Week 8 - Endocrine Flashcards
What are the Organs of the Endocrine System? (Brain)
Hypothalamus - production of ADH, oxytocin, and regulatory hormones.
Pineal Gland - Anterior lobe: ACTH, TSH, GH, PRL, FSH, LH, and MSH
Posterior Lobe: Release of oxytocin and ADH
Pineal Gland: Melatonin
Parathyroid Glands(located on posterior surface of thyroid.) Produces Parathyroid hormone (PTH)
Organs of endocrine system. (Non Brain)
Thyroid gland: Thyroxine, Triiodothyronine, calcitonin
Adrenal glands: Adrenal medulla - Epinephrine (E), norepinephrine (NE),
Adrenal cortex- Cortisol, corticosterone, aldosterone, androgens
Pancreatic islets: Insulin, glucagon
What are endocrine glands?
Ductless glands comprised of endocrine cells.
Have a good blood supply
Secrete hormones directly into blood stream
What are hormones?
Organic chemical messengers produced and secreted by endocrine cells into blood stream.
Bind to receptors(binding cites0 in target cells (cells w receptors)
This stimulates gene expression/protein synthesis to regulate, integrate and control a wide range of physiologic functions.
What are anabolic steroid hormones?
Some steroids have receptors in muscle that stimulate muscle protein production
Not all steroid hormones build muscle (oestrogen, progesterone, cortisol.)
Hormones don’t have specific effects
Risks:
Teenagers can have early skeletal and sexual maturation-stunted growth
Damage to liver, cardiovascular system and increased cholesterol
Males reduced sperm count, infertility, baldness, inc risk of prostate cancer
Females, facial hair, male pattern baldness, cessation of menstrual cycles
Receptors may be present in many tissues, with different effects in different tissues
What are the three types of hormones?
Amino acid derivatives - small molecules, structurally similar to amino acids
Peptide hormones- consist of chains of amino acids, largest class of hormones
Lipid derivatives - 2 classes of lipid based hormones: steroid hormones and eicosanoids
What are the two locations of hormone receptors?
On cell membrane- receptors for non-lipid soluble hormones, epinephrine, norepinephrine, all peptide hormones and eicosanoids. trigger cell signalling w G protein and second messengers eg cyclic AMP or GMP
Inside cell - receptors for steroid hormones and thyroid hormones
How does activation of cAMP occur?
- Activate G protein activates adentéllate cyclase enzyme
- Ándenla te cyclase converts ATP to cAMP
- cAMP activates kinase enzymes
- Activated kinases affect target cell
How do steroid hormones find receptors?
1.diffusiom through membrane lipids
2. Binding of hormone to cytoplasmic or nuclear receptors
. Binding of hormone-receptor complex to dna
4. Gene activation
5. Transcription and mRNA production
6. Translation and protein synthesis
How do thyroid hormones find receptors?
- Transport across cell membrane
- Binding to receptors at mitochondria and nucleus
- Binding of hormone-receptors complex to DNA
- Gene activation
- Transcription and mRNA production
- Translation and protein synthesis
What happens to hormones after secretion?
Free Hormones - Remain functional for less than 1 hour
Bind to target cell receptors or broken down in liver, kidney or by enzymes in plasma
Thyroid and steroid hormones - Remain in circulation much longer because most are “bound”
Enter bloodstream - more than 99% become attached to special transport proteins
Bloodstream contains substantial reserve of bound hormones.
Describe Hypothalamus and pituitary
Hypothalamus - Interface between nervous and endocrine systems
Regulatory hormones affect pituitary function
Pituitary -
Anterior pituitary: Hormones that control other endocrine organs
Posterior pituitary: Oxytocin and ADH release
What is the Hypophyseal portal system?
Neurosecretory neurons at median eminence secrete regulatory factors
Enter fee started capillaries in capillary bed in hypothalamus
Portal veins
Capillary bed in anterior pituitary
How are Prolactin (PRL) and Groth hormone (GH) regulated?
PRL - Hypothalamus produces releasing factor (PRF) and inhibiting hormone (PIH)
GH - Hypothalamus produces releasing hormone and inhibiting hormone.
Effects of growth hormone
Acts on liver to promote release of somatomedins, e.g Insulin like Growth factors which - Stimulate tissue growth (skeletal muscle and cartilage)
- Increase amino acid uptake/protein synthesis
Growth hormone acts directly on tissues to - stimulate cell division in epithelial and connective tissue
- stimulate triglyceride breakdown in adipocytes
- stimulates liver glycogen breakdown
