Ch.16-Endocrine System Flashcards
Hormones control several major processes (5)
- Reproduction
- Growth & Development
- Mobilization of body defenses
- Maintenance of much of homeostasis
- Regulation of Metabolism
General Overview of the Endocrine Sys
- Second controlling system of the body
- Slow, but long lasting system
- Uses chemical messengers (hormones) that are released into the blood
Effects caused by Hormones (5)
- Changes in plasma membrane permeability or electrical state
- Synthesis of proteins, such as enzymes
- Activation or inactivation of enzymes
- Stimulation of mitosis
- Promotion of secretory activity
Hormone Overview (4)
- Hormones are produced by specialized cells
- Cells secrete hormones into extracellular fluids
- Blood transfers hormones to target sites
- These hormones regulate the activity of other cells
Hormones are classified chemically as… (3)
- Steroids
- Non Steroids
- Prostaglandins
Steroids
- derived from cholesterol
- lipid soluble (can pass through phospholipid membrane of target cell)
Non-steroids
- synthesized from amino acids, which includes proteins, glycoproteins, peptides, amino acids
- Not soluble
Prostaglandins
- Derived from fatty acid molecules
- found in plasma membranes of all body cells
- act locally at site of release
Mechanisms of Hormone Action (3)
- Hormones affect only certain tissues or organs (target cells or target organs)
- Target cells must have specific protein receptors
- Hormone-binding alters cellular activity within target cells
Two mechanisms in which hormones act… (2)
- Direct Gene Activation
- Second messenger system
Direct Gene Activation Explained
Also known as Steroid Hormone mechanism
- Diffuse through the plasma membrane of target cells
- Enter the nucleus
- Bind to a specific protein within the nucleus
- Bind to specific sites on the cell’s DNA
- Activate genes that result in synthesis of new proteins
Effects ranges from 45 mins to days (slow)
Second Messenger System Explained
Also known as Nonsteroid Hormone Action
- Hormone binds to a membrane receptor (Hormone does not enter the cell)
- Sets off a series of reactions that activates an enzyme
- Catalyzes a reaction that produces a second messenger molecule
- Oversees additional intracellular changes to promote a specific response
Effects ranges from seconds to minutes (fast)
Control of Hormone Release Explained
- Hormone levels in the blood are mostly maintained by negative feedback
- A stimulus or low hormone levels in the blood triggers the release of more hormone
- Hormone release stops once an appropriate level in he blood is reached
Hormonal Stimuli
- Most common
- Endocrine glands are activated by other hormones
Humoral Stimuli
- Changing blood levels of certain ions & nutrients stimulate hormone release
- Humoral indicates various body fluids such as blood and bile
Neural Stimuli
- Nerve impulses stimulate hormone release
- Most are under the control of the sympathetic nervous system
Pituitary Gland Characteristics
- Size of a pea
- Hangs by a stalk, in infundibulum hat connects it to the hypothalamus in the brain
- Protected by the sphenoid bone
Pituitary Gland Functional Lobes (2)
- Anterior pituitary–glandular tissue
- Posterior pituitary–nervous tissue
Pituitary Gland
Master endocrine gland
Six Anterior Pituitary Glands
- Growth Hormone
- Prolactin
- Thyroid-stimulating hormone (thyrotropic hormone)
- Adrenocorticotropic (ACTH) hormone
- Two gonadotropic hormones (FSH & LH)
Hormones that affect non-endocrine targets(2)
- Growth Hormone
- Prolactin
Hormones that stimulate other endocrine glands (4)
- Thyroid-stimulating hormone (thyrotropic hormone)
- Adrenocorticotropic (ACTH)
- Two Gonadotropic Hormones (FSH & LH)
- FSH=Follicle Stimulating Hormone
- LH=Luteinizing hormone
Characteristics of all anterior pituitary hormones
- Proteins
- Act through second messenger systems
- Regulated by hormonal stimuli, mostly negative feedback
Growth Hormone Characteristics
- General metabolic hormone
- Growth of skeletal muscles and long bones
- Causes amino acids to be built into proteins (growth and tissue repair)
- Causes fats to be broken down for a source of energy
- Spares glucose
Growth Hormone Disorder: Pituitary dwarfism
results from hyposecretion of GH during childhood
Growth hormone Disorder: Gigantism
Results from hypersecretion of GH during childhood
Growth Hormone Disorder: Acromegaly
