Scheme for Past year's Qs 2010

Problem 1

1- A

2- B

3- C

4- D

5- B

6- 

Problem 2

1- A

2- C

3- A

4- B

Problem 3

1- C

2- D

3- A

4- B

Short essay questions

1. weber-fechner law:

- num.  of nerve impulses in the sensory nerve fiber directly proportionate to the amplitude of the receptor potential, directly proportionate to the log intensity of the stimulus.

- wide variation in the strength of the stimuli will result in only restricted (small) variations in the amplitude of the receptor potential and frequency (impulse) of action potentials discharged along the sensory fibers.

2. Static stretch reflex:

Stimulus	Maintained weak steady passive stretch
Receptor	Nuclear chain
Afferent	Flower spray
Center	Alpha motor neurons in AHC
Efferent	Thick myelinated axons of alpha motor neurons
Effector	Extrafusal fibers
Response	Muscle tone (neurogenic,  maintained, subtetanic muscle contraction)

3. Declarative memory

A) short-term memory

-change the sensitivity of synaptic transmission btw neurons.

-presynaptic facilitation or inhibition at synapses

-lasts for seconds up to several minutes

-new or facilitated pathways = memory traces

B) long-term memory

-structurally changes occur in synapses such as

         i.            Increase num of  vesicles release sites for secretion of transmitter

       ii.            Increase num of transmitter vesicles released

     iii.            Increase num of presynaptic terminals

    iv.            Change structure of dendrites – transmit stronger signals

4.  A) photoreceptor potential

dark

light

I.            cGMP gated channels open     II.            Na n Ca enter outer segment  III.            Na accumulate in outer—go to inner segment—pump out  IV.            Ca also pump out     V.            Inward current keeps the receptor depolarized near -40mv  VI.            Synaptic transmitter (glutamate) is continually released.

i.  Structurally change from kinked form to straight form of retinal                       ii. Conformational change of metarhodopsin of photopigment                       iii.  Activation of transducin                       iv.  Activation of PDE                        v.    Decrease intracellular cGMP                        vi  Closure of Na channel                       vii. Hyperpolarization          viii. Decrease of synaptic transmission                         ix.    Response in bipolar cells (depolarization) and other neural elements.

B) role of cGMP

dark	light
i.            cGmp bound wif Na channel ptn—causes splints (open state)       ii.            Na influx     iii.            depolarized	I.    metarhodopsin 2 activate transducin                       II. active transducin activate PDE—breaks cGMP into 5 GMP                      III.   no more splinting –Na channel close up                       IV.    decrease Na influx                        V.       hyperpolarized

CREDITS TO ANONYMOUS =)