Colloq V CNS Script Aurora Killi PDF

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EnchantingPeach

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Riga Stradiņš University

2022

Aurora Killi

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central nervous system motor control spinal cord anatomy

Summary

This document contains notes on the Central Nervous System, focusing on the motor hierarchy, spinal cord anatomy and function, and consequences of spinal shock. It outlines the levels of motor control, functions of the spinal cord, and reflexes organized within it. The document clearly defines levels of motor control, conductive functions of the spinal cord, and reflex mechanisms.

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Aurora Killi 25.03.22 Central nervous system Motor hierarchy. Levels of motor control; their functions...............

Aurora Killi 25.03.22 Central nervous system Motor hierarchy. Levels of motor control; their functions.................................................................................................................. 2 Functional anatomy of the spinal cord. Functions of the spinal cord.................................................................................................. 3 Early and late consequences of the spinal shock................................................................................................................................. 5 Functions of the medullary region and pons. Reflexes that are organized through this region....................................................... 10 Functions of midbrain......................................................................................................................................................................... 12 Functions of cerebellum. Afferent information that comes to the cerebellum, its function. Functional organization of cells in the cerebellum.......................................................................................................................................................................................... 14 Functional parts of cerebellum; their functions. Consequences of the damage of cerebellum....................................................... 18 Functions of the hypothalamus.......................................................................................................................................................... 22 Functions of thalamus; functional groups of nuclei and their functions........................................................................................... 23 1 Aurora Killi 25.03.22 Motor hierarchy. Levels of motor control; their functions Motor hierarchy Centers in the central nervous system are arranged into three levels according to their input in the regulation of our movement 1. Secondary and tertiary cortical areas → generate general plan of movement Highest level of motor hierarchy Responsible for o Memory o Analyzation of sensory information o Planning and programming of our movements Secondary and tertiary cortical areas generate general plan of movement Example o If there is an apple on the kitchen table, secondary and tertiary cortical areas decide if you should take it or not o According to receptors inside the body and information about what we see, these areas decide 2. Primary cortical areas and subcortical areas → split general plan into several programs Information from the highest level is sent to the middle level Middle level includes primary cortical areas and subcortical centers (basal ganglia, brainstem nuclei, cerebellum) These centers split the general plan of movement into several programs Primary cortical area o Triggers voluntary movement o Sends information to motor neurons to cause contraction of skeletal muscles Subcortical centers o Regulate the movement and make it precise and smooth without tremors or additional movements o Control equilibrium of the body according to the movement to prevent us from falling 3. Lower motor neurons in spinal cord → make movement possible When the middle level has elaborated on the common plan impulses are sent to the lowest center Lowest center consists of lower motor neurons (generally α motor neurons) o Most neurons are located in the spinal cord → innervates extremities and trunk o Some motor neurons are located in the brain stem → innervates facial and eye muscles Send impulses to skeletal muscles and activate them in the order that was decided by the highest centers. Makes the movement possible They only send impulses to skeletal muscles if they receive impulses from a higher level Interreaction between levels Information from the skeletal muscles, lower motor neurons, and other receptors (touch, pressure, pain, visual, hearing) is sent back to the middle and highest level of motor hierarchy In such a way, the higher centers can adjust the plan or make a new plan of movement if something has changed so they can adjust the plan or make a new plan of movement if something has changed. 2 Aurora Killi 25.03.22 Functional anatomy of the spinal cord. Functions of the spinal cord Functional anatomy of the spinal cord Lowest center of motor hierarchy Consists of white matter that surrounds the grey matter o White matter o Made of nerve fibers o Make up conductive pathways that go up or down the white matter o Grey matter o Made of nerve cell bodies and synapses o 97% are interneurons cell bodies o 3% are efferent neuron cell bodies o Afferent neurons are not found inside the spinal cord Afferent nerve fibers are located in the spinal ganglion of the dorsal root Dorsal root contains afferent nerve fibers → bring information into spinal cord Anterior root contains efferent nerve fibers → bring information out of spinal cord Functions of the spinal cord Conductive function → related to the conductive pathways Reflex function → related to the reflexes organized through the spinal cord Conductive function Related with the pathways that make up the white matter of the spinal cord. All conductive pathways are divided into two large groups Ascending pathways Begin from receptors in periphery Sensory pathways Sends information to the brain Majorly to thalamus and then further to the cerebral cortex for conscious sensation Spinothalamic pathways, dorsal column medial lemniscus system (proprioreceptors → brain) Descending pathways Pyramidal (corticospinal) Begin from brain, goes into Begin from primary motor area in precentral gyrus of cerebral cortex spinal cord, ends on Ends in the anterior motor neurons → skeletal muscles neurons in spinal cord Triggers voluntary movements Extrapyramidal Pyramidal pathways trigger Begin from sources outside the cerebral cortex (subcortical centers) the movement, but the o Tectospinal, reticulospinal, oligospinal, vestibulospinal pathways extrapyramidal pathways Bring information from subcortical centers to the spinal cord adjust and regulate it Regulate and adjust movements to make them precisely directed Reflex function Related to the reflexes that are organized through the neurons in the spinal cord Reflexes Function Stretch reflexes Triggered by stretch of skeletal muscles Muscle spindle (receptor) senses stretch and sends information to the spinal cord to cause contraction of the stretched muscle Two groups of reflexes o Phasic stretch reflex → stimulated by fast stretch and causes strong muscle contraction 3 Aurora Killi 25.03.22 o Tonic stretch reflex → stimulated by slow stretch due to gravity causes weak muscle contraction Reflexes form receptors in Triggered by stretch of muscle tendon tendons Tendon stretch is most commonly caused by very strong muscle contraction Golgi tendon organ senses stretch → relaxation of muscle whose tendon is excessively stretched Flexor reflexes Triggered by stimulation of pain receptors Nociceptive reflex Causes contraction of flexor muscles in extremity that receives nociceptive stimuli Crossed extensor reflex Realized by pain receptors from the other side Pain receptors stimulate extension of the opposite extremity to support the body Positive support reaction Triggered by pressure on palm or feet Causes extension of the extremity to provide support Can be observed when standing up from sitting position Rhythmic reflexes Triggers rhythmic activation and inhibition of muscle activity in extremities