Anatomy and Physiology Chapter 13 Notes

Anatomy and Physiology Chapter 13 Notes 13.1 – Brain Organization and Development Overview of Brain Anatomy  The brain is composed of 4 major regions: the cerebrum, diencephalon, brainstem, and cerebellum o The cerebellum is inferior to the cerebrum o The brainstem has three regions: the midbrain, pons, and medulla oblongata o The diencephalon is organized into the epithalamus, hypothalamus, and thalamus  The cerebrum is divided into two halves, called left and right hemispheres o Each hemisphere may be further subdivided into five functional areas called lobes  Our skull volume limits the size of our brain, so the outer brain tissue of the cerebrum is folded on itself so that more neurons can fit within the cranium o These folds are called gyri o The shallow depressions between those folds are called sulci and the deeper grooves are named fissures  Two directional terms are often used to describe relative positions of brain anatomy o Anterior = rostral o Posterior = caudal Development of Brain Divisions  The formation of nervous tissue begins in the embryo during the third week of development with a thickening of a portion of the ectoderm o This portion of the ectoderm specifically overlies the notochord, which is a tightly packed group of mesoderm cells positioned on the developing embryo midline  The thickened ectoderm is called the neural plate o The neural plate is induced by the underlying notochord to form a neural tube, which begins the process called neurulation  Steps of neurulation: o The neural plate develops a central longitudinal indentation called the neural groove o as this is happening, cells along the lateral margins of the neural plate proliferate, becoming the thickened neural folds o the tips of the neural folds form neural crest cells o the neural folds elevate and approach one another o the neural crest cells begin to pinch off from the neural folds and form other structures o by the end of the third week, the neural folds have met and fused at the midline as the neural groove starts to form a neural tube, which has an internal space called the neural canal  for a short time, the neural tube is open at both ends but close at the end of the fourth week  neuropores o the opening closest to the future head is the cranial neuropore (forms the brain), whereas the opening closest to the future buttock’s region is called the caudal neuropore (forms the spinal cord) Development of the Brain  the neural tube undergoes disproportionate growth rates in different regions o this growth has formed three primary brain vesicles by the late fourth week of development, which eventually give rise to all the different regions of the adult brain  the forebrain is called the prosencephalon o the midbrain is called the mesencephalon o the hindbrain is called the rhombencephalon for its rhombical shape  by the fifth week of development, the three primary vesicles further develop into a total of five secondary brain vesicles o the telencephalon arises from the prosencephalon and eventually forms the cerebrum o the diencephalon also derives from the prosencephalon and eventually forms the thalamus, hypothalamus, and epithalamus o the metencephalon arises from the rhombencephalon and eventually forms the pons and cerebellum o the myelencephalon also derives from the rhombencephalon and eventually forms the medulla oblongata o the mesencephalon is the only primary vesicle that does not form a new secondary vesicle and it becomes the midbrain Gray Matter and White Matter Distribution  the anatomic structure of gray matter within the CNS primarily derives its color from the cell bodies and dendrites of the neurons that compose it o the cortex, which is a superficial layer of gray matter, and the nucleus are both composed of gray matter o neural cell bodies, dendrites, and unmyelinated cells  the general function of each of the different regions of gray matter, in either the brain or the spinal cord, is to serve as an integrating and processing area o for example, the synapses within the gray matter allow for integration and processing to occur  the anatomic structure of white matter derives its color from the bundles of myelinated axons that compose it o divided into funiculi and white commissures  the general function of the bundles of axons forming the white matter, in either the brain or the spinal cord, is to relay nerve signals o white matter provides the means for information to be transmitted between different regions of the brain and spinal cord and between the brain and the body 13.2 – Protection and Support of the Brain the brain is both protected and isolated by multiple structures o the body cranium provides rigid support, while protective connective tissue membranes surround and partition portions of the brain o CSF acts as a cushioning fluid between specific layers of meninges o Blood-brain barrier Cranial Meninges  The cranial meninges are three connective tissue layers that separate and support the soft tissue of the brain from bones of the cranium, enclose and protect some of the blood vessels that supply the brain, and contain and help circulate cerebrospinal fluid  Pia mater is the innermost of the cranial meninges o It is a thin layer of delicate areolar connective tissue that tightly adheres to the brain and follows every contour of the brain surface  The arachnoid mater lies external to the pia