Theme 1 – Brain and Body PDF
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Erasmus University Rotterdam
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This document outlines the major divisions of the brain, including the hindbrain, midbrain, and forebrain, and their subdivisions. It details the structures within each division and their functions, along with the organization of the nervous system, including the central and peripheral components. The document also explains afferent and efferent nerves and cranial nerves.
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Checklist Three major divisions of the brain: hindbrain, midbrain, forebrain The smaller subdivisions of these subdivisions Hindbrain: rhombencephalon Midbrain: mesencephalon Forebrain: prosencephalon, diencephalon, telencephalon...
Checklist Three major divisions of the brain: hindbrain, midbrain, forebrain The smaller subdivisions of these subdivisions Hindbrain: rhombencephalon Midbrain: mesencephalon Forebrain: prosencephalon, diencephalon, telencephalon Major structures of the subdivisions, location and function The division of the cerebral cortex into the temporal lobe, parietal lobe, frontal lobe and occipital lobe The binding problem Divisions of the nervous system Central Nervous System Brain Spinal cord Peripheral Nervous System Somatic nervous system Autonomic nervous system Sympathetic nervous system Parasympathetic nervous system Afferent and efferent nerves Cranial nerves general function and amount The blood-brain barrier Features of a neuron Types of neurons: interneurons, motor neurons, sensory neurons Neuroanatomical directions: dorsal, anterior, posterior, ventral, medial, lateral Planes of the brain: sagittal, horizontal, coronal Major divisions of the brain and their subdivisions ⭑ The telencephalon is on the top and the other four divisions are below it in alphabetical order. ◦ The telencephalon (cerebral hemispheres) undergoes the greatest growth during development. The other four divisions are referred to collectively as thebrain stem, the stem on which the telencephalon sits. Hindbrain (rhombencephalon) ◦ The hindbrain consists of the myelencephalon/medulla and the metencephalon. ◦ Themyelencephalon/medullacan be regarded as anenlarged extension of the spinal cord. ◦ The medulla controls breathing, heart rate and other vital functions through the cranial nerves. ◦ Themetencephalonis divided into the pons and thecerebellum. ◦Ponsis Latin for “bridge,” reflecting the factthat in the pons, axons from each half of the brain cross to the opposite side of the spinal cord so that the left hemisphere controls the muscles of the right side of the body and the right hemisphere controls the left side. ◦ Thecerebellumhas long been known for its contributions to the control of movement and many describe it as important for balance and coordination. ◦ It is an important sensorimotor structure; cerebellar damage eliminates the ability to precisely control one’s movements and to adapt them to changing conditions. ◦ However, the fact that cerebellar damage also produces a variety of cognitive deficits suggests that its functions are not restricted to sensorimotor control. Midbrain (mesencephalon) ◦ Themesencephalonhas two divisions: 1. Thetectumis the dorsal surface of the midbrain andis composed of two pairs of swelling: theinferior colliculihave an auditoryfunction and thesuperior colliculihave a visual-motor function, meaning theydirect the body’s orientation toward or away from particular visual stimuli. 2. In addition to the reticular formation, thetegmentumcontains three colourful structures. Theperiaqueductal greyis the grey mattersituated around the cerebral aqueduct. Thesubstantia nigragives riseto a dopamine-containing pathway that facilitates readiness for movement. Along with thered nucleus, it’s also an important part of the sensorimotor system. Forebrain (prosencephalon) ◦ Thediencephalonis composed of two structures. 1. Thethalamusis the two-lobed structure that’s part of the top of the brain stem and is the main source of input to the cerebral cortex. The two lobes are joined by themassa intermedia. ◦ Many nuclei of the thalamus receive input from and project to the cerebral cortex. ◦ Also involved in memory. 2. Thehypothalamusplays an important role in the regulation of motivated behaviours. It does so by regulating the release of hormones from thepituitary gland, which dangles from it. ◦ Theoptic chiasmis the point at which the optic nerves from each eye come together and then decussate(cross over to the other side of the brain). ◦ Thelimbic systemis a circuit of structures that circle the thalamus and isinvolved in the regulation of motivated behaviours (basic needs/survival). Major structures are: ◦ Thebasal gangliaare thecaudateandputamen, knowntogether as thestriatum. ◦ Their major output is to theglobus pallidus. ◦ The basal ganglia play a role in the performance of voluntary motor responses and decision making. A part of the basal ganglia is thenucleus accumbens, which is thought to play a role in the rewarding effects of addictive drugs. ◦ Thetelencephalon(cerebral hemispheres) is thelargest division. It’s involved in the most complex functions – it initiates voluntary movement, interprets sensory input and mediates complex cognitive processes like learning and problem solving. ◦ The cerebral hemispheres are covered by a layer of tissue called thecerebral cortex that’s mainly composed of grey matter (unmyelinated neurons). The layer beneath the cortex is mainly composed of white matter (myelinated neurons). ◦ Each hemisphere is organised to receive sensory information, mostly from the contralateral side of the body. ◦ The cerebral hemispheres are directly connected by a few tracts spanning the longitudinal fissure (the largest fissure) calledcerebral commissures, the largest of which is thecorpus callosum. The division of the cerebral cortex into four types of lobes ◦ Thecentral fissureand thelateral fissuredivideeach hemisphere into four lobes: the frontal lobe, the parietal lobe, the temporal lobe and the occipital lobe. ◦ Among the largest gyri are theprecentral gyri(frontallobe), thepostcentral gyri (parietal lobe) and thesuperior temporal gyri(temporallobe). ◦ Theoccipital lobeis the main target for visualinformation. ◦ Theparietal lobeprocesses sensations. Informationabout touch and body location is important not only for its own sake but also for interpreting