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1 Fisiologia Animal Organização+do+ sistema+ nervoso+ Silverthorn, Human physiology (2001) 2 ed. Vias+eferentes+ Silverthorn, Human physiology (2010) 5 ed. 2 Sistema+nervoso+somá6co+ Silverthorn, Human physiology (2010) 5 ed. Sistema+nervoso+autónomo+ (sistema+parassimpá6co)+ Silverthorn, Human physiology (2010) 5 ed. 3 Sistema+nervoso+autónomo+ (sistema+simpá6co)+ Silverthorn, Human physiology (2010) 5 ed. Sistema+ nervoso+ autónomo+ 4 Fisiologia Animal + + Músculos+e++ movimento+animal+ Fisiologia Animal Movimento+ • O#que#permite#o#movimento#dos#animais?# – Músculos?# • E#nos#seres#unicelulares?# – Cílios#e#flagelos# 5 Fisiologia Animal Microtúbulos,+microfilamentos+e+ movimento+celular+ • Dois#componentes#do#citoesqueleto#são#capazes#de#gerar# movimento:# – Microtúbulos# – Microfilamentos# ## # # Fisiologia Animal α β Tubulin#dimer## βDTubulin#monomer# αDTubulin#monomer# C+End# ++ End# Microtúbulos+ • Tubos#ocos#consEtuídos#por#tubulina+ • Tubulina#é#consEtuída#por#2# subunidades:# – βDtubulina# – αDtubulina# • Principais#funções:# – Formam#um#esqueleto#interno# – Envolvidos#na#divisão#celular# 6 Fisiologia Animal Microtúbulos+ • Microtúbulos#também#originam#dos#cílios#e#flagelos.# – Cílios#e#flagelos#são#estruturas#citoplasmáEcas#anexas#à# membrana# plasmáEca# das# células,# tendo# origem# a# parEr# do# prolongamento# dos# centríolos,# consEtuídos# de# proteínas# motoras# (dineínas)# formando# um# conjunto#de#microtúbulos.## – Cílios:#mais#curtos#e#em#maior#quanEdade#na#superVcie# da#célula;# – Flagelos:#mais#longos#e#geralmente#pouco#numerosos.## ## • Muitos#proEstas#e#pequenos#invertebrados#uElizam# cílios#para#a#sua#locomoção.# • Animais#uElizam#os#cílios#para#movimentar#fluidos#e# parYculas#sobre#determinadas#superVcies.## • Nos#humanos:# – os#cílios#removem#detritos#das#vias#respiratórias# – Os#flagelos#permitem#o#movimentos#dos# espermatozóides# Fisiologia Animal Microfilamentos+ • Microfilamentos#são# proteínas#que#geram#forças# contrácteis#através#da# alteração#da#sua# conformação## • Principais#funções:# – Movimento# – Dar#forma#à#célula# Monómeros de actina 7 Fisiologia Animal Microfilamentos+ • A#principal#proteína#é#a#acEna.# • As#microvilosidades#intesEnais##e#os#estereocílios#das#células# ciliadas#são#manEdos#por#microfilamentos#de#acEna# • O#processo#de#endocitose#também#depende#da#acEna#e# miosina# Histology:##A#Text#and#Atlas,#4th#ed.# Fisiologia Animal Tipos+de+músculos+ • Músculo#cardíaco# – BaEmento#cardíaco#e#bombeamento# do#sangue# # • Músculo#liso# – Movimentos#da#parede#do#tubo# digesEvo# – Fluxo#de#sangue#nos#vasos# – Esvaziamento#da#bexiga# – Contracção#uterina#durante#o#parto# • Músculo#esqueléEco# – Movimento#corporal# – Manutenção#da#postura# – Respiração# – Produção#de#calor# – Comunicação# • Falar,#escrever,#gesEcular,#expressões# faciais…# 8 Fisiologia Animal Músculos++ • Todos#os#Epos#de#músculos#possuem# microfilamentos?# • ConsEtuídos#por?# – ACTINA# – MIOSINA## Músculo+esquelé6co+ Tendão+ Tecido+conjun6vo+ Nervos+e+ Vasos+sanguíneos+ Músculo+esquelé6co+ Feixe+de+fibras+ musculares+ Tecido+ conjun6vo+ Núcleo+ Fibra+muscular+ 9 Músculo+ esquelé6co+ Fisiologia Animal Como+os+músculos+contraem?+ • Modelo#do#deslizamento#dos#filamentos# http://www.wiley.com/college/pratt/0471393878/student/animations/ actin_myosin/actin_myosin.swf 10 Fisiologia Animal O+que+origina+a+contração+do+músculo+ esquelé6co?