mater o Partially composed of a delicate web of collagen and elastic fibers, termed the arachnoid trabeculae o Immediately deep to the arachnoid mater is the subarachnoid space, which contains CSF  The dura mater is the strongest of the meninges because of the two layers of dense irregular connective tissue o The meningeal layer is immediately superficial to the arachnoid o The periosteal layer, the more superficial layer, forms the periosteum of the internal surface of the cranial bones  o The meningeal layer is usually fused with the periosteal layer, except in specific areas where these two layers are separate and form large, blood-filled spaces called dural venous sinuses (drain the blood from the brain) o Two potential spaces are associated with the dura matter  the epidural space and the subdural space  The dura mater and the bones of the skull may be separated by the epidural space, which contains the arteries and veins that nourish the meninges and bones of the cranium o The subdural space is positioned between the arachnoid mater and the overlying dura mater Cranial Dural Septa  The double layers of dura mater are called cranial dural septa o These membranous partitions separate specific parts of the brain and provide additional stabilization and support to the brain  There are 4 cranial dural septa o The falx cerebri is the largest of the four dural septa  This large, sickle-shaped, vertical fold of dura mater is located in the midsagittal plane and projects into the longitudinal fissure between the left and right cerebral hemispheres  Located within the superior and inferior margins of this dural septum are tow dural venous sinuses: the superior sagittal sinus and the inferior sagittal sinus o the tentorium cerebelli is a horizontally oriented fold of dura mater that separates both the occipital and temporal lobes of the cerebrum from the cerebellum  the transverse sinuses are within its posterior border, whereas the straight sinus is within its midsagittal region  the anterior surface of the tentorium cerebelli has a gap, or opening, called the tentorial notch to allow for the passage of the brainstem o extending into the midsagittal line inferior to the tentorium cerebelli is the falx cerebelli, a sickle-shaped, vertical partition that divides the left and right cerebellar hemispheres  a tiny occipital sinus (another dural venous sinus) is within its posterior vertical border o the diaphragma sellae is the smallest of the dural septa and forms a roof over the sella turcica of the sphenoid bone Brain Ventricles  ventricles are cavities or expansions within the brain that are derived from the neural canal  all the four ventricles are lined with ependymal cells and contain CSF  two lateral ventricles are in the cerebrum, separated by a thin medial partition called the septum pellucidum  within the diencephalon is a smaller, thinner ventricle called the third ventricle o each lateral ventricle is connected with the third ventricle through an opening called the interventricular foramen  a narrow canal called the cerebral aqueduct passes through the midbrain and connects the third ventricle with the tetrahedron-shaped fourth ventricle o located between the pons, medulla oblongata, and cerebellum o the fourth ventricle narrows at its inferior end before it merges with the slender central canal of the spinal cord Cerebrospinal Fluid cerebrospinal fluid (CSF) is a clear, colorless liquid that circulates within the ventricles and subarachnoid space  CSF performs several important functions: o Buoyancy  the brain floats within the CSF, thereby reducing its apparent weight by more than 95% which prevents the brain from being crushed under its own weight o Protection  CSF provides a liquid cushion to protect delicate neural structures from sudden movements o Environmental stability  CSF transports chemical messengers to the brain and removes waste products from the brain, as well as protects nervous tissue from chemical fluctuations that would disrupt neuron function  Cerebrospinal fluid is initially formed by the choroid plexus, a region of specialized tissue in each ventricle o The choroid plexus is composed of a layer of ependymal cells and the blood capillaries that lie within the pia mater  Blood plasma is filtered from the blood capillaries across both he capillary wall and the pia mater, while its composition is modified by the ependymal cells o Fluid is then released into a ventricle and is now referred to as CSF o It then circulates through the ventricles, where additional fluid is added by ependymal cells o Once CSF enters the subarachnoid space, its volume increases with the addition of excess interstitial fluid from the brain  Reabsorption of CSF occurs at arachnoid villi which are fingerlike extensions of the arachnoid mater that project through the dura mater into the dural venous sinuses o A collection of arachnoid villi forms an arachnoid granulation which provides a one-way flow of excess CSF to be returned to the blood within the dural venous sinuses Blood-Brain Barrier  The brain is protected from the contents within the blood by the blood-brain barrier (BBB) which strictly regulates which substances can and cannot be filtered from the blood to enter the interstitial fluid of the brain  The BBB is formed of specialized capillaries surrounded by astrocytes  Capillaries forming the BBB exhibit three significant structural differences