the action potential in postsynaptic
cell LESS likely to occur.
---Allows negative ions to enter cell or positive ones exit, lowering the voltage.
post-synaptic potentials: spatial summation and temporal summation - Answer--Occurs
as the axon hillock in the postsynaptic cell.
-*Spatial summation*: post-synaptic potentials from multiple synapses around the
dendrites will sum together (including the IPSPs bringing in negative ions).
-*Temporal summation*: time- a combination of PSPs produced over a short time
period.
synapse - reuptake and enzymatic deactivation - Answer--Processes by which the
action of the NT (the opening of LGIC) is stopped.
-*Reuptake*: a pump in the presynaptic cell sucks the excess NT out of the synapse
and back into the presynaptic cell to be reused (active process).
-*Enzymatic deactivation*: enzymes in extracellular fluid change the structure/shape of
the NT, which means that they can no longer bind to the receptors (lock & key).
can synapses vary in strength? - Answer--yuh.
-Charges differ, distance from axon hillock differs.
-Their strengths can change: the more you use a synapse, the stronger the signal
becomes.
Bell & Magendie - how did they disprove Descartes' first assumption that the nervous
system is homogeneous in function (experiment) - Answer--Examined different parts of
the CNS and PNS.
-Cat experiment: cut ventral or dorsal root in cats and observed the result.
-Cutting ventral root: animal could feel stimulus but could not move, so *ventral root
carries motor information* (vroom!).
-Cutting dorsal root: animal could move but could not feel the stimulus applied to the
affected limb, so *dorsal root carries sensory information*.
-Shows that different structures support different functions.
Whytt & Fluorens - how did they disprove Descartes' first assumption that the NS is
homogeneous in function (experiment) - Answer--*Decerebration*: detached the brain
from the spinal cord in cats and frogs.
COMPLETE SOLUTIONS
define diffusion & electrostatic pressure - Answer--*Diffusion*: ions moving from an area
of high concentration to an area of low concentration.
-*Electrostatic pressure*: alike charges repel, opposites attract.
ACTION POTENTIAL - define, what happens, sodium potassium pump - Answer--*A
rapid change in potential when ions that were not able to cross the membrane suddenly
can.*
-A stimulus causes the resting potential to move from -70mV toward 0, and at -55mV
VGICs open (critical threshold level).
-Na+ enters the cell through these VGICs bc of diffusion and electrostatic pressure.
-This causes rapid depolarization in the cell until its charge peaks at +40mV, the peak of
action potential.
---VGICs close around +35mV.
-To get back down to -70, K+ must leave the cell through different VGICs that open
around +35 and close around -60 (re-polarization).
-*sodium potassium pump*: requires *metabolic energy* to pump Na+ out of the cell and
K+ into it. This allows the cell to recover from the chemical transfer that occurred in
action potential.
Adrian - what did he want to know, what was his method, what principle did he establish
? - Answer--Investigated how the cell codes for intensity of stimulation (e.g. light touch
vs. hard slap).
-He takes an electrode (highly conductive wire) to measure action potential in a skin
sensory fiber (which responds to touch) & stimulated the skin with both intensities.
-*Frequency of firing*: for more intense signals, there are more action potentials in a
given time period.
-*All-or-none principle*: action potential either fires or it does not (if it doesn't reach -
55mV)
the synapse - electrical process of communication - Answer--Space between cells = gap
junction.
-One neuron "excites" the next neuron by "jumping" the signal over the synaptic cleft.
-Not much flexibility in the NS this way.
the synapse - CHEMICAL SIGNALING: the process - Answer--1. VGIC in the
presynaptic cell's terminal opens at the peak of action potential.
-2. Ca2+ flows into the terminal through this VGIC.
-3. Influx of Ca2+ causes one vesicle filled with neurotransmitters to migrate and bind to
the presynaptic cell's membrane, creating a little dimple.
-4. Diffusion causes the NT to go out into the synaptic space to the postsynaptic cell's
receptor, which is coupled with a *ligand-gated ion channel*.
, -5. If NT fits, LGIC opens to allow the ions to flow across the membrane.
-6. LGIC is closed when the NT is taken out of the receptor (either by reuptake or
enzymatic deactivation)
the synapse - CHEMICAL SIGNALING: types of neurotransmitters - Answer--Glutamine
= excitatory.
-GABA = inhibitory.
-*Excitatory post-synaptic potential (EPSP)*: makes the action potential in the
postsynaptic cell MORE likely to occur, more likely to reach -55mV and fire.
---Allows positive ions to enter cell and raise the voltage.
-*Inhibitory post-synaptic potential (IPSP)*: makes the action potential in postsynaptic
cell LESS likely to occur.
---Allows negative ions to enter cell or positive ones exit, lowering the voltage.
post-synaptic potentials: spatial summation and temporal summation - Answer--Occurs
as the axon hillock in the postsynaptic cell.
-*Spatial summation*: post-synaptic potentials from multiple synapses around the
dendrites will sum together (including the IPSPs bringing in negative ions).
-*Temporal summation*: time- a combination of PSPs produced over a short time
period.
synapse - reuptake and enzymatic deactivation - Answer--Processes by which the
action of the NT (the opening of LGIC) is stopped.
-*Reuptake*: a pump in the presynaptic cell sucks the excess NT out of the synapse
and back into the presynaptic cell to be reused (active process).
-*Enzymatic deactivation*: enzymes in extracellular fluid change the structure/shape of
the NT, which means that they can no longer bind to the receptors (lock & key).
can synapses vary in strength? - Answer--yuh.
-Charges differ, distance from axon hillock differs.
-Their strengths can change: the more you use a synapse, the stronger the signal
becomes.
Bell & Magendie - how did they disprove Descartes' first assumption that the nervous
system is homogeneous in function (experiment) - Answer--Examined different parts of
the CNS and PNS.
-Cat experiment: cut ventral or dorsal root in cats and observed the result.
-Cutting ventral root: animal could feel stimulus but could not move, so *ventral root
carries motor information* (vroom!).
-Cutting dorsal root: animal could move but could not feel the stimulus applied to the
affected limb, so *dorsal root carries sensory information*.
-Shows that different structures support different functions.
Whytt & Fluorens - how did they disprove Descartes' first assumption that the NS is
homogeneous in function (experiment) - Answer--*Decerebration*: detached the brain
from the spinal cord in cats and frogs.
