- 14 Sep 2015 20:18
#14599614
HISTORY
5000 years ago the ancient Egyptians believed that the heart was the seat of the mind.
Hippocrates wrote that the brain was the seat of knowledge and memory.
Aristotle believe that the heart was the seat of knowledge and the brain merely cooled the blood and determined temperament.
Galen 130-200 AD found fluid filled ventricles in the brain by dissecting sheep. He proposed that the cerebrum stored sensation and memory and the cerebellum controlled muslce movements. Created the fluid mechanical theory that fluid from the ventricals was pumped down hollow tubes similar to blood vessels to inflate muscles.
Andreas Vesalius (1514-1564) was an anatomist that drew detailed structures of the brain.
Descartes reasoned that humans not animals have a mind sperate from the brain.
By the end of the 18th century the nervous system was seperated into the basic divisions of the central nervous system (CNS) and the peripheral nervous system (PNS).
1798 Galvani discovers the electrical nature of nervous activity, nerves were not tubes but wires.
1810 Bell and Magendie propose sensory and motor fibers and start the general use of experimental ablation method. The practice of studying the effects of damaging a part of the brain to determine it's function.
The idea of localized function in different areas of the brain begins taking root.
by the end of the 19th century it was understood that:
Spinal roots carry functional information, the cerebellum is the origin of motor fibers, and the cerebrum is the destination of sensory fibers.
Paul Broca studied patients with speech loss and discovered the discrete region that controls human speech (Broca's area).
Neuron Doctrine: Each nerve cell is a distinc genetic and anatomical unit with axons and dendrites that have distinct endings (proposed by Waldheyer in 1891).
The Neuron doctrine was proven after the staining of neurons and processes by Golgi and Cajal.
eticular theory: Disproven theory that axons and dendrites form a continuous network.
20th century neuroscience.
1920s Langley, Loewi, Dale, and others identify neurotransmitters that function as chemical messengers between neurons.
1940s Shannon, Weaver, and Weiner introduce concepts of information processing and control systems (cybernetics)
1950s Hodgkin, Katz, and Eccles make precise recoding of electrical signals with microelectrodes. Electron microscompy reveals synapses and neuronal fine structure. Single cell analysis reveal brain circuits for feature abstraction.
1960s Integrative functions of dendrites are recognized: synaptic circuts and synaptic interactions without impulses are identified.
1970s Neuromodulator substances and second messengers are found that greatly extend the duration and complexity of neuronal interactions. Computerized imaging techniques permit visualization of brain activity in relation to sensation and cognition. Molecular methods are introduced for analyzing genetic mechanisms. Society of neuroscience established.
2000s Neuron stem cell discovered.
CELLS OF THE NERVOUS SYSTEM
Neurons: Reside in grey matter in nuclei and ganglia
Glia: Reside in grey and white matter.
Oligodendrocytes in CNS
Astrocyte in CNS
Schwann cell in PNS
Microglia: carry out immune function
Ependymal cells: Line ventricales
Meningial cells: cover brain and spinal cord.
Neuron classifications:
By shape:
Unipolar
Bipolar
Multipolar
by major neurotransmitter:
Dopaminergic
Adrenergic
Cholinergic
by function:
Motor, snesory, sympathetic, etc.
Projection, interneuron.
Parts of the neuron:
Soma: cell body of neuron, contains nucleus
Axon: long fiber which carried information to other neurons.
Dendrite: recieves information from other neurons
Dendritic spine: Receives information at a single synapse.
Glial cells: 5-10X more abundant than neurons
Astrocyte, oligodendrocyte, Schwann cell, Microglial cell, Ependymal Cells.
Oligodendrocyte: Present only in the CNS, found mostly in white matter, mylenates large diameter axons in the CNS.
Schwann cell: Present only in the PNS, mylenates axons, participates in development and regeneration of the PNS.
Astrocyte: Protoplasmic found in grey matter, Fibrous found in white matter. Regulates CNS metabolism and extracellular ion concentrations. Plays important role at the synapses.
