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BMS 250 Lecture
Chapter 14
| Term | Definition |
|---|---|
| 5 subdivisions of the spinal cord | cervical, thoracic, lumbar, sacral, coccygeal |
| What is the difference between spinal meninges and cranial meninges? | spinal dura is only 1 later |
| Gray matter of spinal cord | innermost layer divided into posterior, lateral, and anterior horn |
| White matter of spinal cord | outermost layer divided into posterior, lateral, and anterior funiculus |
| Functional nuclei in the posterior horn | sensory nuclei (somatic and visceral) |
| Functional nuclei in the lateral and anterior horn | motor nuclei |
| How many pairs of cervical nerves? | 8 |
| How many pairs of thoracic nerves? | 12 |
| How many pairs of lumbar nerves? | 5 |
| How many pairs of sacral nerves? | 5 |
| How many pairs of coccygeal nerves? | 1 |
| What are spinal nerves formed by? | posterior (dorsal root) containing sensory axons (cell bodies in posterior root ganglion), anterior (ventral) root containing motor axons (cell bodies in anterior and lateral horns of spinal cord) |
| What type of nerve is a spinal cord always? | mixed |
| Nerve plexuses | network of spinal nerves that come from multiple anterior rami (will split into "named" nerves to innervate specific areas of the body) |
| Dermatomes | specific segment of skin innervated by a single spinal nerve |
| All spinal nerves except C1 do what? | innervate a skin segment |
| Ascending pathways | sensory receptors to spinal cord to brain; relay sensory information form sensory receptors to the brain |
| Types of ascending pathways | somatosensory and viscerosensory pathways |
| Somatosensory pathways | from skin, muscles, and joints |
| Viscerosensory pathways | from internal organs |
| What neurons do ascending pathways use to relay signals to the brain? | primary, secondary, and tertiary neurons |
| Primary neuron | from sensory receptor to CNS (synapses on secondary neuron) |
| Secondary neuron | from primary neuron to tertiary neuron or cerebellum |
| Tertiary neuron | from secondary neuron to cerebellum (primary somatosensory cortex) |
| Anterolateral pathway | receives sensations associated to crude touch, crude pressure, pain, and temperature; composed of lateral spinothalamic tract, anterior spinothalamic tract |
| Pathway of anterolateral pathway | primaryneuron carries sensoryinformation from receptor to posteriorhorn, secondaryneuron carries information through spinalothalamictracts (from posterior horn to thalamus), tertiary neuron carries information from thalamus to primary somatosensory cortex |
| Descending pathways | brain to spinal cord to effectors |
| General characteristics of all pathways | pathways are paired (matching left and right tracts), composed of 2 or more neurons, common neuronal cell body locations, common axon locations, pathways decussate (axons cross midline so brain processes information from contralateral side of body) |
| What neurons do descending pathways use? | upper motor neuron and lower motor neuron |
| Upper motor neuron | excites or inhibits activity of lower motor neurons, cell body in cerebral cortex, cerebral nuclei or specific nuclei within brain stem |
| Lower motor neuron | always excite skeletal muscle fibers to contract cell body in anterior horn of spinal cord, project to and innervate a specific skeletal muscle |
| Direct (pyramidal) pathway | upper motor neuron synapses directly on to lower motor neuron |
| Upper motor neuron axon (direct pathway) | cerebral cortex to spinal cord; travels from primary motor cortex through corticospinal tract, synapses on lower motor neuron in anterior horn of spinal cord |
| Lower motor neuron axon (direct pathway) | spinal cord to muscle; extends through a spinal nerve, innervates (synapses on) a skeletal muscle |
| Pathway of direct pathways | upper motor neuron carries motor command from primary motor cortex to anterior horn of spinal cord, lower motor neuron carries command from anterior horn of spinal cord to skeletal muscle |
| Reflexes | involuntary response (survival mechanism); respond immediately, awareness comes later |
| Common properties among all reflexes | a stimulus initiates the response, they are rapid (involves few neurons), pre-programmed, and involuntary |
| Reflex arc | neuron pathways that generates a response |
| Components of reflex arcs | stimulus actives sensory receptor, sensory neuron transmits signals to spinal cord, information processed in integration center, motor neuron transmits signals to effectors, effector responds |
| Classifying reflexes | number of synapses in reflex arc and which sides of the body are involved |
| Classifying reflexes by number of synapses in arc | monosynaptic and polysynaptic |
| Monosynaptic | sensory neuron synapses directly on motor neurons (one synapse) |
| Polysynaptic | 1+ interneurons between sensory and motor neurons (more than one synapse) |
| Classifying reflexes by which sides of the body are involved | ipsilateral and contralateral |
| Ipsilateral | receptor and effector are on the same side of the body |
| Contralateral | receptor and effector are on the opposite sides of the body |
| Types of spinal reflexes | stretch reflex, golgi tendon reflex, withdrawal reflex, crossed-extensor reflex |
| Stretch reflex | muscle contracts in response to excessive stretching |
| Stretch reflex steps | musclespindle detectsstretch, stimulates S nervesignals tobe transmitted to SC, Snerve synapseson M neuron&transmits nervesignals tothe samemuscle stimulatingcontraction while interneuronssynapse on Mneuron of antagonisticmuscle inhibitingcontraction |
| Golgi tendon reflex | muscle lengthens/relaxes in response to excessive contraction/tension |
| Golgi tendon reflex steps | musclecontraction increases tensiontotendons, detected by golgitendon organs&stimulates S nervesignals that travel to CNS, which synapse on interneurons in SC, interneuron inhibit M neurons to same muscle & stimulate M neurons to antagonistic muscles |
| Withdrawal reflex | muscle contracts to withdraw body part away from painful stimulus |
| Crossed-extensor reflex | stabilizes contralateral limb when a withdrawal reflex occurs (usually in lower limbs) |
| Withdrawal reflex/Crossed-extensor reflex steps | painfu stimulusdetected byreceptors of Sneurons, Snerve signal detected by interneurons whichstimulate Mneuron to flex knee&withdraw from painfulstimulus while other interneurons decussate&stimulate Mneurons on contralateralside to support bodyweight |
Created by:
kkade
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