Autonomic Nervous System Flashcards
What are the 5 main functions of the autonomic nervous system?
- Maintenance of homeostasis
- Contraction and relaxation of smooth muscle
- All exocrine and some endocrine secretions
- Heart rate and contraction
- Metabolism
Define the 2 divisions of the ANS
Sympathetic Nervous System
- Activity increases “stress” response
- “fight or flight”
Parasympathetic Nervous System
- Activity dominant during rest
- “Rest and digest”
Identify and describe the anatomical organisation of the parasympathetic and sympathetic nervous systems.
Top and Bottom of spinal cord is Parasympathetic.
Middle is Sympathetic.
Describe the neurotransmitter involved in autonomic transmission and corresponding receptors.
Acetylcholine (Transmitter)
- Quaternary amines (aka choline esters)
Muscarinic receptors (mAChR)
- Selective agonist is muscarine
- G-protein coupled receptors (metabotropic)
Nicotinic receptors (nAChR)
- Selective agonist is nicotine
- Ligand-gated ion channels (ionotropic)
What are the 4 ANS receptor sites in the body and what are their actions?
a3B4 = autonomic ganglia (increased Na+ permeability) = excitatory M1 = neural = excitatory M2 = cardiac = inhibitory M3 = glandular/smooth muscle = excitatory
Give examples of physiological responses that occur after activation of the Parasympathetic and Sympathetic nervous systems.
Activation of mAChR’s in the PSNS
- Pupillae constrictor muscle contraction
- Lacrimal and salivary gland secretion
- Detrusor muscle contraction/sphincter muscle
- Cardiac muscle relaxation
- Gastric acid secretion
- GIT muscle contraction
Activation of adrenergic receptors in the SNS
- Relating to nerve cells that use adrenaline (epinephrine) or noradrenaline (norepinephrine) as a neurotransmitter.
- Radial muscle contraction => mydriasis
- Detrusor muscle relaxation/sphincter muscle contraction
- Cardiac muscle contraction
- Bronchial smooth muscle relaxation
- Vascular smooth muscle contraction
- GIT muscle relaxation
