Week 3

Question 1

Functions of the Nervous System?

Answer 1

Controls the internal environment (in coordination with the endocrine system)

Regulates voluntary movement

Processes and responds to sensory input

Integrates spinal cord reflexes

Facilitates memory and learning

Question 2

Anatomical Divisions of the Nervous System?

Answer 2

1. Central Nervous System (CNS):
   Composed of the brain and spinal cord

Responsible for integration and processing of information

2. Peripheral Nervous System (PNS):
   Consists of all neurons outside the CNS

Divided into:

Sensory (afferent) division: Carries signals to the CNS from receptors

Motor (efferent) division: Carries signals from the CNS to effectors (muscles and glands)

Question 3

Structure of a Neuron?

Answer 3

Axon: Transmitsaction potentialsaway from the cell body.

Schwann cells: Insulate axon by forming themyelin sheath, which speeds up signal transmission.

Synapse: Connection between the axon of one neuron and the dendrite of another.

Also, Larger axon diameterandthicker myelin sheath=faster signal transmission

Question 4

Functional organisation of the nervous system?

Answer 4

Input = Sensory nervous system ( detects stimuli and transmits information from the receptors to CNS)

Branches into:

• Somatic sensory - sensory input consciously perceived from receptors eg eyes, ears, skin
• Visceral sensory - not consciously perceived from receptors of blood vessels and internal organs eg heart

Output = Motor nervous system - initiates and transmits information from the CNS to effectors

Branches into:

• Somatic motor - motor output that is consciously or voluntarily controlled, effects is skeletal muscle
• Autonomic motor - not consciously or is involuntarily controlled, effects are cardiac, and smooth muscle and glands

Question 5

Multiple Sclerosis (MS)?

Answer 5

Autoimmune disorderthat destroysmyelin sheaths, leading to:
- Muscle weakness
- Fatigue
- Loss of motor control
- Poor balance
- Depression
Exercise trainingcan improvefunctional capacityandquality of life.

Question 6

Electrical Activity in Neurons?

Answer 6

• Negative chargeinside the cell at rest (40 to -75 mV in neurons).
• Maintained by:
  
  1. Selective permeabilityof the membrane.
  2. Ion concentration differences(Na+, K+, Cl-).

🔄Sodium-Potassium Pump

• Activelymoves 3 Na+ out and 2 K+ intothe cell, maintainingnegative RMP.

Action Potential (AP) – The Nerve Impulse

1. Depolarization:
   
   • Na+ channels open, Na+ rushesintothe cell.
   • Inside the neuron becomesmore positive.
2. Repolarization:
   
   • K+ exitsthe cell quickly, restoringnegative charge.
   • Na+ channels close.
3. All-or-None Law:
   
   • Once an action potential starts, ittravels the full length of the neuron.

Question 7

Neurotransmitters & Synaptic Transmission?

Answer 7

• Neurotransmitters: Chemical messengers released from thepresynaptic neuron.
• Bind to receptors onpostsynaptic neuron, causingdepolarization.

Question 8

Types of Synaptic Potentials?

Answer 8

1. Excitatory Postsynaptic Potentials (EPSPs)
   
   • Promote depolarization, bringing the neuroncloser to threshold.
   • Summation mechanisms:
     
     • Temporal summation: Rapid, repeated EPSPs from a single neuron.
     • Spatial summation: Multiple neurons releasing EPSPs simultaneously.
2. Inhibitory Postsynaptic Potentials (IPSPs)
   
   • Causehyperpolarization(more negative potential).
   • Inhibit depolarization, making neuronless likely to fire.

Question 9

Sensory Information and Reflexes?

Answer 9

Proprioceptors – The “Sixth Sense”

• Providesensory feedbackaboutbody position and movement.

1. Joint Proprioceptors

• Free nerve endings: Detect touch and pressure.
• Golgi-type receptors: Found injoint ligaments, detect movement.

