Chapter 17: The Endocrine system Flashcards
Endocrine systems
sends chemical only signals
reactions are slow(secretion of hormones can take seconds to days)
long term effects
long term effects
mechanisms of endocrine systems
gap junctions
neurotransmitters
paracrine (local) hormones
hormones (strict definition)
gap junctions
pores in cell membrane allow signaling chemicals to be secreted from cell to cell
neurotransmitters
released from neuron to to travel across gap to a second cell
paracrine (local) hormones
secreted into tissue fluids to affect nearby cells
hormones
chemical messenger that is secreted into the blood stream, stimulates the response in another tissue or organ
components of the endocrine system
hormones target cells endocrine glands endocrine organs hormone producing cells in organs
target cells
will respond to the hormone only if it has a receptor specific for that hormone
they have receptors for a specific hormone
endocrine glands
these produce hormones in the endocrine system
dense capillary networks to distribute hormones
intracellular effects, alter target cell metabolism
vertebrate endocrine system functions
regulation of reproduction and metabolism
growth and development
water and electrolyte balance
communication of endocrine system
endocrine cells secrete hormones
hormones travel through blood stream
target cells absorb hormones
neuron endocrine systems
Several chemicals function as both hormones and neurotransmitters
Some hormones secreted by neuroendocrine cells (neurons)
Both systems with overlapping effects on same target cells
Both systems with overlapping effects on same target cells
true endocrine glands
Pineal gland Thyroid gland Thymus gland Parathyroid gland Adrenal glands Pituitary Gland (Hypophysis)
secondary endocrine structures
Hypothalamus GI tract Heart Pancreas Ovaries Testes Placenta Liver kidney
major organs of the endocrine system
Pineal gland hypothalamus pituitary gland thyroid gland thymus adrenal gland pancreas parathyroid glands trachea gonads
exocrine glands
- ducts carry secretion to a surface or organ cavity
- extracellular effects (food digestion)
chemical nature of hormones
peptide/ protein hormones
steroid hormones
Monoamines (biogenic amines)
types of hormone receptors
Receptors that are part of signal transduction pathways
Intracellular receptors
hypothalamus
part of the diencephalon, has nurmorus functions including endocrine control
controls all activities in the pituitary gland
has neuroendocrine cells
pituitary cells
respond to signals from the hypothalamus
neuroendocrine cells
specialized neurons that secrete hormones (not neurotransmitters!)
pituitary gland
made of two embryonically different tissues that form
Anterior pituitary gland (Adenohypophysis)
Posterior pituitary gland (Neurohypophysis)
anterior pituitary gland
made of endocrine( glandular cells)
Connected to the hypothalamus via the hypothalamic-hypophyseal portal system
Endocrine cells are controlled by releasing- and inhibiting hormones from the hypothalamic neuroendocrine (neurosecretory) cells
6 different hormones secreted from the endocrine cells:
6 different hormones secreted by the anterior pituitary gland
GH-growth hormone PRL-prolactin FSH-follicle-stimulating hormone LH-luteinizing hormone TSH-thyroid-stimulating hormone ACTH- adrenocorticotropic hormone
growth hormone - GH
released by somatotroph cells; non-specific effects on cartilage, bone, muscle and fat; causes the liver to release somatomedins (insulin-like growth factors) that stimulate bone and cartilage growth
prolactin-PRL
released by lactotroph cells; stimulates mammary gland growth and milk production; in males, makes testes more sensitive to LH.
follicle-stimulating hormone-FSH
released by gonadotrope cells; in males, helps regulate spermatogenesis; in females, helps regulate oogenesis
luteinizing hormone -LH
released by gonadotrope cells; in males, regulates the secretion of testosterone by the testes; in females, induces ovulation and the secretion of estrogen and progesterone
thyroid-stimulating hormone TSH
released by thyrotroph cells; causes the secretion of the thyroid hormones by the thyroid gland
adrenocorticotropic hormone -ACTH
released by corticotroph cells; causes the secretion of glucocorticoids from the adrenal cortex during times of stress
posterior pituitary gland
Made of neuroendocrine cells that originate in the hypothalamus and terminate in the posterior pituitary gland. Axon terminals release their hormones into the bloodstream surrounding the posterior pituitary gland
Connected to the hypothalamus via the hypothalamic-hypophyseal tract
Two different hormones secreted from the neuroendocrine cells: oxytocin OT (from paraventricular nucleus) and anti-diuretic hormone ADH (from supraoptic nucleus).
