Topography of the brain Flashcards
Describe the development of the brain (neurulation)
Neuroectoderm cells receive inductive signals from notochord
Cells thicken to form neural plate
Lateral neural plate margins fold inwards to form neural tube
Which cells (cell types) arise from the differentiation of neural crest cells?
At what age does this occur?
- Neurons and glia of the sensory and autonomic nervous systems
- Cells of the adrenal gland
- Epidermis
- Skeletal/ connective tissue of the head
Embryonic day 24
What is the function of the mantle layer, ependymal layer and lumen of the neural tube?
Mantle layer becomes the brain parenchyma
Ependymal lines the ventricles
Lumen becomes the ventricles and central canal
Describe 2 neural tube defects
Anencephaly: Failure of anterior neuropore to close. 1/1000. FATAL
Spina bifida: failure of posterior neural tube to close. 1-2/1000. Leads to open vertebral canal
Whats the difference between spina bifida occulta and spina bifida cystica?
SBO- hidden, vertebral arch defect only
SBC- e.g. meningocele= meninges projects out
Expansion of the cranial end of the neural tube forms the the main brain regions. What are these?
Prosencephalon= forebrain Mesencephalon= midbrain Rhombencephalon= hindbrain
Primary vesicles on LHS
Which secondary vesicles arise from the prosencephalon (forebrain)?
Telencephalon= cerebral hemispheres
Optic vesicles= eyes
Diencephalon= thalamus/hypothalamus
Which secondary vesicles arise from the Rhombencephalon (hindbrain)?
Metencephalon= Pons/cerebellum Myelencephalon= Medulla
Which secondary vesicles arise from the Mesencephalon (Midbrain)?
None
At which embryonic day do the secondary vesicles arise?
36
What is the difference between gray and white matter?
Gray matter (peripheral)- mainly neuronal cell bodies (e.g. cerebral cortex, brain nuclei)
White matter- mainly myelinated axons
What is the telencephalon and how is it arranged?
Comprises the cerebral hemispheres/cerebral cortex, components of the limbic system and the basal ganglia
Divided into lobes: frontal- primary motor cortex parietal- somatosensory cortex temporal- auditory and olfactory cortex occipital- primary visual cortex
What is the cerebral cortex?
Outer layer of the cerebral hemispheres
Folded to form gyri and sulci
Precentral gyrus (motor), central sulcus (divides frontal and parietal lobes), postcentral gyrus (sensory), lateral sulcus (divides temporal from parietal lobe)
What is the corpus callosum?
White matter tract linking cerebral hemispheres.
3 parts:
Genu- contains axons from pre-frontal complex
Body- contains motor axons
Splenium- contains sensory axons
Briefly state the deep brain structures
Brain nuclei and white matter tract deep to cerebral hemispheres
Interconnected to form important neural pathways including:
Limbic system- involved with emotion and memory
Basal ganglia- involved in the control of posture and voluntary movement
Explain the limbic system
Spans the telencephalon and diencephalon
Components include: cingulate cortec, fornix, hypothalamus, mammillary bodies, amygdala, hippocampus
The fornix is a semi-circular white matter tract connecting the hippocampus with the mammillary bodies
What is continuous with the hippocampus?
Dente gyrus
Describe the basal ganglia
Series of interconnected nuclei at base of forebrain
It includes
- Lentiform nucleus (lens shaped)- sits lateral to caudate nucleus
- Caudate nucleus (C-shaped)- sits in wall of lateral venricle
Describe the capsules
There two
Internal capsule forms major white matter tract (its internal to leniform nucleus)
External capsule external to leniform nucleus
Describe the diencephalon
Comprises the thalamus and hypothalamus (+corpus callosum and fornix)
Describe the thalamus
Paired structure
Relays sensory information to the cortex
Involved with voluntary movement, personality and consciousness
Interthalamic adhesions connect the thalamus
Describe the hypothalamus
Inferior to the thalamus, between the optic chiasm and mammilary bodies
Involved in homeostasis- coordinates ANS and endocrine processes, thermoreg, feeding, drinking, circadian rhythms and recieves inputs from limbic system
What is contained within the brainstem?
Cranial nerve nuclei within all three regions
Vital respiratory and cardiovascular centres
Vomiting centre
Nuclei involved with motor control, sleep
White matter tracts
In the midbrain describe the function of the cerebral peduncles, superior colliculus and inferior colliculus.
Cerebral peduncles- white matter tracts connecting pons with diencephalon
Superior colliculus- vision (eye movements)
Inferior colliculus- auditory (relay nuclei)
In the midbrain, describe the role of the red nucleus and substantial nigra
Red nucleus- motor coordination- relay between cortex and cerebellum
Substantial nigra- dopaminergic neurons, part of basal ganglia
What are the features of the Pons (Rhombencephalon) and what does it do?
Relays information to the cerebellum
90% of axons descending through midbrain synapse in pons
Transverse fibres forming cerebellar peduncles
- Middle cerebellar peduncle is a white matter tract linking the brainstem to cerebellum
Contains reticular formation
-Nuclei concerned with sleep, motor control
What are the features of the medulla oblongata and what does it do?
Pyramid- corticospina tract- main voluntary motor pathway
Olive- formed by olivary nuclei
Motor relay to cerebellum
Cuneate tubercle and gracile tubercle - nuclei form part of ascending tract
Contains nuclei that are important in controlling respiration and the CVS
What does the Cerebellum look like and what does it do?
Posterior to brainstem Outer gray matter with underlying white matter 2 cerebellar hemispheres Three lobes Contains nuclei
Main functions in motor control:
Control of posture
Coordinating and planning limb movements
Control of eye movements
State the anatomical features of the cerebellum
Arbor vitae (tree of life) Cerebellar cortex
Anterior lobe
Flocculonodular lobe
Posterior lobe
Two hemispheres - left and rights
Vermis in middle
Connected to brainstem by cerebellar peduncles
