Endocrine System Flashcards
➔ 2nd control system of the body (Nervous System is 1st)
➔ Uses chemical messengers (hormones) released in bloodstream
Endocrine system
Fast-control system
Organized structure
Nervous system
Slow-control system
No structure
Endocrine system
are chemical messengers that regulate bodily functions by acting on specific target cells or organs.
Hormones
A given hormone affects only specific tissues or organs, known as
target cells or target organs.
Hormones play a key role in reproductive health, and imbalances can cause issues like infertility.
reproduction
Influences increase in height, size, and volume.
Growth
Specialization of body parts, such as breast
Development
Hormones help activate the body’s defense mechanisms.
Body defense mobilization
Hormones maintain balance in water levels, body temperature, and metabolic processes.
Regulation of metabolism
Proteins, Peptides, and Amines
Amino-acid based protein
Cholesterol-derived
Steroid
Derived form highly active lipids
Prostaglandins
Hormones can initiate by reversing charges in the plasma membrane.
action potentials
Irregular menstruation, abnormal hair growth in women, mood swings, and temperature regulation issues.
Physical symptoms of hormonal imbalance
Hormonal issues can affect both mental and physical health, causing issues with body temperature, mood, and overall function.
Health impact of hormonal imbalance
→ Used by steroid hormones and
thyroid hormones
→ KeyPoint: Direct gene activation
does not require receptor proteins on the cell membrane; the hormone directly initiates protein synthesis inside the cell.
Direct Gene Activation
Steps of direct gene activation
Diffusion, nuclear entry, binding, gene activation, transcription, protein synthesis
→ Used by protein and peptide hormones
→ Key Point: The second messenger
system requires receptor proteins and involves a more complex, multi-step process compared to direct gene-activation
Second messenger system
steps of second messenger system
Binding, receptor activation, second messenger production, intracellular changes
→ Hormone levels are primarily controlled by the negative feedback mechanism, which helps maintain homeostasis within the body.
→ It occurs when a change in a physiological variable triggers a response that counteracts the initial change.
negative feedback
When calcium levels are low, the endocrine system signals to release hormones that increase calcium levels in the bloodstream.
Calcium regulation (negative feedback)
High Blood Sugar: After consuming a large amount of carbohydrates, blood sugar levels rise, potentially harming tissues and organs. The body responds by storing excess sugar in the liver.
Restoration of Balance: If blood sugar levels later drop, the body releases stored sugar to restore normal levels.
Blood sugar regulation (negative feedback)
→ Most common category of stimulus
→ Endocrine organs are activated by other hormones
1. The hypothalamus stimulates
the anterior pituitary to release hormones like thyroid-stimulating hormone (TSH), which activates the thyroid gland to produce thyroid hormones.
Hormonal stimuli
→ It is triggered by changing blood
levels of specific ions and nutrients,
stimulating hormone release.
1. When blood calcium levels drop, the parathyroid glands release parathyroid hormone (PTH) to increase calcium levels.
2. Conversely, when blood calcium levels are high, the thyroid gland releases calcitonin, which lowers calcium levels.
Humoral stimuli
→ It involves hormone release stimulated directly by nerve fibers, primarily controlled by the sympathetic nervous system.
→ Most are under the control of the sympathetic nervous system
★ In response to a stressful situation (e.g., danger), the brain activates the adrenal glands to release adrenaline, preparing the body for a “fight or flight” response.
Neural stimuli
→ It produces and inhibiting hormones
→ Produces hormones that control the pituitary gland, including:
○ Oxytocin: Induces uterine
contractions and milk ejection.
○ Antidiuretic Hormone (ADH):
Regulates water balance by
reducing urine production.
Hypothalamus
○ Proteins (or peptides)
○ Act through
second-messenger system
○ Regulated by hormonal stimuli
○ Mostly negative feedback regulation
Hormones of the hypothalamus
→ AKA Somatotropin
→ General metabolic hormone
→ Promotes skeletal muscle and bone growth, determines body size, converts amino acids into proteins, and causes fats to be broken down for a source of energy
→ Active until age 18 for females, and up to age 21 for males.