Necessary for walking, running, swimming etc. Provide rhythmic activities in extremities Autonomic reflexes Autonomic reflexes are realized through autonomic centers in the lateral horns of spinal cord T1-L3 → sympathetic centers which realizes sympathetic reflexes S2-4 → parasympathetic center which mainly realizes micturition and defecation reflex 4 Aurora Killi 25.03.22 Early and late consequences of the spinal shock Spinal shock Spinal shock is the consequence of high spinal cord transection Can be observed after spinal cord damage High = high level in cervical or The outcome generally depends on the level of transection place apoecthoracal segment of the o Above C5 → if transection is above the cervical 5th segment spinal cord level, the most common outcome is death Complete spinal cord transection = o Below C5 → if transection is below cervical 5th segment, the spinal cord is cut completely there is possibility for spinal shock to develop off the remaining spinal cord We most often speak about spinal shock after lower C 5 segments transection, but if the person survives after upper C 5 spinal cord damage, spinal shock develops as well Importance of C5 segment Spinal cord segments regulate respiratory system functions Respiration is performed by two groups of respiratory muscles o Diaphragm → major muscle that provides approx. 75% of the lung ventilation o External intercostal muscles → provide remaining 25% of volume change Respiratory muscles have no automaticity and are dependent on impulses from CNS o C3-4 → innervates diaphragm through the phrenic nerve o T segments → innervates external intercostal muscles according to their intercostal space Motor neurons in the spinal cord do not have automaticity either and are dependent on impulses from respiratory center in medullary region which sends impulses to o C3-4 segment to activate the phrenic nerve and stimulate contraction of diaphragm. o Thoracic segments to cause contraction of external intercostal muscles Damage below C5 Impulses cannot be sent to motor neurons located below C5 segment EIC muscles do not - External intercostal muscles do not receive impulses and stop functioning receive impulses, Impulses from the respiratory center can activate the phrenic nerve and diaphragm still cause contraction of + diaphragm receives impulses Since diaphragm is the major muscle of respiration → person can breathe and survives Damage above C5 Impulses form respiratory center cannot be sent to any of the motor neurons No respiratory that control respiratory muscles muscles receive Respiration is stopped and if artificial respiration is not started within 5 impulses minutes → irreversible brain neuron death begins Such spinal cord transections usually occur in situation in which we do not have time to start artificial ventilation early enough, so the most common outcome is death o In traffic accidents causing neck fracture o Jumping in shallow water with head forwards If person survives after such damage, the ability to ventilate lungs is lost forever since spinal cord neurons do not regenerate 5 Aurora Killi 25.03.22 Consequences of spinal shock There are two consequences depending on the time Immediate effect Full depression of spinal cord functions 1. If the spinal cord is cut, all nerve fibers coming from the brain into Neurons in the scheme the spinal cord are cut as well 1. Neuron in spinal cord 2. Neuron in the brain (controls 2. Since peripheral processes of brain neurons are cut, excitability of activity of spinal cord neuron) spinal cord neurons is lost 3. Sensory neuron (coming from 3. This causes immediate loss of all spinal cord functions below the receptors in the periphery, sends impulses to spinal cord neuron) transection site and at the level of transection Late effect (after 2 weeks-months) Excitability of neurons in spinal cord increases, and spinal cord becomes hyperexcitable 1. After 1-2 days → in the remaining functional synapses Neurotransmitter amount increases Number of receptors increases Spinal cord neurons activate a little bit more 2. Within several days and weeks → peripheral process of the transected brain neurons degenerates The remaining synapses in the spinal cord become hyperexcitable to compensate for the lost synapses This causes greater response in the periphery Signs of spinal shock Consequence Mechanism Anesthesia First sign that develops Anesthesia is the loss of conscious sensation Ascending pathways that bring information from receptors in periphery to cerebral cortex are cut Person loose conscious feeling of touch, pressure, pain, temperature, proprioception, and movement of extremities below the transection site Anesthesia remains for the rest of the life Paralysis Paralysis is the loss of conscious movements Happens due to damage of corticospinal tract Neurons in the brain cannot send impulses to lower motor neurons and stimulate conscious contraction of skeletal muscles Paralysis remains for the rest of the life Areflexia → hyperreflexia Areflexia Areflexia develops o Because of loss of spinal cord neuron excitability, all reflex realized immediately but turns into through the segments below and at level of transection are lost hyperreflexia after a while Hyperreflexia o After a while, reflexes below transection site return and become hyperactive o After some days → neurotransmitter amount and receptor number in synapses increases o After weeks or months → new synapses develop and can excite the spinal cord neuron upon stimulation of receptors in periphery 6 Aurora Killi 25.03.22 o Reflexes do not return at the level of transection because here α motor neurons are also lost Atonia → hypertonia Atonia → loss of skeletal muscle tone o Happens because reflexes that trigger muscle tone generation are not realized through the spinal cord Hypertonia o Tonic stretch reflex become hyperactive o Muscle tone is greater in muscles innervated by neurons below transection site o Hypertonia does not develop in muscles innervated by segment of transection Disappearance of Reflexes in the autonomic nervous system are also immediately lost autonomic reflex → (not only in the motor nervous system) return After a while, autonomic reflexes also return and become hyperactive Blood vessel tonus regulation reflexes (sympathetic nervous system) Immediately after transection o Sympathetic reflexes that control blood vessel tone realized through the T1-L3 are lost o Vascular smooth muscle cells relax → BP decreases, and shock develops After a while o Reflexes are regained and become hyperactive, but blood pressure control still cannot be achieved effectively o Normally → receptors in aortic arch and carotid sinus signals to the medullary region about BP change. Medullary region should send information back to sympathetic centers in the spinal cord to stimulate or inhibit them o Transection → impulses from cardiovascular center in medullary region do not reach sympathetic neurons in the spinal cord and cannot change response in blood vessels o Each segment below transection begin to work independently → some blood vessels dilate while others are constricted depending on the local stimulation of afferent nerve fibers going through the particular segment Bladder and colon evacuation reflexes (parasympathetic nervous system) Immediately after transection o Parasympathetic reflexes (micturition and defecation) realized through the sacral segments are lost o Bladder and colon will fill to greater volumes than normal After a while o Reflexes return and become hyperactive o Smaller volumes in bladder and colon stimulates reflex o Even though reflexes are realized, they cannot be controlled by the person o Colon and bladder fill up until a certain volume and empty automatically no matter the place and time 7 Aurora Killi 25.03.22 Flaccid paralysis Damage of lower motor neuron Depending on the location of damaged motor we can Lower motor neurons are generally α motor distinguish two types of paralysis: flaccid and spastic neurons located in o Anterior horn of spinal cord o Brain stem nuclei which innervate face and eye skeletal muscles Lower motor neurons are generally the last neuron in the chain and transmits impulses to skeletal muscles If we damage this neuron (either in spinal cord transection or at the level of efferent nerve fiber) three signs develop o Areflexia → loss of reflexes o Spinal neuron is damaged o Impulses from peripheral receptors never reach skeletal muscles o All reflexes are lost in the muscle that is innervated by the damaged motor neuron o Atonia → loss of muscle tone o Tonic stretch reflex that maintains muscle tonus is lost o Muscle spindle stretch cannot activate the damaged motor neuron o Impulses are not sent from the neuron back to the muscle to keep its tonus o Atrophy o Develops with time o Since the innervated muscle loses muscle tone, its muscle mass decreases Place of damage on motor neuron determines outcome of the damage o Damage of neuron inside the spinal cord → motor neuron cannot regenerate o Damage to peripheral nerve ending → peripheral nerve ending will degenerate, but the central nerve ending tries to grow back to the muscle o If muscle is close to the damaged site, the nerve fiber can reach the muscle again o If muscle is far away the nerve fiber may not reach the muscle, so the reflex is lost Spastic paralysis Damage of upper motor neuron Upper motor neuron = all motor neurons that send information to the α motor neuron (in anterior horn or brain stem nuclei) Therefore, this is damage of corticospinal or corticonuclei pathways Late signs are opposite to flaccid paralysis o Hyperreflexia → hyperactivity of reflex o The reflex arch is anatomically healthy, but the neuron that send information to the α motor neuron is damaged o Immediately after damage, the reflexes will be lost o After weeks or months → hyperactivity of reflex arches in segments below the damage o Hypertonia o Tonic stretch reflex is more active o Muscle tone is greater o No atrophy → since muscles work even more, no atrophy develops Babinski´s sign Sign of corticospinal tract damage (upper motor neuron damage) In case of upper motor neuron damage, pathological reflexes in extremities can be observed One of these reflexes is Babinski´s reflex Normally 8 Aurora Killi 25.03.22 o If we stroke the lateral side of foot → toes should flex Corticospinal tract damage o If we stroke the lateral side of the foot → toes fan out or move upwards o Indicates that corticospinal tract neurons responsible for activation of α motor neurons are lost Such a pathological reflex also can be used to find out the location of damage 9 Aurora Killi 25.03.22 Functions of the medullary region and pons. Reflexes that are organized through this region Functions of pons and medullary region Medullary region is right above the spinal cord Pons is located above the medullary region Functions organized through both of them are very similar Medullary region and pons have two functions o Conductive o Reflex function Conductive function Related with conductive pathways that join the spinal cord and the brain All ascending pathways go through the medullary region All descending pathways go down through the medullary region into the spinal cord Reflex function Related to reflexes organized through this level. There are four groups of reflexes realized through the medullary region and pons Vital reflexes Breathing reflexes Life important o Respiratory center is located in the medullary region and pons o It controls inspiration and regulates respiration upon changes of respiratory gases in the blood Control of heart rate o Cardiac function control center cardioacceleratory and cardioinhibitory center are located in medullary region. They are responsible for heart rate control upon blood pressure change in the large arteries Control of blood vessel diameter o Vasomotor center is located in the medullary region o Controls diameter of blood vessels due to BP change or chemical composition change of the blood Defense reflexes Coughing Defend body against harmful o Protects respiratory system from harmful substances that substances that can enter might enter with inspired air through respiratory and Sneezing digestive system o Protects respiratory system from harmful substances that might enter with inspired air Vomiting o Protects GI system from entrance of harmful substances Motor and secretory reflexes The three most important parasympathetic nerves are located in for the gastrointestinal tract medullary region and pons o Facial nerve VII o Glossopharyngeal nerve IX o Vagal nerve X Most of GI tract stimulation is done through the medullary region Muscle tonus and posture Vestibular and olivary nuclei activate due to change of body control reflexes posture and adjust muscle tone in extremities to prevent us from falling Reticular nuclei in the reticular formation control excitability of motor neurons in the spinal cord, thus also muscle tone 10 Aurora Killi 25.03.22 Damage of pons and medullary region Most common outcome is death Damage can be related to o Traumatic accidents o Hematomas o Tumors Medullary region is in a vulnerable position if intracranial pressure rises o Brain is pushed down through foramen magnum which is too small for the medullary region to exit into the vertebral column o Compression of medullary region might lead to loss of vital functions (respiration, BP control) causing death 11 Aurora Killi 25.03.22 Functions of midbrain Midbrain Located above pons Functions (physiological) are two o Conductive function related with the conductive pathways o Reflex function related with reflexes realized through the midbrain Functions according to anatomical structures located in midbrain Structure Function Lamina tecti Superior colliculi → related with visual system control and they stimulate Superior colliculi Eye movements Inferior colliculi o Superior colliculi work in concert with the oculomotor and trochlear nerve o Control most of eye external muscles Accommodation o Changes the shape of the lens Pupillary reflexes to light o Both reflexes are related with parasympathetic fibers going into the oculomotor nerve o Midbrain triggers constriction of pupils and contraction of ciliary muscles Visual orientation reflex o Turning of the head in direction of light o Reflex is related with tectospinal tract o Leads to activation of neck muscles that turns our head Inferior colliculi → related with hearing function Hearing orientation reflex is realized through inferior colliculi Head turns in direction of sound source Helps attract attention to sudden stimuli (sound) Periaqueductal grey Contains neurons that secrete matter o Dopamine o Opioid peptides Decreases pain sensation through the antinociceptive system Activates inhibitory neuron in dorsal horn of spinal cord Locus coeruleus One of three colorful substances located in the midbrain Blue area Contains norepinephrine secreting neurons that are activated by periaqueductal grey matter Norepinephrine signaling neurons o Decrease pain sensation by inhibition pain impulse transmission o Sleep-wake cycle o Regulation of emotions and mood o Regulation of body temperature Substantia nigra 1. Substantia nigra contains dopaminergic neurons that Black substance extend their projection to striatum in basal ganglia Movement control 2. Depending on the receptors, they either (with basal ganglia) + Activate striatum cells by binding to D1 receptors Behavioral control (dopamine 1) - Inhibit striatum cells by binding to D2 receptors 12 Aurora Killi 25.03.22 3. Pathways from the striatum take part in movement control 4. Dopaminergic projections also go to cerebral cortex where they regulate memory and behavior Parkinson´s disease Damage to substantia nigra Dopaminergic projections activate and inhibit respective striatum neurons less than before Inability to perform voluntary movements → rigidity and tremor Projections to cerebral cortex suffer as well → o Dementia o Memory problems o Inability to learn new skills and information Reticular nuclei Regulate excitability of central nervous system Scattered all over the midbrain Non-specifically increase excitability of different neurons o Motor neurons o Autonomic neurons o Other neurons (responsible for consciousness regulation, not directly connected to motor or autonomic functions) Nucleus ruber Functions of red nucleus Red substance Three systems ↓ Tonus of extensor - RAS inhibitory part is located inside red nucleus muscles o Send impulses through reticulospinal tract to motor neurons in ↑ Tonus of arm spinal cord and suppress their activity flexors o Decreases impulses that are sent to skeletal muscles + RAS excitatory part is located in