Neurology, The Nervous System, and Atrophy
Neurology, The Nervous System, and Atrophy HES 1823 004
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This 6 page Class Notes was uploaded by Tay-La Notetaker on Saturday October 1, 2016. The Class Notes belongs to HES 1823 004 at University of Oklahoma taught by Xin Ye in Fall 2016. Since its upload, it has received 9 views. For similar materials see Scientific Principles of Health and Disease in Health and Exercise Science at University of Oklahoma.
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Date Created: 10/01/16
TayLa Jackson Professor Jennifer Russell Health and Disease Week 6 (9/269/28) Neurology Anatomy and Physiology AND The Nervous System Neurons: are the basic unit of the Nervous System and they have extreme longevity and a high metabolic rate. Structure of a Neuron o Cell Body: cell maintenance o Dendrites: receive and conduct impulses to the cell body. o Axon: the nerve fiber that carries impulses away from the cell body and are covered in Schwann cells (these form the Myelin Sheath along the axon. The Myelin Sheath is a whitish, fatty, and segmented substance on the axons of cells to insulate their fibers. The gaps in the sheath are called “Nodes of Ranvier” it speeds the rate of signal transmission o Synapse: the contact points between two neurons. The gap between neurons where information transfer takes place. Two parts: Axon terminal of presynaptic neuron containing synaptic vesicles which carry neurotransmitter molecules. Neurotransmitter receptor region on membrane of postsynaptic neuron. They generate electrical signals that move from one part of the cell to another. This causes communication of two cells by an axon (or other parts of the cell) communicating with the dendrite of another cell. There are 3 types of neurons: Sensory, Motor, and Interneuron. Neurotransmitters: chemical messengers released by electrical signals that pass those signals to other cells. Serve as integrators because their output reflects the balance of inputs om thousands of other neurons hat communicate with them. The Nervous System controls internal environment (with the endocrine system), voluntary control of movements, spinal cord reflexes, and the assimilation of experiences necessary for memory and leaning. Broken in 2 :rts o Central Nervous System (CNS) Brain and Spinal Cord Comprised of neurons o Peripheral Nervous System (PNS) Comprised of neurons outside of the CNS There are 4 large opening in the brain known as ventricles that are filled with cerebrospinal fluid to cushion the brain and which are constantly replaced. Brain Subdivisions: Forebrain: composed of the Cerebrum and the Diencephalon. o Largest component of forebrain is Cerebrum (83% of total mass) Covered by cerebral cortex. (area that “makes humans human”) Contains several functional areas: motor, somatosensory, auditory, visual, and association Primary Sensory areas. These control language, memory, and learning. 4 lobes: Frontal, Parietal, Occipital, Temporal Underneath is the central core of the forebrain, the diencephalon. Primary Sensory Cortices: Somatosensory: Located in Parietal Lobe and receives impulses on pain, temperature, touch, and vibration. Visual: Located in Occipital Lobe and receives information about vision. Auditory: Located in Temporal Lobe and receives information about sound. Language Centers: Broca’s Area Important for generating words and damage to this area means people can understand words but can’t generate them. Wernicke’s Area Important for hearing and understanding words and damage to this area causes people to add inappropriate words or phrases to their speech. Association Areas Located adjacent to the primary cortex and integrates information related to a single sense. Motor Association Areas integrates information related to movement. Multimodal Association Areas integrate information from all senses and decide how to respond. Then signal is sent to the Primary Motor Cortex. Diencephalon: composed of Thalamus Involved in arousal and attention Sensory/motor input goes through thalamus before cortex. Hypothalamus Major endocrine center Controls homeostasis Brainstem: composed of midbrain, pons, and medulla oblongata. o 2.5% of total mass o Responsible for basic mechanisms of life Sleep and wakefulness Cardiovascular and respiratory functions Regulation of posture and balance o Relays information from periphery to brain and vice versa. o Contains “reticular formation” Cerebellum o ~11% of total mass o Coordinates ongoing movements and learns new ones o Receives input from structures of body related to movements. Peripheral Nervous Syste consists of neurons outside of the CNS. Sensor Division has afferent fibers that transmit impulses from receptors to CNS. (Ex. Feeling Cold) Motor Division has efferent fibers that transmit impulses from CNS to effector organs. (Ex. Muscle Contraction) Autonomic Nervous System Sympathetic Division: Fight or Flight Parasympathetic Division: Rest and Digest Atrophy and Sarcopenia o Muscle Atrophy is the wasting away or loss of muscle. Conditions: 1 . Wasting unintentional loss of weight both fat and fat free typically caused by inadequate diet. 2 . Cachexia loss of weight, muscle, and appetite from someone who isn’t trying to lose weight. Cn reverse nutritionally but is likely caused by inflammatory cytokines. 3. Sarcopenia (Greek for “poverty of Flesh”) intrinsic agerelated process that occurs in absence of disease and can be accelerated by inactivity and poor nutrition. o Age related disease that includes loss of strength, function, and decline in quantity and quality of muscle mass. o # of muscle fibers will begin to decrease after the mid20’s and after 30, adults lose ~38% of their muscle mass per decade. o Motorneurons that control the skeletal muscles also begin to decrease in number. Prevalence: o Currently affects 20% of adults below the age of 70. o >50% of adults 80+ years. Consequences: o Decreased resting expenditure (Lower metabolism) o Higher risk of disabilities which means loss of balance which can lead to more falls. o Higher mortality rate. There are two models for Sarcopenia: o Traditional Model Sarcopenia is a slow, insidious process o Catabolic Rest Model (Bed Rest) Inactivityinduced muscle loss mass affects lower body and is most rapid in the first days and week of inactivity. Assessing Muscle in the Body: Muscle Composition : Fiber type, size, and number. o Muscle Quality: Ratio of strength to mass in upper and lower extremities. Body Composition: how much muscle mass is in the body. Sarcopenia can be assessed with a DEXA Assessment. Aging Muscle 1. Loss in fiber size and number 2. More pronounced Type II fiber atrophy and relative increase in percent of type I but decrease in type II cross sectional area and fiber number. 3. Loss of motor units a. Motor unit remodeling may occur which leads to slower and less force production and not as efficient with control of your movements. 4. Collectively leads to a loss of strength and power. Factors in Sarcopenia 1. Decrease of sex hormones (Testosterone) 2. Decrease levels of anabolic hormones 3. Increase cytokine production 4. Accumulation of reactive oxygen species Iron accumulation in muscles causing oxidative stress. 5. Physical Inactivity “Use it or lose it” 6. Malnutrition 7. Smoking Protein Synthesis and Muscle Loss 1. Muscle mass is determined by the rates of the muscle protein synthesis and the muscle protein degradation. MPS=MPD: no change in mass MPS<MPD: loss of muscle MPS>MPD: gain muscle (hypertrophy) Smoking impairs MPS and increases the expression of genes associated with impaired muscular maintenance. You can prevent Sarcopenia by being physically active, dieting, and hormone replacement.
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