→ Dietary Recommendations: For optimal muscle development, a diet rich in protein (e.g., meat, soy, tofu) is encouraged.
Growth hormone (GH)
→ Glandular Tissue
→ Two hormones affect non endocrine targets:
○ Growth Hormone
○ Prolactine
→ Four are tropic hormones:
○ Follicle-stimulating hormone
(FSH)
○ Luteinizing hormone
○ Thyrotropic hormone
○ Adrenocorticotropic hormone
Anterior pituitary
Caused by low levels of growth hormone, leading to impaired growth and development
Dwarfism
→ Stimulates and maintain milk production in the mammary glands following childbirth
→ Unknown function in males
→ Levels increase significantly following childbirth, which can lead to lactation issues.
Prolactine
→ Stimulates follicle development in ovaries
→ Important for egg maturation in females.
→ Stimulates sperm development in
testes
Follicle-stimulating hormone (FSH)
→ Promotes ovulation and the production of sex hormones
→ In females, it triggers ovulation; it stimulates testosterone production in the testes.
Luteinizing hormone (LH)
→ AKA thyroid-stimulating hormone
→ Influences growth and activity of thyroid gland
→ Stimulate the thyroid gland to
produce thyroid hormones, which regulate metabolism and calcium levels in the body
Thyrotropic hormone (TH)
→ Regulate endocrine activity of the
adrenal cortex
→ ACTH stimulates the adrenal glands to release different hormones, including glucocorticoids (like cortisol), which are essential for stress response, metabolism, and immune response regulation.
Adrenocorticotropic hormone (ACTH)
→ Nervous tissue
→ Does not make the hormones it releases
→ Stores hormones made by the thalamus
→ Two hormones released: Oxytocin and ADH
Posterior pituitary
Aids in contraction during labor and milk release.
Oxytocin
Inhibits urine production, promoting water retention, affecting kidney tubules; Urine ↑; BP ↓.
Antidiuretic hormone
Hangs from the roof of the 3rd ventricle of the brain. Produces melatonin.
Pineal gland
Regulates the sleep-wake cycle, with higher levels at night to promote sleep
Melatonin
Peak time for melatonin
10PM - 2AM (Golden hours)
Found at the base of the throat, inferior to the Adam’s apple. Consists of two lobes and a connecting isthmus. Follicles are hollow structures that store colloidal material. Produces two hormones: Thyroid hormone and calcitonin
Thyroid gland
Major metabolic hormone. Controls rate of glucose oxidation to supply body heat and chemical energy Needed for tissue growth and development Composed of two active iodine-containing hormones: Thyroxine (T4) and Calcitonin
Thyroid hormone
Secreted by thyroid follicles.
Thyroxine (T4)
Formed from T4 at target tissues.
Triiodothyronine (T3)
Lowers blood calcium levels by
stimulating osteoblasts to create bone, reducing calcium in the bloodstream (hypoglycemic effect). Produced by parafollicular cells located between the follicles.
Calcitonin
Build bones.
Osteoblast
Break down bones
Osteoclast
Maintain bones
Osteocyte
When you have low blood pressure, ______ prompts kidney to retain sodium and water, increasing blood pressure
Aldosterone
During high blood pressure, ____ from the heart inhibits aldosterone, reducing sodium and water retention
Atrial natriuretic peptide (ANP)
→ Tiny masses on the posterior of the thyroid
→ Secretes parathyroid hormone (PTH)
→ Most important regulator of Ca2+
→ Bone Impact: Stimulates osteoclasts to break down bone tissue, releasing calcium into the blood (hypercalcemic effect).
→ Additional Actions: Promotes calcium absorption from the kidneys and intestines to maintain adequate blood calcium levels.
