1. endocrine system Flashcards
What is the definition of a gland?
A gland is an organ that releases a secretion. (Hormone, enzyme, etc.)
What are the two types of glands?
Exocrine gland and endocrine gland
Describe an exocrine gland?
A gland that secretes a substance onto the surface of an epithelium. (Ex, sudoriferous (sweat) glands, salivary glands, pancreas (digestive enzymes for lumen of small intestine))
Describe an endocrine gland
A gland that secretes HORMONES into the insterstitial fluid that enters the BLOODSTREAM (ex, pituitary gland, thyroid gland, adrenal gland)
What is a hormone?
A molecule (chemical messenger) that is released in one part of the body and regulates the activity of another part of the body (travels through the bloodstream).
What makes it possible for a hormone to act on a certain body part?
Each hormone has its own receptors in the target organs (ex, adrenal gland has receptors for the hormone adrenocorticotropic hormone)
What are the two types of hormone structures?
STEROID hormones: lipid based (ex, testosterone, estrogen, progesterone)
AMINE, PEPTIDE, PROTEIN hormones: all PROTEIN based (ex, epinephrine, ADH, Insulin)
What are the 6 functions of hormones in the body?
- Stimulate secretions by exocrine glands (E.g. Prolactin from pituitary gland
stimulates milk secretion from mammary glands) - Stimulate secretion of hormones from other endocrine glands (E.g. TSH from
pituitary stimulates secretion of thyroid hormones) - Regulate metabolic reactions and changes in body’s biochemistry (E.g. Insulin from
pancreas stimulates glycogenesis) - Regulate muscle contraction and nervous stimulation (E.g. Epinephrine from
adrenal gland increases heart rate) - Regulate growth and development (E.g. Thyroid hormone accelerate body growth
and development - Regulate reproduction (E.g. Estrogen from the ovaries regulate the menstrual cycle)
What is the function of the hypothalamus
The hypothalamus acts as the control centre for homeostasis that targets the pituitary gland.
How is the pituitary gland divided?
The pituitary gland is divided into the ANTERIOR and POSTERIOR glands
What are the 8 types of hormones from the hypothalamus?
5 releasing hormones (stimulates release of another hormone)
1 inhibitory hormone (stops production of a hormone)
2 hormones produces in the hypothalamus and secreted by the posterior pituitary
What is the difference between the anterior and posterior pituitary?
The posterior pituitary cannot create hormones, it only stores and releases hormones made by the hypothalamus.
The anterior pituitary can create hormones.
What connects the anterior pituitary and the hypothalamus?
The hypophyseal portal systems connects the anterior pituitary and the hypothalamus.
The hypophyseal portal systems refers to blood vessels in the brain that connect the hypothalamus and pituitary as hormones can only travel through blood.
What do the releasing hormones of the hypothalamus act on?
The releasing hormones of the hypothalamus acts on the ANTERIOR pituitary
What are the 5 releasing hormones?
- Adrenocorticotropic hormone releasing hormone
- Thyroid stimulating hormone releasing hormone
- Gonadotropin releasing hormone
- Growth hormone releasing hormone
- Prolactin releasing hormone (pregnancy only)
Describe the pathway from the hypothalamus to the production of cortisol
- Hypothalamus releases Adrenocorticotropic hormone releasing hormone
- ACH-RH stimulates the anterior pituitary gland.
- The anterior pituitary releases adrenocorticotropic hormone
- Adrenocorticotropic hormone stimulates the adrenal cortex located on the adrenal glands
- The adrenal cortex produces cortisol
Describe the pathway from the hypothalamus to development of sex organs
Hypothalamus releases GnRH that stimulates the anterior pituitary gland that releases TWO HORMONES: FSH + LH.
FEMALE: FSH + LH stimulates the ovaries and creation of eggs (oogenesis) to increase growth of organs, release eggs, estrogen and progesterone
MALE: FSH + LH stimulate the testes to increase growth or organs, creation of sperm (spermatogenesis) and release of testosterone
What is the inhibitory hormone made by the hypothalamus and its function?
Prolactin inhibiting hormone (PIH) – inhibits the levels of prolactin released from the anterior pituitary to stop lactation (normal conditions)
What are the hormones secreted from the posterior pituitary and their function?
