Introduction to neuroanatomy Flashcards
How many synapses does each cell form
Around 10,000
What are the 2 types of synapses
Chemical or electric
What 2 types of receptors does the nervous system use
Ionotropic and metabotropic receptors
What do we do to cells to view them
Harden tissue without destroying its structure (fixative-formaldehyde)
Microtome (section brain tissue into small sections)
Staining techniques
What helps form the blood-brain barrier around the blood vessels
Astrocytes’ end feet
What is a gathering of neuron cell bodies in PNS
Ganglion
What is a cluster of neurons in CNS, usually deep in the brain
Nucleus
What is a nerve
Bundle of long axons in in PNS
What is a tract
Bundle of axons in CNS with a common site of origin and destination
What makes up the CNS
Brain- cerebrum, cerebellum, brainstem
Spinal cord
What can the cerebrum be split up into
Diencephalon and cerebral hemisphere
What can the cerebral hemisphere be split up into
Cerebral cortex, basal ganglia, hippocampus amygdala
What can the diencephalon be split into
Thalamus and hypothalamus
What can the brainstem be split into
Midbrain, pons, medulla
What is grey matter vs white matter
Grey matter- generic collections of neuronal cell bodies in CNS
White matter- tracts of myelinated nerve cells in CNS
How do nerve cells tend ot be grouped
In CNS- clusters or layers, with their associated nerve fibres forming the axon tracts
Who first described the neuron
Purkinje in 1837
Who laid the foundation of our knowledge of cellular organsiation of the brain
Cajal in his studies of the adult and developing nervous system
Provided descriptions of synapses and their proposed function, with detailed drawings
What method did Cajal use to visualise neurons and glia
The Golgi method aka impregnation- place a section of brain in a beaker containing potassium dichromate and silver nitrate, silver chromate precipitates out within the cytoplasm of cells
What other modulatory factors of the nervous system are not recognised in the simple Neuron Doctrine
Gap junctions which modulate cell activation, modulatory receptors on pre-synaptic elements, modulatory action of transmitters/hormones in the local environment which affect neuronal activity
In which direction does conduction take palce
Dendrites to soma to axon terminals
Who from Oxford made a big contribution to neuroanatomical nomenclature
Thomas Willis (1621-1675)
3 vesicle stage of development- what are the 4 sections
Forebrain, midbrain, hindbrain, caudal part of neural tube
Development- what does the forebrain develop into in the 5 vesicle stage
Telencephalon (2 cerebral hemispheres), diencephalon
Development- what does the midbrain develop into
Midbrain
Development- what does the hindbrain develop into
Pons, medulla, cerebellum
Development- what does the caudal part of the neural tube develop into
The spinal cord
What cavity lies between the 2 parts of the diencephali
3rd ventricle
What cavity results from the midbrain
Aqueduct, surrounded by a region of grey matter called the periaqueductal grey
What cavity results from te hindbrain
Fourth ventricle
What cavity results from the caudal part of the neural tube
Central cantral
What are the 3 coverings of meninges surrounding the CNS
Dura mater, arachnoid mater, pia mater
What is the dura mater
Tough fibrous covering applied to the periosteum of the cranium
Has folds that extend between the main lobes of the CNS eg the falx cerebri
What is the periosteum
Membrane covering the outside of all bones
What is the arachnoid mater
Fine membraneous layer that lies beneath the dura mater
What is the pia mater
The part of the surface of the CNS, formed by glial and mesothelial cells
What causes an epidural hematoma
Skull fracture and injury of the meningeal artery, results in blood between skull and dura mater
What causes a subdural hematoma
Injury to bridging veins, results in blood between dura mater and arachnoid matter
What causes a subarachnoid hemorrhage
Ruptured aneurism, leads to build up of fluid in subarachnoid space
What is the structure of the cerebral hemispheres
The cerebral cortex forms the largest part of the human brain and can be subdivided into the occipital, parietal, frontal and temporal lobes
The surface has regular folds called gyri divided by a series of grooves called sulci
What are the functional subdivisions of the cortex
eg visual, somatosensory, auditory
What are secondary areas that are provided informatino by functional subdivisions of the brain
eg parietal association area, inferotemporal cortex, limbic regions
What is the corpus callosum and cingulated bundle examples of
Long distance fibre tracts connecting areas of the cortex and other brain areas
What is formed by nerve fibres passing into and away from the cortex to the brain stem (esp the thalamus)
The internal capsule
What cavities are at the core of the hemisphere
Lateral ventricles filled with cerebrospinal fluid
What is the choroid plexus
An epithelial ependyma responsible for producing CSF, found covering strands of tightly coiled vascular tissue within the lateral, 3rd and 4th ventricles
Which ventricle has the choroid plexus that makes the biggest contribution to producing CSF
The lateral ventricles
What is the tela choroidea
Describes the whole invagination, the functional unit responsible for producing CSF- ‘choroid plexus’ often refers to the tela choreoidea
How does CSF travel between the lateral ventricles to the 4th ventricle
Passes from the choroid plexus via the interventricular foramen into the 3rd ventricle, then posteriorly through the cerebral aqueduct into the 4th vesicle
How does the CSF travel from the 4th vesicle to the brain and spinal cord
