Endocrine System 2 Flashcards
What is normal range?
Set of values for a regulated variable. These can fluctuate around a set point
What is a set point?
Physiological value of which a normal range functions
True or false? Individual normals tend to be wider than the range of value of the population.
False
Describe the negative feedback loop
The stimulus is detected by the sensors and this sends signals to the control centre which sends signals to the effectors to oppose the effect of the stimulus.
What is the role of the sensors?
Monitor the variable and detect changes
What is the role of the control centre?
Compare the variable’s changed values to the set point and sends signals to the effector.
What is the role of the effector?
Acts to oppose the stimulus
What is positive feedback?
Amplification. When a process is driven to completion.
If a variable goes up, the feedback makes it go up further.
What is the purpose of the endocrine system?
Releases hormones into the blood stream to bind to the membrane receptors of target cells.
What is the relative speed of the endocrine system?
Slow, but long lasting
What are hormones?
Chemicals that bind to specific target cells within the body
What are hormones made up of?
Amino acids or cholesterol
Where do hormones come from?q
Released by endocrine gland cells
How do hormones travel around the body?
In the bloodstream
How do water-soluble hormones work?
They do not require carrier proteins to travel in the blood but cannot cross cell membranes so they bind to receptors on the membrane of the target cell
How do lipid-soluble hormones work?
Require carrier proteins to travel in the blood but can diffuse easily across plasma membranes to =bind to the intracellular receptors inside of a target nucleus.
Are receptors hormone specific?
Yes
How do lipid soluble hormones produce a response?
Stimulate creation of new proteins, enzymes, to produce a response.
How do water soluble hormones produce a response?
Activate a second messenger system to produce a response
How do hormones know when to stop?
The body will break them down/ recycle them or they are excreted in sweat, urine, or faeces.
What is an example of a water-soluble hormone?
Adrenaline
What is an example of lipid-soluble hormone
Thyroid hormone and cortisol
How are lipid soluble hormones synthesised and stored?
Some are premade and some are made only when required
How are water soluble hormones synthesised and stored?
All are premade and stored
What kind of response does a lipid soluble hormone evoke?
Cellular Response
Is the action mechanism for lipid soluble fast or slow?
Slow because protein synthesis takes a long time
How fast is the action mechanism for water-soluble hormones?
2nd messengers are premade so this is a fast response.
Describe the action mechanism for Water soluble hormone
Receptors activate G-proteins either inhibits or activates 2nd messengers which affect the actions of other proteins (ion channels or enzymes)
What are the 2 types of 2nd messengers?
cAMP and Ca ions.
What are the two glands involved in the regulation of plasma glucose and calcium concentration?
Parathyroid Glands, Thyroid gland, and the kidneys
Why does calcium need to be regulated?
Because there needs to be enough calcium in the blood for cells to use when they need it
How does the body use calcium?
Calcium is a second messenger which affects the actions of proteins and ion channels.
Interacts with vesicles to facilitate release of neurotransmitter
Interacts with myofilaments to form cross-bridges.
All muscle requires Ca
Where is most calcium stored in the body?
In the bones, it is important for making bones hard
How does calcium enter the blood plasma?
Absorbed from the digestive tract?
Resorbed from bone broken down by osteocytes
Reabsorbed back into blood from kidneys
How does the calcium get removed from the blood?
Deposited back into the bone by osteoblasts
Filtered out of the blood by the kidneys
Which organs/ glands are involved in Ca homeostasis?
Parathyroid
Kidneys
Thyroid gland
Bones
Digestive system?
How are the parathyroid glands involved in the regulation of Ca?
They secrete PTH (parathyroid hormone)
How many parathyroid glands are there?
4
How are kidneys involved in Ca homeostasis
Stimulated by PTH to secrete calcitriol
Filter blood, reabsorbed and filters Ca into the blood
How is the thyroid gland involved in Ca homeostasis?
Secretes calcitonin (minor role)
How are bones involved in Ca homeostasis
Osteoblasts remove Ca to store as bone
Osteoclasts release Ca by breaking down bone
What hormones stimulate the bone mechanisms in Ca homeostasis?
Parathyroid, calcitriol, and calcitonin
How is the digestive system involved in Ca homeostasis?
Absorbs calcium from digesting food
What hormone regulates the digestive system in Ca homeostasis?
Calcitriol
What are the sensors in Ca homeostasis?
Parathyroid glands, detect calcium levels in blood flowing through them.
What are the effectors for Ca homeostasis?
Bone, Kidneys (calcium reabsorbed), kidneys (vitamin D converted to calcitriol), and digestive tract
What is hypercalcemia?
High plasma Calcium levels
What are the two sensors for hypercalcemia?
Thyroid and parathyroid glands
What role does the thyroid have in correcting hypercalcemia
Releases calcitonin, which sends messages to the bones and the kidneys to perform their functions
What gland is involved in plasma glucose homeostasis
Pancreas
Why is blood glucose regulated?
Because it needs to be available if cells require it
What is the purpose of glucose in the body?
Used to make ATP and other substances essential for body function
How is glucose stored in the body?
Stored as glycogen
How does glucose enter the blood plasma?
Absorbed by the digestive tract.
Released into the blood by the liver
How is glucose removed from blood plasma?
Removed from the blood by body cells
Removed and stored in liver and skeletal muscle as glycogen
Stored in adipose as fat
When is more glucose required in the body?
During periods of growth, stress, and exercise
Which glands involved in glucose homeostasis?
Pancreas, liver
How is the pancreas involved in glucose homeostasis?
Pancreatic cells secrete glucagon and insulin
What do alpha islet cells secrete?
Glucagon
What do beta islets cells secrete?
Insulin
Is glucose high or low in a fasting state?
Low
Describe what happens during hypoglycemia?
Alpha cells detect low glucose and release glucagon. This sends signals to the liver which can react in 3 different ways
What occurs during gluconeogenesis?
Glucose molecules are built and released into the blood
What occurs during glycogenolysis?
Break down of glycogen to release more glucose into the blood