Neuroscience Quiz: Brain Structures and Functions

Central Nervous System (CNS) Anatomy and Function

• CNS comprises the brain, spinal cord, and cranial nerves 1 & 2. Major regions include the spinal cord, brainstem, cerebellum, and cerebrum.
• Circle of Willis: A network of arteries supplying blood to the cerebral hemispheres.
  • Anterior Cerebral Artery (ACA): Branches supply the medial surface of frontal and parietal lobes.
  • Middle Cerebral Artery (MCA): Supplies internal capsule, globus pallidus, putamen, caudate, and most of the lateral hemispheres.
  • Posterior Cerebral Artery (PCA): Supplies midbrain, occipital lobe, and parts of medial and inferior temporal lobe.
• Brain Lobes and Functions:
  • Frontal Lobe: Motor functions, executive functions, planning, and personality.
  • Parietal Lobe: Sensation processing.
  • Temporal Lobe: Language and hearing.
  • Occipital Lobe: Vision.
• Brainstem Functions: Vital functions, cardiovascular activity, respiration, conveying information from cerebrum and spinal cord, cranial nerve nuclei, and consciousness.
• Brain Structure and Sulci/Gyri:
  • Deep Longitudinal Fissure: Separates right and left hemispheres.
  • Central Sulcus: Separates precentral and postcentral gyri, both part of the frontal lobe.
  • Parieto-occipital Sulcus: Separates parietal and occipital lobes.
• Communication Between Brain Areas: Presynaptic neuron transmits information to the postsynaptic neuron via action potentials (nerve impulses).
• Cerebellum Function and Sensory Input:
  • Motor and nonmotor domains.
  • Comparator function (coordination, regulation, and modulation of motor behavior).
  • Sensory function: Unconscious proprioception, regulating balance and coordination of movement, quality control of movement.
  • Sensory loss with injury is ipsilateral for cerebellum.
  • Sensory losses include proprioception, light touch, fast nociception, heat, and slow nociception.
• Demyelination: Affects proprioception and vibratory sense (most heavily myelinated).
• Nerve Root Lesion: Impaired sensation in dermatomal pattern and loss of motor function in myotomal pattern.
• Complete Transection: All sensation lost 1-2 levels below lesion level.
• Hemi-section/Brown-Sequard Syndrome:
  • Pain and temperature interrupted below lesion contralaterally.
  • Pain and temperature interrupted at lesion ipsilaterally.
  • Discriminative touch and conscious proprioception lost below lesion ipsilaterally.
• Posterior Column Lesions: Loss of conscious proprioception, vibration, and 2-point discrimination below lesion level.
• Anterior Cord Lesion: Loss of pain, temperature, and crude touch below lesion level.
• Brainstem Lesions: Contralateral or ipsilateral signs, depending on lesion location.
• Thalamus Lesion: Contralateral decrease or loss of sensation.
• Somatosensory Cortex: Contralateral impairments; discriminative sensations include stereognosis, conscious proprioception, 2-point discrimination, localization of touch, and fast nociception.
• Spinal Cord Anatomy: Extends from foramen magnum to L1 vertebra (ends at conus medullaris). Blood supply via 3 spinal arteries: 1 anterior (⅔), 2 posterior (⅓). Dorsal (sensory) and ventral (motor) roots join to form nerve roots.
• Imaging Techniques:
  • PET: Shows metabolic functions, blood flow (radioactive material).
  • CT: Detailed images of bones/fractures (X-rays).
  • MRI: Shows soft tissue detail (magnetic field).
  • MRA: Visualizes blood vessels in detail (contrast medium).
  • BOLD MRI: Detects areas of oxygen consumption; assesses brain function.
  • DTI: Detailed white matter tract imaging; detects ischemic stroke (water diffusion).
  • EEG: Records electrical impulses from brain cortex; detects seizures.

Sensory Receptors and Functions

• Exteroreceptors: Respond to external environment.
• Interoreceptors: Respond to internal environment.
• Proprioceptors: Internal sense of movement; joint position sense.
• Tonic Receptors: Slowly adapting receptors.
• Phasic Receptors: Fast adapting receptors.
• Mechanoreceptors: Respond to mechanical deformation.
• Thermoreceptors: Respond to temperature gradients across the skin.
• Nociceptors: Respond to tissue-damaging stimuli.
• Chemoreceptors: Respond to chemical constituents.

