BIOS 252 A&P 2 MIDTERM STUDY GUIDE

A&P 2 Midterm Study Guide Ch. 10 Characteristics of smooth and cardiac muscle tissue • Cardiac Muscle o Involuntary, intrinsically controlled, striated, branched, and single nucleated. • Smooth Muscle (Visceral) o Involuntary, not striated, not branched, and singly nucleated. Functions of the 3 types of muscle tissue • Skeletal Muscle o Moves bones and other structures • Smooth Muscle o Contractions and relaxation of the autonomic nervous system, and walls of organs • Cardiac Muscle o Pump blood Characteristics of skeletal muscle: excitability, elasticity • Voluntary, striated, not branched, and multinucleated • Excitability: ability to respond to a stimulus, delivered from a motor neuron or a hormone. • Elasticity: ability to return to its original length & shape after contraction or extension. Components of a skeletal muscle cell • Myofibrils: cylindrical structures that extend along the complete length of the cell. Twitch contraction • Brief contraction of all muscle fibers in a motor unit in response to a single action potential in its motor neuron. Layers of connective tissue holding skeletal muscle organs together (3 types) • Epimysium: outer layer, dense irregular connective tissue, surrounds muscle organs • Perimysium: middle layer, dense irregular connective tissue, contains nerves and vasculature; surrounds muscle fascicles. • Endomysium: interior layer, loose/elastic connective tissue, contains capillaries, nerves and stem cells, surround muscle fibers. Parts of the sarcomere • Z Discs: narrow, plate-shaped regions of dense material that separate one sarcomere from the next. • A Band: dark, middle part of sarcomere that extends entire length of thick filaments and includes those parts of thin filaments that overlap thick filaments. • I Band: lighter, less dense area of sarcomere that contains remainder of thin filaments but no thick filaments. A Z-disc passes through center of each I-Band. • H Zone: narrow region in center of each A Band that contains thick filaments but no thin filaments • M Line: region in center of H zone that contains proteins that hold thick filaments together at center of sarcomere. SR function • Store calcium ions (Ca2+) T tubule function • conduct the signal to contract throughout the entire fiber, are part of sarcolemma. Acetylcholine • ACh – neurotransmitter released at the Neuromuscular Junction. Functions in memory, waking up, attention and learning. The sliding mechanism theory • Myosin pulls on actin, causing thin filament to slide inward • Consequently, Z discs move toward each other and the sarcomere shortens • Whole muscle shortens > transfers force to tendon > movement Role of ATP in muscle contraction • ATP binds to myosin, moving myosin to its high-energy state, releasing the myosin head from the actin active site. • ATP can then attach to myosin, which allows the cross-bridge cycle to start again, hence muscle contraction can occur. The steps of muscle contraction (start at NMJ, ending with sarcomere shortening) • Action potential in a motor neuron triggers the release of Ca2+ ions from the sarcoplasmic reticulum • Calcium ions bind to troponin (on actin) and cause tropomyosin to move, exposing binding sites for the myosin heads • The actin filaments and myosin heads form a cross-bridge that is broken by ATP • ATP hydrolysis causes the myosin heads to swivel and change orientation • Swiveled myosin heads bind to the actin filament before returning to their original conformation (releasing ADP + Pi) • The repositioning of the myosin heads move the actin filaments towards the center of the sarcomere • The sliding of actin along myosin therefore shortens the sarcomere, causing muscle contraction Myosin and actin functions • Myosin : thick filament • Actin : thin filament • Interactions of actin and myosin are responsible not only for muscle contraction but also for a variety of movements of non-muscle cells, including cell division Resting Membrane Potential • About -70mV, this means that the inside of the neuron is 70 mV less than the outside. Ch. 11 Fulcrum, effort and load – how muscles function with bones and joints • Bones serve as levers • Joints serve as fulcrums • Lever is activated on by resistance and effort • Example : movement of the forearm lifting a weight. E is contraction of biceps brachii, F is elbow joint, L is weight of object plus forearm 3 types of lever systems • First Class Lever : EFL – fulcrum is between effort and load; think of adult and child on seesaw. Ex: head resting on the vertebral column • Second Class Lever : ELF – load is between fulcrum and effort; produces most force, like wheelbarrow. Uncommon in body, example is standing up on toes. • Third Class Lever : FEL – effort is between fulcrum and load; operate like pair of forceps, most common in body; example is the elbow joint, biceps brachii