the midbrain RAS = reticular activating o Excites motor neurons in spinal cord system + Vestibular nuclei located in medullary region o Receives impulses from vestibular receptors in inner ear o Excite spinal cord motor neurons to prevent falling If we want to sit down, red nucleus is activated to inhibit spinal cord motor neurons and decrease extensor muscle activity Damage of red nucleus → decerebrate rigidity 1. If we damage red nucleus, RAS inhibitory part cannot activate 2. Spinal cord motor neuron inhibition decreases 3. RAS excitatory part and vestibular nuclei are still functional and increases motor neuron activity 4. Extensor muscle tone increases Total damage of both red nuclei → muscle tone increases so much that movement is not possible, person cannot walk Partial damage → muscle tone increases but person can still move 13 Aurora Killi 25.03.22 Functions of cerebellum. Afferent information that comes to the cerebellum, its function. Functional organization of cells in the cerebellum Cerebellum Control motor activities before feedback signals from the periphery reaches the brain It can predict in which direction and how intense muscle contraction should be to achieve the goal of the brain centers Functions of cerebellum Equilibrium control Controls intensity and duration of muscle contraction Provides fast switch from one movement to another Coordinates agonist and antagonist contractions Regulation of cognitive functions, especially regulation of o Speech o Emotional behavior Damage of cerebellum Mostly observe function loss of motor control Cognitive function loss is temporary → other brain centers take up the cerebellum function and regulate cognitive functions quite well Afferent information to the cerebellum Afferent information comes to the cerebellum from everywhere so that is it aware about the current movement and plan of movement. Cerebellum use this information to adjust movement and make it precisely directed. Some of the main sources coming here are Cerebral cortex Cerebral cortex sends information to cerebellum, so it knows that activity is triggered Cerebellum and the cerebral cortex together can plan the next movements that will be performed within the next milliseconds Reticular activating RAS regulates excitability of cerebellar neurons system It can excite cerebellar neurons Vestibular receptors Cerebellum receives a lot of information from vestibular receptors in the and nuclei inner ear that convey information through the vestibular nuclei Vestibular receptors sense body position, acceleration of the body, and direction of movement Olivary nuclei Information from the cortex and periphery comes to the inferior olivary nuclei The inferior olivary nuclei can then compare the plan of movement with the actual condition of the extremities and the body If there is a difference between planned and executed movement, inferior olivary nuclei signal to cerebellum for it to take part in activity control Hearing and Photoreceptors and hearing receptors send information to cerebellum photoreceptors They signal about the surrounding space, where the body is moving, and indicates location of the place we want to move Spinal cord Proprioreceptors Spinal cord sends information through 14 Aurora Killi 25.03.22 two spinocerebellar o Information from proprioreceptors informs cerebellum about where tracts that transfers each extremity is located in space, whether it moves or not, how fast, information from and how intense muscles contraction is Receptors in skin, joints, bones o These receptors give additional information about where our extremities are Anterior motor neurons o Information from anterior motor neurons is carried through anterior spinocerebellar tract o Cerebellum receives information that is already sent to these motoneurons and will know is this motor neuron will activate or inhibited in the next moment Anatomical and functional parts of cerebellum Anatomically, cerebellum is divided into three lobes o Flocculonodular lobe o Posterior lobe o Anterior lobe Functionally, cerebellum is divided into functional zones where the flucculonodular lobe functions separately, while cerebellum is divided into o Vermis o Hemispheres (left & right) On each hemisphere there is an o Intermediate zone directed towards the vermis o Lateral zone directed laterally Cerebellar cortex Made of grey matter and neurons are organized in three layers 1. Granule cell layer (inner) 2. Purkinje cell layer (middle) 3. Molecular layer (outer) Purkinje cells o Branches their dendrites into the molecular layer o Extensive arborization in anteroposterior direction o No arborization in transverse plane o Inhibitory neurons and the only cell type that send information out of the cerebellar cortex Granule and molecular cells o Elaborates information inside the cerebellar cortex o modifies the information sent out from Purkinje fibers Granule cell layer consists of o Excitatory neurons (Granule cells) that excite Purkinje cells o Inhibitory neurons (e.g., Golgi cells) that inhibit granule cells Molecular cell layer consists of two more important inhibitory neurons o Stellate cells o Basket cells Deep nuclei Almost all information from cerebral cortex is sent to deep nuclei of cerebellum. Together they form the only output of cerebellum o Dentate nuclei 15 Aurora Killi 25.03.22 o Interposed nuclei o Fastigial nuclei These nuclei send information out of cerebellum to o Brain stem structures o Encephalic structures o Cortex Cell arrangement in cerebellum Purkinje cells (mainly) transmits information out of the cerebellar cortex and release GABA that inhibits deep nuclei cell Deep nuclei cell is almost the only cell that sends information out of cerebellum Afferent information reaches cerebellum through two types of nerve fibers Climbing fibers Begin from inferior olivary nuclei where information from cerebral cortex and peripheral receptors meets Climbing fibers go in two directions in the cerebellum First, they activate deep nuclei cells Afterwards the same fiber transmits impulses to Purkinje cells o Climbing fibers are precise o One climbing fiber gives impulses to a few Purkinje cells o If one climbing fiber activate → few Purkinje cells activate in cerebellar cortex Principle of response 1. When climbing fibers activate Impulse transmission through the efferent fiber of deep nuclei will increase + Movement is facilitated 2. When impulses arrive in the cerebellar cortex Purkinje cell activates Inhibits the same deep nuclei Impulse frequency decreases - Facilitation of movement stopped Mossy fibers Begin from sources outside inferior olivary nuclei o Different brainstem structures o Spinal cord o Cerebral cortex o Other receptors in other centers of brain Mossy fibers go in two directions as well o First, they active deep nuclei cell through the short loop o Branch off and go to cerebellar cortex where they activate granule cells Granule cells activate many Purkinje cells through parallel fibers o One granule cell can activate hundreds or thousands of Purkinje cell o One Purkinje cell can receive information from many granule cells o Gives wider response in cerebellum 16 Aurora Killi 25.03.22 Principle of response 1. When mossy fibers are activated Deep nuclei cell activates Impulse frequency through efferent fibers increases 2. When granule cell is activated Purkinje cells cause inhibition of deep nuclei cell Impulse frequency decreases 3. Granule cells also activate other inhibitory neurons in cerebellar cortex Basket cells cause inhibition of Purkinje cell Golgi cells cause inhibition of granule cells themselves Purkinje cell activation by mossy fiber is not as strong as from climbing fiber because it is activated but also inhibited (by basket and Golgi cells) In such a way, cerebellum facilitates movements and stop them at the exact point that we want to 17 Aurora Killi 25.03.22 Functional parts of cerebellum; their functions. Consequences of the damage of cerebellum Functional parts of the cerebellum Cerebellum has no direct pathway to the spinal cord, but rather uses brainstem and cortical nuclei to send information to the spinal cord. It has a certain topographical localization of the body; however, it is only presented in the vermis and intermediate zones of hemispheres Cerebellum controls movements in the same side of the body o Right hemisphere