Brain Flashcards
3 Major Locations for Brain Herniation
1) Cingulate gyrus herniation: the cingulated gyrus herniates medially beneath the falx cerebri
2) Uncal herniation: the medial temporal lobe herniates below the free edge of the tentorium
*can compress the midbrain and CN III resulting in a dilated pupil (ipsilateral)
*can compress the posterior cerebral artery which leads to infarction of that territory
*downward displacement of the midbrain and pons can lead to tearing of penetrating arteries and veins leading to Duret hemorrhages, flame shaped hemorrhages in the gray matter of the pons
3) Cerebellar tonsils: herniation of cerebellar tonsils into the foramen magnum, may be fatal when respiratory centers in the medulla are compressed
Amygdala
•nucleus at the anterior end of hippocampus
Arachnoid mater
- middle meninges
- neural crest mesoectoderm
- linked by tight junctions, forming a blood-CSF barrier
Arachnoid Villi
- protrusions of the arachnoid through the dura and into the sinuses
- enables CSF to drain from the subarachnoid space into the venous system
- bulk flow process - when the pressure in the subarachnoid space is greater than venous pressure (as is normally the case) CSF moves across the villi into the sinus
Basal ganglia
•masses of gray matter buried inside the cerebral hemispheres •lenticular and caudate nuclei (also some diencephalic and brainstem structures) •nuclear accumbens + olfactory tubercle = ventral striatum •caudate nucleus + putamen = dorsal striatum •dorsal striatum + ventral striatum = striatum •pallidum •motor functions - muscle tone, involuntary movements, initiating and stopping movement
Blood Brain Barrier
- tight junctions of arachnoid membrane
- choroid epithelial cells
- endothelial cells of blood vessels
Brainstem
•midbrain, pons, medulla •CN III-XII attach here (XI exits the cervical spinal cord) - brainstem processes their incoming info and sends it on to the thalamus, cranial nerve reflexes, motor commands out through CN •spinothalmic and corticospinal tracts traverse the brainstem - long tract functions of the brainstem •multiple collections of brainstem neutrons with widespread, diffuse connections (Ascending Reticular Activating System) - regulate our state of consciousness and are central to the sleep wake cycle
Calcarine Sulcus
- runs roughly horizontally through the occipital lobe
- primary visual cortex lives here
Caudate Nucleus
•The caudate nucleus is one of the structures that make up the corpus striatum, which is a component of the basal ganglia. While the caudate nucleus has long been associated with motor processes due to its role in Parkinson’s disease, it plays important roles in various other nonmotor functions as well, including procedural learning,associative learning[5] and inhibitory control of action,among other functions. The caudate is also one of the brain structures which compose the reward system and functions as part of the cortico–basal ganglia–thalamic loop.[1]
Central sulcus
•divides parietal and frontal lobes
Centrum Semiovale
- The centrum semiovale, semioval center or centrum ovale is the central area of white matter found underneath the cerebral cortex. The white matter, located in each hemisphere between the cerebral cortex and nuclei, as a whole has a semioval shape.
- The white matter, located in each hemisphere between the cerebral cortex and nuclei, as a whole has a semioval shape. It consists of cortical projection fibers, association fibers and cortical fibers. It continues ventrally as the corona radiata.
