Endocrine System Flashcards
(17 cards)
Exocrine gland
secrete their products into a duct (eg. Sweat or intestines)
Endocrine glands
ductless and release hormones into the blood.
What’s endocrine system
Is one of the body 2 major communication systems:
Consists of glands and organs that secrete hormones
A single gland may screw multiple hormones
Hormone structure and synthesis: fall into 3 major structural clases
Amines (thyroid hormones, dopamine and catecholamines)
Peptides and proteins ( majority of hormones are peptides - insulin) they are water solubles and circulate dissolved in plasma , can bind to plasma
Steroids ( aldosterone, cortisol, androgens , estrogens - circulate mainly bound to plasma proteins
(Liver and kidney major organs that remove hormones from plasma by metabolising them or excreting.
Hormones
Released by glands to elicit a response ( enhance or inhibit a cellular response)
Present at very low concentrations ( much lower than other similar molecules)
Response to small amount is due to the way the cell “behaves” ( this means that although a given hormone travels throughout the body in the blood it only affects specific target cells)
They act in synchrony with the nervous system - endocrine. ( chemical messenger acting slowly often lasting longer) and nervous system ( electrical conduit system which is instantaneous and short lived)
Hormone functions
Help regulate ( energy, metabolism,contraction of smooth and cardiac muscles,glandular secretion, and chemical composition)
Control growth and development
Regulate operation of reproductive system
Help establish circadian rhythms
Mechanism of hormone action
Mechanisms of hormone action:
They have specific destinations (target tissue) the prescience of specific receptors for those hormones on or in target cells necessary for response.
For steroid and thyroid hormones the majority of receptors are inside target cells (lipid soluble)
For peptides hormones and catecholamines (adrenaline) are on the plasma membrane.
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Responsiveness of target cell to hormone depends on
The responsiveness of target cell to hormone depends on :
1) hormones concentration in the blood
2) abundance of the target cells hormone receptors
3) influence exerted by other hormones ( permissive,synergistic,antagonist.
Negative feedback systems regulate the secretion of many hormones.
Inputs that control hormone secretion
Inputs that control hormone secretion:
1) Plasma concentration of an ion or nutrient that hormone regulates eg.insulin secretion ( increase in blood glucose, passing insulin secreting cells stimulating them , activates removing glucose and storing it , dropping blood glucose - homeostasic control)
2) neural input to endocrine cells - the autonomic nervous system controls hormone secretion via adrenal medulla and other glands , as well as hypothalamus, neural input controls secretion of many hormones.
3) other hormones - often secretion of particular hormones is controlled by blood conc of other hormones - tropic hormone.
What’s the hypothalamus
Hypothalamus, a structure deep in your brain, acts as your body’s smart control coordinating center. Its main function is to keep your body in a stable state called homeostasis. It does its job by directly influencing your autonomic nervous system or by managing hormones.
What’s the pituitary gland
The pituitary gland is often called the master gland because it controls several other hormone glands in your body, including the thyroid and adrenals, the ovaries and testicles.
Posterior pituitary gland - neural extension of hypothalamus, Hormones are synthesized in the hypothalamus, axons pass down the infundibulum, terminate in the posterior pituitary and release hormones E.g., oxytocin (used in labour) and vasopressin (control blood pressure)
The anterior pituitary gland - secretes growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), prolactin, and two gonadotropic hormones—follicle-stimulating hormone (FSH) and luteinizing hormone (LH), controlled by hypophysiotropic hormones from hypothalamus via the portal vessels.
Thyroid gland
Thyroid gland -
multiple effects across the body eg.protein synthesis and increase DNA replication, sits within the neck in front of the trachea.
Produces thyroxine and triiodothyronine.
Thyroid stimulating hormone production is controlled by negative feedback of T3 and T4, this associated with increase oxidative substrate metabolism and mitochondrial enzyme
Increase metabolic rate
What’s cortisol
Cortisol -
Cortisol secretion during stress is mediated by the hypothalamus–anterior pituitary gland system
Cortisol in non stress full situation
Non stressful situations :
Cortisol affects the responsiveness of smooth muscle cells to epinephrine
and norepinephrine (Thus, helps maintain normal blood pressure)
Cortisol required to maintain the certain enzymes conc. involved in
metabolic homeostasis.(Thus, prevents plasma glucose concentration dropping too far below normal)
Cortisol in stressful situation
Stressful situations:
Effects on metabolism
(Stimulation of protein catabolism in bone, lymph, muscle, and elsewhere - Stimulation of liver uptake of amino acids and their conversion to glucose (gluconeogenesis) - Maintenanced of plasma glucose concentrations - Stimulation of triglyceride catabolism in adipose tissue, with release of glycerol and fatty acids into the blood
Enhanced vascular reactivity, improving cardiovascular performance
Unidentified protective effects against the damaging influences of stress
Inhibition of inflammation and specific immune responses
Inhibition of nonessential functions (e.g., reproduction &
growth
When stress response is triggered
When the stress response is triggered, the Sympathetic Nervous System is
activated, triggering the release of epinephrine At the same time, the endocrine system releases cortisol from the adrenal gland
Leads to faster breakdown of fuel, increase in cardiac function and increase in ventilation
Growth hormones ?
Growth hormone -
Growth hormone secretion is stimulated by growth hormone releasing hormone and inhibited by somatostatin
Major stimulus of postnatal growth, acts direct in cells to stimulate protein synthesis and highest during adolescence.
Testosterone (produced by male testes and small quantities in the female ovaries - promotes muscle growth and development of male characteristics)
Oestrogen (produced by female ovaries influencing menstrual cycle, also found in men small amounts - promotes development of female sex characteristics and adipose tissue growth)