++ • Iniciado#por#PA#conduzidos#por#neurónios# motores# • Cada#neurónio#motor#pode#estabelecer# sinapses#com#várias#fibras#musculares.# – Unidade#motora:#conjunto#de#fibras# musculares#controladas#por#um#neurónio# motor# • Libertação#de#ACh#na#junção#neuroD muscular# • ACh#induz#a#geração#de#um#PA#na#fibra# muscular# • PA#esEmula#a#libertação#de#Ca2+#do#RS# • Ca2+#combina#com#a#troponina#e#inicia#a# contração# Fisiologia Animal Acoplamento+excitação+contração+ 11 Fisiologia Animal Acoplamento+excitação+contração+ Fisiologia Animal Acoplamento+excitação+contração+ Figure 12-11b: Excitation-contraction coupling 12 Fisiologia Animal Relaxamento+muscular+ • Ocorre#quando#o#Ca2+#é# transportado#aEvamente#para#o# interior#do#RS# – Implica#dispêndio#de#energia# (ATP)# • [Ca2+]#no#sarcoplasma#diminui,#o# que#origina#a#libertação#do#Ca2+# da#troponina# • O#complexo#tropononaD tropomiosina#restabelece#a#sua# posição,#bloqueando#os#locais# aEvos#das#moléculas#de#acEna# • Fibra#relaxa# Fisiologia Animal Acoplamento+excitação+contração+ 13 Fisiologia Animal 3. Sarcómeros activos 2. Libertação de Ca 2+ 1. Potencial de ação Potencial de ação Ciclo contractivo Níveis de Ca 2+ no citoplasma Tempo (mseg) Marieb (1997) Human Anatomy & Physiology (4ª ed .) Relação+temporal+da+contração+com+ o+potencial+de+ação+e+a+elevação+no+Ca2++na+ célula+muscular+ + Fisiologia Animal Velocidade+de+contração++ a) Extraocular# b) Gémeos# c) Solhar# 14 Fisiologia Animal Caracterização+das+fibras+ musculares+esquelé6cas++ Características Tipo I Tipo IIA Tipo IIB Contrácteis Velo. Contracção Lenta Rápida Rápida Actividade da ATPase Lenta Rápida Rápida Duração ciclo contractivo Longo Curto Curto Recaptação do Ca2+ Lenta Rápida Rápida Metabólicas Capilares Abundantes Intremédios Raros Capacidade glicolitica Baixa Média Elevada Capacidade oxidativa Elevada Elevada Baixa Conteúdo em mioglobina Elevado Médio Baixo Conteúdo em glicogénio Baixo Médio Elevado Diâmetro Pequeno Médio Grande Fisiologia Animal Tipos+de+fibras+musculares+ 15 Fisiologia Animal Músculo+esquelé6co+e+movimento+ • Os#músculos#apenas#contraem#e#relaxam# • Para#criar#movimento,#necessitam#de#puxar#algo:# – Outros#músculos:#tromba#do#elefante# – Esqueleto# • Esqueleto#hidrostáEco# – Presente#em#cnidários,#anelídeos#e# outros#invertebrados# – ConsEtuído#por#fluido#conEdo#numa# cavidade#corporal#rodeada#por# musculo# – Contracção#muscular#aperta#o#fluido#e# faz#deslocar#o#corpo#do#animal#numa# determinada#direcção# Fisiologia Animal Músculo+esquelé6co+e+movimento+ • Exoesqueleto# – Músculos#estão#ligados#internamente# ao#exoesqueleto# – Contração#dos#músculos#permite#que# segmentos#arEculados#do# exoesqueleto#se#movam# • Endoesqueleto# – Músculos#estão#ligados#por#tendões# ao#esqueleto# – Contração#e#relaxamento#dos# músculos#permite#o#movimento# 16 Fisiologia Animal Neurónios+motores+ Sistema#nervoso#somáEco# Neurónio#motor# Músculo+ ACh+ nAChR+ • EsEmulam#a#contracção#muscular# • AcEvidade#controlada#por:# – Informação#proveniente#de#músculos#e#tendões# – Efeitos#facilitadores#ou#inibidores#do#cérebro# Fisiologia Animal 17 Fisiologia Animal Fuso+muscular+ Neurónio motor γ$ Neurónio motor γ$ Neurónio sensorial$ Fibra extrafusal$ Fibra intrafusal$ Fuso muscular$ Zona central sem miofibrilhas$ Silverthorn (2001) Human physiology (2 ed.) Fisiologia Animal Tónus+muscular+ Silverthorn (2001) Human physiology (2 ed.) 18 Fisiologia Animal Função+do+fuso+muscular+ Silverthorn (2010) Human physiology (5 ed.) Fisiologia Animal Reflexo+ • Resposta#automáEca#aos#esYmulos#que# ocorrem#sem#pensamento#consciente# 19 Fisiologia Animal Reflexo+de+Extensão+ Silverthorn (2001) Human physiology (2 ed.) Contracção#do#músculo#em#resposta#a#uma#força#de#esEramento#que#lhe#é#aplicada#Fisiologia Animal Reflexo+de+Extensão+ Bear et al (1995) Neuroscience: Exploring the Brain Peso Comprimento do músculo Neurónio sensorial Ia Neurónio motor α Peso Neurónio motor α Neurónio sensorial Ia 20 Fisiologia Animal CoCac6vação+dos+neurónios+motores+α+e+γ+ Bear et al (1995) Neuroscience: Exploring the Brain α Ia γ α activado Fibra extrafusal Fibra intrafusal γ activado α - neurónio motor α Ia - neurónio sensorial Ia γ - neurónio motor γ Fisiologia Animal Órgão+tendinoso+de+Golgi+ Neurónio sensorial# Neurónio aferente# Fibras extrafusais# Cápsula# Tendão# Fibra de colagénio# Silverthorn (2001) Human physiology (2 ed.) 21 Fisiologia Animal Reflexo+de+Golgi+ Silverthorn (2001) Human physiology (2 ed.) Fisiologia Animal Reflexo+patelar+ Silverthorn (2001) Human physiology (2 ed.) 22 Fisiologia Animal Reflexo+ flexor+de+ re6rada+ Reflexo+ Extensor+ cruzado+ Fisiologia Animal Modulação+dos+movimentos+ reflexos+ 23 Fisiologia Animal Movimentos+ • Reflexos# – Integrados#na#medula#espinhal# – Iniciados#por#esYmulos#externos# • Voluntários# – Requer#integração#ao#nível#do#córtex# – Iniciados#sem#esYmulos#externos# • Rítmicos# – Combinação#de#mov.#reflexos#e#voluntários# – Iniciados#e#terminados#através#de#informação#proveniente#do# córtex# – ManEdos#por#interneurónios#espinhais# Fisiologia Animal Locomoção+ Berne & Levy (1995) Principles of Physiology (2ª Ed) Mesencephalic locomotor region Extensors Flexors Stance Swing Treadmill Nerves to forelimbs Nerves to hindlimbs 24 Fisiologia Animal Circuito+da+a6vidade+rítmica+alternada+dos+músculos+ flexores+e+extensores+durante+a+locomoção+ Bear et al (1995) Neuroscience: Exploring the Brain Interneurónio excitador Interneurónio excitador Interneurónios inibidores Neurónio motor p/ extensor Neurónio motor p/ flexor ‘Input’ central Fisiologia Animal Centros+de+controlo+do+movimento+ Silverthorn (2001) Human physiology (2 ed.) 25 Fisiologia Animal A6vidade+cerebral+ Simple finger flexion (performed) Somatic sensory cortex Motor cortex Purves et al. (1997) Neuroscience Finger movement sequence (performed) Supplementary motor cortex Finger movement sequence (mental rehearsal) Fisiologia Animal Áreas+do+córtex+cerebral+envolvidas+na+programação+dos+ movimentos Kandel et al. (1995) Essentials of Neural Science and Behavior Córtex parietal posterior Córtex somatossensorial primário Córtex motor primário Córtex motor suplementar Córtex pré-motor 26 Fisiologia Animal Controlo+motor+pelos+gânglios+da+base+ Pré-motor e suplementar Prefrontal Motor primário Somatossensorial Tálamo Subtálamo Substância negra Putamen Globo pálido Fisiologia Animal Controlo+motor+pelo+cerebelo+ Córtex motor Cerebelo Músculos Tálamo 27 Fisiologia Animal Controlo+neuronal+do+movimento+ Silverthorn (2001) Human physiology (2 ed.) Fisiologia Animal Vias+descendentes+do+córtex+motor+ para+os+neurónios+motores+da+medulaCespinhal+ Berne & Levy (1995) Principles of Physiology (2ª Ed) Directas Indirectas Feixes piramidais ou cortico-espinhais Feixes extra-piramidais 28 Fisiologia Animal Feixes+piramidais+ Fox (2012) Human physiology (12 ed.) Figure 8.26 The higher motor neuron control of skeletal muscles. The pyramidal (corticospinal) tracts are shown in pink and the descending motor