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Controlling Skeletal
Chapter 14 - A & P Lecture
| Question | Answer |
|---|---|
| The motor system is responsible for .... | all movement in the body |
| motor system functions: | Maintain posture and balance Move: limbs trunk head eyes |
| motor system enables: | facial expression speech |
| Two Types of Movement: | Reflexes & Voluntary Movements |
| All skeletal muscle control depends on two neurons working in sequence: | Upper Motor Neurons & Lower Motor Neurons |
| Upper Motor Neurons | Located in the brain Initiate and plan movement Send signals downward |
| Lower Motor Neurons | Located in: anterior horn of spinal cord cranial nerve nuclei Exit the CNS → go to muscles Directly stimulate muscle contraction |
| How Voluntary Movement Happens | Step 1: Planning (cerebral cortex plans movement) Step 2: Command (upper motor neurons send signals) Step 3: Execution (Lower motor neurons receive signal) |
| Primary Motor Cortex | Main output center ~30% of upper motor neurons originate here |
| Premotor Area | Plans and organizes movement Active before movement begins |
| Prefrontal Cortex | Handles: motivation decision-making emotional context This is why movement is tied to intention and behavior. |
| two major descending systems: | Direct Pathways (Pyramidal System) & Indirect Pathways (Extrapyramidal System) |
| Direct Pathways Function: | Precise, skilled, voluntary movement Especially: hands face |
| Direct Pathways feature: | Upper motor neurons synapse directly with lower motor neurons |
| Direct Pathways Two main tracts: | Corticospinal Tract & Corticobulbar Tract |
| Corticospinal Tract | Controls movements below the head Especially fine motor control (e.g., fingers) |
| Corticobulbar Tract | Controls head and face Example: facial expressions chewing |
| Indirect Pathways Function: | Less precise Controls: posture, balance, automatic movements |
| Indirect Pathways features: | Synapse in intermediate nuclei |
| Indirect Pathways Major tracts: | Rubrospinal, Vestibulospinal, Reticulospinal, Tectospinal |
| Rubrospinal | Fine motor control of upper limbs Works with cerebellum |
| Vestibulospinal | Maintains balance and posture Activates extensor muscles Example: catching yourself when falling |
| Reticulospinal | Posture and walking |
| Tectospinal | Reflex head movements to: light/sound |
| The basal nuclei .... | refine movement before it happens |
| basal nuclei functions: | Plan and coordinate movement Regulate posture Balance muscle activity |
| basal nuclei two key roles: | Stimulatory & Inhibitory |
| Stimulatory | Initiate movement Example: standing up |
| Inhibitory | Suppress unwanted movement Prevent opposing muscles from interfering |
| The cerebellum ensures movements are smooth, accurate, .... | and coordinated. |
| Cerebellum Core functions: | Maintain muscle tone Control balance Coordinate eye movements |
| Cerebellum Three functional regions: | Vestibulocerebellum, Spinocerebellum, Cerebrocerebellum |
| Vestibulocerebellum | Balance |
| Spinocerebellum | Compares intended vs actual movement Adjusts in real time |
| Cerebrocerebellum | Plans complex, rapid movements Involved in: skill learning timing rhythm |
| Cerebellar Dysfunction Damage leads to: | Decreased muscle tone Poor balance Overshooting movements (dysmetria) Intention tremor (shaking during movement) |
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