from other capillaries o The endothelial cells contain tight junctions, which prevent the passage of materials between cells o The capillary wall is made more substantial by a thickened basement membrane that further restricts the passage of substances from the blood into the brain o The capillaries forming the BBB are wrapped in the perivascular feet of astrocytes, which form the outermost portion of the BBB  13.3 – Cerebrum  The cerebrum is the location of conscious thought processes and the origin of all complex intellectual functions o The functional activities in your cerebrum enable you to read and comprehend the words in this textbook, turn pages, form and remember ideas, and talk about what you’ve learned with your peers o It is the center of your intelligence, responding, reasoning, thought, memory, and judgement, as well as your voluntary control of skeletal muscle movement and conscious perception of your senses  The cerebral cortex is the surface layer of gray matter of the cerebrum and the cerebral nuclei are the internal, deep gray matter within the cerebrum o Gray matter functions as centers of integration and processing Cerebral Hemispheres  The cerebrum is composed of two halves, called the left and right cerebral hemispheres o The paired cerebral hemispheres are separated by a narrow, deep cleft called the longitudinal fissure, which extends along the midsagittal plane  The cerebral hemispheres are separate from one another, except at a few locations where bundles of axons called tracts form white matter regions that allow for communication between them o Largest of these is the corpus callosum which connects the hemispheres  Both cerebral hemispheres receive their sensory information from, and project motor commands to, the opposite side of the body Lobes of the Cerebrum  The frontal lobe lies deep to the frontal bone and forms the anterior part of the cerebral hemispheres o The frontal love ends posteriorly at a deep groove called the central sulcus that marks its boundary with the parietal lobe o The inferior border of the frontal lobe is marked by the lateral sulcus, a deep groove that separates the frontal and parietal lobes from the temporal lobe o The precentral gyrus, is the mass of nervous tissue immediately anterior to the central sulcus o Controls voluntary motor functions, concentration, verbal communication, decision making, planning, and personality  The parietal lobe lies deep to the parietal bone and forms the superoposterior part of each cerebral hemisphere o It terminates anteriorly at the central sulcus, posteriorly at a relatively indistinct parieto-occipital sulcus, and laterally at the lateral sulcus o An important anatomic feature of this lobe is the postcentral gyrus, which is the mass of nervous tissue immediately posterior to the central sulcus o Involved with general sensory functions, such as the shape and texture of objects  The temporal lobe lies internal to the temporal bone and inferior to the lateral sulcus o Involved with hearing and smell  The occipital lobe lies internal to the occipital bone and forms the posterior region of each hemisphere o Responsible for processing incoming visual information and storing visual memories The insula is a small lobe deep to the lateral sulcus o Involved in memory and the interpretation of taste (gustation) Functional areas of the Cerebrum  The central sulcus serves as an anatomic landmark that separates motor functions that are controlled by the frontal lobe, and sensory input that is relayed to the parietal lobe, occipital lobe, and temporal lobe, as well as the internal insula Motor Areas  The primary motor cortex, also called the somatic motor area, is specifically located within the precentral gyrus of the frontal lobe  The left primary motor cortex controls the skeletal muscles on the right side of the body and the right primary motor cortex controls the skeletal muscles on the left side of the body  The distribution of the primary motor cortex innervation to various body parts can be diagrammed as a motor homunculus on the precentral gyrus o The distorted proportions of the homunculus body reflect the amount of cortex dedicated to the motor activity of each body part  The motor speech area is located in most individuals within the inferolateral portion of the left frontal lobe o This region is responsible for regulating the breathing and controlling the muscular movements necessary for vocalization  The frontal eye field is within the frontal lobe immediately superior to the motor speech area o This area controls and regulates eye movements needed for reading and coordinating binocular vision  The primary motor cortical regions are connected to adjacent association areas that coordinate discrete skeletal muscle movement o The premotor cortex also is called the somatic motor association area, and it is located within the frontal lobe immediately anterior to the precentral gyrus o Responsible for coordinating learned, skilled motor activities Sensory Areas  The primary somatosensory cortex is housed within the postcentral gyrus of the parietal lobes o Neurons receive sensory information regarding touch, pressure, pain, and temperature o Typically, conscious of the sensations received by this cortex  A sensory homunculus may be traced on the postcentral gyrus surface o The surface area of somatosensory cortex devoted to a body region indicates the amount of