pathways from the brain stem that are controlled by the extrapyramidal system are shown in black. released by the nigrostriatal pathway (as previously dis- cussed), are often referred to medically as “extrapyramidal symptoms.” These symptoms demonstrate that the extra- pyramidal system is needed for the initiation of body move- ments, maintenance of posture, control of the muscles of facial expression, and other functions. The term extrapyramidal can be understood in terms of the following experiment: If the pyramidal tracts of an exper- imental animal are cut, electrical stimulation of the cerebral cortex, cerebellum, and basal nuclei can still produce move- ments. The descending fibers that produce these movements must, by definition, be extrapyramidal motor tracts. The regions of the cerebral cortex, basal nuclei, and cerebellum that participate in this motor control have numerous synap- tic interconnections, and they can influence movement only indirectly by means of stimulation or inhibition of the nuclei that give rise to the extrapyramidal tracts. Notice that this motor control differs from that exerted by the neurons of the Primary motor area of cerebral cortex Internal capsule Thalamus Skeletal muscle Anterior corticospinal tract Lateral corticospinal tract Cervical spinal cord Lumbar spinal cord Medulla oblongata Pyramid Figure 8.25 Descending corticospinal (pyramidal) motor tracts. These tracts contain axons that pass from the precentral gyrus of the cerebral cortex down the spinal cord to make synapses with spinal interneurons and lower motor neurons. precentral gyrus, which send fibers directly down to the spi- nal cord in the pyramidal tracts. The reticulospinal tracts are the major descending pathways of the extrapyramidal system. These tracts originate in the reticular formation of the brain stem, which receives either stimulatory or inhibitory input from the cerebrum and the cerebellum. There are no descending tracts from the cer- ebellum; the cerebellum can influence motor activity only indirectly by its effect on the vestibular nuclei, red nucleus, and basal nuclei (which send axons to the reticular forma- tion). These nuclei, in turn, send axons down the spinal cord via the vestibulospinal tracts, rubrospinal tracts, and reticulo- spinal tracts, respectively ( fig. 8.26 ). Neural control of skel- etal muscle is explained in more detail in chapter 12. CLIN ICAL APPL ICATION The corticospinal tracts appear to be particularly important in voluntary movements that require complex interactions between sensory input and the motor cortex. Speech, for example, is impaired when the corticospinal tracts are damaged in the tho- racic region of the spinal cord, whereas involuntary breathing continues. Damage to the pyramidal motor system can be detected clinically by the presence of Babinski’s reflex, in which stimulation of the sole of the foot causes extension of the great toe upward and fanning of the other toes. (In normal adults such stimulation causes the plantar reflex, a downward flexion, or curl- ing, of the toes.) Babinski’s reflex is normally present in infants because neural control is not yet fully developed. 