controls movements in the right side of the body o Left hemisphere controls movements in the left side of the body Vestibulocerebellum Flucculonodular lobe belongs to this part Vestibular system Related with vestibular function regulation Receives information from o Vestibular receptors about o Equilibrium and acceleration o Direction of acceleration o Visual receptors about o Surrounding objects o Neck receptors o Predict if it is a whole-body movement or just head movement Flucculonodular lobe sends information directly to the vestibular nuclei in the brain stem From the vestibular nuclei, information goes through the vestibulospinal tract to the spinal cord motor neurons to adjust muscle contraction to provide stability of the body Spinocerebellum Includes vermis and intermediate parts of both hemispheres Spinal cord Receives information from o Vestibular receptors Informs about body position o Hearing receptors and where it moves o Photoreceptors o Proprioreceptors o Vermis → receives information from trunk o Intermediate parts → from extremities mostly It also receives information from cerebral cortex motor areas o These areas signal to motor neurons in spinal cord and brain stem o Gives collateral branches to the cerebellum to inform about current body movement The information is elaborated in all layers of cerebellar cortex and deep nuclei cells, and sent out to several nuclei o Vermis sends information through fastigial nuclei o Intermediate parts send information through interpose nuclei Information from deep nuclei is further sent out of cerebellum to o Vestibular nuclei send information further through vestibulospinal tract to the spinal cord o Reticular nuclei send information through reticular spinal tract to spinal cord o Red nuclei send information through rubrospinal tracts to the spinal cord o Thalamus transmits information to cerebral cortex from where corticospinal and corticonuclear tracts send information down to 18 Aurora Killi 25.03.22 o Spinal cord motor neurons or o Brainstem motor neurons Body parts are topographically represented in discrete parts of spinocerebellum o Vermis o Mostly control axial muscles (trunk, large muscles in extremities) o Mostly receives information form proprioreceptors in the trunk o Send information back to muscles of the trunk and large muscles of extremities o Intermediate parts o Mostly receive information from proprioreceptors in extremities o Send information back to muscles in extremities o Regulate precise actions Cerebrocerebellum Include lateral parts of cerebellum that communicate with cerebral cortex Cerebral cortex Receives information from cerebral cortex secondary and tertiary areas responsible for planning next activities Secondary and tertiary areas send information through thalamus and back to cerebral cortex through the dentate nucleus of cerebellum Cerebrocerebellum mainly deals with regulation of next movement Learning in the cerebellum Cerebellum activity can be modified by learning. If we learn new motor tasks, cerebellum adjust to make our movements more precise. In an experiment people were asked to throw darts and precision was monitored Before wearing glasses at all o Precision of throws are quite good When wearing glasses o Glasses moved visual field laterally o Right away → throws became unprecise and more laterally because the visual signal was deviated from the actual location of the target plate o Afterwards → person started to correct the throwing precision After wearing glasses o Right away → darts were thrown to the opposite side because the cerebellum had corrected the previous movement when the glasses were worn o Afterwards → precision increased and return to normal Damage of cerebellum o This type of correction is not possible o When the glasses are put on, the correction by cerebellum is not made o The person shoots the same way before and after wearing glasses, and while wearing them the throws remain unprecise because the correction by cerebellum is not achieved Cerebellar damage Causes of damage Non-reversible damage (most often) 19 Aurora Killi 25.03.22 o Stroke in brain All signs of cerebellar damage o Hemorrhage in brain appear while moving o Tumors in posterior fossa If person is in bed with closed eyes, o Traumatic accidents damaging cerebellum these signs are not visible Reversible damage As soon as person moves, great o Alcohol consume disorder of movement is observed o Activates GABA receptors → functional inhibition of Signs appear in the same side to the cerebellum cerebellar damage o When the alcohol is washed out of the system, the cerebellar damage sites disappear Dysequilibria Inability to maintain equilibrium Eyes open → visual signals help to maintain equilibrium to some extent o Not very precise o Person oscillates o Not able to keep straight vertical position Eyes closed → visual signals and equilibrium is lost o Conscious equilibrium centers detect the deviation from vertical position too late o Precise equilibrium control by conscious centers is unprecise Dysmetria Inability to predict distance to an object and thus also the force necessary to reach it Can be checked by using a finger-nose probe Person is asked to point the finger at the nose tip with eyes closed If cerebellum is working o Movement is pretty precise o Cerebellum predicts the direction of the hand movement and knows where the nose tip is If cerebellum is damaged o Hand movement control is lost o Finger dose not reach the nose Ataxia Loss of coordination of movements If cerebellum is damaged, conscious systems detect deviation from goal only with greater amplitude of movement Movements either over- or undershoot the goal Conscious systems try to compensate for the imprecision by involving additional movements causing the movement to overshoot the other direction This causes uncoordinated movements Intention tremor Oscillatory movements or intention tremor Movements overshoots in one direction and the person tries to correct it to the opposite side Intention tremor in extremities as it approaches the goal is with o Low frequency (3-5 Hz) o High amplitude Dysdiadochokinesia Inability to perform rapid alternative movement This defect is more visible in fast movements compared to slow Every next movement is triggered too fast or too slow, so the movement becomes uncoordinated Dysarthria Inability to speak due to uncoordinated muscle activity 20 Aurora Killi 25.03.22 Speech requires rapid change from contraction to relaxation of different speech muscles Coordination of these muscles is lost Some sounds are too short while others too long → articulation ununderstandable Nystagmus Nystagmus is oscillation of the eyeball The cerebellum is important regulator of the vestibular ocular reflex. Without the cerebellar function, also eyeball muscle movement become with greater inertia, not being able to stop the eyeball exactly at the moment it focuses on the object We can observe nystagmus for person with damage of cerebellum when he/she is looking at the stationary object Low muscle tonus Hypotonia Low muscles tone in muscles of the same side as the cerebellar damage 21 Aurora Killi 25.03.22 Functions of the hypothalamus Functions of hypothalamus Located below thalamus and is related with behavioral reaction regulation. Hypothalamus includes three types of important centers Highest autonomic centre → coordinates activity of sympathetic and parasympathetic nervous system Highest endocrine centre → regulates most of the hormone secretion in the body Limbic system centre → regulates emotional reactions and behavioral reactions Regulation of behavior All three centers together regulate different behavioral programs Thirst regulation Thirst reaction in the body is collectively regulated by o Pre-optic area o Paraventricular nuclei o Supraoptic nuclei If pre-optic area signals to cortex about need of drinking water → ventricular and supraoptic nuclei regulate ADH secretion, preventing dehydration Hunger & satiety Hunger center → lateral hypothalamic area regulation o Stimulates food intake Satiety center → ventromedial nucleus o Decreases food intake o Stimulates use of stored substances for energy production Sleep centre Located in ventrolateral pre-optic nuclei (mostly) Suppress systems that arose the brain Work in relationship with suprachiasmatic nuclei which o Receive