Detailed Study Notes on Nervous and Muscular Systems

Coursework Overview and Future Topics

  • Focus on lighter elements regarding muscle physiology
  • Action potentials and detailed physiology scheduled for next Tuesday
  • Lab Nine materials will be addressed after the exam on Thursday
  • Aim to address early sections of Lab Nine and Topic 11 worksheets

Nervous and Muscular Systems Overview

  • Reminder to focus on muscular system knowledge
  • Brief overview of nervous system components, specifically neuron types, will be provided

Muscle Anatomy Review

  • Last week’s session included:
    • Muscle cell anatomy review using models
    • Diagrams of skeletal muscle cells
    • Understanding of sarcomere structures: banding pattern, locations of myosin and actin, presence of Z lines and I bands
  • Importance of reviewing this material as it will appear on the exam

Neuron Structure Types

  • Multipolar Neurons

    • Structural description: characterized by multiple extensions (dendrites and one axon) from the cell body
    • Terminology breakdown:
    • "Multi" means many, indicating numerous poles/extensions
    • Functional Example:
    • Typically a motor neuron, responsible for transmitting signals from the CNS (central nervous system) to the PNS (peripheral nervous system)
    • Example of a multipolar neuron: one that transmits to cardiac muscle or glands

  • Pseudounipolar Neurons

    • Structural description: a single extension (axon) that splits into two branches, which act as both dendrites and axon
    • Definition of "pseudounipolar": appears to have one pole but has branches, hence 'pseudo' (false)
    • Functional Example:
    • Typical sensory neuron, such as one that carries touch information from fingertips to the CNS
    • This neuron conveys sensory information from the PNS to the CNS

  • Bipolar Neurons

    • Structural description: characterized by two extensions coming off the cell body
    • Functional Example:
    • Commonly associated with special senses, such as vision in the retina, smell in the nasal cavity, and hearing/balance in the ear

Importance of Structural Understanding

  • All three neuron types are foundational for understanding neurophysiological functions
  • Revisiting slides (including diagrams of neuron types) to reinforce anatomical and functional knowledge in labs and discussions

Myelination and Action Potential

  • Myelin role discussed, with relation to action potentials and axonal conditions
  • **Myelin Function: **
    • Provides insulation which increases the speed of action potentials due to a phenomenon known as saltatory conduction
    • Action potentials jump between the nodes of Ranvier, enhancing signal transmission speed
  • Gaps between myelinated sections are referred to as nodes of Ranvier

Neuroglia (Supporting Cells)

  • Distinction between neurons and neuroglia:
    • Neurons generate action potentials, while neuroglia are supporting cells that assist neurons

Types of Neuroglia

  • Microglia
    • Function: act as immune cells in the CNS, providing defense against pathogens and clearing debris
  • Astrocytes
    • Maintain ionic balance in the CNS and protect CNS environment (e.g., regulate the blood-brain barrier)
    • Functions include supporting and nourishing neurons, facilitating nutrient exchange and keeping the environment optimal
  • Ependymal Cells
    • Line ventricles of the brain and spinal cord; create and circulate cerebrospinal fluid (CSF)
  • Oligodendrocytes
    • Responsible for myelination of axons in the CNS—can myelinate multiple axons
  • Schwann Cells
    • Myelinate axons in the PNS on a one-to-one basis
  • Satellite Cells
    • Support neurons in the PNS by keeping ionic environments clean

Resting Membrane Potential (RMP)

  • Definition: The resting membrane potential refers to the voltage (approximately -70 mV) across the neuronal membrane when the neuron is not firing an action potential

Mechanisms Maintaining RMP

  • The sodium-potassium pump maintains the negative charge by moving sodium ions out and potassium ions in, using active transport:
    • This pump works against concentration gradients and requires ATP
    • Consistently pumps 3 sodium ions out for every 2 potassium ions brought in, leading to a net negative charge
  • Passive transport phenomena:
    • Sodium influx and potassium efflux occur simultaneously but at different rates, contributing to a stable membrane potential
  • Selective permeability of the neuronal membrane traps negative ions inside, which also supports the maintenance of a negative membrane state

Conclusion and Further Actions

  • Encouragement to review notes while progressing through worksheets
  • Focus on understanding the implications of physiological mechanisms discussed before the next session on action potentials due next week
  • Preparation for upcoming exam topics, specifically muscle cell anatomy and neuron classifications.