Physiology Flashcards
The endocrine system involves ducts. True/False?
False
It is a ductless system involving glands that secrete directly into blood
How is specificity of signalling by endocrine glands achieved?
Chemically distinct hormones
Specific hormone receptors
Distinct distribution of receptors
List the main endocrine glands of the body
Hypothalamus Pituitary Parathyroid Thyroid Adrenal gland Pancreas Placenta Ovaries/testes
What is meant by an autocrine gland?
Hormone released acts back on the structure that released it
What is meant by a paracrine gland?
Hormone released acts on neighbouring structures
List the 3 main classes of hormones
Glycoproteins + peptides
Steroids
Tyrosine derivatives
Give an example of glycoprotein/peptide hormones
Insulin
Growth hormone
Oxytocin
Prolactin
Give an example of a steroid hormone
Cortisol
Testosterone
Give an example of a tyrosine-derivative hormone
Adrenaline
Thyroid hormone
Melatonin
A whole protein is always required to achieve hormonal effect. True/False?
False
Protein can be cleaved into active hormonal units
On a basic level, how are amines, peptides and proteins released from the endocrine cell?
Synthesised, packaged into vesicles and then released in response to stimuli via exocytosis
On a basic level, how are steroid hormones released from the endocrine cell?
Synthesised upon demand, then stimuli increases cellular uptake and availability of cholesterol + rate of conversion into pregnenolone, which is then used to build steroid to be released
Steroid hormones travel freely in blood. True/False?
False
Usually has carrier protein in inactive form
Which carrier protein binds cortisol?
Cortisol-binding protein! FANCY THAT
Which carrier protein binds thyroxine (T4)?
Thyroxine-binding globulin
Which hormones normally bind to sex steroid-binding globulin?
Testosterone
Estradiol
Free and bound lipophilic hormone are in equilibrium in the blood. True/False?
True
What does “tropic” mean with regards to hormones?
Refers to a hormone that acts upon another endocrine gland to regulation secretion of hormone
What are the biggest players in elimination of hormone?
Liver
Kidney
Time taken to reach half life of amine hormones is achieved in seconds/minutes/hours
Seconds
Time taken to reach half life of protein hormones is achieved in seconds/minutes/hours
Minutes
Time taken to reach half life of steroid hormones is achieved in seconds/minutes/hours
Hours
List the 3 main distinct types of hormone receptor
GPCR
Receptor kinases
Nuclear receptors
Which of the 3 main types of hormone receptor are cell surface receptors?
GPCR
Receptor kinases
Which of the 3 main types of hormone receptor are intracellular receptors?
Nuclear kinases
Describe class 1 nuclear receptors
Activate by steroid hormones
Usually in cytoplasm bound to heat-shock-proteins
Describe class 2 nuclear receptors
Activate by lipids
Present in nucleus
Describe the hybrid class of nuclear receptors
Activated by T3 Similar function to class 1
Give an example of a hormone that utilises signalling via receptor kinases
Insulin
What are the 3 main components of the hypothalamic pituitary axis?
HYPOTHALAMUS influences PITUITARY to secrete hormones to act on PERIPHERAL GLAND (thyroid, adrenal etc.)
List the main hormones secreted by the anterior pituitary
GH LH/FSH ACTH TSH Prolactin
List the main hormones secreted by the posterior pituitary
ADH
Oxytocin
What is the effect of peripheral hormones secreted by target glands (thyroid, adrenals etc.) upon the pituitary and hypothalamus?
Negative feedback loop (inhibition)
List the factors that influence our ability to measure hormone levels
Pattern of secretion Presence of carrier proteins Interfering agents Stability/half-life Absolute concn
What is the major determination of hormone concentration?
Rate of secretion
Outline the thyroid hormone axis
Hypothalamus secretes TRH which stimulates anterior pituitary to stimulate TSH which stimulates thyroid to produce thyroid hormones
Thyroid hormones inhibit the thyroid, anterior pituitary and hypothalamus to reduce further thyroid hormone release. True/False?
False
They do not inhibit the thyroid gland!
What test is done to evaluate thyroid hormone?
Highly-sensitive TSH assay
Outline the hypothalamic-pituitary-adrenal axis (HPA axis)
HYPOTHALAMUS releases CRH to stimulate ANTERIOR PITUITARY to release ACTH which stimulates ADRENALS to release cortisol
Which parts of the HPA axis does cortisol inhibit via negative feedback loop?
Anterior pituitary
Hypothalamus
Random cortisol measurement is useful in determining cortisol levels. True/False?
False
Circadian rhythm means levels will vary widely throughout the day
GH stimulates the liver to produce what hormone?
IGF-1
Which cells secrete prolactin?
Lactotroph cells in the anterior pituitary
Which hypothalamic hormone inhibits release of prolactin?
Dopamine
What is the rate-limiting step in steroid hormone metabolism?
Cholesterol to pregnenolone