information about day and night cycle in external environment o Coordinate out sleep behavior according to dark and light cycles Thermoregulation Anterior hypothalamus → stimulate responses to heat in body centre Posterior hypothalamus → stimulate reactions to cold Regulation of Hypothalamus takes part in regulation of sexual functions o Sexual functions o Pregnancy and lactation Neuroendocrine cells in medial and lateral pre-optic nuclei regulates sexual functions in relation to o Limbic system o Endocrine system (regulates hormone production and sexual function) Regulation of Hypothalamus takes part in stress regulation stress Regulation of Suprachiasmatic nuclei regulate circadian rhythms biological rhythms It receives information from retina about light and dark cycles in the environment Adjust different cycles according to the day and night rhythms. Such as o Hormone secretion from hypothalamus o Temperature rhythms o Sleeping patterns o Other biological rhythms 22 Aurora Killi 25.03.22 Functions of thalamus; functional groups of nuclei and their functions Functions of thalamus Nuclei of thalamus area divided into several groups according to their anatomical localization Anterior group Lateral group Medial group Small intralaminar nuclei (located in the internal lamina of white matter which divides thalamus into several parts) Nuclei group Function Relay nuclei Relay information going to the cerebral cortex Ventral posterolateral Ventral posterolateral and posteromedial nuclei Ventral posteromedial o Bring information from somatosensory system to cerebral cortex Medial and lateral Medial and lateral geniculate bodies geniculate nuclei o Bring hearing and visual information to the cerebral cortex Ventral lateral Ventral lateral and anterior nuclei Ventral anterior o Mostly bring information from other parts of the brain to the cerebral cortex o Like information from cerebellum and basal ganglia used for planning and programing next movements o Information from basal ganglia is used for initiation of voluntary movement Association nuclei Connects different centers in the brain for common function Pulvinar Pulvinar nucleus Dorsomedial o Biggest nucleus in the posterior part of thalamus Medial o Receives information from visual subcortical and cortical centers o Sends this information to the areas that deals with visual perception of stimuli and eye movement regulation Dorsomedial nucleus o Receives information from subcortical and cortical centers of vision o Integrates this information for control of o Eye movements o Direction of attention to the visual stimuli o Regulation of emotional behavior. Medial nuclei o More related with the emotional control o Bring information into limbic structures of the cerebral cortex, and regulates emotions Nonspecific nuclei Intralaminar or reticular nuclei work in close association with the Intralaminar/reticular reticular activating system (RAS) nuclei Regulates sleep-wake cycle and alertness of the person If thalamus is damaged, integration of information between centers is lost 23 Aurora Killi 31.03.22 Basal ganglia, cerebral cortex & limbic system Functions of basal ganglia. Short and long circuit through basal ganglia............................................................................................ 2 Cortical areas of the brain (primary, secondary, and tertiary) and their functions............................................................................. 8 Functional asymmetry types of cortical areas................................................................................................................................... 12 Speech mechanism............................................................................................................................................................................. 14 Language areas in the cerebral cortex; their functions and damage consequences......................................................................... 16 Limbic system. Regulation of emotions. Subjective and objective components of emotions.......................................................... 18 Functions of hippocampus and amygdaloidal nucleus...................................................................................................................... 20 1 Aurora Killi 31.03.22 Functions of basal ganglia. Short and long circuit through basal ganglia. Basal ganglia Located subcortically in the big hemispheres Anatomical structure Caudate nucleus Anatomically, basal ganglia o Extends from temporal lobe into parietal and consist of three main nuclei frontal lobe o Located more medially (in transection) Striatum Putamen o Located most laterally (in transection) o Together with caudate nucleus form striatum Globus pallidus o Located medially to putamen and has two parts that function differently o Internal part o External part (located laterally) Clinical and physiological Substantia nigra → located in midbrain structure Subthalamic nuclei → located below thalamus Two additional nuclei Their functions are closely related with basal ganglia; thus, they are included in the clinical classification Functions of basal ganglia 1. Encode decision to move Basal ganglia turn idea of movement into physical movement Allow voluntary movements to begin 2. Regulate direction of movement 3. Regulate amplitude of movement These two functions are similar to cerebellar functions If cerebellum is damaged, basal ganglia can partially compensate the movement disorder 4. Regulation of motor expression of emotions Activate hand and facial muscles to express emotions In form of gestures or facial expressions Basal ganglia movement control Explanation of schematic representation Striatum is the combination of putamen and caudate nucleus Globus pallidus with external and internal part, is connected to thalamus and cerebral cortex Substantia nigra is divided into two parts o Compact part (pars compacta) → functions separately o Reticular part (pars reticulata) → has common functions as globus pallidus internal part and when internal globus pallidus is mentioned it also includes reticular part Ingoing information o Comes from cerebral cortex mostly o Arrives in striatum both from cortex and substantia nigra compact part Outgoing information o Leaves from internal globus pallidus and substantia nigra reticular part 2 Aurora Killi 31.03.22 o Sent through thalamus to cerebral cortex o Information from reticular part of the substantia nigra goes to superior colliculi to regulate fast or saccadic eye movements Neurons in basal ganglia Red neurons → inhibitory o Work with neurotransmitter GABA Blue neurons → excitatory o Neurotransmitter glutamate o Located in cerebral cortex, subthalamic nuclei, and thalamus Grey neurons → dopaminergic o Located in substantia nigra o Neurotransmitter is dopamine, which can work both excitatory and inhibitory, depending on the receptor it binds to o D1 receptor → excitation o D2 receptor → inhibition Direct circuit Also called excitatory circuit → leads to disinhibition of movements so movement is stimulated 1. Cerebral cortex neurons activate striatum neurons when idea of movement is made Mostly neurons in secondary and tertiary motor areas responsible for planning of movement sends information to striatum Some neurons in primary motor areas responsible for triggering voluntary movement can also send information to striatum 2. Neurons in substantia nigra compact part also sends impulses to direct circuit neurons in the striatum Direct circuit neurons in striatum have D1 receptors → excitation Substantia nigra itself is activated from different sources, including the cerebral cortex When idea of movement is made in cortex it sends impulses directly to striatum and also through substantia nigra to striatum 3. Striatum neuron activity increases Greater inhibition of internal globus pallidus and substantia nigra reticular part Inhibition of thalamic nuclei decreases 4. Thalamic nuclei increase activity More impulses are sent to cerebral cortex motor areas Through corticospinal and corticonuclei pathways information is sent to motor neurons in spinal cord → movement is triggered 3 Aurora Killi 31.03.22 Indirect reflex 1. Begins in cerebral cortex with an idea of movement Impulses are sent to striatum neurons that take part in indirect circuit 2. Substantia nigra