BIPN 150 Midterm 1 Notes

BIPN 150 Midterm 1 Notes - BIPN 150 Midterm 1 Notes Motor...

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BIPN 150 Midterm 1 Notes Motor Neurons 1. Motor units are composed of the a-alpha1 motor neuron and the muscle fibers that it innervates 2. Each MN contacts many muscle fibers 3. Motor neurons are found in ventral horn of spinal cord Local Motor Circuits 1. Negative feedback of muscle tension by Golgi tendon organs prevents muscle from generating excess tension 2. Upper motor neurons are found in primary motor cortex next to central sulcus in frontal lobe 3. Lower motor neurons follow lateral cortical spinal tract: motor cortex decusation in medulla cortical spinal tract muscle contraction 4. Lower motor neurons connect brainstem and cord to muscle fibers and brings nerve impulses from UMNs to muscles 5. Glutamate released from upper motor neurons triggers depolarization in lower motor neurons of anterior horns of spinal cord which causes AP to propagate down axon to NMJ making muscle contract Four Contributions to Motor Control 1. Four contributiona to motor control come locally from spinal cord/brain stem, descending systems, cerebellum and the basal ganglia 2. Brain stem/ spinal cord are involved in local circuit neurons where you have LMN integration where circuit receives sensory imput initiating the contraction 3. Descending systems involve UMNs in the motor cortex for planning, initiating and directing voluntary movements. An example is the cortical spinal tract from motor cortex to LMNs in ventral horns for fine voluntary motor control of limbs 4. UMN lesions are indicated by spasticity, muscle weakness and babinski sign 5. Cerebellum also contributes to motor control via sensory motor coordination of ongoing movement 6. Lastly basal ganglia gates proper initiation of movement Signs/Symptims of Upper and Lower MN lesions 1. Upper motor lesions can be detected by weakness, spasticity, hypractive reflexes, clonus (where certain muscles are continuosly contracting) and an increase in tone 2. UMN also be detected by babinsky sign and loss of fine voluntary movement 3. LMN lesions can be detected by weakness/paralysis, decrease reflexes, hypoactivity and decreased tone, also fasiculations, fibrillations and severe
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muscle atrophy Amyotropic Lateral Sclerosis (ALS) FACTS 1. Has a mean age onset of 55 years 2. Fatal (4-5 yrs) 3. Affects both upper and lower MNs, where affecting UMNs affects cortical spinal tract leading to spasticity and affecting LMNs affects those in ventral horn of spinal cord and leads to severe muscle atrophy 4. Hallmark of ALS is muscle denervation and atrophy due to loss of spinal motor neurons and degenerations of brain MNs which causes spasticity 5. 2/3 of damage begins in arms and legs and 1/3 affects the brain stem (bulbar) which connects cerebral cortex to the brainstem and controls muscles of face, head and neck. 6.
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BIPN 150 Midterm 1 Notes - BIPN 150 Midterm 1 Notes Motor...

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