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43 Cards in this Set
- Front
- Back
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3 types of white matter fibers of telencephalon
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1. Association fibers (connect w/i hemisphere)
2. Commissural fibers (Corpus Callosum)- connect btw hemispheres 3. Projection fibers- project for long distances (ex. to spinal cord) |
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Telencephalon
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includes:
Cerebral Cortex Basal Ganglia Limbic System 6 Lobes: 1. Frontal lobe (motor & higher brain function) 2. Parietal lobe 3. Temporal lobe 4. Occipital lobe 5. Insular lobe 6. Limbic lobe |
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Layer of Cerebral Cortex
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Neocortex (develops last)
Paleocortex (develops 2nd) Archicortex (develops first) |
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Association fibers
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white matter of cerebral hemisphere
-connect areas of cortex w/i same hemisphere -long assoc. fibers (connect adjacent gyri) -short assoc. fibers (connect more distant areas) |
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Commissural Fibers
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white matter of cerebral hemisphere
-integrate info btw the 2 hemispheres -Corpus Callosum (largest commissural fibers) -smaller commissural bundles |
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Projection Fibers
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white matter of cerebral hemisphere
-carry info beyond cortex (from cortex to brainstem, muscles, spinal cord etc) -Corticopetal fibers= axons that originate outside telencephalon and terminate in cortex -Corticofugal fibers= axons that arise in cortex and terminate in downstream targets |
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Internal Capsule
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white matter
-extends from cortex to brainstem -has both ascending and descending fibers -all axons that link the thalamus & cortex pass through here *Anterior limb- most fibers to and from thalamus *Genu- CN nuclei to brainstem *Posterior limb- from cortex to brainstem and from cortex to spinal cord |
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Basal Ganglia
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Includes:
Striatum (Caudate & Putamen) Globus Pallidus Substantia Nigra *damage to BG causes mvmt disorders NOT paralysis -involuntary mvmts -Parkinsons disease (w/damage to substantia nigra |
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Limbic System
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2 main components:
Hippocampus & Amygdala -responsible for memory -damage causes changes in eating, sexual behaviors and agression |
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What are the 3 functional areas of the Cerebral Cortex?
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Motor areas
Sensory areas Association areas (communication & integration btw lobes- allows you to recognize things) |
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What are Brodmann Areas?
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structurally distinct areas of the cortex
-#'d areas that have different histology and function -each # has different function |
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Primary Sensory Area of Cortex
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receives sensory info from thalamus
****primary somatosensory area ***Areas 3, 1, 2 = involved with conscious awareness of general somatic senses -primary auditory area -primary vestibular area -primary visual cortex |
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Sensory Association Areas of Cotex
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analyze sensory input from thalamus and primary sensory cortex
***somatosensory assoc. area ***Areas 5, 7 -integrates tactile and proprioceptive info from muscles, skin etc |
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Primary Motor Cortex
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controls contralateral voluntary movements
***Area 4 -trunk muscles are represented bilaterally (pts present w/bilateral trunk weakness even if damage is only on one side) |
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Cortical Motor Planning Areas of Cortex
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-Supplementary Motor Area (area 6, medial part)
*initiation of mvmt, orientation planning, bimanual mvmts (carrying something heavy in one hand, balance out other side of body) -Premotor Area (area 6, lateral part) *controls trunk muscles, postural adjustments -Broca's Area = speech *dominant hemisphere= opp side of dominant hand -if you're R handed, Broca's area is in L hemisphere -if you're L handed, B area could be in either R or L -L hemisphere lesion has a good chance of affecting speech |
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Brodmann Areas we need to know
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Primary Sensory: 3, 1, 2
Sensory Association: 5, 7 Primary Motor: 4 Cortical Motor Planning: 6, 8 |
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Diencephalon
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Main processing center for information going to cerebral cortex
includes: Thalamus/Dorsal Thalamus, Hypothalamus, Epithalamus, Ventral/Subthalamus |
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Thalamus
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makes up 80% of diencephalon
-most sensory input going to cortex stops at thalamus first -nuclei amplify or tone down signals before they go to cortex if injured: total lesion= no relay of sensory signals partial lesion= lose sensation to specific body part (since thalamus is divided by y-shaped white matter) |
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Thalamic pain syndrome
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pain comes from thalamus
-a non-painful stimulus (light touch) is processed as pain in thalamus sending wrong info to cortex |
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Projections btw thalamus and cortex
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-Thalamocortical axons
-Corticothalamic axons *relay info from BG (motor planning) and cerebellum (balance & coordination) |
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Hypothalamus
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Contains nuclei primarily related to visceral function
-sends info to thalamus about: *autonomic nervous system *emotional response *emotional expression (anger, pleasure etc) *regulation of hunger and thirst |
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Ventral Thalamus/Subthalamus
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Functions more along the line of BG but structurally close to thalamus
-received input from motor cortex -involved in regulation of mvmt -facilitates BG function Lesion= hemiballismus (like seizure on 1/2 of body, neck region) |
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Epithalamus
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-forms roof of 3rd ventricle
-part of endocrine system -secretes melatonin (go to sleep) |
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What happens w/lesions to Cortex, Cerebellum and Basal Ganglia?
