Hormones Flashcards
What are the 2 major regulatory systems of the body?
endocrine and nervous
What are the main differences between the endocrine and nervous systems?
- endocrine involves slow acting hormone messengers whereas nervous involves fast acting electrochemical impulses
- endocrine regulates activities that require duration rather than speed whereas nervous regulates activity of muscles and glands
What does the endocrine system maintain?
homeostasis
What are hormones?
substances released by endocrine glands and transported throughout the blood stream to target tissues where they act to regulate specific functions
What is the classification of hormones based on?
the endocrine gland and the chemical nature of hormones
What are endocrine glands?
ductless glands that produce hormones that are released into the surrounding tissue fluid
What are exocrine glands?
glands with ducts that produce non-hormonal substances that are released into the atmosphere
Give examples of exocrine glands
sweat and saliva glands
What are the 3 central endocrine glands in the brain?
- pineal gland
- hypothalamus
- pituitary gland
What are the 6 peripheral endocrine glands?
- thyroid gland
- parathyroid glands
- thymus gland
- adrenal gland
- pancreas
- ovary/testes
Where are the parathyroid glands?
on dorsal aspect of thyroid gland
What are the major hormones of the hypothalamus?
releasing and inhibiting hormones e.g. TRH, CRH, PIH etc.
What are the 6 major hormones of the anterior pituitary lobe?
- luteinising hormone
- follicle stimulating hormone
- prolactin
- growth hormone
- adrenocorticotrophic hormone
- thyroid stimulating hormone
What are the 2 major hormones of the posterior pituitary lobe?
ADH and oxytocin
What are the 2 major hormones of the thyroid?
- thyroxine
- calcitonin
What is the major hormone of the parathyroid?
parathyroid hormone (PTH)
What are the 3 major hormones of the adrenal cortex?
- cortisol
- aldosterone
- androgens
What are the 2 major hormones of the adrenal medulla?
epinephrine and norepinephrine (adrenaline and noradrenaline)
What are the 4 major hormones of the testis?
- testosterone
- oestradiol
- inhibin
- MIH
What are the major 3 hormones of the ovary?
- oestradiol
- inhibin
- progesterone
What are the 3 major hormones of the placenta?
- hCG
- progesterone
- oestrogen
What are the 3 major hormones of the pancreas?
- insulin
- glucagon
- somatostatin
What is the major hormone of the pineal gland?
melatonin
What does BPA do when heated?
hasten puberty in females and increase the chances of various cancers
What do oestrogen disrupters do in males and females respectively?
females = mimic the activity of oestrogen and increase the risk of breast tumours
males = decrease sperm count and cause undescended testis (cryptorchidism)
What are the 3 classifications of hormone?
- amino acid (amine)
- peptide
- lipid derivative (steroid)
Gives examples of amino acid derived hormones
- tyrosine derivatives e.g. thyroid hormones and catecholamines
- tryptophan derivatives e.g. melatonin
What are lipid derived hormones?
carbon rings and side chains built from fatty acids or cholesterol
Give examples of lipid derived hormones
- eicosanoids
- steroid hormones
Which hormone classes are hydrophilic?
peptide hormones and amines in the adrenal medulla
Which 5 glands secrete peptide hormones?
- pituitary gland
- thyroid and parathyroid glands
- pancreas
- gonad (inhibin only)
- placenta
Which hormone classes are hydrophobic/lipophilic?
steroids (lipid) and amines (except adrenal medulla)
Which 3 glands secrete steroid hormones?
- adrenal cortex
- gonad
- kidney
Which 2 glands secrete amine hormones?
- thyroid
- pineal
Why must lipid soluble hormones be bound to plasma proteins?
to stay stable
How are hormone actions mediated?
by binding of the hormone to receptor molecules on target tissues
What are the 2 types of hormone receptor and what type of hormone do they bind?
- cell membrane receptors bind hydrophilic hormones
- intracellular receptors bind hydrophobic/lipophilic hormones
How fast and what are the actions of cell membrane receptors?
seconds to minutes to alter transcription, translation and various protein functions via intracellular second messengers
Give examples of intracellular second messengers
- cAMP
- DAG
- IP3
- calcium
- tyrosine kinase
What are intracellular receptors?
large oligomeric and phosphorylated proteins
How fast and what are the actions of intracellular receptors?
hours to alter transcription rates
Why do lipophilic hormones take longer to elicit a response?
they have to enter into the cell
What are the 3 degrees of hormone response?
- specificity of hormones
- signal amplification
- response
What are the 3 possible intracellular events of hormones binding to a receptor?
- alteration of channel permeability
- alteration of activity of proteins by acting on second messenger systems
- activation of specific genes to cause formation of new proteins
What are the 4 determinants of effective hormone concentration in plasma?
- rate of activation or conversion
- extent of binding to plasma proteins
- rate of removal from blood
- rate of secretion into the blood
What happens to a hormone that is not required?
it can be bound to another protein until it is required (prolongs half life) or broken down by stomach acids or peptidases
What are the effects of hormones proportional to?
their concentration in the plasma
How are most peptide hormones administered?
nasally or via injection
What can be used to measure insulin levels?
radioimmunoassay (RIA)
What is homeostasis?
when all body systems are functioning perfectly and together in a state of balance and health
What does negative feedback aim to do?
return to normal and inhibit the initial response
Where are feedback loops used extensively to regulate secretion of hormones?
the hypothalamic-pituitary axis (HPA)
Where is the only place where there is less negative feedback?
female reproductive system
What is circadian rhythm?
the physical, mental, and behavioral changes an organism experiences over a 24-hour cycle
What is the body’s biological clock?
the suprachiasmatic nucleus (SCN) of the hypothalamus
Describe levels of CLK and PER throughout the 24 hour cycle
- CLK accumulates in the SCN throughout the day and activates genes that tell us to stay awake
- CLK produces PER which accumulates and eventually inhibits CLK
- CLK by day and PER by night
What does melatonin do?
trigger sleep
What is melatonin inhibited by?
natural light filtering in and travelling through the optic nerve to the SCN
Why does jet lag occur?
crossing different time zones requires resynchronising the circadian rhythms and hormones can become out of sync (can take several cycles to readjust)
What can hormone imbalance result from?
- excess or deficiency/decreased secretion of hormones
- excess or deficiency/decreased target cell responsiveness
What does too much or too little hormone active result in?
endocrine disorders
What are tropic hormones?
hormones that regulate the secretion of another hormone from an endocrine gland
Give examples of tropic hormones
- CRH
- TRH
- HRHR
What is the commonality between the anterior pituitary and the posterior pituitary?
regulation by the hypothalamus