Brain organization
Divisions of the nervous system:Central nervous system (CNS), Peripheral nervous system (PNS), autonomic nervous system (ANS).
CNS: Brain= Cerebrum, cerebellum, brain stem. Spinal cord.
Cerebrum: Cerebral hemispheres right and left. Four lobes per hemisphere; Frontal, parietal, occipital, and temporal.
Deep structures of the cerebrum: Basal ganglia and thalamus.
Neocortex: allows for human functions; Learning, reasoning, intention, desires, and the "mind".
Gyrus and sulcus.
Gyrus- folds on surface of brain.
Sulcus = Grooves on brain's surface.
Increases surface area of neocortex to accomodate more neurons without increasing brain size.
Cerebral hemispheres: Right hemisphere contols left side motor and sensory functions. Involved in spatial reasoning and parallel processing.
Left hemisphere contols right side motor and sensory, involved in logical reasoning.
In most humans left cerebral cortex controls language.
Frontal lobes process conscious control of movement, behavior, and personality.
Parietal lobes processes sensory information from muscle and skin.
Temporal lobes are involved in processing hearing and language.
Occipital lobes involved in vision.
Nuclei: Collection of neuronal somas located deep in the brain.
Meninges: seperated into three layers Dura mater outside, arachnoid in the middle, and pia mater at the brains surface.
Ventricals: Lateral ventricals (anterior and posterior horns), Third ventrical (at the level of the thalamus), and fourth ventricle (at the level of the pons and cerebellum)
Ventricles are filled with cerebral spinal fluid (CSF)
Choroid Plexus: specialized tissue in ventricals that secretes CSF. CSF reabsorbed by the subarachnoid space. CSF flows from the cerebrum, brain stem cores, subarachnoid space, special structures called arachnoid villi that absorb csf.
Secreted by choroid plexus on the floor of the lateral ventricals. Brain floats in CSF.
Midbrain: Functions in visual and auditory orientation reflexes, maintaining posture, and voluntary movements of body and face, pain.
Contains nuclei for cranial nerves 3 (ocularmotor), 4 (trochlear), and 6 (abducens).
A thouroughfare for axons entering and leaving the brain.
Pons: Regulates respiration, thoroughfare for motor and sensory fibers, controls movements of the face and jaw muscles, eye movements, and sensation to face. Also regulates sleep.
contains nuclei for cranial nerves 5 (trigeminal), and 7 (facial).
Trigeminal, abducesn, fascial, and vestibulochoclear nerves run through it.
Medulla Oblongata: Caudal portion of brainstem, leads to spinal cord. Contains nuclei for cranial nerves 7-12. Involved in speech, swallowing, moving neck, shoulder muscles, salivation, taste, hearing, balance, mood, alertness, respiration, heart rate. Throughfare for somatic afferent and efferent fibers from brain to spinal cord.
Motor modulation systems: Cerebellum, involved in controlling movements by sequentially activating muscles. Basal ganglia, involved in voluntary beginning and ending movements.
Cerebellum: Derived from hindbrain but not part of brain stem. Connected to pons and Medulla by cerebellar peduncles that are made up of axons entering and leaving the cerebellum. 4th ventrical seperates it from the brain stem.
Coordinates muscle activity and plans complex movements. Involved in learning and memory of motor tasks. Posture, keeps muslce tone during voluntary movement and reflexes. Equilibrium. Spatial reasoning.
Right and left hemispheres. Unlike cerebrum, system is uncrossed (the right side of the cerebellum controls the right side of the body)
Cerebellar lobes: Anterior lobe, Posterior lobe, vermis, Flocculondular.
Anterior lobe: Unconcious Proprioception.
Posterior lobe: Fine motor coordination.
Flocculonodular lobe: Eye tracking and movement of eyes in relation to head position and movement.
Vermis: Body posture and locomostion
Deep cerebellar Nuclei: Emboliform, Dentate, Globose, Fastigial. Main output neurons from cerebellum into spinal cord to innervate motor neurons in the ventral horn.