231The Central Nervous System fox78119_ch08_203-238.indd 231fox78119_ch08_203-238.indd 231 09/07/10 2:54 PM09/07/10 2:54 PM Fisiologia Animal Feixes+extrapiramidais+ Fox (1999) Human physiology (6 ed.) 29 Fisiologia Animal Músculo+liso+ • As#células#musculares#lisas#são#as#mais# simples:# – Possuem#um#único#núcleo# – Forma#fusiforme# Fisiologia Animal Tipos+de+músculos+lisos+ Unidade simples (visceral)$ Multiunitário$ • Tubo digestivo • Aparelho reprodutor • Aparelho urinário • Pequenos vasos$ • Íris • Grandes vasos • Sistemas respiratório • Pêlos$ Tem gap-junctions Sinapses “en passant” Não tem gap-junctions Sinapses “en passant” Single-unit smooth muscle Digestive tract Varicosity Varicosity Gap junctions Smooth muscle cell Multiunit smooth muscleEye Autonomic neuron Synapses en passant Autonomic neuron Synapses en passant Figure 12.37 Single-unit and multiunit smooth muscle. In single-unit smooth muscle, the individual smooth muscle cells are electrically joined by gap junctions, so that depolarizations can spread from one cell to the next. In multiunit smooth muscle, each smooth muscle cell must be stimulated by an axon. The axons of autonomic neurons have varicosities, which release neurotransmitters, and which form synapses en passant with the smooth muscle cells. Only some cells of single-unit smooth muscles receive autonomic innervation, but the ACh released by the axon can diffuse to other smooth muscle cells. Binding of ACh to its muscarinic receptors causes depolarization by closing K + channels, as described in chapter 9 (see fig. 9.11). Such stimulation, however, only modifies the automatic behavior of single-unit smooth muscles. Single-unit smooth muscles display pacemaker activity, in which certain cells stimulate others in the mass. This is similar to the situation in cardiac muscle. Single-unit smooth muscles also display intrinsic, or myogenic, electrical activity and contraction in response to stretch. For example, the stretch induced by an increase in the volume of a ureter or a section of the digestive tract can stimulate myogenic contraction. Such contraction does not require stimulation by autonomic nerves. Contraction of multiunit smooth muscles, by contrast, requires nerve stimulation. Multiunit smooth muscles have few, if any, gap junctions. The cells must thus be stimulated individually by nerve fibers. Examples of multiunit smooth muscles are the arrector pili muscles in the skin and the cili- ary muscles attached to the lens of the eye. Case Investigation CLUE Maria was taking a calcium-channel-blocking drug to treat her hypertension (high blood pressure). ■ How does a calcium-channel-blocking drug affect the smooth muscle of blood vessels and the blood pressure? Single-Unit and Multiunit Smooth Muscles Smooth muscles are often grouped into two functional cat- egories: single-unit and multiunit ( fig. 12.37 ). Single-unit smooth muscles have numerous gap junctions (electrical synapses) between adjacent cells that weld them together electrically; they thus behave as a single unit, much like car- diac muscle. Most smooth muscles—including those in the digestive tract and uterus—are single-unit. 392 Chapter 12 fox78119_ch12_355-399.indd 392fox78119_ch12_355-399.indd 392 05/07/10 7:26 PM05/07/10 7:26 PM Single-unit smooth muscle Digestive tract Varicosity Varicosity Gap junctions Smooth muscle cell Multiunit smooth muscle Eye Autonomic neuron Synapses en passant Autonomic neuron Synapses en passant Figure 12.37 Single-unit and multiunit smooth muscle. In single-unit smooth muscle, the individual smooth muscle cells are electrically joined by gap junctions, so that depolarizations can spread from one cell to the next. In multiunit smooth muscle, each smooth muscle cell must be stimulated