Ch 16 - Endocrine System Flashcards
Long-distance chemical messengers that cause a change in metabolic activity of a cell
Hormone
Effects are usually long-lasting!!
Hormones control:
1) Reproduction
2) Growth and development
3) Immune system activation
4) Maintenance of various blood components (glucose, electrolytes, water, etc.)
5) Etc, etc, etc.
Glands Involved in Endocrine System
Endocrine glands, obviously
But also sonetimes autocrine and paracrine glands
autocrine - affects same cell
paracrine - affects different cell in same tissue
Classification of hormones
1) Amino acid-based hormones - molecular size varies (amino acid derivatives, peptides, proteins) - water soluble, circulate w/o carrier
2) Steroid hormones - synthesized from cholesterol (gonadal hormones and adrenocortical hormones are only steroid hormones in body) - non water soluble, circulates WITH carrier
Hormone Actions
1) Altering plasma membrane permeability or membrane potential
2) Stimulates synthesis of enzymes/proteins inside cell
3) Activates/deactivates enzymes
4) Induces secretory activity
5) Stimulates mitosis
can only affect target cells with receptors that can bind it
Mechanisms of Hormone Action
1) Second messenger-systems: use receptors found on surface of plasma membrane (glucagon, TSH)
2) Intracellular systems: hormone enters cell first, then binds to intracellular receptors (steroid hormones, T3, T4)
Receptor-hormone complex binds specific regions of DNA - DNA transcription occurs
Hormone stimulus mechanisms
1) Humoral stimuli: changing blood levels of ions & nutrients (Ca2+ levels + parathyroid gland)
2) Neural stimuli: nerve fibers stimulate hormone release (infrequent, NE&epinephrine release)
3) Hormonal stimuli: hormone released in response to other hormones (hypothalamic hormones stimulate/inhibit anterior pituitary gland)
controlled by negative feedback mechanisms
Factors of activiation of cell by hormone
1) Blood levels of hormone
2) Number of receptors for specific hormone on/in cell
3) Affinity of receptor to the hormone
How amount of hormone in blood/cell can change the NUMBER OF RECEPTORS in/on target cell
Up-regulation: increase receptor number in response to low hormone levels (increase sens.)
Down-regulation: decrease in response to high (decrease sens.)
Hormone Interactions at Target Cells
1) Permissiveness: one hormone cannot have full effect without binding of a second type of hormone
2) Synergism: 2+ hormones with similar effects bind target cell - amplification occurs
3) Antagonism: one hormone opposes the effect of another hormone
Duration of hormone effects on target cell
Not always immediate - can be seen after hours or days of exposure to hormone
Duration of effect varies as well
Major Endocrine Organs
1) Pituitary Gland (hypophysis) - (connected to hypothalamus - master endocrine organ)
2) Thyroid Gland - produces, secretes, stores hormones (thyroid hormone - major metabolic hormone)
3) Parathyroid Gland - parathyroid hormone (Ca2+ homeostasis)
4) Adrenal Glands - stress response, electrolyte balance
5) Pineal Gland - melatonin
6) Pancreas - glucagon and insulin
7) Gonads & Placenta - estrogens/progesterone; testosterone; placenta temporary
Regions of Pituitary Gland
1) Anterior pituitary: manufactures and releases several different hormones
2) Posterior pituitary: composed mostly of neural tissue and nerve fibers - stores and releases neurohormones produced by hypothalamus
Hormone relase of pituitary control
Controlled by Hypothalamus:
1) Action potentials from hypothalamus cause hormone relase
2) Hypothalamic hormones released into hypophyseal portal system - stimulate or inhibit
Posterior pituitary & hypothalamic hormones
1) Oxytocin - stimulant for uterine contraction, milk ejection, “cuddle hormone”
2) ADH (antidiuretic hormone) - prevents water being added to urine (maintains water content of blood)
Function of Oxytocin
Stimulates uterine contraction, milk ejection, “cuddle hormone”
Works as a neurotransmitter in the brain - promotes nurturing, couple bomding, trust, affectionate behavior
Positive Feedback!!
