Muscle Overview PDF

Muscle overview - One of the four basic tissues of the body Characteristics - Excitability -response to stimulus (nerve impulse - Contactability - shorten in length when stimulated - Extensibility - Stretch when pulled - Elasticity - return to original shape after contraction/ext...

Muscle overview - One of the four basic tissues of the body Characteristics - Excitability -response to stimulus (nerve impulse - Contactability - shorten in length when stimulated - Extensibility - Stretch when pulled - Elasticity - return to original shape after contraction/extension 3 primary function - Provides motion - Maintain posture - Generate heat Skeletal - Controlled by the conscious mind - Moves bones of the skeleton - Voluntary striated muscle - Well-defined group of cells surrounded by fibrous connective sheath - epimysium Tendons - Attach muscle to bones by fibrous tissue bands Aponeurosis - Attach to bones or muscles by broad sheets of fibrous tissue Origin - More stable site - Does not move when muscle contracts Insertion - The site that undergoes the most movement when a muscle contracts Skeletal muscle actions Agonist - prime mover - Directly produces a desired movement Antagonist - Directly opposes the action of an agonist Synergist - The contract at the same time is an agonist to assist its action Fixator - Stabilizes joints to allow other movements Cardiac - Found only in the heart Smooth - Carries out conscious internal movement of the body - Found all over the body Muscle naming conventions Action -superficial digital flexion Shape - deltoid Location - biceps brachii Direction of fibers - rectus abdominis Number of heads or divisions - biceps brachii, triceps brachii, quadriceps brachii Attachment sites - sternocephalicus Cutaneous muscles - Thin broad superficial muscle - Found in connective tissue just beneath the skin - Little or no attachment to bones Head and neck skeletal muscles - Control facial expressions - Enables mastication - Masseter muscle - masseter muscle - Move sensory structures - Support the head - Raise (extend) the head or neck - Splenius and trapezius - Move head laterally - Open and close the jaw - Extend the head and neck and pull the front limb forward - brachiocephalic - Flex the head and neck - sternocephalicus Abdominal skeletal muscles Functions - Support the abdominal organs - Help flex the back - Participate in defecation, urination, parturition, vomiting, and regurgitation - Heave a role in respiration - expiration Arranged in layers - External abdominal oblique muscle - Internal abdominal oblique muscle - Rectus abdominis muscle - Transverse abdominis muscle - Left and right part come together at linea alba Clinical relevance: linea alba Advantages - one cut into abdomen less bleeding less pain Disadvantages - pressure from abdominal organs on incisions Thoracic limb muscles - Functions mainly for locomotion - Superficial muscles of the brachium - Adductor muscles - Latissimus dorsi - Pectoral muscles - Abductor's muscle - Deltoid muscle - Brachial muscles - Flexor and extensor muscles - Carpal and digital muscles  - Flexor and extensor muscles Pelvic limb skeletal muscles - Functions mainly for location - Muscles for the theigh region - Extensor muscles - Gluteal muscles, hamstring, biceps femoris, semimembranosus, semitendinosus - Flexor muscles - Tensor fascia latae, iliopsoas - Muscles of the stifle joint - Extensor muscles - Quadriceps femoris -also assist in flexing the hip - Muscles of the tarsus and digits - Extensor gastrocnemius - achilles tendon , Skeletal muscles of respiration - function to increase and decrease size of thoracic cavity Inspiratory - Diaphragm - External intercostal muscles Expiratory muscles - Internal intercostal muscles - Abdominal muscles Skeletal muscle cell - muscle fiber - Very large quite large and thin - Multinucleated - Sarcolemma - muscle cells membrane - Myofibril- fiber like structures that occupy most of the cytoplasm. Composed of filaments containing actin and myosin - Sarcoplasmic reticulum - organelle for calcium storage - Transverse tubules - system of tubules that extend from the sarcoplasmic reticulum to interior of cell and helps carry nerve impulse - Sarcomere - series of protein filaments that make up contractile units of muscle cells - Many sarcomeres lined up end to end = one