Session 6: Human Sexual Response Flashcards
Phases of human sexual response found in both women and men.
Excitement phase
Plateau phase
Orgasm phase
Resolution phase
What stimuli causes the excitement phase in men?
Psychogenic stimuli
Somatogenic stimuli
Explain the psychogenic stimuli of the excitement phase in men.
Looking/hearing/smelling something causing a somatic and parasympathetic response.
Explain the somatogenic stimuli of the excitement phase in men.
Touching.
Causes tactile afferents of the penis to signal via the spinal reflex to cause a somatic and parasympathetic response.
Explain the excitement phase in men.
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.
Explain the plateau phase in men.
Minor involuntary vasocongestion
Penile erection increase slightly
A rise in heart rate
What can the orgasm phase in men be divided into?
Emission and ejaculation
Explain the emission part of the orgasm phase in men.
Smooth muscle contraction of the prostate, vas def and seminal vesicle.
This pushes semen into the prostatic urethra.
Explain the ejaculation part of the orgasm phase.
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.
Explain the resolution phase of men.
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.
Explain the differences in the human sexual response between men and women.
Men have an absolute refractory period
Causes of erectile dysfunction.
Psychological input
Vascular disorders
Anti-hypertensives
Drugs
Neurological disorders
Tears in fibrous tissue of corpora cavernosa (Tunica albuginea)
Explain the mucus changes produced by the cervix over the course of the menstrual cycle.
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
Explain capacitation.
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.
Fertile window of the spermatozoa.
Can survive for 48-72 hours
Fertile window of oocyte
24 hours
What is the fertile period?
Sperm deposition for up to 3 days before ovulation. Or just before ovulation
What is the acrosome reaction?
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.
Explain what happens after fertilisation.
Calcium waves allows fusion of oocyte with the sperm.
Resumption of meiosis II occurs.
Formation of the morula
Briefly explain the morula.
8 cells which are totipotent
Explain assisted reproductive technology.
Oocytes are fertilised in vitro until it becomes a morula of 4-8 cells.
The morula is then implanted into the uterus.
Give another use for the morula.
You can extract cells without damaging the morula to look for serious heritable conditions.
Explain the next step after the formation of the morula.
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.
Explain the implantation.
Trophoblasts interact with the endometrium.
The endometrium will control the degree of invasion (this does not happen in ectopic pregnancy)