2. Muscle Proprioceptors (Mechanoreceptors)

• Muscle spindles: Detect changes inmuscle length.
• Golgi Tendon Organs (GTOs): Monitormuscle force, preventing excessive force generation.

💡Training adaptation: Athletes canoverride GTO inhibition, leading toincreased strength.

3. Muscle Chemoreceptors (Metaboreceptors)

• Detect chemical changes:
  
  • H+ ions (pH changes), CO2, and K+.
• Provide feedback toCNSfor cardiovascular and pulmonary regulation.

Question 10

Key Structures of the Brain?

Answer 10

1. Cerebrum (Cerebral Cortex)
   
   • Controls voluntary movement.
   • Storeslearned experiences.
   • Processessensory input.
2. Cerebellum
   
   • Coordinatesmovement and balance.
3. Brainstem (Midbrain, Pons, Medulla)
   
   • Regulatescardiorespiratory function, posture, and muscle tone.

Question 11

Sports-Related Traumatic Brain Injury (TBI)?

Answer 11

Concussions (Mild TBI)

Symptoms can bephysical, cognitive, emotional, or sleep-related:
Physical - Headache, nausea, vomiting, vision issues
Cognitive - Memory loss, confusion, slow responses
Emotional - Irritability, sadness, nervousness
Sleep - Insomnia, excessive sleepiness

Question 12

Spinal Cord and Voluntary Movement?

Answer 12

• 45 cm long, encased and protected by bony vertebral
  column, and attaches to brainstem
• Major conduit for two-way transmission of information from
  skin, joints, and muscles to brain
• Major pathway forsensory and motor information.
• Containsmotor, sensory, and interneurons.
• Spinal tuning: Central networksrefine voluntary movement.

Question 13

Control of Voluntary Movement?

Answer 13

• Motor Cortex(Brain) receives input from:
• Basal nuclei(movement planning).
• Cerebellum(movement coordination).
• Thalamus(sensory integration).

Question 14

Exercise and Brain Health?

Answer 14

Regularexercise enhances cognitive functionand protects against:
Alzheimer’s Disease, Stroke, Cognitive decline with aging

Question 15

Mechanisms of Exercise Benefits?

Answer 15

• Stimulatesneurogenesis (new neurons).
• Improvesblood flow and vascular function.
• Reducesinflammation, hypertension, insulin resistance.
• Enhancesmood and reduces depression risk.

Question 16

Main functions of skeletal muscle?

Answer 16

Locomotion & breathing (force production).
Postural support (stability).
Heat production (thermoregulation).
Endocrine function (hormone secretion).

Question 17

Muscle Actions?

Answer 17

• Flexors → Decrease joint angle.
• Extensors → Increase joint angle.
• Attachment: Origin (fixed) & Insertion (moves).

Question 18

Structure of Skeletal Muscle?

Answer 18

Connective Tissue Layers: Surrounding skeletal muscle
- Epimysium → Surrounds the entire muscle.
- Perimysium → Surrounds fascicles (muscle fiber bundles).
- Endomysium → Surrounds individual muscle fibers.
- Basement membrane → Below endomysium.
- Sarcolemma → Muscle cell membrane.

Question 19

Microstructures of muscle fibres?

Answer 19

• Myofibrils & Contractile Proteins:
  
  • Actin (thin filament) & Myosin (thick filament).
  • Sarcomere structure: Z line, M line, H zone, A band, I band.
• Tubular Systems:
  
  • Sarcoplasmic Reticulum (SR): Calcium storage.
  • Terminal Cisternae: Expanded SR regions.
  • Transverse Tubules (T-tubules): Carry electrical signals.

Question 20

Satellite Cells & Muscle Growth?

Answer 20

• Satellite cells aid in muscle repair and hypertrophy.
• Myonuclear domain: Sarcoplasm controlled by one nucleus.
• Hypertrophy → More myonuclei → Greater protein synthesis.
• Atrophy → Fewer myonuclei → Decreased muscle function.

