2-Minute Neuroscience: Sympathetic Nervous System

Summary

The sympathetic nervous system, a key component of the autonomic nervous system, is responsible for managing automatic bodily functions such as digestion, heart rate, and respiration. Often linked to the 'fight-or-flight' response, it is active in various situations, not just emergencies. Originating from the thoracic and lumbar spinal cord, its neurons travel to sympathetic ganglia and can directly reach the adrenal medulla. The system includes interconnected sympathetic chain ganglia and prevertebral ganglia, with preganglionic neurons releasing acetylcholine and postganglionic neurons primarily norepinephrine, ensuring a diverse impact throughout the body.

Takeaways

• 🧠 The sympathetic nervous system is part of the autonomic nervous system, which is a division of the peripheral nervous system that controls automatic processes in the body.
• 🏃‍♂️ It is commonly associated with the 'fight-or-flight' response, which is the body's way of dealing with alarming or threatening situations by increasing its ability to act.
• 🔍 The idea of the sympathetic nervous system being only active during 'fight-or-flight' is an oversimplification; it is also active in non-emergency situations and during rest.
• 🌱 The nerves of the sympathetic nervous system originate in the thoracic and lumbar regions of the spinal cord.
• 🔗 These nerves typically extend to clusters of neurons in the peripheral nervous system known as sympathetic ganglia, rather than directly to their targets.
• 🚫 An exception to this is the sympathetic neurons that travel to the adrenal medulla, which extend directly from the spinal cord.
• 🔄 Some ganglia form an interconnected network called the sympathetic chain ganglia, located close to the spinal cord.
• 📍 Other ganglia, known as prevertebral ganglia, are situated closer to the organs they serve.
• 🔑 Neurons that travel from the spinal cord to the ganglia are called preganglionic neurons and synapse with postganglionic neurons in the ganglia.
• 🎯 Postganglionic neurons then extend to the diverse targets of the sympathetic nervous system, which are found throughout the body.
• 💉 The preganglionic neurons primarily release acetylcholine, while postganglionic cells mainly release norepinephrine, although some use acetylcholine.

Q & A

What is the sympathetic nervous system?

The sympathetic nervous system is a subdivision of the autonomic nervous system that controls automatic processes in the body, such as digestion, heart rate, and respiration.

What is the 'fight-or-flight' response associated with the sympathetic nervous system?

The 'fight-or-flight' response is a general reaction to alarming or threatening situations that involves increasing the body's ability to act, typically associated with the sympathetic nervous system's role in expending energy.

Is the sympathetic nervous system only active during 'fight-or-flight' responses?

No, the idea that the sympathetic nervous system is only active during 'fight-or-flight' responses is an oversimplification. It is also active in non-emergency responses and during times of rest.

Where do the nerves of the sympathetic nervous system originate?

The nerves of the sympathetic nervous system originate in the thoracic and lumbar regions of the spinal cord.

What is the role of sympathetic ganglia in the nervous system?

Sympathetic ganglia are clusters of neurons in the peripheral nervous system where sympathetic neurons extend from the spinal cord and synapse with other neurons.

What is the exception to the sympathetic neurons' path from the spinal cord to their targets?

The sympathetic neurons that travel to the adrenal medulla are an exception, as they extend directly from the spinal cord to the adrenal medulla, bypassing the sympathetic ganglia.

What is the sympathetic chain ganglia and where are they located?

The sympathetic chain ganglia is a network of interconnected ganglia within the sympathetic nervous system, found close to the spinal cord.

What are prevertebral ganglia and their location relative to the organs they supply?

Prevertebral ganglia are sympathetic ganglia that are located closer to the organs they supply, unlike the sympathetic chain ganglia which are closer to the spinal cord.

What is the difference between preganglionic and postganglionic neurons in the sympathetic nervous system?

Preganglionic neurons are the neurons that travel from the spinal cord to the ganglia, while postganglionic neurons are those that synapse with preganglionic neurons in the ganglia and then extend to the targets of the sympathetic nervous system.

Which neurotransmitters are primarily released by preganglionic and postganglionic neurons in the sympathetic nervous system?

Preganglionic neurons primarily release the neurotransmitter acetylcholine, while postganglionic cells primarily release norepinephrine, although some postganglionic neurons use acetylcholine as their primary neurotransmitter.

What are the diverse targets of the sympathetic nervous system throughout the body?

The targets of the sympathetic nervous system are various and include organs and tissues throughout the body, affected by the postganglionic neurons extending from the sympathetic ganglia.