Term
| Sensory pathways begin at _____ and end in the _____. |
|
Definition
peripheral receptors
CNS, often in diencephalon &/or cerebral hemispheres |
|
|
Term
|
Definition
| info carried (much of it never reaches primary sensory cortex and our awareness) |
|
|
Term
|
Definition
| conscious awareness of a sensation |
|
|
Term
|
Definition
| area monitored by a single receptor; bigger = poorer ability to to localize a stimulus |
|
|
Term
| basic events along a sensory pathway |
|
Definition
1. depolarization of a receptor- stimulus produces a graded change in transmembrane potential
2. a.p. generation
3. propagation over labeled line, info interpreted by CNS based on nature of axon it arrives on |
|
|
Term
|
Definition
| the conversion of a stimulus to change in membrane potential |
|
|
Term
|
Definition
| axons carrying info about one type of stimulus (touch, pressure, temperature) |
|
|
Term
| Info goes from the sensory pathway to _____, and then to either the _____ or _____. |
|
Definition
CNS processing
involuntary or voluntary motor pathway |
|
|
Term
| CNS processing part of the pathway |
|
Definition
| info is processed at every synapse along the labeled line, which may branch to distribute info to multiple nuclei and centers in the CNS |
|
|
Term
| involuntary motor pathway |
|
Definition
| immediate reflex response occurs, possibly even before sensations reach the cerebral cortex |
|
|
Term
|
Definition
| first perception occurs (only about 1% of arriving sensations), then the voluntary response occurs, which isn't immediate and can moderate, enhance, or supplement the relatively simple reflexive respone |
|
|
Term
| What are the simplest receptors? Describe them. |
|
Definition
dendrites of sensory neurons
tips are free nerve endings so are not protected by accessory structures; can be stimulated by many different stimuli, so there is little receptor specificity |
|
|
Term
| What are the 4 main functional classifications of general sensory receptors? |
|
Definition
| nociceptors, thermoreceptors, chemoreceptors, and mechanoreceptors |
|
|
Term
| What are nociceptors and their two types? |
|
Definition
pain receptors; free nerve endings with large receptive fields and broad sensitivity
Type A fibers and Type C fibers |
|
|
Term
|
Definition
| nociceptors; myelinated axons that carry sensations of fast pain that very quickly reach the CNS (often triggering somatic reflexes) and are also relayed to the primary motor cortex for conscious attention; stimulus can be located to an area within a few cm |
|
|
Term
|
Definition
| nociceptors that are slower, unmyelinated axons that carry sensations of slow pain that cause generalized activation of reticular formation and thalamus; only general idea of where the stimulus is located |
|
|
Term
|
Definition
| prickling pain such as an injection or a deep cut that is felt by Type A fibers |
|
|
Term
|
Definition
| burning, aching pain felt by Type C fibers |
|
|
Term
|
Definition
| temperature receptors that are free nerve endings located int he dermis, skeletal muscles, liver, and the hypothalamus |
|
|
Term
| Which type of thermoreceptor is there more of? |
|
Definition
| cold - 3-4x as many as warm, but the two have no structural difference at the cellular level |
|
|
Term
|
Definition
| respond to water-soluble and lipid-soluble substances that are dissolved in body fluids (interstitial fluid, plasma, and CSF) |
|
|
Term
|
Definition
| sensitive to stimuli that distort the plasma membrane, which contain mechanically-gated ion channels that open/close to stretching, compression, twisting, etc. |
|
|
Term
| What types of mechanoreceptors are there? |
|
Definition
| proprioceptors, baroreceptors, and tactile receptors |
|
|
Term
|
Definition
| the most structurally and functionally complex mechanoreceptors that monitor positions of joints and muscles |
|
|
Term
|
Definition
| mechanoreceptors that detect pressure changes in walls of blood vessels and in portions of the digestive, reproductive, and urinary tracts |
|
|
Term
|
Definition
| mechanoreceptors that provide sensations of touch, pressure, and vibration; two kinds- fine touch and pressure and crude touch and pressure |
|
|
Term
| What are the nature of the response classifications of the general sensory receptors? |
|
Definition
| tonic receptors and phasic receptors |
|
|
Term
|
Definition
| always active, generate an a.p. at a frequency that reflects the background level of stimulation (ex. when stimulus increases or decreases, the rate of a.p. generation does too) |
|
|
Term
|
Definition
| normally inactive, but become active for a short time in response to a change in the conditions they are monitoring |
|
|
Term
|
Definition
| a decrease in sensitivity in the presence of a constant stimulus; peripheral and central |
|
|
Term
|
Definition
| occurs when the level of receptor activity changes; responds strongly at first, then activity gradually decreases |
|
|
Term
|
Definition
