RRoman

Actually, I heared that morning wood is caused by a full bladder pressing on some nerves or something.

Totalitarianist

I have never experienced this.

Amit Misra

doghouse wrote:
Are we getting into proximate and ultimate causes from the simple pleasures of water-relief?
In so far as a causal relationship can be established, I offer the following observations:
1. "Andropause" as defined by deLignires in circa 1995, correlates with reduced pulse amplitude and frequency of GnRH pulses.
2. Peri-andropausal males have fewer early-morning erections.
3. Early-morning erections are first experienced around puberty, when the hypothalamus-pituitary-testes hormonal axis begins to settle down to its biorhythm.
4. We have parasympathetic outflows, REM sleep and muscle tones in pre-pubertal life (ditto full urinary bladders if I remember my childhood correctly!).
More to go, but let me save ammo!
amit

doghouse

Fewer, but they still have them. See below.



This is incorrect. Halverson, in 1940, documented nocturnal erections in infants. Nocturnal erections peak at puberty, but occur in healthy males of all ages (Schiavi).

Halverson HM. Genital and sphincter behavior of the male infant. J Gen Psychol 1940;56:95.
Schiavi RC, et al. Hormones and nocturnal penile tumescence in healthy aging men. Arch Sex Behav 1993;22:207

All erections are primarily neurovascular events. Parasympathetic input (via the 2-4 sacral segments, pelvic nerves, pelvic plexus, and finally the cavernous nerve) causes release of NO from vascular endothelium of the penis. This initiates the vascular events leading to tumescence. Stimulation of the pelvic plexus and cavernous nerves causes tumescence. Stimulation of the sympathetic trunk causes detumescence. This clearly implies that sacral parasympathetic input is responsible for erection.
For review, see Tue TF. Physiology of penile erection and pathophysiology of erectile dysfunction and priprism. In Walsh et al (Eds) Campbell’s Urology 8th ed. Philadelphia: Saunders 2002.

These erections don’t occur just in the morning. Nocturnal erections occur throughout sleep, with over 80% occurring during REM sleep. The average adult male has 3-5 episodes through the night. You only recognize the episode in the morning because you wake up.
Karacan et al. Erection cycle during sleep is related to dream anxiety. Arch Gen Psychiatry 1966;15:183.

Now, I agree that androgens influence nocturnal erections. Hypogonadal men have less have nocturnal penile erections and hormone replacement therapy can correct this. But hypogonadal patients can still have nocturnal erections (93% in one study:KadIolu PI, et al. Penile hemodynamics in hypogonadal men with micropenis. Urology 2003;61:426-30)

On the other hand, damage to the pelvic plexus or cavernous nerves (aggressive prostate surgery, for example) will abolish nocturnal erections, despite normal hormonal levels. This clearly indicates that nocturnal erections are absolutely dependent on parasympathetic innervation. (for ref. see Tue)

If you are arguing that hormonal fluxes are the direct cause of nocturnal erections, then you will need to show evidence that hormone levels fluctuate coinciding with the 3-5 episodes per night of penile erections.


I'm interested in your response

Craig

I find that the morning wood occurs more often when I really have to pee (as in a drank a lot of beer/water/etc the night before). This is an unfortunate cause-effect because as we all know this condition prevents urination which makes for an uncomfortable (and sometimes comical) morning.

NialScorva

I hate having to do a hand stand in order to piss.

ps418

Doghouse,

Im not sure what you're arguing. If you want to be picky about it, lots of the things that hormones do, they do not do directly, but by acting on nerve cells. There is no contradiction necessarily in saying that something is caused by hormones and is a neural 'event', since neural events can and often are caused by release of hormones (e.g. fight or flight response).

Hypogonal men still have androgens, though at much low levels. Individuals with no androgens probably could not experience erections at all. I remember reading that animals castrated at birth do not experience any erections, though I dont have a reference for this.

Patrick

PopeInTheWoods

[Beavis and Butthead]Heh, heh. He said expound.[/Beavis and Butthead]

doghouse

I like to think of it as "discussing" not "arguing". And I don't necessarily want to be picky. Just accurate. If you read the previous posts, you will see that my response was originally in reference to:

My point is that early morning erections are not caused by this morning surge of hormones. They are associated with REM sleep, independent of any hormone surge. I hope that's more clear.

Amit Misra

The PopeInThe Woods deserves kudos for detecting the Freudian slip. Now, if I may pound away...
Doghouse's demand for accuracy is well taken. So also his sugestion that I should be able to demonstrate significant cross-correlation between nocturnal penile tumescence (NPT) and blood levels of GNRH (impossible with technology available) LH and testosterone (T).
Veldhuis' seminal paper (J Clin Endocrinol Metab 65 (5): 929-941 1987) describes the temporal coupling of LH and T. These authors document an inter-pulse interval of 112+/-14 minutes between 2 pulses of T. Given a sleep period of 8 h (480 min), there should be 4.29 pulses during this period.
Hunch: there are 4 to 5 episodes of NPT. If someone funds me and a clinician to stick canulae into healthy adult males, draw blood every 10 minutes and do radioimmunoassays of T, hooking up the poor guy's penis to the chart recorder thing that keep track of NPT and trying to establish whether NPT and T pulse maxima cross-correlate with NPT...we'll be able to claim cross correlation (or lack thereof) and not cause.
Doghouse wins the entirely respectable reductionist stakes, because the basis of his argument is the molecular event of nitric oxide release inducing erections.
(not to mention the huge popularity of sildenafil) .
I could nit-pick with Doghouse: the adrenals are a significant source of T (in hypogonadal/agonadal males, females and children). Childhood erections do not have periodicity. Smokers with intact hormonal axes are not so 'hard' to come by...
Let it pass. Erections are "caused" by NO-induced vascular tone, which is caused by parasympathetic input, which is influenced by hormones, but is amenable to extra-hormonal induction...that Jack built.
What about the PMCS, though? I still get it, despite waning tumescence at any time of day or night?
amit