Which of the following physiologic principles would be considered a function of the somatic nervous system?

A) Norepinephrine, dopamine, and serotonin:
Depression has been strongly linked to deficiencies in certain neurotransmitters in the brain, specifically norepinephrine, dopamine, and serotonin. These neurotransmitters play significant roles in regulating mood, emotions, and behavior. When their levels are low, individuals may experience symptoms of depression, such as sadness, low energy, anhedonia (inability to feel pleasure), and difficulty concentrating. Antidepressant medications often work by increasing the availability of these neurotransmitters in the brain.

B) Epinephrine, Norepinephrine, and Acetylcholine:
While norepinephrine plays a key role in depression, epinephrine and acetylcholine are not typically highlighted as the primary neurotransmitters involved in depression. Epinephrine (also known as adrenaline) is more associated with the body’s stress response and fight-or-flight reaction. Acetylcholine is involved in memory and learning processes, but it is not the primary neurotransmitter related to depression.

C) Acetylcholine, gamma-aminobutyric acid, and serotonin:
Acetylcholine and gamma-aminobutyric acid (GABA) are involved in many brain functions, but they are not the primary neurotransmitters linked to depression. While GABA may play a role in mood regulation, it is not typically associated with depression in the same way that serotonin, norepinephrine, and dopamine are. Serotonin is the exception in this answer

D) Gamma-aminobutyric acid, dopamine, and epinephrine:
Although dopamine is involved in depression, gamma-aminobutyric acid (GABA) and epinephrine are not the key neurotransmitters associated with the pathophysiology of depression. Epinephrine primarily affects the stress response, and while GABA does influence mood and anxiety, it is not the main neurotransmitter linked to depression itself.

A) The patella reflex ("knee jerk") activated by tapping the patella tendon: The patellar reflex is a monosynaptic spinal reflex that involves the somatic nervous system but is a reflex action rather than a voluntary motor function. The somatic nervous system governs voluntary movements, but reflex actions like the patellar reflex are involuntary responses that do not require higher brain input, though they involve somatic motor pathways.

B) Abdominal viscera the beginning of depolarization in the cardiac conduction of impulses: This process is primarily under the control of the autonomic nervous system (ANS), not the somatic nervous system. The ANS regulates involuntary processes like heart rate and digestion, while the somatic nervous system controls voluntary movements and somatic sensation.

C) The act of typing a report using a computer keyboard: Typing is a voluntary motor activity, controlled by the somatic nervous system. The somatic system is responsible for conscious, voluntary actions such as moving muscles in the arms, hands, and fingers to type. This is the most accurate example of a somatic function.

D) Withdrawing the hand after touching a hot surface: This is a reflex action known as the "withdrawal reflex," which involves the somatic nervous system. However, it is an involuntary action triggered by a sensory stimulus. While it does involve the somatic system, it is not a voluntary action like typing, and reflexes are considered part of the automatic response mechanisms.