| occurs along sensory pathways within the CNS; awareness of stimuli virtually disappears after a short time even though sensory neurons are quite active; generally involves inhibition of nuclei along a sensory pathway |
|
|
Term
|
Definition
| branching tips of sensory neurons that aren't protected by accessory structures and are nonspecific; they are the most common receptors in the skin |
|
|
Term
|
Definition
| nerve endings wherever hairs are located that monitor distortions and movements across the body surface, which distorts sensory dendrites and leads to a.p. production |
|
|
Term
| Which general sensory receptor is best at detecting initial contact and subsequent movements? |
|
Definition
| root hair plexus- adapts rapidly |
|
|
Term
|
Definition
| fine touch and pressure receptors that are extremely sensitive tonic receptors with very small receptive fields |
|
|
Term
|
Definition
| large epithelial cells in the stratum basale of the skin that make close contact with the dendritic processes of a single myelinated afferent fiber |
|
|
Term
|
Definition
| aka Meissner corpuscles; provide sensations of fine touch and pressure receptors and low-frequency vibration; quickly adapt to stimuli, are fairly large, and are surrounded by fibrous capsule that anchors it within the dermis |
|
|
Term
| Where are tactile corpuscles most abundant? |
|
Definition
| in the eyelids, lips, fingertips, nipples, and external genitalia |
|
|
Term
| What are the dendrites of tactile corpuscles like? |
|
Definition
| highly coiled and interwoven and are surrounded by modified Schwann cells |
|
|
Term
|
Definition
| aka pacinian corpuscles; sensitive to deep pressure; fast-adapting, which leads to them being most sensitive to pulsing or high-frequency vibrating stimuli |
|
|
Term
| What are the dendrites of lamellated corpuscles like? |
|
Definition
| single dendrite within a series of concentric collagen fibers and specialized fibroblasts that are separated by interstitial fluid and shield it from any other stimulation |
|
|
Term
| Where do lamellated corpuscles provide sensation to? |
|
Definition
| the dermis, mostly in the fingers, mammary glands, external genitalia, superficial and deep fascia, and in joint capsules |
|
|
Term
| Where do lamellated corpuscles provide information in? |
|
Definition
| visceral sensory info in mesenteries, pancreas, and walls of urethra and urinary bladder |
|
|
Term
|
Definition
| sensitive to pressure and distortion of reticular dermis (deep); tonic and show little to no adaptation |
|
|
Term
| What are the dendrites of Ruffini corpuscles like? |
|
Definition
| network intertwined with a core of collagen fibers that are continuous with the dermis that are surrounded by a capsule; tension and distortion tugs and twists capsular fibers, causing stretching and compression of attached dendrites and altering activity in myelinated afferent fibers |
|
|
Term
| What are the three major somatic sensory pathways that carry information from the skin and musculature to the CNS? |
|
Definition
| spinothalamic, posterior column, spinocerebellar |
|
|
Term
|
Definition
| two tracts provide conscious sensations of crude touch, pressure, pain, and temperature |
|
|
Term
| Where do axons of first-order neurons synapse in the spinothalamic pathway? |
|
Definition
| they enter the spinal cord and synapse on second-order neurons within the posterior gray horn |
|
|
Term
| Where do axons of interneurons synapse in the spinothalamic pathway? |
|
Definition
| cross to opposite side of the spinal cord before ascending to the thalamus |
|
|
Term
| Where do third-order neurons synapse in the spinothalamic pathway? |
|
Definition
| primary sensory cortex from the thalamus |
|
|
Term
| anterior spinothalamic tracts |
|
Definition
| carry sensations of crude touch and pressure |
|
|
Term
| lateral spinothalamic tracts |
|
Definition
| carry pain and temperature sensations |
|
|
Term
| Where do second-order neurons synapse in the spinothalamic pathway? |
|
Definition
| in the ventral nuclei of the thalamus |
|
|
Term
|
Definition
| carries sensations of highly localized fine touch, pressure, vibration, and proprioception |
|
|
Term
| The posterior column pathway begins at _____ and ends at _____. |
|
Definition
a peripheral receptor
primary sensory cortex |
|
|
Term
| Where do the sensory axons of the posterior column pathway go? |
|
Definition
| ascend in the fasciculus gracilis and cuneatus to the thalamus |
|
|
Term
|
Definition
| tract in the posterior column pathway leading from the nucleus gracilis and nucleus cuneatus to the thalamus |
|
|
Term
|
Definition
| sends proprioceptive info about position of skeletal muscles, tendons, and joints to the cerebellum |
|
|
Term
| Posterior axons of the spinocerebellar pathway... |
|
Definition
| don't cross over to the opposite side of the spinal cord, they reach the cerebellar cortex via the inferior cerebellar peduncles of the same side, mostly on posterior tracts |
|
|
Term
| Anterior tracts of the spinocerebellar pathway |
|
Definition
| are dominated by axons that have crossed over |
|
|
Term
| The somatic motor pathways always involve |
