Chapter 5.2 - Regulation of Blood Sugar Flashcards
What is glucose? What is blood sugar?
Sugar in the blood is in the form of glucose.
blood sugar = the amount of glucose in the blood
Why do we need glucose in the body?
- All cells need a constant supply of glucose
- Because it is the SOURCE OF ENERGY for all cell activities
- eg movement, reproduction, synthesizing molecules active transport, + others
ENERGY IS RELEASED FROM GLUCOSE MOLECULES BY CELLULAR RESPIRATION
What is the cellular respiration equation? (word)
GLUCOSE + OXYGEN —> CARBON DIOXIDE + WATER + ENERGY
Where do we get our source of glucose?
body’s SOURCE of GLUCOSE is in the FOOD WE CONSUME
- CARBOHYDRATES in our food are BROKEN DOWN into GLUCOSE DURING DIGESTION,
- then ABSORBED into the BLOOD through the WALLS of the SMALL INTESTINE.
- after meal, BLOOD GLUCOSE CONT. can RISE SHARPLY
- HOMEOSTATIC MECHANISMS then BEGIN to OPERATE to REDUCE the BLOOD GLUCOSE CONT. AND MAINTAIN it at a NORMAL LEVEL.
- ANY EXCESS GLUCOSE in the blood must be REMOVED and STORED READY for use in CELLULAR ACTIVITIES between meals.
WHAT IS glycogen?
A POLYSACCHARIDE MADE UP OF 1000S OF GLUCOSE MOLECULES BONDED TOGETHER IN BRANCHING CHAINS: FUNCTIONS AS A STORE OF GLUCOSE MOLECULES IN MUSCLE AND LIVER CELLS
GLUCOSE IN THE BODY IS STORED AS GLYCOGEN.
GLYCOGEN IS A MOLECULE made up of LONG CHAINS of GLUCOSE MOLECULES.
- Body is able to store about 500g of glycogen:
- about 100g is stored in the liver
- remainder in skeletal muscle cells
- STORED IN THE LIVER
What is the link between Glucose and Glycogen?
EXCESS GLUCOSE IN THE BODY IS CONVERTED TO GLYCOGEN FOR STORAGE.
- BLOOD GLUCOSE LEVEL HIGH (eg. after a meal)
Alternatively, GLYCOGEN CAN BE CONVERTED BACK TO GLUCOSE, when there is not enough glucose in the blood.
- BLOOD GLUCOSE LEVEL LOW (eg. during exercise)
LIVER - LOCATION, WHAT, HOW.
LOCATION - upper part of the abdominal cavity, below the diaphragm.
WHAT - largest gland, which has an important role in the CONTROL OF BLOOD SUGAR CONT.
ROLE - LIVER is able to CONVERT GLUCOSE –> GLYCOGEN FOR STORAGE, OR GLYCOGEN –> GLUCOSE FOR RELEASE into BLOOD.
HOW? -
- most of the liver’s SUPPLY VIA HEPATIC PORTAL VEIN,
- BRINGS BLOOD DIRECTLY FROM THE STOMACH, SPLEEN, PANCREAS, SMALL AND LARGE INTESTINES.
- SO THAT THE LIVER HAS THE 1ST CHANCE TO ABSORB THE NUTRIENTS FROM DIGESTED FOOD.
- after a typical meal, containing a high portion of carbohydrates is consumed, THE BREAKDOWN PRODUCTS, MAINLY GLUCOSE, ARE ABSORBED INTO THE BLOOD CAPILLARIES OF VILI OF SM. INTST.
GLYCOGEN
- IS stored in the liver, for SHORT TERM ENERGY SUPPLY
- can PROVIDE GLUCOSE FOR BODY CELL for 6 HOURS ONLY, if no other supply is available
- if more energy required, the body uses the energy reserves in stored fat.
THE HEPATIC PORTAL VEIN CARRIES THE GLUCOSE TO THE LIVER, WHERE THE NUMBER OF THINGS MAY OCCUR
WHAT ARE THEY?
GLUCOSE MAY:
- REMOVED FROM BLOOD by liver to PROVIDE ENERGY FOR LIVER FUNCTIONING
- REMOVED by the LIVER and or MUSCLES and CONVERTED INTO GLYCOGEN FOR STORAGE.
- CONTINUE, TO CIRCULATE in the BLOOD,
- AVAILABLE FOR BODY CELLS TO ABSORB AND USE AS A SOURCE OF ENERGY. - CONVERTED into FAT for LONG TERM STORAGE, if it is IN EXCESS of that required to MAINTAIN BOTH NORMAL BLOOD SUGAR and TISSUE GLYCOGEN LEVELS.
THE HEPATIC PORTAL VEIN CARRIES THE GLUCOSE TO THE LIVER, WHERE THE NUMBER OF THINGS MAY OCCUR
WHAT ARE THEY?
