Week 7: The Endocrine System Flashcards
What is homeostasis?
The internal environment remains relatively constant though there are changes in the external environment
What is the endocrine system?
A collection of glands that secrete hormones into circulation to be carried to distant organ(s)
Define nervous system
Performs short-term very specific responses to environmental stimuli
How do the nervous system transfer messages?
Via chemical messengers (neurotransmitters)
How does the endocrine system transfer messages?
Chemical messengers (hormones)
What is the function of the endocrine system?
1) Epithelial secretory cells manufacture specific hormones
2) Hormones are then releases systemically
3) Transport of hormones to rest of body conveys specific regulatory information among cells and organs
What are the four different ways hormones can communicate?
Endocrine
Autocrine
Paracrine
Juxtacrine
Describe how hormones communicate via autocrine
Hormones acts directly back on the cell that has produced it
Describe how hormones communicate via paracrine
Hormones acts directly upon a nearby cell
Describe how hormones communicate via juxacrine
Hormonal intracellular communication between connecting cells- requires physical contact of two cells
What is homeostasis ?
Maintenance of relatively constant chemical/physical conditions of the internal environment
What is successful compensation?
When homeostasis is re-established
What does it mean to fail to compensate?
pathophysiology/illness/death
What is the endocrine system?
A collection of glands that secrete hormones into circulation to be carried to distant organs
What are the four ways in which hormones can communicate?
Endocrine
Autocrine
Paracrine
Juxtacrine
What are the three methods in which endocrine glands are stimulated to release hormones?
Humoral stimuli
Hormonal stimuli
Neural stimuli
How does humoral stimuli work?
Changes in the composition of blood
How does hormonal stimuli work?
Arrival or removal of a specific hormone
How does neural stimuli work?
Nerve fibres stimulate hormone release
What controls cellular activity?
Enzymes
What do cells need to have for hormones to affect them?
Cells that possess specific receptors for that hormone
What determines the magnitude of the hormone effect?
The number of target receptors
Concentration of the hormones
Affinity of receptor for hormone
Influence of other hormones
What happens to a receptor during up and down regulation?
Up- increased number of hormone receptors
Down- decreased number of hormone receptors
What are the two main hormone categories?
Steroid
Non-steroid
What does the category of hormone determine?
How the hormone is transported in blood
How the hormone enters/is used by cells
What are steroid hormones synthesized from?
Cholesterol
Are steroid hormones lipid soluble?
Yes
How do steroid hormones circulate the blood?
Bound to a carrier protein
When steroid hormones are bound to binding proteins are the active or inactive?
Inactive
Can steroids diffuse into the cell?
Yes
Where are the specific steroid receptors are located?
Cytoplasm or nucleus
What does the steroid hormone do once it’s in the nucleus and what does that lead to?
Activate gene expression therefore protein synthesis is induced
Are non-steroid hormones water-soluble?
Yes
What is the molecular weight of non-steroid hormones and what effect does this have?
High molecular weight therefore cannot diffuse across the cell membrane
Where do non-steroid hormones interact/bind with receptors?
On the cell’s plasma membrane
What is signal transduction?
The process by which extracellular signals are communicated into a cell to affect function
What is the most common type of feedback loop?
Negative feedback
What happens during a negative feedback loop?
Stimulus activates endocrine gland
Endocrine gland secretes hormone into blood stream
Target cell respond to hormone alter original stimulus
This signal then reaches original endocrine gland to switch-off further hormone production
Describe what the negative feedback loop does in simple terms
The output inhibits the input
What hormone is lipid soluble?
Steroid
What does receptor down regulation mean?
The number of receptors on a cell decreases
What are the two lobes of the pituitary gland?
Anterior lobe
Posterior lobe
What does the posterior lobe of the pituitary gland do?
Stores hormones made by hypothalamic neurons and releases into circulation (does not synthesise hormones)
What does the anterior lobe of the pituitary gland do?
Receives hypothalamic hormones which stimulates further hormone release by pituitary gland
What does the pineal gland produce?
Melatonin
Where is the thyroid gland located?
In the neck inferior to the larynx
What does the thyroid gland secrete?
T3 and T4
What is the thyroid gland involved in?
Tissue development and growth and macronutrient metabolism
Where is the parathyroid gland located?
Posterior of the thyroid gland
What does the parathyroid gland produce?
Parathyroid hormone (PTH)
What ion is the parathyroid hormone the most important regulator of?
Ca2+
What does parathyroid hormone stimulate?
Ca2+ re-absorption at kidney, and calcium resorption at bone
What are the two types of functions that the pancreas has?
Exocrine
Endocrine
What is the endocrine function of the pancreas?
Secretes substance (i.e. insulin) to regulate blood glucose levels
What is the exocrine function of the pancreas?
Secretes enzymes to digest exogenously obtained substances (i.e. carbohydrates)
In the pancreas, what do alpha cells do and why?
Produce glucagon therefore increase blood glucose
In the pancreas, what do beta cell do and why?
Insulin to decrease blood glucose
In the pancreas, what do delta cells do and why?
Produce gastrin/somatostatin to regulate alpha and beta cells
In the pancreas, what do F cell do and why?
Pancreatic polypeptide to regulate metabolism
Where are the adrenal glands located?
Superior to each kidney
What are the two portions of the adrenal glands called?
Outer adrenal cortex
Inner adrenal medulla
What are the way in which the endocrine system can fail?
Abnormal hormone receptor function/levels
Altered intracellular response to the hormone receptor complex
Hyper or hyposecretion of hormones by glands
In the adrenal medulla what happens when the sympathetic nerve fibres stimulate it?
Stimulates the release of neurotransmitters epinephrine (adrenaline) and norepinephrine
Where are the epinephrine and norepinephrine alpha receptors found?
In sympathetic organs/tissues
Where are the epinephrine and norepinephrine beta receptors found?
Located on membranes of many organs, including muscles, lungs, heart and liver
What are catecholamines?
Hormones secreted by the adrenal glands
What happens to glucagon when insulin levels increase?
Production decreases