Dorsal Column-Medial Lemniscus (DCML) Pathway

• Discriminative tactile sensation, kinesthesia/proprioception and stereognosis.
• Heavily myelinated.
• Three-neuron pathway:
  • First order: Enters dorsal column, ascends ipsilaterally to medulla; cell body in DRG.
  • Second order: Crosses, travels to contralateral dorsal column nuclei, ascends to thalamus; cell body in medulla.
  • Third order: Thalamus to parietal lobe; cell body in thalamus.
• Carries discriminative touch, conscious proprioception, and vibration.

Spinothalamic Tract

• Part of the anterolateral system; for nociception, temperature, and crude touch.
• Lightly myelinated.
• Three-neuron pathway:
  • First order: Enters spinal cord, synapses in dorsal horn; cell body in DRG.
  • Second order: Crosses midline, ascends in anterolateral white matter to thalamus; cell body in dorsal horn.
  • Third order: Thalamus to parietal lobe; cell body in thalamus.
• Carries nociception (fast), temperature, and crude touch.

Nerve Structure and Function

• Neurons: Nerve cells; receive and transmit signals; responsible for control, integration, and responses of body functions.
• Parts: Axon (conducting), dendrites (receptive), soma (cell body).
• Neuroglia: Supporting cells; protect and supply metabolic support to neurons.
• Information Transmission: Axons (nerve fibers) forming bundles (tracts/pathways).

Nerve Damage

• Description of damage effects not provided.

CNS Development

• Zygote: Fertilized egg; divides into cells.
• Morula: Collection of blastomeres (cells).
• Blastocyst: Spheres of cells; outer layer becomes placenta, inner layer embryo.
• Embryo: Until 8 weeks; Fetus: After 8 weeks.
• Gastrulation: Single-layered blastula reorganized into trilaminar gastrula (ectoderm, mesoderm, endoderm).
• Neurulation: Formation of neural tube (3rd week gestation).
• Neural Plate: Thickening of ectoderm.
• Neural Tube: Forms CNS.
• Neurocele: Forms ventricles and spinal cord.
• Neural Crest: Forms PNS.
• Somite Development: Develop from mesoderm (day 20-30).
• Myotome: Embryonic part of somite that becomes muscle.
• Dermatome: Embryonic part of somite that becomes dermis.
• Brain Formation (primary vesicles): 4 weeks.
  • Prosencephalon (forebrain), Mesencephalon (midbrain), Rhombencephalon (hindbrain).
• Brain Formation (secondary vesicles): 5 weeks.
  • Telencephalon → cerebral hemispheres (lateral ventricles)
  • Diencephalon → thalamus, hypothalamus, optic vesicles
  • Mesencephalon → midbrain
  • Rhombencephalon → cerebellum, pons, medulla
• Fetal Stage (8 weeks-birth): More nervous system development, myelination begins.
• Cellular Development: Proliferation, migration, differentiation (growth cones, synaptogenesis).
• Myelination: Begins 4th month, most sheaths complete by 3 years.
• Clinical Conditions: Descriptions and causes of anencephaly, spina bifida, cerebral palsy, autism spectrum disorders, Horner's syndrome, fibromyalgia, complex regional pain syndrome, listed.

Neurotransmitters

• General descriptions of neurotransmitters (e.g., acetylcholine, norepinephrine, dopamine, GABA).

Neurological Plasticity

• Neural plasticity: Ability of NS to change functions, chemical profiles, or structure.
  • Recovery vs. compensation.
• Experience-expectant plasticity: Changes during development.
• Experience-dependent plasticity: Cellular structure changes.
• Critical periods: Specific times for development.
• Treatments: Examples of treatment approaches.

Autonomic Nervous System (ANS)

• SNS: Increase energy utilization; fight-or-flight (stress, exercise).
  • Efferent pathway, innervates adrenal medulla, vasculature, etc.
  • Paravertebral ganglia, short preganglionic, long postganglionic fibers; uses ACh (pre) & EPI/NE/ACh (post).
• PSNS: Most active at rest; energy conservation, increases digestion, promotes relaxation.
  • Efferent pathway, PS fibers innervate pupil, salivary glands, etc.
  • Long preganglionic, short postganglionic fibers, ganglia near/in organ.
  • Uses ACh for both pre and post.
• SNS vs PSNS: Comparison table of functions.

Pain

• Nociceptors: Signal injury.
• Referred pain: Perceived as coming from different origin due to shared secondary neuron in spinal cord; thalamus.
• Spinothalamic tract mediates pain.
• Antinociception: Suppression of pain.