Question 21

Neuromuscular Junction (NMJ)?

Answer 21

• Junction between motor neuron & muscle fiber.
• Key Components:
  
  • Motor end plate → Sarcolemma pocket around the neuron.
  • Neuromuscular cleft → Small gap for neurotransmitter exchange.
  • Acetylcholine (ACh):
    
    • Released from neuron → Binds to receptors → Muscle depolarization → Contraction.
• Trainability of NMJ:
  
  • Larger NMJ, more synaptic vesicles (ACh), more ACh receptors → Enhanced performance.

Question 22

Sliding Filament Model & Contraction Cycle?

Answer 22

• Muscle shortens as actin slides over myosin.
• Steps:
  
  1. Cross-bridge formation (actin-myosin binding).
  2. Power stroke (filament movement via ATP hydrolysis).
  3. Cross-bridge detachment (new ATP binds).
  4. Reactivation of myosin head (ATP hydrolysis resets position).
• ATP sources:
  
  • Phosphocreatine (PCr), glycolysis, oxidative phosphorylation.

Question 23

Excitation-Contraction Coupling (E-C Coupling)?

Answer 23

• Process:
  
  1. Action potential travels down T-tubules.
  2. Calcium released from SR.
  3. Calcium binds to troponin → Tropomyosin moves.
  4. Myosin binding sites on actin exposed → Cross-bridge formation.
  5. Contraction continues with ATP & calcium.
  6. When neural activity stops, calcium is pumped back into SR → Muscle relaxes.

Question 24

Muscle Fatigue & Exercise-Associated Muscle Cramps (EAMC)? Solutions?

Answer 24

• Muscle Fatigue Causes:
  
  • Heavy exercise (1-10 min):
    
    • ↓ Calcium release from SR.
    • Accumulation of Pi, H+, free radicals → Weakens actin-myosin interaction.
  • Moderate exercise (>60 min):
    
    • Glycogen depletion → Less ATP production.
    • Increased radical production damages muscle proteins.
• EAMC Causes:
  
  • Not primarily electrolyte imbalance.
  • Likely due to hyperactive spinal motor neurons.
  • Altered muscle spindle & Golgi tendon organ activity.
• Solutions:
  
  • Stretching.
  • Activating transient receptor potential channels (mouth/throat stimulation).

Question 25

Muscle Actions & Contraction Types?

Answer 25

- Dynamic (Isotonic) - Concentric: Muscle shortens (lifting a weight). - Eccentric: Muscle lengthens (lowering a weight). - Static (Isometric) - No length change (planks, wall sits). - Isokinetic: Constant velocity contractions (dynamometer testing).

Question 26

Muscle fibre type characteristics ? and which each fibre type is?

Answer 26

Mitochondria density Fatigue resistance Energy systems ATPase Activity Contraction speed Efficiency Specific tension Type I - High High Aerobic Low Slow High Moderate Type IIa - Moderate Moderate Mixed High Fast Moderate High Type IIx - Low Low Anaerobic Highest Fastest Low High

Question 27

Fiber Type Distribution?

Answer 27

- Endurance Athletes: ~70-80% Type I fibers. - Sprinters: ~70-75% Type II fibers. - Non-athletes: ~50% Type I, 50% Type II.

Question 28

Motor Units & Force Regulation?

Answer 28

- Motor Unit = Motor Neuron + All Innervated Muscle Fibers. - Henneman's Size Principle: - Small units (low force, fatigue-resistant) recruited first. - Large units (high force, fatigue-prone) recruited as needed. - Force Regulation Factors: 1. Number & type of motor units activated. 2. Muscle length (optimal sarcomere overlap). 3. Firing rate of motor neurons (twitch, summation, tetanus). 4. Contractile history (fatigue vs. potentiation from warm-up)

Question 29

Force-Velocity & Force-Power Relationships?