Cephalic flexure
•80º bend between the brainstem and the diencephalon
Cerebellum
- inferior and posterior to the forebrain
- receives huge amounts of sensory information, but is NOT part of the sensory system - lesions do not cause sensory deficits
- designs movements and adjusts movements once they have begun - lesions cause movement disorders (rate, range, force of motion - ataxic)
- tethered to the back of the pons by three cerbellar peduncles
- two large hemispheres, continuous across the midline through a narrow strip called the vermis
Cerebral Aqueduct
- connects 3rd ventricle and 4th ventricle
- passes through midbrain
Cerebral cortex
•covers the surface of the cerebral hemispheres •involved in perception, initiation of voluntary movements and in everything we think of as “higher function”
Cerebral hemispheres
•cerebral cortex, basal ganglia, subcortical limbic system
Choroid Plexus
- produces CSF
- specialized structure derived from pial capillaries and modified ependymal cells
- responsbile for secretion of CSF through active transport across the choroid epithelium
- choroid plexus is composed of thin walled, leaky capillaries, a thin CT layer, and a single layer of simple cuboidal cells (modified ependymal cells) connected by tight junctions and modified for secretion - the blood brain barrier in the choroid plexus is at the level of the epithelium
Communicating Hydrocephalus
•obstruction after CSF exits the ventricles (such as blockade of the arachnoid villi)
Corpus Callosum
- along with the anterior commissure interconnect most areas of the cerebral cortex
- splenium, body, rostrum
CSF
- cerebrospinal fluid, much like plasma but with less protein
- produced at a steady rate by the choroid plexus - because of this, anything that blocks the pathway resultsin hydrocephalus
- fill ventricles and percolate through brain parenchyma - pours out of three holes in the ventricular walls of the brainstem filling the spaces outside the CNS as well
- choroid plexus —> ventricular system —> out the brainstem apertures —> down around the spinal cord as well as up towards the arachnoid granulation and out into the superior sinus systems and eventually out the venous system
- partial flotation of the brain, indrectly regulates the brain’s extracellular fluid, route of distribution of neuroactive substances produced by nerve cells, and a spatial buffer - moving in and out of the cranial cavity to make room for arterial pulses
Diencephalon
•thalamus - major relay station through which nearly all specific information reaches the cerebral cortex: sensory, outputs from basal ganglia (not olfactory system - bulb reaches cortex directly) •hypothalamus - major control center for ANS, drive related behaviour (hunger, thirst, temperature regulation, neuroendocrine control etc…)
Dura mater
•outermost layer of meninges
Dural Sinuses
- where the dua doubles upon itself, dural sinuses are formed
- thin walled, endothelium lined venous channels within the dura that can be found at several locations within the CNS
- cerebral veins empty into the dural sinuses
- superior saggital sinus - along the attached edge of the falx cerebri
- straight sinus - along the falx/tentorium line of attachment
- transverse sinuses - (left and right) along the attached edge of the tentorium cerebelli
- sigmoid sinuses - (left and right) continuation of each transverse sinus after it leaves the tentorium
- confluence of the sinuses - junction of the superior, saggital, staright and both transverse sinuses
Falx Cerebri
•dural reflection located between the cerebral hemispheres
Forebrain
•accounts for most of the CNS •cerebral hemispheres and diencephalon
Fornix
• major output bundle from the hippocampus, curves dow towards the hypothalamus
Frontal lobe
- movement
- personality, insight, foresight
- divided into superior, medial and inferior lobes
- precentral gyrus located just anterior to the central sulcus
- inferior surface orbital gyri - orbitofrontal cortex
Globus Pallidus
•The globus pallidus is a structure in the brain involved in the regulation of voluntary movement. It is part of the basal ganglia, which, among many other things, regulate movements that occur on the subconscious level.
Grey matter
•areas where cell bodies, dendrites, synapses are concentrated •discrete collection of cell bodies within CNS = nucleus •discrete collection of cell bodies within PNS = ganglion •grey matter covering part of the CNS surface = cortex •masses of grey matter within cerebral hemispheres = basal ganglia
Gyrus Rectus
The portion of the inferior frontal lobe immediately adjacent to the longitudinal fissure (and medial to the medial orbital gyrus and olfactory tract) is named the straight gyrus,(or gyrus rectus) and is continuous with the superior frontal gyrus on the medial surface.
A specific function for the straight gyrus has not yet been brought to light; however, in males, greater activation of the straight gyrus within the medial orbitofrontal cortex while observing sexually visual pictures has been strongly linked to HSDD (hypoactive sexual desire disorder).[
Hippocampus
•differently structured cerebral cortex rolled into the temporal lobe •nucleus at its anterior end = amygdala •interconnected with limbic lobe and are prominent parts of the limbic system •drives, emotions, memory
Hydrocephalus Ex Vacuo
- dilation of the ventricles secondary to loss of brain parenchyma
- commonly occurs in Alzheimer’s disease when there has been a significant amount of brain atrophy
Hypothalamus
•The hypothalamus is a small region of the brain. It’s located at the base of the brain, near the pituitary gland. While it’s very small, the hypothalamus plays a crucial role in many important functions, including: releasing hormones. regulating body temperature.
