physiology Flashcards
what is a hormone?
a hormone is a chemical which is produced at one site and has an effect on another site
what happens when a hormone reaches its target tissue?
it brings about a specific effect
where are hormones produced?
hormones are produced in the hypothalamus and the pituitary gland controls the onset of puberty, sperm production and the menstrual cycle
what hormones does the pituitary gland produce?
FSH (follicle simulating hormone) - both males and females
ICSH (interstitial cell simulating hormone) - males
LH (luteinising hormone) - females
what does the hypothalamus do at the beginning of puberty?
at the beginning of puberty the hypothalamus secretes a releaser hormone whose target is the pituitary gland which then secretes hormones
what does the production of hormones from the pituitary gland do?
the release of these hormones triggers the onset sperm production in men and the menstrual cycle in women
what does FSH do at the bloodstream in the testes?
it promotes sperm production in the seminiferous tubules
what does ICSH do when it arrives in the bloodstream at the testes?
it stimulates the interstitial cells to produce the sex hormone testosterone
what does testosterone do?
testosterone stimulates sperm production in the seminiferous tubules and activates the prostate gland and seminal vesicles to produce their secretions
what is the self regulating mechanism of testosterone production?
when the concentration of testosterone increases in the bloodstream it reaches a level where it inhibits the secretion of FSH and ICSH by the pituitary gland which leads to a decrease of testosterone concentration which then triggers the pituitary gland to again make FSH and ICSH
what do the testes produce?
sperm and testosterone
what is sperm formed from and where are they formed?
sperm is formed from germline cells in tiny tubes called seminiferous tubules
what is a sperm duct?
seminiferous tubules unite together to form coiled tubes that link to the sperm duct and sperm leave to the testes through the sperm duct
what is testosterone produced by?
interstitial cells found in the tissues between semiferous tubules and passes directly into the bloodstream
what do seminal vesicles secrete?
seminal vesicles secrete a fluid rich in fructose (to provide energy) and hormonal like compound (to stimulate contractions of the female reproductive tract)
what does the prostate gland secrete?
a thin, lubricating liquid containing enzymes which help to keep the fluid at the optimum viscosity for sperm motility
what is semen?
semen is the collective name for the liquid released by males
what does semen contain?
semen contains sperm from the testes and fluid secretions from the seminal vesicles and prostate gland that maintain the mobility and viability of sperm
what is the female gamete called?
an ova (egg)
what and where are female gametes produced?
female gametes are produced in the ovaries and are produced from germline cells
what do the ovaries contain?
the ovaries contain a mature ova at several stages of production
what are ovums surrounded by?
each ovum is surrounded by. a follicle which protects it and secretes the hormones
what happens to the folicle after ovulation?
after ovulation the follicle develops into a corpus luteum
what is ovulation?
the release of the mature ovum into the oviduct during ovulation
what is. a corpus luteum?
a hormone secreting body that secretes progesterone
function of corpus luteum in gamete production in the ovaries?
the corpus luteum then secretes the hormone progesterone which causes changes in the uterus to make it more suitable for implantation of the blastocyst
what happens to the sperm during intercourse?
during sexual intercourse, the sperm are released into the vagina and move through the cervix, the uterus and into the oviducts where they may meet an ovum
what is fertilisation?
fertilisation is when the nucleus of a sperm fuses with a nucleus of an ovum
where does fertilisation occur?
oviduct
what is a fertilised ovum called?
a zygote
how long does the menstrual cycle last for?
approximately 28 days
what is mensuration indicated by?
by blood flow
what is the first day of menstruation called?
“day 1” of the menstrual cycle
what are the two phases of the menstrual cycle?
follicular phase and luteal phase
which is the first phase of the menstrual cycle
the follicular phase
which phase is the second phase of the menstrual cycle?
the luteal phase
what does FSH do in the follicular phase?
it stimulates development and maturation of a follicle
it stimulates production of oestrogen by the follicle
what does Oestrogen do in the follicular phase?
Oestrogen stimulates rapid growth of the endometrium preparing it for implantation
affects the consistency of cervical mucus making it more easily penetrated by sperm
triggers a surge in the production of LH (around day 14)
what does LH do in the follicular phase?
is the direct cause of ovulation wha
what is the hormone which is present in urine during pregnancy and is the basis of pregnancy tests?
HGC aka Human chorionic gonadotrophin
what does HGC do during the luteal phase when fertilisation has occurred?
the embryo secretes a hormone called HGC which has the same effect as LH
where is HGC secreted?
the embryo
where are sperm formed?