myofibril Sarcomere - 2 primary proteins filaments responsible for contraction - Thick dark myosin - Thin light actin Neuromuscular junction - Sites where end of motor nerve fibers connect to muscle fibers - Synaptic vesicles at the end of nerve fiber contain neurotransmitter acetylcholine - Acetylcholine quickly diffuses across the synaptic space and binds to receptors on the sarcolemma Motor unit - One nerve fiber and all the muscle fibers it innervates - Few muscle fibers per motor unit  - The small delicate movement of muscle - Huge numbers of muscle fibers per motor unit - Large powerful movement of muscles Connective tissue - Hold components of muscle together - It contains blood vessels and nerves - Epimysium is continuous with tendons or aponeuroses - Contains adipose tissue - marbling Epimysium - surround groups of fassicles Endomusium - delicate layer that surrounds each muscle fiber Facile - group of muscle fiber that bound together by perimysium Muscular system chapter 8 part 2 Muscle contraction and relaxation Nerve impulses comes down motor nerve fibers Impulse reaches end bulb of nerve fibers Acetylcholine released into synaptic space and binds to receptors on sarcolemma surface Impulse travels along sarcolemma and through T tubules to interior of the cell Impulse reaches sarcoplasmic reticulum Ca++ ions released into sarcoplasm Ca++ diffuses into myofibrils and starts contraction Energy supplied by ATP Sarcoplasmic reticulum begins pumping Ca++ back in again Ca++ is pulled out of myofibril Energy supplied by ATP Contraction stops Muscle returns to original length Both muscles contraction and relaxation requires ATP/energy Clinical relevance - Hypocalcemia - Rapid increase in Ca demand - Initial signs: mild muscle tremors, ataxia, ear twitching - Progress to:recumbancy, flaccid paralysis, tachycardia - smooth muscle paralysis - Untreated: progress to coma or death - Tx: mild: oral Ca - severe : administer Ca iV SLOWLY Mechanics of muscle contraction - Muscle fibers in relaxed state - Actin and myosin filaments slightly overlap - Muscle fibers stimulated to contract - Cross- bridges ratchet back and forth - Actin filaments pulled toward the center of myosin filaments - Sarcomere is shortened - Muscle contraction = shortening of all sarcomeres in muscle fiber Clinical relevance - RIgor Mortis - Latin - stiffness of death - Death ->lack of energy, cells barriers break down - Ca2 spills out of sarcoplasmic reticulum into sarcoplasm - Uses ATP however no regeneration of ATP - Making muscles stuck in contracted position - However not permanent, decomposition causes actin/myosin to break down causing relaxation Characteristics of muscle contraction All or nothing principle - When stimulated, individual muscle fibers contracts completely - or not at all - Nervous system controls number of muscle fibers stimulated Twitch control - A single muscle fiber contraction - Latent phase: brief hesitation between the nerve stimulus and actual contraction - 0.01 seconds - Contracting phase: actual contraction - 0.04 seconds - Relaxation phase: fibers return to original length - 0.05 seconds Muscle contraction Maximum contraction efficiency - When nerve impulses arrive 0.1 second apart - Results in series of complete muscle fiber twitches Smooth sustained muscle contraction - Contractions out of sync with each other - Average out activity of all muscle fibers Chemistry of muscle contraction - ATP provides energy to allow sliding of actin and myosin filaments - Creatine phosphate converts ADP back to ATP - Catabolism of glucose and oxygen help reduce ATP and CP - Glucose stored in muscle as glycogen - Oxygen stores attached to myoglobin Aerobic metabolism - Adequate oxygen supply for energy needs of muscle fibers - Maximum energy extracted from glucose molecule Anaerobic metabolism - Need for oxygen exceeds available supply - Lactic acid formed in incomplete glucose breakdown Heat production - Muscle activity generates heat - Mechanism to eliminate excess heat - panting or sweating - Spasmodic muscle contractions that increases heat production - shivering When stimulated, the body is able to partially contract muscle fibers, allowing for fine motor movements True OR False Cardiac Muscle  - Striated involuntary muscle - Found only in the heart - Small cells with 1 nuclei - Much smaller