Lecture 10 - Hormonal Control During Exercise Flashcards
How does the proportion of plasma energy change in relation to intensity increasing (VO2 max increasing)?
- the portion of plasma stays relatively stable
- the proportion is reduced because muscle energy increases significantly
what is blood glucose homeostasis?
- maintenance of blood glucose levels during exercise
what are the two reasons in which maintaining blood glucose homeostasis is important?
- glucose is a major substrate for metabolism
- glucose is the only fuel acceptable to the brain and other CNS tissues
what is normal resting blood glucose concentration?
- 4.0-5.5 mmol/L
- 90-100 mg/dL
what is the term for someone who cannot regulate blood glucose levels well?
- diabetic
how does exercise affect blood glucose?
- causes a massive increase in glucose uptake from the blood
why is it necessary for glucose uptake from the blood to increase?
- maintain energy for muscle contraction during exercise
what are glut-4 transporters?
- transporters on the plasma membrane
- must be present to allow glucose to enter into the cell
- the amount of glut-4 is affected by exercise –> this affects the amount of glucose able to enter the cytosol
why must glucose be restored in the blood immediately?
- if we only used the glucose stored in the blood, we would only have 25 calories worth of energy
- must be replenished or it would fall rapidly
what organ is responsible for blood glucose?
- the liver
- also the gut and kidneys
what are the two systems in the liver that release glucose into the blood?
- gluconeogenesis
- glycogenolysis
what is hepatic glucose production?
- “the release of glucose from the liver”
what are the steps for how gluconeogenesis produces glucose?
- start with pyruvic acid (aka lactic acid)
- creates glucose-6-phosphate (also can be produced by amino acids or glycerol)
- makes glucose
- *this is an anabolic system
what are the steps for how glycogenolysis produces glucose?
- start with glycogen
- breaks down to produce glucose-1-phosphate
- breaks down again to produce glucose-6-phosphate
- this makes glucose
- *this is a catabolic system
what is lipid mobilization?
- a strategy to reduce glucose from falling during exercise (supports the metabolism at the muscle level)
How does lipid mobilization work?
- use free fatty acids to provide acetyl-CoA to the Krebs cycle
- increase in fat metabolism (means we can use less glucose in the muscles)
what are adipocytes?
- subcutaneous fat (adipose tissue)
what is the role of adipocytes in lipid mobilization?
- release fatty acid chains (from the triglycerides) through lipolysis
- into the blood
- transported with albumin
- taken up at the muscle
- form fatty acetyl CoA
- produce energy through the Krebs cycle and electron transport
how is glucose regulated during exercise?
- homeostasis
- through the endocrine system (chemical communication) aka hormones
- through the nervous system (electrical communication) aka sympathetic nervous system
what is the role of the endocrine system?
- controls all physiological processes that support exercise and maintain homeostasis
- does this by releasing hormones
what are hormones?
- signalling molecules to trigger physiological processes within the body
where are hormones produced and released?
- by glands transported by the circulatory system to target organs for regulating physiology
- specifically the endocrine glands (for exercise metabolism)
how are hormones secreted?
- in pulsatile bursts (plasma concentration fluctuates)
- triggered by negative feedback - correcting an “error signal”
what is the role of hormone receptors?
- hormones bind to specific receptors
- without receptors, hormones have no effect
- receptors are located at the target organ
what is the action of hormones?
- exert effects after binding with receptor - do not directly affect cell activity (indirect causation)
- initiate a predictable series of chemical reactions
what are the 4 important endocrine glands for metabolism?
- pancreas
- adrenal gland
- anterior pituitary gland
- thyroid gland
what is the role of endocrine glands?
- regulate the mobilization of fats and carbohydrates
- influence the fuel utilization we use during exercise
what is the role of the pancreas?
- endocrine regulation of metabolism
- a gland important for regulating metabolism through the release of glucagon and insulin
what is the importance of insulin?
- lowers blood glucose
- counters hyperglycemia, opposes glucagon
- facilitates glucose transport in cells
- enhances synthesis of glycogen, protein and fat
- inhibits gluconeogenesis
- is not present in individuals with diabetes
what is the importance of glucagon?
- raises blood glucose
- counters hypoglycemia, opposes insulin
- promotes glycogenolysis, gluconeogenesis
What is type I diabetes?
- absolute insulin deficiency
- no insulin is produced
- exercise is important because of glut-4 and uptake (to help regulate glucose)
what is type II diabetes?
- impaired glucose control
- inadequate insulin production
- reduced effect of insulin
- negative feedback loops are disrupted
how is blood glucose controlled?
- (understand diagram)
- work in a negative feedback system
- increase in glucose signals the release of insulin so glucose lowers and vice versa
what is a sign of hypoglycemia?
- craving for candy/cereal etc.
what is insulin-stimulated glucose uptake?
- insulin binds to the insulin receptors in the plasma membrane
- initiates the same results as exercise does
- glycogen synthesis = glucose uptake, stimulated by insulin
how is glucose regulated by pancreatic hormones during exercise?
- blood glucose does not change even during moderate-to-heavy exercise for long periods of time
- insulin falls during exercise (helps maintain glucose)
- glucagon rises (more glucose is released)
how does glucagon change during exercise?
- has a large percent increase at the beginning
- remains high (to stop hypoglycemia)
- insulin falls and glucose hardly changes
what is the adrenal medulla?
- endocrine regulation of metabolism
- a gland located above each kidney
- releases catecholamines (epinephrine and norepinephrine) –> “fight or flight”
what is the effect of epinephrine and norepinephrine release during exercise?
- increase sympathetic nervous system
- stimulate glycogenolysis in muscle and liver
- stimulate and maintain lipolysis (Epi) –> increase free fatty acids in the blood
- suppress insulin secretion
- supply blood to skeletal muscle
- increase heart rate, increases blood pressure and increases contractile force
- Norepinephrine also causes vasoconstriction to non-active areas to send more blood to the active muscles
how does exercise influence norepinephrine and epinephrine?
- both are increased as exercise continues
- this increases the fat metabolism so you can exercise for longer periods of time
