Deir Yassin Secondary School
Lebanon, Tyre, Al Buss Camp
Scholastic Year 2010 - 2011
Mid Year Exam in Biology
Name: ..............................................
Grade: 12 (Ec)
Date: 8/2/2011
Duration: 60 mints
Exercise One :
( 2 pts. )
Indicate the right statement ( s ), and correct the false one(s).
1234-
To obtain an acquired reflex, the neutral stimulus should proceed the natural one.
Ach, at the level of skeletal muscles, provokes muscular contraction, thus it is an inhibitory neurotransmitter .
Na+ channels open at the level of excitatory synapses.
Across a synapse nerve message propagate in one direction from post to pre- synaptic structure.
Exercise Two :
( 6 pts. )
In the framework of studying the effect of morphine on the transmission of pain messages, morphine was injected at
a specific time , where the frequency of the pain message was recorded before and after morphine injection. The
results are given in the table below.
Time (min.)
0
5
10
15
20
25
Frequency of pain message (a.u)
0
4
6
8
0
0
↑
Morphine Injection
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Construct a graph that represents the variation of frequency of pain message (a.u) as function of time (min.)
Analyze the above results , what can you deduce concerning the role of morphine.
Formulate a hypothesis that explains the mode of action of morphine.
Name a neurotransmitter that stimulates the transmission of pain anad a one that inhibits it.
“ morphine has more durable effect than enkephaline “ . Explain why ?
Exercise Three :
( 4.5 pts. )
Amphetamines are substances used to fight fatigue. Their consumption leads to cognitive and psychic troubles,
decrease in body weight , liver and kidneys disorders, cardiac and vascular troubles, and degradation of nerve cells.
Like cocaine, amphetamines increases the concentration of dopamine in the synaptic cleft.
In fact , amphetamines enter into the presynaptic buds by dopamine carriers. Once the are in the presynaptic
buds, amphetamines induce the expulsion of dopamine molecules stored in the vesicles into the synaptic cleft.
Moreover , amphetamines decreases dopamine recapture, and when they are in high concentration, they inhibit an
enzyme , mono – amine Oxidase A , which degrades dopamine.
As a result, the concentration of dopamine increases in the synaptic cleft. Amphetamines lead to a strong
psychological dependence, mild physical dependence, and very strong tolerance. Amphetamines ‘ withdrawal
leads to insomnia and depression.
1- Pick out from the text :
a- The consequences of amphetamines ‘ consumption.
b- The effects of withdrawal of amphetamines.
c- The action of high concentration of amphetamines at the level of a synapse.
2- Referring to the acquired knowledge and to the text :
a- Justify that amphetamines act as a drug.
b- Explain how amphetamines ‘ consumption prolong pleasure sensation.
Exercise Four :
( 7.5 pts. )
Experiment (A) :
After exposure to an electric shock , the cat escapes.
Experiment (B) :
Presenting a visual signal (light ) followed by an electric shock leads to the escape of the cat .After repeating this
experiment several times , the cat escapes just after presenting the visual signal.
1- What type of reflexes does each experiment represent? Justify.
2- Indicate the pathway of the nerve message during each reflex.
3- Give three differences between these two reflexes.
Good Work