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