The CSF passes through the foramen of Magendie and the lateral foramina of Luschka (that it uses to communicate with the subarachnoid space) to occupy the subarachnoid space around the brain and spinal cord
What are the arachnoid villi
Tufts of arachnoid mater that pierce the inner meningeal layer of the dura- they reabsorb CSF into the vascular system
What is hydrocephalus
An increase in cerebrospinal fluid volume, usually resulting from impaired absorption
What is obstructive hydrocephalus
Obstruction to CSF flow within the ventricular system
What is communicating hydrocephalus
Obstruction to CSF flow beyond the ventrical system ie ventricular CSF communicates with the subarachnoid space
What does hydrocephalus cause
Raised intracranial pressure, white matter damage and gliotic scarring, if untreated causes grey matter damage
Can cause head expansion and massive ventricular dilation in infants
What does the term the limbic cortex encompass
The components of the limbic lobe and associated structures eg enthorinal and septal areas, amygdaloid complex and mamillary body
What is the basal ganglia
A cluster of deep nuclei- includes the caudate nucleus, the putamen, and lentiform nucleus (medial to the internal capsure)
What does the thalamus do
With the exception of the olfactory projections all afferent info to the cortex relays through the thalamus
There is also a lot of interconnection between the thalamic nuclei and association cortex
Regulates awareness and emotional aspects of sensation
What lies below the thalamus
The hypothalamus which controls many of our automatic and endocrine functions, has extensive connections with the thalamus and midbrain
What is the tectum
Formed by the midbrain, and formed from the superior and inferior colliculi
What is below the aqueduct of the midbrain
The red nucleus and the massive fibre bundles that originate in the cerebral cortex and pass to the pons, medulla and spinal cord
What forms the pons
The massive fibre tracts and pontine nuclei that relay info from the cerebral cortex to the cerebellum (pons=bridge)
Where does the medulla lie
Beneath the caudal part of the cerebellum
What forms the dorsal surface of the medulla
The 4th ventricle
What lies in the medulla
Many of the cranium nerve nuclei, and the fibre tracts passing to and from the spinal cord and between cranial nerve nuclei
What 3 functional regions can the cerebellum be subduvided into
Vestibulo-cerebellum, spino-cerebellum and ponto-cerebellum
What does the vestibulo-cerebellum do
Comprises floccular-nodular lobe which receives inputs from the vestibular system concerned with the position of the body in space
What does the spino-cerebellum do
Lies in the midline of the cerebellum, receives info from the spinal cord and is concerned with the position and movement of the limbs
What does the ponto-cerebellum do
Forms the lateral cortex via the pontine nuclei, has various functions concerned with pre-programming and monitoring motor programs
What are the gyri of the cerebellar cortex called
Folia
What are the 3 large fibre tracts conveying fibres to and from the cerebellar cortex
Inferior peduncle, middle peduncle, superior peduncle
What is the midline
The invisible line running down the middle of the nervous system
What is bilateral symmetry
When structures either side of the midline are mirror images of one another
What does medial vs lateral mean
Medial- structures closer to the midline
Lateral- structures further away from the midline
What term describes 2 structures on the same side of the midline
Ipsilateral to one another
What term describes 2 structures on opposite sides of the midline
Contralateral
What does the cerebellum mean in Latin
‘little brain’
How is info processed by the cerebellum different to info processeed by the cerebral hemispheres
The left side of the cerebellum controls the movements of the left side of the body and vv
What are afferent axons
‘Carry to’- somatic or visceral sensory axons bringing info into the CNS
What are efferent axons
‘Carry from’- axons that emerge from the CNS to innervate muscles and glands
What is the ventricular system composed of
Fluid-filled caverns and canals inside the brain
What is the entire CNS derived from in development
The walls of a fluid-filled tube formed at an early stage in embryonic development, with the inside of the tube becoming the adult ventricular system
What is a cortex
Any collection of neurons forming a thin sheet, usually at the brain’s surface
What is a substantia
A group of related neurons deep inside the brain with usually less distinct borders than nuclei
What is an example of a ganglion
Dorsal route ganglia which contains the cell bodies of sensory axons entering the spinal cord via the dorsal routes
What is the only cell group in the CNS called a ganglion
Basal ganglia, structures lying deep in the cerebrum that control movement
What is the only collection of CNS axons called a nerve
The optic nerve
What is a capsule
Collection of axons that connect one side of the brain with the brain stem
What is a commissure
Any collection of axons tha connect one side of the brain with the other side
What does the embryo start as
A flat disk with 3 distinct cell layers- endoderm (gives rise to lining of viscera), mesoderm (bones and muscles), and ectoderm (nervous system and skin)
What part of the ectoderm gives rise to the nervous system
The neural plate
What forms in the neural plate
A neural groove forms in the neural plate that runs rostral to caudal
The walls of the neural groove are neural folds, which move together and fuse forming the neural tube
What is produced as the neural folds come together forming the neural tube
Some neural ectoderm is pinched off and lies lateral to the neural tube- the neural crest
What do all neurons with cell bodies in the PNS derive from
