Chemicals that allow nerve impulses to transmit between neurons are called
a. vesicles.
b. neurotransmittors.
c. axon terminals.
d. synapse.
dermis means
a. elastic skin.
b. final layer.
c. true skin.
d. thin layer.
which of the following statements is not true about the immune system?
a. there is more lymphoid tissue in adults than in children.
b. in children, lymphatic tissues such as adenoids, tonsils, and lymph nodes enlarge as growth continues and from exposure to microorganisms.
c. disease, poor nutrition, or poor environments can damage the immune system.
d. in later adulthood, the thymus gland starts to degenerate.
insulin is to glucagon as
a. morning is to afternoon.
b. wet is to dry.
c. a key is to a lock.
d. walking is to running.
if a person has neither of the two blood antigens, what is his or her blood type?
a. a
b. b
c. o
d. ab

Chemicals that allow nerve impulses to transmit between neurons are called neurotransmitters. These are chemicals, often amine based such as dopamine, that effect the transmission of signals or impulses between neurons. Some neurotransmitters are excitatory (i.e. glutamate) which stimulates the post-synaptic neuron; some neurotransmitters are inhibitory (i.e. gamma aminobutyric acid) which inhibits the activity of the post-synaptic neuron. 

Dermis means true skin. The skin has 3 layers: (1) epidermis, (2) dermis, and (3) subdermis or subcutaneous layer. The dermis is the skin layer immediately underneath the epidermis. The dermis is the true skin such that sebaceous glands, sweat glands, blood vessels, connective tissues, hair follicles, neural receptors and other nerve endings, etc. are found in the dermis. The dermis also functions to nourish the cells in the epidermis. 

Which of the following statements is not true about the immune system? The correct answer is: There is more lymphoid tissue in adults than in children. There are actually less lymphoid tissue in adults than in children. First of all, there is this phenomenon called thymic involution wherein the thymus gland starts shrinking and eventually functionally disappearing by adulthood, thereby reducing the mass of lymphoid tissues. Children generally has more lymphoid tissues as these structures in children are very active since lymphocytes are still "learning" to combat different diseases. 

Insulin is to glucagon as wet is to dry. Insulin and glucagon functions oppositely or antagonistically of each other. Insulin decreases blood glucose levels (usually after a meal) by stimulating the absorption of blood glucose into muscle and fat tissue. Glucagon, on the other hand, increases blood glucose levels (usually on fasting states) by stimulating gluconeogenesis and glycogenolysis producing glucose to the blood stream.

If a person has neither of the two blood antigens, what is his or her blood type? The correct answer is blood type O. Blood antigens are proteins embedded on the cell membrane of the red blood cells. There are also blood antibodies that are "anti-antigens" present in the plasma. Blood type O has no red blood cell antigens but have both anti-A and anti-B antibodies in the plasma.

Blood type A has A antigens on the red blood cell membrane and have anti-B antibodies in the plasma. Blood type B has B antigens on the red blood cell membrane and have anti-A antigens in the plasma. Blood type AB has both A and B antigens on the red blood cell membrane but has no antibodies in the plasma.