The neurotransmitter ____ creates a sense of feeling good and at low levels may lead to depression.

Clinical depression can be caused by deficiency of

The joints between the bones in the skull are ____ joints.

Match the correct structure of the knee with the number indicated on the image above. 

The iris:

What type of synovial joint is the knee?

The synaptic cleft is

Feelings of physical and emotional exhaustion due to stress from working with people under difficult or demanding conditions is called:

The cell membrane or plasma membrane of the muscle fiber is called:

The ability to ignore unimportant stimuli is called