BME 732 - The Motor Cortex

medicineman's version from 2015-10-06 02:21

Central Nervous System

Question Answer
CNS main cell typesNeurons and glia
Neurons Conduct electrical impulses and form the basis of neural networks. Communicate with neighboring neurons via axons
Glial cellsForm support matrix for neurons. 80-85% of brain cells are glial cells
InterneuronsDo not exit the CNS
Seven parts of the CNS1. Spinal cord 2. Medulla 3. Pons 4. Cerebellum 5. Midbrain 6. Diencephalon 7. Cerebral hemisphere
1. Spinal cordLocomotion, reflex, sensory and motor processing
2. Medulla Autonomic function: digestion, breathing, heart rate. Sleep function: maintaining quiet breathing
3. PonsControl of posture and balance
4. CerebellumLearning, memory, and control of movement
Cortical laminationThe neocortex is divided into 6 layers: 1-4 communicate within the cerebral cortex, 5-6 send information out of the brain
Gyrus (pl. gyri)A ridge on the cerebral cortex
Sulcus (pl. sulci)A depression or groove in the cerebral cortex

Reference Planes

Question Answer
Horizontal (transverse)Divides the body into superior and inferior parts
Frontal (coronal)Divides the body into ventral and dorsal sections
Sagittal Divides the body into left and right halves
VentralAnterior or belly
Dorsal Posterior or back
RostralSituated near the front end of the body
CaudalSituated near the back end of the body (tail)

Motor Control

Question Answer
Motor control hierarchyStrategy-high, involves association areas and basal ganglia. Tactics-middle, involve motor cortex. Execution-low, involves brain stem and spinal cord
Posterior parietal cortexAlign proprioception of arm with vision of hand. Computes hand and target position in fixation coordinates
Premotor cortexCalculates displacement of the hand in order to reach the target position
Primary motor cortexTransforms the desired movement to muscle activity patterns and sends this command to the brain. Damage reduces speed, accuracy, and force of movements. Damage does not cause paralysis
Secondary motor cortexInput mainly from association cortex and output mainly to primary motor cortex. Two supplementary motor areas: SMA and preSMA
SomatotopyPoint-for-point correspondence of an area of the body to a specific point on the CNS. More of the cortex is devoted to parts that make many movements
AsteriognosisFailure to identify objects by touch
Output to musclesVia ventral root
Ventromedial systemBalance, posture, and controlling head and eye movements. Important for muscles of the legs and trunk needed for walking
Dorsolateral systemControlling movement of upper limbs and extremities, such as fingers and toes, as well as facial muscles

Somatic Sensory System

Question Answer
SkinSensation of touch begins at the skin. Largest sensory organ. Hairy and glabrous. Most sensory receptors are mechanoreceptors
Pacinian corpusclesPressure, stretch, poorly localized sensations. Under pressure the capsule compresses, axon terminal is deformed, channels open, receptor potential activates transmitter
Ruffini's endingsPressure, vibrations
Meissner's corpusclesVery small receptive fields in hairless skin only (fingers and lips). Superficial touch, well localized
Merkel's disksSmall receptive fields, skin indentations
Free nerve endings, hair folliclesMost common. Temperature, pain, pressure
Speed of action potential conductionDetermined by diameter of axon and myelin. Larger diameter, faster conduction. Pain and temperature slow, touch fast.
Input to primary somatosensory areaVia the dorsal root
Dorsal spinothalamic tractProprioception and hapsis. Crosses in medulla
Ventral spinothalamic tractNocioceptive information. Crosses over in the spinal cord
ProprioceptionBody awareness and position in space
HapsisSensation of fine touch and pressure
NocioceptionPerception of pain
Sensorimotor integrationAssociation cortex > secondary motor cortex > primary motor cortex > brain stem > spine

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