Deep Brain nuclei: Basal Ganglia-Striatum, 3 forebrain nuclei invovled in motor control. Diencephalon, Processing sensory and motor information and endocrine role. Limbic system, involved in regulating emotion, motivation, and homeostasis.
Basal Ganglia: Nuclei surrounding Thalamus with common function, 3 components. Putamen, globus pallidus, caudate nucleus (aka striatum). Substantia nigra. Subthalamic nuclei.
Planning of coluntary movement including starting and stopping a movement and tone of antigravity muscles.
Diencephalon: Anterior to the midbrain and forms the walls of the third ventricle. Consists of two parts the thalamus and the hypothalamus.
Thalamus : processes sensory information, relays motor information.
Hypothalamus: Part of limbic system, controls the pituitary gland.
Thalamus: divided into 6 nuclei. Relay for afferent information traveling to cortical regions. Several nuclei receive information from optic nervs. Other nuclei recieve auditory and motor information.
Hypothalamus: Involved in maintaining homeostasis of your bodily functions, controls body temperature, blood pressure, salt and water levels. Initiates and suppresses eating and drinking. Activates and inhibits pitutitary gland. Involved in emotional responses tha tchange blood pressure, heart rate, respiration, blushing, and sweating.
Limbic system: Regulates visceral motor functions, emotions, memory, and olfaction.
Cranial nerves.
1. olfactory
2. optic
3. occularmotor
4. trochlear
5. trigeminal
6. abducens
7. facial
8. vestibularchochlear
9. glossopharyngeal
10. vagus
11. accesory
12. hypoglossal.
Brainstem: 3 primary vessivals develop from neural tube Forebrain, midbrain, and hindbrian. Midbrain derived form mesenchepalon. Pons derived with cerebellum from metenchephalon. Medulla oblangata derived from the myencephalon
SPINAL CORD AND PNS
Major concepts: spinal cord is shorter than the vertebral column cauda equina is the spinal roots travaling down the subarachnoid space until the correct vertebra to exit. Spinal cord grey matter is central, white matter in peripheral. Dorsal= sensory, ventral = motor. Primary motor neurons are in ventral spinal cord; primary sensory neurons are in dorsal root ganglia.
Dorsal horn and columns, sensory. Ventral horn and columns, motor. Spinal canal. Dorsal rootlets, roots, and ganglia. Ventral rootlets and roots. Spinal pia mater, arachnoid, and dura mater. Cauda equina.
8 cervical spinal cord levels between cervical vertabra 1-7 give rise to 8 cervical nerves c1-c8.
12 Thoracic spinal cord levels T!-T12.
5 Lumbar spinal cord levels L1-L5.
5 Sacral spinal cord levels, L1-L5
1 Coccygeal nerve.
Lateral Horns: Only at lower toracic and upper lumbar levels and contain autonomic sympathetic neuronal somas. Also called the inermediolateral cell collumn in the grey matter of the spinal cord.
Interneuron is another name for an association neuron. Primary motor neuron inervates muscle and soma is in ventral grey matter. Primary sensory neurons innervates skin, muscle, and soma is in dorsal root ganglion.
Peripheral nervous system (PNS): Consists of nerves and Ganglia. Has somatic(sensory and motor) and autonomic (sympathetic and parasympathetic) divisions.
Function of peripheral nerves: Somatic nervous system processes input from sensory receptors and coordinates muslce activity and is under voluntary control. Autonomic NS regulates vital funcations such as respiration, blood pressure, heart rate, digestions, and is involuntary. Both branches influenced by CNS.
Peripehral nervous system organization: Cranial and spinal nerves with axons carrying somatic and autonimic information. Neuron cell bodies aka somas are organized into ganglia found throughout the body and within the vertebral column and alongside the vertebal column. The axons of the neurons cell bodies bundle and run together as nerves.
