endocrine system Flashcards
what is a gland
an organ that releases a hormone
pituitary gland
known as master gland
regulates other glands
has two lobes with separate functions (anterior and posterior)
hypothalamus
controls pituitary hormone production
secretes releasing and inhibiting hormones
links the nervous system and endocrine system
two connections: anterior lobe via special portal blood system
posterior lobe directly via neurons
what is the process of releasing a hormone
-neural signal
-hypothalamus releases CRF
-pituitary gland
-production of ACTH
-e.g cortisol released
what is CRF
corticotropin releasing factor
what is ACTH
adrenocorticotropic hormone
what is cushing’s disease, causes and symptoms
-over production of ACTH so adrenal glands over produce cortisol
-causes: tumours/growths in pituitary or adrenal glands
-symptoms: weight gain, red face, red stretch marks, poor WM and poor conc.
what is the role of the thyroid
metabolism regulation controlled by pituitary
produces TSH (thyroid stimulating hormone)
what occurs with thyroid disregulation
gigantism
-swollen hands and feet
-deepening of voice
-cog. issues
-fertility issues
what is grave’s disease
-immune system attacks thyroid gland: hyperthyroidism
-affects 1 in 200
-increased risk of heart failure/stroke
-thinning of skin, inflammation of tissue around eyes which can put pressure on optic nerve
what do the ovaries produce
oestradiol (E) and progesterone (P)
what do the testes produce and what is their role
testosterone (T)
-essential for reproduction
-controlled by pituitary-produces luteinizing hormone (LH) and follicle stimulating hormone (FSH)
what is hypogonadism and its symptoms
low levels of sex hormones
causes impaired fertility and lack of secondary sexual features
what is the name of low levels of testosterone
hypoandrogenism
what is the name for low levels of oestrogen
hypooestrogenism
testosterone and its role
-part of wider group called androgens
-both sexes but 20x more in men
-sexual behaviour, spermatogenesis, developing secondary sexual characteristics, muscle growth
what are some possible weaknesses of high testosterone levels
-suppress the immune system
-increased risk of cancer
-aggression
-may reduce parental behaviour
evidence of the role of testosterone in animals
Wallen
-castrated rats fail to show sexual behaviours but can be reinstated using implants
-anti androgens reduce male sexual behaviours
natural experiments demonstrating role of T in humans
Wang et al 2000
-hypogonadal men with reduced sexual functioning, poor mood, lower muscular strength
-wear T patch for 180 days
-sexual performance and desire increases @30 days
-increase of mood @30 days
-increase in leg press
evidence that T levels can be influenced by social cues
Midgley
-60% of those that take steroids show anticipation of sexual activity increases T levels
lab controlled experiment into T
Nave et al 2017
-T gels cause men to make rash decisions and choose obvious incorrect answer instead of thinking carefully about correct answer
oestrodiol (E) and its role
-in both sexes but 8x more in women
-sexual behaviour, secondary sexual characteristics, skin elasticity, sensitivity of brain to oxytocin
-regulates ovulation, positive bone density/strength, positive mood/wellbeing, regulates pregnancy
do E levels vary or remain constant
vary across menstrual cycle
works in conjunction with progesterone
evidence of effect of E on behaviour
Takahashi
-ovariectomised rats are not sexually receptive
-can be reinstated with large doses of E
-more effective to give small amounts of E with P (progesterone)
-E has a priming effect in hypothalamus causing lordosis (curving of spine) (Pfaff 1989)
natural experiments on women (E)
Nathorst-Boos et al 1993
-women going through menopause have decreased hormones
-women wear E patch for 90 days
-increase desire for sex and reduce pain by lubrication
-also improves sleep after 90 days (Polo Kantola 1998)
role of T in menopause
Cappelletti and Wallen found T can help increase sexual desire following menopause
what are activational effects
-immediate effects that come and go
e.g ovulation, oxytocin release during orgasm
-may cause some structural change, hippocampus can shrink in absence of some hormones (Fitch and Denenberg)
what are organisational effects
-permanent effects on structure and function of body and NS
-critical period of development e.g fetal/puberty
activational sex hormone regulation
hypothalamic pituitary gonadal axis (HPG axis)
-gonadotropin releasing hormone GnRH
-follicle stimulating hormone
-luteinizing hormone
activational sex hormone regulation in men
GnRH bursts - 2 hours
T provides negative feedback loop to hypothalamus and pituitary
activational sex hormone regulation in women
GnRH varies over 28 days as does:
-pituitary sensitivity to GnRH
-ovary sensitivity to LH/FSH
-LH and FSH crucial to ovulation
organisational effects: sex hormones
-presence of SRY gene determines male sex, this is a region of the Y chromosome
brain effects/development
-womens brains share functions bilaterally
-mens are slightly larger overall
early sex differences in behaviour study
Connellan 2000
-babies 37 hrs old
-shown face or a mobile image for 70 secs
-blind judges guess sex of baby by their observation of the image presented
- 43% boys prefer mobile image compared to 17% for girls
- 25% boys prefer face compared to 36% for girls
oxytocin (OT) and behaviour
-known as cuddle hormone
-in female prairie voles injection of OT antagonist inhibits pair bonding
-OT directly into brain = pair bonding without mating
