Exam 1 Kines 350 Study Guide

Physiology

study of how cells, tissues, organs and organ systems function

Exercise physiology

how exercise influences the function of cells, tissues, organs and systems

acute response

• short term/immediate after single bout of exercise 

  • Increased HR, BP

chronic response

• long term from repeated training

  • Increased VO2max, stronger muscles

Why is exercise considered a physiological stressor?

Disrupts homeostasis and challenges the body

What are the four variables used to describe exercise?

Mode, duration, frequency, intensity 

What SI unit is used for force?

N

What SI unit is used for power?

W

Work def

when force moves object through a distance against resistance

Power def

rate at which work is performed

List four common ergometers used in exercise physiology

Bench step, Cycle, Arm, Treadmill

How to convert kg to N

m x 9.81

What are the three major functions of the nervous system? 

Perception → Response → Memory/Learning

Afferent pathway

towards (sensory), Vision, touch, pain, Receptors → CNS (info)

efferent pathway

away (motor), Types of muscle (smooth, skeletal), CNS → effectors (commands)

3. Which lobe of the cerebrum is primarily responsible for motor control? 

frontal lobe

4. What functions are regulated by the hypothalamus? 

homeostasis: Hunger, thirst, temp, BP, HR, breathing

5. Why does myelin increase conduction velocity? 

Conduct impulses fast → insulator = no leakage

Describe the role of the sodium-potassium pump. 

Active transport, Pump out 3Na+ and in 2K, Maintains ion gradients

Depolarization

stimulus threshold reached

Repolarization

returns to resting membrane potential

8. What is meant by the all-or-none law? 

Once at threshold, full AP occurs and signal travels entire axon

temporal summation

multiple EPSPs from one neuron arrive rapidl

spatial summation

EPSPs from multiple neurons arrive simultaneously

IPSP function

inhibits

EPSP function

excites

Cerebrum

• Left and right hemispheres

• Consciousness, intellect, awareness

Frontal lobe

Motor control

Basal ganglia

Posture, repetitive movements, walking/running

thalamus

Sensory relay center/awareness of sensory info

Hypothalamus

Master regulator of homeostasis

Cerebellum

Coordination and balance

Brain stem

Relays info btw brain and spinal cord, regulates breathing, controls muscle tone

Spinal cord

Carry sensory info to brain, carry motor commands from brain

Homeostasis

Stable internal environment

Somatic nervous system

Voluntary, skeletal muscles

Autonomic nervous system

Involuntary, smooth/cardiac muscle

Sympathetic division

Fight or flight

Parasympathetic division

Rest and digest/relaxed

Neuron

Functional unit of nervous system

Myelin sheath

insulation/ increase conduction

Saltatory conduction

AP jump node to node along myelinated axons

Multiple sclerosis

Autoimmune disease attacks myelin in CNS

Synapse

Small gap between presynaptic and postsynaptic neuron

CNS

Brain + Spinal Cord

PNS

Sensory (Afferent) + Motor (Efferent)

Concentric

muscle shortens

Eccentric

muscle lengthening

Isometric

muscle stays same length

2. What occurs during the latent period of a muscle twitch?

• Muscle fiber depolarizes

• excitation-contraction coupling

3. Why do fast-twitch fibers contract more rapidly than slow fibers?

• Faster; greater ATPase activity and faster Ca2+ release 

Summation def

another stimulus arrives before complete relaxation so extra Ca2+ in cell, more cross-bridges and force increases

Tetanus

high stimulation frequencies produce sustained contraction and max force production

length-tension relationship

Optimal = max force since cross-bridge formation optimal overlap

1. Why is grip strength stronger when the wrist is slightly extended compared to flexed?

Finger flexors operate near optimal length due to optimal overlap so optimal length

2. Explain why maximal force production occurs at slower movement velocities.

• Muscles have more time to form cross-bridges, more cross-bridges = more force

3. Why does power decrease at extremely high movement velocities?

• Force decreases; peak when velocity = moderate 

4. How does motor neuron firing frequency affect force production?

• Force depends on stimulation frequency (continuous = better)

