McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 2 9 Introduction to the autonomic nervous system

Brain stem and spinal cord Sympathetic

chain Nerves and ganglia

Organs

Eye

1

Lacrimal gland Parotid gland Salivary gland

2

3

4

Lungs Larynx

Heart

Stomach

Liver

Coeliac ganglion and plexus

Pancreas Adrenal gland Kidney Intestine Colon

Superior mesenteric ganglion

Inferior mesenteric ganglion and plexus

FIGURE 29.2  The autonomic nervous system. The sympathetic, or thoracolumbar, division sends relatively short preganglionic fibres to the chains of paravertebral ganglia and to certain outlying ganglia. The second cell, or postganglionic cell, sends relatively long postganglionic fibres to the organs preganglionic fibres that synapse with a second nerve cell in ganglia located close to or within the organs that are then innervated by short postganglionic fibres. it innervates. The parasympathetic, or craniosacral, division sends long

Bladder

5

Reproductive organs

Oculomotor n. Facial n. Glossopharyngeal n.

1 2 3 4 5

Vagus n. Pelvic n.

Noradrenaline synthesis and storage Noradrenaline belongs to a group of structurally related chemicals called catecholamines that also includes dopamine, serotonin and adrenaline. Noradrenaline is made by the nerve cells using tyrosine, which is obtained in the diet. Dihydroxyphenylalanine (dopa) is produced by a nerve, using tyrosine from the diet and other chemicals. With the help of the enzyme dopa decarb­ oxylase, the dopa is converted to dopamine, which in turn is converted to noradrenaline in adrenergic cells. The noradrenaline is then stored in granules or storage vesicles within the cell. These vesicles move down the nerve axon to the terminals of the axon, where they line up along the cell membrane. To be an adrenergic nerve, the nerve must contain all of the enzymes and

the production and release of thyroid hormone, which increases metabolism and the efficient use of energy. Together, all of these activities prepare the body to flee or to fight more effectively. When overstimulated, however, they can lead to system overload and a variety of disorders. Adrenergic response Sympathetic postganglionic nerves that synthesise, store and release noradrenaline are referred to as adre­ nergic nerves. Adrenergic nerves are also found within the CNS. The chromaffin cells of the adrenal medulla are also adrenergic because they synthesise, store and release noradrenaline, as well as adrenaline.