Control of release of ADH
Osmoreceptors in hypothalamus monitor solute concentration and release the antidiuretic hormone when solute concentration is too high
Six Anterior Pituitary Hormones
1) Growth Hormone (GH) (category 2 tropic hormone)
2) Thyroid-Stimulating Hormone (TSH) (Tropin)
3) Adrenocorticotropic Hormone (ACTH) (Tropin)
4) Follicle-stimulating hormone (FSH) (Tropin)
5) Luteinizing hormone (LH) (Tropin)
6) Prolactin (PRL) (category 2 tropic hormone)
Tropins are hormones that affect the activity of another endocrine gland
Effects of GH
metabolic: decreases glucose uptake, mobilizes fat stores - releases fatty acids to blood, increases aimo acid uptake
growth: liver, bone, skeletal muscle, etc. produce insulin-like growth factor (IGFs) in presence of GH - stimulate growth (increase nutrient uptake, formation of collagen and deposition of bone matrix
Technically not a tropin
Anterior pituitary hormone
Release and Function of TSH
Thyroid-htimulating hormone stimulated by Thyrotropin-releasing hormone (TRH)
function: stimulates developmet and secretory activity of thyroid gland
Tropin
Anterior pituitary hormone
Release and Function of ACTH
Adrenocorticotropic hormone stimulated by Corticotropin-releasing hormone (CRH)
function: stimulates developmet and secretory activity of thyroid gland
Tropin
Anterior pituitary hormone
Release and Function of FSH
follicle-stimulating hormone stimulated by Gonadotropin-releasing hormone (GnRH)
function: stimulates production of gametes
Tropin
Anterior pituitary hormone
Release and Function of LH
Lutenizing hormone hormone stimulated by Gonadotropin-releasing hormone (GnRH)
function: stimulates production of gonadal hormones
Tropin
Anterior pituitary hormone
Release and Function of PRL
Prolactin levels rise and fall with blood estrogens (rising estrogen = more PRL) - controlled by dopamine
function: stimulates milk production in breast tissue & contributes to reproductive system function
PRL increases toward end of pregnancy
Tropin
Anterior pituitary hormone
Release and Function of TH
Thyroid hormone produced depending on the presencce of iodine
Affects virtually every body cell
1) Increases metabolic rate and body heat production
2) Regulates tissue growth/development
3) Maintains blood pressure
Thyroid gland retains ~3 months normal supply of hormone
Release and Function of PTH
Decreasing blood Ca2+ levels stimulate Parathyroid hormone release by:
1) Stimulating osteoclasts to increase bone degredation
2) Enhancing Ca2+ reabsorption by kidneys
3) Activating vitamin D - increases absorption of Ca2+ from digestive system
Functional areas of the Adrenal glands
1) Adrenal Cortex - outermost region, produces 3 corticosteroids (mineralcorticoids, glucocorticoids, gonadocorticoids)
2) Adrenal Medulla - innermost region of adrenal gland, synthesize NE and Epinephrine (80% epinephrine)
Corticosteroid that regulates electrolyte concentration in ECF (esp. Na+ and K+)
Mineralcorticoids
importance:
- Na+ influences water movement - can affect blood volume and blood pressure
- K+ determines resting membrane potential - imbalance affects responsiveness of neurons
Adrenal Cortex Hormone
Corticosteroid that influences energy metabolism of cells, provides resistance to stressors
Glucocorticoids
specific types: cortisol, cortisone, corticosterone
Release stimulated by ACTH - neg. feedback
Stress affects cortisol release - CNS overrides negative feedback mechanism & more cortisol released
Effects of glucocorticoids
1) Mobilizes body stores to create more glucose
2) Provokes sympathetic nervous system
3) Excessive release causes:
- Depressed cartilage & bone formation
- Inhibits inflammation
- Depresses immune system
- Disrupts normal cardiovascular, neural, gastrointestinal functions
Gonadocorticoid release and function
Small amounts of androgens released by adrenal cortex - much less than produced by gonads
effects:
- Contribute to axillary and pubic hair development
- in females: contributes to libido & produce estrogens post-menopause
Some converted to testosterone, others to estrogen
Function of Adrenal Medulla
Synthesizes EPI and NE (80-20)
Release initiated by sympathetic nervous system
Hormones not essential for flight-or-fight response
EPI has a greater influence on metabolic activity & is a dilator of airways in lungs, whereas NE has a greater influence on blood vessel diameter
Function of Pineal Gland
Secretes melatonin
Regulating night-day cycles
Release controlled indirectly by intensity & duration of light
Pancreatic Hormones, and where they are produced
Produced in pancreatic islets:
1) Glucagon: (alpha cells) stimulates liver to break down glycogen, convert non-carbohydrate molecules to glucose, release glucose from liver cells - HYPERglycemic effect
2) Insulin: (beta cells) increases glucose uptake by body cells, inhibits glycogen breakdown, inhibits conversion of non-carbohydrate molecules to glucose
Release of insulin controlled by:
- Elevated blood glucose
- Rising blood levels of amino acids & fats
- Acetylcholine release from parasympathetic nervous system
- Any hyperglycemic hormone
Types of Diabetes Mellitus
Type 1) Autoimmune condition - insulin is not produced by the pancreas at all
Type 2) “Insulin resistance” - insulin produced & released, cells do not respond
Causes/Treatment of DM1
Caused by destruction of beta cells by immune system
Treatment: insulin shots before meals or cont. fusion pumps
If left untreated - development of vascular & neural problems
Causes/Treatment of DM2
Caused by a combination of genetics & lifestyle
Treatment: can be managed with diet and exercise
Similar complications to type 1 diabetes if not managed/treated
