Wednesday, 5 June 2013

Parasympathetic Nervous System - brief overview

Generally involved in the rest and digest response, or other activities that occur when the body is resting.

Preganglionic neurons are usually long, postganglionic neurons are usually short, this is because the preganglionic neurons must travel from the brain and spinal cord to a ganglion that is next to or inside of an organ. The postganglionic neurons which communicate with the organ are therefore very short in comparison.

Both types of neurons typically use acetylcholine as their neurotransmitter but can also utilise neuropeptides.

Examples of sympathetic stimulation:

- Iris (eye muscle): pupil constriction

- Salivary glands: saliva production increased

- Oral / Nasal Mucosa: mucus production increased

- Heart: heart rate and force decreased

- Lungs: bronchial muscles contracted

- Stomach: peristalsis increased and gastric juice secreted as well as an increase in motility

- Small intestine: motility increased

- Large intestine: secretions and motility increased

- Liver: No change

- Kidneys: increased urine secretion

- Adrenal medulla: No change

- Bladder: wall contracted, sphincter relaxed

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