visual and auditory information. The parietal lobe monitors the information about eye, head and body positions and passes it on to brain areas that control movement. ◦ Thetemporal lobecontributes to hearing, complexaspects of vision and processing of emotional information. Temporal lobe damage can lead to a set of behaviors known as theKlüver-Bucy syndrome, where the most commonsymptoms are inappropriate sexual behaviors, overeating and excessive lip-smacking or other mouth movements. ◦ Thefrontal lobeincludes the precentral gyrus, which controls fine movements. It also includes the prefrontal cortex, which is important for planning, aspects of memory and cognition and decision making. ◦ The area where the parietal lobe and the temporal lobe meet is thetemporoparietal junction. It serves multiple functions, includingattention, body awareness and social cognition. ◦ Several areas in the prefrontal cortex and the temporoparietal junction have come to be known as thedefault network. These are theareas that dominate activity when you don’t need to concentrate on anything in particular. Binding problem The question of how various brain areas produce a perception of a single object is known as the binding problem, or large-scale integration problem. Binding requires perceiving that two types of stimuli (such as sight and sound) occurred at the same place at the same time. Divisions of the nervous system ◦ Thecentral nervous system (CNS)is composed of the brain and the spinal cord. ◦ The spinal cord comprises two different areas:an inner H-shaped core of gray matter and a surrounding area of white matter. ◦ Gray matter is composed largely of cell bodies and unmyelinated interneurons, whereas white matter is composed largely of myelinated axons. (It is the myelin that gives the white matter its glossy white sheen.) ◦ Each segment of the spinal cord sends sensory information to the brain and receives motor commands from the brain. ◦ Theperipheral nervous system (PNS)connects thebrain and the spinal cord to the rest of the body and has two divisions: 1. Thesomatic nervous system (SNS)interacts with theexternal environment. It controlsvoluntarymuscles and is composed ofafferentnerves(signals from sensory organs → CNS) andefferent nerves(motor signalsfrom CNS → skeletal muscles). ⭑ afferent = approaching the CNS, efferent = exiting the CNS 2. Theautonomic nervous system (ANS)regulates the internalenvironment. It controlsinvoluntarymuscles and is composed of afferentnerves (sensory signals from internal organs → CNS) and efferent nerves (motor signals from CNS → internal organs). ◦ The ANS has two kinds of efferent nerves:sympatheticnervesand parasympathetic nerves. ◦ All sympathetic and parasympathetic nerves are two-stage neural paths – they project from the CNS and go only part of the way to the target organs before they synapse on second-stage neurons that carry the signals the rest of the way. ◦ There are three important principles of the functions of the sympathetic and parasympathetic nervous systems: 1. Sympathetic nervesexpendenergy in threatening situations, whereas parasympathetic nerves act toconserveenergy. 2. Each autonomic target organ receives opposing sympathetic and parasympathetic input, so its activity is controlled by relative levels of sympathetic and parasympathetic activity. 3. Sympathetic changes are indicative ofarousal, whereas parasympathetic changes are indicative ofrelaxation. ◦ Sympathetic and parasympathetic activities are usually the opposite of each other. ◦ A special part of the ANS is theenteric nervoussystem, which controls the digestive system. Meninges ◦ The CNS is protected by three membranes. In order of innermost to outermost: 1. Pia mater 2. Arachnoid membrane 3. Dura mater Cerebrospinal fluid ◦ The cerebrospinal fluid supports and cushions the brain. ◦ Occasionally, the flow of cerebrospinal fluid is blocked by a tumor. The resulting buildup in the ventricles causes the walls of the ventricles and thus the entire brain to expand, producing a condition called hydrocephalus. Cranial nerves general function and amount ◦ While most of the nerves of the PNS project from the spinal cord, the 12 pairs of cranial nervesproject from the brain. The head andthe organs connect to the medulla and adjacent areas by 12 pairs of cranial nerves. ◦ They’re involved in a variety of sensory and motor functions. ◦ The functions of the various cranial nerves are commonly assessed by neurologists as a basis for diagnosis. Because the functions and locations of the cranial nerves are specific, disruptions of particular cranial nerve functions provide excellent clues about the location and extent of tumors and other kinds of brain pathology. Blood-brain barrier ◦ Theblood-brain barrierprevents the passage ofmany toxic substances from the blood into the brain. Unlike the loosely packed cells that compose the walls of blood vessels in the rest of the body, those in the brain are tightly packed and form a barrier to large molecules, except those that are critical for brain function. ◦ Many CNS disorders are associated with impairment of the blood–brain barrier. Features of a neuron ◦Neuronsare cells in the nervous system that receiveinformation and transmit it to other cells. A. Dendrite – Collection of information from other neurons. B. Cell nucleus – Location of DNA (the genetic information). C. Cell body (soma) – Integration of incoming information and generation of outgoing signal to the axon. D. Axon – Passing the signal over long distances. E. Axon branches – Passing the signal in different directions. F. Presynaptic terminal – Here the signal is passed to the dendrites of other neurons or other cells. Types of neurons ◦ One way of classifying neurons is based on the number of processes (projections) emanating from their cell bodies. ◦ Most neurons aremultipolar(unipolar, bipolar), which means more than two ◦ processes extend from their cell bodies. ◦Interneuronshave a short axon or no axon at all. Their function is to integrate neural activity within a single brain structure, not to conduct signals from one structure to another. ◦ Amotor neuronreceives excitation through its dendrites and conducts impulses along its axon to a muscle. ◦ Asensory neuronis specialized at one end to behighly sensitive to a particular type of stimulation, such as touch. Neuroanatomical directions and planes of the brain Rostral and caudal are not in the checklist Summary of major brain structures
