L18- Overview Of Endocrine Flashcards
What is the endocrine system
Group of glands which secrete hormones into circulatory system in response to specific signals
(Circulatory syst carries them to target organs)
How do target organs respond to the hormone
Target cells express specific hormone receptors which allow them to respond to the hormone
Endocrine vs nervous
Endocrine- wireless,hormones travel long distance in blood, communication depends on expression of specific receptors, can be rapid or slow and long lasting
Nervous- wired, nt diffuses short distance, communication dependant on anatomical neuron relationship, rapid and brief
What do hormones regulate
Homeostasis
Energy metabolism
Growth and development
Reproduction
Behaviour
Classes for hormones
Peptide - chain of amino acids
Sterioid- cholesterol derivative
Amine- amino acid (tyrosine or tryptophan) derivatives
Steroid hormone secretion and transport
Steroid hormones are lipophilic (leaves cell by diffusion)
Secretion enhanced by increasing synthesis (not stored)
Hormone not soluble so transported bound to specific proteins in circulation
Peptide hormone secretion and transport
Peptide hormones are hydrophilic (stored in secretory vesicles)
Fusion of the vesicles with the plasma membrane (exocytosis) releases hormones into blood stream
Hormone is freely dissolved in bloodstream
Amine hormone secretion and transport
Dependant on specific amine hormone eg.
Catecholamines- exocytosis, dissolved in plasma
Thyroid hormone- transporter protein, bound to carrier protein
Where are peptide hormone receptors found
Plasma membrane of target cell
Where are steroid hormone receptors found
Intracellularly of target cell (have to diffuse into cell to bind)
Where are amide hormone receptors found
Depends on specific hormone eg.
Catecholamine- surface receptor
Thyroid- intracellular
What hormone modulates gene transcription
Steroid hormones
What hormone activates intracellular signalling pathways
Peptide hormones
What amide hormone activates second messenger
Catecholamine
What amide hormone effects gene transmission
Thyroid
What factors control hormone secretion
Conc of ions/nutrients in plasma
Environmental changes
Neuronal activity
Other releasing hormones released from hypothalamus or pituitary
What regulates hormone release from the pituitary gland
Hypothalamus
What is the hypothalamus important for
Homeostasis
Receiving signals from CNS
Producing releasing and inhibiting hormones which act on pituitary gland
Link nervous and endocrine
Pituitary gland
Master endocrine gland which releases many different hormones
Divided into anterior and posterior
Posterior pituitary
Releases hormones but doesn’t synthesise them- synthesised in hypothalamus.
Axons from hypothalamic neurons enter posterior, releasing hormones (oxytocin and ADH) which enter capillaries of posterior pituitary. These are then released into general circulation.
Anterior pituitary
Hormones released from anterior pituitary are synthesised there.
Hormones released from hypothalamus and move through portal veins into anterior pituitary. These either inhibit or stimulate hormone release from cells in anterior pituitary. Hormones released from anterior pituitary go straight into circulation, some of which control hormone secretion from other endocrine glands.
3 hormonal sequence use
Allows for different types of hormonal feedback regulation
Facilitates signal amplification
Types of hormones that use feedback regulation
Thyroid hormones and parathyroid hormone secretion