Parathyroid glands
→ Located in the upper thorax, posterior to the sternum
→ Largest in infants and children
→ Decreases in size throughout adulthood
→ Produces thymos in hormone
★ Matures some types of WBCs
★ Important in developing the immune system
Thymus
→ Outer glandular
→ Region has three layers:
★ Mineralocorticoids
★ Glucocorticoids
★ Sex Hormones
Adrenal cortex
→ Inner neural
→ Tissue regions
→ Produces two similar hormones
(catecholamines)
★ Epinephrine (adrenaline)
★ Norepinephrine (noradrenaline)
→ Hormones prepare the body to deal with short-term stress (fight-or-flight) by:
★ Increasing heart rate, BP, and blood sugar levels
★ Dilating small passageways of lungs
Adrenal medulla
→ Mainly aldosterone
→ Produces in outer adrenal cortex → Regulate mineral (salt) contentin
blood (Na+ and K+)
→ Regulate water and electrolyte balance
→ Target organ is the kidney
Mineralocorticoids
→ Function: Regulates blood minerals, impacting water balance and blood pressure.
→ Target: Kidneys, to increase sodium and water reabsorption.
→ Regulation: Triggered by low BP via renin-angiotensin mechanism; inhibited by atrial natriuretic peptide (ANP) from the heart.
Mineralocorticoids
→ Function: Controls long-term stress by increasing blood glucose and providing an anti-inflammatory effect.
→ Trigger: ACTH from the anterior pituitary.
Glucocorticoids
→ Most of the hormones produced are androgens (male hormones), HO but some estrogens female hormones) are also formed
→ Function: Small levels of androgens and estrogens are produced continuously.
★ Androgens ★ Estrogens
Sex hormones
→ Function: Short-term stress response (fight-or-flight), increasing heart rate, blood pressure, and glucose.
→ Effects: Enhances alertness and
physical readiness.
Epinephrine and Norepinephrine
- Increased heart rate
- Increased blood pressure
- Liver converts glycogen to glucose
and releases glucose to blood - Dilation of bronchioles
- Changes in blood flow patterns,
leading to increased alertness and decreased digestive and kidney activity
Short-term stress response
- Retention of Sodium and water by kidneys
- Increased blood volume and blood pressure
- Protein and fast converted to glucose or broken down for energy
- Increased blood sugar
- Suppression of immune system
Long-term stress
→ Located in the abdomen, close to stomach
→ Mixed gland, with both endocrine and exocrine functions
Pancreas
Produces digestive enzymes.
Exocrine function
Regulates blood sugar levels by producing hormones
Endocrine funciton
→ Islets of Langerhans
→ Clusters of cells within the pancreas responsible for hormone production
Pancreatic Islets
→ Produced by: Beta Cells in the Islets of Langerhans
→ When Released: When blood sugar levels are high (e.g., after eating
carbohydrates).
→ Function: Lowers blood sugar by
increasing glucose uptake and metabolism in body tissues.
→ Effect: Hypoglycemic–reduces
blood glucose levels and promotes glycogen storage in the liver for later use.
Insulin
→ Antagonists hormones that maintain blood sugar homeostasis
→ Produced By: Alpha cells in the Islets of Langerhans.
→ When Released: When blood sugar levels are low (e.g., after fasting or prolonged physical activity).
→ Function: Raises blood sugar by stimulating the liver to convert stored glycogen to glucose.
→ Effect: Hyperglycemic – increases blood glucose levels to maintain homeostasis.
Glucagon
Reproductive glands that produces sex cells and sex hormones
Gonads
Male gonad
Testes
Female gonad
ovaries
→ Location: Suspended outside the
pelvic cavity within the scrotum.
→ Function: Produces sperm cells and androgens, primarily testosterone, the primary male sex hormone.
→ Hormone: Testosterone
testes
→ Location: Pelvic cavity.
→ Function: Produces eggs (ova) and
two main steroid hormones—estrogen and progesterone.
→ Hormones: Estrogen and Progesterone
Ovaries
→ Responsible for adult male secondary sex characteristics, such as increased muscle mass, body hair, and deepening of the voice.
→ Promotes growth and maturation of the male reproductive system.
→ Essentialforspermatogenesis (sperm production) and spermiogenesis (maturation of sperm cells).
Testosterone
→ Stimulate the development of
secondary female characteristics,
such as wider hips
→ Mature the female reproductive
→ organs.
→ With Progesterone:
○ Promote breast development
○ Regulate menstrual cycle
Estrogen
→ Acts with estrogen to bring about menstrual cycle
→ Prepares the uterine lining (endometrium) for potential
pregnancy.