than skeletal muscle cells - Longer than wide withmultiple branches - Intercalated discs - fastned cells together, transmit impulses from cell to cell Physiology of cardiac muscle - Cells contract with no external stimulation - Groups of cells contract at the rate of the most rapid cell in the group - Contractions are rapid and wavelike - Act as a single unit as opposed to individual cells Cardiac conduction system - Sinoatrial node - Made of cardiac muscle cells - Located in wall of right atrium - Generates to start each heartbeat - Impulses follows controlled path through the heart - Structures in heart transmit delay and redirect - Walls of heart chambers contract in coordinated manner Nerve supply to cardiac muscle - Not needed to initiate contractions - Its purpose is to modify - Heart from 3 systems - Sympathetic system - stimulates heart in fight or flight response - Parasympathetic system - inhibits cardiac function for relaxation and rest Smooth muscle - 2 main forms - Visceral smooth muscle - Large sheet of cells in walls of small hollow organs - Stomach, intestine, uterus and urinary bladder - Multiunit smooth muscle - Small, discrete groups of cells - Iris and ciliary body of the eye, walls of small blood vessels, small airway passages in the lungs Smooth muscle - involuntary muscle - Cells not under conscious control - Cells small and spindle shaped - Single nucleus in the center - Smooth, homogenous appearance - Cells ball up as it contracts Actin and myosin filament sarrange as small contractile units cross cross the cell Dense bodies= structures in smooth muscle where actin and myosin attach Visceral smooth muscle - Found in walls of many soft internal organs - Stomach, intestines, uterus, urinary bladder - Contracts in large, rhythmic waves  - Contracts without external stimulation - Reacts to stretching Innervated from 2 systems - Sympathetic decreases activity - Parasympathetic increases activity Opposite effect than the cardiac muscle - Multiunit smooth muscle - individual smooth cells or smaller groups of cells - Found where small, delicate contractions are needed - Iris and ciliary body of the eye, walls of small blood vessels, and small air passageways in lungs - Contraction requires impulses from autonomic nervous systems Case: Masticatory Myositis - Focal inflammatory myopathy, autoimmune in origin, targets muscle of mastication Symptoms/presentation: - Acute - bilateral swelling of muscles of mastication, pain of palpation, exophthalmos, and inability to open jaw - Chronic - atrophy of muscles, enophthalmos, permanent inability to open the mouth Pathology: masticatory muscles have similar muscle fiber types, the immune system targets these muscles and cause necrosis/ damage Diagnostics: serum antibody, biopsy, CT/MRI Treatment: steroids, do not force open the jaw Monitoring: weight loss, hydration status, relapse possible Prognosis: acute - good, chronic - fair to poor Nervous System part One Nervous system: - Uses chemicals to carry messages - Neurotransmitters produced by neurons - Travel short distances across synapses - Allows the system to react quickly 3 main activities: Sensory functions - Senses change from within and outside the body - Conveys the information to the spinal cord and brain Integrating functions - In the brain and spinal cord - Sensory info received, analyzed, stored, and integrated to produce a response Motor functions - Instructs the body to do something Neurons - Nerve cells - The basic functional unit of the nervous system - Have a high requirement for oxygen - Cannot reproduce but can regenerate cell processes - Have support and protection from neuroglial cells Neuron structure - Central cell body - soma or perikaryon - cell extensions  - Processes: dendrites receive stimuli; axons conduct nerve impulses away from the cell Dendrite cell processes - gray matter - Short, numerous, multi branched - Conduct stimuli toward the cell body -afferent - May receive stimuli from other neurons - May serve as sensory receptors; hea Axon cell - white matter - Single long process - May be covered with myelin - white matter - Conducts nerve impulse away from the cell toward another neuron or effector cells - efferent - Nerve fibers: bundles of axons Myelinated axons - Myelinated axons conduct impulses faster than those with no myelin - Myelin