Lecture 26 Flashcards
Homeostasis of plasma calcium concentration glands involved
Parathyroid glands
Thyroid glands
Why is plasma ( Ca2+ ) regulated
Needs to be enough Ca2+ calcium in the blood for cells to use it when they need to
How does the body use Ca2+
- one way is from the water soluble hormones, when the G protein activates or inhibits 2nd messenger ( eg: cAMP or Ca2+ )
- Ca2+ reacts with vesicles to facilitate realise of neurotransmitter
- Ca2+ reacts with myooofilaments in sacomeres to facilities cross bridge formation
- all muscles require Ca2+ for tension creation
- more than 99% of Ca2+ in the body is stored into the bones and it is very important for making the bones hard and strong
- bones act as a Ca2+ storage space
How does Ca2+ enter or exit the blood plasma
Enter: Absorbed into blood from digestive tract,
Exit: removed from blood and into the bone by osteoblast during remodelling and growth
Enter: resorbed into blood from bone broken down by osteoclast
In the kidneys
Exit : filter out of blood by kidneys
Enter: reabsored back into blood by kidney
Glands and hormones that are involved in plasma Ca2+ homeostasis
Parathyroid glands:
- there are 4 parathyroid glands on the posterior side of the thyroid gland
- it secretes PTH: parathyroid hormone, and this is the most importantly hormone for Ca2+ homeostasis
Kidneys:
- there are 2 kidneys And it is anterior to the lower limb ribs
- stimulated by PTH to secrete CALCITRIOL
- filter blood to make urine
- and are also the site for filtration of Ca2+ out of an reabdorbption of Ca2+ back into the blood
Thyroid glands:
- wraps around tracheas/ windpipe in the throat
- secretes CALCITONM, calcitonin plays a minor role in Ca2+ homeostasis
Bones:
- osteoblast remove Ca2+ from plasma to store into bo
- osteoclast eases Ca2+ into plasma when breaking down the bone
- parathyroid, calcitriol and calcitonin affect these processes
Digestive system:
- absorbed nutrients from food
- absorbed Ca2+ enter the bloodstream
- Ca2+ absorbsion is increased under the influence of CALCITITROIL
How does the body correct HYPOcalcemia - Low Ca2+
HYPOcalcemia means that the calcium is too low
So this is the stages
1) parathyroid glands ditect low Ca2+ and it compares it to the set point and then releases more PTH
2) it goes into the effectors which are, bone and the kidney
Bone: more Ca2+ resobsion by osteoclast = more Ca2+ in thr plasma
Kidneys: more Ca2+ reabsorbtion from pre-urine filtrate = more Ca2+ into plasma
These both make the plasma increase
Also for Kidney: more vitamin D is converted to Calcitriol ( this acts on digestive tract, kidneys and bone ) and so after the Digestive tract: more Ca2+ absobsion from food = more Ca2+ into plasma
This all results in a negative feedback as more Ca2+ increases so we need to reduce the PTH release
How does the body correct hypercalcemia - high plasma Ca2+ using parathyroid glands
So the parathyroid gland detiects the high Ca2+ so it realises less of the PTH and then goes to the effectors
The effectors are
bone: less Ca2+ resobsion from osteoclast so less Ca2+ in plasma
Kidney: less Ca2+ resorbsion from pure urine filtrate = less Ca2+ into plasma
Also kidney ; less victimun D is converted to Calcitriol and this acts on the digestive tract and bone and kidneys.
Digestive tract : less Ca2+ uptake so less Ca2+ into the plasma
All results in plasma Ca2+ decreasing and this results in negative feedback increasing the PTH release
How does the body correct HYPERcalcemia - high Ca2+ using Thyroid
Thyroid glands will detect the high Ca2+ and it compares it to the set point value. Then it releases calcitonin
The effectors are Bone and kidneys
Bone: less Ca2+ resobsion from osteoclast and so less Ca2+ into plasma
Kidneys: less Ca2+ reabsorption from pre urine filtrate do less Ca2+ into plasma
And as a result plasma Ca2+ decreases
What are the glands involved in homeostasis of plasma gluclose concentration
Pancreas
Why is the plasma gluclose concentration regulated
Because there needs to be enough gluclose in the blood for cells to use it when they need it
How does the body use gluclose
- body cells use gluclose as the main substrate for making ATP
- make substances essential for the body functioning
- gluclose is stored in the form of glycogen ( long chains of gluclose molecules ) or fat
How does gluclose enter or exit the blood plasma
enter: gluclose absorbed into blood from digestive tract
Exit: gluclose removed from blood by all body cells. Excess gluclose removed from blood and stored in liver and skeletal muscle as glycogen
Enter: gluclose released into blood by liver
Exit: excess gluclose removed from blood and stored int adipose as fat
What happens if there is excess intake of gluclose over long periods of time
Can lead to deseases, insulin and type 2 diabetes
When do cells use more gluclose
During periods of growth, stress and excessive with higher metabolism
Which glands and hormones are ivoove in plasma homeostasis
Pancreas:
- sits just behind the stomach on the left side of the abdomen
- it is the endocrine organ that secretes hormones for plasma ( gluclose ) homeostasis
- pancreatic islet cells secrete hormones: glucagon and insulin
Alpha secretes glucagon
Beta secretes insulin
