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88 Cards in this Set
- Front
- Back
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To what do the terms, central nervous system (CNS) and peripheral nervous system (PNS) refer?
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CNS is the brain and spinal chord… the PNS is all of the spinal nerves (31 pair) and cranial nerves(12 pair) and associated ganglia.
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The PNS is divided into two main divisions, what are they?
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Afferent (bringing info to the brain and spinal chord) and Efferent (bringing signals away from the
brain and spinal chord). |
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How is a neuron different from a nerve?
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The neuron is the individual cell,
the nerve is a bundle of neurons. |
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What type of neuron is attached to or associated with a sensory receptor?
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afferent neuron
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What type of neuron synapses with skeletal muscle cells?
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Efferent somatic motor neurons. (Sometimes also referred to as lower motor neurons or alpha motor neurons.)
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What two types of neurons synapse with smooth muscle, cardiac muscle or glandular cells?
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Sympathetic and parasymphathetic
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Where is a muscle spindle apparatus found?
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Within the regular muscle fibers (extrafusal fibers).
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What is the function of the muscle spindle apparatus?
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The muscle spindle apparatus monitors the length of the muscle fibers (in particular, sudden changes in length).
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Where is the Golgi Tendon Organ found?
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Within the regular muscle fibers (extrafusal fibers).
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How the function of the Golgi Tendon Organ different from the muscle spindle
apparatus? |
The Golgi Tendon Organs monitor the tension is the muscle fibers (the tension is amount of contraction without shortening of the muscle.)
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What is a reflex (arc)?
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The direct interaction of a sensory neuron and a motor neuron at the spinal cord.
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Does the number of neurons involved vary from one reflex to another?
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yes
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What is the simplest reflex?
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Monosynaptic-stretch reflex arc
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How many synapses are involved in the simplest reflex?
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one - Monosynaptic-stretch reflex arc
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In reciprocal innervation (in flexor –extensor muscle pairs) when one of the pair is stimulated to
contract, what neural activity prevents the other muscle from contracting so that they will not work against each other? |
The activation of an inhibitory interneuron
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What are the functions of interneurons in a reflex pathway?
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In general, they are inhibitory.
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Do all interneurons stimulate (depolarize) other neurons?
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no
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What are spinal nerves?
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The bundles of sensory and motor neurons that are bringing information to the CNS and activating skeletal or other types of muscles.
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How many spinal nerves does the
human body have? |
31
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By which pathway do sensory fibers enter the spinal cord?
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Through the dorsal root.
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Which pathway do the motor fibers use to exit the spinal cord?
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Through the ventral root.
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What is the dorsal root ganglion?
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The dorsal root ganglion is where the majority of sensory neurons cell bodies reside.
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What is the function of a sensory receptor?
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Sensory receptors sample both the external and internal
environments. Internally, they help to monitor homeostasis. Externally, they are sampling the external environment for changes that may affect the body as a whole, and aid the body to interact with the external environment. |
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Do receptors respond to a variety of different stimuli?
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No - this property is referred to as the "Law of Specific Nerve Energies."
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What part of a nerve makes up the receptor region?
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The receptor region is the cell body/dendritic area of the neuron.
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What types of stimulus are transduced to the CNS?
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Each receptor is specific for only one type of stimulus, i.e.
changes in pressure. If the stimulus is encountered, the receptor "transduces" (or converts) the stimulus to action potentials that are sent to the CNS. |
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What are tonic receptors?
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Tonic receptors are those whose frequency is always directly
proportional to the magnitude of the stimulus |
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What are phasic receptors?
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Phasic receptors are
those that act to "alert" the brain. When they are stimulated they exhibit a burst of action potentials which quickly subside to a low level frequency of action potentials (referred to as adaptation). |
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What is a generator potential?
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A generator potential is the equivalent of an EPSP
which occurs on the receptor membrane. |
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To what modality do the receptors in our eyes respond to?
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The modality that our rods and cones
respond to is light. |
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What are rods and cones and what are the differences between them?
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Both detect different aspects of light entering the eye. The cones (of which there are 3 subtypes)
respond to different colors. The rods help to distinguish different levels of low light. |
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How does the body control the amount of light that is allowed to interact with our rods and cones?
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By dilation or constriction of the iris, which is a muscle with both circular and radial muscle fibers.
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What is the fovea centralis?
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This is a small area on the retina that has an extremely high
concentration of rods and cones. |
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What is the function of the fovea centralis?
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The fovea centralis is the area that is responsible for all sharp (focused) vision
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What is the optic disk?
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An area that is commonly
referred to as the "blind spot" in which no "vision" occurs. |
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What is the function of the optic disk?
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The optic disk is where all neurons and blood vessels (both arteries and veins) converge and exit through the retina. So the optic disk is completely devoid of rods and cones
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What is accommodation?
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Accommodation is the ability to focus an object, either far away or close up, directly on the fovea
centralis. |
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How is accommodation controlled with respect to vision?
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The ciliary muscles of the eye relax or contract to flatten or curve the lens of the eye, so that the image stays focused on the fovea centralis.
