Lecture on Exercise Physiology and the Nervous System

Reporting and Performance Metrics

  • Discussion of exercise performance metrics, particularly in endurance vs. strength training contexts.
    • Initial estimate of performance levels is 80%, but more realistically about 75% may be accurate for many individuals.
    • The concept that performance metrics can vary greatly between individuals and should not be viewed as an absolute number.

Weightlifting Guidelines

  • Important considerations in weightlifting include:
    • The number of repetitions a weight can be lifted (e.g., curls, leg extensions).
    • Reaching a point (failure) where another lift is not achievable.
    • Key lifts mentioned: pull-ups, chin-ups, push-ups, sit-ups.
  • Guidelines for using weight machines:
    • Recommended repetition range: 10 to 12 lifts.
    • Identifying appropriate weight:
    • If unable to lift 10 times, the weight is too heavy.
    • If able to lift more than 12 times, the weight is too light.
    • Proper adjustment of seat/backrest crucial for aligning pivot points with body parts.

Understanding Exercise Fatigue

  • Fatigue can be regarded as the inability to maintain sustained contractions.
  • Aerobic vs Anaerobic performance:
    • In running, swimming, and biking, maintaining pace above anaerobic threshold (e.g., 85% intensity) is a key performance factor.
    • General belief that maintaining a lower intensity pace (65%) can be sustained longer compared to higher intensities (78%, 86%, 98%).
  • Illustrative examples:
    • One cannot sustain a race pace for a longer distance event, like a 5K.
    • Specific scenarios to understand fatigue include:
    • Holding a weight while trying to align a bolt (fatigue occurs after holding for a duration).
    • Situations in rock climbing where muscle fatigue may lead one to relinquish hold to prevent falling.

Causes of Fatigue

  • Factors leading to fatigue include:
    • Depletion of stored ATP (energy source) which lasts approximately 8 to 10 seconds at high intensity via energy system number one.
    • ATP includes cytoplasmic ATP and creatine phosphate.
    • Accumulation of intramuscular lactic acid, resulting in decreased pH:
    • Each biochemical reaction has an optimal pH; suboptimal pH results in reduced efficiency of reactions.
    • Depletion of stored glycogen shifts the body to fat metabolism:
    • If glycogen is low, fat becomes the primary energy source, but fat metabolism requires aerobic conditions.
    • Disruption of sodium and potassium concentrations:
    • Sodium has low intracellular and high extracellular concentrations, while potassium has high intracellular and low extracellular concentrations.
    • Concentration gradients must be maintained for proper cellular function.
  • Fatigue experience parallels situations in sports and physical activity, where prolonged strain may necessitate resting or pausing to recover.

Muscle Contractions

  • Types of muscle contractions:
    • Isotonic contractions involve movement, while isometric contractions maintain constant muscle length despite exerting force.
    • Example of isometric contraction: Holding up weights in a static position.
  • Terms explained:
    • "Iso-" as in isotonic, relates to maintaining length during contraction.
    • "Metric" indicates length in terms of isotonic contractions.

Introduction to the Nervous System

  • Organization of nervous system as two primary components:
    • Central Nervous System (CNS): comprises brain and spinal cord, responsible for processing information.
    • Peripheral Nervous System (PNS): involved in conducting information via cranial and spinal nerves.

Central Nervous System (CNS)

  • CNS functions include:
    • Processing and conducting information through the spinal cord and brain.
    • Example: Reflexes like the knee-jerk reflex occur through spinal cord processing, even in the absence of brain input.

Peripheral Nervous System (PNS)

  • PNS conducts sensory and motor information:
    • Cranial Nerves: 12 pairs connected to the brain.
    • Spinal Nerves: 31 pairs connected to the spinal cord.
    • Motor signals originate in the brain, travel through the spinal cord, and out via spinal nerves.
  • Sensory information enters the CNS via sensory nerves and is processed in the parietal lobe.

Brain Functionality

  • Differentiation among brain functions:
    • Frontal Lobe: Involved in motor functions and higher cognitive processes (e.g., planning, decision-making)
    • Parietal Lobe: Processes sensory information like touch, and temperature.

Complexity and Development of the Frontal Lobe

  • Frontal lobe functions evolve with age and experience, reaching full development around age 21 to 25 or even later in some individuals.
  • Formative experiences can shape logic, planning, and understanding of social norms over time.

Peripheral Nervous System Divisions

  • The PNS is divided into two primary systems:
    • Somatic Nervous System: Voluntary movements (e.g., writing, walking).
    • Autonomic Nervous System: Involuntary functions important for maintaining homeostasis (e.g., sweating, heart rate).

Autonomic Nervous System Functionality

  • Autonomic functions characterized by two branches:
    • Sympathetic Nervous System: Activates during stress or activity (increased heart rate, dilated pupils).
    • Parasympathetic Nervous System: Activates during rest and relaxation (slowed heart rate).
    • Connection between activities and autonomic responses explained through everyday scenarios.
  • Notable exceptions include pedal reflexes and sexual responses that cannot be easily categorized as sympathetic or parasympathetic.

Neurons and Neuroglia

  • Two major cell types in nervous tissue:
    • Neurons: Conduct action potentials, essential for nervous system signaling.
    • Neuroglia: Provide support, protection, and nutrition for neurons; do not conduct signals.
  • Neurons may be differentiated based on direction of signal flow:
    • Axons: Usually a single, transmit signals away from the cell body.
    • Dendrites: Multiple, receive incoming signals toward the cell body.

Structure of Neurons

  • Neurons' notable structural features:
    • Components: Cell body (contains nucleus), axons, and dendrites.
    • Synapses represent junctions between neurons facilitating signal transmission pathways.

Neuron Types and Functions

  • Category classifications of neurons:
    • Sensory Neurons: Conduct signals toward CNS.
    • Motor Neurons: Conduct signals away from CNS.

Neuroglial Cells Functionality

  • Different types of neuroglia functioning within CNS vs PNS discussed, including:
    • Ependymal Cells: Ciliated cells that produce and circulate cerebrospinal fluid.
    • Astrocytes: Form blood-brain barrier, regulate substance exchange between brain and blood.
    • Oligodendrocytes: Provide insulation for axons in the CNS.
    • Schwann Cells: Insulate axons in the PNS.
    • Microglia: Phagocytes that remove debris and dead cells from the nervous system.

CNS Vs PNS Schwann and Oligodendrocytes

  • Both Schwann and oligodendrocytes wrap around axons providing myelin insulation to increase conduction velocity.
    • Myelin sheath increases conduction speed from about 10 m/s to about 100 m/s.
  • An overview of diseases affecting myelin sheath, e.g., multiple sclerosis, characterized by an autoimmune attack on myelin-producing cells.

Important Neurotransmitter Functions

  • Acetylcholine: Body's most prevalent neurotransmitter, released at synapses to facilitate neuron signaling.
  • Understanding the essentiality of neurotransmitters in brain function and learning processes discussed.

Key Terms and Definitions

  • Nerve: A group of nerve cell processes in the PNS.

  • Tract: A group of nerve cell processes in the CNS.

  • Understanding distinctions between sensory, motor, and mixed nerves is critical for grasping nerve functionalities.

  • Ascending Tracts: Conduct signals upwards towards the brain, typically sensory information.

  • Descending Tracts: Conduct signals downwards from the brain, typically motor commands.

This document encompasses definitions, explanations of physiological concepts, and examples related to the topics discussed in the transcript, creating an exhaustive and encyclopedic study guide for a university student.