A&P Midterm 2 Chapter 10: Skeletal muscles are things that produce movement, control movement, prevent movement Skeletal muscles: Most have at least 2 attachments Origin of muscle attachment (Proximal) Insertion of muscle attachment (Distal) Can attach to bone, cartilage, ligament, or fascia by tendon (aponeuroses) Architecture: Circular: controls openings (mouth, eye) Convergent: converge onto one tendon (pec major) Parallel: all run parallel to one another Unipennate: central, with fibers off one side Bipennate: central, have fibers off 2 sides (rectus femoris) Multipennate: multiple branches (deltoid) Structure informs its function Concentric contraction: Produce movement. Acts as prime mover or synergist Prime mover: muscle that has the main responsibility for producing a movement. (Knee extension: Quads, Hip extension: Glut max). Synergists: Muscles that help with other motions (helpers) (hip rotation: Glut max, Hip flexion: Quads) Stabilizers: Prevent movement. (fixator) (Scapular muscles when water skiing, Abdominal muscles to stabilize posture/core, knee muscles to stabilize joint) Eccentric contraction: Controls movement. Usually with gravity (Gravity when sitting, going down slowly in push up, weight in hand) Naming: Location: Temporalis (Temporal), brachialis (Brachii), Tibialis posterior (Tibia) Size: Maximus (large), Medius (Medium), Minimis (small) Direction: Transverse abdominus (Horizontal), Internal oblique (angle) Number or heads (origin): Biceps (2), Triceps (3), Quadriceps (4) Action: Flexor carpi radialis (Flexion, wrist, radius), Flexor carpi ulnaris (Flexion, wrist, ulna) Rules: 1. To move a joint, a muscle must cross that joint. (Must attach to 2 bones that form that joint) 2. Muscles must always pull on bone, they never push. 3. Movement produced depends on attachment location Chapter 9 Muscles are almost 50% of body mass Muscles use energy to make force Chemical energy (ATP) - > mechanical energy = Force Force = movement Muscles also maintain body position/posture, stabilize joints, and maintain body temperature. Excitability: Responsiveness to stimuli Contractility: Shorten when stimulated (Unique to muscle tissue) Extensibility: Ability to stretch Elasticity: Ability to recoil Skeletal Muscle: most attach to bone via tendon - Muscle = many muscle cells called muscle fibers - Very large: up to 30cm long, diameter 10x of normal cell - Multinucleated (unique) Myofibril: specialized organelles in muscle cells Sarcolemma = Plasma membrane Myofibril: Striated (repeated light and dark bands) - Sarcomere: small piece of myofibril - Sarcomere: made up of numerous myofilaments - Sarcomere: functional unit of cell, where contraction happens Myofilaments: - Myosin: Thick – many molecule heads that stick out on opposite sides - Actin: Thin – 2 strands of subunits in helix. - Elastic: Titin – hold myosin in place - Dystrophin: links actin to extracellular matrix T-Tubules: communication Neuromuscular junction: Where contraction starts: where nerve that activates the muscle, meets the muscle cells. Nervous systems send signal down to initiate contraction. - Signal travels down neuron (Action Potential) Comes in contact with myofibril Causes channels to open, some proteins in/out These channels allow Ca2+go in, ACH come out. ACH come out (Exocytosis), diffuse across space, binds to receptors on sarcolemma (plasma membrane) - Causes more channels to open, Na and K channels. - ACH binds and changes receptor. Allows Na in/out. - More sodium in than K out - This makes action potential in Sarcolemma (graded potential) Excitation-contraction coupling - New action potential moves along sarcolemma - Goes down T-tubules - Makes Ca2+ open again inside in sarcoplasmic reticulum - Ca2+ comes out goes to myofilaments - Binds to actin (thin), lets myosin head bind to actin (activates it by Ca2+) Cross bridge cycle - NEEDS ATP - Where force comes from - Myosin is bound to actin - Myosin head pulls actin with it - Then it releases, and cycles as long as ATP is available and stimulus is there. Motor unit: alpha motor neuron (nerve cell) and all the muscle fibers it goes through (innervates) - What the action potential travels down - All or none action Muscles for fine movement: small motor units (Eye) Muscles for gross movement: larger motor units (Butt) Muscle Twitch Force: - If ONE action