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Dorsal
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Sensory – afferent ( back)
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Ventral
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Motor – efferent (front)
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Decussate
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“cross over”
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Ascending Spinal Tract
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Sensory info from body travels to brain in Ascending spinal tract
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Descending Spinal Tract
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Motor activity from brain travels to body in descending tracts
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Pyramidal/corticospinal
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Input from the primary motor cortex, fibers originating from neuronal cell bodies known as pyramidal cells within the primary motor cortex descend directly without synaptic interruption to terminate on motor neurons
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extrapyramidal
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Input from the brain stem as part of the multineuronal motor system. The pathways composing the multineuronal motor system include a number of synapses that involved more regions of the brain
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Ganglia
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Collection of neuronal cell bodies located outside the central nervous system
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Dorsal Root
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Composed of sensory fibers (afferent)
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Ventral Root
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Composed of motor fibers (efferent)
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Nerve
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Bundle of peripheral neuronal axons, some afferent and some efferent, enclosed by a connective tissue covering and following the same pathway
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Spinal Nerves
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31 pairs that are bundled in nerves which bring infor to the CNS, are mixed nerves that separate next to spinal cord into dorsal and ventral roots
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Cranial Nerves X=Vagus
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12 pairs of peripheral nerves, the majority of which arise from the brain stem
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PNS
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Nerve fibers that carry information between the CNS and the other parts of the body
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Afferent
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Portion of the PNS that carries information from the periphery to the CNS
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Efferent
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Portion of the PNS that carries instructions from the CNS to effector organs
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Transduce
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Change environmental information into action potentials (the common language of NS)
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Modality
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A particular form of information for which receptors specifically respond too (form of information such as sound, light, pressure)
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Sensory Receptors
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Afferent neuron’s peripheral ending, are grouped receptors according to type of stimulus they transduce
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Chemoreceptors
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Sensory receptor sensitive to specific chemical stimuli
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Photoreceptors
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Sensory receptor responsive to light
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Thermoreceptors
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Sensory receptor responsive to temperature changes
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Mechanoreceptors
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Sensory receptors sensitive to mechanical energy that deforms their cell membrance such as stretching or bending (touch)
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Nociceptors
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Sensory receptors sensitive to intense stimuli by the signaling of pain, sensitive to tissue damage
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Proprioceptors
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Sensory receptors signaling the awareness of position info of body parts
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Acuity
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Discriminative ability, ability to discriminate between two different points of stimulation
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Receptive Field
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The field of sensory receptors, the higher the acuity the smaller the receptive field such as finger tips, where as legs contain bigger receptive fields and smaller acuity
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Cutaneous Receptors
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Adequate Stimulus
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Refers to the fact that a receptor is set to start producing action potentials with a minimum of activation
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Tonic Receptors
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Respond as constant rates as long as stimulus is applied, e.g. Pain
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Phasic Receptors
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Respong with bursts of activity but quickly reduce firing rate to constant stimulation (ADAPTATION) e.g. smell, touch
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Generator Potentials
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When dealing with receptors, they only receive excitatory signals, equivalent to EPSP’s
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Rods/Cones
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Eyes photoreceptors used for color vision (cones) and night vision (rods)
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Fovea Centralis
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High density of cones where our sharp vision and acuity occurs
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Optic Disk
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The place where axons of retinal neurons gather and come together and exit the eye
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Blind Spot
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The optic disk, where retinal neurons exit the eye
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Accommodation
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The ability of eyes to keep image focused on retina as distance between eyes and object varies, results from contraction of ciliary muscles that either flatten or curve the lens
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Reflex Arc
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Simple sensory input, motor output circuit involving only peripheral nerves and spinal cord
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Golgi Tendon Organ
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Monitors the tension in the muscle fibers, the tension is amount of contraction without shortening the muscle, found in regular muscle fibers
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Muscle Spindle Apparatus
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Monitors length of muscle, located near the tendon in regular muscle fibers, sensing if muscle is too stretched out or too flabby and if sensed then reflex arc is initiated to correct,
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Intrafusal Fiber
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Muscle fibers of spindle apparatus, consists of nuclear bag and chain fibers
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Extrafusal Fiber
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Major muscle fibers
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Nuclear Bag Fiber
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Muscle fibers of spindle apparatus sensing Sudden stretch
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Nuclear Chain Fiber
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Muscle fibers of spindle apparatus sensing Sustained stretch
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Alpha Motor Neurons
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Motor neurons that supple the extrafusal fibers
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Gamma Motor Neurons
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Efferent neuron that innervates a muscle spindle’s intrafusal fibers
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Coactivation
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Coactivation of the gamma motor neuron system along with the alpha motor neuron system during reflex and voluntary contractions take slack out of the spindle fibers as the whole muscle shortens
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Monosynaptic-Stretch Reflex
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Simplest reflex involving one synapse
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Reciprocal Innervation
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As one muscle contracts another relaxes, agonist vs antagonist
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Crossed-Extensor Reflex
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Involves both sides of the body, such as stepping on a nail, the other side needs to be ready to be activated quickly to rebalance the offset of the other side, so the other side has the opposite affects
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