W1 Endocrine System Flashcards
Define hormone and endocrine system
The bodies second great controlling system which influences metabolic activities of cells by means of hormones.
Hormones: are chemical messages that act to alter the activity of its target cell
Discuss differences between endocrine and exocrine glands
The presence exocrine (needs ducts) or absences (endocrine) of ducts.
List differences between the endocrine and nervous systems
Endocrine communicates by only chemical means (hormones). Nervous system communicates via electrical impulses (action potential) (neurotransmitters).
Endocrine has a wider spread distribution of hormones, whereas nervous system is local and specific. Endocrine reacts more slowly to stimuli whereas, nervous system reacts quickly.
List the 3 mechanisims of action
Autocrine agents act on the cell that secreted it.
Paracrine agents act of adjacent cells.
Endocrine agents release hormones into blood stream, travelling to distant target cell, maintenance of homeostasis.
Describe how hormones are transported to their site of action
AMines and peptides are hydrophillic and mix easily with blood plasma → steroids and thyroid hormone are hydrophobic so they need to bind to transport proteins → they then disassociate with protein. Bound hormones have a longer circulating time in the blood stream as the protein protects it from being metabolically broken down. Resulting in longer floating in system .
Hormones act only at target cells of which contain specific receptors. {Lock and key mechanisim}.
Steroid hormone (nucleus or cytoplasm) HYDROPHOBIC: penetrate plasma
Non-steriod (protein, peptide & amine hormone). HYDROPHILLIC: must bind to to cell surface receptorDescribe how steroid hormones stimulate their target cells
& state any differences between the main chemical groups of hormones
Steroid hormones: binds to carrier proteins and penetrate phospholipid plasma membrane.
- Lipid soluable steroid hormone molecules detach from a carrier protein.
- Moves into intracellular space passing through phospholipid bilayer of target cell.
- Hormone enters nucleus and binds to receptor.
- Binds to DNA location
- Transcription of gene produced new mRNA strands.
- mRNA moves into cytosol where a ribosome translates into a protein
- New protein produces specific effects in target cell.
Describe how target cells can adjust their sensitivity to a hormone
When cell receives signal it can UP-REGULATION producing more receptors. = ↑ sensitive
The cell can desensitize it’self by DOWN-REGULATION reducing the number of receptors= less sensitive.
List similarities between the endocrine and nervous systems
Both act via receptors. Several chemicals acts as both neurotransmitters and hormones. Presence of neuroendocrine cells indicate association between town. Both hormones and neurotransmitters produce overlapping effects on same organ.
List the 2 main chemical classes of hormones and give examples of each
Steroid hormones
Non-steroid hormones (amino acid derivatives, peptide/proteins/glycoproteins)
Describe the chemical class of steroid hormones
Synthesized from cholesterol and is lipid soluable. Eg. Progesterone, testosterone, cortisol
Describe the chemical class of non-steriod hormones
Synthesized by amino acids. 1. Peptides: smaller proteins, growth hormone, oxytocin, glycoproteins.
2. Amino acid derivatives: Synthesized by modifying a single molecule of tyrosine or trytophan.
modifications of phenylalanine, tyrosine and tryptophan (produced by the thyroid gland
Describe the chemical class of non-steriod hormones
Synthesized by amino acids. 1. Peptides: smaller proteins, growth hormone, oxytocin, glycoproteins.
2. Amino acid derivatives: Synthesized by modifying a single molecule of tyrosine or trytophan.
modifications of phenylalanine, tyrosine and tryptophan (produced by the thyroid gland
Describe how non-steroid hormones stimulate their target cells
Non-steroid hormones: Hydrophillic they must bind to cell surface receptors. SECOND MESSENGER
They cannot pass through membrane, they bind to receptor proteins on the outter surface of the plasma membrane - G-protein.
1. First messenger binds to a fixed G protein-coupled receptor in the target cell.
2. The hormone receptor complex activates the G protein.
3. Activates G protein reacts with GTP which activates adenyl cyclase.
4. Adenly cyclase removes phosphates from ATP converting to cAMP (second messanger).
5. cAMP activates protein kinases.
