Describing the Brain Flashcards
What is the process called by which the neural plate folds to form the neural tube?
Neurulation
Name the following parts of the neural plate:
What causes the neural plate to fold to develop the neural tube?
Neuroectoderm receives a signal from the notochord - this causes the cells to thicken and the lateral margins to fold inwards to form a neural tube.
What is primary neurulation?
When the lateral edges of the neural plate fold upwards & inwards, joining and fusing.
What is secondary neurulation?
Neural tube forming with the cavity in the centre
Why does the neural plate become a tube?
Because the cells in the middle increase, the plate becomes thicker and heavier here, causing it to move down whilst the plate margins move upwards.
When does neurulation occur?
In weeks 3-4
What does the neural tube become in the body?
The brain and spinal cord, the meninges and cranial bones.
How common are neural tube defects?
1 in 1000
What is Anencephaly?
Failure of the anterior neuropore to close.
What is spina bifida?
Failure of the posterior neural tube to close (creates open vertebral canal)
What are the two types of spinal bifida and what is the difference between them?
Spina bifida occulta (hidden, vertebral arch defect only)
Spina bifida cystica (meninges project out of the body)
How many primary brain vesicles are there?
3
How many secondary brain vesicles arise from the 3 primary brain vesicles?
5
What are the primary brain vesicles called?
Prosencephalon
Mesencephalon
Rhombencephalon
Which primary brain vesicle becomes the forebrain?
Prosencephalon
Which primary brain vesicle becomes the midbrain?
Mesencephalon
Which primary brain vesicle becomes the hindbrain?
Rhombencephalon
Which secondary brain vesicles arise from the prosencephalon?
Telencephalon
Diencephalon
Which secondary brain vesicles arise from the mesencephalon?
Mesencephalon
Which secondary brain vesicles arise from the rhombencephalon?
Metencephalon
Myelencephalon
What does the telencephalon become?
Cerebral hemispheres
What does the diencephalon become?
Thalamus
What does the mesencephalon become?
Midbrain
What does the metencephalon become?
Pons/cerebellum
What does the myelencephalon become?
Spinal cord
Label the 5 secondary primary vesicles on this picture.
Forebrain, midbrain and hindbrain are divisions of the brain based upon what?
Their embryological origin.
What does the forebrain contain?
Cerebral hemispheres (Telencephalon)
Thalamus (Diencephalon)
Hypothalamus (Diencephalon)
What does the hindbrain contain?
Cerebellum (Metencephalon)
Pons (Metencephalon)
Medulla Oblongata (Myelencephalon)
What is the medulla oblongata?
The lower part of the brainstem.
Which is the largest component of the brain?
Telencephalon / Cerebral hemispheres
What are the cerebral hemispheres separated by?
Longitudinal fissure
What is the cerebral cortex?
Grey matter outside layer of the cerebral hemispheres - 2.4mm thick
What is the primary function of the cerebral cortex?
Processing motor and sensory information - higher function, perceiving world around us.
How are the two cerebral hemispheres connected?
Via the corpus callosum - white matter layer.
What are depressions of the cerebral cortex called
Sulcus (pl. sulci)
What are elevations of the cerebral cortex called?
Gyrus (pl. gyri)
Why does the cerebral cortex have elevations and depressions?
To increase the SA - allows more neurons to fit into the same space.
What are the layers of the cerebral cortex called and how many of them are there?
6
Laminae
In which part of the brain are the limbic system and basal ganglia found?
Telencephalon
Name these lobes of the brain…
What is the theory of functional specificity?
Postulates that specific areas of the brain undertake a specific task.
What is the central depression in the brain called?
Central sulcus
What does the central sulcus represent in terms of function?
Is a broad demarcation in terms of function - Caudal to central sulcus = about receiving incoming information. Rostral to central sulcus = conscious response to the information.
What is the function of the frontal lobe?
Primary motor cortex, executive functions & ability to think
What is the function of the parietal lobe?
Primary somatosensory cortex (pain, touch, proprioception).
What is the function of the temporal lobe?
Primary auditory & olfactory cortexes + learning & memory
What is the function of the occipital lobe?
Primary visual cortex
Which part of the brain is responsible for 80% of association & cognition?