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Cortex --> paralysis
Cerebellum --> mvmt will be uncoordinated and jerky Basal Ganglia --> difficulty starting and stopping mvmt, slow mvmt, not smooth (Parkinsons) |
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Symptoms of UMNL & LMNL
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UMNL= hypertonia or hyperreflexia
LMNL= hypotonia or hyporeflexia |
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Lower Motor Neurons
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From Anterior Horn Cells to muscle
-activity is influenced by peripheral sensory input and supraspinal input (higher up) |
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AHCs
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located in gray matter of spinal cord
*only direct link of NS to musculoskeletal system -receive feedback from the muscles they control |
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Locations of ACHs
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arranged according to muscle groups they innervate:
-motor neurons of flexor muscles are more posterior in Anterior horn -motor neurons of extensor muscles are more anterior is Anterior horn -neurons that innervate proximal & paravertebral muscles are more medial -neurons that innervate the limbs are more lateral |
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Types if AHCs
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Alpha Motor Neurons: innervate extrafusal muscle fibers (outer bundles)
Gamma Motor Neurons: innervate intrafusal muscle fibers (within Muscle Spindle) |
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What are interneurons?
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regulate anterior horn cells (both Alpha & Gamma motor neurons)
-influence can be excitatory of inhibitory |
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Size of motor unit in relation to size of muscle
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-large weight-bearing muscles have large motor units
-muscles that control fine mvmts (fingers, eyes) have small motor units |
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Types of motor units
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1. Slow Twitch (type I)
-aerobic -longer contraction time -red fibers -low force -fatigue resistant 2. Fast Twitch (type II) -rapid contraction times -large force -quickly fatigued -white fibers |
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Size Principle
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when a group of motor neurons in Ant Horn are activated smaller cells are recruited first. If more help is needed, larger cells are recruited later due to increased input
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2 types of muscle spindle fibers
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1. Nuclear bag fibers- cell nuclei are clustered together centrally
-Dynamic Bag fibers (sensitive to RATE of CHANGE in length) -Static Bag fibers (sensitive to CHANGE in length) 2. Molecular chain nuclei- nuclei arranged in a line (sensitive to CHANGE in length *sensory portions located centrally *contractile portions located distally (when contraction occurs, central portion is stretch btw 2 ends) |
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Innervation of Muscle Spindle fibers
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Sensory Nerve Fibers
-primary endings of *Type Ia -secondary endings of *Type II Motor Nerve Fibers: Gamma Motor Nerve Fibers -Dynamic gamma motor neurons (innervate dynamic bag fibers) -Static gamma motor neurons (innervate static bag fibers and nuclear chain fibers) |
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Primary Type Ia fibers
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Sensory Nerve Fibers of muscle spindle
-associated w/nuclear bag fibers and nuclear chain fibers *sensitive to RATE of CHANGE in length -Phasic Discharge: maximal discharge during quick stretches, fades quickley -Tonic Discharge: sustainded during constant stretch |
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Secondary Type II fibers
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Sensory nerve fibers of muscle spindle
-associated w/nuclear chain fibers -sensitive only to CHANGE in length -has tonic discharge |
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2 types of Gamma Motor Nerve Fibers of muscle spindle
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-each type of intrafusal fiber is innervated by a gamma motor neuron
1. Dynamic gamma motor neurons (innervate dynamic nuclear bag fibers) 2. Static gamma motor neurons (innervate static nuclear bag & nuclear chain fibers) |
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What do Alpha Motor Neurons innervate?
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extrafusal muscle fibers
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Explain the Gamma Loop
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-Supraspinal activation
-causes gamma motor neurons to contract -which stretch the muscle spindle (intrafusal fibers) -which sends info to CNS -which increases activity of Ia fibers (sensory) -activates alpha motor neurons to contract muscles |
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Alpha-Gamma Coactivation
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when extrafusal fibers (alpha mn) contract, signals are sent o gamma mns to contract to shorten the spindle to keep the spindle "on-line" to be able to continue to detect changes in muscle length
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Function of Golgi Tendon Organ
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-sends info to AHCs through Ib fibers about amount of muscle contraction (prevents muscle from pulling tendon off bone)
-if muscle is contracted too much, inhibitory info is sent to alpha motor neurons to inhibit contraction -if more contraction is needed, gamma motor neurons are activated to cause more contraction through Ia fibers ***GTO is exactly opposite in function from the muscle spindle |
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Difference in function btw GTO and Muscle Spindle
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-muscle spindle activation leads to excitation of extrafusal muscle fibers
-GTO activation leads to inhibition of extrafusal muscle fibers |
