Endocrine System SEM1 Flashcards
How do hormones travel to get to target cells
Hormones travel via bloodstream
What are neuroendocrine hormones
Neural cells that release chemical signals into the bloodstream
Where are releasing hormones released from and what do they act on
Released from hypothalamus and act on the pituitary gland
Where are stimulating hormones released from and what do they act on
From pituitary to act on another endocrine gland
Where are non-tropic hormones released from
From endocrine gland to the target cells
What does the hypothalamus release
Thyrotropin releasing hormone (TRH)
What does the anterior pituitary release
Thyroid stimulating hormone (TSH)
What does the thyroid release
Thyroid hormone (T3 and T4)
Where are amino hormones derived from
Derived from tyrosine
What hormones are encoded in genes
Peptide and protein hormones
Where are steroid hormones derived from
Derived from cholesterol
What are properties of protein and polypeptide hormones
Stored in secretory granules and released on stimulation
Ca++ dependent event - exocytosis
Hydrophilic - cannot freely cross membranes
What are properties of steroid hormones
Steroids are lipophilic molecules that freely cross membranes
Steroids are not stored but released as made
Travel in blood
What changes can second messengers create
Phenotypic changes in target cell
What are the phenotypic changes second messengers create in target cells
Alter phosphorylation of proteins
Alter permeability of membranes
What does hormone binding receptors being internalised result in
Results in reduced responsiveness of target cell and receptor may be recycled to cell surface or degraded
What are intracellular receptors
Steroid and thyroid hormones and act via intracellular receptors
How does the hormone-receptor (HR) complex interact with DNA
Interacts directly with DNA in chromatin fibre at the promoter of specific genes
How does the hormone-receptor (H-R) complex act
Acts as a transcription factor to enhance (or decrease) rate of transcription
What do the physiological effects of hormones depend on
Depend on their concentration in blood and extracellular fluid
What are the three factors which determine the concentration of hormones as seen by the target cells
Rate of production
Rate of delivery
Rate of degradation and elimination
What can cause for abnormal production or function of hormones
Genetic diseases
Autoimmune diseases
Gene mutations
What does the anterior pituitary gland secrete
Secretes trophic hormones that influence activity of target glands and tissue
Where is the thyroid located
Anterior to the trachea
Inferior to the larynx
How are Tri-iodothryonine (T3) and thyroxine (T4) synthesised
Synthesised by follicular cells by iodination of throsine
How are Tri-iodothryonine (T3) and thyroxine (T4) stored
Stored extracellularly in follicular colloid on surface of thyroglobulin molecules
What are the actions of thyroid hormones
Metabolic effects
Physiological effects
Reproductive effects
Developmental effects
Cellular effects
What are the metabolic effects of thyroid hormones
Heat production
Glucose production
Protein synthesis
Lipid metabolism
What are the physiological effects of thyroid hormones
Stimulation of heart rate
Mental activity
Red blood cell production
Appetite
Gut motility
What are the reproductive effects of thyroid hormones
Female fertility
Maintenance of milk secretion
Onset of puberty
What are the developmental effects of thyroid hormones
Normal brain development
What are the cellular effects of thyroid hormones
RNA synthesis
Na+/K+ dependent ATPase activity
Amino acid transport into responsive cells
How does hypothyroidism occur
Lack of thyroid hormones either because of the thyroid (primary) or from lack of stimulation by TSH (secondary)
How does hyperthyroidism occur
Over activity of the gland
What does the posterior pituitary gland secrete
Secretes oxytocin and vasopressin
What is the role of osmoreceptors
Send signals to the neuroendocrine cell in the hypothalamus that make vasopressin when plasma osmolality exceeds the threshold => increase vasopressin secretion
What factors can cause the stimulation of vasopressin secretion
High osmolality
Low blood volume
Low blood pressure
Angiotensin
Nicotine
Nausea
What factors can cause the inhibition of vasopressin secretion
Low osmolality
High blood volume
High blood pressure
Atrial natriuretic peptide
Alcohol
What is diabetes insipidus
Inability to secrete or respond to vasopressin
What does it mean to be nephrogenic
Kidneys do not respond to ADH
What is the role of oxytocin
Stimulates contraction of myopithelial cells in mammary glands to cause milk ejection
What is endocrine tissue called
Pancreatic islets or islets of langerhans
What are the secratory cells of the pineal gland called and what does the gland secrete
Secretory cells = pinealocytes
Releases melatonin
