Este documento descreve os sistemas sensoriais e as propriedades gerais da recepção sensorial. Resume que os sistemas sensoriais são conjuntos de estruturas que captam e interpretam estímulos do meio externo ou interno, gerando sensações. Detalha os principais componentes dos sistemas sensoriais, incluindo receptores, vias sensoriais e áreas sensoriais centrais. Explora também a codificação e transdução dos estímulos sensoriais.
An action potential is an electrical signal that propagates along the surface of a neuron membrane due to the movement of sodium and potassium ions through specific ion channels. It occurs in four phases: 1) Resting potential with sodium and potassium channels closed, 2) Depolarization with sodium entry lowering the membrane potential, 3) Repolarization with sodium channel inactivation and potassium efflux restoring the potential, 4) Repolarization continuation with full potential restoration before returning to resting potential. This process allows an electrical signal to travel down an axon through repeated action potentials.
The nervous system is made up of the central nervous system (brain and spinal cord) and the peripheral nervous system (nerves). The brain is divided into three main parts - the forebrain, midbrain, and hindbrain. The forebrain includes the cerebrum, thalamus, and hypothalamus. The midbrain contains the tectum and tegmentum. The hindbrain comprises the cerebellum, pons, and medulla. Each region of the brain controls different functions, from basic functions like breathing and heartbeat to higher functions like memory, language, and decision making. Sensory nerves gather information and motor neurons deliver instructions from the brain to the body.
This document provides an overview of the autonomic nervous system (ANS). It discusses the two divisions of the ANS - the sympathetic and parasympathetic divisions. The sympathetic division is involved in the fight or flight response and increases heart rate, breathing, etc. The parasympathetic division is involved in rest and digest functions like digestion. The document details the pathways, ganglia, nerves and effects of both divisions. It notes that the hypothalamus and brainstem have significant control over autonomic function.
Este documento descreve os sistemas sensoriais e as propriedades gerais da recepção sensorial. Resume que os sistemas sensoriais são conjuntos de estruturas que captam e interpretam estímulos do meio externo ou interno, gerando sensações. Detalha os principais componentes dos sistemas sensoriais, incluindo receptores, vias sensoriais e áreas sensoriais centrais. Explora também a codificação e transdução dos estímulos sensoriais.
An action potential is an electrical signal that propagates along the surface of a neuron membrane due to the movement of sodium and potassium ions through specific ion channels. It occurs in four phases: 1) Resting potential with sodium and potassium channels closed, 2) Depolarization with sodium entry lowering the membrane potential, 3) Repolarization with sodium channel inactivation and potassium efflux restoring the potential, 4) Repolarization continuation with full potential restoration before returning to resting potential. This process allows an electrical signal to travel down an axon through repeated action potentials.
The nervous system is made up of the central nervous system (brain and spinal cord) and the peripheral nervous system (nerves). The brain is divided into three main parts - the forebrain, midbrain, and hindbrain. The forebrain includes the cerebrum, thalamus, and hypothalamus. The midbrain contains the tectum and tegmentum. The hindbrain comprises the cerebellum, pons, and medulla. Each region of the brain controls different functions, from basic functions like breathing and heartbeat to higher functions like memory, language, and decision making. Sensory nerves gather information and motor neurons deliver instructions from the brain to the body.
This document provides an overview of the autonomic nervous system (ANS). It discusses the two divisions of the ANS - the sympathetic and parasympathetic divisions. The sympathetic division is involved in the fight or flight response and increases heart rate, breathing, etc. The parasympathetic division is involved in rest and digest functions like digestion. The document details the pathways, ganglia, nerves and effects of both divisions. It notes that the hypothalamus and brainstem have significant control over autonomic function.
The cerebellum and basal ganglia play important roles in motor control and coordination. The cerebellum helps control the timing, smoothness, and intensity of muscle movements. It receives sensory feedback and compares actual movements to planned movements, sending corrections back to the motor system. The basal ganglia help plan and control complex patterns of muscle movement. The cerebellum has distinct input and output pathways and its Purkinje cells provide inhibitory signals that help regulate the output of deep nuclear cells and coordinate movement.
O documento descreve o sistema nervoso simpático, seus neurotransmissores e receptores. É detalhada a biossíntese, armazenamento e liberação da norepinefrina, assim como os tipos de receptores adrenérgicos e seus agonistas e antagonistas. Por fim, são explicadas as propriedades físico-químicas da norepinefrina e epinefrina e como modificações estruturais afetam a atividade dos fármacos adrenérgicos.
