Physiology Flashcards
Define the Endocrine system
System which controls organ function via the release of hormones (ductless endocrine glands), which then travel via the blood to a distal site of action
Exert their effects at very low concentrations
Must have action terminated (negative feedback)
Secreted in short bursts (24hr monitoring)
How does the Endocrine system differ from the Nervous system?
Nervous:
Local site of actions
Crossing a synapse
Released from a Neurone (neurotransmitter chemicals)
Endocrine:
Distant site of actions
Transported through the blood
Released from a cell, tissue or gland
What is a Neurohormone?
Nerve cell relates a chemical into the blood which is then transferred to a distal site of action (hypothalamus hormones)
What is a difference between Endocrine, Autocrine, Paracrine & Exocrine Glands
Endocrine are ductless and secrete into the blood (Insulin)
Exocrine have ducts and secrete into the external environment (Bile)
Autocrine cells secretions bind to the same cell (Cytokines)
Paracrine cell secretions bind to a neighbouring cell through diffusion in the ECF (Histamine)
Pineal Gland:
Hormone
Primary Target
Main Effect
- Melatonin
- Brain & Other Tissues
- Circadian rhythms / Immune function / Antioxidant
Hypothalamus:
Hormone
Primary Target
Main Effect
- Trophic hormones
- Anterior pituitary
- Release or inhibition of pituitary hormones
Posterior Pituitary:
Hormone
Primary Target
Main Effect
- Oxytocin / Vasopressin
- Kidneys, Breasts & Uterus
- Milk ejections, Labour & Water retention
Thyroid Gland:
Hormone
Primary Target
Main Effect
- Triiodothyronine, Thyroxine & Calcitonin
- Bone & Other Tissues
- Metabolism, Growth, Development & Plasma calcium levels
Parathyroid Gland:
Hormone
Primary Target
Main Effect
- Parathyroid hormone
- Bone & Kidney
- Regulate plasma Ca & Phsophate levels
Thymus Gland:
Hormone
Primary Target
Main Effect
- Thymosin & Thymopoietin
- Lymphocytes
- Lymphocyte development
Heart Cells:
Hormone
Primary Target
Main Effect
- Atrial naturalistic peptide
- Kidneys
- Increases Na excretions
Liver Cells:
Hormone
Primary Target
Main Effect
- Angiotensinogen / Insulin-like growth factor
- Adrenal cortex, blood vessels & other tissues
- Increase Blood Pressure / Growth
Stomach & Intestines:
Hormone
Primary Target
Main Effect
- Gastrin, Cholecystokinin & Secretin
- GI tract & Pancreas
- Assist digestion and absorption
Pancreas
Hormone
Primary Target
Main Effect
- Insulin, Glucagon, Somatostatin & Pancreatic polypeptide
- Many tissues
- Metabolism of glucose
Anterior Pituitary:
Hormone
Primary Target
Main Effect
- Prolactin, Somatotopin, Corticotropin, Thyrotropin, Folicle-stimulating & Luteinzing
- Breast, Liver, Adrenal cortex, Thyroid & Gonads
- Milk Production, Growth, Cortisol release, Thyroid hormone synthesis, Effective or sperm production
Adrenal Cortex:
Hormone
Primary Target
Main Effect
- Aldosterone, Cortisol & Androgens
- Kidney & Other tissues
- Na & K homeostasis, Stress response & sex drive in females
Adrenal medulla:
Hormone
Primary Target
Main Effect
- Epinephrine & Norepinephrine
- Many tissues
- Fight or Flight
Kidney:
Hormone
Primary Target
Main Effect
- Erthropoietin & Calciferol
- Bone marrow & Intestine
- RBC production & Calcium absorption
Skin:
Hormone
Primary Target
Main Effect
- Vitamin D3
- Intermediate hormone
- Precursor to Calciferol
Testes:
Hormone
Primary Target
Main Effect
- Androgens & Inhibin
- Many tissues & Anterior pituitary
- Perm production, secondary sexual characteristics & Inhibits FSH secretion
Ovaries:
Hormone
Primary Target
Main Effect
- Estrogen, Progesterone, Inhibin & Relaxin
- Many tissues, Anterior pituitary & Uterine muscle
- Egg production, secondary sexual characteristics, relaxes muscle & Inhibits FSH secretion
Adipose tissue:
Hormone
Primary Target
Main Effect
- Leptin, Adiponectin & Resistin
- Hypothalamus & Other tissues
- Food intake, metabolism & reproduction
Placenta (during pregnancy):
Hormone
Primary Target
Main Effect
- Estrogen, Progesterone, Somatomammotropin & Gonadotropin
- Many tissues & Corpus Iutem
- Foetal development, Metabolism & hormone secretion
3 Classifications of Endocrine Hormones
3
Peptide (amino acids) - Most common
Amine (tryptophan (melatonin) & thyrosine)
Steroid (cholesterol)
Describe the synthesis and storage of Peptide hormones (include location)
- Transcribed via mRNA as preprohormone (Rough Endoplasmic Reticulum)
- Cleaved into prohormone (Rough Endoplasmic Reticulum)
- Repacaged into separate vesicles which contain enzymes which chop prohormone into active hormone and inactive peptides (Golgi Apparatus)
- Stored invisibles until required (Cytoplasm)
Mechanisms of action of Peptide hormones
- Water soluble for transport in blood
- Cannot cross cell membranes fo bine to receptors on target cell
- Target either GPCR or tyrosine kinase receptors which change the functions of existing cell proteins (open/shut ion channels, activate/deactivate enzymes)
- Generate fast responses
What are the two target receptors of peptide hormones and their functions?
(2)
G Protein couple receptors:
Activates 2nd messenger system and ion channels leading to modification of proteins (Rapid response)
Throsine Kinase receptors:
Alters gene gene expression (slower longer lasting)
Types and subcategories of Amine hormones
2/1
Tyrosine
- Catocholamines: Dopamine, Norepinephrine & Epinephrine
- Thyroid Hormones: Thyroxine & Triiloforthyonline
Triptophan (melatonin)
Catechoiamines
Similar mechanism to peptide hormones
- Hydrophilic
- Lipaphobic
Thyroid hormones
Similar mechanisms to steroid hormones
- Hydrophobic
- Lipophilic
Describe the synthesis, storage and transport of Steroid hormones (include location)
Not stored - synthesised as required
Derived from cholesterol
Longer half life
Binds with albumin to transport through the blood (protects from enzymes)
What produces steroid hormones:
4
Gonads - Sex steroids
Placenta - hCG & Sex steroids
Kidney - Vitamin D3
Adrenal Cortex - Cotrtico
Mechanism of action of steroid hormones
Readily cross cell membranes as unbound ‘free’ hormone
Receptors within the cells
Moves into the nucleus
Lead to a change of gene expression
Genes control the synthesis of new protein
Law of mass action
Amount of free hormone is homeostaticly stable (very small levels)
How to calculate Total plasma hormone
Free hormone + complexed hormone
What feedback mechanism controls most hormone secretion
Negative feedback
What type of hormone system is usually controlled by negative feedback?
Hormones which are transported in plasma
What feedback system controls neuroendocrine pathways
Neural feedback loops
Which nerve cells control neural feedback
Sympathetic
What stimulates insulin release
Blood glucose (negative feedback) Autonomic nerve activity (neural feedback) Presence of food in gut (mechanoreceptors) Additional hormones (eg Glucagon)
