FSU PSB 2000 - EXAM #3 INCLASS/ONLINE LECTURE SUMMARIES

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EXAM #3 INCLASS/ONLINE LECTURE SUMMARIES CHAPTER 8 Movement MUSCLES1. Smooth Muscle- Found in internal organs. Are long, thin cells2. Skeletal/Striated Muscle- Are the main movers. Are Long cylindrical fibers w/ stripes3. Cardiac Muscle- Found in heart. Fused fibers contract together. Each fiber innervated by one motor neuron. One motor neuron innervates many fibers. MOTOR UNIT - smallest functional unit. Neuron meets fiber at NEUROMUSCULAR JUNCTION• acetylcholine - excites muscle/contraction.• Antagonistic muscles work together to move perfect amount FLEXORS vs. EXTENSORSMYASTHENIA GRAVIS - Autoimmune Disorder. Antibodies act against ACh receptors• Symptoms – progressive weakness. rapid fatigue of skeletal muscles• Physiological Basis – fewer ACh receptors. Morphological changes at synapse– action of : ACETYLCHOLINESTERASE - lower likelihood ACh reaches enough receptors• Treatments – immunosuppressants. Acetylcholinesterase inhibitors• FAST-TWITCH FIBERS – Contract and relax rapidly. Anaerobic. Fatigue rapidly. Generate greatest force (EX: sprinting)• SLOW-TWITCH FIBERS – longer contraction time. Aerobic. Resistant to fatigue. Generate less force (EX: walking)PROPRIOCEPTORS - Sensitive to position/movement of muscles. Detect stretch/tension. Allow spinal cord to adjust signal.• Two primary types of proprioceptors: - Muscle Spindles - Golgi Tendon OrgansMUSCLE SPINDLEs - Parallel to muscle. Senses Stretch::: Muscle stretched -> Signal to motor neuron in spinal cord -> Muscle contraction. • Negative Feedback = stretch causes contraction. Stimulates STRETCH REFLEX GOLGI TENDON ORGANS - Located in tendons (connecting muscles to bone). Senses Tension. Vigorous muscle contraction::: Signal to spinal cord -> inhibitory interneurons -> Inhibit motor neuron (muscle contraction)• Negative Feedback = tension causes muscle relaxation. Protects against too vigorous a contractionMOVEMENT- Reflexes – consistent, automatic responses to stimuli. EX: Babinski reflex (in babies; when foot touched -> toes curl)– allied reflexes - occur together/elicit each other• Ballistic Movements – executed as a whole. cannot be corrected/not sensitive to feedback. (EX: reflexes)MOTOR PROGRAMS - Neural circuits w/ fixed sequence of movements. Built-in (Ex: rodent grooming, yawning) vs. learned (EX: gymnast, pianist)• Central Pattern Generators: Neural mechanisms that generate rhythmic motor patterns(EX: wet dog shake. wing flapping)SOMEMAJOR MOTOR AREAS OF THE BRAINFOREBRAIN = • Cortex • Basal Ganglia • CerebellumMIDBRAIN = • Substantia Nigra • Red NucleusHINDBRAIN = • Reticular Formation • Reticular Formation • Vestibular NucleusMAJOR MOTOR AREAS OF THE BRAIN• Primary Motor Cortex - Involved with coordinated movements in several muscles leading to a specific outcome.• Posterior Parietal Cortex - Involved with coordinating movement through the environment based on visual input.• Prefrontal Cortex / Premotor Cortex - Involved in planning movement.• Supplementary Cortex – Involved in preparation for rapid sequences of movements.PRIMARY MOTOR PATHWAYS TO SPINAL CORDDORSOLATERAL TRACT - Carries axons from primary motor cortex & red nucleus(midbrain) to spinal motor neurons.• Crosses over to the contralateral side at the pyramids in the ventral portion of the anterior medulla (pyramidal tract).• Controls movements of distal limbs including hands fingers and toes.• Courses down the dorsolateral portion of the white matter of the spinal cord.VENTROMEDIAL TRACT - Carries axons from primary motor cortex (& vestibular nucleus/tectum/reticular formation & other cortical areas). Axons synapse on spinal interneurons (and some motor neurons) controlling spinal motor neurons.• Some of the axons cross and others don’t, providing bilateral innervation.• Controls movements of proximal limbs and axial musculature (neck/shoulders/trunk). Involved w/ movements and posture.• Courses down the ventromedial portion of the white matter of the spinal cord.MOTOR FUNCTIONS OF CEREBELLUM - The cerebellum contains more neurons than the rest of the brain combined.• Involved in: Control of rapid ballistic movements (including saccades) • Timing • Establishment of new motor programsCEREBELLAR DAMAGE can lead to trouble:• Tapping a rhythm • Athletics • Speaking and writing • Hand clapping • Typing • Playing musical instruments • Finger-to-nose test • Simple saccadesBASAL GANGLIA• CAUDATE NUCLEUS / PUTAMEN - Primarily input area. Receives info from thalamus and cortex. Also receives dopaminergic projection from the substantia nigra (in midbrain)• GLOBUS PALLIDUS - Primarily an output area. sends info to thalamus, which sends to motor/prefrontal cortex/midbrain.* BASAL GANGLIA - Role still somewhat unclear. Might be involved in: Organization of action sequences into chunks, inhibition of specific motor responses. Basal ganglia role can be known by examining Parkinson’s Disease.PARKINSON’S DISEASE- MUSCLE RIGIDITY/TREMORS • SLOW MOVEMENTS • COGNITIVE DEFICITS• DIFFICULTY INITIATING MOVEMENT • DEPRESSION • AFFECTS 1 IN 100 ABOVE AGE 50* CAUSED BY : Degeneration of the dopaminergic neurons in the substantia. Nigra projecting to caudate nucleus/ putamen.POSSIBLE CAUSES OF PARKINSON’S DISEASE• Early onset (< 50 years) has a genetic component.• Possible environmental influence. Environmental Toxins; e.g.: MPTP converted to MPP; which accumulates in opaminergic neurons and kills them. Cigarette/Caffeine has a protective effect. (less likely w/ smoking/caffeine)TREATMENT FOR PARKINSON’S DISEASE: Unlike dopamine, L-dopa can cross blood-brain barrier where it is absorbed by neurons and can increase dopamine production.• It can’t restore degenerated neurons, however. Effectiveness declines as the disease progresses. Side-effects are a problem.OTHER POSSIBLE TREATMENTS (largely experimental)• Antioxidant drugs to decrease further damage. • Dopaminergic agonists that can cross blood-brain barrier.• Glutamate or adenosine antagonists • Inactivating electrical stimulation of globus pallidus• Neurotrophins to promote growth and survival of neurons. • Drugs that decrease apoptosis. • Fetal tissue transplants• Drugs that block certain calcium channels abundant in elderly brains • Drugs that stimulate cannabinoid receptors.CHAPTER 10 Regulation of Internal States REGULATION OF INTERNAL


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FSU PSB 2000 - EXAM #3 INCLASS/ONLINE LECTURE SUMMARIES

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