Appendix B - Sex and the nervous system Flashcards
What are the two types of neurons in the sympathetic nervous system?
Preganglionic neurons - Reside in the spinal cord and send their axons to ganglia outside the spinal cord
What is the postganglionic neurons - cell bodies lie in the ganglia and that send their axons to peripheral targets such as smooth muscle and glands
What are the five elements of the reflex loop that runs from the genitals to the spinal chord and back?
- Sensory nerve endings detect the stimulation.
- Nerves convey the sensory information to the spinal cord.
- Information is processed in the spinal cord.
- Nerves carry an output signal to the penis or clitoris.
- Vascular elements are responsible for the actual erection.
What are the unique class of nerve endings called in genitalia?
Genital end-bulbs (or genital corpuscular receptors) - Specialized nerve endings, found in the genital area, that probably detect the tactile stimulation associated with sexual activity.
What are the pudendal nerve and the pelvic nerves?
pudendal nerves Peripheral nerves supplying the external genitalia.
pelvic nerves Nerves that convey sympathetic signals from the lower spinal cord to the genitalia and other pelvic organs.
What kind of sympathetic axons release norepinephrine?
Adrenergic
What kind of sympathetic axons release acetylcholine?
Cholinergic
How are cholinergic and adrenergic fibres related to erection?
Flaccidity - Actively mantained by a continuous (tonic) flow of impulses in the adrenergic nerve fibers.
Erection - Increase in the activity of the cholinergic fibers, such as may happen during activation of the spinal reflex described above - The release of the neurotransmitters acetylcholine and nitric oxide cause the smooth muscle cells of the arterioles and the trabeculae to relax, and the sinusoids fill with blood. Whether the adrenergic input ceases during erection, or whether its influence is simply overridden by the cholinergic inputs, is not clear. With complete erection, no more blood can enter the sinusoids, and blood flow ceases. The pooled blood gradually loses its oxygen, taking on the purplish color of venous blood. This color change can be observed in the glans of the penis, which has only a thin, translucent capsule.
What is Onuf’s nucleus
A sexually dimorphic group of motor neurons
in the sacral segments of the spinal cord that innervates striated muscles associated with the penis and clitoris
What is sexual dimorphism?
An anatomical difference between the sexes
How is the activity of the locus coreuleus related to nighttime erections?
Most of the time, the locus coeruleus neurons are active; their activity then stimulates activity in the neurons of the lumbar region of the spinal cord, and this activity is relayed to the penis by the adrenergic sympathetic axons, thus keeping the penis flaccid. During REM sleep, however, the activity of the neurons in the locus coeruleus drops; this leads to a corresponding drop in adrenergic activity, shifting the balance in favor of the cholinergic sympathetic inputs to the penis, so an erection occurs.
What is the vulva?
A woman’s entire external genital area
What are the different parts of a woman’s vulva?
Mons, labia, vaginal opening and clitoris
What is the mons?
Pad of fatty tissue covered by skin and pubic hair - Immediately in front of the pubic bone
