Download Name________________________ Midterm #1 Biology 3330, Fall

Name________________________
Midterm #1
Biology 3330, Fall 2014
1. (6 pts) Explain (one sentence), in the space provided on the right, the effects of a lesion in
the following structures:
Structure
Effects of Lesion
a) Cerebellum
b) Substantia Nigra
c) Reticular Formation
d) Frontal Lobe
e) Hippocampus / Temporal lobe
f) Amygdala
2) (6pts) A transformation in the representation of visual information occurs between the
LGN and visual cortex. As a result, simple-type cells in visual cortex are selective for
what stimulus features? Describe the mechanism that underlies this selectivity; in your
answer, explain how intracellular recordings have revealed this mechanism (use a
diagram).
3) (9 pts) Choose the correct answer:

Photoreceptor cells are (depolarized/hyperpolarized) in response to light.

Photoreceptors release (more/less) glutamate when stimulated by light

ON bipolar cells are (excited/inhibited) by glutamate

OFF bipolar cells are (excited/inhibited) by glutamate

The peripheral retina has more (rods/cones)

The peripheral retina is (more/less) sensitive to light than the fovea

The fovea has (higher/lower) acuity than the peripheral retina

Color vision is produced by (rods/cones)

(Horizontal/amacrine/ganglion) cells connect to photoreceptors and to bipolar
cells
4. (6 Pts) The figure below shows the responses of a ganglion cell to a visual
stimulus. Using this figure answer the questions that follow.
a. Using the stimulus-response characteristics of the ganglion cell, can you
explain and identify which type of ganglion cell this is?
b. By summoning your knowledge of the retinal organization could you
explain the activity of such ganglion cell? Use (draw) a simple circuit to
illustrate how the above response characteristics arise.
5). (13 pts) Identify, on the pictures below, the
location of the listed brain structures; put letters in
boxes.
a)
OL: Occipital Lobe
PL: Parietal Lobe
FL: Frontal Lobe
TL: Temporal Lobe
Cb: Cerebellum
CS: Central Sulcus
b)
VC: Visual Cortex
PC: Parietal Cortex
AC: Auditory Cortex
MC: Primary Motor Cortex
PMC: Premotor Cortex
SS: Somatosensory Cortex
PFC: Prefrontal Cortex
c)
SN: Substantia Nigra
Put: Putamen (Basal ganglia)
GP: Globus Pallidus “ “
CC: Corpus Callosum
Thal: Thalamus
AM: Amygdala
CN: Caudate Nucleus
d)
MP: Medullary pyramidal tract
ML: Medial lemniscus
VCN: Ventral Cochlear N.
IO: Inferior Olivary N.
DC: Dorsal Column Nuclei
RF: Reticular Formation
6) (8 pts) Matching:
___ AMPA-type glutamate receptor
___ GAD (Glutamic acid decarboxylase
___ Glutamate
____ GABA-A type receptor
a) Has voltage-dependent ion channels that conduct
Ca+2
b) Enzyme for GABA synthesis
c) Primary excitatory neurotransmitter
d) Ionotropic receptor, mediates fast excitatory
transmission
e) Binding site of benzodiazepines and purines
____ NMDA-type receptor
b) What 3 criteria must be satisfied to prove that a chemical is a neurotransmitter?
7) (3 pts) Properties of sensory systems:
a) Using a diagram and 1-2 sentences, illustrate the principle of Range
Fractionated/population coding, as it applies to color vision.
8) (4 Pts) Circle the correct choices.
a. At threshold voltage the relative ionic permeability of the membrane favors
potassium/ sodium.
b. An action potential can be fired even during the absolute/relative refractory
period by forcing enough positive current into the cell.
c. When cell membrane is strongly depolarized, there is a huge driving force on K+
/ Na+ ions.
d. Action potentials are triggered at the axon hillock/dendritic spine.
9( 6 Pts) Using figure 1 and the concepts you have learned, answer the following questions:
Level 1
Level 2
Level 3
Membrane
voltage
Figure1: An illustration of an experimental stimulation of a neuron using different levels of injected current.
Top trace shows the levels of current injected into the cell, bottom trace shows the changes in membrane
voltage due to current injection.
a. (2 pts) When zero current is being injected the membrane voltage is at -65mV,
explain why a sudden increase in positive current injection results in a ‘curved/slow’
change in membrane potential as indicated in the red dotted circle?
b. (2 pts) Write down the ‘law’ that governs the relationship between a neuron’s
membrane voltage and injected current. Which variable remains constant in this
equation w.r.t. the manipulations in figure 1?
c. (2 pts) Can you explain the type of neuronal coding behavior seen in figure 1
using a biological example that you have come across in this course
10) (8 pts) Matching:
___ ___Bitter
___ ___Sweet
___ Sour
___ Salt
___ ___ Odorant (Olfaction)
___ ___Light (Vision)
a) Proton-mediated closure of K
channels
b) G-protein-mediated increase in IP3
c) G-protein-mediated increase in
cAMP
d) G-protein-mediated decrease in
cGMP
e) Ions directly pass through amiloridesensitive channels
f) Phospholipase C activated
g) Adenylyl cyclase activated
h) Phosphodiesterase activated
b) Describe the actions of the 2nd messengers (cAMP, cGMP, IP3) in the sensory
transduction shown above. In your answer describe the effects of these 2nd messengers
on particular ion channels.
Action
cAMP
cGMP
IP3
11. (6pts) Chemosensory (taste and olfaction): Fill in the blanks.
The main organ of taste is the tongue on which the tip is sensitive to _________,
the back is sensitive to __________, and the sides are sensitive to _______. On the
tongue surface, there are small projections called _________, and each have hundreds of