sensory information collected within that region  The somatosensory association area is located within the parietal lobe and lies immediately posterior to the primary somatosensory cortex o Integrates sensory information and interprets sensations to determine the texture, temperature, pressure, and shape of objects o Allows us to identify known objects without seeing them  The primary visual cortex is located within the occipital lobe, where it receives and processes incoming visual information  The visual association area is located within the occipital lobe and it surrounds the primary visual area o Enables us to process visual information by analyzing color, movement, and form and to use this information to identify the things we see  The primary auditory cortex is located within the temporal lobe, where it receives and processes auditory information o The auditory association area is located within the temporal lobe, posteroinferior to the primary auditory cortex where it interprets the characteristics of sound and store memories of sounds heard in the past  The primary olfactory cortex is also located within the temporal lobe and provides conscious awareness of smells  The primary gustatory cortex is within the insula and is involved in processing taste information Functional Brain Regions  A functional brain region acts as a multi-association area between lobes for integrating information from individual association areas  One functional brain region is the prefrontal cortex, located in the most anterior portions of the frontal lobes o Associated with many higher intellectual functions such as complex thought, judgement, expression of personality, planning future behaviors, and decision making o Also, will evaluate potential consequences of one’s actions  Another functional brain region is the Wernicke area, which is typically located within the left hemisphere o Involved in recognizing, understanding, and comprehending spoken or written language o The Wernicke area and the motor speech area must work together for fluent communication to occur Central White Matter  The central white matter of the cerebrum lies deep to the gray matter of the cerebral cortex o Composed primarily of myelinated axons, grouped into bundles called tracts o These are classified as association tracts, commissural tracts, or projection tracts  Association tracts connect different regions of the cerebral cortex within the same hemisphere o short association tracts are composed of arcuate fibers which connect neighboring gyri within the same lobe o the longer association tracts, called the longitudinal fasciculi, connect gyri in different lobes of the same hemisphere  commissural tracts extend between the cerebral hemispheres through axonal bridges called commissures   o the prominent commissural tracts that link the left and right cerebral hemispheres include the large, C-shaped corpus callosum and the smaller anterior posterior commissure projection tracts link the cerebral cortex to both the inferior brain regions and the spinal cord o the packed group of axons in these tracts passing in between the cerebral nuclei and the gray matter of the thalamus is called the internal capsule Cerebral Lateralization  humans tend to have shape asymmetries of the frontal and occipital lobes of the brain, called petalias o right-handed individuals typically have right frontal petalias, meaning that the right frontal lobe projects farther than the left frontal lobe  the hemispheres also differ with respect to some of their functions o each hemisphere tends to be specialized for certain tasks, a phenomenon called cerebral lateralization  in most people, the left hemisphere is the categorical hemisphere o it usually contains the Wernicke area and the motor speech area o specialized for language abilities and is important in performing sequential and analytical reasoning tasks, such as those required in science and mathematics  the other hemisphere is called the representational hemisphere, because it is concerned with visuospatial relationships and analyses o it is the seat of imagination and insight, musical and artistic skill, perception of patterns and spatial relationships, and comparison of sights, sounds, smells, and tastes  some aspects of lateralization differ between the sexes o women have a thicker posterior part of the corpus callosum due to the additional commissural axons in this region o adult males typically exhibit more lateralization than females and suffer more functional loss when one hemisphere is damaged  right-handed individuals tend to have a slightly different lateralization pattern than those who are left-handed  o a thicker corpus callosum in left-handers suggests that more signals may be relayed between their hemispheres the left hemisphere is the speech-dominant hemisphere o it controls speech in almost all right-handed people as well as in many lefthanded ones Cerebral Nuclei  the cerebral nuclei are paired, irregular masses of gray matter buried deep within the central white matter in the basal region of the cerebral hemispheres, inferior to the floor of the lateral ventricle o generally, help regulate motor output initiated by the cerebral cortex, to help inhibit unwanted movements  cerebral nuclei have multiple components, and each component has its own specific functions related to the overall function of the cerebral nuclei o the C-shaped caudate nucleus