|
Definition
| at least 2 motor neurons (upper and lower) |
|
|
Term
| What are the 3 major somatic motor pathways? |
|
Definition
| corticospinal, medial, and lateral |
|
|
Term
|
Definition
| cell body lies in a CNS processing center |
|
|
Term
|
Definition
| cell body lies in a nucleus of the brain stem or spinal cord |
|
|
Term
| Where does the upper motor neuron synapse? |
|
Definition
| on the lower motor neuron, which innervates a single motor unit in a skeletal muscle |
|
|
Term
|
Definition
| functional map of the cortical areas in a specific region of the bod; motor area devoted to a specific region of the cortex is proportional to the number of motor units innervated and the degree of fine motor control available |
|
|
Term
|
Definition
| sensory map of the primary sensory cortex; areas of sensory cortex devoted to particular body regions is proportional to the number of sensory receptors it contains |
|
|
Term
|
Definition
| aka pyramidal system; voluntary control over skeletal muscles |
|
|
Term
| The corticospinal pathway begins at _____. |
|
Definition
| pyramidal cells of the primary motor cortex |
|
|
Term
| Axons of the upper motor neurons of the corticospinal pathway descend into _____ to synapse on _____. |
|
Definition
the brain stem and spinal cord
lower motor neurons that control skeletal muscles |
|
|
Term
| What happens along the length of the pyramids in the corticospinal pathway? |
|
Definition
| 85% of the axons of the pathway cross the midline to enter the lateral corticospinal tracts |
|
|
Term
| Axons in the corticobulbar tracts of the corticospinal pathway synapse on |
|
Definition
| lower motor neurons in the motor nuclei of the cranial nerves |
|
|
Term
|
Definition
| provide conscious control over skeletal muscles that move the eye, jaw, face, and some of the neck and pharynx |
|
|
Term
| Descending axons of corticospinal tracts of the corticospinal pathway are visible |
|
Definition
| along the ventral surface of the medulla oblongata as thick bands called the pyramids |
|
|
Term
| anterior corticospinal tracts |
|
Definition
| the 15% of corticospinal axons that descend uncrossed |
|
|
Term
|
Definition
| somatic motor commands issued by several centers in the cerebrum, diencephalon, and brain stem that help control gross motor movements of the neck, trunk, and proximal limb muscles (result of subconscious processing) |
|
|
Term
| What are the nuclei of the medial pathway? |
|
Definition
| superior and inferior colliculi, reticular formation, vestibular nucleus; they are where the upper motor neurons are located |
|
|
Term
|
Definition
| part of the medial pathway; contain axons of upper motor neurons in the reticular formation |
|
|
Term
| What is the reticular formation's role in the pathways? |
|
Definition
| receives input from almost every ascending and descending pathway has interconnections with the cerebrum, cerebellum, and brain stem nuclei |
|
|
Term
|
Definition
| receive sensory info from inner ear about the position and movement of the head; respond to change in orientation of the head by issuing motor commands that alter muscle tone and position of the neck, eyes, head, and limbs |
|
|
Term
|
Definition
| contain axons of upper motor neurons in the superior and inferior colliculi of the midbrain that direct reflexive change in position of the head, neck, and upper limbs |
|
|
Term
|
Definition
| somatic motor commands issued from several centers in the cerebrum, diencephalon, and brain stem as a result of processing performed at the subconscious level |
|
|
Term
| The lateral pathway controls what? |
|
Definition
| distal limb muscles that perform precise movements |
|
|
Term
| What is the primary nucleus of the lateral pathway? |
|
Definition
| red nucleus- receives info from the cerebrum and cerebellum to adjust distal limb muscles and background muscle tone |
|
|
Term
| What are in the red nucleus? |
|
Definition
| upper motor neurons, whose axons cross to opposite sides of the brain and descend into the spinal cord in rubrospinal tracts that are small and extend only to the cervical spinal cord |
|
|
Term
| What are the tracts of the spinothalamic pathway? |
|
Definition
| anterior spinothalamic tracts, lateral spinothalamic tracts; importantly there are the three orders of neurons |
|
|
Term
| What are the tracts of the posterior column pathway? |
|
Definition
|
|
Term
| What are the tracts of the spinocerebellar pathway? |
|
Definition
| posterior spinocerebellar tracts and anterior spinocerebellar tracts, |
|
|
Term
| What are the tracts of the corticospinal pathway? |
|
Definition
| corticobulbar tracts, corticospinal tracts (pyramids), anterior corticospinal tracts, and lateral corticospinal tracts |
|
|
Term
| What are the tracts of the medial pathway? |
|
Definition
| reticulospinal tracts, vestibulospinal tracts, and tectospinal tracts |
|
|
Term
| What are the tracts of the lateral pathway? |
|
Definition
| rubrospinal tracts; also has the red nucleus |
|
|
Term
| What do the basal nuclei do in somatic motor control? |