Results from hypersecretion of GH during adulthood
-Facial bones enlarge tremendously, as do feet and hands
Prolactin Characteristics
- Stimulates and maintains milk production following childbirth
- Function in males is unknown
Adrenocorticotropic Hormone (ACTH)
-Regulates endocrine activity of the adrenal cortex
Thyroid-stimulating hormone (TSH)
- a.k.a. thyrotropic hormone (TH)
- influences growth and activity of the thyroid gland
Gonadotropic Hormones
-Regulate hormonal activity of the gonads
Two types of Gonadotropic Hormones (2)
- Follicle-stimulating hormone (FSH)
- Luteinizing Hormone (LH)
Follicle-stimulating hormone (FSH)
- stimulates follicle development in ovaries
- Stimulates sperm development in testes
Luteinizing hormone (LH)
- Triggers ovulation of an egg in females
- Stimulates testosterone production in males
Pituitary-Hypothalamus Relationship
- Hormonal release of many anterior pituitary hormones are regulated by releasing and inhibiting hormones produced by the hypothalamus through the hypophyseal portal system
- -hypothalamus is mind body connection
Hypothalamus produces two hormones:
- Oxytocin
- Antidiuretic hormone
Posterior pituitary gland…
storage area for hormones made by hypothalamic neurons
Oxytocin Characteristics ALSO KNOWN AS NEUROHYPOPHYSIS
- Stimulates contractions of the uterus during labour, sex and breastfeeding
- Causes milk ejection
- Labor induction;pitocin-drugs mimic oxytocin to induce labour
- Positive feedback loop
Antidiuretic Hormone (ADH) Characteristics
- Inhibits urine production by promoting water reabsorption by the kidneys
- decreased urine volume, blood volume increases
- large amounts cause vasoconstriction leading to increased blood pressure
- Drinking booze inhibits ADH secretion, results in large amounts of urine
Diabetes Insipidus is…
- hyposecretion of ADH resulting in excessive urine output.
- Always thirsty, drink huge amounts of water
Pineal Gland Characteristics
- Hangs from the roof of the 3rd ventricle of the brain
- Acts in two systems (nervous and endocrine)
- Secretes Melatonin
Melatonin Characteristics
- Helps establish the body’s wake and sleep cycles (biological clock)
- May also affect a person’s mood (serotonin is a precursor of melatonin, which is a mood altering molecule
- Seasonal Affective Disorder
Thyroid Gland Characteristics
- Found at the base of the throat (inferior to Adam’s apple)
- Consists of 2 lobes
2 hormones that are produced by Thyroid Gland
- Thyroid hormone
- Calcitonin
Thyroid Hormone Characteristics
- body’s major metabolic hormone
- composed of two active iodine-containing hormones…Thyroxine(T4), Triiodothyronine (T3)
- increases rate of metabolism of all cells
- important in process of normal tissue growth and development
- Every cell in the body is a target
Thyroid Hormone Disorder:Goiters
- Thyroid gland enlarges due to lack of iodine
- Salt is iodized to prevent goiters
Thyroid Hormone Disorder: Cretinism
- Caused by hyposecretion of thyroxine
- Results in dwarfism during childhood
- If untreated will also result in mental deficits, hair is scant, and skin is dry
Thyroid Hormone Disorders: Myxedema
- Caused by hypothyroidism in adults
- Results in physical and mental sluggishness, fatigue, poor muscle tone, low body temp, obesity, and dry skin
- Oral thyroxine can be prescribed
Thyroid Hormone Disorders: Graves’ Disease
- Hyperthyroidism
- Results in increased metabolism, heat intolerance, rapid heartbeat, weight loss, nervous and agitated behaviour, and eyes bulge.
- Treated with thyroid blocking drugs or radioactive iodine to destroy thyroid cells
Calcitonin Characteristics
- Decreases blood calcium levels by causing its deposit on bone
- Antagonistic to parathyroid hormone
- Produced by parafollicular cells of thyroid gland
- parafollicular cells are found between the follicles
Parathyroid Glands Characteristics
- Tiny masses on the posterior of the thyroid
- Secrete parathyroid hormone (PTH)=parathormone
Parathyroid Hormone Does what??
- Stimulate osteoclasts to remove calcium from bone
- Stimulate the kidneys and intestine to absorb more calcium and release into blood
- Raises calcium levels in the blood
What happens when you get hyposecretion of Parathyroid Hormone??
-decrease in blood calcium level increases neuromuscular irritability–may cause muscle spasms and convulsions
What happens when you et hyperparathyroidism??