Nerves contain only the axons of motor and sensory neurons. they do not contain the neruonal somas or cell bodies. Most neuron soma is found in the ventral horn o fthe spinal cord at each level. Sensory neuron soma is found in the dorsal root ganglion at each level of the vertebral column in the intervertebral foramen, the opening between vertebrae through which nerves leave the spine and extend to other parts of the body.
Cervical nerves 3-5 innervate diaphram muscle.
Cervical 5 innervates deltoid and biceps.
cervical 7 innervates triceps and extensor of wrist and fingers.
C8 innervates abductor of fith finger.
L2-4 innervates quadriceps.
L5 innervates long extensor of big toe and anterior tibial muscles.
S1 innervaets plantar fexors and gastrocnemius.
Sensory Dermatomes: the area of skin innervated by axons in a single dorsal root. Dermatomes of adjecent dorsal roots overlap. Insury to a single dorsal root causes no loss of sensation. Injury may cause pain in area subserved by the dorsal root.
Cranial nerves carry somatic sensory and motor information for head muscles and skin. Carry visceral sensory information for viscera and glands of mouth, eyes, and neck.
Nerve structure: 3 layers. Endoneurium, most interior, consists of axons and schwann cells and surrounding basal lamina. Perineurium, middle layer, consists of fibroblasts and connective tissue components aka extracellular matrix that wrap around and protect fascicles of axons each within their endoneurium. Epineurium, external layer, consist of less fibroblasts and more connective tissue and blood vessels that surround the multiple fascisicles within a nerve, continuous with the dura mater.
Myelin: Myelin membrane different in composition from plasma membrane of neuron and other cells an dbetween oligodendrocyte and schwann cells.
Autonomic nervous system (ANS)
Somatic nervous system vs ANS: CNS gets info from 2 sources, the external world and the internal world.
External world Special senses, somatic senses.
Internal world: heart, lungs, digestive organs, blood vessels.
The brain responds using the somatic NS and the Autonimic NS.
Autonomic nerous system= comprised of neurons in the CNS and PNS and autonomic nerves that control internal organs, inervate cardiac and smooth muscle and glands. Function to maintain homeostasis. Blood pressure, blood volume, temperature, and acidity.
Organs also regulated by the neuroendocrine system located in the hypothalamus of the brain.
Preganglionic axons synapse on postganglionic autonomic neurons. Postganglionic azons synapse on end organ, gland, smooth muscle. Sensory neurons end in a specialized reveptor or naked ending located in target. Motor neurons synapse directly on muscle or glands.
Anatomy of the ANS: Organs (except liver) are innervated by both sympathetic and parasympathetic fibers. Generally antagonize each other to maintain homeostasis and respond to sensory and emotional information.
Sympathetic NS: Innervate all organds, glands, and smooth muscle in artieries. INcluding those in skin and sweat glands in skin, but not lacrimal glands. Always active, under influence of hypothalamus to maintain homeostasis. Readies body for aciton, increases heart rate, blood pressure, moves blood to muscles away from viscera. Fear, neurons in hypothalamus and brain stem activate adrenal glands that decrete adrenalin aka epinephrine. Postganglionic fibers use norepinephrine as neurotransmiter.
Short preganglionic fibers and long postganglionic fibers. Preganglionic neurons are found in lateral horns of thoracic and lumbar spinal cord levels only. Ganglia lie close to spinal cord in the paravertebral chain aka sympathetic chain.
Some ganglia lie in body cavity such as superior cervical, celiac, and mesenteric.
Parasympathetic NS: Innervates all organs except liver, skin, and arteries. Always active to maintain homeostasis. Causes relaxation and inhibits activity of innervated end organs. Except increases digestion. blood pressure and heart rate decreases, blood flow dirced from muscle to viscera.
Preganglionic fibers synapse in ganglia close to or in innervated organ. Possess a long preganglionic fiber and short postganglionic fiber.
Preganglionic fibers arise from brain stem and travel in cranial nerves 3, 7, 9, and 10
Also arise from sacral spinal cord and travel in spinal nerves S2-S4.
