Exercise Physiology Exam 1

Explain the 6 step process of excitation contraction coupling

1. Action potential travels down a motor neuron to the axon terminal

2. ACh is released into the neuromuscular junction

3. ACh binds to receptors on the sarcolemma, generating a muscle action potential

4. Action potential travels along sarcolemma and down the T-tubules

5. Voltage-sensitive proteins trigger calcium release from the sarcoplasmic reticulum (SR)

6. Calcium binds to troponin, tropomyosin moves, actin binding sites are exposed, and contraction begins

Explain the layers of a myofiber

• Epimysium = surrounds entire muscle

• Perimysium = surrounds fascicles

• Endomysium = surrounds individual muscle fibers

• Sarcolemma = muscle cell membrane

• Sarcoplasm = cytoplasm of muscle cell

What is the function of a sarcomere?

• Functional contractile unit of skeletal muscle

• Shortens during contraction through the sliding filament mechanism

What is the job of myosin?

Thick filament containing ATPase, forms cross-bridges with actin

What is the job of actin?

Thin filament, contains myosin binding sites

What is the job of titin?

Elastic protein, anchors myosin and helps restore resting length

What is the job of tropomyosin?

Covers myosin binding sites on actin

What is the job of troponin?

Moves tropomyosin away from binding sites

Compare/contrast Type I, Type IIa, Type IIx muscle fibers and their effect on exercise, including: peak tension, effects of ATPase, SR, motor units

Type I = slow oxidative, low peak tension, slow ATPase activity, less developed SR, small motor units, high fatigue resistance, best for endurance

Type IIa = fast oxidative-glycolytic, moderate peak tension, fast ATPase activity, moderately developed SR, medium motor units, moderate fatigure resistance

Type IIx = fast glycolytic, highest peak tension, fastest ATPase activity, highly developed SR, large motor units, low fatigue resistence, best for power/sprinting

What are the characteristics of the ATP-PCR system?

Fastest ATP production, anaerobic, lowest capacity, used for sprinting

For ATP-PCR system what is the ATP yield, duration, and enzyme?

ATP yield = 1 ATP per PCr

Duration = 3-15 seconds

Enzyme = Creatine Kinase (CK)

For glycolytic system what is the ATP yield (both glucose and glycogen), duration of exercise, enzyme, and byproducts?

ATP yield = 2 ATP from glucose, 3 ATP from glycogen

Duration = 15 seconds - 2 minutes

Enzyme = PFK

Byproducts = lactate, hydrogen ions (H+)

What is the end result of anaerobic glycolysis? Pros/cons?

End result = lactate (lactic acid)

Pros = rapid ATP production, doesn’t require oxygen

Cons = low ATP yield, lactate accumulation, fatigue

For oxidative system what is ATP yield (both glucose and glycogen) and duration of exercise?

ATP yield = 32 ATP from glucose, 33 ATP from glycogen

Duration = about 2 minutes

Glycolysis location and overall production

Location = cytoplasm

Produces = 2 ATP (glucose), 3 ATP (glycogen), pyruvate, NADH

Krebs cycle location and overall production

Location = mitochondrial matrix

Produces = 2 ATP, NADH, FADH₂, CO₂

Electron transport chain location and overall production

Location = inner mitochondrial membrane

Produces = ~28-30 ATP, Water

Function of Beta Oxidation

Breakdown fatty acids into acetyl-CoA to enter Krebs cycle

Location, requirement, and result of Beta Oxidation

Location = mitochondria

Requires = oxygen

Result = Acetyl-CoA enters Krebs Cycle, large ATP production, slower than carbohydrate metabolism

Explain the 6 step process of generating an action potential

1. Resting membrane potential (-70 mV) maintained by sodium-potassium pumps

2. Na+ channels open and Na+ moves into the cell, depolarizing it

3. Na+ channels close and K+ channels begin to open to repolarize the cell

4. K+ moves out of the cell (repolarization)

5. Additional K+ moves out of the cell, hyperpolarizing it

6. Cell returns to resting membrane potential

For an action potential, what is the resting membrane potential, action potential threshold, and peak depolarization?