Answer 29

- Force-Velocity: - Higher force → Lower velocity. - Fast-twitch fibers = Greater velocity at any given force. - Force-Power: - Peak power at 200-300°/sec. - Beyond this, force decreases at higher speeds.

Question 30

Muscle Aging & Disease? Brief summary?

Answer 30

- Sarcopenia (Age-Related Muscle Loss): - 10% loss from 25-50 years. - 40% additional loss from 50-80 years. - Shift from fast to slow fibers. - Resistance training slows progression. - Cachexia (Disease-Related Muscle Loss): - Common in cancer & diabetes. - 50% of cancer patients experience severe muscle wasting. - Exercise & nutrition therapy help. - Muscular Dystrophy: - Genetic disorder causing progressive muscle fiber loss. - Duchenne MD most common in children.

Question 31

Strength Loss with Age?

Answer 31

- Annual decline: - Men: ~3–4% per year. - Women: ~2.5–3% per year. *(Goodpaster et al., 2006)* - Lower body muscles experience greater strength losses. 40% compared to 33%

Question 32

Muscle Power & Function?

Answer 32

- Power = Force × Velocity - Older adults exhibit: - Lower muscle power. - Slower rate of force development. - Higher risk of falls. Key Study: Van Roie et al. (2018) - Muscle power declines significantly with age. - Women tend to lose velocity faster than men.

Question 33

Causes of Age-Related Functional Declines?

Answer 33

Muscle Mass Loss (Sarcopenia & Atrophy) - Muscle loss rate: - 40+ years: ~8% per decade (0.5–1% per year). - 70+ years: ~15% per decade. *(Janssen et al., 2000)* - By 70–80 years, most individuals have only 60–80% of the muscle mass they had at age 30. - Greater loss in lower limbs than upper limbs. Muscle Quality Decline - Increased fat accumulation in and around muscles: - Intermuscular fat (IMF). - Subcutaneous fat (SF). - Fat infiltration reduces muscle force production. Key Studies: - Older adults have more fat & less muscle in thigh muscles. *(Power et al., 2014)* - Increased fat content = Lower muscle quality. Neuromuscular Alterations Motor Unit (MU) Changes - Fewer motor units with age. - Muscle fibres become denervated, leading to: - Fibre atrophy. - Fibre loss. - Reinnervation by Type I motor units (slower contractions). - Larger motor units compensate but reduce fine motor control. Key Studies: - Campbell et al. (1973): Fewer motor units = Less force. - Wilkinson et al. (2018): Reinnervation by Type I units leads to less efficient muscle function. Denervation & Reinnervation - Type II fibres either: - Atrophy (due to lack of innervation). - Get reinnervated by Type I motor units. - Reinnervated fibres are less powerful but more fatigue-resistant. Effects: - More fatigue resistance. - Less force & slower movements → Higher fall risk.

Question 34

Muscle Fibre Changes?

Answer 34

- Type II fibres shrink more than Type I fibres. - Total muscle fibre numbers decrease, but Type I proportion remains stable. *(Lexell et al., 1988)* Key Findings: - Muscle loss ≠ Strength loss. - Strength loss is much greater than muscle mass loss. *(Delmonico et al., 2009)*

Question 35

Fatigue Resistance in Old Age?

Answer 35

- Older adults are less fatigable than young adults in certain tasks. - Due to: - More Type I-like fibres (slow-twitch, endurance). - Altered neuromuscular activation patterns.

Question 36

Effect of Lifelong Exercise on Muscle Ageing?

Answer 36

Master Athletes & Lifelong Exercisers - Lifelong training preserves muscle function but does not prevent all ageing effects. - Master athletes maintain: - Higher muscle power. - Better Type I fibre preservation. - Greater force production (similar to people 30 years younger). Key Study: Piasecki et al. (2016) - Lifelong exercise does not prevent motor unit enlargement. - Muscle deterioration still occurs but is less severe.