Insula
- big expanse of cortx below lateral sulcus
- plays a significant role in pain perception, social engagement, empathy, emotions, and numerous other vital functions, it is far from the only brain region that contributes to these functions. Moreover, it must work with other brain regions—and other parts of the body—to properly function
Internal Capsule
•The internal capsule is a white matter structure situated in the inferomedial part of each cerebral hemisphere of the brain. It carries information past the basal ganglia, separating the caudate nucleus and the thalamus from the putamen and the globus pallidus.
interventricular foramen
•connects lateral ventricles and 3rd ventricle
Language functions
•spread over parts of the frontal, parietal and temporal lobes near the lateral sulcus •almost always the left hemisphere
Lateral sulcus
•divides frontal, temporal and parietal lobes
Limbic lobe
- drive related behaviour, emotions, some forms of memory
- The limbic lobe is an arc-shaped region of cortex on the medial surface of each cerebral hemisphere of the mammalian brain, consisting of parts of the frontal, parietal and temporal lobes.
- made up of the cigulate and parahippocampal gyri; the cigulkate gyrus curves above and behind the corpus callosum and continues into the parahippocampal gyrus which in turn ends on the uncus
Longitudinal fissure
•separates the cerebral hemispheres
Medulla
•continuous with the spinal cord
Midbrain
•mesencephalon (contiguous with the diencephalon)
Non Communicating Hydrocephalus
•obstruction of CSF somewhere within the ventricles
Nucleus Accumbens
- The most widely recognized function of the nucleus accumbens is its role in the “reward circuit” of the brain.
- The nucleus accumbens is found in an area of the brain called the basal forebrain. There is a nucleus accumbens in each hemisphere; it is situated between the caudate and putamen. The nucleus accumbens is considered part of the basal ganglia and also is the main component of the ventral striatum. The nucleus accumbens itself is separated into two anatomical components: the shell and the core. These two contiguous areas have overlapping connections, but may make different contributions to the functions of the nucleus accumbens.
Occipital lobe
- smallest, simplest
- vision
- calcarine sulcus
orbital gyri or orbitofrontal cortex
•The inferior or orbital surface of the frontal lobe is concave, and rests on the orbital plate of the frontal bone. It is divided into four orbital gyri by a well-marked H-shaped orbital sulcus. These are named, from their position, the medial, anterior, lateral, and posterior, orbital gyri. The medial orbital gyrus presents a well-marked antero-posterior sulcus, the olfactory sulcus, for the olfactory tract; the portion medial to this is named the straight gyrus, and is continuous with the superior frontal gyrus on the medial surface.
Parietal lobe
•somatic sensation, including some very complex aspects of orientation •directed attention
Parietoocciptal sulcus
•divides the occipital lobe and the parietal lobes
Pia mater
•innermost layer of meninges •adherent to brain and spinal cord
Pineal gland
•small endocrine gland •produces melatonin
Pituitary gland
•receives messages from the hypothalamus and produces hormones
Postcentral Gyrus
- parietal lobe, posterior to the central sulcus
- somatosensory cortex
precentral gyrus
- frontal lobe, anterior to the central sulcus
- contains the primary motor cortex
Putamen
•The putamen and caudate nucleus together form the dorsal striatum. It is also one of the structures that comprise the basal nuclei.
Septum Pellucidum
•medial wall of lateral ventricles
Subarachnoid Space
- between the arachnoid and pia
- filled with CSF
- contains large arteries and veins that supply the underlying brain
- where there are depressions in the brain surface, the subarachnoid space expands to form structures called cisterns
Subdural Hemorrhage
- tearing of bridging veins, which pass from the subarachnoid space on the surface of the brain and connect to the dural sinuses
- elderly individuals moe at risk
Temporal lobe
- location of auditory cortex
- higher order visual functions
- some parts of the medial temporal lobe (often considered separately as underlying part of the limbic lobe) play a role in learning and memory
- divided into superior, middle and inferior gyri along the anterior surface
- divided into parahippocampal, occipitotemporal and inferior gyri along the inferior surface
- uncus
Tentorium Cerebelli
•dural reflection between the cerebellum and cerbral hemispheres
Thalamus
•The thalamus is a small structure within the brain located just above the brain stem between the cerebral cortex and the midbrain and has extensive nerve connections to both. The main function of the thalamus is to relay motor and sensory signals to the cerebral cortex.
