Brain Anatomy Flashcards
What is gastrulation?
-Occurs @ week 2/3 of embryogenesis (after fertilisation)
-3 primary germ layers (endoderm, ectoderm, mesoderm) form & begin to form diff tissues
-Formation of gastrula from blastula (= embryology)
-Blastopore forms anus in humans - mouth breaks through @ ant end = forms through-gut
-In most animals this process forms gut
What is neurulation?
Occurs @ week 3/4 of embryogenesis (after fertilisation)
-Neural tube forms - important as will form brain, spinal cord, meninges & surrounding bones
-Neural plate bends up & later fuses - forms hollow tube - eventually differentiates into brain & spinal cord of CNS
–> so whole process of neurulation gives rise to brain & spinal cord
What do the 3 germ layers - ectoderm, mesoderm & endoderm - go on to from/give rise to?
-Ectoderm = gives rise to NS & skin
-Mesoderm = (originates from ectoderm) forms CT & bones, muscle, urogenital organs, pleura, peritoneal lining of body cavity
-Endoderm = lining of internal organs e.g., in GIT & airway lining
What starts/stimulates neurulation to occur?
Notochord
Explain how neurulation occurs.
-Lateral edges of ectoderm become elevated - forms neural fold
-Central depression = neural groove
–> whole layer = called the neural plate (of ectoderm)
-Image = top view
-Neurulation occurs/advances cranially & caudally - starts at mid region
-At end of neurulation - cranial end gives rise to brain & caudally gives rise to spinal cord
-Eventually the neural folds will fuse centrally - as neural fold occurs on either end (which is why get a neural groove in midline)
–> when this fusion occurs - converts neural plate into neural tube - this fusion starts in middle then advances cranially & caudally
–> to form neural tube - the neural folds meet, fuse - outer part of ectoderm moves down to surround endoderm & mesoderm
–> this neural tube is where the CNS will develop from
-@end of week form = neural tube is formed
-As neural tube forms -> some cells from ectoderm from tube migrate to form layers of cells - called neural crest -> neural crest gives rise to structures working closely with CNS e.g., peripheral NS spinal & cranial nerves & their ganglia, meninges ANS ganglia
–> remaining ectoderm - forms skin
How does neural tube go on to form CNS (brain & spinal cord) in rest of embryology/development - i.e., think of sections?
*Neural tube think of as having 4 sections that each go on to form different parts of CNS:
-Prosencephalon = becomes cerebrum & thalamus (forebrain)
-Mesencephalon = becomes midbrain
-Rhombencephalon = becomes pons, cerebellum, medulla (hindbrain)
-Spinal cord = becomes spine
What happens after the forebrain, midbrain, hindbrain & spine from?
Forebrain evaginated (turns inside out) = produces x2 secondary brain vesicles:
-Telencephalon
-Diencephalon
–> this occurs from primary brain vesicles -> to secondary brain vesicles
Summarise what is found in the forebrain, (midbrain just contains ‘midbrain’), hindbrain (& spinal cord just contains ‘spinal cord’)?
*Forebrain
-Telencephalon = cerebral cortex, basal ganglia
-Diencephalon = thalamus, hypothalamus, retina
*Midbrain
*Hindbrain = cerebellum, pons, medulla
*Spinal cord
-Somites from from mesoderm germ layer
How many ventricles in the brain & what is in them?
-4 ventricles = laterals (x2), 3rd ventricle, 4th ventricle
-Contain cerebrospinal fluid (CSF)
What components of the brain have evolved SO significantly?
-Cerebellum (in amniote stem lineage probably = where rats evolve from)
-Cerebral cortex (in mammalian stem lineage probably) -> folding of cerebral cortex creates gyri & sulci = separate brain regions, increase brain’s SA & cognitive ability
What does a lateral view of primary and secondary brain vesicles & post-natally (or from 2nd trimester onwards) look like - describe?
-Primary brain vesicles = (can still see prosencephalon, mesencephalon, rhombencephalon & spinal cord) - also see cephalic flexure (@ mesencephalon) & cervical flexure (@ rhombencephalon - between hindbrain & spinal cord)
-Secondary brain vesicles = (now can see telencephalon and diencephalon [from division of prosencephalon], mesencephalon, metencephalon and myelencephalon [from division of rhombencephalon] & spinal cord) - also see pontine flexure (which divides hindbrain into metencephalon rostrally & myelencephalon caudally)
–> can also see the 4 ventricles
-From 2nd trimester of pregnancy onwards = cortex dominates - along with cerebellum (due to prolif of neural progenitor cells)
–> post-natally - these structures dominate cranial cavity
Label these brain axis.
