Neuroanatomy Flashcards
What is the cerebrum?
The cerebrum is the largest part of the brain, located superiorly and anteriorly in relation to the brainstem
What separates the lobes of the cerebrum?
It consists of two cerebral hemispheres (left and right), separated by the falx cerebri of the dura mater.
Which cranial fossa does the cerebrum lie in?
Within the skull, the cerebrum fills the anterior and middle cranial fossae,
What does the grey matter of the cerebrum make up?
Grey matter forms the surface of each cerebral hemisphere (known as the cerebral cortex), and is associated with processing and cognition.
What does the white matter of the cerebrum make up and consist of?
White matter forms the bulk of the deeper parts of the brain. It consists of glial cells and myelinated axons that connect the various grey matter areas.
What is the longitudinal fissure?
A major sulcus that runs in the median sagittal plane.
Where and what is the falx cerebri?
The falx cerebri (a fold of dura mater) descends vertically to fill the longitudinal fissure.
What are the two main sulci of the brain?
Central sulcus – groove separating the frontal and parietal lobes.
Lateral sulcus – groove separating the frontal and parietal lobes from the temporal lobe.
What are the three main gyri of the brain?
Precentral gyrus – ridge directly anterior to central sulcus, location of primary motor cortex.
Postcentral gyrus – ridge directly posterior to central sulcus, location of primary somatosensory cortex.
Superior temporal gyrus – ridge located inferior to lateral sulcus, responsible for the reception and processing of sound.
What are the functions of the frontal lobe?
Higher intellect, personality, mood, social conduct and language (dominant hemisphere side only).
What are the functions of the parietal lobe?
Language and calculation on the dominant hemisphere side, and visuospatial functions (e.g. 2-point discrimination) on the non-dominant hemisphere side.
What are the functions of the temporal lobe?
Memory and language – this includes hearing as it is the location of the primary auditory cortex.
What is the function of the occipital lobe?
The primary visual cortex (V1) is located within the occipital lobe and hence its cortical association area is responsible for vision.
What does the anterior cerebral arteries branch off and what does it supply?
Branches of internal carotid arteries, supplying the anteromedial aspect of the cerebrum.
Where does the middle cerebral artery come from and what does it supply?
Continuation of internal carotid arteries, supplying most of the lateral portions of the cerebrum.
Where does the posterior cerebral artery come from and what does it supply?
Branches of vertebral arteries, supplying both the medial and lateral sides of the cerebrum posteriorly.
Where is the cerebellum?
The cerebellum is located at the back of the brain, immediately inferior to the occipital and temporal lobes, and within the posterior cranial fossa.
What separates the cerebellum from the temporal and occipital lobes?
It is separated from these lobes by the tentorium cerebelli, a tough layer of dura mater.
What separates the cerebellum and the pons?
It lies at the same level of and posterior to the pons, from which it is separated by the fourth ventricle.
How many hemispheres does the cerebellum have?
The cerebellum consists of two hemispheres which are connected by the vermis, a narrow midline area.
What are the four nuclei in the cerebellum?
The dentate, emboliform, globose, and fastigi nuclei
What are the three anatomical lobes of the cerebellum and what separates them?
The anterior lobe, the posterior lobe and the flocculonodular lobe. These lobes are divided by two fissures – the primary fissure and posterolateral fissure.
What is the blood supply of the cerebellum?
The cerebellum receives its blood supply from three paired arteries:
Superior cerebellar artery (SCA)
Anterior inferior cerebellar artery (AICA)
Posterior inferior cerebellar artery (PICA)
What is the function of the meninges?
Provide a supportive framework for the cerebral and cranial vasculature.
Acting with cerebrospinal fluid to protect the CNS from mechanical damage.
What are the two layers of the dura mater?
Endosteal layer – Lines the inner surface of the bones of the cranium.
Meningeal layer – Lines the endosteal layer inside the cranial cavity. It is the only layer present in the vertebral column.
Where are the venous sinuses and what do they do?
Between these two layers, the dural venous sinuses are located. They are responsible for the venous vasculature of the cranium, draining into the internal jugular veins.
What is the blood supply and innervation of the dura mater?
The dura mater receives its own vasculature; primarily from the middle meningeal artery and vein. It is innervated by the trigeminal nerve (V1, V2 and V3).
What is the arachnoid mater made of?
It consists of layers of connective tissue, is avascular, and does not receive any innervation.
Where is the sub-arachnoid space and what does it contain?
Underneath the arachnoid is a space known as the sub-arachoid space. It contains cerebrospinal fluid, which acts to cushion the brain.
How does CSF enter the venous sinuses?
Small projections of arachoid mater into the dura (known as arachnoid granulations) allow CSF to re-enter the circulation via the dural venous sinuses.
What is the function of the ventricular system?
These structures are responsible for the production, transport and removal of cerebrospinal fluid, which bathes the central nervous system.
What is the function of CSF?
