Exercise Physiology Exam 1

Physical Activity Guidelines for healthy adults

150-300 minutes moderate-intensity aerobic physical activity

or

75-150 minutes of vigorous-intensity aerobic physical activity

After 300 minutes (5 hours) physical activity

additional health benefits gained

MET requirements to be considered physically active

Must reach 450 MET minutes a week

2 muscle-strengthening activities a week

MET

metabolic equivalent

Moderate intensity physical activity MET value

3-6 MET per minute

Vigorous-intensity physical activity

more than 6 MET

Recommendations for strength training

must be two times a week

-dynamic resistance exercises

-full range of motion

-8-10 different exercises

-8-12 repetitions per exercise; resistance set to volitional fatigue

does not need to be progressive weight training- calisthenics and stair climbing okay

Light intensity activity

1.6-3 METs

(walking slowly or standing at work)

Any activity even under 10 minutes is beneficial and counts toward meeting target range

Benefits of moderate vigorous physical activity

-Sleep quality

-executive function

-memory processing speed

-attention

-academic performance

-reduces depressive symptoms and anxiety

-perceived quality of life increases

-physical function

-minimizes weight gain

-prevents dementia

-reduces obesity risk and improves bone health

Central NS

Brain and spinal cord

Peripheral Nervous System

afferent

• somatic sensory

• visceral sensory

• special sensory

Efferent division

• somatic motor

• autonomic motor

  • sympathetic NS

  • parasympathetic NS

  • Enteric
    

Somatic Sensory

Sensory input that is consciously perceived from receptors

Visceral Sensory

Sensory input that is not consciously perceived from receptors of blood vessels and internal organs

Resting membrane potential

The resting membrane potential is the electrical charge difference across a neuron’s membrane when the cell is at rest, typically around –70 mV (ranging from –40 to –90 mV), with the inside of the cell being negative relative to the outside. This potential results from the unequal distribution of ions across the membrane and the selective permeability of the membrane to those ions. Potassium (K⁺) is more concentrated inside the cell and tends to diffuse out through K⁺ leak channels, while sodium (Na⁺) is more concentrated outside and moves in slowly through fewer Na⁺ leak channels. Chloride (Cl⁻) and negatively charged proteins (A⁻) inside the cell also contribute to the negative charge. The sodium–potassium pump (Na⁺/K⁺ ATPase) actively maintains these concentration gradients by pumping three Na⁺ ions out of the cell and two K⁺ ions in, using ATP. Together, the ion gradients, selective ion permeability (especially to K⁺), and Na⁺/K⁺ pump activity maintain the neuron’s stable resting membrane potential.

Which of the following contributes to the negativity of a neuron’s resting membrane potential?

a. [K+] is low inside the neuron

b. [Na+] is high inside the neuron

c. Pumps transfer negatively-charged ions into the cell

d. Channels slowly leak sodium into the extracellular space

e. A neuron contains proteins, phosphates, and nucleotides

e. A neuron contains proteins, phosphates, and nucleotides

How is an action potential created

It begins when a stimulus causes the neuron’s membrane potential to reach a threshold (around –55 mV), triggering voltage-gated Na⁺ channels to open. Sodium ions (Na⁺) rush into the cell by passive diffusion, making the inside of the cell more positive — this is depolarization. Once the membrane potential peaks around +30 mV, Na⁺ channels close and voltage-gated K⁺ channels open. Potassium ions (K⁺) then move out of the cell by passive diffusion, restoring the inside to a more negative state — this is repolarization. Because K⁺ channels close slowly, extra K⁺ leaves the cell, briefly making it more negative than resting potential — this is hyperpolarization. Afterward, the Na⁺/K⁺ pump (active transport) restores the original ion distributions by pumping 3 Na⁺ out and 2 K⁺ in, using ATP. The action potential then propagates down the axon as the depolarization of one region triggers the opening of Na⁺ channels in the next segment, creating a wave-like signal. According to the all-or-none law, once threshold is reached, the action potential occurs completely; if threshold is not reached, it does not occur at all — its size does not vary with stimulus strength.

The rapid repolarization that occurs immediately after a neuron depolarizes is caused by:

a. Passive diffusion of potassium out of the cell

b. Passive diffusion of sodium into the cell

c. Active transport of sodium out of the cell

d. Active transport of potassium into the cell

e. Both c and d above

a. Passive diffusion of potassium out of the cell

Synapyic transmission

When an action potential reaches the axon terminal of the presynaptic neuron, it triggers the release of neurotransmitters from vesicles into the synaptic cleft. These neurotransmitters diffuse across the cleft and bind to specific receptors on the postsynaptic membrane, causing ion channels to open. Depending on the type of neurotransmitter and receptor, the postsynaptic cell experiences either excitatory postsynaptic potentials (EPSPs) or inhibitory postsynaptic potentials (IPSPs). EPSPs occur when positive ions (like Na⁺) enter the cell, making the inside more positive and moving the membrane potential closer to threshold. IPSPs occur when negative ions (like Cl⁻) enter or positive ions (like K⁺) leave, making the inside more negative and moving the membrane potential farther from threshold. The neuron integrates all these inputs through summation. Temporal summation happens when multiple signals from the same presynaptic neuron arrive in quick succession, and spatial summation occurs when inputs from several presynaptic neurons arrive at the same time. Communication is controlled by the balance of EPSPs and IPSPs—only if their combined effect brings the postsynaptic neuron to threshold will an action potential be generated, ensuring that the neuron fires only when it receives sufficient stimulation.