has an enlarged head and a slender, arching tail that parallels the curve of the lateral ventricle o the lentiform nucleus is a compact, triangular mass, made up of both the putamen and globus pallidus, two masses of gray matter positioned between the insula lobe of the cerebrum and the lateral wall of the thalamus  the putamen functions in controlling skeletal muscular movement at the subconscious level  the globus pallidus both excites and inhibits the activities of the thalamus to regulate skeletal muscle tone o the claustrum is a thin sliver of gray matter formed by a layer of neurons located immediately internal to the insula and processes visual information at a subconscious level o the amygdaloid body is an expanded region at the tail of the caudate nucleus and participates in the expression of emotions, control of behavioral activities, and development of moods  the term corpus striatum describes the striated appearance of the white matter of the internal capsule positioned between the gray matter of eh caudate nucleus and the lentiform nucleus 13.4 – Diencephalon the diencephalon is sandwiched between the inferior regions of the cerebral hemispheres and for this reason is often referred to as the “in-between brain” Epithalamus  the epithalamus partially forms the posterior roof of the diencephalon and covers the third ventricle o the posterior portion of the epithalamus houses the pineal gland and the habenular nuclei  the pineal gland is an endocrine gland that secretes melatonin, which appears to help regulate day-night cycles known as the body’s circadian rhythm  the habenular nuclei relay signals form the limbic system to the midbrain and are involved in visceral and emotional responses to odors Thalamus  the thalamus forms the superolateral walls of the third ventricle and its paired oval masses of gray matter that lie on either side of the third ventricle  the interthalamic adhesion is a small, midline mass of gray matter that connects the right and left thalamic bodies  each part of the thalamus has about a dozen major thalamic nuclei that are organized into groups  the thalamus is the principal and final relay point for incoming sensory information that is processed and then projected to the appropriate lobe of the cerebral cortex Hypothalamus  the hypothalamus is the anteroinferior region of the diencephalon o a thin, starlike infundibulum extends inferiorly from the hypothalamus to attach to the pituitary gland  the hypothalamus has numerous functions controlled by specific nuclei: o master control of the autonomic nervous system  it projects descending axons to autonomic nuclei in the brainstem that influence heart rate, blood pressure, digestive activities, and respiration o master control of the endocrine system  the hypothalamus secretes hormones that control secretory activities in the anterior pituitary gland, and it produces both antidiuretic hormone and oxytocin o regulating of body temperature  controls the mechanisms that heat and cool the body o control of food intake  neurons within the ventromedial nucleus monitor levels of nutrients such as glucose and amino acids in the blood and produce sensations of hunger o control of water intake  when the hypothalamus detects dehydration from the blood, our sensation of thirst is stimulated o regulation of sleep-wake rhythms  the suprachiasmic nucleus directs the pineal gland of the epithalamus to secrete melatonin at certain times of the day o control of emotional behavior  controls emotional responses such as pleasure, aggression, fear, rage, contentment, and sex drive  13.5 – Brainstem  the brainstem connects the cerebrum, diencephalon, and cerebellum to the spinal cord o the brainstem is a bidirectional passageway for all tracts extending between the major regions of the brain and the spinal cord Midbrain  the midbrain is the superior portion of the brainstem  cerebral peduncles are motor tracts located on the anterolateral surfaces of the midbrain o they relay voluntary motor commands from the primary motor cortex of each cerebral hemisphere  the superior cerebellar peduncles connect the midbrain to the cerebellum o bands of myelinated sensory axons composing a medial lemniscus extend from the medulla oblongata, through the pons and midbrain to the thalamus  the substantia nigra consists of bilaterally symmetric nuclei within the midbrain o it houses clusters of neurons that produce the neurotransmitter dopamine, which affects brain processes to control movement, emotional response, and ability to experience pleasure and pain  the tegmentum is sandwiched between the nuclei of the substantia nigra and the periaqueductal gray matter o contains the pigmented red nuclei and the reticular formation o the red color is due to blood vessel density and iron pigmentation o integrates information from the cerebrum and the cerebellum and issues involuntary motor commands to the erector spinae muscles of the back to help maintain posture  extending through the midbrain is the cerebral aqueduct connecting the third and fourth ventricles o surrounded by the region called the periaqueductal gray matter  the tectum is the most posterior region of the midbrain o it contains two pairs of sensory nuclei called the tectal plate that relay stations in the processing pathway of visual and auditory sensory input o the superior colliculi are the superior nuclei  they help visually track moving