5000 years ago the ancient Egyptians believed that the heart was the seat of the mind.
Hippocrates wrote that the brain was the seat of knowledge and memory.
Aristotle believe that the heart was the seat of knowledge and the brain merely cooled the blood and determined temperament.
Galen 130-200 AD found fluid filled ventricles in the brain by dissecting sheep. He proposed that the cerebrum stored sensation and memory and the cerebellum controlled muslce movements. Created the fluid mechanical theory that fluid from the ventricals was pumped down hollow tubes similar to blood vessels to inflate muscles.
Andreas Vesalius (1514-1564) was an anatomist that drew detailed structures of the brain.
Descartes reasoned that humans not animals have a mind sperate from the brain.
By the end of the 18th century the nervous system was seperated into the basic divisions of the central nervous system (CNS) and the peripheral nervous system (PNS).
1798 Galvani discovers the electrical nature of nervous activity, nerves were not tubes but wires.
1810 Bell and Magendie propose sensory and motor fibers and start the general use of experimental ablation method. The practice of studying the effects of damaging a part of the brain to determine it's function.
The idea of localized function in different areas of the brain begins taking root.
by the end of the 19th century it was understood that:
Spinal roots carry functional information, the cerebellum is the origin of motor fibers, and the cerebrum is the destination of sensory fibers.
Paul Broca studied patients with speech loss and discovered the discrete region that controls human speech (Broca's area).
Neuron Doctrine: Each nerve cell is a distinc genetic and anatomical unit with axons and dendrites that have distinct endings (proposed by Waldheyer in 1891).
The Neuron doctrine was proven after the staining of neurons and processes by Golgi and Cajal.
eticular theory: Disproven theory that axons and dendrites form a continuous network.
20th century neuroscience.
1920s Langley, Loewi, Dale, and others identify neurotransmitters that function as chemical messengers between neurons.
1940s Shannon, Weaver, and Weiner introduce concepts of information processing and control systems (cybernetics)
1950s Hodgkin, Katz, and Eccles make precise recoding of electrical signals with microelectrodes. Electron microscompy reveals synapses and neuronal fine structure. Single cell analysis reveal brain circuits for feature abstraction.
1960s Integrative functions of dendrites are recognized: synaptic circuts and synaptic interactions without impulses are identified.
1970s Neuromodulator substances and second messengers are found that greatly extend the duration and complexity of neuronal interactions. Computerized imaging techniques permit visualization of brain activity in relation to sensation and cognition. Molecular methods are introduced for analyzing genetic mechanisms. Society of neuroscience established.
2000s Neuron stem cell discovered.
CELLS OF THE NERVOUS SYSTEM
Neurons: Reside in grey matter in nuclei and ganglia
Glia: Reside in grey and white matter.
Oligodendrocytes in CNS
Astrocyte in CNS
Schwann cell in PNS
Microglia: carry out immune function
Ependymal cells: Line ventricales
Meningial cells: cover brain and spinal cord.
Neuron classifications:
By shape:
Unipolar
Bipolar
Multipolar
by major neurotransmitter:
Dopaminergic
Adrenergic
Cholinergic
by function:
Motor, snesory, sympathetic, etc.
Projection, interneuron.
Parts of the neuron:
Soma: cell body of neuron, contains nucleus
Axon: long fiber which carried information to other neurons.
Dendrite: recieves information from other neurons
Dendritic spine: Receives information at a single synapse.
Glial cells: 5-10X more abundant than neurons
Astrocyte, oligodendrocyte, Schwann cell, Microglial cell, Ependymal Cells.
Oligodendrocyte: Present only in the CNS, found mostly in white matter, mylenates large diameter axons in the CNS.
Schwann cell: Present only in the PNS, mylenates axons, participates in development and regeneration of the PNS.
Astrocyte: Protoplasmic found in grey matter, Fibrous found in white matter. Regulates CNS metabolism and extracellular ion concentrations. Plays important role at the synapses.