______________ with several (50-150) ______________, which are responsive to
chemicals indicating tastes. When these cells are exposed to appropriate tastant
chemicals, there are membrane potential changes, called ____________. The majority of
these cells are relatively _________ (qualitative answer) to chemical sensing. The taste
information is then carried by _________ (afferent/efferent) nerves to the
_____________. Axons here make synapses on neurons of the ____________, which
projects to the _______________ of the cerebral cortex. This pathway is presumed to
mediate conscious perception of taste
12. (6 pts) Neurotransmitter systems & Synaptic Transmission
Thien identifies a rare form of familial tremor, in which patients have involuntary tremors
and cardiac irregularities. An undergraduate chemist working with Thien reported that
patients have elevated levels of epinephrine in their blood samples. Thien thought “Aha!
This must involve a malfunction in a rate-limiting step of the epinephrine synthesis!” So
he looked at the epinephrine synthesis pathway.
a). What is the precursor to epinephrine (and DOPA, Dopamine, or norepinephrine)
called? What kind of molecule is it?
b). Above each arrow, give individual names to the molecules catalyzing these reactions
(depending on the reaction). Hint: they are named for the chemical modifications they
produce.
c). What is the step that is rate-limiting in this synthesis?
d). Thien thinks that the molecule that catalyzes this rate-limiting step is overexpressed in
a particular set of neurons. What is the name of the brain region where these neurons are
found? __________
e). Thien has access to mouse models of this disease, and their nervous systems. Describe
how he could identify these neurons.
13. (6 pts) You are recording from a neuron that receives inputs from neurons A and B.
The postsynapse at A contains ligand-gated Cl- channels and has a reversal potential of 60 mV (below threshold for spike initiation). The neuron being recorded has a resting
membrane potential of -70 mV.
a) If only neuron A is stimulated, what will the change in membrane potential
look like? Draw below. (2 pts)
b) When only neuron B is stimulated, there is a depolarization of 30 mV. Draw
what the change in membrane potential would look like if both neurons A and B are
stimulated. (2 pts)
c) Is synapse A excitatory or inhibitory? Explain your answer. (2 pts)
14.(Total: 6 pts) Using figure 2 answer the questions below:
_________ ___________ ___________ ____________
Figure 2: Different states of a voltage gated Sodium channel. Each state of the
channel is represented by a number below the channel.
a. Name each state of the channel indicated in figure 2:
b. Explain the transition of the voltage-gated sodium channel from state 1 to state 2.
Which part of the sodium channel is essential for such transition?
c. Generalized epilepsy with febrile seizures is a common inherited disorder. One of the
causes of this disorder is a mutation in the voltage-gated sodium channel. Could you
name which state transition is affected by such mutation and how? How does this
mutation affect the action potential? (Hint: Batrachotoxin has a similar effect on the
channel function as this mutation.)
15. (Total: 6 Pts) Answer the following questions:
a. (4 pts) Use a simple diagram to explain the projection of neurons/information
from the retina to the lateral geniculate nucleus of the thalamus. In this answer
explain the functional specializations of the 6 layers of the LGN.
b. (1 pt) What is retinotopy?
c. (1 pt)Visual space is not uniformly sampled in the retina. What effect does this
have on the organization of visual field in the striate/V1 cortex?
13. (11pts) You have learned that 2nd messenger systems are important in synaptic
transmission. These 2nd messenger pathways are also important in stimulus transduction in the
visual, gustatory and olfactory systems. Complete the chart showing how sensory stimuli are
transduced by filling the blanks. Each blank can have more than one answer, and the answers can
be used more than once.
A. Adenylyl cyclase
B. Increase Ca2+
release
C. Ca2+ channels open
D. Depolarization
E. Increased IP3
F. Phosphodiesterase
G. Decreased cGMP
H. Hyperpolarization
I. Na+ channels close
J. Cyclic nucleotide
gated channels open
K. PKA
phosphorylates K+
channel, closing it
L. PKC
phosphorylates K+
channel, closing it
M. PLC
N. Decreased Na+,
Ca2+ entry
O. Increased cAMP
Matching:
___ Bitter
___ Sweet
___ Sour
___ Salt
___ Odorant (Olfaction)
____ Light (Vision)
i) Proton-mediated closure of K
channels
j) G-protein-mediated increase in IP3
k) G-protein-mediated increase in
cAMP
l) G-protein-mediated decrease in
cGMP
m) Ions directly pass through amiloridesensitive channels
n) Phospholipase C activated
o) Adenylyl cyclase activated
p) Phosphodiesterase activated
b) Describe the actions of the 2nd messengers (cAMP, cGMP, IP3) in the sensory transduction
shown above. In your answer describe the effects of these 2nd messengers on particular ion
channels.
Action
cAMP
cGMP
IP3
7) (8 pts) a) What is the function of the synapse (1-2 sentences)? (2 pts)
b) Label the key components of the synapse indicated on the image below. Also, label the
presynaptic side and postsynaptic side of the synapse. (6 pts)
8. (3 pts) a) For each of the following receptor properties, write I for ionotropic, M for metabotropic, B
for both, or N for neither:
___ Triggers a fast postsynaptic response
___ Is important in neuromodulation
___ Binds neurotransmitters such as somatostatin
and vasopressin
___ Triggers a slow postsynaptic response
___ Binds acetylcholine
___ Acts via a G-protein mediated cascade