114. Describe the structure of a synapse and explain how it operates?

Answer: Synapses occur between two neurons. Electrical activitiy in the pre-synaptic neuron influences the post-synaptic neuron. There are two types of synapses in the body: Electrical and chemical. Electrical synapses occur in pre and post synaptic neurons that are joined via gap junctions. Currents from action potentials flow across the junction through channels called connexons. This current will depolarize the membrane of the post synaptic neuron to threshold, which will continue the action potential in the cell. Electrical synapses are fast and bidirectional. However, they are mainly found in cardiac and smooth muscles, and not in the mammalian nervous system. Chemical synapses use neurotransmitters. Depolarization occurs in the pre-synaptic neuron and calcium ions rush in. The calcium ions activate neurotransmitter release into the synaptic cleft. The neurotransmitters reach the post-synaptic neuron and cause action potentials to develop.

Section X Biochemistry of the Muscular tissue

1. Anaerobic glycolysis occur under conditions of relative oxygen insufficiency. This biochemichal process is accompanied by the pH decrease in tissues resulting from the accumulation of:

А. Lactate

В. Citrate

С. Oxaloacetate

D. Succinate

Е. Fumarate

2. The fastest mechanism of ATP production for the urgent muscular contraction is:

А. ATP generation from creatine phosphate

В. Aerobic glycolysis

С. Anaerobic glycolysis

D. Glycogenolysis in muscles

Е. Triglicerides oxidation

3. In muscular dystrophies the production and excretion of creatinine is inhibited. But what index is increased in urine under these conditions?

А. Creatine

В. Urates

С. Porphyrins

D. Indicanes

Е. Bilirubin

4. Organ-specific enzymes are evaluated for the diagnosis of some diseases. What enzymes are determined to diagnose muscular dystrophies?

А. Aspartate aminotransferase, kreatine kinase

В. Arginase, pyruvate decarboxylase

С. Alanine aminotransferase, urease

D. Hexokinase, phosphorylase

Е. Fumarase, superoxide dismutase

5. The huge amount of nitrogen, derived from the amino acids, is excreted from the human organism with urea in the form of creatinine. Which amino acids participate in biosynthesis of creatine?

А. Glycine, arginine, methionine

В. Glycine, phenylalanine, cysteine

С. Valine, serine, tyrosine

D.Tryptophan, lysine, alanine

E. Leucine, histidine, glutamine

6. Indicate the right sequence of the biochemical information transfer in the mechanism of muscular contraction?

А. Са → Troponin → Tropomyosin → Actin → Myosin

В. Са → Troponin → Tropomyosin → Myosin → Actin

С. Са → Actin → Myosin → Troponin → Tropomyosin

D. Са → Tropomyosin → Troponin → Actin → Myosin

Е. Са → Tropomyosin → Troponin → Myosin → Actin

7. The sportsman ran a marathon distance, resulting in a production of lactate in his muscles. The biggest amount of this lactate:

А. Gets to blood, is caught by liver where it is converted to glucose

В. Gets to mitochondrias and is oxidized to pyruvate

С. Is excreted with urea

D. Is used for the glucose synthesis in the muscular tissue

Е. Is accumulated in the organism, causing acidosis

8. What reaction in skeletal muscles causes ATP production for the urgent muscular contraction?

А. Creatine phosphokinase

В. Phosphofructokinase

С. Adenylate kinase

D. Glucokinase

Е. Hexokinase

9. A 30 year old patient manifested a decreased tolerance to physical exercises, whereas the content of glycogen in his muscles increased. The decrease of what enzyme caused this condition?

А. Glycogen phosphorylase

В. Phosphofructokinase

С. Glycogen synthase

D. Fumarase

Е. Succinate dehydrogenase

10. The main biochemical regulator of the muscular contraction and relax is the change of the ions of:

А. Са⁺⁺

В. К⁺

С. Mg⁺⁺

D. СІ^-

Е. Na⁺

11. In the course of studies it was evaluated that muscular contraction needs energy in the form of:

А. ATP

В. GTP

С. CTP

D. ADP

Е. AMP

12. Within short-termed muscular work with maximal activity the following processes are the source of ATP:

А. Anaerobic breakdown of glycogen

В. Resynthesis from creatine phosphate

С. Anaerobic glycolysis

D. Adenilate kinase reaction

Е. Fatty acids oxidation

13. The fibrillar proteins include:

A. F-actin

B. Myosin

C. Troponin

D. Tropomyosin

E. a- and b - actinin

14. During water extraction of muscular and nervous tissue the following compounds are released into the water solution:

A. Anserine

B. GABA

C. Carnosine

D. Creatine

E. Cholesterol

15. In which organs is creatine phosphate synthesized?

А. Kidneys and liver

В. Adrenal glands

С. Lungs

D.Pancreas

Е. Spleen

16. Which statements on the white muscular fibers are right?

А. They are characterized by anaerobic carbohydrates catabolism

В. Contain more glycogen than the red fibers