sheath: cell membrane of flail cells tightly wrapped around the axon - Oligodendrocytes: specialized glial cells within the brain and spinal cord - Schwann cells: specialized glial cells surrounding peripheral nerve Myelinated axons: multiple oligodendrocytes or schwann cells cover entire length of axon Nodes of ranvier are the gaps between adjective glial cells Endocrine system: - Uses chemicals to carry messages - Hormones secreted directly into the bloodstream - Travel long distances to reach targets - The body reacts more slowly to changes Central nervous system - brain and spinal cord Organization of the nervous system Central nervous system - Composed of brain and spinal cord - Found along central axis of the body Peripheral nervous system - Components extend away from the central axis outward - Cranial nerves - 12 pairs of nerves originating directly front he brain - Spinal nerves - peripheral nerves that originate from the spinal cord Afferent - Conduct impulses toward the CNS - Also called sensory nerves Efferent nerve fibers - Conducts away from the CNS - Also called motor nerves - Mixed nerve fibers: nerve fibers may contain both kinds of nerves; most nerves in the PNS are mixed nerves - Nerve fibers= bundles of axons that make up chord-like nerves Autonomic nervous system - Coordination of autonomic body functions - Examples: stimulating the release of digestive juices in response to ingestion of a meal Somatic nervous system - Conscious or voluntary control of skeletal muscles  - Examples: turning your head to look at something Neuron function: depolarization and Repolarization Neuron function Sodium - potassium pump - Specialized molecule to help maintain cell resting state - Pumps Na+ to the outside - Pumps K+ to the inside Resting membrane potential - Difference in electrical charge across neuron membrane - Net negative charge - Neuron is not being stimulated - NA+ has pumped out of the cell - K+pumped into the cell Depolarization - Neuron receives external stimulus - Na+ channel opens on neuron cell membrane - Na+ ions flow into cell by passive diffusion - Charge now positive inside cell - Switching of electrical charge from negative to positive is known as action potential Beginning of repolarization - Within a fraction of a second - Na+ channels close - K+ open - K+ ions flow out of the cell - Passive diffusion and like charges repelling - The net charge is returning to a negative direction Repolarization - Sufficient outflow of K+ ions restored net negative charge to inside of cell - Na+ and K+ are on opposite sides of cell membranes from where they started - Sodium - sodium-potassium pump quickly moves ions back to their original sides - Resting state is resotored Nerve impulse Threshold stimulus - Stimulus is strong enough to cause complete depolarization and to generate a nerve impulse - all-or-nothing principle Nerve impulse - Electrical charges flip across cell membranes (depolarize) followed by unclipping of the electrical charge (repolarize) - The adjacent area is stimulated spreading a wave of depolarization Refractory period - Very brief period when a neuron is insensitive to additional stimuli - The cell is still depolarization /early repolarization - Absolute refractory period - during Na+ influx and early K+ outflow Relative refractory period - During the end of the repolarization period - Possible to stimulate another depolarization if the stimulus is very large Saltatory conduction - Rapid means of conducting an action potential - Depolarization in myelinated axons can only take place at the nodes of Ranvier Nervous system Chapter 9 part II How neurons communicate: the synapse Synapse: junction between two neurons or a neuron and a target cell Synaptic cleft: gap between two adjacent neurons or a neuron and a target cell Presynaptic neuron: brings depolarization wave to the synapse; releases neurotransmitter Postsynaptic neuron: contains receptors for the neurotransmitter Synaptic transmission - Perpetuation of the nerve impulse from one neuron to the next cell via vesicle - Depolarization wave cause vesicle to ump neurotransmitter into the synaptic cleft - Neurotransmitters diffuse across synaptic cleft toward the postsynaptic membrane - Receporirs on the postsynaptic membrane bind the neurotransmitter Excitatory neurotransmitters - usuallt caused of