BIOL 2P94 Lecture Notes - Lecture 7: Nicotinic Acetylcholine Receptor, Adrenal Medulla, Postganglionic Nerve Fibers

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Published on 4 Feb 2013
Outline of Lecture 72 (03-31 A; Schramm)
Peripheral Autonomic Nervous System
I. The sympathetic NS is distributed to more tissues than is the parasympathethic NS
- The parasympathethic NS innervates glands and some thoracic and abdominal viscera
- The parasympathethic NS is noticeably absent from all limb and body wall vasculature
II. The symp. and parasymp. NSs tend to have opposite effects on dually-innervated effector tissues
- Analogous to muscle agonist/antagonist pairs, symp/parasymp are reciprocally coordinated
- Example of symp/parasymp effects on cardiac pacemaker cells
- Parasymp
- Vagal (parasymp) stimulation immediately depol. rate and hyperpol. the cell
- Mediated by ACh: Na and Ca influx and K outflux
- Symp
- Symp stimulation causes in depol. rate and heart rate after a few seconds
- Mediated by NE: Na and Ca influx only
III. Actions of autonomic nxt are conferred by nature and location of the nxt’s receptors
- Cholinergic receptors
- There are 5 types of muscarinic receptors, including M1 (ganglia), M2 (heart), M3 (smooth
muscle, secretory glands)
- There are nicotinic receptors as well (ganglia, adrenal medulla)
- Adrenergic receptors
- α receptors cause contraction of vascular smooth muscle via PLC/DAG/Ca pathway
- There are at least 3 types of α receptors
- β receptors cause channels to open via AC pathway
- β1 is found in heart, β2 in variety of tissues, β3 in adipose tissue
IV. The morphology of autonomic endings on effectors widely within and between tissues, some of which
have functional differences
V. Peptides are often colocalized with conventional autonomic nxt, with differential release of these nxt’s
- There is good evidence that the colocalized peptide is functional
- Peptide release may be triggered by high frequencies of nerve activity
VI. Sympathetic ganglia perform a variety of information processing functions
- The pre- to post-ganglionic connections involves both convergence and divergence, and this can
give rise to subtle patterns of activity
VII. Peripheral and central pathways mediating visceral afferent processing strongly resemble those
mediating somatic processing
- Afferent processing can be complex: e.g. can be detect rates of change instead of just absolute
- Both somatic and visceral afferents end on the same second order neuron, which is the
neurological basis of referred pain
- There is a visceral spinal reflex pathway, but it is never active due to descending inhibition
Summary of major ideas
- See p. 1 of notes (same as headings of roman numerals in this outline)
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