Brain organization
Divisions of the nervous system:Central nervous system (CNS), Peripheral nervous system (PNS), autonomic nervous system (ANS).
CNS: Brain= Cerebrum, cerebellum, brain stem. Spinal cord.
Cerebrum: Cerebral hemispheres right and left. Four lobes per hemisphere; Frontal, parietal, occipital, and temporal.
Deep structures of the cerebrum: Basal ganglia and thalamus.
Neocortex: allows for human functions; Learning, reasoning, intention, desires, and the "mind".
Gyrus and sulcus.
Gyrus- folds on surface of brain.
Sulcus = Grooves on brain's surface.
Increases surface area of neocortex to accomodate more neurons without increasing brain size.
Cerebral hemispheres: Right hemisphere contols left side motor and sensory functions. Involved in spatial reasoning and parallel processing.
Left hemisphere contols right side motor and sensory, involved in logical reasoning.
In most humans left cerebral cortex controls language.
Frontal lobes process conscious control of movement, behavior, and personality.
Parietal lobes processes sensory information from muscle and skin.
Temporal lobes are involved in processing hearing and language.
Occipital lobes involved in vision.
Nuclei: Collection of neuronal somas located deep in the brain.
Meninges: seperated into three layers Dura mater outside, arachnoid in the middle, and pia mater at the brains surface.
Ventricals: Lateral ventricals (anterior and posterior horns), Third ventrical (at the level of the thalamus), and fourth ventricle (at the level of the pons and cerebellum)
Ventricles are filled with cerebral spinal fluid (CSF)
Choroid Plexus: specialized tissue in ventricals that secretes CSF. CSF reabsorbed by the subarachnoid space. CSF flows from the cerebrum, brain stem cores, subarachnoid space, special structures called arachnoid villi that absorb csf.
Secreted by choroid plexus on the floor of the lateral ventricals. Brain floats in CSF.
Midbrain: Functions in visual and auditory orientation reflexes, maintaining posture, and voluntary movements of body and face, pain.
Contains nuclei for cranial nerves 3 (ocularmotor), 4 (trochlear), and 6 (abducens).
A thouroughfare for axons entering and leaving the brain.
Pons: Regulates respiration, thoroughfare for motor and sensory fibers, controls movements of the face and jaw muscles, eye movements, and sensation to face. Also regulates sleep.
contains nuclei for cranial nerves 5 (trigeminal), and 7 (facial).
Trigeminal, abducesn, fascial, and vestibulochoclear nerves run through it.
Medulla Oblongata: Caudal portion of brainstem, leads to spinal cord. Contains nuclei for cranial nerves 7-12. Involved in speech, swallowing, moving neck, shoulder muscles, salivation, taste, hearing, balance, mood, alertness, respiration, heart rate. Throughfare for somatic afferent and efferent fibers from brain to spinal cord.
Motor modulation systems: Cerebellum, involved in controlling movements by sequentially activating muscles. Basal ganglia, involved in voluntary beginning and ending movements.
Cerebellum: Derived from hindbrain but not part of brain stem. Connected to pons and Medulla by cerebellar peduncles that are made up of axons entering and leaving the cerebellum. 4th ventrical seperates it from the brain stem.
Coordinates muscle activity and plans complex movements. Involved in learning and memory of motor tasks. Posture, keeps muslce tone during voluntary movement and reflexes. Equilibrium. Spatial reasoning.
Right and left hemispheres. Unlike cerebrum, system is uncrossed (the right side of the cerebellum controls the right side of the body)
Cerebellar lobes: Anterior lobe, Posterior lobe, vermis, Flocculondular.
Anterior lobe: Unconcious Proprioception.
Posterior lobe: Fine motor coordination.
Flocculonodular lobe: Eye tracking and movement of eyes in relation to head position and movement.
Vermis: Body posture and locomostion
Deep cerebellar Nuclei: Emboliform, Dentate, Globose, Fastigial. Main output neurons from cerebellum into spinal cord to innervate motor neurons in the ventral horn.
