Session 6: Human Sexual Response

Question 1

Phases of human sexual response found in both women and men.

Answer 1

Excitement phase

Plateau phase

Orgasm phase

Resolution phase

Question 2

What stimuli causes the excitement phase in men?

Answer 2

Psychogenic stimuli

Somatogenic stimuli

Question 3

Explain the psychogenic stimuli of the excitement phase in men.

Answer 3

Looking/hearing/smelling something causing a somatic and parasympathetic response.

Question 4

Explain the somatogenic stimuli of the excitement phase in men.

Answer 4

Touching.

Causes tactile afferents of the penis to signal via the spinal reflex to cause a somatic and parasympathetic response.

Question 5

Explain the excitement phase in men.

Answer 5

Somatogenic and psychogenic stimuli feeding afferents to the somatic and parasympathetic efferents.

The somatic efferents are via the pudendal nerve.

Parasympathetic efferents are via the pelvic nerve.

The parasympathetic nerves release ACh which will bind to the M3 receptors. Along with cGMP this causes an increase in intracellular Ca2+ concentrations which causes the release of NO (nitrous oxide).

Nitrous oxide causes vascular smooth muscle relaxation and arterial and venodilation. Sinusoids within the corpora cavernosa also dilate. All of this dilation leads to an erection by subsequent increased blood flow to the corpora cavernosa against the tough tunica albuginea. This also compresses venous drainage.

This is all important in order to maintain an erection.

Question 6

Explain the plateau phase in men.

Answer 6

Minor involuntary vasocongestion

Penile erection increase slightly

A rise in heart rate

Question 7

What can the orgasm phase in men be divided into?

Answer 7

Emission and ejaculation

Question 8

Explain the emission part of the orgasm phase in men.

Answer 8

Smooth muscle contraction of the prostate, vas def and seminal vesicle.

This pushes semen into the prostatic urethra.

Question 9

Explain the ejaculation part of the orgasm phase.

Answer 9

Contraction of the glands and ducts.

Contraction of the IUS to prevent retrograde flow.

Rhythmic contraction of the muscles of the pelvic floor.

This leads to expulsion of the semen.

Question 10

Explain the resolution phase of men.

Answer 10

2 steps:

1 - Penile involution and decrease in penile erection and size. This is an absolute refractory period. During this time the cycle cannot keep going.

2 - Penis return to normal size. This is the relative refractory period. During this time it is possible to start the excitement phase again.

Question 11

Explain the differences in the human sexual response between men and women.

Answer 11

Men have an absolute refractory period

Question 12

Causes of erectile dysfunction.

Answer 12

Psychological input

Vascular disorders

Anti-hypertensives

Drugs

Neurological disorders

Tears in fibrous tissue of corpora cavernosa (Tunica albuginea)

Question 13

Explain the mucus changes produced by the cervix over the course of the menstrual cycle.

Answer 13

Oestrogen - thin and stretchy mucus

Oestrogen + progesterone - Thick, sticky and forms a plug of the cervix to prevent further sperm getting in. Also prevents pathogens to enter to protect a potential fertilisation

Question 14

Explain capacitation.

Answer 14

Further maturation of the sperm inside of the female reproductive tract.

The sperm membrane changes in order to be able to fuse with the oocyte.

Also the tail changes from a beat to a whip-like action.

Also allows acrosome reaction by the sperm.

Question 15

Fertile window of the spermatozoa.

Answer 15

Can survive for 48-72 hours

Question 16

Fertile window of oocyte

Answer 16

24 hours

Question 17

What is the fertile period?

Answer 17

Sperm deposition for up to 3 days before ovulation. Or just before ovulation

Question 18

What is the acrosome reaction?

Answer 18

The spermatozoa pushes through the corona radiata (layer of granulosa cells on the surface of the ovum)

The spermatozoa will then reach the zona pellucida and release enzymes to break down the barrier.

One sperm will penetrate and enter the cell.

The cortical reaction will pursue to prevent any other entry of sperm.

Question 19

Explain what happens after fertilisation.

Answer 19

Calcium waves allows fusion of oocyte with the sperm.

Resumption of meiosis II occurs.

Formation of the morula

Question 20

Briefly explain the morula.

Answer 20

8 cells which are totipotent

Question 21

Explain assisted reproductive technology.

Answer 21

Oocytes are fertilised in vitro until it becomes a morula of 4-8 cells.

The morula is then implanted into the uterus.

Question 22

Give another use for the morula.

Answer 22

You can extract cells without damaging the morula to look for serious heritable conditions.

Question 23

Explain the next step after the formation of the morula.

Answer 23

Formation of a blastocyst by the differentiation into an inner and outer cell mass. The blastocyst hatches out of the zona pellucida in order to be able to grow bigger and also allow implantation into the uterine wall.

Question 24

Explain the implantation.

Answer 24

Trophoblasts interact with the endometrium.

The endometrium will control the degree of invasion (this does not happen in ectopic pregnancy)