This document provides information about the circulatory system of a rat. It includes labeled diagrams showing the major arteries and veins of the rat. The text then provides instructions to trace various branches of arteries and veins, labeling key blood vessels like the aortic arch, abdominal aorta, renal arteries, inferior and superior vena cava, and hepatic vein. Checkboxes are included for the student to check off structures as they are located during the dissection.
The tropical cone snail hunts fish using a venomous harpoon-like tooth. Its venom acts extremely quickly, paralyzing prey within seconds through a mixture of toxins that disrupt neuronal signaling. Neurons communicate through electrical and chemical signals, and the cone snail venom interferes with both types of signaling. This prevents the prey's neurons from controlling locomotion and respiration, resulting in its inability to escape or survive the venom's effects.
The thalamus is a paired subcortical structure that relays sensory and motor signals to the cerebral cortex. It contains several nuclei that have specific connections to different regions of the cortex. The thalamus develops from the thalamic plate and differentiates into the epithalamus, dorsal thalamus, and ventral thalamus. The dorsal thalamus contains nuclei that project to the cortex via thalamocortical fibers. The thalamic reticular nucleus, part of the ventral thalamus, surrounds the dorsal thalamus and provides inhibitory input to it. The cerebral cortex is a laminated sheet of neurons involved in higher-level signal processing. It receives input from the thalamus and sends
B.Sc.(Micro+Biotech) II Animal & Plant Physiology Unit 4.1 Neurones & The Act...Rai University
Neurons have three main parts - the cell body, dendrites, and axon. Dendrites receive impulses and pass them to the cell body, while the axon sends impulses to other neurons. At rest, the neuron maintains an electrochemical gradient with more positive charges outside and negative inside. This gradient is maintained by active transport of ions against their concentration gradients. When stimulated, the neuron's membrane becomes permeable to sodium ions, causing depolarization and generating an all-or-none action potential if the threshold is reached. The action potential travels down the axon before the neuron enters refractory periods and returns to resting potential.
diaporama découverte des rythmes du sommeil
rôle du sport, caféine, sieste...
modification des rythmes chez la personne agée
consignes pour bien s'endormir
The document provides an overview of the autonomic nervous system (ANS). It discusses that the ANS is not under conscious control and regulates functions like blood pressure, heart rate, and gland secretion. It describes the two divisions of the ANS as the sympathetic and parasympathetic nervous systems. Key differences between the two divisions are described such as neurotransmitters, locations of ganglia, and effects on target organs. Examples of neurotransmitters, receptor types, and locations are outlined. Common drugs that target the adrenergic and cholinergic systems are also summarized along with their indications and actions.
This document provides information on nervous tissue and neurons. It discusses that nervous tissue consists of neurons and neuroglia. Neurons are specialized to receive sensory stimuli, process information, and transmit signals via nerve impulses. Neuroglia support and nourish neurons. The structure of neurons includes a cell body containing a nucleus, dendrites that receive signals, and an axon that transmits signals. Neurons are classified based on their structure and function. Synapses allow neurons to communicate via chemical or electrical signaling. The document also describes various sensory nerve endings and the stimuli they detect, as well as motor end plates that transmit signals to effector cells.
O documento descreve as funções e estrutura básica do sistema nervoso. O sistema nervoso é responsável por perceber estímulos ambientais e internos e elaborar respostas para adaptar o organismo às condições. A unidade básica é o neurônio, que conduz impulsos nervosos e se conecta a outros neurônios em cadeia. O sistema nervoso central processa informações e o periférico conduz informações entre órgãos e o cérebro.
O documento descreve a anatomia e o funcionamento do sistema nervoso central e periférico em humanos. Explica que o sistema nervoso central, constituído pelo cérebro, cerebelo e medula espinal, é responsável por funções como percepção, movimento e coordenação, enquanto o sistema nervoso periférico conecta o cérebro ao resto do corpo. Detalha também a estrutura dos neurônios e como estes transmitem sinais através de sinapses.
Physiology of Sleep and its correlation with EEG wavesABHILASHA MISHRA
Content includes Physiology of sleep and and its correlation with EEG waves along with specific characteristics of different phases of sleep as well as an account of sleep disorders.