Protection – It acts as a cushion for the brain, limiting neural damage in cranial injuries.
Buoyancy – By being immersed in CSF, the net weight of the brain is reduced to approximately 25 grams. This prevents excessive pressure on the base of the brain.
Chemical stability – The CSF creates an environment to allow for proper functioning of the brain. E.g. Maintaining low extracellular K+ for synaptic transmission.
What are the ventricles of the brain?
The ventricles are structures that produce cerebrospinal fluid, and transport it around the cranial cavity.
How many ventricles are there in the brain?
In total, there are four ventricles; right and left lateral ventricles, third ventricle and fourth ventricle. (this is a picture from a superior view)
Where are the lateral ventricles?
The left and right lateral ventricles are located within their respective hemispheres of the cerebrum. They have ‘horns’ which project into the frontal, occipital and temporal lobes.
What connects the lateral and third ventricles?
The lateral ventricles are connected to the third ventricle by the foramen of Monro.
Where is the third ventricle?
The third ventricle is situated in between the right and the left thalamus.
Where does the fourth ventricle receive CSF from?
The fourth ventricle is the last in the system – it receives CSF from the third ventricle via the cerebral aqueduct.
Where is the fourth ventricle?
It lies within the brainstem, at the junction between the pons and medulla oblongata.
Where does the CSF drain from the fourth ventricle?
Central spinal canal – Baths the spinal cord
Subarachnoid cisterns – Baths the brain, between arachnoid mater and pia mater. Here the CSF is reabsorbed back into the circulation.
What is the pineal gland?
The pineal gland is a small endocrine gland located within the brain.
What does the pineal gland secrete?
Its main secretion is melatonin, which regulates the circadian rhythm of the body. It is also thought to produce hormones that inhibit the action of other endocrine glands in the body.
What are the two types of cells in the pineal gland?
There are two types of cells present within the gland:
Pinealocytes – hormone secreting cells.
Glial cells – supporting cells.
Where is the pineal gland?
The pineal gland is a midline structure, located between the two cerebral hemispheres. It is attached by a stalk to the posterior wall of third ventricle.
What does the dorsal column-medial lemniscus pathway do?
The dorsal column-medial lemniscal pathway (DCML) carries sensory modalities of fine touch (tactile sensation), vibration and proprioception.
What do the first order neurones in the dorsal column-medial lemniscus pathway carry?
First order neurones carry sensory information from touch or proprioceptive receptors to the medulla oblongata.
What part of the dorsal column-medial lemniscus tract does information from the upper limb travel in?
Signals from the upper limb travel in thefasciculus cuneatus (the lateral part of the dorsal column). They then synapse in the cuneate nucleus of the medulla oblongata.
What part of the dorsal column does information from the lower limb travel in?
Signals from the lower limb travel in the fasciculus gracilis (the medial part of the dorsal column). They then synapse in the gracile nucleus of the medulla oblongata
What do second order neurones in the dorsal column-medial lemniscus tract do?
Second order neurones begin in the cuneate nucleus or gracilis. The fibres receive the information from the preceding neurones, and delivers it to the third order neurones in the thalamus. Within the medulla oblongata, these fibres decussate (cross to the other side of the CNS). They travel in the contralateral medial lemniscus to reach the thalamus.
What do third order neurones in the dorsal column-medial lemniscus tract do?
Third order neurones take the sensory signals from the thalamus to the primary sensory cortex of the brain. They ascend from the ventral posterolateral nucleus of the thalamus, through the internal capsule, terminating at the sensory cortex.
What are the two tracts in the anterolateral spinothalamic system?
The anterior spinothalamic tract carries the sensory modalities of crude touch and pressure.
The lateral spinothalamic tract carries the sensory modalities of pain and temperature.
What do first order neurones in the spinothalamic tract do?
First order neurones arise from the sensory receptors in the periphery. They enter the spinal cord, ascend 1-2 levels, and terminate at the tip of the dorsal horn (an area known as the substantia gelatinosa).
What do second order neurones in the spinothalamic tract do?
Second order neurones carry the sensory information from the substantia gelatinosa to the thalamus. Arising from a synapse with the preceding neurones, the neurones decussate(cross to the other side of the CNS). Here, fibres split:
Crude touch and pressure fibres enter the anterior spinothalamic tract.
Pain and temperature fibres enter the lateral spinothalamic tract.
What do third order neurones in the spinothalamic tract do?
Third order neurones take the sensory signals from the thalamus to the primary sensory cortex of the brain. They ascend from the ventral posterolateral nucleus of the thalamus, through the internal capsule, terminating at the sensory cortex.
Where are the asceding tracts in the spinal cord?
What are descending tracts?
The descending tracts are the pathways by which motor signals are sent from the brain to lower motor neurones. The lower motor neurones then directly innervate muscles to produce movement. They are the upper motor neurones
Are there synapses in the descending pathways?
There are no synapses within the descending pathways. At the termination of the descending tracts, the neurones synapse with a lower motor neurone
Where are the cell bodies of the descending tracts?
