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Questions and Answers
What are the two main branches of the internal carotid arteries supplying the brain?
What are the two main branches of the internal carotid arteries supplying the brain?
Which layer of the meninges is characterized as tough and double-layered?
Which layer of the meninges is characterized as tough and double-layered?
What structure forms as a result of the fusion of the vertebral arteries?
What structure forms as a result of the fusion of the vertebral arteries?
Which defect is characterized by the failure of closure of the anterior neuropore?
Which defect is characterized by the failure of closure of the anterior neuropore?
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What is the primary derivative of the neuroectoderm?
What is the primary derivative of the neuroectoderm?
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Which part of the neural tube ultimately becomes the spinal cord?
Which part of the neural tube ultimately becomes the spinal cord?
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What is a characteristic feature of the falx cerebri?
What is a characteristic feature of the falx cerebri?
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Which of the following conditions is related to incomplete closing of the vertebrae?
Which of the following conditions is related to incomplete closing of the vertebrae?
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What is the primary function of the neurons developed within the alar plate of the neural tube?
What is the primary function of the neurons developed within the alar plate of the neural tube?
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Which structure develops from the caudal portion of the neural tube?
Which structure develops from the caudal portion of the neural tube?
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By which week of embryonic development is the formation of the neural tube typically completed?
By which week of embryonic development is the formation of the neural tube typically completed?
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What does the sulcus limitans differentiate within the developing spinal cord?
What does the sulcus limitans differentiate within the developing spinal cord?
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The prosencephalon is more commonly referred to as which part of the brain?
The prosencephalon is more commonly referred to as which part of the brain?
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Which structure does NOT arise from the neural crests during development?
Which structure does NOT arise from the neural crests during development?
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What are the general visceral efferent neurons primarily involved with?
What are the general visceral efferent neurons primarily involved with?
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Which brain structure forms from the division of the rhombencephalon?
Which brain structure forms from the division of the rhombencephalon?
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What is the primary role of sensory ganglia formed from neural crests?
What is the primary role of sensory ganglia formed from neural crests?
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Which of the following flexures is associated with the junction of the midbrain and forebrain?
Which of the following flexures is associated with the junction of the midbrain and forebrain?
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Which type of efferent neuron is responsible for controlling muscles derived from branchial arches?
Which type of efferent neuron is responsible for controlling muscles derived from branchial arches?
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What major change occurs during the development of the neural tube into the adult central nervous system (CNS)?
What major change occurs during the development of the neural tube into the adult central nervous system (CNS)?
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What major structure is formed by the inner cavity of the neural tube after development?
What major structure is formed by the inner cavity of the neural tube after development?
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What is the primary developmental anomaly associated with anencephaly?
What is the primary developmental anomaly associated with anencephaly?
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In spina bifida, what may be exposed on the infant's back?
In spina bifida, what may be exposed on the infant's back?
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During the embryonic development of the brain, how is the central cavity affected?
During the embryonic development of the brain, how is the central cavity affected?
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What is the term used to describe the evolution of the cerebral hemispheres to an 'executive' role in brain function?
What is the term used to describe the evolution of the cerebral hemispheres to an 'executive' role in brain function?
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Which part of the brain underwent relatively little further development during evolution, according to the content provided?
Which part of the brain underwent relatively little further development during evolution, according to the content provided?
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What structure serves to separate the cerebral hemispheres in the cranial cavity?
What structure serves to separate the cerebral hemispheres in the cranial cavity?
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Which layer of meninges is the outermost membrane surrounding the CNS?
Which layer of meninges is the outermost membrane surrounding the CNS?
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What is the significance of the dural reflections in the cranial cavity?
What is the significance of the dural reflections in the cranial cavity?
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What does the rostral end of the tubular nervous system predominantly develop into during evolutionary changes?
What does the rostral end of the tubular nervous system predominantly develop into during evolutionary changes?
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Which function is primarily associated with the cerebellum in the human brain?
Which function is primarily associated with the cerebellum in the human brain?
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What is suggested about the relation of the human brain to its evolutionary ancestors?
What is suggested about the relation of the human brain to its evolutionary ancestors?
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What evolves as a major integrative center in association with the senses and movement control during brain evolution?
What evolves as a major integrative center in association with the senses and movement control during brain evolution?
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Which of the following statements regarding the coverings of the central nervous system is true?
Which of the following statements regarding the coverings of the central nervous system is true?
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What structure does the basal plate specifically develop into during spinal cord formation?
What structure does the basal plate specifically develop into during spinal cord formation?
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Which of the following best describes the characteristics of multipolar neuroblasts?
Which of the following best describes the characteristics of multipolar neuroblasts?
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Which cell type myelinates in the central nervous system (CNS)?
Which cell type myelinates in the central nervous system (CNS)?
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What does the sulcus limitans demarcate in the neural tube?
What does the sulcus limitans demarcate in the neural tube?
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At which week of development does the optic nerve (CN II) begin to form?
At which week of development does the optic nerve (CN II) begin to form?
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Which of the following structures is NOT derived from the neural crest?
Which of the following structures is NOT derived from the neural crest?
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What is the primary function of ependymal cells?
What is the primary function of ependymal cells?
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What emerges from the neuroepithelial cells following the closure of the neural tube?
What emerges from the neuroepithelial cells following the closure of the neural tube?
