Endocrine System Lecture Flashcards
31/10/24
What is the role of hormones?
Hormones influence metabolic activity by secretion into the bloodstream.
Involved in: cellular metabolism, growth and development, sexual development, homeostasis.
What is an endocrine gland?
A ductless structure that’s rich in blood supply, responsible for hormone secretion.
What is an exocrine gland?
Secretion of hormones externally onto an epithelial surface. e.g. tongue secretes saliva and the skin secretes sebum.
What are the 3 types of hormone?
Amino acid derived, steroids, protein
Describe amino acid derived hormones
Modified tyrosine e.g. thyroid hormone
Describe steroid hormones
Synthesised from cholesterol, so they’re lipid soluble.
Able to readily cross the plasma membrane.
Require specific transporter proteins in the blood.
Describe protein hormones
They are water soluble and have a short half life.
They initiate cellular change and vary in size.
Where do hormones act?
They bind to receptors that can either be on the cell membrane of a surface (extracellular) or they can be intracellular.
What are the different types of hormone activity?
Episodic, Diurnal and Constant
What is episodic hormonal activity?
Release of hormones is in response to physiological demand
What is diurnal hormonal activity?
Predictable pattern of hormonal release over 24 hours.
What is constant hormonal activity?
A fairly constant blood hormone concentration for normal physiological function.
What are the different types of hormonal stimuli?
Humoral, Neuronal and Hormonal.
What is humoral stimulus?
Circulating molecules in the blood
What is a neuronal stimulus?
A stress response, for example, the sympathetic nervous system.
What is a hormonal stimulus?
Response to hormones secreted by other glands.
What is the hypothalamus?
It is responsible for controlling hormone release from the anterior lobe of the pituitary gland. It releases the growth hormone releasing hormone, and the growth hormone inhibiting hormone.
It also synthesises oxytocin/antidiuretic hormone which is stored in the posterior lobe of the pituitary gland.
What is the pituitary gland?
Divided into 2; anterior and posterior.
Anterior or adenohypophysis. It releases growth hormone (GH), thyroid stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), FSH, LH, and prolactin.
The posterior is made of mainly neural tissue, and stores ADH and oxytocin.
What is the thyroid gland?
Made of 2 lobes surrounding the trachea.
In the visceral compartment of the neck surrounded by the pretracheal fascia.
Rich blood supply and innervated PNS/SNS
Secretes thyroxine.
What is the function of thyroxine?
Regulates the rate of metabolism, energy use, protein production, growth and development, and the sensitivity of cells to other hormones.
What is hyperthyroidism?
Too little thyroid hormones, so less metabolism, and an increase in fatigue and weight gain.
What is hypothyroidism?
Graves disease: over stimulation of thyroid hormones - leads to weight loss.
What is the parathyroid gland?
Secretes parathyroid hormone - responsible for calcium homeostasis.
Osteoclasts break down bone which leads to an increase in blood calcium levels.
Inactive vitamin D is converted to active vitamin D which is used for calcium absorption.
What is the adrenal/suprarenal gland?
Comprised of 2 sections, the cortex, made of glandular tissue and the medulla, made of sympathetic NS derived from the neural crest.
Medulla produces epinephrine, norepinephrine and dopamine.
The cortex produces 3 main corticosteroid hormones (steroid hormones):
The Zone Glomerulosa produces mineralocorticoids which ensures homeostasis of Na+/K+
The Zona fasciculata produces glucocorticoids, for example, cortisol, responsible for energy metabolism and glucose availability.
The Zona reticularis produces gonadocorticoids which are sex steroids.
What is the function of the pancreas?
Endocrine and exocrine gland. Major role in glucose homeostasis.
‘Islets of Langerhans’ cells produce glucagon and insulin.
