Endocrine Physiology I - Central Hormones Flashcards
Endocrine system includes:
Hypothalamus
Pituitary
Thyroid
Parathyroids
Adrenals
Pancreas
Ovaries and testes
Chemical Regulating Systems
- Hormones
Hormones
- function
Hormones:
Made in gland(s) or cells
Transported by blood
Distant target tissue receptors
Activates physiological response
Control of
-enzymatic reactions
- Transport of ions or molecules across cell membranes
- Gene expression and protein synthesis
Exert effects at very low concentrations
Bind to target cell receptors
Half-life indicates length of activity
Hormonal Control
- Water balance and Blood volume
- Metabolism
- Energy balance and appetite
- Digestion, circulation
- Growth and development
- Reproduction
- RBC production
- Stress management
Tropic Hormones
Act on other endocrine glands
-Control of hormone secretion
-Hypothalamus and Anterior Pituitary
Non –tropic hormones
-Act on effector organs
E.g. thyroid, adrenals, pancreas
Hormones and Neuropeptides
Endocrine glands
-Secrete hormones
-Ductless
Neuro-secretory cells
-Secrete neuro-hormones (or neuro-peptides)
Adrenal medulla
* Catecholamines
Hypothalamus
* Posterior pituitary
Hormones
- Classification
- Peptides or proteins
Peptide hormones
-protein
Steroid hormones
- Cholesterol
Amine hormones
- Tryptophan or tyrosine (amino acids)
Preprohormone
- Large, inactive
Prohormone
- Post-translational modification
Hormone
- Final cuts make before it exits the cell to make it an active hormone
- Travels freely in the blood but cannot cross the cell membrane (needs a cell receptor)
-Short half-life
Peptide Hormone-Receptor
Complex
Surface receptor
Hormone binds
-Enzyme activation, or
-Opens channels, or
-2nd messenger systems
Cellular response
Peptide hormones: features
- Hydrophilic (water soluble)
- examples
Hydrophilic (water soluble)
-Can travel freely in the blood
- Cannot enter the cell (cross lipid membrane)
* Must use a membrane receptor
* Second messenger response
-Quick-acting, short half-life
Insulin, glucagon, calcitonin, parathyroid H.
Steroid Hormones: Features
- Cholesterol-derived
- examples
Cholesterol-derived
-Lipophilic and can enter target cell
-Must travel in blood bound to a protein
Cytoplasmic or nuclear receptors (mostly)
- Activate DNA for protein synthesis
Slower acting, longer half-life
Cortisol, estrogen, and testosterone
Steroid Hormones: Structure and action
- structure
- Cholesterol is the parent compound for all steroid hormones
Amine Hormones: Features
- structure
Ring structure
Derived from one of two amino acids
Tryptophan
* melatonin
Tyrosine
-Thyroid hormones
-Catecholamines
* Epinephrine
* Norepinephrine
* Dopamine
Catecholamines behave similar to peptides
Thyroid hormones behave similar to steroids
Blood Hormone levels depend on:
Rate of hormone secretion
Rate of hormone degradation
Rate of hormone excretion (kidneys)
Hormone Interactions
- Synergism
- Permissiveness
- Antagonism
Synergism
- Multiple stimuli—more than additive
* Eg. Glucagon, epi, and cortisol
Permissiveness
Need second hormone to get full expression
* Eg. TH and epinephrine
⬧ TH increases # receptor sites for epi
Antagonism
Pairs of hormones with opposing effects
Glucagon opposes insulin
Negative Feedback
Endocrine Control
- Three levels
- Other factors
- Self- regulates hormone levels
- Turns off response homeostatically
Three levels
Hypothalamic
* from CNS
Pituitary stimulation
* hypothalamic trophic hormones
Endocrine gland stimulation
* pituitary trophic hormones
- Hormone secretion is also affected by:
Emotional state
Disease state
Stress
Diet, sleep
Body cycles - Circadian rhythm, menstrual cycle
Endocrine Dysfunction
- Abnormal plasma concentrations of a
hormone
Abnormal plasma concentrations of a
hormone
Hyposecretion
* Too little hormone is secreted
Hypersecretion
* Too much hormone is secreted
Hyposecretion
- Primary hyposecretion
- Secondary hyposecretion
Primary hyposecretion
-Too little hormone is secreted due to gland abnormality
Causes
* Genetic (eg. Type I diabetes)
* Dietary (eg. Iodine and TH)
* Chemical or toxic
* Immunologic / auto-immune (eg. Hashimoto’s)
* Diseases / cancer
Secondary hyposecretion
- Gland is normal but too little hormone is secreted due to decreased tropic hormone (Eg. Ant. Pit.)
Hypersecretion
-Causes
- primary
- secondary
Causes
-Tumours
* Can continuously secrete excess hormone
- Immunologic factors
Primary hypersecretion
- Too much hormone is secreted due to
abnormality within gland
Secondary hypersecretion
- Excessive stimulation from outside the gland causes oversecretion
Hypothalamus
- controls
Hypothalamic Releasing and
Inhibiting Hormones
-Homeostasis, controls Anterior
Pituitary which then controls other endocrine glands
- Anterior pituitary hormones are stimulated or inhibited by one or
more hypothalamic hormones
Posterior Pituitary (Neurohypophyis)
- hormones made where
-stored where
- when released
Anterior Pituitary (Adenohypophysis)
Hormones made in the hypothalamus
* Oxytocin
* ADH
-Stored in the posterior pituitary
- When neuron excited, hormone is released
Secretes 6 peptide hormones, 5 are tropic
Oxytocin
- stimulates and promotes
ADH (Vasopressin)
- what is
- when released
- Stimulates uterine contractions in childbirth
-Promotes milk ejection during lactation - Anti-diuretic hormone
-Released if blood volume low or blood
osmolarity high, Eg. Dehydrated - Increases water reabsorption in kidney, decreases urine output
Diabetes Insipidus
- ↓ ADH (vasopressin)
- treatment
Excessive polyuria
* Urinating as much as 8-19 L of urine in 24 hours
⬧ More than 3 L
* Hypotension
* Dizziness
* Constipation
Treat
* Vasopressin replacement
Gonadotropins
- FSH – Follicle-stimulating hormone
- LH – Luteinizing hormone
FSH – Follicle-stimulating hormone
- Promotes egg and sperm production
LH – Luteinizing hormone
- Estrogen and Testosterone secretion
from gonads (acts with FSH) ovulation
Secreting Hormones
- TSH – Thyroid-secreting hormone
- ACTH - Adenocorticotropic hormone
TSH – Thyroid-secreting hormone
Acts on thyroid
Promotes TH secretion
- ACTH - Adenocorticotropic hormone
Acts on adrenal cortex
Promotes cortisol secretion
Prolactin
- what it is and does
Non-tropic hormone, acts on mammary glands
- Breast development, milk production