Label the names of the different spinal nerve levels, and the parts of the brain shown.
What are the 4 lobes of the cerebral cortex?
-Names correspond to the overlying cranial bone
*Frontal lobe
*Temporal lobe
*Parietal lobe
*Occipital lobe
What section is this image of the brain?
Axial section
What are 4 major components of the basal ganglia?
-Dorsal striatum (made of caudate + putamen)
-Ventral striatum (made up of nucleus accumbens + olfactory tubercle)
-Globus pallidus (external = Gpe, internal = Gpi)
-Ventral pallidum
Where is the dorsal striatum?
Where is the ventral striatum?
Where is the globus pallidus?
Sits above ventral pallidum
Where is the ventral pallidus?
Label the structures shown which are part of the basal ganglia.
Name the structures shown in different colours.
What section of the brain is this?
Midsagittal section
What are the 2 anatomical divisions of the brain stem?
-Midbrain
-Pons
-Medulla
Where is the 3rd ventricle of the brain located?
Within the diencephalon (containing thalamus + hypothalamus)
Where is the 4th ventricle of the brain located?
Within the hindbrain - rhombencephalon (pons + medulla + cerebellum)
What view of the brain is this?
Dorsal view - cortex & cerebellum removed
What is the function of the thalamus?
Relay station for info being communicated to –> the cortex
Function of the midbrain?
-Role in visual & auditory reflexes - dorsally
-Motor functions - ventrally
What is the function of the pons?
Communicates info between cerebellum & rest of CNS
What is the function of the medulla?
Coordinates subconscious sensorimotor integration
What is the function of the cerebellum (‘little brain’)?
Integrates proprioceptive info with motor commands –> so conditions of cerebellum often involve balance & coordination problems
What are the 4 roles of the cerebellum?
What are the 3 parts of the cerebral cortex?
-Paleocortex - 3 layers = smell perception (olfaction)
-Archicortex - 2-4 layers = learning, memory
-Neocortex - unique to mammals - dominates human cerebral cortex - has 6 layers = perception, association, reacting
–> 6 layer of cortex vary in thickness across different brain regions
What are Brodmann areas of the brain?
Brain regions defined by different thicknesses in the 6 layer of the cortex - for functional purposes
Divided based on cytoarchitecture or histological structure & cell organisation
Function of the primary motor cortex Brodmann area number 4 (M1 - BA4)?
-In frontal lobe
-AKA precentral gyrus
-This region has a topographic map (map of the body’s muscles) - so it can coordinate the motor commands of different body parts/muscles
-Different muscles - have differing amounts of neural circuitry dedicated to operating them
-Most no. of neurons here = dedicated to moving lips (motor control of lips)
–> i.e., the density of cortical neurons that generate info = proportional to the degree of control in the body
Function of the primary somatosensory cortex (S1 - BA1/2/3)?
-Parietal lobe
-AKA called the postcentral gyrus
-This region also has a topographic map (map of body) - so it can receive information from spinal & brainstem nuclei, primary sensory neurons & the outside world
-> so info regarding touch, pain & proprioception is sent here from the places said above
Function of the primary auditory cortex (A1 - BA41)?
-In temporal lobe
-This region also has a topographic map (of sound frequency along primary auditory cortex) - meaning different pitches of sound frequency will be perceived/interpreted by different areas of cortex
Function of the primary visual cortex (V1 - BA17)?
-At back of occipital lobe (posterior)
-Topographic map in the primary visual cortex - mapping out the visual world (everything you can see)
-Computes our visual sense of the world - neurones found medially & laterally (green in image)
How can the brains of humans, cats and rats be compared?
In human brain = vast majority isn’t primary functional areas - but are the association cortex areas/points - ability to connect ideas - complex idea formulation
–> compared to rats & cats whose brains are mostly made up of these primary functional areas (shown in image)
-Also - level of gyrification - no. of gyri & sulci = more in human
