Functional anatomy and physiology Flashcards
What does the endocrine system consist of?
pituitary gland, thyroid, parathyroid, adrenal
glands, pancreas, ovary and testes
What are the 4 classes of hormones?
- Peptides
- Amines
- Iodothyronines
- Cholesterol derivatives and steroids
How are water soluble hormones transported?
Unbound to proteins
How do water soluble hormones interact with cells?
Bind to surface receptor
What is the half life of water soluble hormones?
Short
How quickly is the clearance for water soluble hormones?
Fast
What are examples of water soluble hormones?
Peptides, monoamines
How are lipid soluble hormones transported?
Protein bound
How do lipid soluble hormones interact with cells?
Diffusing into cells
What is the half life of lipid soluble hormones?
Long
How quickly is the clearance for lipid soluble hormones?
Slow
What are examples of lipid soluble hormones?
Thyroid hormones, steroids
Are peptides / monoamines stored?
Yes stored in vesicles
Are steroids stored?
No synthesised on demand
Describe features of peptide hormones
- Peptides vary in length
- Can be linear or ring structures and can bind to carbohydrates
- Peptide hormones can be used as granular store
What is the process of the synthesis of peptide hormones?
Synthesis: preprohormone –> prohormone
Packaging: Prohormone –> hormone
Storage: hormone
Secretion: hormone
Describe features of amine hormones
Water soluble, stored in secretory granules, release pulsatile, rapid clearance
Describe features of iodothyronines
- Thyroid hormones are not water soluble
- 99% is protein bound
- Only 20% of T3 in the circulation is secreted directly by thyroid
- Secretory cells release thyroglobulin into colloid – acts as base for thyroid hormone synthesis
- Incorporation of iodine on tyrosine molecules to form iodothyrosines
- Conjugation of iodothyrosines gives rise to T3 and T4 and stored in colloid bound to thyroglobulin
- T3 and T4 are
cleaved from thyroglobulin when TSH stimulates the movement of colloid into secretory
cell
Which type of hormone has receptors on cell membranes?
Peptide
Which type of hormone has receptors mainly in cytoplasm?
Steroid
What are some examples of steroid hormones who’s receptors are in cytoplasm?
Glucocorticoids (cortisol)
Mineralocorticoids (aldosterone)
Androgens (testosterone)
Progesterone
Which type of hormone mainly has receptors in the nucleus?
Thyroid
Which hormones have receptors in the nucleus?
Oestrogen
Thyroid hormone
Vitamin D
What are the different types of cholesterol derivatives and steroid hormones?
- Vitamin D
- Adrenocortical and gonadal steroids
What are features of vitamin D?
- Fat soluble
- Enters cells directly to nucleus to stimulate mRNA production
- Transported by Vitamin D binding protein
What are features of adrenocortical and gonadal steroids?
- 95% protein bound
- After entering cell
- Pass to nucleus to induce
response - Altered to active metabolite
- Bind to a cytoplasmic receptor
- Pass to nucleus to induce
Describe steroid actions
- Steroid hormone diffuse through plasma membrane and binds to receptor
- Receptor-hormone complex enters nucleus
- Receptor-hormone complex binds to GRE (glucocorticoid-response elements)
- Binding initiates transcription of gene to mRNA
- mRNA directs protein synthesis
Describe the control of hormone secretion
- Basal secretion – continuously or pulsatile
- Release inhibiting factors – dopamine inhibiting prolactin, sum of positive and negative effects (GHRH and somatostatin on GH)
- Releasing factors
Describe the control of hormone action
- Hormone metabolism: increased metabolism to reduce function
- Hormone receptor induction: induction of LH receptors by FSH in follicle
- Hormone receptor down regulation: hormone secreted in large quantities cause down regulation of its target receptors
- Synergism: combined effects of two hormones amplified (glucagon with epinephrine work together to raise glucose levels)
- Antagonism: one hormone opposes other hormone (glucagon antagonizes insulin)
What are examples of pituitary dysfunction?
● Tumour mass effects
● Hormone excess
● Hormone deficiency
What hormones does the posterior pituitary release?
Oxytocin and ADH
Describe the hypothalamo-pituitary-thyroid axis
Hypothalamus –> TRH –> anterior pituitary –> TSH –> thyroid gland –> thyroid hormones
What are some functions of thyroid hormones?
● Accelerates food metabolism
● Increases protein synthesis
● Enhances fat metabolism
● Brain development during foetal life and postnatal development
● Growth rate accelerated
What hormones does the anterior pituitary release?
TSH
ACTH
FSH & LH
GH
Prolactin
What class of hormone does the adrenal cortex produce?
Steroids
What types of hormones are produced in the adrenal cortex?
- Mineralocorticoids
- aldosterone
- Glucocorticoids
- cortisol androgens
- Androgens
- androstenedione
- dihydroepiandrosterone (DHEA)
What hormones are produced in the adrenal medulla?
- Epinephrine
- Norepinephrine
