In: Anatomy and Physiology
Match the following. Use each answer once.
Secreted by preganglionic parasympathetic fibers.
Secreted by most postganglionic sympathetic fibers.
Connective tissue sheath surrounding the myelin sheath of a neuron
The end of the spinal cord
A. Edoneurium
B. Conus medullaris
C. Norepinephrine (NE)
D. Acetylcholine (ACh)
1. Secreted by preganglionic parasympathetic fibres- Acetylcholine (ACh).
In the autonomic nervous system, fibres from CNS to ganglion are known as preganglionic fibres. All preganglionic fibres, whether they are sympathetic or parasympathetic secrete acetylcholine as neurotransmitter.
2. Secreted by most postganglionic sympathetic fibres- Norepinephrine (NE)
In the autonomic nervous system, fibres from the ganglion to effector organ are called postganglionic fibres. These are directly responsible for changes in the activity of target organ via biochemical modulation and neurotransmitter release. In sympathetic system, the postganglionic fibres all all organs except sweat glands secrete noradrenaline. Therefore it is called adrenergic system.
3. Connective tissue sheath Sorrounding the myelin - Endoneurium
Endoneurium is a layer of delicate connective tissue around the myelin sheath of each myelinated nerve fibre in the peripheral nervous system. It's component cells are called endoneurial cells.
4. The end of spinal cord- Conus medullaris
The most distal bulbous part of spinal cord is called conus medullaris. It is tapered and occurs near lumbar vertebral L1 and L2 , occasionally lower.