objects and control reflexes such as turning the eyes and head in response to a visual stimulus o the paired inferior colliculi control reflexive turning of the head and eyes in the direction of a sound Pons      the pons is a bulging region on the anterior part of the brainstem the middle cerebellar peduncles are transverse axons that connect the pons to the cerebellum the pons houses autonomic nuclei in the pontine respiratory center which regulates the skeletal muscles of breathing in and breathing out the superior olivary nuclei are located in the inferior portion of the pons and they receive auditory input (sounds localization) also houses sensory and motor cranial nerve nuclei for the trigeminal, abducens, and facial nerves Medulla Oblongata  the medulla oblongata is often simply called the medulla       o it is the most inferior part of the brainstem and is continuous with the spinal cord inferiorly o all communication between the brain and spinal cord involves tracts that ascend through the medulla oblongata the anterior surface exhibits two longitudinal ridges called the pyramids, which house the motor projection tracts called the pyramidal tracts that extend through the medulla o cross at points called the decussation of the pyramids  each cerebral hemisphere controls the voluntary movements of the opposite side of the body immediately lateral to each pyramid is a distinct bulge, called the olive, which contains a large fold of gray matter called the inferior olivary nucleus o relay ascending sensory nerve signals paired inferior cerebellar peduncles are tracts that connect the medulla oblongata to the cerebellum the most important autonomic centers in the medulla oblongata and their functions include: o the cardiovascular center, composed of both the cardiac center, which regulates both the heart’s rate and its force of contraction to alter cardiac output, and the vasomotor center, which controls the contraction and relaxation of smooth muscle within the walls of the smallest arteries (BP) o the medullary respiratory center, which regulates the respiratory rate  rhythmically initiate nerve signals that cause contraction of breathing muscles contains the vestibulocochlear, glossopharyngeal, vagus, accessory, and hypoglossal cranial nerves also contains the nucleus cuneatus and the nucleus gracilis, which relay somatic sensory information to the thalamus 13.6 – Cerebellum the cerebellum is the second largest part of the brain o it coordinates fine control over skeletal muscle actions and stores memories of movement patterns Structural Components of the Cerebellum  the cerebellum is composed of left and right cerebellar hemispheres o each hemisphere consists of two lobes, the anterior lobe and the posterior lobe, which are separated by the primary fissure  a narrow band of nervous tissue known as the vermis lies along the midline between the left and right cerebellar lobes o the cerebellar hemispheres and vermis have surface folds called folia  the cerebellum is partitioned internally into three regions o an outer gray matter called the cerebellar cortex o an internal region of white matter called the arbor vitae o the deepest gray matter layer that is composed of cerebellar nuclei Functions of the Cerebellum  it coordinates and fine-tunes skeletal muscle movements that were initiated by the cerebrum, and it ensures that skeletal muscle contraction follows the correct pattern     o this leads to smooth, coordinated movements the cerebellum stores memories of previously learned movement patterns o the cerebrum initiates the movement and sends a “rough draft” of the movement to the cerebellum, which then coordinates and adjusts it maintains equilibrium and posture by receiving proprioceptive information from the muscles and joints and uses this information to regulate the body’s position the cerebellum unconsciously perceives the position of the body, and when the cerebellum detects a disparity between the intended and actual movement, it may generate error-correcting nerve signals 13.7 – Functional Brain Systems     the limbic system is composed of multiple cerebral and diencephalic structures that collectively process and experience emotions the structures of the limbic system form a ring or border around the diencephalon o the cingulate gyrus is an internal mass of cerebral cortex located within the longitudinal fissure and superior to the corpus callosum o the parahippocampal gyrus is a mass of cerebral cortical tissue in the temporal lobe o the hippocampus connects to the diencephalon via the fornix  essential is storing memories and forming long-term memory o the amygdaloid body connects to the hippocampus  helps store and code memories based on how a person emotionally perceives them o the olfactory bulbs, olfactory tracts, and olfactory cortex experience how a particular odor can provoke certain emotions or be associated with certain memories o the fornix is a thin tract of white matter that connects the hippocampus with limbic structures of the diencephalon expression of our emotions is interpreted by our limbic system, but ultimately is controlled by the prefrontal cortex o decides the appropriate way to show our feelings if specific regions of either of these structures are damaged or artificially stimulated, we exhibit either deadened or exaggerated expressions of aggression, affection, anger, fear, love, pain, pleasure, or sexuality