potential goes to muscle, result is twitch force Increase frequency of stimulation: send more frequent action potentials Increase number of Motor units: increase frequency may not be enough, instead needs more motor units. Motor units are used from smallest to largest. They build upon each other; - engage muscle motor unit, max out frequency, needs more - more motor units, max out frequency, needs more - more motor units, max out frequency needs more, etc. - until needs are met - If body cant meet that need, cant do task. Nervous systems needs way to grade (judge) how much force body needs to complete task: - increase frequency - increase # of motor units Muscle Tone: constant, slightly contracted state of muscles - When awake/conscious - Keeps muscles firm, healthy, and ready to respond. Flaccid: low muscle tone (Spinal cord injury) Spastic: Tone is increased (Brain injury, stroke) Factors that influence force production: - Rate of stimulation (frequency) - Number of motor units - Size muscle/fiber - Length of muscle (if muscle is very short, or very long: ability to produce force is decreased) When muscle is stimulated it is NOT all or none Muscle Contraction: Isometric: No change in muscle length (Static; carrying something) producing force, but not moving - Myosin head does not move the thin (actin) filament. Isotonic: muscle changes length, get longer or shorter. - Can be concentric (shorter). Produces movement - Can be eccentric (longer). Controls movement - Force is produced in same way for both isometric and isotonic Muscles require energy (ATP): - To move and detach cross bridges - Operate the NA-K+ pump - Operate Ca2+ pump in SR Only enough ATP stored for 4-6 seconds. 3 ways to regenerate ATP: - Direct phosphorylation - Anaerobic glycolysis - Aerobic respiration Length of exercise determines how ATP is made: - First 6 seconds: stored ATP - Next 10 seconds: Direct phosphorylation Next 30-40 seconds: Anaerobic glycolysis Remainder: Aerobic Respiration ATP Production Direct Phosphorylation Anaerobic Glycolysis No Oxygen No oxygen 1 ATP made 2 ATP 15 seconds 30-40 seconds - Brief burst of energy for short period, use one of first 2 methods Aerobic Respiration Needs Oxygen 32 ATP Hours Aerobic/Endurance exercise: long time - Change in physiology and structure - Greater endurance, greater strength, and greater resistance to fatigue Endurance: length of time of muscle contraction before its fatigued Resistance exercise: weightlifting - Progressive (build up strength) - Typically anaerobic - Muscle hypertrophy (growth): from increase in muscle fibers (myofibrils) - Increase in myofilaments, glycogen stores, and connective tissue - Increased muscle strength and size # of muscle fibers stays the same, but number of myofilaments can increase - Muscles cells DO NOT undergo mitosis – why they don’t increase in # Ageing: Muscles weakness occurs as we age - Sarcopenia: age related muscle loss. Issues with mobility, fall risk, loss of independence - Losses in strength quickened when immobile (hospitalization, disability, injury) – PJ paralysis - Muscle loss is NOT permanent. Can be reversed through resistance training o Be progressive resistive exercises o 3 x a week Smooth muscle - In hollow organs (stomach, bladder, airways) - NO voluntary control - Usually arranged in sheets - Has 2 layers: longitudinal, circular o Longitudinal: parallel to long way of organ. Contraction = shortens o Circular: on circumference of organ. Contraction = constricts - Contraction of 2 layers leads to rhythmic contraction: Peristalsis - Single unit: has gross control (moves as a unit) - Stomach - Multi-unit: has independent control (fine movement) – Pupil size, erector pili muscles (hair follicles) - Stress-relaxation response: move substances along by temporary contraction – adjusts to ‘new normal’ o Can contract ‘on demand’ - Length/tension change: when at half-2x resting length. - o functions well when empty – bladder, stomach o Skeletal muscle only when at optimal resting length Hyperplasia: Smooth muscle cells can divide and increase numbers (Uterus during puberty) Smooth One nucleus Very small No striations or sarcomeres Has actin and mysoin No T-Tubules No neuromuscular junction Has varicosities Skeletal Multinucleated 10 x wider 1000’s x longer Striated Has sarcomeres, Myosin and Actin Has T-Tubules Has