O documento resume as principais divisões e estruturas do sistema nervoso humano em três frases:
1) O sistema nervoso é dividido em central e periférico, sendo o central composto pelo encéfalo e medula espinal e o periférico pelos nervos cranianos e raquidianos.
2) O encéfalo é constituído pelo cérebro, responsável pelas funções voluntárias e cognitivas, cerebelo responsável pelo equilíbrio, e tronco encefálico controlador de funções vitais como respiração
O documento discute os neurônios, as estruturas do neurônio, os tipos de neurônios, nervos, sinapses, a organização do sistema nervoso, o sistema nervoso autônomo, as meninges, o líquido cefalorraquidiano, o sistema nervoso central, ato reflexo e o efeito das drogas sobre o sistema nervoso.
The document summarizes the structure and function of the nervous system. It has two principal parts: the central nervous system (CNS), comprising the brain and spinal cord, and the peripheral nervous system (PNS) comprising nerves. The CNS integrates sensory input and dictates motor responses, while the PNS carries signals between the CNS and sensory receptors and effector organs. Neurons are the basic functional units and transmit signals via electrical impulses. Neuroglia provide support and insulation for neurons.
The document discusses ascending pathways in the spinal cord that transmit sensory information to the brain. There are two main pathways - the spinothalamic pathway carries pain and temperature sensations while the dorsal column pathway carries touch, proprioception, and vibration sensations. Both have three neurons with the first receiving input from receptors and synapsing in the spinal cord, the second carrying signals to the thalamus, and the third projecting to the somatosensory cortex. The cortex contains a sensory homunculus map of the body. Damage to ascending pathways can cause syndromes like Brown-Sequard.
O sistema nervoso é responsável pelo controle e regulação das funções corporais. É formado por neurônios que se comunicam através de sinapses. O sistema nervoso é dividido em central e periférico, sendo o central formado pelo encéfalo e medula espinhal e responsável pelas funções vitais e movimentos, enquanto o periférico inerva os órgãos e músculos.
The nervous system has 3 main functions: sensory input, integration, and motor output. It is divided into the central nervous system (CNS; brain and spinal cord) and peripheral nervous system (PNS). The PNS has sensory and motor divisions. The motor division is further divided into somatic and autonomic systems. Nervous tissue contains neurons and supporting cells like neuroglia. Neurons have dendrites, axons, and may be covered by a myelin sheath. Information passes between neurons at synapses. The brain is divided into the cerebrum, diencephalon, brain stem, and cerebellum. The special senses of smell, taste, vision, and hearing involve specialized receptors and
The nervous system consists of neurons and neuroglial cells. Neurons transmit nerve impulses through electrical and chemical signals. The neuron has a cell body, dendrites which receive signals, and an axon which transmits signals. Schwann cells wrap around axons and form myelin sheaths to insulate axons. Myelin allows faster impulse transmission. The nervous system regulates sensation, movement, and organ function through sensory, motor and interneurons. Nerve impulses rely on ion exchange and travel through the nervous system via pathways and reflex arcs.
What Makes School so Resistant to Change. The Wittgensteinian Approach.Pasi Vilpas
School is resistant to change because it is a societal and political entity focused on assessment and progression rather than learning. As a system that regulates students' advancement, education, careers, and social standing, school provides structure against alienation through standardized grading. This feedback loop makes reform difficult as modern societies depend on school's segregational services. Learning and schooling are separate concepts that cannot be discussed together sensibly, explaining school's resistance to change.
The cerebellum and basal ganglia play important roles in motor control and coordination. The cerebellum helps control the timing, smoothness, and intensity of muscle movements. It receives sensory feedback and compares actual movements to planned movements, sending corrections back to the motor system. The basal ganglia help plan and control complex patterns of muscle movement. The cerebellum has distinct input and output pathways and its Purkinje cells provide inhibitory signals that help regulate the output of deep nuclear cells and coordinate movement.
O documento descreve o sistema nervoso simpático, seus neurotransmissores e receptores. É detalhada a biossíntese, armazenamento e liberação da norepinefrina, assim como os tipos de receptores adrenérgicos e seus agonistas e antagonistas. Por fim, são explicadas as propriedades físico-químicas da norepinefrina e epinefrina e como modificações estruturais afetam a atividade dos fármacos adrenérgicos.
