Sleep, neuronal activity and thrombotic events

Sleep stages & autonomic nervous system:

1. NREM sleep:

    1. Parasympathetic drive increases.

    2. Decline in Sympathetic drive, blood pressure, heart beat.

2. REM sleep:

    1. Profound Sympathetic nerve activity (increase).

Autonomic Nervous System, regulates involuntary physiologic processes like heart rate, blood pressure, respiration, digestion, sexual arousal etc. This is part of peripheral nervous system, comprising of Sympathetic, Parasympathetic and Enteric nervous system.

1. Sympathetic N.S.

    1. Afferent fibers -- Sensory input. 

                                                           } Central Nervous System

    2. Efferent fibers -- Motor output. }        ---->           motor pathway with 2 neuron series;

                                                                                       1. a Preganglionic neuron with a cell body in                                                                                                                         CNS.                                                                                                                                                                          

                                                                                       2. a Post ganglionic neuron with a cell body in 

                                                                                           the periphery that innervates target tissues. 

2. Parasympathetic N.S. 

    1. Afferent fibers -- Sensory input. 

                                                           } Central Nervous System

  2. Efferent fibers -- Motor output. }       ---->              1. S.N.S. activation, 

                                                                                           SNS innervates every every tissue in the body.

                                                                                           causes:

                                                                                           Elevated activity & attention.

                                                                                           "flight or fight" response,

                                                                                           b.p. & hear rate increases,

                                                                                           glycogenolysis ensues,

                                                                                           gastrointestinal peristalsis cease.

                                                                                        2. P.N.S. activation,

                                                                                            PNS innervates only the head, viscera,

                                                                                            external genitalia (smaller than SNS).

                                                                                            promotes: 

                                                                                            "rest & digest" response,

                                                                                            b.p. & heart rate lower,

                                                                                            gastrointestinal peristalsis/digestion restarts,

• Presynaptic neurons of both SNS and PNS utilize acetylcholine(ACh) as neurotransmitter.
• Postsynaptic Sympathetic neurons generally produce norepinephrine (NE) as their effector transmitter to act upon target tissue while Postsynaptic Parasympathetic neurons use ACh throughout.
• Enteric neurons use several neurotransmitters as ACh, Nitrous Oxide, Serotonin etc.

      Neurotransmitter, are chemical signals from one neuron to the next target cell, to quote a few:

• Acetylcholine is often used in Parasympathetic N.S. to have an inhibitory effect.
• Norepinephrine (Noradrenaline; neurotransmitter and a hormone as well) often works with Sympathetic N.S.to have a stimulating effect on the body.

Sexual arousals:

1  S.N.S. activation > increasing blood flow > decreasing food processing in the bowels > in turn would increase blood availability for genital engorgement.

2. P.N.S. activation > branches from Sacral plexus of Spinal nerves > arteries supplying erectile tissues. Nerves release Acetylcholine > Nitric Oxide from endothelial cells of trabecular arteries, eventually causes Nocturnal Penile tumescence. This NPT phenomena is of spinal regulation, brain or testosterone is not involved.

Sympathetic activity and REM sleep:

A research conclusion thankfully quoted here as, "REM sleep is associated with profound sympathetic activation in normal subjects, possibly linked to changes in muscle tone. The hemodynamic and sympathetic changes during REM sleep could play a part in triggering ischemic events in patients with vascular disease.

REM sleep is most manifest toward the end of sleep, before arousal. Sympathetic and hemodynamic alterations during REM sleep could conceivably initiate increased platelet aggregability, plaque rupture, or coronary vasospasm, thus acting as a triggering mechanism for thrombotic events that may present clinically only after arousal."