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Which is NOT a secondary brain vesicle formed from the primary brain vesicles?
Which is NOT a secondary brain vesicle formed from the primary brain vesicles?
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Which cell type originates from the vascular mesenchyme in the CNS?
Which cell type originates from the vascular mesenchyme in the CNS?
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The roof plates in the neural tube are characterized by what feature?
The roof plates in the neural tube are characterized by what feature?
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How many pairs of cranial nerves arise primarily from the brainstem?
How many pairs of cranial nerves arise primarily from the brainstem?
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What is the main role of Schwann cells in the peripheral nervous system?
What is the main role of Schwann cells in the peripheral nervous system?
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Which of the following describes the alar plates in the neural tube?
Which of the following describes the alar plates in the neural tube?
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Study Notes
Brain Arterial Circulation
- Two major arteries supply each side of the brain: internal carotid arteries and vertebral arteries.
- Internal carotid arteries branch into anterior and middle cerebral arteries.
- Vertebral arteries merge to form the basilar artery, which further divides into posterior cerebral arteries.
Meninges
- Three membranes (meninges) surround the brain:
- Dura mater: A tough, double-layered membrane; the inner layer (meningeal) is next to the brain, the outer layer (periosteal) is attached to the skull.
- Arachnoid mater: A thin membrane with a subarachnoid space filled with cerebrospinal fluid (CSF).
- Pia mater: A very thin membrane adhering closely to the brain surface.
- Cranial dura encloses the brain, often inseparable in some areas. The two dura layers separate to create dural venous sinuses and dural partitions.
- Dural partitions, similar to septa, prevent excessive brain movement.
- Falx cerebri: A sickle-shaped dural partition separating the cerebral hemispheres.
Trilaminar Embryonic Disc
- Three germ layers (ectoderm, mesoderm, endoderm) compose the disc.
Neural Tube Formation
- Cranial and caudal ends of the neural tube are called the anterior and posterior neuropores, respectively.
- Developing cranial portion of tube becomes the brain, caudal portion becomes the spinal cord.
- Neural canal differentiates into the ventricular system of the brain and central canal of the spinal cord.
Neural Tube Defects
- Exencephaly: Anterior neuropore fails to close; brain develops outside the skull.
- Anencephaly: Absence of a significant portion of the brain.
- Microcephaly: Small brain within a small cranium.
- Spina bifida: Incomplete closure of the vertebrae and neural tube, allowing spinal cord or meninges to protrude. Common in lumboscaral region.
Neural Crest Cells
- Neural crest cells are located at the neural plate border.
- Closure of the neural tube separates them from the surface ectoderm.
- They migrate to a multitude of locations and differentiate into various tissues.
Derivatives of Ectoderm
- Neuroectoderm differentiates into:
- Neural tube: Forms CNS (brain and spinal cord).
- Neural crest: Forms facial & skull bones, cranial nerve ganglia, dorsal root ganglia, autonomic ganglia, meninges (pia & arachnoid), Schwann cells (PNS myelin), satellite cells (PNS glial cells).
- Surface ectoderm differentiates into:
- Skin epidermis, hair, nails, enamel.
- Anterior pituitary lobe.
Early Brain Development
- Three primary brain vesicles: prosencephalon (forebrain), mesencephalon (midbrain), rhombencephalon (hindbrain).
- Five secondary brain vesicles:
- Telencephalon: Cerebral cortex and basal ganglia.
- Diencephalon: Thalamus, hypothalamus, pituitary gland, pineal gland, optic nerve (CN II) and retina.
- Mesencephalon: Midbrain.
- Metencephalon: Pons and cerebellum.
- Myelencephalon: Medulla oblongata.
Cranial Nerves
- 12 pairs of cranial nerves; most arise from the brainstem. Example: Optic nerve (CN II).
Spinal Cord Development
- Neuroepithelial cells rapidly divide during neural groove stage.
- Neuroblasts form the mantle layer, precursor to grey matter.
- Marginal layer develops into white matter.
- Ventral thickening (basal plates) contain motor neurons.
- Dorsal thickening (alar plates) contain sensory neurons.
- Sulcus limitans separates basal and alar plates.
- Floor and roof plates allow fibre crossing.
- Intermediate horn (lateral horn) contains autonomic neurons (T1-L2/L3).
Histological Differentiation (Nerve Cells)
- Neuroblasts (primitive nerve cells) form from neuroepithelial cells.
- Differentiation includes apolar, bipolar, and multipolar stages.
- Axons from basal plate form ventral roots (impulses to muscles).
- Axons from alar plate form association neurons (interneurons).
Histological Differentiation (Glial Cells)
- Glial blasts develop from neuroepithelial cells alongside neuroblasts.
- Differentiation yields astrocytes (support, metabolism), oligodendrocytes (myelination), microglia (phagocytic cells).
- Ependymal cells line CNS cavities.
Myelination
- Schwann cells myelinate PNS axons (one axon per Schwann cell).
- Oligodendrocytes myelinate CNS axons (one cell can myelinate multiple axons.
Brainstem and Medulla
- Brainstem is a direct extension of the spinal cord.
- Medulla oblongata is involved with vital reflexes.
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Description
Explore the crucial structures that supply and protect the brain, including the major arteries like the internal carotid and vertebral arteries. Understand the roles of the meninges, including the dura mater, arachnoid mater, and pia mater, in maintaining brain stability and function.
