Week 2 and 3
Week 2 and 3 PGY 451LEC
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This 5 page Bundle was uploaded by Ndidiamaka Okorozo on Saturday September 19, 2015. The Bundle belongs to PGY 451LEC at University at Buffalo taught by Baizer, J S in Fall 2015. Since its upload, it has received 24 views. For similar materials see Human Physiology I in Physiology at University at Buffalo.
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Date Created: 09/19/15
PAIN Pain is relatively different because it involves an emotional component it39s a strong determinant of factor of behavior and the link between stimulus and response varies Strong stimulus can produce no pain because of excitement No stimulus can produce pain in cases of chronic pain syndrome 0 Example is Phantom Limb Pain where there is alteration of processing of the pain signals by emotional or cognitive state Transduction Stimulus of pain extreme temperatures result in tissue damage which causes release of chemical mediators that act on the endings of nociceptors pain bers The transmitter release by the bers is called Substance P A branch with substance P divides into 3 one sent to the blood vessel to increase blood ow in lesion site second goes to mast cell which activates the release of histamine and third goes to the lesion site where serotonin prostaglandin and bradykinin are present Histamine produced from mast cell goes to the lesion site too and helps with better activation of Substance P Pain fibers A6 and C fibers are chemoreceptors Chemical mediators serotonin bradykinin prostaglandin and histamine indirectly Hyperalgesia increases sensitivity to pain dues to tissue damage Ex sunburn Pathway Tracts of Lissauer ensures that information is distributed up and down the spinal cord Pain bers synapse on cells in dorsal horn of the spinal cord These cells send their axons across the midline to ascend in anterolateral tracts At the level of spinal cord Information about pain and temperature is of the contralateral side Anterolateral pathway leads to the reticular formation medulla l reticular formation of pons D thalamus mid brain D cingulate cortex and somatosensory cortex in Parietal Lobe Referred Pain tissue damage on internal organ is thought to be from surface of skin overlying that organ There is a convergence of pain signals coming from the skin and intestines to the second order dorsal neuron Endogenous Pain control mechanism of how brain modi es pain input 1 Transmitter and receptors Opiates and receptors are at key sites along pain pathways gt Spinal cord dorsal horn gt Brainstem reticular formation gt Frontal lobes Opiate receptors 6delta umu K kappa Endogenous Opioid Peptide Transmitter Receptor EnkephaHns u6 Dynorphins K Betaendorphin u 6 Feedback system with pain as input releases these opiates 2 Descending control of pain 2 brainstem nuclei a Nucleus raphe Magnus Serotonin Nucleus in NRM send their axons back to the dorsal horn D activate dorsal horn interneurons by releasing inhibitory enkephalins l synapse on incoming pain bers to decrease their synapse strength gt This is done at the level of spinal cord at rst synapse b Second pathway locus ceruleus norepinephrine From the brain to the dorsal hon almost same pathway as the above MOTOR SYSTEM Motor control not intuitive Motor system motor hierarchy l motor cortex at top and muscles at the bottom However all structures work together in movement Function Coordination Posture ln coordination there are changes in joint angle and muscle length Flexion l Decrease in joint angle l Contractionshortening of exor l Stretchinglengthening of extensor Extension Increase in joint angle l Contractionshortening of extensor l Stretching lengthening of exor Agonist muscle doing the movement Antagonist muscle with opposite action at the joint Synergist all muscle doing the same action at a joint Posture resisting forces of gravity D carried out by extensors antigravity muscles gt Antagonist exors Position xation elimination of unwanted movement at a joint in order to achieve desired movement Muscles vary in properties 1 Force amount generated by each muscle 2 Resistance to fatigues 3 Speed of contraction how fast they respond to stimuli 4 Fineness of control important for nger and eyeball movements Force resistance and speed result from the muscle s structure while neness of control is as a result of structure and pattern of innervation Muscle Fiber Types 1 Fast Twitch a FF fast fatigable large force fast contraction time fatigue readily Biochemical differences white muscle b FR fast resistant Large force fast contraction time more resistant to fatigue Biochemical differences white muscle 2 Slow Twitch a S slow Least force slowest contraction time most resistant to fatigue Red muscle Cannot increase the number of muscle bers or change muscle ber with training D xed composition Each muscle has different of ber types But composition of a particular muscle may vary among individuals may correlate with athletic ability Motor innervation Alpha oz motor neuron lower motor neuron axons have large diameter myelinated Acx fibers 12 20 um 70 120ms Each innervate muscle fibers 2100039s depends on size Muscle ber receives innervation from one and only one motoneuron Range of size of motoneurons Larger MN39s larger Cell body larger diameter l Axons with more branches D higher number of muscle bers 0 Larger MN39s larger Cell body larger diameter l Axons with more branches D higher number of muscle bers ALS MN s release chemical called trophic factors The absence of these trophic factors which are essentials for the health of muscles leads to ALS Because the death of motoneuron leads to muscle deathatrophy Motoneuron Pool MN39s innervation particular muscle are divided in segments which are called pools Composed of different range of sizes The Motor Unit A single motoneuron and all its muscle bers innervated by it Its size depends on the size of the motoneurons Large MN s D Larger Muscle Fibers D large motor unit Same type of muscle ber in a motor unit 0 Average Motor unit size differs among muscles gt Fine control Smaller gt Force speed Larger Size Principle Motor units are recruited in order of increasing size smallest rst and largest last Drop out happens in reverse order S bers in use more of the time Feedback Info from muscle 1 Muscle length receptor is the muscle spindle Muscle Spindle is a connective tissue sheath containing 212 specialized muscle bers called intrafusal bers Ordinary muscle bers are extrafusal bers a Maintained length b Rate of change of length 2 Muscle force receptor is the Golgi Tendon Organ GTO gt Receptors for gamma attached in series with muscle sensory innervation for lb ber 12 20pm diameter and 70120msec conduction velocity lb bers crunch on axons of gamma motor neurons depolarize them creating action potentials lntrafusal bers have contractile poles and noncontractile centers a Nuclear bag dynamic b Nuclear chain static Types of sensory bers Group IA 1220um 70120 msec innervate all intrafusal bers has primaryannulospiral endings Carry info about maintained muscle length static and rate of change of muscle length Group II 512um 3070 msec lnnervate only nuclear chain bers has secondary ower spray endings Carry info about maintained muscle length static Transduction in the spindle Muscle Stretched D Endings become polarized D action potentials generated Motor innervation of spindle Gamma MN39s quotfusimotorquot neurons 5 12pm diameter 3070msec conduction velocity Cell bodies are in ventral horn of spinal cord Ensure steady action potential Problem Muscle shortens D Spindle goes slack D No stretch on spindles D No sensory input Solution with gamma MN39s innervating the contractile poles of spindle it facilitates the contraction of spindle while muscle shortens
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