Test 2 Flashcards
PASS
Endocrine System uses what for communication
Hormones
Hormones bind to specific protein receptors on the surface of cell membranes or inside the cell
Hormone-receptor complex
Cells can have ______ to ______ receptors for a specific hormone.
2,000-10,000
Steroid Hormones
- Derived from cholesterol
- Lipid soluble, easily diffuse through cell membrane
- Hormone receptor complex located inside the cell
Steroid hormones activate genes in nucleus of cell
Direct gene activation
Hormone - receptor complex binds to DNA -> promotes or inhibits protein synthesis
Testosterone promotes protein synthesis
Cortisol inhibits protein synthesis
Non-Steroidal Hormones
Not lipid soluble
Hormone–receptor complex located on surface of cell membrane
Two groups
Protein/peptide hormones
Amino acid-derived hormones
Insulin
Secreted from pancreas
Regulates membrane transport of glucose into skeletal muscle
Insulin binds to receptor on cell surface, causes glucose receptors to translocate from inside the cell to the cell membrane
Glucose converted into glycogen
Glycogenisis
Plasma glucose depends on a balance between
Glucose release by liver
Glucose uptake by muscles
Hormones that increase plasma glucose
Glucagon- pancreas
Epinephrine and norepinephrine- adrenal gland
Cortisol- adrenal gland
Glycogenolysis
Occurs in the liver and skeletal muscle
Gluconeogenesis
Converting non CHO sources into glucose
Lactate
Amino acids
Glycerol
Pyruvate
Occurs in the liver
Glucagon, norepinephrine, and epinephrine increase liver glycogenolysis
Activate the enzyme glycogen phosphorylase
This occurs during exercise and at rest when we become hypoglycemic
Fat is important for ______ athletes
Endurance
Sources of fatty acids used by muscle during exercise
Adipose tissue TG Intramuscular triglycerides (IMTG)
is an enzyme in adipocytes and skeletal muscles that causes lipolysis
Hormone-sensitive lipase (HSL),
Exercise increases activity of the sympathetic autonomic nervous system (SANS)
SANS stimulates release of the hormones epinephrine and norepinephrine from the adrenal glands
Sweating causes losses of body _____ and ______ (Na+), from the blood plasma
Water, electrolytes
Hormones from the following endocrine glands correct fluid and Na+ imbalances
Posterior pituitary gland
Adrenal cortex
Kidneys
Posterior pituitary
Secretes antidiuretic hormone (ADH or vasopressin)
Sweating concentrates the blood plasma, termed hemoconcentration
↑ osmolality stimulates osmoreceptors in hypothalamus
↓ plasma volume sensed by baroreceptors in heart
Both stimulate release of ADH
ADH promotes water conservation by increasing water reabsorption by the kidneys
Less water is excreted in the urine
Aldosterone, hormone secreted by adrenal cortex
Maintains extracellular electrolyte balance
Resulting in ↑ Na+ and water retention by kidneys
Stimuli for aldosterone release
Low plasma Na+
Decreased plasma volume and blood pressure
Renin
an enzyme secreted by the kidneys
Increases aldosterone secretion
↓ blood volume from sweating reduces blood pressure, this is sensed by the kidneys
Stimulates release of renin
Renin-angiotensin-aldosterone mechanism
Renin is released into the blood, converts angiotensinogen → angiotensin I
In the lungs, angiotensin-converting enzyme (ACE) converts angiotensin I → angiotensin II
Angiotensin II stimulates aldosterone release from adrenal cortex and blood vessel constriction
Substrate (CHO and fat) metabolism efficiency
40% of substrate energy ATP
60% of substrate energy heat
Calorimetry
is the measurement of heat transfer from one object to another
Used to estimate energy expenditure
Direct Calorimetry PRO
Direct measure of heat
Good for resting metabolic measurements
Direct Calorimetry CON
Expensive, slow
Exercise equipment adds extra heat
Not all heat leaves the body
Indirect Calorimetry
Measures O2 consumed and CO2 produced, and estimates energy expenditure from their ratio
Only accurate for steady-state oxidative metabolism (cardio)
VO2
volume of O2 consumed per minute
Rate of O2 consumption
Volume of inspired O2 − volume of expired O2
VCO2
volume of CO2 produced per minute
Rate of CO2 production
Volume of expired CO2 − volume of inspired CO2
Respiratory exchange ratio (RER)
Ratio of the amount of CO2 produced to O2 consumed
Protein metabolism is ignored because:
It is not completely oxidized; amino acids contain nitrogen and humans cannot oxidize nitrogen
Accounts for small percentage of energy expenditure
Therefore, RER is more accurately referred to as the non-protein RER
Does the RER change over time?
YES
Fat utilization increases for two reasons:
Lipolysis and beta-oxidation take time; generally takes ~20 minutes before FA are available to muscles
As glycogen levels decrease, fat oxidation increases
Training status affects RER
Trained endurance athletes can use more fat than untrained
At the same submaximal exercise intensity; they will have a lower RER than untrained individual
Diet affects RER
Low-CHO diets = lower RER
Metabolic rate:
the rate at which the body uses energy
VO2 increases as exercise intensity increases
Relationship is mostly linear at submaximal intensities
The highest VO2 an individual can achieve is termed
VO2max
Maximal aerobic capacity
Maximal O2 uptake
VO2peak
VO2max expressed in L·min-1
Absolute VO2max
Suitable for non-weight bearing activities
VO2max expressed in ml·kg-1·min-1
Relative VO2max
Normalized to body weight
Allows comparison of individuals with different body weights
Steady-state:
the physiological responses during submaximal intensities will “level out” within 2-3 minutes
Slow component of VO2:
Due to recruitment of less efficient type II fibers?
Higher VO2 needed to achieve same intensity
Lactate threshold (LT):
point at which blood lactate accumulation ↑ substantially
Expressed as percentage of VO2max
Untrained = ~60% of VO2max
Elite endurance athletes = ~85% of VO2max
Shift toward anaerobic glycolysis due to:
Increased fast-twitch motor unit recruitment
Ischemia (low blood flow) or hypoxia (low O2)
The V-slope method
is based on CO2 production
CO2 is a by-product of the aerobic metabolism of CHO and fats
CO2 is produced in proportion to O2 consumption during aerobic efforts
As H+ enters the blood it reacts with
bicarbonate producing CO2
Now there are two sources of CO2 production
Aerobic
Anaerobic
The ventilatory threshold (VT)
reflects the disproportionate ↑ in VCO2 relative to VO2
O2 demand > O2 consumed at onset of exercise
Body incurs O2 deficit
Anaerobic pathways used for ATP production until cardiorespiratory system can supply muscles with adequate O2
In other words, until body reaches steady-state VO2
Excess postexercise O2 consumption (EPOC)
Oxygen debt
Why? O2 is needed for the following:
Replenish muscle PCr
Clear lactate (oxidize it or convert it to glucose)
Replenishes hemoglobin and myoglobin with O2
Respiratory muscles still removing CO2 from blood
Economy of effort
refers to the VO2 required to exercise at a specific intensity
Multifactorial
Biomechanics
Genetics
Experience
Characteristics of Successful Athletes in Aerobic Endurance Events
High VO2max
High LT
High economy of effort
High percentage of type I muscle fibers
