Name_______________________
Biology 3330, Midterm #1, 2005
1.) (11 pts.) a) Matching:
__ GABA
a. begins synthetic pathway for catecholamines
__ Dopamine
b. inhibitory transmitter in vertebrate CNS
__ Acetylcholine
c. released at neuromuscular junctions
__ Tyrosine
d. excitatory transmitter in vertebrate CNS
__ Glutamate
e. lack of this associated with Parkinson's disease
b) Label each neurotransmitter listed below as belonging to amino acid (AA),
monoamine (MA) or peptide (P) transmitter groups.
___ Dopamine
___ Substance P
___ Serotonin
___ GABA
___ Glutamate
___ Enkephalins
2. (6 pts.) In studying a new synapse, you find that the transmitter activates a receptor that is
twice as conductive to K+ as it is to Na+. The equilibrium potentials of Na and K are +50 mV
and -70 mV, respectively.
a) The reversal potential of this synapse should be what value?
b) Explain what the term Reversal Potential refers to, and how it is determined experimentally.
3. (11 pts) In your experiments you find an unusual type of neuron. After applying TTX and
TEA, large regenerative depolarizations can still be observed. To investigate the ionic basis of
this ‘action potential’ you conduct a voltage clamp analysis. At the clamp voltages shown, the
currents below (left) were observed (by convention, these are the opposite of that injected by the
instrument). You also find that these currents are blocked by high levels of Mg ions, which also
eliminates these ‘action potentials’.
a) Increased conductance to what type of ion is probably responsible for producing these unusual
‘action potentials’? What other manipulation could you perform to test this hypothesis?
b) What do the shapes and sizes of the currents observed in the V-clamp experiments reveal
about the properties of the channels that are responsible for this conductance? At the right, draw
the action potential (elicited by 0.3 nA current injection), and explain its shape.
c) Injecting 0.1 nA of positive current results in a 10 mV steady-state depolarization of the
neuron. What is the approximate resistance of this cell?
outward
Inward
Positive current
0 mV
-30 mV
-65 mV
-40 mV
Time
-70 mV
-10 mV
0.3 nA
0.1 nA
-30 mV
4. (6 pts) Consider the neuron shown below, which has two inputs. You record intracellularly
from this cell and stimulate either input #1, input #2 or simultaneously stimulate both inputs. The
resulting recordings are shown above each stimulus trace.
What is a plausible explanation of these results? In your answer, comment on the properties of
chemical synaptic transmission at each synapse (2-3 sentences).
1
2
Stimulating input
#1 alone
#2 alone
1&2 together
5) (6 pts) Following activation of G proteins, a variety of 2nd messenger systems can be
activated. What 2nd messengers are produced by the activity of the following enzymes,
and what actions do these 2nd messengers then have? (They stimulate the activity of what
types of proteins?)
2nd messenger
Protein kinase
Adenylyl cyclase
Guanylyl cyclase
Phosphodiesterase (Phospholipase C)
6) (8 pts) Assume that you construct a cell that has the initial concentrations of K and Cl
ions shown below. The cell is bathed in a fluid of comparable volume that also has
K and Cl, but each is at a concentration of 20 mM. You then incorporate K and Cl
channels of equal number and conductance into the membrane.
-
Cl [20 mM]
-
Cl [20 mM]
+
+
K [20 mM]
-
[100 mM]
K [120 mM]
A [100 mM]
noncharged
molecules for
osmotic balance
a) What ion movements will occur? State the direction of movement and why?
b) If only K channels were incorporated into the membrane, what equilibrium condition
would be established? (use the Nearst equation to calculate equilibrium potentials).
7) (8 pts) For each of the following receptor properties, write I for ionotropic, M for
metabotropic, or B for both:
___ Triggers a fast, short-lasting postsynaptic response
___ Triggers a slow, long-lasting postsynaptic response
___ Binds neurotransmitters such as somatostatin
___ Acts via a G-protein mediated biochemical cascade
___ Acts via phosphorylation of an ion channel
___ Is important in neuromodulation
___ Binds neurotransmitters such as ACh
___ This receptor contains ion channel(s)
8. (8 pts.) On the picture below, label the frontal lobe, parietal lobe, temporal lobe,
occipital lobe, cerebellum, central sulcus, motor cortex and postcentral gyrus.
9. (8 pts.) Match the Cranial Nerves to the symptoms that result were you to damage it:
___ Oculomotor
___ Facial
___ Optic
___ Trigeminal
___ Glossopharyngeal
___ Olfactory
___ Vestibulocochlear
___ Vagus
A.
B.
C.
D.
E.
F.
G.
H.
Inability to see
Inability to swallow; no gag reflex
Inability to chew
Inability to smile
Inability to hear
Inability to smell
Heart rate increase
Pupils stay dilated, impaired control
of eye movement
10. (7 pts.) Match the brain area to its function:
___ Reticular Formation
___ Amygdala
___ Cerebellum
___ Basal ganglia
___ Hippocampus
___ Superior colliculus
___ Inferior colliculus
A.
B.
C.
D.
storage of long term memory
process visual information
important in motor calibration
modulates emotions, important
for expression of fear
E. process auditory information
F. important in control of posture
and planning voluntary
movement
G. modulates sleep and wakefulness
11. (3 pts) Two sensory receptors are stimulated and responses recorded from
corresponding afferent neurons. The following results are obtained.
What phenomenon explains the response of receptor #2 when both #1 and #2 are
stimulated simultaneously? Explain.
12. (10 pts.) Sensory matching
a) In the blanks below, place an R if the coding scheme is range-fractionated or L is it is
labeled-line. Choose the best answer.
___ Coding chemical identity (smell)
___ Coding angle of tilt of the head
___ Coding wavelength of light
___ Coding gentle touch vs. painful mechanical stimulus
b) For each of the following, state whether the primary receptor of the system is a
mechanoreceptor (M), chemoreceptor (C), neither (N), or both (B).
___ Olfactory
___ Visual
___ Auditory
___ Gustatory (taste)
___ Somatic (touch)
___ Balance
13. (4 pts) a) What is Muller's Doctrine?
b) Define Synesthesia. Provide an example and relate the example to Muller's Doctrine.
14. (4 pts) Shown below is a cross-section of a leech with the receptive fields of four
touch receptors:
A.
B.
In response to a touch, the leech will bend away from the stimulus (fig. B). For
example, when the leech is touched at the arrow in fig. A, the leech will bend away
downwards to the left.
What type of coding scheme is being used to encode the EXACT touch location?
In your answer, explain how this coding scheme works.
Some useful equations:
Eion = 58 log [ion]out/[ion]in
V=IR
Q= CV
dv/dt = i/C
1/2
λ = ( rm/ ri)
Em = 58 log [ion Aout] + Perm. ion B/Perm ion A [ion Bo]
[ion Ain+ Perm. ion B/Perm ion A [ion Bi]
V (volts), I (amps), R (ohms)
τ = rm cm