Week 1: Overview of nervous system: development, adult structures and ventricles Flashcards
(13 cards)
Describe the basic events involved in embryological development of the CNS
- week 4: formation of neural crest and tube
- neural tube develops into spinal cord, brain, and brain stem
- day 25: 3 vesicle stage- tube has three dilations, the forebrain (prosencephalon), midbrain (mesencephalon), hindbrain (rhombencephalon)
- 5 weeks: 5 vesicle stage.
forebrain: telencephalon and diencephalon
midbrain: Mesencephalon
hindbrain: metencephalon and myelencephalon
List the major components of the adult CNS and its subdivisions
- cortex, brain stem, and spinal cord
- transition between brain stem and spinal cord is at foramen magnum (through which you can have tonsilar herniation due to intracranial pressure increases)
Explain the production the CSF
- formed by choroid plexus: pial connective tissue and capillaries
- in body, inferior horn, and atrium (glomus) of lateral ventricles
- in roof of 3rd and 4th ventricles
- 500mL/day, only 150mL capacity in ventricles and subarachnoid (3x turnover/day)
Know the sites of occlusion along the CSF pathways that can lead to hydrocephalus
- obstructions within ventricular system
- turmor of choroid plexus can occlude 3rd ventricle , cause stenosis of aqueduct
- results in ventricle enlargement proximal to obstruction - obstructions in subarachnoid space impairing CSF absorption
- tumor causes lateral shift of brain due to unilateral mass (post infectious or post hemorrhagic meningitis)
List the adult derivatives of the CNS from the 5 vesicle stage
- Telencephalon: cerebral cortex and basal ganglia
- Diencephalon: retina, Thalamus, hypothalamus, subthalamus
- Mesencephalon: midbrain, sup and inf collicullus
- Metencephalon: Pons and cerebellum
- Myelencephalon: medulla
What are the subdivisions of the diencephalon?
- Thalamus: relays sensory info from PNS to cortex. Integrates motor fxns of cortex with cerebellum and basal ganglia
- hypothalamus: regulating homeostasis
- Subthalamus: motor control
- epithalamus (pineal gland): circadian rhythms
What are the subdivisions of the brain stem?
- midbrain
- pons
- medulla oblongata
What is the cerebellum for and what are its subdivisions?
- coordinates motor activity and involved in motor learning
- divided into two hemispheres and a midline vermis
How does the ventricular system develop?
- at around 5 weeks
- telencephalon expands, lateral ventricles enlarge with it
- third ventricle forms from central cavity of diencephalon and cerebral aqueduct from lumen of mesencephalon
- 4th ventricle from shape change in floor of met encephalon and myelencephalon to form diamond like depression
Describe the ventricular system.
Lateral ventricles
-divided into anterior, body, posterior, and inferior horn
-lateral ventricles communicate with third ventricle through inter ventricular foramen
Third ventricle:
-extends into optic chasm, infundibulum, pineal body-called recesses
cerebral aqueduct
-connects 3rd and 4th ventricles
fourth ventricle:
-between cerebellum and pons, upper medulla ventrally
-communicates with subarachnoid space through 3 openings
Explain the flow of CSF
lateral ventricle–>3rd ventricle–>cerebral aqueduct–>4th ventricle–>median and lateral apertures–>subarachnoid space around brain and spinal cord
Explain the drainage of CSf
-CSF flows in upward direction form base of brain toward superior sagittal sinus. Absorbed via arachnoid granulations into cerebral venous sinuses
Explain the functions of CSF
- prevent injury
- blood-CSF barrier by epyndemal cells in chord plexus
- transports micronutrients, e.g. vitamins, trace elements to brain
- remove products of metabolism of some neurotransmitters