This document provides information about the circulatory system of a rat. It includes labeled diagrams showing the major arteries and veins of the rat. The text then provides instructions to trace various branches of arteries and veins, labeling key blood vessels like the aortic arch, abdominal aorta, renal arteries, inferior and superior vena cava, and hepatic vein. Checkboxes are included for the student to check off structures as they are located during the dissection.
The tropical cone snail hunts fish using a venomous harpoon-like tooth. Its venom acts extremely quickly, paralyzing prey within seconds through a mixture of toxins that disrupt neuronal signaling. Neurons communicate through electrical and chemical signals, and the cone snail venom interferes with both types of signaling. This prevents the prey's neurons from controlling locomotion and respiration, resulting in its inability to escape or survive the venom's effects.
The thalamus is a paired subcortical structure that relays sensory and motor signals to the cerebral cortex. It contains several nuclei that have specific connections to different regions of the cortex. The thalamus develops from the thalamic plate and differentiates into the epithalamus, dorsal thalamus, and ventral thalamus. The dorsal thalamus contains nuclei that project to the cortex via thalamocortical fibers. The thalamic reticular nucleus, part of the ventral thalamus, surrounds the dorsal thalamus and provides inhibitory input to it. The cerebral cortex is a laminated sheet of neurons involved in higher-level signal processing. It receives input from the thalamus and sends
B.Sc.(Micro+Biotech) II Animal & Plant Physiology Unit 4.1 Neurones & The Act...Rai University
Neurons have three main parts - the cell body, dendrites, and axon. Dendrites receive impulses and pass them to the cell body, while the axon sends impulses to other neurons. At rest, the neuron maintains an electrochemical gradient with more positive charges outside and negative inside. This gradient is maintained by active transport of ions against their concentration gradients. When stimulated, the neuron's membrane becomes permeable to sodium ions, causing depolarization and generating an all-or-none action potential if the threshold is reached. The action potential travels down the axon before the neuron enters refractory periods and returns to resting potential.
diaporama découverte des rythmes du sommeil
rôle du sport, caféine, sieste...
modification des rythmes chez la personne agée
consignes pour bien s'endormir
The document provides an overview of the autonomic nervous system (ANS). It discusses that the ANS is not under conscious control and regulates functions like blood pressure, heart rate, and gland secretion. It describes the two divisions of the ANS as the sympathetic and parasympathetic nervous systems. Key differences between the two divisions are described such as neurotransmitters, locations of ganglia, and effects on target organs. Examples of neurotransmitters, receptor types, and locations are outlined. Common drugs that target the adrenergic and cholinergic systems are also summarized along with their indications and actions.
This document provides information on nervous tissue and neurons. It discusses that nervous tissue consists of neurons and neuroglia. Neurons are specialized to receive sensory stimuli, process information, and transmit signals via nerve impulses. Neuroglia support and nourish neurons. The structure of neurons includes a cell body containing a nucleus, dendrites that receive signals, and an axon that transmits signals. Neurons are classified based on their structure and function. Synapses allow neurons to communicate via chemical or electrical signaling. The document also describes various sensory nerve endings and the stimuli they detect, as well as motor end plates that transmit signals to effector cells.
O documento descreve as funções e estrutura básica do sistema nervoso. O sistema nervoso é responsável por perceber estímulos ambientais e internos e elaborar respostas para adaptar o organismo às condições. A unidade básica é o neurônio, que conduz impulsos nervosos e se conecta a outros neurônios em cadeia. O sistema nervoso central processa informações e o periférico conduz informações entre órgãos e o cérebro.
O documento descreve a anatomia e o funcionamento do sistema nervoso central e periférico em humanos. Explica que o sistema nervoso central, constituído pelo cérebro, cerebelo e medula espinal, é responsável por funções como percepção, movimento e coordenação, enquanto o sistema nervoso periférico conecta o cérebro ao resto do corpo. Detalha também a estrutura dos neurônios e como estes transmitem sinais através de sinapses.
Physiology of Sleep and its correlation with EEG wavesABHILASHA MISHRA
Content includes Physiology of sleep and and its correlation with EEG waves along with specific characteristics of different phases of sleep as well as an account of sleep disorders.
O documento resume as principais divisões e estruturas do sistema nervoso humano em três frases:
1) O sistema nervoso é dividido em central e periférico, sendo o central composto pelo encéfalo e medula espinal e o periférico pelos nervos cranianos e raquidianos.