by an axon. The axons of autonomic neurons have varicosities, which release neurotransmitters, and which form synapses en passant with the smooth muscle cells. Only some cells of single-unit smooth muscles receive autonomic innervation, but the ACh released by the axon can diffuse to other smooth muscle cells. Binding of ACh to its muscarinic receptors causes depolarization by closing K + channels, as described in chapter 9 (see fig. 9.11). Such stimulation, however, only modifies the automatic behavior of single-unit smooth muscles. Single-unit smooth muscles display pacemaker activity, in which certain cells stimulate others in the mass. This is similar to the situation in cardiac muscle. Single-unit smooth muscles also display intrinsic, or myogenic, electrical activity and contraction in response to stretch. For example, the stretch induced by an increase in the volume of a ureter or a section of the digestive tract can stimulate myogenic contraction. Such contraction does not require stimulation by autonomic nerves. Contraction of multiunit smooth muscles, by contrast, requires nerve stimulation. Multiunit smooth muscles have few, if any, gap junctions. The cells must thus be stimulated individually by nerve fibers. Examples of multiunit smooth muscles are the arrector pili muscles in the skin and the cili- ary muscles attached to the lens of the eye. Case Investigation CLUE Maria was taking a calcium-channel-blocking drug to treat her hypertension (high blood pressure). ■ How does a calcium-channel-blocking drug affect the smooth muscle of blood vessels and the blood pressure? Single-Unit and Multiunit Smooth Muscles Smooth muscles are often grouped into two functional cat- egories: single-unit and multiunit ( fig. 12.37 ). Single-unit smooth muscles have numerous gap junctions (electrical synapses) between adjacent cells that weld them together electrically; they thus behave as a single unit, much like car- diac muscle. Most smooth muscles—including those in the digestive tract and uterus—are single-unit. 392 Chapter 12 fox78119_ch12_355-399.indd 392fox78119_ch12_355-399.indd 392 05/07/10 7:26 PM05/07/10 7:26 PM 30 Fisiologia Animal Músculos+lisos+ The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again. Fibra muscular lisa$ Varicosidades$ Gap junctions$ Músculo liso de unidades simples (visceral)$ Músculo liso multiunitário$ Vander (2000) Human Physiology (8ª ed.) Fisiologia Animal Músculo+liso+ 31 Fisiologia Animal Músculo+liso:+mecanismo+de+contração+ Figure 12-28: Smooth muscle contraction! Fisiologia Animal Figure 12-29: Relaxation in smooth muscle Músculo+liso:+mecanismo+de+ relaxamento+ 32 Fisiologia Animal Alteração+do+potencial+de+membrana+ nas+células+musculares+lisas+ The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again. The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again. Tempo$ Potencial de acção$ Potencial pacemaker$ Potencial limiar$ Po te nc ia l d e m em br an a (m V) $ Vander (2000) Human Physiology (8ª ed.) Fisiologia Animal Músculo+Cardíaco+ • Contém#filamentos#de#acEna# e#miosina##organizados#em# sarcómeros.# • Contraem#por#um#mecanismo# de#interdigitação#e#deslize#dos# filamentos.# • As#células#miocardiais# adjacentes#unemDse#por#“gap# juncEons”.# – Os+potenciais+de+ação+ propagamCse+no+músculo+ cardíaco+através+das+“gap+ junc6ons”.+ – O+músculo+cardíaco+contrai+ como+um+todo.+ 33 Fisiologia Animal Junções espaçados
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