The sympathetic and parasympathetic nervous systems are two branches of the autonomic nervous system, which control involuntary bodily functions such as heart rate, digestion, and breathing. These two systems have different neurotransmitters associated with their functioning.
The primary neurotransmitter of the sympathetic nervous system is norepinephrine, also known as noradrenaline. It is released by the sympathetic nerves that originate from the thoracic and lumbar regions of the spinal cord. Norepinephrine is involved in the "fight or flight" response, which prepares the body to respond to stress by increasing heart rate, dilating pupils, and constricting blood vessels.
The primary neurotransmitter of the parasympathetic nervous system is acetylcholine. It is released by the parasympathetic nerves that originate from the brainstem and sacral region of the spinal cord. Acetylcholine is involved in the "rest and digest" response, which promotes relaxation and helps conserve energy by slowing down heart rate, constricting pupils, and stimulating digestion.