→ Helps prepare breasts for lactation
Progesterone
→ Stimulates ovarian follicle
development, thickening follicle layers around the egg, and leading to
the formation of a mature follicle (Graafian follicle)
Follicle-stimulating hormone (FSH)
Triggers ovulation, the release of the
mature egg from the follicle, allowing it to be ready for fertilization.
Luteinizing hormone (LH)
After ovulation, the Graafian follicle
transforms into the corpus luteum, which produces progesterone to prepare the uterus for potential pregnancy.
Corpus luteum formation
■ Progesterone: Continues to
support the pregnancy by
thickening the endometrium.
■ Human Chorionic Gonadotropin (HCG): Produced by the placenta around the 8th week; maintains the corpus luteum, ensuring ongoing progesterone production. (Detected by pregnancy tests.)
If fertilization occurs
■ Progesterone Levels Drop: The
corpus luteum deteriorates,
lowering progesterone levels.
■ Menstruation: Without
sufficient progesterone, the endometrial lining collapses and sheds, marking day 1 of the new menstrual cycle.
If no fertilization occurs
Produced by the placenta around the 8th week; maintains the corpus luteum, ensuring ongoing progesterone production. (Detected by pregnancy tests.)
Human chorionic gonadotropin (HCG)
→ Produces hormones that maintain pregnancy
→ Some hormones play a part in delivery
Placenta
Helps sustain pregnancy by preventing endometrial collapse and embryo loss.
ACDLE
Produced to support pregnancy maintenance.
Human chorionic gonadotropin (HCG)
Prepares breasts for lactation.
HPL (Human placental lactogen)
Relaxes pelvic ligaments and pubic
symphysis for easier childbirth; this hormone is responsible for pregnancy-related pelvic discomfort.
Relaxin
→ Chemical Composition: Derived from fatty acids.
→ Source: Plasma membranes of most body cells.
→ Stimulus: Local irritation, hormones, etc.
→ Target/Effects: Act locally, causing
vasoconstriction, uterine muscle stimulation (menstrual pain/labor), inflammation, pain, blood pressure increase, digestive secretion enhancement, and fever.
Prostaglandine (PGs)
→ Chemical composition: Peptide.
→ Source: Duodenum (small intestine).
→ Stimulus: Food, especially fats.
→ Target/effects: Stimulates gastric glands and stomach motility.
Intestinal Gastrin
→ Chemical composition: Peptide.
→ Source: Duodenum
→ Stimulus: Food.
→ Target/effects:
Pancreas: Releases bicarbonate-rich juice
Liver: Reduces secretion and motility
Secretin
→ Chemical composition: Peptide.
→ Source: Duodenum
→ Stimulus: Food.
→ Target/effects:
Pancreas: Releases enzyme-rich juice
Gallbladder: Expels stored bile
Cholecystokinin (CCK)
→ Chemical composition: Glycoprotein.
→ Source: Kidneys
→ Stimulus: Hypoxia (low oxygen).
→ Target/effects: Bone marrow stimulation for red blood cell production
Erythropoietin
→ Chemical composition: Steroid.
→ Source: Kidneys (activated from epidermal provitamin D).
→ Stimulus: Parathyroid hormone (PTH).
→ Target/effects: Intestine— enhances dietary calcium absorption
Active Vitamin D3
→ Chemical composition: Peptide.
→ Source: Heart
→ Stimulus: Atrial stretching.
→ Target/effects:
Kidneys: Inhibits sodium reabsorption and renin release.
Adrenal Cortex: Reduces aldosterone, lowering blood volume and pressure.
Atrial Natriuretic Peptide (ANP)
→ Chemical composition: Peptide.
→ Source: Adipose tissue
→ Stimulus: Fatty foods.
→ Target/effects: Brain— suppresses appetite and increases energy expenditure
Leptin
→ Chemical composition: Peptide.
→ Source: Adipose tissue
→ Stimulus: Unknown.
→ Target/effects: Antagonizes insulin action in fat, muscle and liver
Resitin