- Oxytocin: causes contraction of the uterus which is important during childbirth and the release of milk (milk ejection reflex, works with prolactin) during breastfeeding
- Antidiuretic hormone: increases water absorption in the kidney (released at all times, amount deprends on body conditions)
What is the role of Growth Hormone (GH) in the body?
GH promotes physical growth, increases metabolism, cell size, and bone and muscle growth. In adults, it helps maintain bone and muscle mass and promotes tissue repair.
What are the conditions resulting from hyposecretion and hypersecretion of Growth Hormone?
• Hyposecretion: Childhood pituitary dwarfism (stunted growth due to premature closure of epiphyseal plates).
• Hypersecretion: Gigantism (abnormally large size in children) and Acromegaly (thickening of bones and soft tissues in adults).
What is the effect of ADH (Antidiuretic Hormone) hyposecretion?
It leads to diabetes insipidus, characterized by excessive urination (polyuria) and extreme thirst (polydipsia).
How does thyroid hormone (thyroxine) influence the body?
It increases basal metabolic rate, breaks down fats and carbohydrates, affects protein metabolism, and is involved in nervous and skeletal system development.
What is the function of Calcitonin?
Calcitonin lowers blood calcium and phosphate levels through the regulation of calcium ion levels.
What is the role of Parathyroid Hormone (PTH)?
PTH increases blood calcium levels by stimulating osteoclasts to break down bone and releasing calcium and phosphorus into the blood.
What are the three zones of the adrenal cortex and their functions?
• Outer zone: Produces mineralocorticoids (e.g., aldosterone for sodium and water reabsorption).
• Middle zone: Produces glucocorticoids (e.g., cortisol, which responds to stress and increases sugar storage).
• Inner zone: Produces androgens, which contribute to the development of secondary sex characteristics.
What are the symptoms of Cushing’s Syndrome?
Redistribution of body fat, facial swelling, bruising, poor wound healing, hyperglycemia, hypertension, and increased thirst and urination.
How does cortisol impact the body during stress?
Cortisol increases muscle metabolism, boosts gluconeogenesis (production of glucose), and plays a key role in the body’s stress response.
What are the effects of insulin and glucagon in blood glucose regulation?
• Insulin: Lowers blood glucose by increasing cellular uptake, glycogen synthesis, and fat storage.
• Glucagon: Increases blood glucose by promoting glycogen breakdown and gluconeogenesis.
What phases are involved in the stress response?
• Alarm Phase: Triggered by the nervous system (fast and short-lived).
• Resistance Phase: Activated by the endocrine system (long-lasting but slower).
• Exhaustion Phase: Organ failure due to prolonged hormone activity.
How do the parathyroid hormone and calcitonin regulate blood calcium levels?
• Parathyroid hormone increases calcium by promoting osteoclast activity and calcium absorption.
• Calcitonin lowers calcium by stimulating osteoblast activity and decreasing osteoclast activity.
What is the difference between Type 1 and Type 2 Diabetes Mellitus?
• Type 1: Autoimmune destruction of beta cells, leading to insulin loss.
• Type 2: Insulin resistance, where cells no longer respond to insulin.
What hormones are produced by the adrenal medulla and their effects?
Epinephrine (adrenaline) and norepinephrine (noradrenaline), which increase blood pressure and direct blood flow to essential organs during stress.
What are the primary and secondary sex hormones produced by ovaries and testes?
• Ovaries: Estrogen and progesterone, responsible for female sex characteristics and reproductive functions.
• Testes: Testosterone, responsible for male sex characteristics and spermatogenesis.
What is the role of the thymus in the immune system?
The thymus produces thymosins, which are involved in the development of T-cells (lymphocytes) critical for the immune response.
What is the role of the pineal gland?
The pineal gland produces melatonin, which regulates sleep patterns and can influence hormonal rhythms like luteinizing hormone.
What is the function of Epinephrine (Adrenaline)?
Epinephrine increases heart rate, dilates bronchial airways, and redirects blood flow to essential organs during stress (fight or flight response).
What is the function of Norepinephrine (Noradrenaline)?
Norepinephrine reduces blood flow to the intestines and skin while increasing blood flow to vital organs like the heart and brain during stress.
