1
Q
Which two reflexes are triggered by sexual stimulation, and govern ejaculation?
A
Sympathetic reflex:
- triggered by sexual stimulation
- SNS nerves (T12-L2)
Somatic reflex:
- triggered when semen enters urethra
- pudendal nerve (S2-4)
2
Q
What is the sympathetic reflex governing ejaculation?
A
- triggered by sexual stimulation
- SNS nerves (T12-L2)
3 actions:
- internal urethral orifice contracts to prevent reflux into bladder
- contraction of accessory ducts and glands fills urethra with seminal fluid
- PNS fibres release nitric oxide, which causes vasodilation of penile arterioles and engorgement of corpus cavernosum and corpus spongiosum in penis
3
Q
What is the somatic reflex governing ejaculation?
A
- triggered when semen enters urethra
- pudendal nerve (S2-4)
2 actions:
- contraction of bulbospongiosus ejects semen
- contraction of ischiocavernosus maintains erection
- muscular contractions occlude venous return from penis (and maintain erection)
4
Q
What is semen?
A
- an alkaline mixture of sperm, testicular fluid and secretions from the prostate and seminal glands
- provides a transport medium for sperm cells during ejaculation
- each ejaculation of semen contains 300-500 million sperm
5
Q
What are the components of semen?
A
- fructose (fuel source)
- prostaglandins (decrease viscosity of cervical mucous and stimulate reverse peristalsis of uterus)
- clotting factors
- antimicrobial substances
- relaxin hormone (enhances sperm motility)
6
Q
Which hormone in semen enhances sperm motility?
A
Relaxin
7
Q
What are the functions of the bulbourethral glands during sexual stimulation?
A
- paired pea size glands located inferior to prostate gland
- ducts pass through perineal membrane with urethra and open into proximal spongy urethra (in bulb of penis)
- ducts produce secretions into urethra during sexual arousal
- secretions neutralize pH of urine residue in urethra and lubricate tip of penis
