Week 2 Flashcards
Hormones alter the rates of cellular reactions by altering rates of…? (3)
- protein synthesis
- enzyme activity
- cell membrane transport
Action of hormones (3)?
- alter rates of cellular reactions
- act at a specific cell receptor site where hormone binding can change
- Ultimately alters cellular functions
Factors that determine hormone levels (3)??
- Secretion rate (not constant, adjust rapidly)
- [hormone] in blood (depends on; synthesis, release, removal)
- over time synthesis = release rate
Growth hormone function?
- Promotes muscle growth and hypertrophy by facilitating AA transport
- Directly stimulates fat metabolism (lipolysis)
- Levels are elevated during aerobic exercise in proportion to exercise intensity
Growth hormone in acute exercise??
- Increase secretion a few minutes after exercise starts (sharp rise in GH production and secretion)
- Beneficial for muscle, bone, CT growth and optimisation of metabolic fuel mix
Hormones of the thyroid gland???
- Triiodothyronin (T3) and Thyroxine (T4)
- Calcitonin
Triiodothyronine (T3) and Thyroxine (T4) function???
- Increase protein and enzyme synthesis
- Increase size and number of mitochondria in cells
- Promote rapid cellular uptake of glucose
- Enhance glycolysis and glycogenesis
- Increase FFA availability for oxidation
Calcitonin function??
- Decreases plasma calcium concentration
- Acts primarily on bones and kidneys
Exercise increase free thyroxin by about ___%; physiological implications not yet determined
35%
With acute exercise, thyrotropin (thyroid stimulating hormone TSH)…?
increases during exercise, affect inconsistent
Hormones of the Adrenal Medulla (3)
- Catecholamines
- Adrenaline (epinephrine) and Noradrenaline (norepinephrine)
Adrenal Medulla hormones are stimulated by…
SNS to prepare for immediate action
Adrenal Medulla hormones function…
- Increase rate of heart contraction, BP, respiration
- Increase metabolic rate, glycogenolysis, release of glucose and FFA to blood
- Allow more blood through muscles by vasodilation and vasoconstriction in certain vessels.
Effect of exercise on adrenal medulla hormones???
- light/mod exercise = little to no change
- Increases dramatically with intense exercise
Hormones of the Adrenal Cortex (3)?
- Mineralcorticoids
- Glucocorticoids
- Gonadocorticoids
Mineralcorticoids function and exercise effect?
- Includes…
- Maintain electrolyte balance in extracellular fluids
- Includes aldosterone
With acute exercise:
- secretion rises (peaks at x6 resting levels)
- Exercise control of secretion via SNS
Glucocorticoids function and exercise effect?
- includes..
- Maintain consistent plasma glucose levels between meals
- Includes cortisol
Acute exercise:
- cortisol increase
- light/mod exercise negative, positive or no change
- Intense exercise increased cortisol (elevated up to 2 hrs post)
Gonadocorticoids function and exercise effects?
- includes…
- Released in addition to those released by reproductive organs but in lesser amounts
- Include androgens, oestrogens and progrsterones
With acute exercise:
Androgens:
- moderate aerobic exercise significantly increases serum and free androgen levels after 15-20 minutes
- Prolonged strenuous exercise - androgen levels may fall below resting values
- Mechanism for exercise effects not currently known but definitely not associated with increase LH production
Hormones of the Pancreas and function (2)
Insulin - secreted when plasma glucose levels are elevated (hyperglycaemia)
Glucagon - secreted when plasma glucose concentrations are below normal (hypoglycaemia)
Insulin with acute exercise???
- In exercise as intensity and duration increases circulating glucose decreases and insulin decreases either through decreased secretion OR increased skeletal muscle uptake OR inhibitory effect on pancreas by SNS
- As progress in long duration exercise insulin output continues to decrease; shift from CHO to FFA mobilisation and metabolism
Glucagon with acute exercise???
- Heavy long duration exercise and starvation -> increase in glucagon
Prolactin (PRL) function with exercise?
- Increases with higher levels of exercise
- Hypothesis - repeated exercise induced release of PRL may inhibit ovaries and thus contribute to delay in menarche; increased incidence of amenorrhea and oligomenorrhea report amongst athletic females
Anti diuretic hormone (ADH) function with exercise?
- Exercise increases ADH secretion -> increased water retention (after severe exercise when dehydration occurs)
- Sweating stimulates ADH secretion - water conservation and decrease risk of dehydration
Power = ???
Power = force x distance/time where force = strength and distance/time = speed
Results of Resistance Training
• Increased muscle size (hypertrophy).
• Alterations of neural control of trained muscle.
• Research show strength gains can be achieved without changes in muscle size, but NOT without neural adaptations.
Possible Neural Factors of Strength Gains
• Synchronization and recruitment of additional motor units for greater force production
• Counteraction of autogenic inhibition allowing greater force production
• Reduction of coactivation of agonist and antagonist muscles
• Changes in the discharge rates of motor units
• Changes in the neuromuscular junction
Muscle Hypertrophy 2 types..
- Transient—pumping up of muscle during a single exercise bout due to fluid accumulation from the blood plasma into the interstitial spaces of the muscle.
- Chronic—increase of muscle size after long-term resistance training due to changes in muscle fiber number (fiber hyperplasia) or muscle fiber size (fiber hypertrophy).
Fiber Hypertrophy – Increased Fibre size
• The numbers of myofibrils and actin and myosin filaments increase, resulting in more cross-bridges; sarcoplasm and connective tissue increase.
• Muscle protein synthesis increases during the post exercise period.
• Testosterone plays a role in promoting muscle growth.
• Training at higher intensities appears to cause greater fiber hypertrophy than training at lower intensities.
Fiber Hyperplasia – increased number of fibres
• It has been proposed that muscle fibers can split in half with intense weight training.
• Each half then increases to the size of the parent fiber.
• Satellite cells may also be involved in skeletal muscle fiber generation.
• It has been clearly shown to occur in animal models; only a few studies indirectly suggest this occurs in humans too.
Early gains in strength appear to be more influenced by ……?
neural factors
Is fibre type change possible?
• A combination of high intensity resistance training and short-interval speed work can lead to a conversion of ST to FTa fibers.
What Determines Fiber Type?
- Genetics determine which type of motor neurons innervate our individual muscle fibres
- Muscle fibres become specialised according to the type of neuron that stimulates them
- endurance training, strength training, and muscular inactivity may result in small changes (less than 10%) in the % of FT and ST fibres
- Endurance training has been shown to reduce % of FT fibres, while increasing fraction of FTa fibres
- Ageing may result in changes in the % of FT and ST fibres
Refractory Period
- Period of repolarisation
- The muscle fibre is unable to respond to any further stimulation
- The refractory period limits a motor units firing frequency