Resting membrane potential = -70 mV

Threshold = -50 mV to -55 mV

Peak depolarization = +30 mV

Muscle spindles vs golgi tendon organs location and function

Muscle spindles = located inside muscle, detect muscle length and initiate muscle contraction to resist further stretching

Golgi tendon organs = located at the tendon, detect tension and inhibit the contracting muscles and excite the antagonist muscles

Explain the structure and function of a neuron

Structure = dendrites, cell body, axon, axon hillock, myelin sheath, node of ranvier, axon terminals

Function = transmit electrical signals throughout the nervous system

How does myelin affect the transmission of an action potential?

The myelin sheath increases the conduction velocity (saltatory conduction)

Transmission of an action potential neuron to neuron vs neuron to muscle

Neuron to neuron = neurotransmitters released at synapse

Neuron to muscle = ACh released at neuromuscular junction

CNS brain vs spinal cord

Brain = integration and processing

Spinal Cord = reflexes and signal transmission

Afferent fibers vs efferent fibers in PNS

Afferent = sensory information to CNS

Efferent = motor information from CNS

Autonomic nervous system, sympathetic vs parasympathetic

Sympathetic = fight or flight, increases HR, BP, glucose release

Parasympathetic = rest and digest, decreases HR, promotes digestion

Steroid vs non-steroid hormones

Steroid hormones = soluble in lipids, cross cell membrane, bind to receptors in the cell, enter the nucleus to bind to part of the cell’s DNA and activate certain genes (ex. cortisol, estrogen, testosterone)

Non-steroid hormones = can’t cross cell membrane, they bind membrane receptors, triggers a series of reactions that lead to the formation of an intracellular second messenger (ex. insulin, glucagon, epinephrine)

Insulin, where is it released from? what does it target? what is its function? its response to exercise?

Released from pancreas

Targets muscle, liver, fat

Function = lowers blood glucose and promotes storage

Exercise response = decreases

Glucagon, where is it released from? what is its function? its response to exercise?

Released from pancreas

Function = raises blood glucose

Exercise response = increases

Epinephrine, where is it released from? what is its function? its response to exercise?

Released from adrenal medulla

Function = glycogen breakdown and fat mobilization

Exercise response = increases

Cortisol, where is it released from? what is its function? its response to exercise?

Released from adrenal cortex

Function = protein breakdown and glucose production

Exercise response = increases with prolonged exercise

What are the hormones active during energy metabolism?

Insuline, glucagon, epinephrine, cortisol

What are the hormones active in fluid and electrolyte balance?

ADH, aldosterone

ADh, where is it released from? what does it target? what is its function? response to exercise?

Released from posterior pituitary

Targets kidneys

Function = water retention

Exercise response = increases

Aldosterone, where is it released from? what does it target? what is its function? response to exercise?

Released from adrenal cortex

Targets kidneys

Function = sodium retention and water retention

Exercise response = increases

What is osmolality and how does it affect ADH?

It is the concentration of dissolved particles in body fluids

Increased osmolality stimulates ADH release

What hormones are involved in the hormonal regulation of caloric intake?

Ghrelin, leptin, CCK, GLP-1, insulin, peptide YY

Ghrelin, where is it released from? what is its function? response to exercise?

Released from stomach

Function = stimulates hunger

Exercise response = usually decreases after exercise

Leptin, where is it released from? what is its function? response to exercise?

Released from fat cells

Function = suppresses appetite

Exercise response = may decrease with reduced body fat

CCK, where is it released from? what is its function? response to exercise?

Released from small intestine

Function = promotes satiety after eating

Exercise response = helps reduce food intake after meals

GLP-1, where is it released from? what is its function? response to exercise?

Released from small intestine

Targets pancreas, stomach, hypothalamus

Function = increases insulin secretion, promotes satiety/reduces hunger

Response to exercise = increases