Neuroanatomy Exam 1 Study Guide PDF

Exam 1 Study Guide Introduction - Identify the planes of reference when presented with pictures of sections of the brain and spinal cord (i.e., sagittal, midsagittal, horizontal, coronal, transverse, cross-section) Sagittal: Divides the brain into left and right halves Midsagit...

Exam 1 Study Guide Introduction - Identify the planes of reference when presented with pictures of sections of the brain and spinal cord (i.e., sagittal, midsagittal, horizontal, coronal, transverse, cross-section) Sagittal: Divides the brain into left and right halves Midsagittal: A sagittal section right in the middle. Horizontal (Axial): Divides the brain into the superior (top) and inferior (bottom) parts. Coronal: Divides the brain into anterior (front) and posterior (back) parts/ Transverse (Cross-section): Often used in spinal cord imaging, cutting perpendicular to its long axis.  A. Horizontal B. Coronal C. Midsagittal - Define gray matter and white matter, including where in the nervous system these terms apply. Gray Matter: Contains neuron cell bodies, dendrites, and synapses. Found in the cerebral cortex, basal ganglia, and spinal cord dorsal/ventral horns. White Matter: Contains myelinated axons that conduct signals. Found in the inner brain, corpus callosum, and outer spinal cord. From Slide: Gray matter: Areas of CNS made up of mainly of neuron cell bodies White matter: Areas of the CNS made of myelinated axons - Describe what the terms "nucleus" and "ganglion" mean in the field of neuroanatomy, including where in the nervous system these terms apply. Nucleus: A collection of neuron cell bodies in the CNS (e.g., thalamic nuclei) Ganglion: A collection of neuron cell bodies in the PNS (e.g, dorsal root ganglia) - Define afferent and efferent pathway Afferent Pathway: Carries sensory information to the CNS (ascending) Efferent Pathway: Carries motor signals from the CNS to muscle/glans (descending) From slide: Sensory: Out/distal to proximal Motor: In/proximal to distal A. Admittance to the CNS - Define lesion. Explain how understanding the effect of a lesion contributes to diagnostic clinical reasoning Lesion: Any damaged area in the nervous in the nervous system (stroke, tumor, injury) Clinical importance: Identifying a lesions location helps diagnose neurological disorders based on functional loss From slide: Lesion: a area of damage or dysfunction. - Compare focal, multifocal, and diffuse lesions Focal: A single, localized area (e.g., stroke) Multifocal: Multiple distinct areas (e.g., multiple sclerosis) Diffuse: Widespread damage (e.g., traumatic brain injury) - Compare and contrast incidence with prevalence Incidence: The number of new cases over a period of time Prevalence: The number of cases at a specific time - Differentiate between speed of onset and pattern of progression in a neurologic disorder Speed of Onset: - Acute: Sudden (e.g., stroke) - Subacute: Develops over days/weeks (e.g., infection) - Chronic: Slow progression (e.g., Alzheimer's) - Stable: Symptoms remain constant - Progressive: Symptoms worsen over time - Relapsing-Remitting: Episodes of worsening followed by partial/full recovery Neuroimaging - Compare and contrast computed tomography (CT), magnetic resonance imagining (MRI), diffusion tensor imaging (DTI), positron emission tomography (PET), and functional magnetic resonance imaging (fMRI). CT Scan: Detects bleeding, fractures, and tumors quickly MRI: High-detail images of soft tissue (brain, spinal cord, tumors) DTI: Maps white matter tracts, useful in brain injury and stroke recovery PET Scan: Measures metabolic activity, used for detecting cancer and dementia fMRI: Measures brain activity base on blood flow, used in research From Slide: Computed Tomography (CT): Mechanism: X-rays Use: Acute Hemorrhage, abnormalities, or fractures of bone, calcified lesions, sinus disease. Time to complete scan: 5 Minutes Radiation exposure: Present Magnetic Resonance Imaging (MRI): Mechanism: Magnetic fields and radio waves detect hydrogen ions Use: Stroke, tumors, infection, multiple sclerosis Time to complete scan: 30-120 minutes Radiation exposure: None Diffusion Tension Imaging (DTI) Mechanism: Magnetic fields and radio waves detect water diffusion along axons Use: Detailed images of white matter tracts, surgical planning Time to complete scan: 30 minutes Radiation exposure: None Positron Emission Tomography (PET) Mechanism: Detects radioactive isotopes as they travel through blood Use: Measure blood flow, glucose metabolism, and oxygen consumption Time to complete scan: 30 minutes Radiation exposure: Present Functional Magnetic Resonance Imaging (fMRI) Mechanism: Measures changes in oxygenated blood flow Use: Detect neural activity in the brain by evaluating changes in blood flow Time to complete scan: 60 minutes Radiation exposure: None - Describe the orientations of axial, coronal, and sagittal images. Axial (horizontal): Top-down view Coronal (Frontal) : Front-to-back view Sagittal: Side view Neurons and Neuroglia - Identify and label on a diagram the main components of a neuron: - Cell body or soma: Contains the nucleus, processes information - Axon: Transmits electrical impulses - Dendrite: Receive signals from other neurons - Pre-synaptic terminal: Releases neurotransmitters - Pre-synaptic neuron: The neuron sending the signal - Synaptic vesicles: stores neurotransmitters - Post-synaptic neuron: The neuron receiving the signal - Neurotransmitter receptors on cell membrane: Bind neurotransmitters on the post-synaptic membrane - Describe anterograde and retrograde axoplasmic transport.  