Acetylcholine is a versatile neurotransmitter that creates an EPSP in skeletal muscle (signaling muscle contraction) but slows heart rate by creating an IPSP on the post-synaptic membrane of the SA node of the heart. Which of the following will occur as a result of acetylcholine release in these locations?

a. Membrane channels allow Na+ into myocardial cells

b. Membrane channels allow K+ out of skeletal muscle cells

c. Membrane potential of skeletal muscle becomes more positive

d. Depolarization of cardiac tissue

e. Hyperpolarization of skeletal muscle tissue

c. membrane potential of skeletal muscle becomes more positive

Which proprioceptors would cause the reflex response knee jerk

a. Pacinian corpuscles

b. Golgi-type receptors

c. Muscle spindles

d. Golgi tendon organs

e. Gamma motor neurons

c. Muscle Spindles

Order of Muscle Spindle and posture

1. muscle spindles detect stretch of the muscle

2. Sensory neurons conduct action potentials to the spinal cord

3. Sensory neurons synapse with alpha motor neurons

4. Stimulation of the alpha motor neurons causes the muscle to contract and resist being stretched

Knee jerk reflex is spinal reflex (sends receipt to the brain)

Which proprioceptors (under normal circumstances) would have prevented this man from lifting the wheels of a car 10 inches off the ground?

a. Pacinian corpuscles

b. Golgi-type receptors

c. Muscle spindles

d. Golgi tendon organs

e. Gamma motor neurons

d. Golgi tendon organs

Golgi Tendon Organ

1. Golgi tendon organs detect tension applied to a tendon

2. Sensory neurons conduct action potentials to the spinal cord

3. sensory neurons synapse with inhibitory interneurons that synapse with alpha motor neurons

4. Inhibition of the alpha motor neurons causes muscle relaxation, relieving the tension applied to the tendon

Motor unit recruitment

A motor unit is a motor neuron and all of the muscle fibers it innervates

size principle- recruits the smaller ones first- helps ajust force production

What detects rotation

ampulla

what detects up and down movement

utricle and saccule

Vestibular apparatus

-sensitive to any change in head position or movement

-detects linear and angular accelerations

-relays this information to the vestibular nuclei, thus allowing control of appropriate head and eye movement during physical activity based on non-visual input

-failure of the vestibular apparatus would inhibit any athletic task that requires head movement

Cerebrum: Cerebral cortex

-organizes complex movements

-stores learned experiences

-receives sensory information

Cerebrum- motor cortex

final relay point (after subcortical input) for movement plan

roles from the cerebellum

-coordinates and monitors complex movements with the aid of proprioceptors

-initiates fast ballistic movements

Roles of brainstem

Postural Tone

Eye movement

Equilibrium

Muscle tone

Reciprocal inhibition

Reciprocal inhibition is the process by which activation of one muscle group (the agonist) causes inhibition of its opposing muscle group (the antagonist).

crossed-extensor reflex

The crossed-extensor reflex helps maintain balance and posture when you withdraw from a painful stimulus.

• When you step on something sharp, the withdrawal reflex causes your injured leg to flex (pull away).

• At the same time, the opposite leg undergoes extension to support your body weight.

• This involves sensory input crossing to the opposite side of the spinal cord, activating extensor muscles on the contralateral limb.

Parkinsons

Basal nuclei or “ganglia” malfunction

Difficulty initiating wanted movements

Huntington’s disease

Basal nuclei or ganglia malfunction

Difficulty supressing unwanted movements

From motor cortex to motor units

undergoes spinal tuning

Planning movement 

Subcortical and cortical areas(initial drive to move)→association cortex(rough draft)→ to basal nuclei (slow refined plan) or cerbellum (fast refined plan)→ thalamus (relay station)→motor cortex (final executor of plan)→”spinal tuning”→motor units (executes desired movement)

4 reasons we have skeletal muscle

1. force generation for locomotion

2. force generation for postural support

3. Heat production during periods of cold stress

4. Some endocrine function

End-plate potential

depolarization of the motor end plate that mandatorily exceeds the threshold and signals the beginning of the contractile process

Training adaptations

Endurance and resistance exercise increase the size of the NMJ, the abundance of synaptic vesicles, and Ach receptors

cholinesterase (an enzyme that breaks down acetylcholine).

you’ll die of breathlessness

A band

Everywhere there is thick filament

I band

only thin filament

H zone

only thick filament

(gets shorter during contraction)

Steps of contraction

. A nerve signal arrives at the synaptic knob

2. Synaptic vesicles release acetylcholine, which binds to receptors, opening ion channels and allowing sodium to flow into the fiber.

3. The fiber depolarizes, sending waves through the T-tubules

4. Calcium is released from the sarcoplasmic reticulum into the cytosol

5. Calcium binds to troponin, causing a shift of tropomyosin and exposing binding sites on actin

6. Energized myosin crossbridge binds to active site on actin; Pi released

7. Power stroke causes filaments to slide; ADP is released

8. A new ATP binds to myosin head, allowing release from actin (Repeat steps 6-8 as long as Ca2+ is still available)

9. Motor neuron stops firing; acetylcholine no longer released; fiber repolarized

10. Calcium is pumped from cytosol into SR for storage; tropomyosin covers binding sites, preventing crossbridge formation and muscle relaxes

Is exercise-induced muscle cramps from dehydration and electrolyte imbalances

NOOO

1. Electrolyte imbalance and dehydration affect the whole body

2. Electrical stimulation causes cramping without changing electrolytes

3. static stretching relieves cramps

4. cramp-prone athletes drink the same amount of fluids as other athletes

What causes muscle cramps

Vigorous exercise may cause hyperexcited motor neurons

• dysfunction of muscle spindle or golgi tendon organ

• stop and stretch to fix cramps!

What does not remedy cramps

salt tablets

bananas

pickle juice

sports drinks