6.6 Flashcards
key endocrine glands
- pineal gland
- pituitary gland
- thyroid gland
- thymus
- adrenal gland
- pancreas
- ovary
- testes
endocrine glands (definition)
- glands which produce and secrete hormones directly into the blood, carried to the target tissues
What hormones regulate blood glucose levels?
pancreas hormones:
- insulin
- glucagon
secreted directly into the blood from: islets of Lagerhans
blood glucose set point
~ 5mmol/L
If glucose lvls drop:
- pancreas detects drop
- α cells secrete glucagon hormone
- stimulates liver to convert glycogen into glucose and its release into the blood
- blood glucose increases to normal
If glucose lvls rise:
- pancreas detects rise
- β cells secrete insulin hormone
- liver is stimulated to convert glucose into glycogen
- stimulates uptake of glucose by skeletal and muscle tissues
- blood glucose drops to normal
diabetes definition
- consistency elevated blood glucose levels
symptoms of diabetes
- constant urination
- constant thirst
- tired
- craves sugar
- glucose in urine
complications of diabetes
- damages tissues and their proteins
- prevents water reabsorption in kidneys –> increase in volume of urine and body dehydration
type 1 diabetes (early onset) (deinfition/cause)
- cannot produce enough insulin
- autoimmune disease (body’s natural defence system cannot tell the difference between own cells and foreign cells)
- destruction of β cells by immune system
type 1 diabetes (early onset) treatment
- testing blood glucose levels regularly and injecting insulin when too high
- implant devices to release insulin
- stem cell treatment to create new β cells
type 2 diabetes (late onset) (definition/causes)
- cannot respond to insulin
- lack of insulin receptors or glucose transporters on target cells
- can be caused by sugary or fatty diets, prolonged obesity, genetic factors that affect metabolism
type 2 diabetes (late onset) treatment
- adjusting diet
- frequent, smaller meals
- avoid sugary foods
- eat foods with low glycemic index (foods which are digested more slowly and less likely to increase blood sugar lvls)
- high fibre foods
- exercise
more hormones produced by endocrine glands
- thyroxin (produced by thyroid gland)
- leptin (produced by adipose cells)
- melatonin (produced by pineal gland in the darkness)
thyroxin
- targets most body cells (liver, muscle, brain)
- increases metabolic rate/rate of protein synthesis
- increases heat production when body temp. is low
deficiency results in:
- tired/lack of energy
- forgetfulness
- depression
- decrease appetite and weight gain (less glucose/fat broken down by cell resp.)
- feel cold
- constipation
- impaired brain development
leptin
- targets appetite control centre of the hypothalamus (bind to receptors in cell membranes)
- increase in adipose tissue increases leptin secretions into blood
- appetite inhibition (feelings of satiety, reduced food intake)
- experiment: mice with (two –>) ob/ob recessive allele injected with insulin showed decline in appetite
melatonin
- targets pituitary gland and other glands
- affects synchronization of circadian rhythms (24-hr cycle)
- circadian rhythms are controlled by two groups of cells in the hypothalamus
- melatonin increases at night, decreases at dawn
- at night drops body temp and possibly reduces urine production
- light detected by retina helps set circadian rhythm
- body’s circadian rhythm mostly maintained even w/o light cues
types of chromosomes (humans have 23)
- 22 pairs are autosomes (homologous pairs)
- 1 pair is sex chromosomes (determines sex) XX = female XY = male
testosterone in development
- testes develop from embryonic gonads when the embryo is becoming a fetus (in presence of testosterone)
- develops testosterone secreting cells
during puberty:
- testosterone secretion increases
- causes primary sexual characteristic of sperm production in testes
estrogen and progesterone
- female reproductive organs develop in absence of fetal testosterone and presence if maternal estrogen and progesterone (estrogen and progesterone are secreted by the mother’s ovaries and later her placenta)
- ovaries develop from embryonic gonads
during puberty:
- primary sexual characteristic of egg release
Menstrual cycle hormones
Produced from the pituitary:
- FSH: stimulates oocyte (and follicle) development, stimulates secretion of estrogen by follicle wall
- LH: matures oocyte and causes release (ovulation), promotes development of follicle wall into corpus luteum after ovulation (corpus luteum secretes estrogen and progesterone)
Produced from the ovaries:
- estrogen: develops endometrium, stimulates increase in FSH receptors, in high lvls will inhibit secretion of FSH and stimulate LH secretion
- progesterone: maintains endometrium, inhibits FSH and LH secretion by the pituitary gland
- HCG: pregnancy hormone (keeps estrogen and progesterone high)
- Oxytocin: birth hormone (contractions of uterus)
follicular phase (what happens?)
- follicles developing in ovary, growing egg in each follicle
- lining of the uterus thickens
- most developed follicle breaks open and egg is released into oviduct
- other follicles degenerate
luteal phase (what happens?)
- follicle wall becomes corpus luteum (in ovary)
- endometrium develops for implantation of embryo
- if no fertilization: corpus luteum breaks down
- endometrium shed during menstruation
Stages of the menstrual cycle
(follicular phase)
Day 1-4:
- menstruation (endometrium is shed)
- FSH increases and stimulates follicle development
Day 5-14
- FSH and follicle stimulates estrogen release
- estrogen stimulates endometrium thickening
- estrogen stimulates LH
- peak in LH causes ovulation
(luteal phase)
Day 14-28
- fall in LH, corpus luteum forms from now empty follicle
- corpus luteum releases progesterone
- progesterone thickens endometrium and inhibits FSH and LH
If no fertilization, progesterone and estrogen drop, triggering menstruation and FSH release
Causes of infertility
female:
- ova not maturing or being released
- abnormality in uterus (prevents implantation)
- antibodies in cervical mucus impair sperm
- blocked fallopian tubes
male:
- unable to achieve an erection or normal ejaculation
- low sperm count or sperm are abnormal w/low mobility
- blocked vas deferens
IVF (what is it?)
- In vitro fertilisation
- often used to overcome infertility
- fertilization that occurs outside the body
IVF steps
- Suitability for IVF is determined
- down-regulation: shutting down of the menstrual cycle by stopping secretion of the pituitary and ovarian hormones for two weeks- allows better control of egg production
- FSH and LH are given to stimulate multiple egg releases, superovulation: collects multiple eggs from the woman, high doses of FSH are injected over ~10 day period to stimulate development of multiple follicles
- when follicles reach 15-20mm in diameter, an injection of HCG given to maturation process, 36 hours later under a general anesthetic, (8-12) follicles are collected from ovaries
- prepared eggs are combined with sperm in sterile conditions, successfully fertilized eggs are then incubated before implantation
- after incubation, viable blastocysts (cluster of dividing cells made by a fertilized egg) are selected and developed into embryos
- up to 3 can be selected and placed in the uterus after 48 hours for implantation (risk of multiple pregnancy)
- ~2 weeks before implantation, woman takes progesterone (suppository) to aid in implantation. treatment continued until pregnancy test, if positive, until 12 weeks of gestation
- after bedrest, pregnancy test administered, if positive, pregnancy continues as normal, if negative, a few months can be waited to attempt process again
William Harvey’s investigation of sexual reproduction (seed and soil theory)
- “seed and soil” theory stated that the male produces a seed which forms an egg when mixed with menstrual blood, egg then develops into a fetus inside the mother
- Harvey studied animal reproduction in chickens and deer: dissected female deer after mating to find changes in sexual organs –> none was found
- therefore Harvey found that menstrual blood did not contribute to the formation of a fetus
- no microscopes: sperm, eggs and embryos were too small to observe