THE ROLE OF LIVER AND HEPATIC VEIN…
GLUCOSE MAY:
- REMOVED FROM BLOOD by liver to PROVIDE ENERGY FOR LIVER FUNCTIONING
- REMOVED by the LIVER and or MUSCLES and CONVERTED INTO GLYCOGEN FOR STORAGE.
- CONTINUE, TO CIRCULATE in the BLOOD,
- AVAILABLE FOR BODY CELLS TO ABSORB AND USE AS A SOURCE OF ENERGY. - CONVERTED into FAT for LONG TERM STORAGE, if it is IN EXCESS of that required to MAINTAIN BOTH NORMAL BLOOD SUGAR and TISSUE GLYCOGEN LEVELS.
WHAT IS GLYCOGENESIS?
GLUCOSE MOLECULES ARE CHEMICALLY JOINED IN LONG CHAINS TO FORM GLYCOGEN MOLECULES.
Formation of glycogen from other carbohydrates
- IT IS STIMULATED BY THE PANCREATIC HORMONE - INSULIN
- GLYCOGEN ITSELF CANNOT BE USED BY CELLS: IT MUST BE CONVERTED INTO GLUCOSE TO MAINTAIN BLOOD SUGAR LEVELS AND SUPPLY ENERGY FOR LIVER ACTIVITY
- GLYCOGEN IN MUSCLE CELLS PROVIDES THE GLUCOSE REQUIRED FOR MUSCLE ACTIVITY
WHAT HAPPENS IF THE LEVEL OF GLUCOSE IN THE BLOOD DROPS BELOW NORMAL?
GLYCOGEN STORED IN THE LIVER AND MUSCLE CELLS CAN BE BROKEN DOWN INTO GLUCOSE.
* GLYCOGENOLYSIS
WHAT IS GLUCOGENOLYSIS
THE PROCESS OF CONVERTING GLYCOGEN BACK INTO GLUCOSE
- most frequently occurs between meals and is stimulated by the PANCREATIC HORMONE GLUCAGON.
WHAT IS GLUCONEOGENESIS
IT IS THE CONVERSION OF FATS OR PROTEINS INTO GLUCOSE.
- THE PROCESS OF PRODUCING GLUCOSE MOLECULES FROM LIPIDS AND AMINO ACIDS
WHAT IS THE PANCREAS? LOCATION
LOCATION - LYING PARTLY in the CURVE of the DUODENUM.
WHAT? pale grey gland, 12-15 cm long.
JOB? Has ISLETS OF LANGERHANS - 2 TYPES: ALPHA secreting GLUCAGON BETA secreting INSULIN
DEFINE ISLETS OF LANGERHANS
Clusters of endocrine cells in the pancreas: secrete the hormones insulin and glucagon via the Beta and Alpha cells respectively.
Define alpha cell
A type of cell in the islets of Langerhans in the pancreas that secretes the hormone insulin.
Define beta-cell
A type of cell in the islets of Langerhans in of the pancreas that secretes the hormone insulin.
Insulin from the beta cells causes a DECREASE in blood glucose level.
HOW?
- accelerating the TRANSPORT OF GLUCOSE FROM THE BLOOD INTO BODY CELLS, ESPECIALLY IN SKELETAL MUSCLES
2. ACCELERATING CONVERSION OF GLUCOSE INTO GLYCOGEN IN THE LIVER AND SKELETAL MUSCLE. #GLYCOGENESIS
- STIMULATING CONVERSION OF GLUCOSE INTO PROTEIN (PROTEIN SYNTHESIS)
- STIMULATING THE CONVERSION OF GLUCOSE INTO FATS (LIPIDS), IN ADIPOSE TISSUE, OR FAT STORAGE (LIPOGENISIS)
WHAT IS LIPOGENESIS?
The production of lipids (fats)
THE ACTIVITIES TO DECREASE BLOOD GLUCOSE LEVELS IN A NEGATIVE FEEDBACK LOOP.
Stimulus - blood glucose levels rise above normal
Receptor - Chemoreceptors in the beta cells
Modulator - islets of Langerhans stimulate secrete INSULIN
MESSAGE - insulin to be secreted
EFFECTOR - SKELETAL MUSCLES, AND LIVER
- accelerating the TRANSPORT OF GLUCOSE FROM THE BLOOD INTO BODY CELLS, ESPECIALLY IN SKELETAL MUSCLES
2. ACCELERATING CONVERSION OF GLUCOSE INTO GLYCOGEN IN THE LIVER AND SKELETAL MUSCLE. #GLYCOGENESIS
- STIMULATING CONVERSION OF GLUCOSE INTO PROTEIN (PROTEIN SYNTHESIS)
- STIMULATING THE CONVERSION OF GLUCOSE INTO FATS (LIPIDS), IN ADIPOSE TISSUE, OR FAT STORAGE (LIPOGENISIS)
NEGATIVE FEEDBACK - Decrease in blood glucose level
WHAT IS LIPOLYSIS?
