Development and External Features of the Brain Flashcards
1
Q
Gastrulation (week 3)
A
- Proliferation and migration of the epiblast to create the endoderm (first wave), mesoderm (second wave) and ectoderm (remainder)
- Brain and spinal cord from ectoderm
2
Q
Neurulation (week 4)
A
- Mesoderm condenses to form notochord, which induces the overlying ectoderm to become the neural plate
- Neural plate will give rise to CNS
- Neural plate forms groove in middle and folds in on itself to form neural tube (becomes brain and spinal cord)
- Cavity in center of tube represents the future ventricular system
- Neural crest cells (multipotent) are from the dorsal-most portion of the neural folds and migrate away to become a variety of structures
3
Q
Development of brain and brain stem: 3 vesicle stage
A
- The immature neural tube becomes segmented into the 3 vesicle stage: forebrain (prosencephalon), midbrain (mesencephalon), and hindbrain (rhombencephalon)
- The spinal cord is the remaining portion of the neural tube
4
Q
Development of brain and brain stem: 5 vesicle stage
A
- At 5 weeks the neural tube becomes segmented into 5 parts (not including spinal cord)
- Forebrain becomes the telencephalon and diencephalon
- Mesencephalon is unchanged
- Hindbrain becomes the metencephalon and myelencephalon
- In the fully developed brain, the brain stem and spinal cord division is at the foramen magnum
5
Q
Details of the 5 vesicle stage
A
- Telencephalon contains both cerebral hemispheres and the lateral ventricles. Becomes the cerebral cortex and basal ganglia
- The diencephalon contains the optic vesicle and third ventricle. Becomes the retina, thalamus, hypothalamus, and subthalamus
- The mesencephalon contains the cerebral aqueduct. Becomes the midbrain, superior and inferior collicullus
- The metencephalon and myelecephalon both contain the fourth ventricle
- Metencephalon becomes the pons and cerebellum
- Myelencephalon becomes the medulla
6
Q
Surface anatomy of cerebral cortex
A
- Frontal cortex and parietal cortex separated by central sulcus
- Immediately anterior to the central sulcus is the precentral gyrus (part of frontal cortex), which is the primary motor cortex
- Immediately posterior to the central sulcus is the postcentral gyrus (part of parietal cortex), which is the primary sensory cortex
- Frontal cortex responsible for motor, judgement, abstract reasoning, and socially appropriate behavior
- Parietal cortex responsible for sensory integration
- Occipital cortex houses the visual cortex
- Temporal cortex associated w/ learning, memory, and emotion
7
Q
Sulci separating the lobes
A
- Longitudinal fissure separates the L from the R side of the parietal, frontal, and occipital lobes
- Central sulcus separates the frontal and parietal lobes
- Lateral (horizontal) fissures separate the temporal lobe from the frontal and parietal lobes
- Parieto-occipital sulcus separates the occipital lobe from the parietal and temporal lobes
8
Q
Diencephalon
A
- Located btwn the cortex and brain stem, divided into 4 parts
- Thalamus: relays sensory info from PNS to cortex, integrates motor function of cortex w/ cerebellum and basal ganglia
- Hypothalamus: major role in regulating homeostasis
- Subthalamus: involved in motor control
- Epithalamus (pineal gland): circadian rhythms (melatonin)
9
Q
Brain stem
A
- Composed of the midbrain, pons, and medulla
- Contains cranial nerve nuclei, ascending sensory tracts, descending motor tracts, and the reticular formation (RF, keeps us awake)
10
Q
Cerebellum
A
- Coordinates motor activity and is involved in motor learning
- Made up of 2 hemispheres and a midline vermis
- Separated from cortex by the tentorium
- Most inferior part is the tonsil, can become herniated w/ increased inter cranial pressure and compress part of the brainstem
11
Q
LVs
A
- Cavity contained w/in each hemisphere is the lateral ventricle (LV)
- LV is continuous w/ the 3rd ventricle (in diencephalon) and the cerebral aqueduct/4th ventricle (in the brainstem)
- LV is divided into anterior horn (frontal lobe), body (parietal lobe), posterior horn (occipital lobe), and inferior horn (temporal lobe)
- Both LVs communicate w/ the single midline 3rd ventricle through the interventricular foramen (IVF, monro)
- Choroid plexus is present in body, atrium (near posterior horn), and inferior horn of LV
12
Q
3rd, 4th ventricles and cerebral aqueduct
A
- 3rd ventricle: slit-like cavity btwn the thalami and hypothalami of the two sides
- CSF in 3rd ventricles enters the 4th ventricle through the cerebral aqueduct
- 4th ventricle is anterior to cerebellum and posterior to brainstem
- From the 4th ventricle the CSF leaves into the subarachnoid space through 3 different openings (1 midline and 2 lateral apertures)
13
Q
Formation of the CSF
A
- CSF is an ultrafiltrate of plasma mostly formed by the choroid plexus (capillaries and pial connective tissue)
- Choroid plexus is found in every ventricle
- CSF made from choroid plexus involves passive diffusion and active secretion by choroid epithelial (ependymal) cells
- Flow of CSF: LV-> IVF-> 3rd V-> CA-> 4th V-> apertures-> subarachnoid space
- Drainage of CSF: in subarachnoid space CSF flows in an upward direction toward superior sagittal sinus (SSS), it is absorbed mostly by arachnoid granulations into cerebral venous sinuses
14
Q
Function of CSF
A
- Prevent injury
- Maintain microenvironment for CNS, due to Blood-CSF barrier (BCB), which is the product of ependymal cell tight junctions in the choroid plexus (choroid plexus capillaries are fenestrated)
- BBB is tight junctions of endothelial cells lining capillaries (everywhere but choroid plexus)
- CSF transports elements to and from the brain (vitamins, glucose, waste products)
15
Q
Hydrocephalus (water brain)
A
- Results from an obstruction to the flow of CSF
- Results in dilation of all ventricles and subarachnoid space proximal to the obstruction
- Obstruction can be in the ventricular system or in the subarachnoid space impairing CSF absorption