neuromuscular junction Smooth Force by sliding filaments Calcium triggers contraction ATP required Stimulation causes excitation and inhibition Very slow contraction, uses less ATP Skeletal Force by sliding filaments Calcium triggers contraction ATP required Stimulation causes excitation Contract 30 x faster, uses high ATP amounts Chapter 11 Functions of Nervous system: - Sensory input: Taking information in (red light) - Integration: Interpretation of what that means (I should stop) - Motor output: Doing action (Stopping) PMS MAS APS PMAS PMASP Sensory part: take info in Motor part: puts info out Nervous system tissues: Neuroglial (Glial cells): Provide support. The ‘jelly’ of the cake. The supportive structure - 6 different types of glial cells o Schwann cells (PNS) o Oligodendrocytes (CNS) – form myelin sheath - Glial cells in PNS can regenerate – cut cell, will grow back o In CNS, will inhibit (Spinal cord/brain do not fix itself) - Way more glial cells than neurons Neurons: are excitable and can conduct information - How Nervous system communicates - Long lifespan - Amitotic (cant divide) - High metabolic rate (needs oxygen continuously) – why we do CPR Dendrites: little arms off cell body, interact with rest of environment. They receive input information Axon hillock: Important for action potentials Axon: where information exits neuron. Length varies by location. Can have 1000’s of axon terminals Myelin sheath: makes axon an effective transmitter Information can go to a cell or gland, or another neuron In CNS: bundles of axons are called tracts In PNS: bundles of axons are called nerves 3 types of neurons: - Sensory: carry sensory information from peripheral to brain(Going in) - Motor: carry information from brain to muscles, glands (Going out) - Interneurons: 99% of all neurons. Neurons that connect neurons. Action Potentials: - How nervous systems send messages over long distances - Muscles also make and use AP to contract - Happens when ions cross cell membranes - Made in axons (axon hillock) and travel to axon terminals - ALL OR NONE – once made, will continue until axon terminal 1. Cell is waiting, neutral 2. Stimulus. Membrane potential changes to less negative. 3. Continues to rise, passes threshold. Makes voltage gated channels open (NA Fast, K Slow) this makes it depolarized as NA rusehs into cell, making it more +, K ruses out of cell, making more – 4. Hyperpolarization: more polarized because K goes out 5. K channel open for longer, goes below normal (more -). Evens out through sodium Potassium pump - Voltage gated channels only open when it reaches certain voltage For AP its -55mV Resting potential is -70 Peak is +30 Depolarization – Na IN Hyperpolarization – K OUT If no voltage gated channels, no action potential - No AP at dendrites AP Propagation: - Acts as stimulus for next section - Voltage in one spot, activates, next, which activates next, etc. Unmyelinated neurons – slow (2m/s) Myelinated neurons – fast (100 m/s) - Multiple sclerosis., affects myelin on neurons, not efficient at transmission AP’s don’t flow back because of Hyperpolarization – refractory period Synapses: connection that allows AP to transmit - Can happen between 2 neurons - Can happen between neuron and effector cell (Muscle cell) - Most are chemical – by neurotransmitters - Enables transmission across synaptic cleft Chemical Synaptic transmission - AP arrives at terminal of neuron - Causes voltage gated channels Ca2+ channel to open. - Ca2+ rushes into axon terminal - Makes neurotransmitter leave by exocytosis - Neurotransmitter diffuses across space, specific receptors bind to NT, opens ion channels - Flow of NA and K - AP happens (Most of time) Neurotransmitters: - Language of the nervous system – enable neurons to talk to each other and body - Anything that interferes with NT function can impair nervous system function - Can be excitatory (depolarization) or inhibitory (Hyperpolarization) - Can act directly (bind to receptors to make ion channels open) - Can act indirectly (by second messenger molecules) - Two types: o Channel linked receptors – located right next to site of neurotransmitter release (closed ion, and open ion channel) o G protein coupled receptors – not as immediate. - 50 types of Neurotransmitters - A lot of drugs affect NT (therapeutic and illicit) - Ach first NT and most understood - Acts at neuromuscular junction Chapter 12 Central Nervous System: - Brain - Spinal cord Brain: - Central hemisphere, diencephalon, cerebellum, midbrain, pons, medulla oblongata Grey matter: - Neuron cell bodies White matter - Generally myelinated axons. Fiber tracts in the CNS Ventricles: - Lateral, third, and fourth. - Makes the cerebrospinal fluid – key function - Aperatures connect ventricles to subarachnoid space Cerebral hemispheres - Right/left hemispheres, separated by longitudinal fissure - Gyri: raised area - Sulci: shallow grooves - These increase surface area. Bigger surface area = more cell bodies - Head needs to be small for balance. Lobes: - Frontal, occipital, parietal, temporal, insula Major sulci: - Central, divides from front and back. (frontal and parietal) - Lateral sulcus, divides, side near ears (temporal from frontal and parietal) 3 regions of Hemisphere - Cerebral cortex (grey matter), white matter, basal ganglia Cerebral Cortex: - Conscious mind - Think, feel, remember, communicate, initiate movement - 40% of mass of brain - Sulci/gyri triples surface area - Contralateral: side of brain controls opposite side of body - Lateralization: each side is specialized (though both contribute to most functions) - Has 3 functional areas: o Motor o Sensory o Association (Integration) Motor areas: generally in front of central sulcus - Primary: conscious control - Premotor: movement planning takes place here, movement not instantaneous - Broca’s area: controls muscles for speech Homunculus: shows size of brain that is devoted to that area of body Sensory areas: generally behind central sulcus - Primary somatosensory cortex: impulses from general sensory receptors in the skin and from proprioceptors arrive here - Auditory area: impulses from inner ear are projected here where they are ‘heard’ and interpreted - Wernicke’s area: understanding written and spoken language - Visual area: sensation and interpretation of what our eyes ‘see’ - Olfactory area: impulses from receptors in nasal cavity Vestibular cortex: keeps us upright (equilibrium) Gustatory cortex: taste Visceral sensory area: conscious perception of visceral sensation (upset GI) Association areas: (Integration) - Multimodal – all the pink of brain in picture - Gives meaning to information we receive - Sends output to multiple areas White Matter - Responsible for communication between areas of the cerebrum and between cerebral cortex and lower CNS - Has myelinated fibers in tracts o Association: connect different parts of same hemisphere o Projection: connect cortex to rest of nervous system o Commissural: connect 2 hemispheres (corpus collosum) Basal Ganglia: - Group of 3 nuclei, deep in white matter o Caudate, putamen, globus pallidus - Receive input from cortex and provide output to motor cortex - Have extensive connection to one another - Critical for production of voluntary movement, initiating movement, and involuntary movement - Parkinson’s and Huntington’s – lesions in area - Learning : rewards or avoidance of punishment - Habit formation Diencephalon: Thalamus, hypothalamus, epithalamus - It encloses the 3rd ventricle Thalamus: directs what way to go – director - Relay station - All sensory information entering the cortex passes through here - Funnels important information to the appropriate parts of cortex - Regulation of learning, memory, motor activities Hypothalamus - Main visceral control center - Autonomic nervous system - Initiates physical response to emotions (heart racing – scared) - Regulates body temperature, food intake, water balance and thirst, sleep wake cycle - Controls endocrine system - Damage to area: Emotional imbalances, obesity, sleep issues Epithalamus - Pineal gland: Secretes hormone melatonin - Helps with sleep-wake cycle Brain stem: Midbrain, Pons, Medulla Oblongata - 2.5% of brain - Necessary functions: breathing, heartrate - Anything going to rest of body HAS to pass through here - Has 10/12 cranial nerves Medulla Oblongata: spinal cord injury here would impact breathing – close proximity to brainstem - Cardiovascular centre, respiratory centre, vomiting hiccups, coughing, sneezing, Pons: means bridge - Mainly has conduction fibers - goes between higher brain and spinal cord - Also helps brining information between cerebellum and motor cortex Cerebellum: little brain - Outer