influx of Na+ so post synoptic memebrane moves toward the threshold beginning a new impulse Inhibitory neurotransmitter - Make inside of a call more negative, moving the charge within the postsynaptic cell farther away form the threshold - Can be excitatory or inhibitory - Acetylcholine - Catecholamines - Epinephrine - Dopamine Inhibitory neurotransmitters - Gamma-aminobutyric acid (GABA) - Glycine Recyling the neurotranmitter - Bodys way to stop the effects of neurotrnsmitters in order to clear the synaptic cleft - Neurotransmitters are broken down and recycled - Acetylcholine is broken down by: acetylcholinase - Catecholamines are broken down by: monoamine oxidase and catechol-O- methyltransferase Central nervous system Main component are: - Neuron cell bodies - Myleniate and unmyelinated nervev fibers - Glial cells Gray matter - Contains most of the neuron cell bodies - Thinking part of the CNS White matter - Contains most of the myleinted nerve fibers - Wiring part of the CNS Brain Cerebrum - Largest part of the brain in domestic animals - Functions associated with learning and intelligence - Surface covered with wrinkles - Gyri - folds - Separated by: fissures - deep grooves ; sulci - shallow grooves - Longitudinal fissure divides into right nd left cerebral hemispheres - Each hemisphere divided by sulci into lobes - Different lobes specialize in different functions Cerebellum - Second largest component of the brain - Located caudl to the cerebrum - Area od the brain responsible for coordinated movement, balance, posture and complex reflecxus - Damage or disease results in hypermetria Feline cerebellar hypoplasia Diencephalan - Passageway between brainstem and cerebrum - Associated structures:  - Thalumus: regulates sensory input to the cerebrum - Hypothalumus: interface between nervous and endocrine systems; temperature regulation, hunger, thirst and rage/anger - Pituitary: regulates production and release of hormones through the body Brian stem - connection between the spinal cord and rest of the brian - Many cranial nerves originate here - Components: medullar oblongata, pons and midbrain - Responsible for maintenance of basic support of the body - Heart, respiration, blood vessels diameter, swallowing, vomiting - Operates at a subconscious level Meninges - Connective tissue layers that surround the brain and the spinal cord - Supplys nutrients and oxygen and provide some cushinings - 3 layers: dura mater - tough fibrous; arachnoid- delicate, spiderweb like; pia matter = very thin; lies directly on the surface of the brainspinal cord - Meningitis: is the inflamttion of the tissue surrounding the brain an spinal cord Cerebrospinal fluid - Fluid between the layers of meninges, and in canals and cavities inside the brain and spinal cord - Provides suckings functions such as respiration and vomiting - CSF Tap provides test samples for the diagnosis of certain diseases or cancer - Meningitis, lyme, epidurals Blood-brian barrier - Separates capillaries in the brian from nervous tissue - Capillary walls in brain that have no fenestrations - Covered by cell membranes of glial cells - Prevents many drugs, proteins, ions and other molecules from readily passing from teh blood into the brain - Ecxamples: MDR-1 Spinal cord - Caudal continuation of brain stem outside the skull - Lies in bony spinal canal formed by vertebrae - Conducts sensory info and motor instructions between brain and rest of the body - Considerable processing and modification of nerve impulses takes place in the spinal cord Spinal cord - medulla - The central part of the spinal cord - Composed of grey matter - The central canal in the center filled with CSF Cortex - Outer part of the spinal cord - Composed of white matter - Surround the grey matter Dorsal and ventral nerve root - Roots emerge from each pair of adjacent vertebrae - Dorsal nerve roots contain sensory fibers- afferent  - Ventral nerve roots contain motor fibers - efferent - Neurons in grey matter process and forward nerve impulses - Dorsal horns carry SENSORY nerve impulses to the brain or other parts of the spinal cord - Ventral horns carry MOTOR nerve impulses to spinal nerves Cranial nerves - not apart of the cranial nervous system its apart of the peripheral nervous system - 12 pairs of nerves in the PNS that originate directly from the brain - Numbered