compact part send impulses to striatum neurons that take part indirect circuit Dopamine binds to D2 receptor on the neurons of striatum → inhibition Striatum neurons in indirect circuit is activated by cerebral cortex neurons, but inhibited by substantia nigra, therefore they activate lesser than in the direct circuit 3. Striatum neurons stimulate inhibition of external globus pallidus Inhibition of subthalamic nuclei is removed and it stimulates internal globus pallidus and reticular part of substantia nigra Greater inhibition of thalamic nuclei 4. Thalamus decreases its activity Less impulses are sent to cortex Impulse transmission through corticospinal and corticonuclei pathways decreases → movement is inhibited Both circuits are stimulated simultaneously When person decides to move impulses go through the direct circuit and stimulate the movement At the same time, impulses are sent through the indirect circuit and inhibit other similar movements Basal ganglia cause central activation of a particular motor program, and causes inhibition of surrounding motor programs that are very similar to the movement Damage to basal ganglia cause different diseases o Some might cause greater intensity of movements o Others might cause greater suppression of movements Parkinson´s disease Hypokinetic disease (less movement than necessary) Causes of Parkinson´s → develops due to degeneration of substantia nigra neurons o Age related degeneration o In old age, general neuron loss in the brain can also decrease neuron number in substantia nigra o This might sometimes lead to Parkinson´s disease symptoms o Genetic inheritance o Autosomal dominant and autosomal recessive inheritance pattern o Traumatic damage o Can sometimes be observed for boxers who gets multiple hits to their heads throughout their carrier o This may cause greater degeneration of neurons in the brain o Toxic damage, tumors, and strokes Effect on direct circuit 4 Aurora Killi 31.03.22 o When we want to move, substantia nigra neurons cannot activate striatum neurons as much as before o Striatum neurons activates lesser and causes weaker inhibition of internal globus pallidus and reticular part of substantia nigra o Internal globus pallidus neurons activate more and cause stronger inhibition of thalamic nuclei o Thalamus cannot activate motor cortex → smaller amplitude movement or no movement at all Effect on indirect circuit o Due to loss of dopaminergic neurons, inhibition of striatum that takes part in the indirect circuit, is not as effective as before o If cortical neurons activate, activity of striatum is greater because inhibition from substantia nigra is lost o Striatum stimulates greater inhibition of external globus pallidus, which inhibits subthalamic nuclei lesser o Subthalamic nuclei activate internal globus pallidus and reticular part of substantia nigra more, causing suppression of thalamic nuclei o Thalamic nuclei cannot activate cortical neurons anymore, causing greater inhibition of movements also in the indirect circuit Signs of Parkinson´s disease Loss of ability to initiate voluntary movement o Due to the inability of the direct circuit to trigger movement, the person loses ability to initiate voluntary movement o It is not enough strength of the impulses to stimulate the particular program of movement Stooped posture o People with Parkinson´s are bent a little forwards with a flexed body o Flexed arms and legs and little movement in extremities with widely flexed arms and legs Rigidity of muscles and trembling o Muscles are more stiff than usual o Muscles are not able to execute motor programs very well o Also, trembling, and small tremor of the arms, legs, and head Cognitive inabilities and dementia o Since dopamine is necessary for memory and cognitive abilities. Therefore, it also leads to cognitive inabilities and dementia Short-stepped gait of the person Masked facial expressions Treatment Methyl-dopa o A drug that frees dopamine in the body to normalize activity of the striatum o Over the years of use of methyl-dopa the necessary does increases and side effects develop Deep brain stimulation o In later stages deep brain stimulation can help to normalize the activity of basal ganglia and decrease the symptoms Huntington´s chorea Hyperkinetic disease (excessive movements) Autosomal dominant inheritance 5 Aurora Killi 31.03.22 Pathology chromosome 4 which regulates huntingtin gene expression Causes degeneration of o Caudate nucleus primarily o Putamen size o Globus pallidus Effect on indirect circuit Degeneration begins with neurons in striatum that take part in the indirect circuit, therefore the main problem is in this circuit 1. Cerebral cortex sends impulses to the striatum Striatum neurons in the indirect circuit do not activate 2. Inhibition of external globus pallidus becomes weaker Increased inhibition of subthalamic nuclei Decreased excitation of internal globus pallidus and reticular part of substantia nigra 3. Inhibition of thalamic nuclei decreases Thalamic nuclei which now can send more impulses to the cerebral cortex 4. Cerebral cortex neurons activate more than usual, causing more movements Indirect circuit is normally supposed to inhibit unnecessary motor program Now, unnecessary motor program become activated, and movement occur unvoluntary 5. Remaining neurons try to compensate for the loss Direct striatum neurons increase activity Greater inhibition of internal globus pallidus Inhibition of thalamus decreases More impulses are sent to the cortex and hyperactivity occurs, even if the person does not wish to move Signs of Huntington´s disease Unvoluntary movements o Arms flex or extend o Legs flex o Hips and trunk rotate or flexes Uncoordinated gait o The persons gait becomes very uncoordinated o In severe cases they are not able to move normally o Person tries to include these sudden, unvoluntary movements in their normal movement scheme Finger movements o Characteristic finger movement that resembles piano playing Treatment Drugs that inhibit dopamine receptors and o Block stimulation of direct circuit o Decrease inhibition in the indirect circuit Deep brain stimulation Deep brain stimulation We can implant pacemaker in the brain that rhythmically stimulates certain centers A battery generates pulsatile signals that ascend to the electrode that is implanted in the brain 6 Aurora Killi 31.03.22 The tip of the electrode is placed close to the basal ganglia, either to o Globus pallidus or o Subthalamic nuclei The pulsatile signals help to normalize impulse frequency that is sent from these neurons, and decrease the movement abnormalities 7 Aurora Killi 31.03.22 Cortical areas of the brain (primary, secondary, and tertiary) and their functions Cortical areas Brodmann classified the cortical areas into 52 areas according to their peripheral connections and functions They can also be divided into three functional groups o Primary o Secondary o Tertiary Primary cortical areas Tightly connected with receptors and effectors Can be divided into primary sensory and primary motor areas Primary Primary taste area somatosensory area o Located in insula at the bottom of the primary somatosensory area Located in where the tongue region is located postcentral gyrus o Provide conscious taste perception (parietal lobe) Primary visual area Receives information o Located in the occipital lobe from touch, pressure, o Deals with impulses received from the retina pain, temperature, o Provides conscious visual sensation and proprioreceptors Primary hearing area Creates conscious sensation o Located in superior temporal gyrus o Deals with analysis of hearing signals Primary smell area o Located on the superolateral side o Medially in the uncus we also have primary smell area located Damage → anesthesia Loss of conscious sensation of touch, pressure, pain, temperature, and proprioception or anesthesia Damage of primary visual area → cortical blindness develops Damage of primary hearing area → cortical deafness There can also be partial area damage causing loss of sensation in a particular place of the body Sensory homunculus In the primary somatosensory area, the human body is represented in a sensory homunculus o Legs face up into the medial hemisphere surface o Head face down on the superolateral surface Hands and face cover the largest regions → detailed sensation in