Pre and post ganglionic nerves

Pre-ganglionic and post-ganglionic nerves are two components of the autonomic nervous system, which controls involuntary bodily functions. Here are the key differences between them:

1. Location:

   - Pre-ganglionic nerves: These nerves originate in the central nervous system (CNS), specifically in the brainstem or the sacral region of the spinal cord.

   - Post-ganglionic nerves: These nerves extend from ganglia, which are small clusters of nerve cell bodies located outside the CNS.

2. Length of axon:

   - Pre-ganglionic nerves: They have relatively long axons that extend from the CNS to the ganglia, where they synapse with post-ganglionic neurons.

   - Post-ganglionic nerves: They have shorter axons that project from the ganglia to the target organs or tissues.

3. Function:

   - Pre-ganglionic nerves: Their primary function is to transmit signals from the CNS to ganglia, where they synapse with post-ganglionic neurons. These signals initiate the autonomic response.

   - Post-ganglionic nerves: These nerves relay signals from the ganglia to the effector organs (such as the heart, digestive organs, or glands), which execute the autonomic response.

4. Neurotransmitters:

   - Pre-ganglionic nerves: They typically release the neurotransmitter acetylcholine (ACh) at their synapses with post-ganglionic neurons.

   - Post-ganglionic nerves: Depending on the branch of the autonomic nervous system (sympathetic or parasympathetic), post-ganglionic nerves release different neurotransmitters. Sympathetic post-ganglionic neurons release norepinephrine (noradrenaline), while parasympathetic post-ganglionic neurons release ACh.

5. Effects on target organs:

   - Pre-ganglionic nerves: Their activity initiates the "fight or flight" (sympathetic) or "rest and digest" (parasympathetic) responses, but they don't directly affect target organs.

   - Post-ganglionic nerves: These nerves directly innervate target organs and elicit the specific autonomic responses, such as increasing heart rate (sympathetic) or promoting digestion (parasympathetic).

In summary, pre-ganglionic nerves transmit signals from the CNS to ganglia, while post-ganglionic nerves relay signals from ganglia to target organs, and they have different functions, neurotransmitters, and effects on bodily functions.