Uncus
- The uncus is an anterior extremity of the parahippocampal gyrus. It is separated from the apex of the temporal lobe by a slight fissure called the incisura temporalis.
- medially facing bump near the brainstem
- clinical significance because expanding masses can push teh uncus against the brainstem and cause major problems
- The part of the olfactory cortex that is on the temporal lobe covers the area of the uncus
Ventricles
- the CNS develops from an epithelial tube and the cavity of the tube persists as a continuous series of ventricles
- two lateral ventricles with a septum pellucidum forming its medial wall curves throuh each of the cerebral hemispheres and opens into a single, midline 3rd ventricle via the interventricular foramen
- the 3rd ventricle narrows into a cerbral aqueduct that passes through the midbrain and expands into a 4th ventricle that extends through the pons and half of the medulla
Vermis
•narrow strip between the two hemispheres of the cerebellum
White matter
•collections of myelinated axons •discrete collection of fibers = tract -two part name: where axons are —-> where they terminate •fasiculus, lemniscus, peduncle
Internal Carotid System
•supplies most of the cerberbral hemispheres, except for the medial surface of the occipital lobes and the medial/inferior surface of the temporal lobes
Vertebral/Basilar System
•supplies the meidal occipital lobes, medial/inferior temporal lobes, brainstem and most of the diencephalon
Posterior Communicating Artery
- preterminal branch of the Internal Carotid a.
- component of the Circle of Willis
Anterior Choroidal Artery
•travels along the optic tract and then slips into the inferior horn of the lateral ventricle to supply its choroid plexus
Middle Cerebral Artery
- terminal branch of Internal Carotid a.
- moves off laterally, reaches the insula, divides into a number of brnaches that emerge from the lateral sulcus and supply most of the lateral surface of the hemisphere
Anterior Cerebral Artery
- terminal branch of the Internal Carotid a.
- moves into longitudinal fissure and divides into branches that supply the orbital and medial surfaces of the frontal lobe and the medial surface of the parietal lobe
Basilar Artery
•the two vertebral arteries join to form BA
Anterior Spinal Artery
- preterminal branch of vertebral a.
- cephalic origin of the spinal cord’s arterial supply
Posterior Spinal Arteries
- preterminal branches of the Vertebral a.
- cephalic origin of the spinal cord’s arterial blood supply
Posterior Inferior Cerebral Artery (PICA)
- preterminal branch of the Vertebral a.
- reaches the posterior part of the cerebellum’s inferior surface, near the choroid plexus of the 4th ventricle and the PICA branches supply it as well
- lateral medulla
Posterior Cerebral Arteries
- bifurcation of the Basilar a.
- wrap around the rostral midbrain and sends its largest branches to the inferior/medial surface of the temporal lobe and the medial surface of the occipital lobe
Anterior Inferior Cerebellar Arteries (AICA)
- preterminal branch of the Basilar a.
- reach the anterior inferior cerebellum’s surface
Superior Cerebellar Arteries
- preterminal branch of the Basilar a.
- reach the part of the cerebellum that PICA and AICA miss (the superior surface)
- wraps around rostral pons and caudal midbrain and supplies them, too
Circle of Willis
•Anterior Cerebral a. and Posterior Cerebral . and Internal Carotid a. communicate through Anterior Communicating a. and Posterior Communicating a.
Venous Angle
•formed where the choroidal and terminal (thalmostriate) veins join at the interventricular foramen, male a hairpin turn and form the internal cerebral vein
Circumventricular Organs
- monitor composition of blood, dump something into theblood
- border on the ventricular system
- no BBB
- examples: pineal gland, parts of the hypothalamus, and the area postrema in the medulla
- in a way, so is the choroid plexus!
