00:01
So now let's discuss
the male sexual response.
00:06
We start with the first E of two.
00:09
That's erection.
00:11
An erection is an enlargement,
and stiffening of the penis.
00:16
In an erection, the arterioles
are normally constricted.
00:21
But during sexual excitement,
the central nervous system
activates parasympathetic neurons,
which released the chemical
nitric oxide.
00:31
Nitric oxide is a neurotransmitter
that causes the relaxation of
local vascular smooth muscles.
00:40
When the smooth muscles
are relaxed,
the arterioles begin to dilate
or open up.
00:47
The corpus cavernosa of the penis
then expands and retards
venous drainage
leading to an engorgement
of the erectile tissue with blood
and an enlargement
and stiffening of the penis.
01:02
This is initiated by sexual stimuli
such as touch,
mechanical stimulation,
erotic sights, sounds, or smells.
01:13
And erection
can be induced or inhibited
by emotions or
higher mental activity.
01:21
And longitudinal and circular
collagen fibers around the penis
can prevent the kinking and buckling
of the erect penis.
01:31
Also, the corpus spongiosum
keeps the urethra open.
01:37
The second E in the
male sexual response is ejaculation.
01:42
Ejaculation is the
propulsion of semen
from the male duct system.
01:49
This is caused by a
sympathetic spinal reflex.
01:53
During this process,
the bladder sphincter muscles
will constrict.
01:58
This will prevent
the explosion of urine
at the same time
that ejaculation occurs.
02:05
Also the ducts and accessory glands
are going to contract
in order to empty their contents.
02:13
The bulbospongiosus muscles
are going to undergo
a rapid series of contractions
that cause the expulsion of semen
at about 500 centimeters per second
or 11 miles per hour.
02:28
At this point
when the contractions occur,
this causes ejaculation.