2) O encéfalo é constituído pelo cérebro, responsável pelas funções voluntárias e cognitivas, cerebelo responsável pelo equilíbrio, e tronco encefálico controlador de funções vitais como respiração
O documento discute os neurônios, as estruturas do neurônio, os tipos de neurônios, nervos, sinapses, a organização do sistema nervoso, o sistema nervoso autônomo, as meninges, o líquido cefalorraquidiano, o sistema nervoso central, ato reflexo e o efeito das drogas sobre o sistema nervoso.
The document summarizes the structure and function of the nervous system. It has two principal parts: the central nervous system (CNS), comprising the brain and spinal cord, and the peripheral nervous system (PNS) comprising nerves. The CNS integrates sensory input and dictates motor responses, while the PNS carries signals between the CNS and sensory receptors and effector organs. Neurons are the basic functional units and transmit signals via electrical impulses. Neuroglia provide support and insulation for neurons.
The document discusses ascending pathways in the spinal cord that transmit sensory information to the brain. There are two main pathways - the spinothalamic pathway carries pain and temperature sensations while the dorsal column pathway carries touch, proprioception, and vibration sensations. Both have three neurons with the first receiving input from receptors and synapsing in the spinal cord, the second carrying signals to the thalamus, and the third projecting to the somatosensory cortex. The cortex contains a sensory homunculus map of the body. Damage to ascending pathways can cause syndromes like Brown-Sequard.
O sistema nervoso é responsável pelo controle e regulação das funções corporais. É formado por neurônios que se comunicam através de sinapses. O sistema nervoso é dividido em central e periférico, sendo o central formado pelo encéfalo e medula espinhal e responsável pelas funções vitais e movimentos, enquanto o periférico inerva os órgãos e músculos.
The nervous system has 3 main functions: sensory input, integration, and motor output. It is divided into the central nervous system (CNS; brain and spinal cord) and peripheral nervous system (PNS). The PNS has sensory and motor divisions. The motor division is further divided into somatic and autonomic systems. Nervous tissue contains neurons and supporting cells like neuroglia. Neurons have dendrites, axons, and may be covered by a myelin sheath. Information passes between neurons at synapses. The brain is divided into the cerebrum, diencephalon, brain stem, and cerebellum. The special senses of smell, taste, vision, and hearing involve specialized receptors and
The nervous system consists of neurons and neuroglial cells. Neurons transmit nerve impulses through electrical and chemical signals. The neuron has a cell body, dendrites which receive signals, and an axon which transmits signals. Schwann cells wrap around axons and form myelin sheaths to insulate axons. Myelin allows faster impulse transmission. The nervous system regulates sensation, movement, and organ function through sensory, motor and interneurons. Nerve impulses rely on ion exchange and travel through the nervous system via pathways and reflex arcs.
What Makes School so Resistant to Change. The Wittgensteinian Approach.Pasi Vilpas
School is resistant to change because it is a societal and political entity focused on assessment and progression rather than learning. As a system that regulates students' advancement, education, careers, and social standing, school provides structure against alienation through standardized grading. This feedback loop makes reform difficult as modern societies depend on school's segregational services. Learning and schooling are separate concepts that cannot be discussed together sensibly, explaining school's resistance to change.
1. Kuuloaisti
Primaarisen kuuloaivokuoren (A1) rakenne ja toiminta
Primaarinen kuuloaivokuori sijaitsee ohimolohkon yläpinnalla, vasen on usein oikeata kookkaampi.
Täällä tapahtuu äänten aistimisen passiivinen osuus. Ääni-informaation varsinainen tulkinta tapahtuu
sekundaarisella kuuloaivokuorella (tämä sijaitsee primaarisen kuuloaivokuoren ympärillä).
Primaarinen kuuloaivokuori on painottunut äänen muutosten havainnoimiseen (pystyy siis hyödyntämään
koodin pakkaamista, kun muuttumattomana pysytteleviä osia ei tarvitse käsitellä).
Primaarisella kuuloaivokuorella on äänen taajuuksia (siis korkeutta) vastaava vyöhykkeisyys eli ns.
tonotooppinen rakenne (Kuva 1). Kussakin vyöhykkeessä on lisäksi äänen kestoajan mukaan aktivoituvia /
passivoituvia hermosoluja ainakin viisi eri tyyppiä (esim. lyhyt / pitkä ääni).