Sperm are formed from germline cells in tiny tubes called seminiferous tubules
what do the testes produce?
The testes produce sperm and the
hormone testosterone
what is testosterone produced by?
Testosterone is produced by interstitial cells found in the tissue between the seminiferous tubules and passes directly into the bloodstream
what does progesterone do in the luteal phase?
promotes further development and vascularisation of the endometrium preparing it for implantation if fertilisation occurs
what happens in the luteal phase when fertilisation hasnt occured?
High levels of oestrogen and progesterone during the luteal phase trigger an inhibitory effect on the pituitary gland, so concentrations of FSH and LH drop as a result and no new follicles develop at this time (This is an example of negative feedback control)
what happens when there is a lack of LH during the luteal phase?
Lack of LH leads to degeneration of the corpus luteum and therefore a subsequent drop in progesterone
what effect does drop of progesterone have in the luteal phase when fertilisation hasn’t occurred?
the drop in progesterone triggers menstruation as the endometrium can no longer be maintained
what does HGC do?
HCG maintains the corpus luteum which continues to secrete progesterone and prevents menstruation taking place.
why are men continuously fertile?
men are continuously fertile because of the negative feedback control of testosterone maintains a relatively
what can calculation of female fertile period be indicated by?
temperature rise
watery cervical mucus
temperature rise as an indicator
after the LH surge triggers ovulation , the women’s body temperature rises by about 0.5C due to progesterone action and the temperature remains elevated for the remainder of the luteal phase
how long does the fertile period lasts?
the fertile period lasts for 1-2 after the 3rd day of elevated temperature the infertile period is resumed and the unfertilised ovum disintegrates
thin watery cervical mucus as an indicator
during the fertile period, cervical mucus is thin and watery to allow sperm easier access to the oviducts
what happens to the cervical mucus after ovulation?
after ovulation the mucus increases in viscosity (due ti progesterone) showing the infertile period is resumed
stimulating ovulation use?
a women may fail to ovulate because of an underlying factor
how can ovulation can be stimulated?
- drugs that prevent negative feedback of oestrogen on FSH
- drugs that mimic the normal action of FSH and LH
- these can bring about super ovulation which can lead to multiple births
(e.g twins and triplets) or can be used to
collect ova for invert fertilisation programmes
- these can bring about super ovulation which can lead to multiple births
artificial insemination use
naturally, during sex, semen is introduced into the female reproduction system. if a man has a low sperm count artificial insemination can be used.
what is artificial insemination?
artificial insemination is the introduction of semen into the female reproductive tract by some other means than sexual intercourse
how is artificial insemination done?
it involves collecting several samples of the mans semen and freezing it until required. when ready, the semen are defrosted and released into the females cervix during her fertile period. semen from a donor can also be used in this process if the man is sterile
what is intracytoplasmic sperm injection (ISCI)
the ISCI procedure involves drawing the head of a healthy sperm into a syringe needle and then injecting it directly into an egg to bring about fertilisation
why is ntracytoplasmic sperm injection (ISCI) useful？
this procedure is useful if the mature sperm are defective or very low in number
how does ntracytoplasmic sperm injection (ISCI) work?
during the procedure the egg is held in place by a holding tool. eggs from a doner can also be used in this process if the females eggs are nonviable
what is IVF used for?
the IVF treatment is used to solve the problem of infertility caused by a blockage of the oviducts
what is IVF (in Virto fertilisation)?
In virto fertilisation means fertilisation occurring outside the body in a culture dish
steps of IVF?
- women given hormonal treatment to stimulate “super ovulation”
- surgery to remove several eggs from ovary
- eggs mixed with sperm in a culture dish of nutrient medium to allow fertilisation to occur OR a sperm may be injected directly into an egg (ICSI)
- fertilised eggs are incubated in nutrient medium for 2-3days to allow cell division to occur so they farm embryos
- two or three of the embryos are chosen and then inserted into the mothers uterus which is ready for implantation
- remaining embryos are frozen and stored in class a second attempt at implantation required
what happens before IVF？
before IVF one or two cells may be removed and tested for genetic abnormalities
pre-implantation genetic screening (PGS)
a non-specific approach that checks the embryo for single gene disorders and common chromosomal abnormalities in general
pre implantation genetic diagnosis
a specific approach to check for a single gene disorder and chromosomal abnormalities
what are PGS and PGD used to help scientists identify?
