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Hormones, Reproduction and Development (Lecture 21)

by Anu J
5 Pages
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York University
Natural Science
NATS 1675
Barbara Czaban

Lecture 20 – Hormones, Reproduction and Development - Hormones are chemical messengers o Coordinate and manage activities of the body’s cells o Responsible for growth, development and maturation o Involved in homeostasis o Secreted by endocrine glands or endocrine cells or neurons  Enter blood stream and travel to target cells  Target cell = the cell which is affected by that hormone  Hormones can have multiple target cells o Effect of hormone varies based on which target cell it is sent to o Two types of hormones:  Steroid hormones  Lipid-soluable  Can pass through cell membranes (lipid bi-layer)  Example: testosterone, estrogen  Non-steroid hormones  Water-soluable  Can’t pass through cell membrane without being actively transported  Example: peptide hormones o Hormones function by way of protein receptors, who receive, interpret and carry out the desired action o Varying mechanisms of change/action, depending on type of hormone  Steroid hormones  Diffuses through the target cell’s lipid bilayer membrane  Travels to nucleus  Binds to receptor  Hormone-receptor complex triggers gene activity in DNA  Strand of mRNA is made to complement that gene section of DNA  mRNA goes to ribosome  Ribosome creates required protein  Created protein carries out desired action  Non-steroid hormones  Diffuses from blood to the area where the target cell is located  Binds to protein receptor on target cell’s membrane  Protein triggers cyclic AMP (adenosine mono-phosphate)  Cyclic AMP triggers enzyme(s)  Enzyme(s) either inhibit or activate proteins in the cell’s cytoplasm  Inhibited/activated proteins have varying effects on cell - Endocrine system o Contains endocrine glands that secrete hormones into blood stream  Released in short bursts  Gland is simulated by signal  Gland releases hormone into blood  When gland stops receiving signal/stimulation, hormone concentration in blood stream goes down o Main hormonal glands to know:  Hypothalamus  Regulates the pituitary gland  Pituitary gland  Stimulates: o TSH - thyroid gland o ACTH – adrenal gland  Produces and releases: o OT – oxytocin (for uterine contraction, endometrium) o PRL - prolactin (for producing milk) o GH – growth hormone o Gonadotrophins  FSH – follicle-stimulating hormone (for egg/sperm development)  LH – luteinizing hormone (for producing testosterone) o ADH – antidiuretic hormone (for water retention)  Thyroid gland  Increases metabolic rate (T3 and T4)  Regulates development  Lowers blood calcium (calcitonin)  Parathyroid gland  Raises blood calcium (parathyroid hormone, PTH)  Pineal gland  Helps with sleep (melatonin)  Maybe helps with puberty (unknown to scientists)  Adrenal glands  Raises blood glucose (epinephrine, norepinephrine, cortisol)  Affects sodium/potassium levels (aldosterone)  Produces small amounts of sex hormones  Pancreas  Monitors blood glucose levels (insulin, glucagon)  Thymus  Produces t-cells (thymosine)  Gonads  Females: ovary o Estrogen and progesterone (for secondary sex characteristics)  Males: testes o Testosterone (for secondary sex characteristics) o Functions of endocrine system and endocrine glands  Affect sequential growth and maturation  Oversee patterned growth of muscles, bones, nervous tissue  Maintain healthy metabolic rate  Maintain ion/water balance  Monitor circadian rhythms (heartbeat, breathing rate, sleeping patterns)  Regulate blood levels of calcium and glucose  At puberty  Appearance of secondary sex characteristics o Development of eggs/sperm - Gl
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