Eräät soluista lopettavat impulssien lähettämisen äänen ajaksi, osa taas toimii juuri päinvastoin eli lähettää
impulsseja äänen kuuluessa. Lisäksi primaarisella kuuloaivokuorella on soluja, joiden aktivoitumiskynnys
määräytyy äänen voimakkuuden perusteella.
Tonotooppinen rakenne (kuva 2) on myös simpukkatiehyen tyvikalvossa, kierteiselimen tumakkeessa
(Spiral ganglion), simpukan tumakkeessa (Cochlear nucleus) sekä MGN:ssä (Medial Geniculate Nucleus).
Tumakkeiden sijaintipaikat näkyvät kuvassa 6.
Niska
Nenä
Aistitun äänen korkeus kasvaa niskaa kohti siirryttäessä n. oktaavin / 2 mm.
Kolme
solukkojonoa,
kukin
erikoistunut
aistimaan eri
värisiä ääniä
Kuva 1. Vasemmanpuoleisen primaarisen
kuuloaivokuoren tonotooppinen rakenne (= kuulo-
aivokuoren ulkopinta yläpuolelta katsottuna
ohimolohkossa).
Kullakin vyöhykkeellä ainakin viisi
äänen pituuteen eri tavoin
reagoivaa solutyyppiä
2. Primaarinen kuuloaivokuori erittelee ääni-informaatiosta eri osatekijöitä ja lähettää ne ääniaivokuoren
sekundaarisiin (A2 – A6) osiin (samaan tapaanhan pelaa myös näköaivokuori): äänen eri piirteet aistitaan
aivokuoren eri osissa. Sekundaarinen kuuloaivokuori sijaitsee kuuloaivokuoren laitamilla (kuvat 3 ja 4).
Kuuloaivokuorelta viestejä lähtee myös takaisin väliaivojen alueelle. Edestakaista vuorovaikutusta siis on.
Kuva 3. Kuuloaivokuoren rakenne (kuvassa oikean ohimolohkon ylimmäinen
poimu). Primaarinen kuuloaivokuori (harmaa), sekundaarinen kuuloaivokuori
(pisteytetty). Henkilön kasvot osoittaisivat kuvassa oikealle, niska vasemmalle.
Kuva 2. Tonotopia kuulohermoradan eri osissa. Oliivitumaketta
(Superior olive), alempaa aivokukkulaa (Inferior colliculus) ja
MGN:ää ei ole merkitty kuvaan.
Simpukkatiehyen
tyvikalvo
karvasoluineen
Välittävien eli primaaristen
hermosolujen solukeskukset
kierteiselimen tumakkeessa
(Spiral Ganglion)
Simpukan tumake (Cochlear
nucleus) synapseineen
(ytimenjatkeessa)
1 KHz
4 KHz
16 KHz
3. Kuuloaistimuksen synty noudattaa seuraavaa reittiä (kuvat 5 ja 6)
1. Ulkokorva (korvatorvi ja tärykalvo)
2. Välikorva (kuuloluut: vasara, alasin, jalustin)
3. Sisäkorva (soikea ikkuna ja simpukka ohimoluun sisällä)
4. Simpukan keskikäytävän eli simpukkatiehyen ripsisolut Cortin elimessä
5. Sisäkorvan välittävät eli primaariset hermosolut. Nämä ulottuvat ripsisoluista ytimenjatkeessa oleviin
tumakkeisiin asti (kuva 6).
6. Sisäkorvassa simpukkatiehyen vieressä kierteiselimen eli Cortin elimen tumake Spiral ganglion
(täällä sijaitsevat välittävien hermosolujen solukeskukset).
7. Kuulohermo
8. Ytimenjatke (täällä sijaitsee simpukan tumake Cochlear ganglion. Tässä on kaksi osaa, dorsaalinen
ja ventraalinen Cochlear nucleus. Ytimenjatkeessa kuuloaistimuksen välittämiseen osallistuu myös
ylempi oliivitumake Superior olive. (Kuva 6)
9. Aivosillassa ylempi aivokukkula Inferior colliculus (kuva 6).
10. MGN eli Medial Geniculate Nucleus (tumake Hypotalamuksessa)
11. Kuuloaivokuori (ohimolohkon ylimmän poimun yläpinnalla)
Kummastakin korvasta kuulohermo haarautuu molempiin ohimolohkoihin. Haarautuminen tapahtuu
kuulohermotumakkeissa ytimenjatkeen alueella.
