Lecture 22: The Autonomic Nervous System Flashcards
what is the organisation of the nervous system?
nervous system branches into CNS and PNS, PNS is divided into sensory and motor division, motor division is split into somatic nervous system and autonomic nervous system, automatic nervous system is split into sympathetic nervous system and parasympathetic nervous system.
purpose of somatic nervous system?
voluntary movement, innervation and activation of skeletal muscle
purpose of autonomic nervous system?
involuntary functions, innervation of organs, glands, smooth muscle. split into sympathetic and parasympathetic nervous systems.
what things does the autonomic nervous system regulate?
maintenance of homeostasis, regulating body temp, cardiovascular activity, respiratory functions, digestive functions.
what are the two branches of the autonomic nervous system and function?
sympathetic nervous system; fight or flight, prepares the body for action
parasympathetic nervous system; rest and digest, relaxes the body
effects of sympathetic and parasympathetic nervous system?
sympathetic; adrenaline increase, increased heart rate, dry mouth, cold, sweaty skin, dilated pupils
parasympathetic; lower blood pressure, heart rate and respiratory rates, increased gastrointestinal tract activity, glucose is taken up into cells, pupils constricted for close vision
what are the major neurotransmitters of the autonomic nervous system, how they are released and purpose?
acetylcholine and noradrenaline. acetylcholine is released by all ANS preganglionic axons and all parasympathetic postganglionic axons. whereas, noradrenaline is released by all sympathetic postganglionic axons, except those at sweat glands.
what are the two acetylcholine receptors?
- nicotinic receptors; found on all postganglionic neurons. e.g.
- muscarinic receptors; g protein coupled receptors. e.g. binding of this receptor to the heart to slow down heart rate
what are the two classes of adrenergic receptors?
noradrenaline and adrenaline act on adrenergic receptors. the two major classes that respond to these hormones is;
- alpha adrenceptors
- beta adrenoceptors
what is some examples of ANS receptors being used for drug (medicinal) purposes?
beta blockers block receptors slow the heart rate down and alleviate bodily feelings of anxiety, muscarinic receptor inactivating drugs act on the gut to reduce feelings of nausea and vomiting.
what is sympathetic and parasympathetic tone?
occurs due to action potentials continually firing down axons of both divisions. there is usually one division that predominates which is controlled by the brain.
parasympathetic tone: both divisions control heart rate, parasympathetic NS decreases heart rate, sympathetic NS increases heart rate and dominates at rest.
sympathetic tone: blood vessels are only innervated by the sympathetic NS, basal activity causes partial constriction of vessels and can constrict or dilate by varying rate of firing in sympathetic NS
what controls the autonomic NS?
controlled by the brainstem and hypothalamus (via brainstem and hormonally)
