Answer:
The hippocampus and amygdala are two parts of the brain that are connected with a fear response. The amygdala is specifically responsible for processing emotional responses, including fear. The hippocampus, on the other hand, is responsible for the formation of memories and plays a role in contextualizing fear experiences.
The thalamus is also involved in processing sensory information and is connected to the amygdala in the processing of fear responses. The thalamus acts as a relay station for sensory information from the sensory organs to the amygdala and other parts of the brain.
Neurotransmitter vesicles are structures within neurons that contain neurotransmitters, which are chemicals that transmit signals between neurons. These neurotransmitters are released into synapses, or the spaces between neurons, in response to neural activity. In the context of fear, neurotransmitter vesicles containing chemicals such as glutamate, GABA, and norepinephrine can be released in the amygdala and other brain regions, contributing to the physiological and behavioral responses associated with fear.
References:
LeDoux, J. E. (2000). Emotion circuits in the brain. Annual review of neuroscience, 23(1), 155-184.
Squire, L. R., & Wixted, J. T. (2011). The cognitive neuroscience of human memory since H.M. Annual review of neuroscience, 34(1), 259-288.
Squire, L. R., Genzel, L., Wixted, J. T., & Morris, R. G. (2015). Memory consolidation. Cold Spring Harbor perspectives in biology, 7(8), a021766.
Kandel, E. R., Schwartz, J. H., Jessell, T. M., Siegelbaum, S. A., & Hudspeth, A. J. (Eds.). (2013). Principles of neural science. McGraw Hill Professional.