Deep Brain nuclei: Basal Ganglia-Striatum, 3 forebrain nuclei invovled in motor control. Diencephalon, Processing sensory and motor information and endocrine role. Limbic system, involved in regulating emotion, motivation, and homeostasis.
Basal Ganglia: Nuclei surrounding Thalamus with common function, 3 components. Putamen, globus pallidus, caudate nucleus (aka striatum). Substantia nigra. Subthalamic nuclei.
Planning of coluntary movement including starting and stopping a movement and tone of antigravity muscles.
Diencephalon: Anterior to the midbrain and forms the walls of the third ventricle. Consists of two parts the thalamus and the hypothalamus.
Thalamus : processes sensory information, relays motor information.
Hypothalamus: Part of limbic system, controls the pituitary gland.
Thalamus: divided into 6 nuclei. Relay for afferent information traveling to cortical regions. Several nuclei receive information from optic nervs. Other nuclei recieve auditory and motor information.
Hypothalamus: Involved in maintaining homeostasis of your bodily functions, controls body temperature, blood pressure, salt and water levels. Initiates and suppresses eating and drinking. Activates and inhibits pitutitary gland. Involved in emotional responses tha tchange blood pressure, heart rate, respiration, blushing, and sweating.
Limbic system: Regulates visceral motor functions, emotions, memory, and olfaction.
Cranial nerves.
1. olfactory
2. optic
3. occularmotor
4. trochlear
5. trigeminal
6. abducens
7. facial
8. vestibularchochlear
9. glossopharyngeal
10. vagus
11. accesory
12. hypoglossal.
Brainstem: 3 primary vessivals develop from neural tube Forebrain, midbrain, and hindbrian. Midbrain derived form mesenchepalon. Pons derived with cerebellum from metenchephalon. Medulla oblangata derived from the myencephalon
SPINAL CORD AND PNS
Major concepts: spinal cord is shorter than the vertebral column cauda equina is the spinal roots travaling down the subarachnoid space until the correct vertebra to exit. Spinal cord grey matter is central, white matter in peripheral. Dorsal= sensory, ventral = motor. Primary motor neurons are in ventral spinal cord; primary sensory neurons are in dorsal root ganglia.
Dorsal horn and columns, sensory. Ventral horn and columns, motor. Spinal canal. Dorsal rootlets, roots, and ganglia. Ventral rootlets and roots. Spinal pia mater, arachnoid, and dura mater. Cauda equina.
8 cervical spinal cord levels between cervical vertabra 1-7 give rise to 8 cervical nerves c1-c8.
12 Thoracic spinal cord levels T!-T12.
5 Lumbar spinal cord levels L1-L5.
5 Sacral spinal cord levels, L1-L5
1 Coccygeal nerve.
Lateral Horns: Only at lower toracic and upper lumbar levels and contain autonomic sympathetic neuronal somas. Also called the inermediolateral cell collumn in the grey matter of the spinal cord.
Interneuron is another name for an association neuron. Primary motor neuron inervates muscle and soma is in ventral grey matter. Primary sensory neurons innervates skin, muscle, and soma is in dorsal root ganglion.
Peripheral nervous system (PNS): Consists of nerves and Ganglia. Has somatic(sensory and motor) and autonomic (sympathetic and parasympathetic) divisions.
Function of peripheral nerves: Somatic nervous system processes input from sensory receptors and coordinates muslce activity and is under voluntary control. Autonomic NS regulates vital funcations such as respiration, blood pressure, heart rate, digestions, and is involuntary. Both branches influenced by CNS.
Peripehral nervous system organization: Cranial and spinal nerves with axons carrying somatic and autonimic information. Neuron cell bodies aka somas are organized into ganglia found throughout the body and within the vertebral column and alongside the vertebal column. The axons of the neurons cell bodies bundle and run together as nerves.
