Hormones Flashcards
(15 cards)
Difference between Endocrine and Exocrine
Endocrine:
ductless, inserted directly into he bloodstream, used blood as vesicle, varied distances
Exocrine:
ducts, secreted through ducts, secreted directly to target, relatively short distances
Types of Hormone Production
Chronic/constitiutive release - maintains constant concentration in the blood
Acute/stimulated release - episodic release when required, tightly controlled by stimulus and feedback
Cyclic/pulsatile release - regular rhythm of production, peaks correspond to physiologically relevant times for hormone action
Types of hormone classification
Peptide hormones
Steroid hormones
Amide hormones
Explain peptide hormones
Peptide hormones are pre-synthesised and stored in vesicles ready for release. They are released following stimulus. They are hydrophilic - secreted directly into plasma, short half life, degraded during transmit, requires continuous secretion to prolong action.
Signal transduction through 2nd messenger on membrane,modified exciting protein creating a rapid response.
Explain steroid hormones
Steroid hormones are stored in a pre-cursor form and are transported as lipid droplets. Are converted to active state when signal is released. Simple diffusion across membrane. Due to poor solubility it is contained by plasma carrier (hydrophobic) Plasma container resulting in longer half-life.
Intracellular receptor, slow response
Explain Amide hormones
Derived from tyrosine or trypophan
Pre-cusors for 2 very different classes of hormones
Differences between anterior and posterior pituitary
Anterior pituitary - true endocrine tissue, is an epithelial organ, Connected to hypothalamus through 2 capillary beds (portal systems), makes up 2/3rds of the gland
Contains tropic hormones which stimulate or inhibit release of other hormones
Posterior pituitary - Neuroendocrine tissue, neural tissue organ, connected to hypothalamus through neural connection, secretes neurohormones made in hypothalamus, 1/3rd of gland
The posterior pituitary and neurohormones
2 types of neurohormones: vascopression (ADH) and oxytocin.
synethsised in the magnecellular neurons in hypothalamus, creates ADH or oxytocin, do not synapse with other neurons, terminals end directly on the capillaries. Hormones synthesised in hypothalamus and transported to the nerve terminal in posterior pituitary ready for release. activation results in release directly into bloodstream.
Vasopression (ADH) and Oxytocin functions
Vasopression (ADH):
regulates water balance, release is triggered by increased plasma osmolarity, decrease in plasma volume/blood pressure.
Oxytocin:
Milk ejection, labour, milk duct smooth mucsle - contracts the muscle
Hypothalamus- hypophyseal portal systems
Hypothalamus hormones released from stimulated hypothalamic neuron, neuron moves through portal systems ans binds to a receptor in anterior pituitary, pituitary then releases hormone that diffuses into capillary systems and into circulation.
Portal systems - short distance -very rapid and dynamic
Anterior pituitary and feedback controls
Complex multi-tiered pathways. Involved in 3 integration centres, Hypothalamus, anterior pituitary, target endocrine cell. Hormones themselves are negative feedback control, each hormone feeds back to inhibit hormone secretion by integrating centres earlier in the reflex. Positive feedback from endocrine target = long-loop feedback. Positive feedback from anterior pituitary to hypothalamus =short-loop feedback
Growth hormone and IGF-1
Growth hormone - stimulates proliferation of pre-chondrocytes - chondrocytes (produce IGF-1)
Metabolises uptake of plasma amino acids and the breakdown of fat.
IGF-1 stimulates chondrocytes to divide and produce cartilage (foundation for bone growth)
Metablises uptake of plasma animo acids and uptake of glucose/energy substrates into cells
Explain Thyroid gland
bi-lobed gland at base of throat, arranged in filaments. Synthesised from tyrosine, requires plasma binding proteins into tyroid-binding globulin (TBG) long-half life, receptors located intracellualrly in nuclei, slow initiation of change of gene expression.
Metabolic functions of cortisol
- Stimulates gluconegenesis
- protein carbohydrates stores (glycogen)
- build-up or breakdown glycogen stores depending on stress - breakdown and uses fatty acids as energy sources - alternative to sources
- break down protein into amino acids to use as energy source
Mineralocorticoids
are intracellualr steroid receptors which alter gene expression, increased expression of Na transport proteins