Kuuloaivokuori
Pikkuaivot
Ohimolohko
Kuva 4. Kuuloaivokuoren (= Auditory cortex)
sijainti ohimolohkon yläpoimun yläpinnalla.
4. 1
3
Kuva 5. Alla olevassa kuvassa 6 ylin
poikkileikkaus esittää kohtaa 1,
kohta 2 esittää aivosiltaa ja kohta 3
ytimenjatketta. Tämä on siis avain,
kun tulkitaan kuvaa 6.
2
5. Kuva 6. Ääni-impulssien eteneminen sisäkorvasta aivoihin (selitys tekstissä edellä).
Huomaa, että kuvaan on merkitty yhteydet vain toisen korvan osalta. Kuuloaivokuori
(= Auditory cortex) sijaitsee ohimolohkon ylimmän poimun yläpinnalla. Katso myös
kuvat 4 ja 5.
Cochlear
nucleus
Ohimo-
lohko
Päälaen-
lohko
Spiral ganglion
- sisältää välittävien eli
primaaristen
hermosolujen (kuva 8)
solukeskukset
Dorsal cochlear
nucleus
Ventral cochlear
nucleus
Superior
olive
Ytimenjatke
(= Pons)
Aivosilta (= Medulla)
Inferior colliculus
eli ylempi
aivokukkula
MGN
Kuulo-
aivo-kuori
6. Simpukan ja kierteis- eli Cortin elimen rakenne
Simpukassa on kolme päällekkäistä tiehyttä: eteiskäytävä, keskikäytävä (= simpukkatiehyt) ja
kuulokäytävä. Keskikäytävässä sijaitsee Cortin elin eli kierteiselin (kuvat 7 ja 8), jossa äänen
aiheuttamat impulssit ensimmäiseksi syntyvät.
Jos simpukka oikaistaisiin suoraksi, sijaitsisi Cortin elin keskikäytävän lattiassa. Lattiaa kutsutaan
tyvikalvoksi. Keskikäytävän katto (siis eteiskäytävän lattia) on nimeltään Reissnerin kalvo. Keskikäy-
tävässä sijaitsee vielä kolmaskin kalvo: Cortin elimeen kuuluva katekalvo. (Tsekkaile kuvat 7 ja 8)
Eteiskäytävä
Kuulokäytävä
Keskikäytävä eli
simpukkatiehyt
Cortin
elin (harmaa)
Tyvikalvo
Reissnerin kalvo
Helicotrema (eteiskäytävästä
kuulokäytävään johtava reikä
tyvikalvossa)
Keskikäytävän eli
simpukkatiehyen
pohjukka
Kuva 7. Sisäkorvassa sijaitsevan simpukan ja kierteiselimen eli
Cortin elimen rakenne (simpukka suoraksi oikaistuna).
Katekalvo
7. Simpukkatiehyen ripsisolut äänen vahvistajina
Ulompia ripsisoluja on simpukkatiehyessä kolme jonoa, mutta sisempiä ripsisoluja on vain yksi jono.
Tästä huolimatta Spiral ganglioniin saapuvista impulsseista peräti 95 % on peräisin sisemmistä
ripsisoluista.
Kuva 8. Cortin elimen eli kierteiselimen rakenne (poikkileikkaus). ripsisolut ovat
erikoistuneita hermosoluja. Kuhunkin niistä liittyy synapsiyhteydellä primaarinen eli
välittävä hermosolu. Primaaristen hermosolujen solukeskukset ovat Cortin elimen eli
kierteiselimen tumakkeessa (= Spiral ganglion). Tämä sijaitsee simpukan vieressä sen
ulkopuolella. Impulssit jatkavat matkaansa primaaristen hermosolujen aksoneita pitkin.
Tämä aksonikimppu eli kuulohermo on synapsiyhteydessä simpukan tumakkeeseen
(Cochlear nucleus). Simpukan tumake on ytimenjatkeessa.
Katekalvo
Tyvikalvo
Cortin sauvat
Sisemmät
ripsisolut (yksi
jono)
Cortin elimen eli kierteiselimen
tumake (Spiral ganglion).
Tumake sijaitsee simpukan
vieressä sen ulkopuolella.
Tumakkeessa sijaitsevat
primaaristen hermosolujen
solukeskukset.
Solukeskuksia
simpukan tu-
makkeessa
(Cochlear
nucleus). Tämä
sijaitsee
ytimenjatkeessa.