The neural crest
How does the mesoderm develop following the formation of the neural crest
The mesoderm forms prominent bulges either side of the neural tube called somites, from which the 33 vertebra of the spinal column and related skeletal muscles later deelop
What is the name of the process of the neural plate becoming the neural tube
Neurulation
What is differentiation
The process through which structures become mroe compelx and functionally specialised
What vesicles does the entire brain derive from
3 primary vesicles of the neural tube
How do the neurons of the developing forebrain extend
Extend axons to communicate with other parts of the nervous system that bundle together to form 3 major white matter systems- the cortical white matter, the corpus callosum and the internal capsule
What does the cortical white matter contain
All the axons that run to and from the neurons in the cerebral cortex
What is the corpus callosum
Continuous with the cortical white matter, forms an axonal bridge that links cortical neurons with the 2 cerebral hemispheres
How does the cerebellum grow from the rostral hindbrain
The tissue along the dorsal lateral wall of the tube grows dorsally and medially until it fuses with its twin on the other side- the resulting flap of brain tissue grows into the cerebellum
What are the medullary pyramids
A major white matter system along the ventral surface of each side of the medulla
What is the pyramidal decussation
Near where the medulla joins with the spinal cord, axons in the pyrimadal tract cross from one side to the other
How is the spinal canal formed from the caudal neural tube
The tissue in the walls of the caudal neural tube expand, constricting the cavity of the tube to form the tiny CSF filled spinal canal
What does the grey matter of the spinal cord look like
A butterfly- the upper part of the wing is the dorsal horn, the lower part is the ventral horn, and the grey matter between the horns is the intermediate zone
What is the white matter in the spinal cord
Columns of axons running up and down the spinal cord - the bundles of axons lateral to the spinal grey matter are lateral columns, and the bundles on the ventral surface are ventral columns
What does dorsal vs ventral mean
Dorsal or posterior means back, ventral or anterior means front
What does caudal vs rostral mean
Caudal means lower down, rostral means higher up
What are the directions described by dorsal/ventral/caudal/rostral relative to
The neural tube- when the neural tube enters up into the brain, the directions are tilted eg dorsal now refers to the top of the brain and rostral refers to the front of the brain
What does the pons look like
The bump outwards at the top of the medulla below the midbrain
Where is the cerebellum located
Lies behind the pons, at the dorsal end of the brain
Where is the diencephalon located
Rostral to the midbrain
What are unipolar cells
Have a single process with many branches- one serves the axon and others act as dendritic receiving structures, meaning they have no dendrites emerging from the soma
What are bipolar neurons
2 functionally specialised processes, a dendrite and an axon
What 4 types of signals at different sites within the cell do all participating sensory and motor cells generate
An input signal, an integration (trigger) signal, a conducting signal and an output signal
Examples of a disease that only affects one type of neuron
Poliomyelitis only affects motor neurons
What is the peripheral nervous system composed of
Groups of neurons called ganglia and peripheral nerves that lie outside the brain and spinal cord
What are the 2 divisions of the PNS
Somatic and autonomic division
What does the somatic nervous system do
Provides CNS with sensory info about body position and environment
What does the somatic nervous system consist of
Sensory neurons of the dorsal root and cranial ganglia that innervate the skin/muscles/joints
The cell bodies of these lie outside the spinal cord in dorsal root ganglia, one for each spinal nerve
What does the autonomic nervous system do
Motor system for viscera, smooth muscles and exocrine glands
What are the 3 spatially segregated subdivisions of the autonomic nervous system
Sympathetic- body response to stress, parasympathetic-conserve resources and restore resting state, enteric-controls function of smooth muscle of the gut
How is the spinal cord segmented into pairs
31 pairs of spinal nerves in humans
What are spinal nerves
Peripheral nerves formed by the joining of the dorsal and ventral roots
How many pairs of cranial nerves cary the sensory input/motor output of the brain stem
12 pairs…also contains ascending/descending pathways to carry info to and from higher brain regions
What does the medulla do
Regulates blood pressure and respiration working with the pons
What does the cerebellum do
Coordinates skeletal muscle during mvoement using info from spinal cord, cerebral cortex and vestibular organs
Maintains posture and controls head and eye movement
What does the midbrain do
Several regions help direct control of eye movement or motor control of skeletal muscles, essential relay station of auditory and visual signals
What do the cerebral hemispheres do
Concerned with perceptual, cognitive and higher motor functions as well as emotion and memory
What is the cerebral cortex
The high wrinkled surface of the cerebral hemisphere
What are the 2 subdivisions of the cerebral cortex other than the main lobes
Insular cortex and limbic lobe
What is the insular cortex
Occupies medial wall of lateral sulcus, not visible on the surface of the brain
What is the limbic lobe
Consists of the medial portions of the frontal, parietal and temporal lobes that form a continuous band of cortex overlying the rostral brain stem
