Neurotransmission

Neurotransmitters are chemical substances that transmit messages between neurons across synapses. These chemicals are released from the axon terminal of one neuron and travel across the synapse to the dendrite of the next neuron. Thus, the correct answer is Neurotransmitters.

The limbic system is a group of structures in the brain primarily responsible for regulating emotions, memory, and arousal. Key components of the limbic system include the amygdala (involved in emotion processing) and the hippocampus (critical for memory formation).
- The cerebellum (A) is responsible for coordinating voluntary movements and maintaining balance, but it is not involved in emotional regulation.
- The frontal lobe (C) is involved in higher cognitive functions like reasoning, decision-making, and voluntary movements but is not the primary center for emotional regulation.
- The occipital lobe (D) is primarily responsible for visual processing.
Therefore, the limbic system (B) is the correct answer.

Step 1: Understanding the Concept:
Neurotransmitters are chemical messengers in the brain that play a crucial role in regulating mood, emotion, and behavior. Imbalances in certain neurotransmitters are linked to various psychological disorders.

Gamma-Aminobutyric Acid (GABA): This is the primary inhibitory neurotransmitter in the central nervous system. Its main function is to reduce neuronal excitability, producing a calming effect.
Serotonin: Plays a major role in mood, sleep, appetite, and learning. Low levels are often associated with depression.
Dopamine: Associated with the brain's reward system, pleasure, motivation, and motor control. It's implicated in addiction and schizophrenia.
Cortisol: This is a steroid hormone, not a neurotransmitter. It is the body's primary stress hormone.
Step 2: Detailed Explanation:
Anxiety is a state of excessive neuronal activity and arousal. GABA's role is to inhibit or "calm down" this activity. Therefore, low levels or low activity of GABA would lead to insufficient inhibition, resulting in the over-arousal characteristic of anxiety disorders. Many anti-anxiety medications, like benzodiazepines, work by enhancing the effects of GABA.
Step 3: Final Answer:
Anxiety disorders have been linked to low activity of Gamma Aminobutyric Acid (GABA).