Nerves contain only the axons of motor and sensory neurons. they do not contain the neruonal somas or cell bodies. Most neuron soma is found in the ventral horn o fthe spinal cord at each level. Sensory neuron soma is found in the dorsal root ganglion at each level of the vertebral column in the intervertebral foramen, the opening between vertebrae through which nerves leave the spine and extend to other parts of the body.
Cervical nerves 3-5 innervate diaphram muscle.
Cervical 5 innervates deltoid and biceps.
cervical 7 innervates triceps and extensor of wrist and fingers.
C8 innervates abductor of fith finger.
L2-4 innervates quadriceps.
L5 innervates long extensor of big toe and anterior tibial muscles.
S1 innervaets plantar fexors and gastrocnemius.
Sensory Dermatomes: the area of skin innervated by axons in a single dorsal root. Dermatomes of adjecent dorsal roots overlap. Insury to a single dorsal root causes no loss of sensation. Injury may cause pain in area subserved by the dorsal root.
Cranial nerves carry somatic sensory and motor information for head muscles and skin. Carry visceral sensory information for viscera and glands of mouth, eyes, and neck.
Nerve structure: 3 layers. Endoneurium, most interior, consists of axons and schwann cells and surrounding basal lamina. Perineurium, middle layer, consists of fibroblasts and connective tissue components aka extracellular matrix that wrap around and protect fascicles of axons each within their endoneurium. Epineurium, external layer, consist of less fibroblasts and more connective tissue and blood vessels that surround the multiple fascisicles within a nerve, continuous with the dura mater.
Myelin: Myelin membrane different in composition from plasma membrane of neuron and other cells an dbetween oligodendrocyte and schwann cells.
Autonomic nervous system (ANS)
Somatic nervous system vs ANS: CNS gets info from 2 sources, the external world and the internal world.
External world Special senses, somatic senses.
Internal world: heart, lungs, digestive organs, blood vessels.
The brain responds using the somatic NS and the Autonimic NS.
Autonomic nerous system= comprised of neurons in the CNS and PNS and autonomic nerves that control internal organs, inervate cardiac and smooth muscle and glands. Function to maintain homeostasis. Blood pressure, blood volume, temperature, and acidity.
Organs also regulated by the neuroendocrine system located in the hypothalamus of the brain.
Preganglionic axons synapse on postganglionic autonomic neurons. Postganglionic azons synapse on end organ, gland, smooth muscle. Sensory neurons end in a specialized reveptor or naked ending located in target. Motor neurons synapse directly on muscle or glands.
Anatomy of the ANS: Organs (except liver) are innervated by both sympathetic and parasympathetic fibers. Generally antagonize each other to maintain homeostasis and respond to sensory and emotional information.
Sympathetic NS: Innervate all organds, glands, and smooth muscle in artieries. INcluding those in skin and sweat glands in skin, but not lacrimal glands. Always active, under influence of hypothalamus to maintain homeostasis. Readies body for aciton, increases heart rate, blood pressure, moves blood to muscles away from viscera. Fear, neurons in hypothalamus and brain stem activate adrenal glands that decrete adrenalin aka epinephrine. Postganglionic fibers use norepinephrine as neurotransmiter.
Short preganglionic fibers and long postganglionic fibers. Preganglionic neurons are found in lateral horns of thoracic and lumbar spinal cord levels only. Ganglia lie close to spinal cord in the paravertebral chain aka sympathetic chain.
Some ganglia lie in body cavity such as superior cervical, celiac, and mesenteric.
Parasympathetic NS: Innervates all organs except liver, skin, and arteries. Always active to maintain homeostasis. Causes relaxation and inhibits activity of innervated end organs. Except increases digestion. blood pressure and heart rate decreases, blood flow dirced from muscle to viscera.
Preganglionic fibers synapse in ganglia close to or in innervated organ. Possess a long preganglionic fiber and short postganglionic fiber.
Preganglionic fibers arise from brain stem and travel in cranial nerves 3, 7, 9, and 10
Also arise from sacral spinal cord and travel in spinal nerves S2-S4.
My dream is a hemispheric common market, with open trade and open borders.
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