Podcast
Questions and Answers
What is the primary function of microglia in the nervous system?
What is the primary function of microglia in the nervous system?
Which type of glia is responsible for myelin formation in the central nervous system?
Which type of glia is responsible for myelin formation in the central nervous system?
What is a consequence of myelin loss in conditions like multiple sclerosis?
What is a consequence of myelin loss in conditions like multiple sclerosis?
Which of the following statements is true regarding Schwann cells?
Which of the following statements is true regarding Schwann cells?
Signup and view all the answers
Charcot-Marie-Tooth disease is primarily caused by mutations in which of the following?
Charcot-Marie-Tooth disease is primarily caused by mutations in which of the following?
Signup and view all the answers
What occurs during the absolute refractory period?
What occurs during the absolute refractory period?
Signup and view all the answers
Which statement correctly describes the role of electrotonic depolarization?
Which statement correctly describes the role of electrotonic depolarization?
Signup and view all the answers
During which phase of the spike potential is the neuron most refractory to stimulation?
During which phase of the spike potential is the neuron most refractory to stimulation?
Signup and view all the answers
What phenomenon occurs in myelinated axons regarding action potential propagation?
What phenomenon occurs in myelinated axons regarding action potential propagation?
Signup and view all the answers
What happens to the nerve cell membrane during an action potential?
What happens to the nerve cell membrane during an action potential?
Signup and view all the answers
Study Notes
Action Potential and Refractory Periods
- During local response, the neuron's excitation threshold decreases; during spike potential phases, it becomes refractory to stimulation.
- Refractory period consists of two phases: absolute (no stimulus can evoke an action potential) and relative (stronger stimuli can result in excitation).
- Absolute refractory period spans from the firing level to about one-third completion of repolarization.
Nerve Membrane Polarization
- At rest, nerve cell membranes are polarized, having positive charges outside and negative charges inside.
- During action potential, membrane polarization is reversed temporarily.
- Positive charges flow into the area of negativity, reducing polarity and initiating local responses.
Conduction and Myelination
- In myelinated axons, depolarization appears to jump between nodes of Ranvier (saltatory conduction).
- Oligodendrocytes (CNS) and Schwann cells (PNS) are responsible for myelin formation around axons.
- Oligodendrocytes sheathe multiple axons, while Schwann cells wrap around a single axon.
Microglia and Immune Response
- Microglia act as immune system scavenger cells, removing debris from injury and disease.
- They originate from macrophages and are distinct from other neural cell types.
- The presence of microglia is notable in diseases like multiple sclerosis (MS) and neurodegenerative disorders.
Myelin-Related Conditions
- MS is characterized by patchy myelin destruction in the CNS, leading to delayed conduction.
- Autoimmune reactions to myelin proteins (P0 and PMP22) can result in Guillain–Barré syndrome.
- Charcot-Marie-Tooth disease is linked to mutations in myelin protein genes, causing peripheral neuropathies.
Neurotrophins and Neuronal Growth
- Nerve Growth Factor (NGF) is crucial for the growth and maintenance of cholinergic neurons, suppressing apoptosis.
- Other neurotrophins include Brain-Derived Neurotrophic Factor (BDNF), Neurotrophin 3 (NT-3), and NT-4/5, each supporting various neuron types.
- BDNF can rapidly depolarize neurons, while NGF is important for skin nociceptive neurons.
Receptor Mechanisms
- Neurotrophins bind to high-affinity tyrosine kinase (Trk) receptors, initiating signaling in neurons.
- Low-affinity p75 receptor binds all neurotrophins; its activation without neurotrophins can lead to apoptosis.
Multiple Sclerosis Diagnosis and Treatment
- MS diagnosis is challenging, often requiring evidence of multiple episodes and MRI to visualize scarring/plaque.
- Common treatments include corticosteroids for inflammation, β-interferons to suppress immune response, and other immunomodulatory agents like glatiramer acetate and natalizumab.
- Emerging therapies include B cell-depleting therapies and oral medications like fingolimod.
Nerve Fiber Classification
- Nerve fibers are categorized into types A, B, and C based on axonal diameter and conduction velocity.
- Sensory afferent fibers have a numerical classification (Ia, Ib, II, III, IV), reflecting diverse functionalities and hypoxia sensitivity.
Transport Mechanisms
- Orthograde transport along axons requires dynein and kinesin, functioning at fast (400 mm/day) and slow (0.5–10 mm/day) rates.
- Retrograde transport moves at about 200 mm/day from nerve endings to cell bodies.
Glial Cells Functions
- There are two main glial types: microglia (scavengers) and macroglia (oligodendrocytes, Schwann cells, astrocytes).
- Astrocytes maintain ionic balance and neurotransmitter concentrations, supporting neuronal health.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Explore the fascinating dynamics of neuron refractory periods through this quiz. Learn about the absolute and relative refractory periods, including their significance during the spike potential. Test your understanding of how these phases impact neuronal responsiveness to stimulation.