in roman numerals from I through XII - Each nerve may contain - Axons of motor neurons - Axons of sensory neurons - Combinations of both We need to know this ☝️ Cranial nerve names: Old Opie Occasional Tires Trigonometry And Feels Very Gloomy, Vague, And HYPOactive Type of nerve: Some Say Money Matters, But My Brother Says Big Brains Matter Most Chapter 9 part 3 Which part of the autonomic nervous system is responsible for the flight-or-flight response? Sympathetic nervous system Autonomic nervous system - Coordination of the automatic body functions - Controls autnomatic functions at the subconscious level - Within the peripheral nervous system Sympathetic nervous system - fight or flight - Thoracolumbar system - Nerves emerge from thoracic and lumbar vertebrae Parasympthatetic - rest and digest - Craniosacral system - Nerves emerge from brain and sacral vertebral regions Autonomic nervous system: efferent nerves - Composed of sequences two neurons  - Preganglion neuron - Cell body in brain or spinal cord - Postganglionic neuron - Connected to a target organ - Ganglion - cluster of neuronal cell bodies outside the CNS Sympathetic system - Sympathetic preganglionic neurons usually synapse with many post ganglionic neuron in sympthatetic chain or ganglions outside sympathetic chain - Sympathetic post ganglionic neuron is much longer than its corresponding preganglionic neuron - Sympathetic response are usually systemic and involve several organs simultaneulsy Parasymphatetic system - Parasympatheic preganglionic neuron: travels directly from CNS to its target organ - Synapse with a short postganglionic neuron in the target organ - The parasympathetic preganglionic neuron is relatively long compared with the very short post-ganglionic neuron Sympathetic system - Fight or flight response - Helps body cope in emergency situations Parasympathetic system - Rest and restore - Brings body back to resting state - Facilitates all body processes to replace resources used during the emergency Neurotransmitters and receptors - Norepineprine - primary neurotransmitter for sympathetic nervous system - Neurotransmitter work only on cells with specific adrenergic receptors - 3 types of receptors are affected by sympathetic system - Alpha, adrenegeric receptors - vasocontrictions of skin, GI tract and kidney - Beta, adrenergic receptors - increases in heart rate an dforce of contraction - Beta, adrenoergic receptors - bronciofilation - Acetylcholine is primarily transmitter for the parasympathetic system - Cholinergic neurons release acetlychonline - 2 types of acetylchonline recpors -nicotinic and muscarinic receptors Reflexes - Rapid, autonomic response of stimuli - Designed to protect the body - Designed to maintain homeostasis 2 types: Somatic- involved with contraction of skeletal muscle Autonomic - regulates smooth muscle, cardiac muscle and endocrine glands Reflex arc - Sensory receptor detects a change - Sensory receptors sends action potential along sensory neuron to gray matter of the spinal cord or brian stem - Soneroy neurons synapse with other neurons - Incoming impulse is iegrated with impulse from other sensory neurons  - Interneurons - short neurons that connect two other neurons - Integrated response is sent out by motor neuron to target organ CNS moderation of reflexes - Upper CNS normally produces inhibitory effect on reflex arch - With injury, intact arcs caudal ro the spinal cord trauma bacomes hyperreflective - With injury where the arc eneters or leaves the spinal cord, or damage to sensory or motor nerves of the reflex arc, reflex is Hyporeflexive or absent Stretch reflex - Simple monosynaptic, two neuron reflex arc - Involves a sensory neuron and a motor neuron - Only one synapse - No interneurons Withdraw reflex - Also called flexor reflex - Several interneuron synapse - Result in contraction or flexing of muscles Crossed extenspry reflex - Contralateral reflex - Afferent sensory impulse synapse with internuerons - Crosses to the other side of the spinal cord and stimulates muscles that extend the opposite limb - Contralateral - opposite side - Ipsilateral - same side Palperbral reflex - Light tap on media canthus of eye produces a blond of eyelids Pupillary light reflex - Normal response to shining light in the eye of an animal is for the iris in both eyes to constrict