Anterograde Transport: Moves materials from the cell body to the axon (e.g., neurotransmitters) Retrograde Transport: Moves materials back to the cell body for recycling From Slide: Axoplasmic Transport: Mechanism of transporting neurotransmitters and other substances from the soma to the presynaptic terminal Anterograde: From soma toward the presynaptic terminal Retrograde: From synapse back to the soma - Define and provide examples of unipolar, bipolar, pseudounipolar, and multipolar neurons. Unipolar: One extension (e.g., sensory neurons) Bipolar: Two extensions (e.g., retina neurons) Pseudounipolar: One extension splits into two (e.g., dorsal root ganglia) Multipolar : Many extension (e.g., motor neurons) - Name and briefly describe the four types of glial cells, and explain the main functions of each: - Astrocytes: Maintain blood-brain barrier, support neurons - Microglia: Act as the immune system of the CNS - Oligodendrocytes: Provide myelin for CNS neurons - Ependyma: Produce cerebrospinal fluid (CSF) - Schwann cells: Provide myelin for PNS neurons From Slide: Astrocytes: - When stimulated, propagate CA2+ waves - Signal to neurons through glutamate release - Transport nutrients from capillaries to neurons - Contribute to blood brain barrier Microglia - Phagocytic Oligodendrocytes - Provide myelination of CNS axons Ependyma - Cuboidal or columnar ciliated epithelial cells - Supports the CSF and lines surfaces - Describe how myelin generally influences nerve conduction.  Function: Myelin insulates axons, speeding up signal transmission viva saltatory conduction at the Nodes of Ranvier. From Slide: - Mostly lipid sheath around the axon - Insulates nerve fibers -- Increases speed of nerve impulse - Not a continuous structure - Small gaps, Nodes of Ranvier approximately every 1-2 millimeter - Identify the Node of Ranvier on a diagram and explain its function. The Nodes of Ranvier are small gaps in myelin where action potentials "jump," increasing conduction speed. - Identify diseases that affect myelin Multiple sclerosis (MS): Autoimmune attack on CNS myelin Guillain-Barre Syndrome: Autoimmune attack on PNS myelin Synapse - Explain the difference between modality-gated, voltage-gated, and ligand-gated ion channels. Modality-Gated: Opens due to stimuli like touch Voltage-Gated: Opens due to electrical changes Ligand-Gated: Opens when a neurotransmitter binds - Explain the events of the action potential, including: - distribution of Na+ and K+ ions during the action potential At rest, a neuron has a resting membrane potential of -70mV, meaning the inside of the neuron is more negative compared to the outside. This is maintained by sodium-potassium pump (Na+/K+ pump) and leak channels. Ion Distribution at Rest: Na+ (Sodium): More concentrated outside the neuron. K+ (Potassium): More concentrated inside the neuron. - opening and closing of voltage gated channels, and when these occur The action potential occurs in the three main phases: 1. Depolarization (Neuron "fires") - A stimulus (such as a signal from another neuron) causes voltage-gated Na+ channels to open. - Na+ rushes into the neuron, making the inside more positive - When the membrane reaches around +30mV, Na+ channels close. 2. Repolarization (Neuron "Resets") - Voltage-gated K+ channels open, allowing K+ to leave the neuron - This restores the negative charge inside the neuron - Membrane potential drops back toward resting levels (-70mV) 3. Hyperpolarization (Extra Reset) - Sometimes, too much K+ leaves, making the membrane even more negative than -70mV - This is called hyperpolarization - The sodium-potassium pump (Na+/K+ pump) helps return the neuron to its resting state. - refractory periods (absolute vs relative refractory period) After an action potential, the neuron needs time to "reset" before firing again. Absolute Refectory Period (Neuron cannot fire) : No action potential can start Why: Because Na+ channels are inactivated and need time to rest Basically: Neuron is busy and can't fire again Relative Refractory Period (Neuron can fire, but needs a stronger stimulus): A new action potential can happen, but only with a stronger-than-normal stimulus Why: Because the neuron is still slightly hyperpolarized (extra negative) Basically: Neuron is "recovering" -- can fire if the stimulus is extra strong - all or none property of action potential - An action potential either happens completely or not at all. - If the stimulus is strong enough to reach the threshold (-55mV), the neuron will always fire - A stronger stimulus does not make the action potential stronger, it only makes neurons fire