Endocrinology Flashcards
Describe the roles of the endocrine system
- Allows communication between organs; secretion and transport of hormones
- Maintenance of the internal environment and homeostasis eg blood glucose regulation
- Involved in many important physiological function such as metabolism, sexual function and reproduction, energy and water balance, growth and development, stress response, sleep-wake cycles
Outline how the endocrine system communicates
- Consists of various glands
- Communicate through chemical messengers (hormones) in the blood
- Communication is slower and lasts longer than the nervous system
What are the roles of the hypothalamus and pituitary gland, endocrine glands and hormones?
- Hypo and pituitary gland - form the H-P axis, main regulator of downstream glands
- Endocrine glands - secrete hormones to initiate actions within cells
- Hormones - chemical messengers, responsible for initiating change within target cells
Name glands of the endocrine system and in short their function
- Pituitary gland - master gland
- Pancreas - blood glucose
- Adrenal glands - stress response, blood pressure and heart rate
- Testes and ovaries - sexual function and reproduction
- Thyroid - metabolism and calcium homeostasis
Describe the hypothalamus role in the hypothalamus-pituitary axis
- Not a gland, but the overall master of the system
- Recieves information from the body (feedback)
- Homeostatic control and behaviour regulation - controls pituitary gland secretion
- Provides important link between nervous system and endocrine system
Describe the pituitary glands role in the hypothalamus-pituitary axis
- Releases hormones –> ‘tropic factors’
- Tropic factors regulate the activity of other glands eg adrenal gland to release cortisol
Outline the overall process of how the H-P axis works
- Releasing factors such as growth hormone-releasing hormone from the hypothalamus activate cells within pituitary gland
- Pituitary gland cells release ‘tropic factors’ which act on target organs/tissues
Describe hormones
- Chemicals produced and released by cells/glands within the body
- Act as ‘messengers’
- Bind to specific cells with the appropriate receptor
- Regulate the activity of target cells/tissues/organs
Describe peptide and steroid hormones with an example
- Peptide - majority of hormones within the body, water soluble, eg insulin
- Steroid - made from lipids, lipid soluble, eg cortisol
What 2 things can the action of a hormone be dependant?
- The concentration of the hormone
- The abundance of target cell receptors (sensetivity)
What are the 2 hormones produced in the pituitary gland and their actions?
- Antidiuretic hormone (vasopressin) - affects water retention and blood pressure
- Growth hormone - growth and development, fat distribution
What are the 2 hormones produced in the adrenal glands and their actions?
- Aldosterone - regulates salt, water balance and blood pressure
- Corticosteroid (eg cortisol) - anti-inflammatory, blood glucose regulation, salt and water balance, muscle strength
What are the 2 hormones produced in the pancreas and their actions?
- Insulin - regulates blood sugar, promotes glucose uptake into cells
- Glucagon - regulates blood sugar - increases blood glucose
What is the hormone produced in the kidneys and its action?
Erythropoietin - regulates RBC production
Describe the 3 ways endocrine glands are stimulated via negative feedback and an example for each
- Hormonal stimulation - hormones will influence secretion of other hormones eg pituitary gland hormone –> pancreas
- Humoral stimulation - fluctuating concentrations of ions and nutrients in the blood eg increased blood glucose –> insulin
- Neural stimulation - nerve fibres will detect changes and initiate hormone release eg digestion of food –> release of insulin
Describe the human growth hormone (HGH)
- Growth and development of tissues ie cell division and hypertrophy
- Hypothalamus releases growth hormone releasing hormone to anterior pituitary gland which releases HGH
- To adipose tissue, bone and muscle
- HGH can directly influence target tissues
What are the most common hormones associated with the HP-adrenal axis/stress response?
- Catecholamines (epinephrine and norepinephrine) - increase HR and improve muscle contracibility
- ACTH and cortisol - ACTH secreted from pituitary gland –> initiates secretion of cortisol from adrenal gland
Describe cortisol
- Steroid hormone (synthesised from cholesterol)
- Most organs within the body have cortisol receptors, therefore cortisol can act on these organs
- General benefits are to help deal with stress
- Anti inflammatory, mobilisation of fuel sources (increases availability of blood glucose), promotes gluconeogenesis (synthesis of glucose)
What are the long term consequences of cortisol?
- Interferes with bone formation
- High blood pressure –> type 2 diabetes
- Suppress immune function
Describe acute exercise
- Critical threshold for exercise intensity (50-60% VO2 max)
- Greater intensity = greater increase in hormones (generally)
- At fixed intensity, duration influences the response
- Able to deal with demands and maintain homeostasis
Describe chronic exercise
- Adaptive or maladaptive response to training
- Hormonal response to sub-maximal exercise after training is reduced
- Increases sensitivity of target tissues and reduced neural, humoral and hormonal disturbance
- Psychological stress response decreases in those that are more physically active
- Excessive endocrine responses through chronic exercise (and additional life stresses) can become harmful
- For athletes this can lead to maladaptation and impair performance (overtraining)
