BIOL 121 Lecture Notes - Lecture 17: Skeletal Muscle, Preganglionic Nerve Fibers, Adrenal Medulla
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12 pairs of cranial nerves emerging from brain stem. 31 pairs of spinal nerves emerging from spinal cord. Can be further divided into efferent and afferent divisions. Most nerves contain bother afferent and efferent neurons. Autonomic nervous system can be subdivided into 2 categories. Trying to prepare the body to do things to either fight or flee. Increase oxygen and nutrient delivery to the skeletal muscle and brain, and heart. Increase blood pressure, heart rate, decrease blood flow to all essential regions. Short pre-ganglionic (lie right next to spinal cord) and long post-ganglionic neurons. Can have the whole body respond at one time. Pre-ganglionic neuron releases acetylcholine (ach), that binds to nicotinic receptors on post-ganglionic neurons. Post-ganglionic neurons release norepinephrine, binds to adrenergic receptors on target cells. Adrenal medulla is a modified post-ganglionic fiber which releases epinephrine (80%) and norepinephrine (20%) into blood instead of it releasing it to a target tissue.
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