more frequently - speed of conduction affected by diameter and myelination of axon The speed at which an action potential travels depends on two key factors: 1. Axon Diameter (Wider = Faster) - Larger diameter = less resistance = faster conduction - Smaller diameter = more resistance = slower conduction 2. Myelination (Insulation = Faster Signals) - Myelin (fatty covering) insulates the axon, preventing signal loss - The action potential "jumps" from one Node of Ranvier to another - This process is called saltatory conduction, which is much faster than unmyelinated conduction - Define, explain, and label diagrams related to the following terms: - EPSP: Increases the chance of an action potential - IPSP: Decreases the chance of an action potential - Temporal summation: Multiple signals over time increase the effect - Spatial summation: Multiple signals from different neurons combine. Development - Name the embryonic cell layer that gives rise to the nervous system. Ectoderm - Identify and name the first three regions/enlargements of the developing embryonic brain. Forebrain, Midbrain, Hindbrain - Identify and name the five regions/enlargements of the developing embryonic brain that emerge from the first three regions. Telencephalon, Diencephalon, Mesencephalon, Metencephalon, Myelencephalon - Identify the adult derivatives of the five regions of the developing brain.  - Name and describe two neural tube defects. Spina Bifida: Incomplete spinal cord formation Anencephaly: Missing parts of the brain. Neuroplasticity - Define neuroplasticity and give examples. Neuroplasticity: The brain's ability to reorganize itself Examples: Learning a new skill strengthens brain connection From slide: Neuroplasticity: The ability of neurons to change their function, chemical profile (amount and types of neurotransmitters produced) , and/or structure General term used to encompass the following mechanisms: - Habituation - Experience-dependent plasticity : learning and memory - Cellular recovery after injury - Describe two types of experience-dependent plasticity associated with learning and memory. Experience-dependent plasticity is the brains ability to change in response to learning and experience. Two major types related to learning and memory are: 1. Long-Term Potential (LTP) Strengthening Connections - Definition: When a neuron is repeatedly activated, the connection between it and the receiving neuron becomes stronger. - Mechanism: More neurotransmitters are released More receptors are added to the post synaptic neuron Synapses become more efficient Example: Learning a new skill, like playing an instrument or studying for an exam, strengthens synaptic connections Basically: Use it = Strengthens it / More Practice = Stronger Neural Pathways 2. Long-Term Depression (LTD) Weakening Connections - Definition: When a neuron is NOT used frequently, the connection weakens over time. - Mechanism: Less neurotransmitters release Fewer receptors on the post-synaptic neuron The synapse weakens or is removed Example: Forgetting a language you haven't spoken in years Basically: Use it or lose it /Neurons that aren't active weaken over time - Describe the degenerative and regenerative events of axonal injury in the peripheral nervous system (PNS). When an axon is damaged in the PNS, it can regenerate, but first, it goes through degeneration. Degenerative Events (After injury) 1. Axon Damage Occurs: The neuron's axon is cut or crushed 2. Wallerian Degeneration: The distal part of the axon (farthest from the cell body) breaks down and is cleared by Schwann cells and macrophages. 3. Chromatolysis: The cell body swells, and the nucleus moves periphery as the neuron starts to repair processes. Basically: Old axon parts die and get cleaned up Regenerative Events (Repair & Regrowth) 1. Schwann Cells Proliferate: They form a generation tube to guide axonal growth. 2. Axon Sprouting: The neuron sends out small axon branches to find the correct path. 3. Successful Regeneration: If the axon finds the Schwann cell pathway, it can reconnect and regain function. Basically: New axon grows if it finds the right path - Compare and contrast central and peripheral nervous system recovery following injury. A screenshot of a medical survey Description automatically generated Basically: CNS damage = Permanent (brain/spinal cord injuries) PNS damage = Can recover (nerve injuries in arms/legs) - Describe excitotoxicity. - Definition: A process where neurons are damaged or killed by excessive stimulation from neurotransmitters, especially glutamate. - Mechanism: 1. Excessive Glutamate Release Over excites neurons 2. Too much Calcium (Ca2+) Enters the Neuron Triggers harmful enzyme activity 3. Neuronal Damage or Death Leads to conditions like stroke, traumatic brain injury (TBI) and neurodegenerative diseases Example Conditions Linked to Excitotoxicity: - Stoke: Lack of oxygen causes excess glutamate release Brain Damage - Alzheimer's & Parkinson's: Ongoing excitotoxic damage contributes to cell death - Traumatic Brain Injury (TBI): Neurons are overstimulated after injury, worsening brain damage.