Darkthorn’s Blog

- fast response to perturbation via nerves

- pervasive into glands, smooth muscle, heart, eyes, sex organs

- flexible, two divisions in most organs, with more than one neurotransmitter involved

- function of maintaining homeostasis – sympathetic or parasympathetic

- cortex, limbic and thalamus also involved in ANS

Sympathetic

- ‘flight or fight’

- division from preganglionic cell bodies and axonal output

- modulated from higher senses

- ionotropic – ATP

- metabotropic – extra juctional (ATP + peptides)

- noradrenaline (norepinephrine) – receptor a1 (constriction), a2, B (relaxation)

- precursor put in vesicle, then NA is synthesized

- uptake I & II (blocked by cocaine)

- COMT – methylates for a contraction

- MAO – de-amination for B relaxation

- ATP cotransmission

- acts on purinergic receptors

- junctional and extra junctional

Parasympathetic

- ‘rest and digest’

- division from preganglionic cell bodies and axonal output

- brainstem – tears/salivary glands

- metabotropic

- nitric oxide

- very lipid soluble, not stored in vesicles

- synthesized on demand, signaled by influx of cytoplasmic calcium

- powerful inhibitor of smooth muscle contraction

- increase in Ca2+ activates NOS

- synthesizes NO from L-arginine

- NO acts on guanylyl cyclase to reduce smooth muscle Ca2+

- peptides

- acetylcholine

- 5 musacinic receptors

- Ach-ase removes from junction

- Actropene as blocker

- sensory nerves – thin, unmylinated axons (C fibres) and large AS fibres, run the same nerve trunk as efferents in periphery to terminate in the dorsal horn of the spinal cord

- main input to NTS and thalamus to communicate with other neurons

- brainstem outflow to cardiovascular/respiratory/mictunition centers, vagal (parasympathetic) outflow in medulla, rostral ventricular medulla and from CUCM to spinal cord

- NTS – nucleus tractus solitaries – receives information

- PVN – paraventricular nucleus – part of hypothalamus

- LC – locus ceruleus – distributes information

- RULM – rostral ventrolateral medulla – collects information

- CULM – caudal ventrolateral medulla – major output control

- input from – sensory afferent nerves, brainstem, spinal cord

- travels to brain – spinothelamic tract, thalamus

- goes to appropriate center

- output from center – down spinal cord

autonomic ganglia

- meeting place of neuron 1 and neuron 2

- parasympathetic ganglia – embedded in organs

- sympathetic ganglia – chain of beads down each side of spinal cord or in abdominal cavity

- acetylcholine and nicotinic ionotropic receptors

postganglionic neuron

- slow, but divided and branched within tissue

- swellings (varicosities = bouton) contain neurotransmitter

- called a junction, as is coordinating with non-neuronal tissues

Flexibility

- SNS and PNS functionally antagonistic

- more than one transmitter

- more than one receptor for each transmitter

Lock and Key

- Lock – receptors, uptake pumps and degrading enzymes

- Key – neurotransmitter and agonist drugs, blocking drugs (antagonists)

Adrenal medulla – become autonomic ganglion cells and adrenal medullary cells

Energy – white and brown fat levels, leptin signals homeostatic levels

Cardiovascular – response by upper and lower limbs to cause pain, heart rate increases and blood vessels constrict.

- SNS in heart – signals need for more blood when heart works harder

- Heat stroke – when temperature levels rise dangerously SNS activates

- Cutanaeous vasoconstriction, stop sweating, blood cooling stops

Human Sexual Response

- a balance of PNS and SNS

- penile artery – Nitric Oxide – vasodilator (PNS)

- noradrenaline – vasoconstrictor (SNS)

- vas deferens – noradenaline – slow contraction (SNS)

- ATP – fast contraction (SNS)

- Sympathetic – contracts tubes, constricts arteries (ejaculation)

- Parasympathetic – dilates penile arteries (erection)