Central Nervous System Flashcards
Brain arises from…
Rostral part of the neural tube
3 week PRIMARY brain vesicles in 4 week old embryo
Prosencephalon (forebrain)
Mesencephalon (midbrain)
Rhombencephalon (hindbrain)
What secondary vesicles do the primary ones give rise to?
Prosencephalon divides into the telencephalon and diencephalon
Mesencephalon remains undivided
Rhombencephalon divides into metencephalon and myelencephalon
How does the adult brain develop from the secondary brain vesicles
Telencephalon gives the cerebral hemispheres
Diencephalon becomes thalamus, hypothalamus, and epithalamus
Metencephalon becomes pons and cerebellum
Myelencephalon becomes medulla oblongata
Ventricles of the brain
Expansions of the brain's central cavity Filled with cerebral spinal fluid Lined with ependymal cells Continuous with each other Continuous with the central canal of the spinal cord
Location of the ventricles:
- Lateral ventricles
- Third ventricle
- Cerebral aqueduct
- Fourth ventricle
- Located in cerebral hemispheres. Horseshoe shaped from bending of the cerebral hemispheres
- Lies in diencephalon. Connected with lateral ventricles by interventricular foramen
- Connects 3rd and 4th ventricles
- Lies in hindbrain. Connects to the central canal of the spinal cord
4 regions of the brain
Brainstem (midbrain, pons, medulla)
Cerebellum
Diencephalon
Cerebral hemispheres
2 main fissures
- Transverse fissures (separates cerebrum and cerebellum)
2. Longitudinal fissure (separates cerebral hemispheres)
Sulci vs Gyri
Sulci are grooves
Gyri are ridges
What does the central sulcus divide? What are the 2 gyri it is bordered by called?
Divides the frontal and parietal lobes
Bordered by precentral gyrus and postcentral gyrus
3 general kinds of functional areas
Sensory areas
Association areas
Motor areas
Multimodal association areas
Receive and integrate input from multiple regions of the cerebral cortex
Higher level functions
Ex: you feel a key in your pocket, these areas tell you what keys are
Motor cortex
Plans and initiates voluntary motor functions
Broca’s area
Left frontal lobe
Can understand everything and can say words, but cannot put words in a sentence that makes sense
Wernicke’s area
Left temporal lobe
Cannot understand words, but can speak and hear completely fine
Cannot make sense of a sentence
Primary somatosensory cortex
Projection is contralateral
Cerebral hemispheres receive input from the opposite side of the body
Primary motor cortex
Specific pyramidal cells control specific areas of the body
Face and hand muscles are controlled by many pyramidal cells
Somatotopy
Body is represented spatially in the primary motor cortex
Which sides of the central sulcus are the motor vs sensory cortex
Motor map in precentral gyrus
Sensory map in postcentral gyrus
3 types of tracts
Commissures
Association fibers
Projection tracts
Commissures
Composed of commissural fibers
Allows communication between cerebral hemispheres
Corpus callosum is the largest commissure
Association fibers
Connect different parts of the same hemisphere
Parts of Wernicke’s and Broca’s areas are connected by these fibers
Projection tracts (2)
From the cortex to the rest of the NS
Internal capsule: projection fibers form a compact bundle - passes between thalamus and basal nuclei
Corona radiata: superior to the internal capsule - fibers run to and from the cerebral cortex
Basal nuclei/ganglia
A group of nuclei deep within the cerebral white matter
Formed from caudate nucleus, putamen, globus pallidus
Involved in motor control
Receives input from many cortical areas
Substantia nigra also influences it
3 functions of basal ganglia
Start, stop and regulate intensity of voluntary movements
Select appropriate muscles for a task and inhibit others
Estimate the passage of time
Thalamus
80% of the diencephalon
Contains ~ 12 major nuclei
Acts as a relay station for incoming sensory message
Every part of brain communicating with cerebral cortex relays signals through thalamic nuclei!
Nuclei organize and amplify or tone down signals
What type of information does the: 1. Ventral posterolateral nuclei 2. Medial geniculate body 3. Lateral geniculate body receive?
- Act as relay stations for the sensory information ascending to the primary sensory areas of the cerebral cortex
- Receives auditory input and links to the auditory cortex
- Receives visual input and transmits to the visual cortex
Epithalamus
Forms part of the roof of the third ventricle
Consists of a tiny group of nuclei
Includes the pineal gland
Pineal gland
Secretes melatonin
Under influence of hypothalamus
Aids in control of circadian rhythm
Cerebral aqueduct
Central cavity of the midbrain
Cerebral peduncles
Located on the ventral surface of the brain Contain pyramidal (corticospinal) tracts
Corpora quadrigemina
On dorsal side of midbrain
Act in visual and auditory reflexes
Largest nuclei
Divided into superior and inferior colliculi
Superior vs inferior colliculi
Superior: nuclei that act in visual reflexes
Inferior: nuclei that act in reflexive response to sound
Periaqueductal gray matter (location, 2 functions)
Surrounds the cerebral aqueduct
Involved in fight or flight reaction, mediates response to visceral pain
Function of:
- Medial lemniscus
- Reticular formation
- Crus cerebri of cerebral peduncle
- Project from neurons in medulla to thalamus - carries sensory information
- Collection of nuclei - has functions in posture, movement, arousal, etc
- Where the pyramidal tracts descend down through your body
Pontine nuclei
Connect portions of the cerebral cortex and cerebellum
Send axons to cerebellum through the middle cerebellar peduncles
Folia
Ridges of the cerebellum
3 lobes of the cerebellar hemispheres
Anterior
Posterior
Flocculonodular lobe (tiny)
3 regions of the cerebellum
Cortex (gray)
Arbor vitae (internal white matter)
Deep cerebellar nuclei - deeply situated gray matter
3 tracts connecting the cerebellum to the brainstem
Superior cerebellar peduncles: to midbrain
Middle cerebellar peduncles: to pons
Inferior cerebellar penduncles: medulla
3 types of info the cerebellum receives to coordinate body movements
Info on equilibrium
Info on current movements of limbs, neck, and trunk
Info from cerebral cortex
2 layers of the dura
Periosteal layer (connects to the skull) Meningeal layer (connected to periosteum) Fused except to enclose the dural sinuses
Arachnoid Mater
Located beneath the dura
Arachnoid villi are where CSF can move back into the blood stream
Allows CSF to pass into the dural blood sinuses
Pia Mater
Delicate connective tissue
Clings tightly to the surface of the brain