5. Why are sprinters generally more powerful than marathon runners?

• More fast twitch fibers (70-75%) in sprinters

  • Produce more force, fire faster (type II)

Muscle twitch phases

latent (immediate), contraction (Ca released), relaxation (Ca to SR)

Force-velocity relationship

• As contraction increases, force a muscle can develop decreases

Power-velocity relationship

• Peak power occurs at an intermediate velocity 

fast fiber function

greater power/sprinters; dominant

slow fiber function

fatigue resistance/efficiency

Sarcopenia and aging effects on muscle performance

Loss of skeletal muscle mass, loss of fast-twitch fibers and increase slow-twitch

Velocity fiber types

IIx → IIa → I

power fiber types

IIx → IIa → I

fatigue resistance fiber types

I → IIa → IIx

Mitochondria fiber types

 I → IIa → IIx

Define muscle fatigue

Decline in muscle power output

2. How do H⁺ ions contribute to fatigue?

• Accumulation of them; compete w/ Ca binding sites on troponin which reduces Ca ability to activate contraction

3. What role does glycogen depletion play in endurance fatigue?

• Reduced carbs, TCA cycle intermediates and ATP production through oxidative phosphorylation 

leading theory for exercise-associated muscle cramps.

muscle spindle activity increases and golgi tendon inhibition decreases creating excitatory input

5. Why does passive stretching often relieve cramps?

• Increases golgi activation, enhances inhibitory signaling and reduces motor neuron activity

9. How are muscle fiber types determined experimentally?

• Muscle biopsy, gel electrophoresis, immunohistochemical staining

10. Why do elite sprinters have a higher proportion of Type II fibers?

• Rapid force production, max power output, high shortening velocity

2. Describe why a 100-meter sprinter would fatigue rapidly if forced to run a marathon.

• Limited slow twitch fibers; rapid force production, low fatigue resistance

High Intensity Fatigue

• H⁺

• Pi

• Free radicals

• Reduced Ca²⁺ release

Long Duration Fatigue

• Glycogen depletion

• Free radicals

Cramp Theory

dehydration and altered neuromuscular control

Strength training can increase:

• Motor unit activation

• Force production

• Muscle hypertrophy

Fatigue can result from:

• Reduced ATP availability

• Impaired Ca²⁺ handling

• Reduced motor neuron activation

During contraction:

• Sarcomeres shorten.

• Z lines move closer together.

End Plate Potential (EPP)

always large enough to trigger a muscle action potential

Excitation-contraction coupling

Muscle AP → T-Tubules → SR → Ca²⁺ Release → Contraction

Muscle Organization Hierarchy

Muscle → Fascicle → Muscle Fiber → Myofibril → Sarcomere → Actin & Myosin

ATP Hydrolysis

• ATP is broken down by myosin ATPase:

  • 𝐴TP → ADP + Pi + energy

Sources of ATP

Glycolysis, oxidative phosphorylation, phosphocreatine system (PCr), cross-bridge cycling

Sliding filament theory 

Swinging lever arm model; sarcomere shortens = actin slides over myosin

Motor End Plate

• Specialized region of the sarcolemma surrounding the motor neuron terminal. Skeletal

Acetylcholine (ACh)

• Primary neurotransmitter released from motor neurons

Epimysium

• Surrounds whole body

Perimysium

• Surrounds fascicles 

Endomysium

• Surrounds individual muscle fibers

Sarcolemma

• Muscle cell membrane 

Sarcoplasmic reticulum

• Stores Ca2+, Ca2+ from SR is the trigger for contraction

T-tubules

• Invaginations of the sarcolemma extending deep into the muscle fiber

Actin

• Thin filament

Troponin

• Calcium binds to it

Tropomyosin

• Blocks myosin-binding sites on actin