Male Reproduction 13

Question 1

What is the role of the human male?

Answer 1

The male human has two major roles with respect the the physiology of reproduction
– manufacturing of sperm (Spermatogenesis)
– disperse sperm for fertilization

Question 2

What factors influence the release of GnRH?

Answer 2

Negative feedback

Sleep/wake cycle

Temperature on the Testes

Stress

Hormones

These influence frequency and amplitude

Question 3

What is the structure of GnRH?

Answer 3

10 AA peptide
• Released in median eminence of hypothalamus
• Secreted for a few minutes every 1-3 hours
– pulsatile

Question 4

What is the mechanism of action of GnRH on the anterior pituitary?

Answer 4

Increases IP3+ DAG which stimulates PKC and thus increases Ca2+ releases vesicles containing LH/FSH via exocytosis

Also increases LH & FSH synthesis

Question 5

What is the mechanism of action LH on testes?

Answer 5

LH increases cAMP via PKA and Increases DNA transcription

This causes cholesterol to be used for testosterone synthesis

Question 6

What is the mechanism of action of FSH on Testes?

Answer 6

FSH increases cAMP and via PKA increases DNA transcription

This increases ABP, Aromatase, and ABP growth factors

Question 7

What does testosterone do at the target tissues?

Answer 7

Dihydrotestosterone binds to receptor to modulate gene expression to increase protein expression

Question 8

What are the actions of testosterone on adults?

Answer 8

 size of reproductive organs
- promotes spermatogenesis
- ? sex drive
- development of 20
sexual characteristics

• promotes long bone fusion
•  BMR
• ↑ in RBC’s mass

Question 9

What secondary sex characteristics in adult males are due to testosterone?

Answer 9

• Effects voice
• thickens skin &
•  sebaceous secretions
  leading to acne
• male pattern of baldness
• increase  body hair on face, chest,
  pubis, linea alba & other portions
• deposition of protein
• muscle mass
• strength & size
  of bones

Question 10

What form does testosterone travel in?

Answer 10

Travels bound (~97%) to
– Sex-hormone binding globulin – Albumin
• Free testosterone is converted into a more active form by 5 α reductase dihydrotestosterone which is more potent then testosterone
• It is broken down in the liver & excreted by the kidneys

Question 11

How is GnRH negatively inhibited?

Answer 11

Testosterone from leydig cell inhibits anterior pituitary and hypothalamus

Some testosterone converted into estrogens

Inhibin from Sertoli cells inhibits anterior pituitary

Question 12

Summarize the male sex act

Answer 12

The male must have an erection and ejaculate in order to complete the sex act

Question 13

Explain the impact of psychological/ physical stimuli of an erection

Answer 13

Increase in parasympathetic(via NO and/or ACh) and decrease in sympathetic activity
This leads to vasodilation and erection

Question 14

What is erectile dysfunction/ impotence?

Answer 14

the inability to have complete erection or have a brief one.
Priapism is sustained erection.

Increased parasympathetic activity( by viagra, cialis, and levitra )via NO &/or they increase levels of cGMP by inhibiting its degradation

This allows for an erection to occur

Question 15

Summarize an ejaculation

Answer 15

Emission Genital duct / accessory organ contraction (sympathetic stimulation)
– Vas deferens, prostate, seminal vesicles
– Mix with mucus in urethra producing semen

• Expulsion
– Semen expelled by rhythmic skeletal muscle contraction at base of penis

Question 16

What are the causes of hypogonadism ?

Answer 16

Non-functionaltestesinfetus
– Lead to development of female sex organs
• loss of Testes pre-puberty
– Maintain infantile sex organs and characteristics
– Bones less strong but longer
– Maybe taller than other men (eunuchs)

Loss of testes post-puberty
– Slight decrease in size of sexual organs – Slight increase in voice pitch
– Loss of bone and protein build up
– Slight loss of sexual desire
– Less easy for erection
– Ejaculation rarely occurs

Question 17

What is Adiposogenital syndrome?

Answer 17

Inability of hypothalamus to secrete enough GnRH

– Also effects feeding center of H/T • Get obesity and hypogonadism

Question 18

What is infertility?

Answer 18

Sperm count
– Should have ~ 120 million sperm / ml of semen
– If below 20 million / ml are said to be infertile
• Sperm morphology and motility – Abnormal shape of sperm
– Lack of motility