Block C Flashcards
what are the two main types of hormone
chemically- peptide vs steroid
functionally- short-term vs long-term regulation of function
what are peptide hormones
two amino acid residue molecules joined by disulphide bridges. rapid onset and offset of action, secret in bursts when requires. short term regulation, secreted when needed
example of steroid hormones
cortisol and testosterone
example of steroid-like hormones
thyroxine
what do pituitary glands influence
the thyroid which produces steroid-like hormone thyroxine, adrenal cortex- which produces steroid hormone cortisol, gonads- which produce sex hormones
thyrotrophin path from pituitary gland
thyrotropin -> thyroid -> thyroxine
corticotrophin path from pituitary gland
corticotrophin -> adrenal cortex -> cortisol
gonadotrophin path from pituitary gland
gonadotrophin -> gonads -> sex hormones
growth hormone path from pituitary gland
growth hormone -> liver -> IGF-1
where is insulin produced
pancreas
what do growth hormones effect
growth, calcium ion and phosphate retention, increased protein synthesis, increased blood glucose, increased circulating free fatty acids
steps in the growth of bones
production of cartilage by chondrocytes pf epiphyseal plate
conversion of cartilage to bone at shaft edge of plate
epiphyseal plate becomes converted to bone
then growth stops at this point
what happens when growth hormones go to accelerated lipolysis
increased circulating free fatty acids, resulting in reduced tissue glucose uptake
what happens if growth hormone deficiency occurs before epiphyseal closure
dwarfism
what happens if there is growth hormone excess
if its before growth cessation -> gigantism
if after growth cessation -> acromegaly
what do thyroids secrete
thyroxine and tridothyronine
which influence activity of almost every body system -> required for synthesis of various key enzymes involved in cellular functions
where is the thyroid located
between larynx and trachea
action of thyroid hormones
influence activity of almost every body system -> required for synthesis of various key enzymes involved in cellular functions
what are required for synthesis of various key enzymes involved in cellular functions
cardiac sarcoplasmic ca2+-ATPase, Na-K ATPase, glyceraldehyde 3-phosphate dehydrogenase, beta-adrenoceptors, enzymes involved in fatty acid synthesis
consequences of thyroid hormone deficiency
marked reduction in metabolic rate of tissues, reduced function of most organ systems
what does thyroid deficiency in newborns lead to
congenital hypothyroidism (cretinism) -> impaired growth and development, mental retardation
adults with congenital hypothyroidism
severe mental retardation, dwarfism, impaired sexual development
consequences of thyroid hormone excess
marked increase in metabolic rate of tissues, increased function of most organ systems
structure of testes
interstitial cells, seminiferous epithelium, seminiferous tubules
function of testes
gametogenesis- spermatozoa
endocrine- androgens, oestrogens, inhibin
sertoli cells
nourish sperm, phagocytosis of defective sperm
paracrine function of Sertoli cells
growth factors; androgen binding protein
endocrine function of Sertoli cells
inhibin; oestrogens; MIF (AMF- anti mullerian factor)
barrier function of Sertoli cells
blood/seminiferous epithelium
what are the requirements for spermatogenisis
optimal temperature, action of various hormones
why are scrotum adapted to lose heat
large surface area, abundant sweat glands
how do testes develop
intra- abdominally
what happens if testes don’t descend into the scrotum before birth
cryptorchidism which leads to sterility
what does the failure of foetal testis lead to
no androgen secretion which leads to external genitalia develop along female lines
reproductive processes in females
early oogenesis occurs in foetus (in contrast to spermatogenesis)
cyclical
- lower animals- oestrous cycle
-human and higher primates- menstrual cycle
halt after menopause
what is the length of the menstrual cycle
average human cycle is 28.1 days (normal range is 26-35 days)
menstrual cycle phases
menstrual phase day 1-5
follicular phase day 5-14
ovulation at day 14
luteal phase day 14-28
ovarian events
follicle development
ovulation
corpus luteum development
uterine events
endometrium
cervix
motility
oogenesis
occurs during intrauterine development in the female foetus
at birth there are 2-4 million primary oocytes- arrested in meiosis
by puberty around 400,000
what type of oocyte during intra-uterine development
oogonium–> 1 degree oocyte (46 chromosomes)
what type of oocyte at time of ovulation
2 degree oocyte (23 chromosomes)
what happens during the menstrual phase
spiral arteries constrict then dilate, inner endometrium becomes ischaemic and tissue dies, blood and necrotic tissue shed via vagina
changes in cervix
thin, watery secretion around time of ovulation allows sperm penetration
changes in uterine motility
uterine peristaltic contractions occur
-movement in follicular phase is from cervix towards Fallopian tubes
-contractions increase as follicular phase progresses
-contractions increase during menstrual phase
hormonal control in follicular phase
oestrogen–> endometrial development, cervical mucus, contractions increase
hormonal control in luteal phase
progesterone–> gland development + secretion, cervical mucus, contractions decrease
hormonal control in menstrual phase
reduced levels of oestrogen and progesterone–> constriction of spiral arteries, endometrial shedding
