Hormonal Control

    Cards (21)

    • Substrate utilization during exercise:
      • significant quantity of substrate comes from blood
      • low intensity = blood
      • high intensity = muscle
    • Blood glucose homeostasis:
      • glucose is a major substrate for metabolism
      • glucose glucose is the only fuel acceptable to the brain and CNS
      normal resting blood glucose concentration:
      • 4.05.5 mmol/L
      • 90100 mg/dL
    • Exercise increases blood glucose uptake:
      • uptake is initiated by muscle contraction
      • sends signals that cause translocation of glut-4 to sarcolemma
      • contraction changes metabolism concentration
      • glut-4 accepts glucose and transports it into cytosol
    • Another reason why maintaining blood glucose is important:
      • to prevent hypoglycemia
    • We do not store a lot of glucose in our body, therefore:
      • if we only relied on glucose, we would deplete it rapidly
    • Blood glucose and exercise:
      • at moderate intensity, energy is produced via oxidative phosphorylation
      • glucose actually rises then plateaus
      • suggests glucose is entering blood from another source at rate equal to its uptake
    • How do we replenish glucose?
      liver is a big source of sugar
      2 processes:
      • anabolic rxns: gluconeogenesis; building glucose; uses lactate, pyruvate, and glycerol (some amino acids)
      • catabolic rxns: breakdown glycogen (stored in liver)
    • Lipid mobilization:
      • we eventually limit glucose use by relying on fats instead
      • indirect way to maintain glucose
    • Glucose regulation during exercise:
      requires physiological regulation:
      • endocrine system = chemical communication
      • nervous system = electrical communication
    • Endocrine:
      • controls physiological processes that support exercise and maintain homeostasis
      • releases hormones
      • hormones = produced and released by glands, transported through blood
    • Hormones:
      • secretion = released in pulsatile bursts (plasma concentration fluctuates); triggered by negative feedback
      • receptors = bind to specific receptor
      • action = exert effects after binding; initiate reactions
    • Endocrine glands:
      • pancreas
      • adrenal glands
      • thyroid gland
      • anterior pituitary gland
    • Pancreas:
      • insulin = lowers blood glucose; counters hyperglycemia
      • glucagon = raises blood glucose; counters hypoglycemia
    • Blood glucose control:
      • type 1 diabetes = insulin deficiency
      • type 2 diabetes = impaired glucose control
    • Insulin-stimulated glucose uptake:
      • insulin binds to receptors to signal glut-4 transporters from vesicles
    • Glucose regulation by pancreatic hormones:
      • during moderate to heavy, blood glucose does not change much because…
      • insulin falls
      • glucagon rises
    • Prolonged exercise:
      • glucagon rises quickly at exercise onset to prevent hypoglycemia
      • insulin falls so so that there is less glucose uptake
    • Adrenal medulla:
      • above kidneys
      • releases catecholamines (epinephrine and norepinephrine)
      • stimulate glycogenolysis
      • stimulate lipolysis (Epi)
      • suppress insulin secretion
      • increase glucose and free fatty acids to active muscle
    • EPI and NE:
      • increase intensity, Epi and NE rise
      • shift of use from carbs to fats
    • Summary:
      • insulin = cellular glucose uptake
      • insulin = glycogen synthesis
      • insulin = triglyceride synthesis
      • insulin = decrease blood glucose
      • glucagon = liver glycogenolysis
      • glucagon = liver gluconeogenesis
      • Epi = liver glycogenolysis
      • Epi = muscle glycogenolysis
      • Epi = lipolysis
      • NE = liver glycogenolysis
      • NE = muscle glycogenolysis
    • Hormones…?
      regulate shift in substrate utilization and mobilization of fat and carb stores
    See similar decks