cortex with many convolutions on surface (similar to gyri and sulci) – very large surface area - Only 10% of brain volume, but 50% of brain neurons - Not part of conscious brain - Timing and coordination of movement – could not pronate/supinate - Cannot initiate movement - Easily disrupted by alcohol - It acts as a comparator, compares actions that happen to what should have happened and corrects it. - Cerebellum injury: o Has difficulty carrying out rapidly changing motions o Difficulty estimating distances – walking over spaces - People with cerebellar issues often times people think they are drunk Functional brain system: limbic system and reticular formation - Network of neurons that are wide-spread among brain Limbic system: on medial aspect of cerebral hemispheres - Emotional-visceral brain - Emotional centre - Motivation and survival – to eat, have sex - Memory storge - Regulation – our behaviors - Functions that are essential to quality of life Reticular formation - 3 broad columns of neurons that go along brain stem - Have connections to hypothalamus, thalamus, cerebral cortex, cerebellum, and spinal cord (Basically everywhere) - Broad connections: controls arousal as a whole - Has reticular activating system (RAS) RAS - Continuously sends signals to cortex to keep it alert/active - Sever injury would result in irreversible coma - Filters out unimportant sensory information (background info) - LSD interferes with this filter - Involved in control of movement Brain protected by Skull, Meninges, Cerebrospinal fluid, blood brain barrier Meninges: Dura, arachnoid, pia – maintains brain shape - Subdural – between dura and arachnoid - Subarachnoid – between arachnoid and pia – usually damage to blood vessels - Meningitis: inflammation of meningitis - Encephalitis: inflammation of brain tissue Cerebrospinal fluid: Surrounds brain and spinal cord - Brain is floating in CSF – reduces weight by 97% - Produced by choroid plexus, hangs from roof of each ventricle - In subarachnoid space, so always bathing the brain - Main function top cushion the brain, also helps nourish - Replaced every 8 hours All protect from trauma from outside Blood-brain barrier: - protects the brain from substances already in the body - Neurons are sensitive to surrounding environment, kept very stable - Prevents any unwanted molecules from entering the brain - Tight junctions in endothelial cells: key structures of blood brain barriers - Only lipid soluble can enter – medication Spinal cord: part of CNS - CSF - Spinal nerves, has 31 pairs - Spinal cord end around T12. - Cauda equina: long nerve roots from higher up go from there down spinal column. Vertebral column grows faster than spinal cord. o Why lumbar punctures go here, no risk of puncturing spinal cord Meninges: same as brain: dura, arachnoid, and pia Spinal cord has butterfly shape for grey matter - Dorsal (posterior) horn o Neurons (interneurons) from periphery up to brain – sensory info o PS – posterior, sensory - Ventral (anterior) horn o Motor neurons out to periphery from brain o ALS, Polio, only affect anterior/motor - Dorsal root and ventral root come together/split to form the spinal nerve root Multi neuronal pathways: bring info from brain to periphery - Decussation: most pathways cross from one side to the other; right side controls left etc. - Relay: most pathways consist of a group of 2/3 neurons that convey info from one region to another - Somatophy: fibers are arranged in orderly fashion, mapping out body – could use symptoms to identify where injury is on spinal cord - Symmetry: all pathways and tracts are paired Ascending tracts: Sensory - Most cross over, some in spinal cord, some in medulla o Spinothalamic: from spinal cord to thalamus: info about temperature, pain, coarse touch, pressure o Spinocerebellar: from spinal cord to cerebellum: info about muscle tendon stretch (coordinating movement) o Medial Lemniscus: dorsal column: vibration, discriminatory touch, proprioception Descending tracts: motor - All cross over, some in spinal cord, some in medulla - All involve interneurons - All end on skeletal muscles o Pyramidal tract: direct pathway from cortex to spinal cord o Indirect patthways: more complex. more connections and synapses. Posture and balance, very coarse limb movements, head, neck, and eye related to seeing (following someone)