Cerebral cortex
What is association in terms of the brain?
It is the perception of the world through senses.
What is grey matter made of?
Neuronal cell bodies
Where is the grey matter located in brain?
In the cerebral cortex & brain nuclei (deep brain structures).
What is white matter made of?
Myelinated axons
What is grey matter divided into in the cerebral cortex?
Into layers (laminae)
What are brain tracts?
Neural pathways
Does information in brain tracts run unilaterally or bilaterally?
Bilaterally
Name the three types of brain tracts and describe each.
Commissural - across hemispheres (R-L)
Projection - vertically - from cerebral cortex to caudal structures
Association - horizontally within same hemisphere
What is the largest commissural tract in the brain?
The corpus callosum
What is the corpus callosum?
White matter tract that links the two cerebral hemispheres
What are the four parts of the corpus callosum?
Rostrum, genu, body & splenium
What does the corpus callosum enable?
Rapid communication between the two hemispheres.
Which is the largest white matter body in the brain?
Corpus callosum
What does the limbic system regulate?
Emotion & memory
What does the basal ganglia control?
Posture & voluntary movement (+ eye movement, emotional control & cognition).
Which parts of the brain are the limbic system found in?
The telencephalon & diencephalon (forebrain)
Which parts of the limbic system are found in the diencephalon?
Mamillary bodies, hypothalamus & thalamus
Which parts of the limbic system are found in the telencephalon?
Cingular cortex, fornix, amygdala & hippocampus
What are the main components of the diencephalon?
Thalamus, hypothalamus, sub thalamus & epithalamus + maxillary bodies
What are mamillary bodies thought to be involved in?
Memory formation
How many thalamus’ are there?
2
What is the thalamus made from?
Grey matter
What is the thalamus used as?
A major relay centre - communicates with a lot of the cerebral cortex & other parts of the cerebrum.
What does the thalamus do?
Receives much of the sensory input and relays this sensory information to the cortex
AND
Is involved with voluntary movement, personality & consciousness.
What connects the thalamus to other diencephalic structures?
Interthalamic adhesions
Why is the central location of the thalamus important?
It means it is best situated to relay information to and from all parts of the brain.
What is located inferiorly to the thalamus?
Hypothalamus
What does the hypothalamus do?
Homeostatic control - coordinates ANS & endocrine responses.
Thermoregulation, feeding, drinking & circadian rhythm
Receives input from the limbic system
What does the pituitary gland do?
Is an interface between the brain and the endocrine system.
What is the stalk of the pituitary gland called?
Infundibulum
What is the term for the crossing of the optic nerves to form optic tracts?
Decussation
What is the function of the brainstem?
Connects cortex to spinal cord
Respiration & CVS centres
Vomiting centre
Motor control & sleep
Contains white matter tracts
What do the cerebral peduncles do?
Connect brainstem to the thalami
What is found within the brainstem?
White matter tracts - connect pons to diencephalon
What does the superior colliculus control?
Eye movements
What does the inferior colliculus contain?
Relay nuclei (involved in auditory)
What does the substantia nigra contain?
Dopaminergic neurons & neuromelanin (gives it darker appearance)
What does the red nucleus do?
Is responsible for motor coordination
Also a major relay centre between cortex and cerebellum
What does the pons do?
Contains transverse fibres - links the brainstem to the cerebellum.
Also - generates rhythmic breathing pattern.
What does the pyramid of the medulla oblongata do?
Contains the corticospinal tract = voluntary motor pathway
Which is the lowest part of the brainstem?
Medulla oblongata
What does the medulla oblongata contain?
Nuclei responsible for controlling respiration & CVS.
How many hemispheres does the cerebellum have?
Two
What is the outside of the cerebellum made of?
Grey matter
What is the white matter inside the cerebellum called?
Arbour vitae
How many lobes dos the cerebellum contain?
What are they?
3 lobes
- Anterior lobe
- Flocculonodular lobe
- Posterior lobe
What is the cerebellum responsible for?
Limb movement
Eye movements
Motor control
Posture
Growing evidence for - cognition, fear & pleasure
How is the cerebellum connected to the brainstem?
By cerebellar peduncles