Their cell bodies are found in the cerebral cortex or the brain stem, with their axons remaining within the CNS.
What are the pyramidal tracts responsible for?
These pathways are responsible for the voluntary control of the musculature of the body and face.
What are the two pyramidal tracts?
Corticospinal tracts – supplies the musculature of the body.
Corticobulbar tracts – supplies the musculature of the head and neck.
Where do the corticospinal tracts receive information from?
The corticospinal tracts begin in the cerebral cortex, from which they receive a range of inputs:
Primary motor cortex
Premotor cortex
Supplementary motor area
They also receive nerve fibres from the somatosensory area, which play a role in regulating the activity of the ascending tracts.
What is the path of the corticospinal tract?
After originating from the cortex, the neurones converge, and descend through the internal capsule. After the internal capsule, the neurones pass through the crus cerebri of the midbrain, the pons and into the medulla. In the most inferior (caudal) part of the medulla, the tract divides into two: the anterior and the lateral corticospinal tracts.
Where do fibres in the lateral corticospinal tract go?
The fibres within the lateral corticospinal tractdecussate after the medulla(cross over to the other side of the CNS). They then descend into the spinal cord, terminating in the ventral horn (at all segmental levels). From the ventral horn, the lower motor neurones go on to supply the muscles of the body.
Where do fibres in the anterior corticospinal tract go?
The anterior corticospinal tract remains ipsilateral, descending into the spinal cord from the medulla. They then decussate and terminate in the ventral horn of the cervical and upper thoracic segmental levels.
What is the path of the corticobulbar fibres?
The corticobulbar tracts arise from the lateral aspect of the primary motor cortex. The fibres converge and pass through the internal capsule to the brainstem. The neurones terminate on the motor nuclei of the cranial nerves. Here, they synapse with lower motor neurones, which carry the motor signals to the muscles of the faceand neck.
Are the corticobulbar tracts bilateral or controlateral or ipsilateral?
Many of these fibres innervate the motor neurones bilaterally. There are a few exceptions to this rule:
Upper motor neurones for the facial nerve (CN VII) have a contralateral innervation. This only affects the muscles in the lower quadrant of the face – below the eyes.
Upper motor neurons for the hypoglossal (CN XII) nerve only provide contralateral innervation.
Where is the olfactory mucosa?
It is located in the roof of the nasal cavity and is composed of pseudostratified columnar epithelium which contains a number of cells.
What do basal cells do?
Form the new stem cells from which the new olfactory cells can develop.
What are sustentacular cells?
Tall cells for structural support. These are analogous to the glial cells located in the CNS.
What is the structure of olfactory receptor cells?
Bipolar neurons which have two processes, a dendritic process and a central process. The dendritic process projects to the surface of the epithelium, where they project a number of short cilia, the olfactory hairs, into the mucous membrane. These cilia react to odors in the air and stimulate the olfactory cells. The central process (also known as the axon) projects in the opposite direction through the basement membrane.
What do Bowman’s glands do and where are they?
Bowman’s glands present in the olfactory mucosa, which secrete mucus.
Where is the olfactory bulb?
Once in the cranial cavity, the olfactory fibres enter the olfactory bulb, which lies in the olfactory groove, within the anterior cranial fossa.
What is the olfactory bulb?
The olfactory bulb is an ovoid structure which contains specialised neurones, called mitral cells. The olfactory nerve fibres synapse with the mitral cells, forming collections known as synaptic glomeruli.
What is the optic nerve formed from?
The optic nerve is formed by the convergence of axons from the retinal ganglion cells. These cells in turn receive impulses from the photoreceptors of the eye (the rods and cones).
How does the optic nerve enter the skull?
After its formation, the nerve leaves the bony orbit via the optic canal, a passageway through the sphenoid bone. It enters the cranial cavity, running along the surface of the middle cranial fossa (in close proximity to the pituitary gland).
Which areas of vision do the optic tracts contain?
Left optic tract – contains fibres from the left temporal (lateral) retina, and the right nasal (medial) retina.
Right optic tract – contains fibres from the right temporal retina, and the left nasal retina.
Where do the optic tracts go to?
Each optic tract travels to its corresponding cerebral hemisphere to reach the Lateral Geniculate Nucleus (LGN), a relay system located in the thalamus; the fibres synapse here.
What does the superior branch of the occulomotor nerve supply?
Motor innervation to the superior rectus and levator palpabrae superioris. Sympathetic fibres run with the superior branch to innervate the superior tarsal muscle.
What does the inferior branch of the oculomotor nerve supply?
Motor innervation to the inferior rectus, medial rectus and inferior oblique. Parasympathetic fibres to the ciliary ganglion, which ultimately innervates the sphincter pupillae and ciliary muscles.
What is the innervation of the ciliary muscles and what do they do?
Oculomotor nerve. Contracts, causes the lens to become more spherical, and thus more adapted to short range vision.