Primaaristen hermosolujen
tuojahaarakkeita
Reticular lamina
Ulommat
ripsisolut (3
jonoa koko
tyvikalvon
pituudelta)
Kuulo-
hermo
8. Ulompia ripsisoluja käytetäänkin enimmäkseen äänen vahvistamisessa. Nimittäin, korvasta aivoihin päin
vievien hermoratojen lisäksi ulompiin ripsisoluihin kytkeytyy myös paljon hermoratoja, joissa impulssit
kulkevatkin vastakkaiseen suuntaan: aivoista korvaan päin.
Ulompien ripsisolujen solukelmussa on proteiineja, jotka supistuvat aivoista saapuvien impulssien
vaikutuksesta. Tällöin ulommat ripsisolut lyhenevät. Samalla ne vetävät alapuolellaan olevia soluja (näitä
ei ole piirretty yllä olevaan kuvaan 8) itseensä päin. Tämä vetäminen tuntuu aina tyvikalvossa asti.
Tyvikalvon kohoaminen työntää puolestaan sisempiä ripsisoluja kohti katekalvoa, jolloin sisempien
ripsisolujen ripsett siirtyvät aivan katekalvon tuntumaan. Näin jo vähäinen tyvikalvon värinä (siis
hiljainenkin ääni) riittää synnyttämään niissä impulssin. Ulommat ripsisolut ovatkin tarpeen nimenomaan
silloin, kun kuulostellaan poikkeuksellisen tarkasti ja erityisen hiljaisia ääniä.
Impulssin synty kuuloreseptorisoluissa
Kuuloimpulssi syntyy kuuloreseptorisoluissa muista reseptorisoluista ja hermosoluista poikkeavalla
tavalla. Kun muissa solutyypeissä depolarisaatio tapahtuu natrium-ionien sisään syöksyessä,
kuuloreseptorisoluissa depolarisaation aiheuttaakin kalium (kuva 9).
Kuuloreseptorisolut kylpevät keskikäytävän sisällä olevassa nesteessä, endolymfassa. Siinä kaliumia on
runsaasti, mutta natriumia vähän. Kuuloreseptorisolujen sisällä kaliumpitoisuus on lepojännitteen aikana
endolymfaa alhaisempi. Solut hyödyntävät valmiin pitoisuuseron omassa depolarisaatiossaan. (Sen
sijaan eteis- ja kuulokäytävän sisältämä neste on perilymfaa, itse asiassa selkäydinnestettä, ja
perilymfassa on runsaasti natriumia ja kaliumia vähän. Tasapaino on siis juuri toisin päin.)
9. TUMA
Karvasolun
nukkalisäkkeitä
Kaliumkanava
Primaarisen eli
välittävän hermosolun
tuojahaarake
Välittäjäainemolekyylejä synapsiraossa
Välittäjäainemolekyylejä
sisältäviä kalvorakkuloita
+
+
++
+
+
Kalsiumia
syöksyy
sisään
Ca++
Kalsium-
ioneja
Ca++
Kaliumia on runsaasti
endolymfassa
(= keskikäytävän
sisältämässä nesteessä)
Kalium-
ioneja
K+
Kalium-ioneja
syöksyy soluun sisälle
Ca++
K+
K+
+
++
K+
Kalsiumia
syöksyy
sisään
Ca++
Ca++
Ca++
Kuva 9. Kuuloimpulssin synty. Kun kuuloreseptorisolujen nukkalisäkkeet (=ripset)
koskettavat Cortin elimen katekalvoa, niissä olevat kaliumkanavat avautuvat. Tällöin
kalium-ionit syöksyvät reseptorisolujen sisälle ja solu depolarisoituu.
Jännitteenmuutoksille herkät kalsiumkanavat avautuvat seuraavaksi, jolloin myös
kalsiumia syöksyy soluun sisälle. Tämän tuloksena välittäjäainerakkulat purkavat
sisältönsä synapsirakoon ja impulssi syntyy välittävässä eli primaarisessa hermosolussa.
Tuojahaarake päätyy Cortin elimen eli kierteiselimen tumakkeeseen (Spiral ganglion).
Impulssin syntytapa on poikkeuksellinen, sillä hermosoluissa yleensä natriumia on solun
ulkopuolella paljon, mutta kaliumia vähän. Kierteiselimen sisältämässä nesteessä
(=endolymfassa) sitä vastoin on paljon kaliumia, mutta vain vähän natriumia.