|
Definition
| modify voluntary and reflexive motor patterns at the subconscious level |
|
|
Term
| What are the two main pathways for subconscious motor commands? |
|
Definition
| medial and lateral pathways |
|
|
Term
| What are the roles of the brain stem and spinal cord in somatic motor control? |
|
Definition
| control simple cranial and spinal reflexes |
|
|
Term
| What are the roles of the pons and medulla oblongata in somatic motor control? |
|
Definition
| control balance reflexes and more complex respiratory reflexes |
|
|
Term
| What are the roles of the hypothalamus in somatic motor control? |
|
Definition
| controls reflex motor patterns related to eating, drinking, and sexual activity; modifies respiratory reflexes |
|
|
Term
| What are the roles of the thalamus and midbrain in somatic motor control? |
|
Definition
| control reflexes in response to visual and auditory stimuli |
|
|
Term
| What are the roles of the cerebral cortex in somatic motor control? |
|
Definition
| plans and initiates voluntary motor activity |
|
|
Term
| What are the roles of the cerebellum in somatic motor control? |
|
Definition
| coordinates complex motor patterns through feedback loops involving the cerebral cortex and basal nuclei as well as the medial and lateral pathways |
|
|
Term
| How do we prepare for a movement? |
|
Definition
| info is relayed from the frontal lobes to the motor association areas which relay it to the cerebellum and the basal nuclei |
|
|
Term
| How do we perform a movement? |
|
Definition
| the motor association areas send instructions to the primary motor cortex |
|
|
Term
| What modify the commands as we perform a movement? |
|
Definition
| feedback from basal nuclei and the cerebellum; output along the medial and lateral pathways directs involuntary adjustments in position and muscle tone |
|
|
Term
| How do the basal nuclei adjust our movement patterns? |
|
Definition
1. they alter sensitivity of pyramidal cells to adjust the output along the corticospinal tract
2. they change the excitatory or inhibitory output of the medial and lateral pathways |
|
|
Term
| Damage to the primary motor cortex can lead to |
|
Definition
| loss of ability to exert find control over skeletal muscles |
|
|
Term
| How do the basal nuclei and cerebellum help if the primary motor cortex is damaged? |
|
Definition
| They can still control some voluntary movements, but they're awkward movements still; the cerebellum can't fine tune movements, but it can help a person stand, balance, and walk |
|
|
Term
| Nervous system disorders may result from |
|
Definition
| problems with neurons, pathways, or a combination of the two |
|
|
Term
| What causes referred pain? |
|
Definition
| strong visceral pain sensations arriving at a segment of the spinal cord can stimulate interneurons that are a par of the spinothalamic pathway, which causes stimulation of the primary sensory cortex |
|
|
Term
|
Definition
| neurons of the substantia nigra are damaged or secrete less dopamine, and the basal nuclei become more active, which leads to increase in skeletal muscle tone and rigidity and stiffness |
|
|
Term
|
Definition
| a bite injects the virus into peripheral tissues, where virus particles quickly enter synaptic knobs, and then retrograde flow carries it into the CNS |
|
|
Term
|
Definition
| a number of disorders that affect voluntary motor performance; they appear during infancy or childhood and persist all of life; cause may be trauma from birth, maternal exposure to drugs, or a genetic defect causing improper development of motor pathways |
|
|
Term
| amyotrophic lateral sclerosis (ALS) |
|
Definition
| aka Lou Gehrig disease; a progressive, degenerative disorder that affects motor neurons (upper and lower) in the spinal cord, brain stem, and cerebral hemispheres that causes atrophy of the associated skeletal muscles; possibly due to a defect in axonal transport; |
|
|
Term
|
Definition
| progressive disorder characterized by the loss of higher-order cerebral functions; causes intra and extracellular abnormalities in the brain regions such as the hippocampus and other memory processing areas |
|
|
Term
| Alzheimer disease is the most common cause of what disorder? |
|
Definition
| senile dementia (aka senility) |
|
|
Term
| When does Alzheimer disease normally come on, and what are its demographics? |
|
Definition
| age 50-60 or older, but it can affect younger people; 2 million people in US have it, including 15% of those over 65 and 1/2 of those over 85; causes 100000 deaths every year |
|
|
Term
|
Definition
| recurrent incidents of demyelination that affects axons in the optic nerve, brain, and spinal cord |
|
|
Term
| What are the symptoms of MS? |
|
Definition
| partial loss of vision and problems with speech, balance, and general motor coordination including bowel and bladder control |
|
|
Term
|
Definition
| it's progressive in 1/3 of cases, progressing after each incident; the 1st attack is usually among 30-40 year olds and is 1.5x more likely in women |
|
|