The breakdown of lipids (fats) in the body.
Glucagon from the alpha cells causes an increase in blood glucose levels. HOW?
- Stimulating GLYCOGENOLYSIS in the LIVER
- Stimulating GLYCONEOGENESIS, in the LIVER
- involves the breakdown of lipids in the process (LIPOLYSIS) - MILD STIMULATING EFFECT on PROTEIN BREAKDOWN.
- THE GLUCOSE FORMED IS RELEASED INTO THE BLOOD, AND GLUCOSE LEVEL RISES
THE ACTIVITIES TO INCREASE BLOOD GLUCOSE LEVELS IN A NEGATIVE FEEDBACK LOOP.
Stimulus - blood glucose levels decrease above normal
Receptor - Chemoreceptors in the alpha cells
Modulator - islets of Langerhans stimulate secrete GLUCAGON
MESSAGE - GLUCAGON to be secreted
EFFECTOR - SKELETAL MUSCLES, AND LIVER
RESPONSE -
1. Stimulating GLYCOGENOLYSIS in the LIVER
- Stimulating GLYCONEOGENESIS, in the LIVER
- involves the breakdown of lipids in the process (LIPOLYSIS) - MILD STIMULATING EFFECT on PROTEIN BREAKDOWN.
- THE GLUCOSE FORMED IS RELEASED INTO THE BLOOD, PRODUCTION REDUCED
NEGATIVE FEEDBACK – GLUCOSE LEVEL RISES
What determines the level of glucose in the blood?
The REGULATION of the SECRETION of GLUCAGON, like that of INSULIN SECRETION, is DIRECTLY DETERMINED BY THE LEVEL OF GLUCOSE IN THE BLOOD AND CONTROLLED BY A NEGATIVE FEEDBACK SYSTEM.
ADRENAL GLANDS - LOCATION, WHAT, HOW. ROLE?
LOCATION - situated above the kidneys, one gland above each.
WHAT? - 2 distinct parts
- MEDULLA (INNER)
- CORTEX (OUTER)
ROLE?
- PRODUCES A NUMBER OF HORMONES
1. CORTEX - SECRETION OF GLUCOCORTICOIDS
- MEDULLA - ADRENALINE (EPINEPHRINE), NORADRENALINE (NORAEPINEPHERINE)
How does the adrenal cortex affect blood glucose level?
IT INCREASES BLOOD SUGAR LEVEL
- Anterior lobe Pit. Gland secretes ADRENOCORTICOTROPIC HORMONE (ACTH)
- Stimulates ADRENAL CORTEX secrets GLUCOCORTIODS - CORTISOL.
- These hormones REGULATE CARBOHYDRATE METABOLISM by ENSURING ENOUGH ENERGY IS PROVIDED TO CELLS.
- STIMULATE THE CONVERSION OF GLYCOGEN INTO GLUCOSE DURING GLYCOGENOLYSIS.
- ALSO INCREASES THE RATE AT WHICH AMINO ACIDS ARE REMOVED FROM CELLS, MAINLY MUSCLE CELLS, AND TRANSPORTED TO THE LIVER.
- SOME OF THESE AMINO ACIDS MAY BE CONVERTED INTO GLUCOSE BY LIVER DURING GLUCONEOGENESIS IF GLYCOGEN AND FAT LEVELS ARE LOW. - GLUCOCORTICOIDS PROMOTE THE MOBILISATION OF FATTY ACIDS FROM ADIPOSE TISSUE, ALLOWING MUSCLE CELLS TO SHIFT FROM USING GLUCOSE TO FATTY ACIDS FOR THEIR METABOLIC ENERGY.
How does the adrenal MEDULLA affect blood glucose level?
IT INCREASES BLOOD SUGAR LEVEL IN BLOOD
- ADRENAL MEDULLA SYNTHESISES ADRENALINE AND NORADRENALINE hormones, to produce the same effects as those brought by the SYMPATHETIC NERVES of the AUTONOMIC NERVOUS SYSTEM.
- ONE SUCH EFFECT IS INCREASE BLOOD GLUCOSE LEVELS.
- ADRENALINE ELEVATES BLOOD GLUCOSE LEVELS VIA GLYCOGENOLYSIS IN LIVER
- counteracts the effects of insulin - It stimulates the PRODUCTION OF LACTIC ACID from GLYCOGEN IN MUSCLE CELLS, which can be used by the LIVER TO MANUFACTURE GLUCOSE
Explain Blood glucose homeostasis
The normal level of glucose in the blood is between 4-6 millimoles per liter.
- 5mmol/L
- 90mg/100mL
figure 5.15
explanation of all three