6. Protein kinases activate specific intracellular enzymes.
7. The activated enzymes then influence celluar reactions thereby producing target cells response to the hormone.
List 4 ways of which hormones relationships with one another
Antagonistic: hormones have opposite effects
Additive: Hormones add together to increase effect
Permissive: First hormone needed for the second one to have effect.
Integrative: hormones have different by complimentary effects
Describe the anatomy of the hypothalamus and function
Hypothalamus is pea size, located within the skull at the base of brain. It is the major link between NS and endocrine system. Critical in maintaining homeostasis. Autonomic neurons control secretion of hormones from adrenal glands → sympathetic NS ( noepinephrine)
Functions include: production of hormones, regulation of eating and drinking, controls body temp, sleep cycles. Secrets, releases hormones that controls secretion from the pituitary gland, ANS control hormones from adrenal gland
List hormones produced by the hypothalamus, list target organ/s or tissue & state principal effects
(7) - Thyrotropic releasing hormone, corticotropin, gonadotropin, growth hormone, growth hormone inhibiting hormone, prolactin, prolactin inhibiting hormone
List hormones produced by the anterior pituitary gland, list target organ/s or tissue & state principal effects
(6) Follicle-stimulating hormone: Ovaries, testes: growth of ovarian follicles secretion of estrogen. Male: sperm porduction.
Luteinizing hormone: Ovaries, testes: ovulation, testosterone producion.
Thyroid-stimulation hormone: thyroid secretion of thyroid hormone.
Adrenocorticotropic hormone: adrenal cortex growth, secretion of glucocotioids.
Prolactin: mammary glands: milk synthesis
Growth hormone: Liver, bone, cartilage, muscle fatL widespread
List hormones stored by the posterior pituitary gland, list target organ/s or tissue & state principal effects
Oxytocin (OXT) for uterine contractions Antidiuretic Hormone (ADH) for water retention and blood volume.
Explain how pituitary secretion is controlled by the hypothalamus and target organs and exemplify using multiple examples
Hypothalamic control enables the brain to monitor conditions within and outside the body to stimulate or inhibit the release of pituitary horomes. Eg. Child birth: pressure on cervix → to hypothalamus release oxytocin → uterine contraction stimulates → more pressure of cervix.
MILK Secretion:(positive) baby crying stimulates hypothalamus → releases prolactin and oxytocin → milk production and ejection stimulated. Hypothalamus → releaseing hormone → pituitary gland → pituitary hormone → target organ → peripheral hormone = effect (negative feedback loop)
Describe the effects of growth hormone
Bone growth at epiphyseal plates during childhood and adolescence, GH induces livers to produce stimulants (insulin-like growth factors which then stimulate target cells → protein synthesis increases - boosts transcription of DNA → mRNA, amino acid uptake into cells, supresses protein catabolism → lipid metabolisim increaded providing energy for tissues → glycogenesis
Describe the the hypothalamus & pituitary gland & their relationship to each other
The pituitary gland recives communication from the hypothalmus directly, regulatory hormones secreted by the hypothalamus enter the hypophyseal portal system, this system efficiently transports hormones from the hypothalamus to the anterior pituitary gland
Pineal gland; state its location, list the hormone/s it produces and their effects
Location: near centre of the brain between the two hemispheres in the roof of the third ventricle.
Produces: Melatonin - setting of body rhythmic cycle.
Regulates reproduction and seasonal breeding (FSH, LH)
Thyroid gland; state its location, describe its structure, list hormones produced & their effects
Location curves across the anterior of the trachea. 2 different cell types regulate two different homeostatic process.
Basal metabolic rate: Aminoacid = Tyrosine produces into thyroxine T3 T4. Increases oxygen rate, breakdown of fat, heat production
Calcium levels: c cells produce calcitonin is released when blood calcium levels are too high (calci-tone-down)
Parathyroid gland; state its location, describe its structure, list hormones produced & their effects
Two pairs of parathyroid glands (4) are embedded in the posterior surface of the thyroid gland. Produce: parathyroid hormone which then signals to increase calcium via bone, kidney (cholesterol into vit D to make Ca+) not to pee out Ca+. Intestines, Increase calcium re absorption from intestine. Negative feedback loop: too much calcium = calcitonin ↓, deposits in bone and PTH ↑ Ca+ excretes in kidneys