Actions of ADT
increases water reabsorption at the collecting duct of the nephrons in response to an increase in blood osmolarity (the blood is too salty, dehydration, etc.)
Action of OT
induces uterine contractions during childbirth; milk ejection during breastfeeding.
Pineal gland
und in the midbrain
Secretes hormone, melatonin (at night) and serotonin (during the day); probably involved in circadian rhythms (‘biological clock’); timing of puberty in humans
Thyroid Gland
Found on the ventral trachea
In response to TSH, two thyroid hormones are secreted: T3 triidothyronine and T4 thyroxine from follicular cells
Action of T3 and T4: maintenance of basal metabolic rate (BMR); increases oxygen consumption and cellular metabolism
Secretes hormone, calcitonin from parafollicular cells: Lowers blood Ca2+ by mineralizing bone. Moves Ca2+ from the blood and lies it down on bone. Calcitonin is the antagonistic hormone to parathormone.
Parathyroid glands
Typically four small glands embedded in the surface of the thyroid glands
Secretes the hormone, parathyroid hormone PTH or parathormone in response to hypocalcemia (low blood calcium)
Antagonistic action to calcitonin: Rises blood Ca2+ by demineralizing bone, increasing intestinal Ca2+ absorption, and inhibiting urinary Ca2+ excretion.
thymus gland
Located in the mediastinum
Secretes a family of thymic hormones that controls the development of T lymphocytes
Islets of Langerhans cells of the pancreas
Alpha cells
Beta cells
Delta cells
Alpha cells
secrete hormone, glucagon (a catabolic hormone)
Actions of glucagon
it’s released in response to a drop in blood glucose (like during fast, between meals)
Liver breaks down glycogen into glucose subunits
Glucose released into the bloodstream
Blood glucose levels rise
Beta cells
Beta cells secrete hormone, insulin (an anabolic hormone)
action of insulin
antagonistic to those of glucagon: it’s released in response to a rise in blood glucose (during a meal)
Stimulates glucose uptake by all body cells except the brain
In liver, glucose is converted to glycogen
Increases fat uptake by adipose tissue
Increases amino acids uptake by muscle
delta cells
secrete, somatostatin
Antagonistic hormone to GH
The adrenal glands
found on left and right kidneys
Made of two embryonic distinct tissue layers
Adrenal Medulla
Adrenal Cortex
Adrenal Medulla
Secretes hormones called catecholamines (epinephrine, norepinephrine) from chromaffin cells
functions of catecholamines
released during a ‘fight-or-flight’response; released in response to neuronal signals from the sympathetic nervous system
increase blood flow to the heart, brain and skeletal muscle and increase metabolic rate.
released during short-term stress to the body
adrenal medulla
Produces a family of steroid-based hormones called the corticosteroids: glucocorticoids, mineralocorticoids, androgens
Actions of the Glucorticoids
released during long-term stress to the body
Main effect is on glucose metabolism
Stimulates glycogen breakdown and glucose release from the liver
Stimulates gluconeogenesis: the synthesis of ‘new’ glucose from non-carbohydrate sources (like proteins and fats)
More glucose is moved to the blood for fuel during stress
Suppresses inflammatory response and immune response
Glucocorticoids are released in response to ACTH from the anterior pituitary
Actions of the Mineralocorticoids
Main effect is sodium reabsorption at the distal convoluted tubules in the nephrons (also potassium excretion)
Systemic effect is increased blood volume and pressure
Actions of the Androgens (male sex hormones) and small amounts of estrogens and progesterone
Maintenance of secondary sexual characteristics
Sex drive
The Gonads
the testes and ovaries
Produce steroid-based sex hormones
Gonadal hormones released in response to FSH and LH from the anterior pituitary gland
Ovaries produce two types of ovarian hormones: estrogens and progesterone
Testes produce a testicular hormone: testosterone.
Sex hormones regulate primary (specific to the genitalia) and secondary (changes to other body parts) sexual characteristics
