Human Endocrine System Flashcards

Flashcards covering the anatomy, hormones, functions, and disorders of the human endocrine system based on the matric Life Sciences Matric notes.

What is the primary difference between endocrine and exocrine glands?

Endocrine glands secrete hormones directly into the bloodstream allowing for faster action, while exocrine glands secrete substances like sweat, tears, and digestive enzymes into ducts onto body surfaces.

How is 'homeostasis' defined in the context of the human body?

Homeostasis is the maintenance of a constant internal environment, specifically the tissue fluid and blood, to ensure cells function properly.

What are the three components of a negative feedback system?

1. A receptor that detects change from a set point; 2. A control centre (usually the brain) that activates a corrective mechanism; 3. An effector that responds to and corrects the change.

Contrast negative feedback with positive feedback.

Negative feedback occurs when a change triggers a response that reverses the initial change (e.g., blood glucose), while positive feedback triggers a response that causes more change in the same direction (e.g., lactation, blood clotting, or uterine contractions).

What is the function of Anti-Diuretic Hormone (ADH) and where is it stored?

ADH increases the permeability of the collecting ducts in the kidney to increase water reabsorption (osmoregulation) and increases blood pressure via vasoconstriction; it is produced in the hypothalamus and stored in the posterior pituitary gland.

Why is the pituitary gland referred to as the 'master gland'?

It produces hormones that regulate other endocrine glands and various vital bodily functions.

Which hormone is secreted by the anterior lobe of the pituitary to target the thyroid gland?

Thyroid-stimulating hormone (TSH).

What mineral is required for thyroxin to become active, and what are its main functions?

Iodine is required. Thyroxin's functions include increasing metabolic rate, heart rate, and nervous system activity, as well as playing a role in organ growth and foetal brain development.

What are the symptoms and common causes of Hyperthyroidism?

Symptoms include weight loss, increased appetite, sweating, anxiety, and exophthalmos (protruding eyeballs); causes include Goitre, tumours, or Grave's Disease.

Compare the effects of Hypothyroidism in adults versus children.

In adults it causes Myxoedema (tiredness, weight gain, mental sluggishness); in children it causes Cretinism (stunted growth, mental retardation, and failure to reach sexual maturity).

What is the result of over-secretion of Growth Hormone (GH) in adults?

Acromegaly, where bones get thicker (enlarged hands, feet, and jaw) because bone epiphyses have already fused, preventing an increase in height.

Which specific cells in the pancreas produce insulin and glucagon?

Beta cells of the Islets of Langerhans produce insulin, and alpha cells produce glucagon.

How does insulin lower blood glucose levels?

It helps cells take in glucose for cellular respiration and causes the liver and muscles to convert glucose into glycogen for storage.

What is the normal blood glucose concentration range?

$3,5 - 5,5\,mmol/litre$ of blood.

Distinguish between Type I and Type II Diabetes.

Type I is an autoimmune disease where the immune system destroys beta cells (lack of insulin); Type II is a lifestyle disease where body cells resist or don't respond properly to insulin.

List four effects of Adrenalin (Epinephrine) on the body.

Increasing heart rate, increasing rate and depth of breathing, dilating pupils, and stimulating the conversion of glycogen to glucose.

What are the primary functions of Cortisol?

Increasing blood sugar through gluconeogenesis, suppressing the immune system, aiding metabolism, and decreasing bone formation.

What roles do FSH and LH play in the female reproductive system?

FSH stimulates the maturation of the Graafian follicle and oestrogen production; LH causes ovulation and stimulates the formation of the corpus luteum for progesterone production.

What roles do FSH and LH play in the male reproductive system?

FSH stimulates Sertoli cells for sperm production; LH (ICSH) stimulates Leydig cells to produce testosterone.

How is infertility defined?

The inability to achieve a pregnancy after $12$ months or more of regular, unprotected sexual intercourse.

What are the anabolic and androgenic effects of testosterone?

Anabolic effects include building muscle, promoting bone density, and recovery; androgenic effects include masculine traits like voice deepening and body hair growth.

What is the danger of chronic elevated cortisol levels in athletes?

It leads to a state of constant muscle breakdown and suppressed immune function, increasing the risk of injury.

Identify the three major stress hormones referenced in the text.

Cortisol, adrenaline, and thyroid hormones (thyroxin and $T_3$).