PGS and PGD are used to help scientists identify embryos which should and should not be allowed to become implanted in the mothers endometrium
what is contraception?
contraception is the intentional prevention of conception or pregnancy by natural or artificial means
what are physical methods of contraception?
physical methods which block the ability of sperm to reach an ovum
what are barriers (physical methods)?
barriers physically block to ability of sperm to reach an ovum.
examples of barriers (physical methods of contraception)
condom
diaphragm
cervical cap
sterilisation procedures in men
a vasectomy involved cutting and tying the two sperm ducts, this prevents sperm being released during sexual activity
sterilisation in women
in women, a tubal ligation involved in cutting and typing the two oviducts. this prevents eggs meeting sperm and reaching the uterus
what are pills containing a combination of hormones used for?
oral contraceptive pills normally contain synthetic progesterone and oestrogen increase in the bloodstream and mimic negative feedback control. :-
FSH and LH by the pituitary gland is inhibited
follicle maturation is inhibited
ovulation fails to occur
progesterone only pill
mini pills, injection, implants contain synthetic progesterone ti thicken the cervical mucus to reduce sperm access to the uterus
morning after pill
emergency hormonal contraception which contain high doses of progesterone and oestrogen and are taken by a women who has had unprotected sexual intercourse to prevent ovulation pr implantation
what is antenatal (before birth) screening
antenatal screening identifies the risk of an disorder so that further tests and a prenatal diagnosis can be offered
3 examples of antenatal screening?
ultrasound imaging
biochemical tests
diagnostic test
what is ultrasound imaging?
when the ultrasound scanner is held against a pregnant women’s abdomen. it picks up high frequency sounds that have bounced off the foetus. these are converted to an ultrasound image on a computer screen.
blood and urine tests
routine blood and urine tests are carried out throughout pregnancy to monitor the concentrations of marker chemicals
what could happen if a chemical was measured at the wrong time? (pregnancy tests)
could lead to a false positive/ negative result.
what is amniocentesis?
it is carried out between 14-16 weeks and involves withdrawing amniotic fluid containing foetal cells. the cells are cultured and stained and then examined under a microscope to create the karyotype and allows for chromosome abnormalities to be detected.
what is the disadvantage of amniocentesis?
there is a risk of miscarriage
what is CVS (chronic villus sampling)?
it invoices taking a sample of the placental cells using a tube inserted into the mothers reproductive tract. the cells are cultured and used for karyotyping.
what is the benefit of CVS?
it can be carried out at 8 weeks whereas amniocentesis is 14-16 weeks
what are CVS and Amniocentesis used for?
these can be used to prepare a persons karyotype which shows their complete chromosome complement arranged as homologous pairs
what are pedigree charts used for?
they can be used to analyse patterns of inheritance in genetic screening and counselling. once phenotypes of family members are known the genotype can be worked out
what are sex chromosomes?
X and Y chromosomes are called sex chromosomes and all other chromosomes are called autosomes
a geneticist can spot the following patterns in autosomal incomplete inheritance, what are these patterns?
the fully expressed form occurs relatively rarely
the partly expressed from occurs much more frequently
each sufferer of the fully expressed form has two parents who suffer from the partly expressed form
males and females are affected in approximately equal numbers
all non-sufferers are homozygous for one incompletely dominant allele
all non sufferers are homozygous for one incompletely dominant allele
all sufferers of the partly expressed form are heterozygous for the alleles
sex linked recessive traits patterns
a geneticist can spot the following patterns in sex linked recessive inheritance-
many males are effected than females
none of the sons of an affected male show the trait
some grandsons of the affecred male show the trait
all sufferers of the trait are homozygous recessive
non-sufferers are homozygous dominant or heterozygous carrier males
when does diagnostic testing for metabolic disorders occur?
diagnostic testing for metabolic disorder occurs when the baby is just a few days old
what happens to new born babies (postnatal screening)
in the UK all new born babies are screened for PKU (phenylketonuria) by having their blood tested for the presence of excess phenylalanine
what is PKU?
PKU sufferers have incurred a substitution mutation meaning that the enzyme that converts phenylalanine to tyrosine is non-functional (therefore causing excessive phenylalanine levels)
how is PKU treated?
PKU sufferers are then put on a restricted diet to prevent mental deficiency and other adverse effects
antinatel and postnatael meaning?
before birth and after birth
what does FSH do in the testes?
promotes sperm production
what does progesterone promote
progesterone promotes vascularisation of the endometrium ready to accept a blastocyst if fertilisation has occurred
