Physiology 3120 Lecture Notes - Lecture 16: Muscarinic Acetylcholine Receptor, Adrenal Medulla, Spinothalamic Tract
11 Aug 2016
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Ans has 3 divisions: sympathetic, parasympathetic and enteric. Eg: sitting down and suddenly stand up = mechanical response of blood pooling in legs which results in 40% decrease in cardiac output. This is because blood has pooled in the legs and is not going back to the heart. Thus less blood goes to the brain and have the potential to faint. Note skeletal muscle is not part of ans. Ans controls internal envt whereas sns (skeletal muscle) controls external envt. Although there are sns components that are largely involuntary as well. Eg: making saccades/smooth pursuit since you are not driven to do them; they just happen. Another eg: stretch reflex/vestibular spinal reflex are involuntary but part of sns. Intrinsically active organs like heart that is always beating so ans influences heart to increase/decrease hr. The gut is always contracting but ans increases/decreases contractions.