-causes massive bone destruction called osteoporosis
Adrenal Gland Characteristics
- Sit on top of the kidneys
- Two regions: cortex & medulla
Adrenal Cortex
-Outside
Adrenal medulla
-Inside
Adrenal Cortex 3 layers
- mineralocorticoids (outermost layer)
- glucocorticoids( middle layer)
- gonadocorticoids(innermost layer)
Mineralocorticoids Characteristics
- Mainly Aldosterone, by renin angiotensin-aldosteron system
- Regulate mineral (sodium & potassium) content in blood
- Promotes water retention
- Target Organ=kidney
Kidney Tubule cells…
-reclaim/reabsorb increasing amounts of sodium ions into blood and secrete potassium ions into urine
Renin-Angiotensin-Aldosterone System Physiology
- when BP in kidneys drops below a certain level-Renin is secreted into blood
- Renin causes Angiotensinogen to be converted to Angiotension I
- Angiotension I is converted to Angiotension II by ACE
- Angiotension II circulates to adrenal cortex-stimulates secretion of aldosterone
- Aldosterone-increased absorption of sodium thus increased water rentention=BP increases
Glucocorticoids a.k.a. hydrocortisone Characteristics
- Promote normal cell metabolism
- Cortisol
- Target every cell in the body
- Help resist long-term stressors, primarily by increasing blood glucose levels
- Hyperglycemic hormones (fats/proteins are broken down by body cells and converted to glucose)
- Decrease inflammation by decreasing edema
- Released in response to increased blood levels of ACTH
Gonadocorticoids Characteristics
- Small amounts of male hormones (androgens) are secreted
- Smaller amount in women compared to men
Adrenal Cortex Disorders: Addison’s
- Results from hyposecretion of all adrenal cortex hormones
- Bronze skin tone, weak muscles, burnout, susceptibility to infection, weight loss
Adrenal Cortex Disorders: Cushing’s
- Results from a tumor in the middle cortical area of the adrenal cortex
- Buffalo hump on the upper back, muscular atrophy, edema, hypokalemia, abnormal skin pigmentation
Hormones of the Adrenal Medulla
- Epinephrine
- Norepinephrine
a. k.a catecholamines - Prepare the body to deal with short term stress (fight or flight) by:
Catecholamines prepare the body to deal with short term stress (fight or flight) by:
- Increasing heart rate, blood pressure, blood glucose levels
- Dilating small passageways of lungs
- Short term response to stress
Pancreatic Islets Characteristics
- Pancreas is a mixed gland (endocrine & exocrine)
- Produces hormones: Insulin & Glucagon
- Insulin & Glucagon are antagonists to each other that maintain blood sugar homeostasis
Insulin Characteristics (Pancreatic Islets)
- Allows glucose to cross plasma membranes into cells
- Lowers blood concentration of glucose, amino acids, fatty acids
- Decreases blood glucose levels
Glucagon Characteristics (Pancreatic Islets)
- Allows glucose to enter the blood by breaking down glycogen to glucose
- Increases blood glucose levels
Diabetes Mellitus
- blood becomes acidic
- referred to as ketosis (breakdown of fat instead of sugar)
- Type 1 requires insulin
- Type 2 insulin resistance, may require insulin
Polyuria
Excessive urination
Polydipsia
Excessive thirst
Polyphagia
Hunger
Thymus Gland Characteristics
- Located posterior to the sternum
- Largest in infants, then atrophies as we age
- Produces thymosin
Thymosin Characteristics
- Matures some types of white blood cells (T cells)
- Important in developing the immune system
Gonads (2)
- Ovaries
- Testes
Ovaries Characteristics
- Produce eggs
- Produce two groups of steroid hormone: Estrogens & Progesterone
Estrogens Characteristics
- Promote the development and maintenance of female sexual characteristics
- Along with progesterone, estrogens also promote breast development & regulate menstrual cycle
Progesterone Characteristics
- Acts with estrogen to bring out menstrual cycle
- Helps in the implantation of an embryo in the uterus
- Helps prepare breasts for lactation
- Regulation of ovarian hormone secretion is complex, but basically depends on changing levels of FSH & LH
Testes Produce….
-Produce androgens (testosterone)
Testosterone Characteristics
- Produced by Testes
- Most important androgen
- Responsible for male secondary sex characteristics
- Promotes growth & maturation of reproductive system
- Required for sperm cell production
Endocrine Function of the Placenta
- Produces hormones that maintain the pregnancy
- Some hormones play a part in the delivery
- Produces human chorionic gonadotropin (hCG) in addition to estrogen, progesterone, and others
- hCG is the hormone detected in pregnancy tests
- Other hormones: human placental lactogen and relaxin
Other Hormone Producing Tissues & Organs: Small intestine
-Cholecystokinin
Other Hormone Producing Tissues & Organs: Adipose Tissue
-Leptin
Other Hormone Producing Tissues & Organs: Heart
-atrial natriuretic peptide (antagonist to ADH and aldosterone
Endocrine Gland described…
…release their products at the body’s surface or into body cavities through ducts
Exocrine Gland described
release their products at the body’s surface or into body cavities through ducts