these body parts Legs and trunk have a small region → sensation is not very precise, and we cannot determine very precisely the localization of stimuli 8 Aurora Killi 31.03.22 Primary motor area Located in the precentral gyrus in the frontal lobe Triggers conscious movements in the body Damage to primary motor area causes inability to perform conscious movements or paralysis Motor homunculus The motor homunculus is located in the primary motor area It represents the human body, with the legs up and the head facing down o Greatest area represents hand and face → provides detailed movements for these body regions o Relatively small area represents legs and trunk → less detailed movements with these body parts If we stimulate a particular regions of the primary motor or sensory area, we will get either sensation or motor activity in the corresponding body part Secondary cortical areas Located around the primary cortical areas and are related with receptors and effectors Also divided into sensory and motor areas Secondary somatosensory Secondary somatosensory area area o Located behind the primary somatosensory area Located around the o Characterizes somatic sensations in the body more in detail primary sensory areas o We can determine the structure of the object purely by the touch Characterize the (sharp, blunt, hard, soft etc.) sensation Secondary visual area o Located around the primary visual area o Analyzes visual information more in detail o We can tell if the object is moving or not, coming closer or going further away etc. Secondary hearing area o Similarly, hearing secondary area analyses the sounds of what we hear Damage → agnosia Leads to loss of ability to characterize conscious sensation, or inability to recognize what it is that we sense by just the sensation. This is called agnosia Secondary visual area damage leads to the visual agnosia in which we cannot recognize the object by looking at it Secondary hearing area damage leads to hearing agnosia in which we cannot characterize the sound or the cause of it In all cases of agnosia, sensation is present, just characterization is lost Secondary motor area Secondary premotor area → located on the superolateral surface and Located in front of deals with coordination of voluntary movements of the hands and head primary motor areas o Hand control area Deal with coordination o Located in the secondary premotor area of voluntary movements, o Controls conscious complex movements in the hands and planning and fingers such as playing instrument programming of o Eye control area movements 9 Aurora Killi 31.03.22 o Eye control area is also located here o Controls head and eye movements so it can be coordinated with the hand movement o Speech area o Located at the bottom of the premotor area o Coordinates muscle activity necessary for speech o Sends impulses in a discrete sequency to the primary motor area to activate motor neurons responsible for speech muscle activation Secondary supplementary area o Located on above premotor area mostly in the medial surface of the hemispheres o Coordinates motor activities in both sides of the body, in both arms and both legs o This area is for example responsible for climbing movements Damage → apraxia Both of these areas take part in planning of movements In case of damage to secondary motor areas it will lead to apraxia Inability to perform more complex movements o Buttoning shirt may not be possible o Speech and eye movement following hand movement will be uncoordinated Tertiary cortical areas Not connected with receptors and effectors and not divided into motor and sensory areas Take up the remaining parts of cerebral cortex and are located in o Frontal lobe (prefrontal cortex) o Parieto-occipitotemporal region Control higher integrative functions such as o Learning and memory o Thinking o Planning and programming o Decision-making o Outcome-prediction o Regulation of social behaviors and emotions o Help us understand speech (Wernicke´s area) Damage of tertiary areas Damage of tertiary areas → loss of higher integrative functions Change of behavior, learning, memory, and dysregulation of emotional control Example: Phineas Gage Railway worker that got a rod (l: 1 m, d: 3 cm) through his skull in an explosion o Entered the skull from below the cheekbone o Went through the orbit and brain o Leaving the skull from the upper part The accident caused damage to tertiary areas in cerebral cortex but not to motor areas Before the accident o Known and respected member of society o Reliable and a good worker 10 Aurora Killi 31.03.22 After recovery o Impulsive o Socially inappropriate o Unreliable Language function, memory, and intellectual function were not deficient, but his emotional regulation was deficient, and his behavior changed 11 Aurora Killi 31.03.22 Functional asymmetry types of cortical areas Functional asymmetry Functional asymmetry is the functional dominance of symmetrical cortical areas in one side One side of the brain takes up more of the function control The dominant side is not bigger in size (wider or thicker), but simply functionally dominant There are three dominance types according to the areas that dominate Sensory dominance Dominance of sensory areas in one side of the brain The dominating hemisphere analyze signals better and causes person to prefer that side sensation Visual dominance → most people have one dominant eye because the information from that eye is better described in the visual areas Hearing dominance → hearing areas in one hemisphere is dominant, and we chose the corresponding ear for example to talk on the pone Sensory dominance → somatosensory area dominates in one side. We prefer to check temperature of water with one hand Motor dominance Functional dominance of motor areas in one hemisphere 90% of people o Left hemisphere motor areas dominate o Causes right-handedness 10% of people o Right hemisphere motor areas dominate o Causes left-handedness Ambidexters o People who do not have well described dominance in one hemisphere o They can work equally well with both hands and both legs Mental dominance Dominance of tertiary areas in one hemisphere → causes different behavior Left hemisphere tertiary areas o Deals with mathematical and logical thinking o Also responsible for language, lexical, and synthetic functions o People with left hemispheral dominance are believed to have o Better memory (names and numbers) o More positive emotions o Talkative and extrovert Right hemisphere tertiary areas o Deals with artistical thinking and analysis of information of emotional coloring of language (intonation) o People with right hemispheral dominance are o Poorer memory on facts and numbers o Artistical abilities (uses color pens) o Introvert o More negative emotions Expression of dominance and damage Dominances are randomly distributed and not related to each other o Expression of all three types of dominance is not always in the same hemisphere o If a person is right-handed, it only means that motor dominance is in the left hemisphere o Mental and sensory dominance can be in the other Dominance in one hemisphere causes different function loss after damage o If damage is in dominant hemisphere → function loss is greater, and recovery takes more time 12 Aurora Killi 31.03.22 o If damage is in non-dominant hemisphere → function loss is lesser, and recovery time might be faster 13 Aurora Killi 31.03.22 Speech mechanism Speech mechanism Consists of three processes 1. Phonation → generation of sound by vibration of vocal cords 2. Resonance → induction of vibration in the rest of the vocal tract to modulate sounds produced in the larynx 3. Articulation → shaping of voice into words Phonation Phonation is done in the larynx by the help of vocal cords Vocal cords are stretched in between arytenoid and thyroid cartilage When we don´t speak → vocal cords are open o Opened due to posterior cricoarytenoid muscle contraction o There is no air flow obstruction and thus no sound produced When we speak → vocal cords approximate o Lateral cricoarytenoid muscle contraction rotates arytenoid cartilage o Vocal cords close and interrupt air flow Mechanism of vocal cord vibration Subglottic pressure = pressure 1. Before speaking, deeper inspiration than usual is made and vocal below vocal cords

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