muscle, and bones of the arm and forearm, flexing. Origin and insertion • Origin : attachment of stationary bone • Insertion : attachment to the moveable bone Muscle movements: flexion, extension, circumduction, rotation, adduction, abduction, etc. • Flexion : decreasing angle btwn two bones, aka bending a body part • Extension : increasing the angle btwn two bones, aka straightening a body part • Circumduction : moving body part away from the midline • Rotation : turning a body part around on its own axis, ex. Head side to side • Adduction : moving body part toward the midline • Abduction : moving body part away from midline Isometric vs Isotonic contractions • Isometric : generate force without changing the length of muscle • Isotonic : generate force by changing the length of the muscle Agonist vs antagonist • Agonist : (prime mover) leader in an opposing muscle pair, it contracts to cause an action (biceps brachii) • Antagonist : stretches and yields to the effects of the agonist (triceps brachii) Muscles of inhalation • Diaphragm, external intercostals, pectoralis major, pectoralis minor, sternocleidomastoid, scalenes, serratus anterior, serratus posterior superior, latissimus dorsi. Biceps brachii: know all actions • Flexes elbow • Flexes and abducts shoulder • Supinates radioulnar joint in the forearm Names and actions of muscle on the “Muscle Objective List” • See separate list Ch. 12 Parts of a typical neuron • Cell body : soma/perikaryon • Dendrites (spikes connected to body) : receive signals from other cells • Axon (long tail) : propagates nerve impulses to another cell Parts of CNS • Brain • Spinal cord Parts of PNS • Cranial nerves • Spinal nerves • Ganglia • Enteric plexuses in small intestine • Sensory receptors in skin Afferent / efferent pathways • Afferent : signals come from outside stimuli and tell your brain what they are sensing • Efferent : carry signals away from CNS, signals that your brain sends to tell your body to do something. Neuroglia types and functions • Satellite Cells (PNS) – surround neuron cell bodies in ganglia; regulate O2, CO2, nutrient and neurotransmitter levels around neurons in ganglia. • Schwann Cells (PNS) – surround axons in PNS; responsible for myelination of peripheral axons; participate in repair process after injury. • Oligodendrocytes (CNS) – myelinated CNS axons; provide structural framework • Astrocytes (CNS) – maintain blood-brain barrier; provide structural support; regulate ion, nutrient, and dissolved gas concentrations; absorb and recycle neurotransmitters; form scar tissue after injury • Microglia (CNS) – remove cell debris, wastes, and pathogens by phagocytosis • Ependymal cells (CNS) – line ventricles (brain) and central canal (spinal cord); assist in producing, circulating, and monitoring of cerebrospinal fluid. Chemical and electrical synapses • Chemical synapses – one-way transfer of information from a presynaptic neuron to a postsynaptic neuron • Electrical synapse – gap junctions connect cells and allow the transfer of information to synchronize the activity of a group of cells EPSP vs IPSP • Excitatory postsynaptic potentials – depolarizing postsynaptic potential (opens Na+ channel) • Inhibitory postsynaptic potentials – hyperpolarizing postsynaptic potential (opens K+ or Cl- channel) Excitatory neurotransmitters function and one example • Increase the likelihood that the neuron will fire an action potential • Examples : epinephrine and norepinephrine Inhibitory neurotransmitter function and one example • Decrease the likelihood that the neuron will fire an action potential • Examples : serotonin and gamma-aminobutyric acid (GABA) Ligand-gated channels • transmembrane ion channels that open or close in response to the binding of a chemical messenger like a ligand. • Found in electrically excitable cells like neurons. Voltage-gated channels • Opens in response to a change in membrane potential. • Participate in the generation and conduction of action potentials in the axons of all types of neurons. Electrically excitable cell types • Are used for transmitting signals between different parts of a cell. Signals are generated by opening or closing of ion channels at one point in the membrane, producing a local change in the membrane potential. • Neurons and muscle cells. Depolarization, hyperpolarization, repolarization • Depolarization (less -) • Hyperpolarization (more -) • Repolarization (return to -70) The steps required for a muscle contraction to occur starting with events at the NMJ and ending with the cross-bridge formation cycle • Neuron action potential arrives at end of motor neuron • ACh is released • ACh binds to receptors on motor end plate • Permeability of sarcolemma changes (Na rushes in)(an action potential is produced) • Muscle action potential sweeps into the T Tubules triggering Ch. 13 • Release of Ca from the cisternae of the sarcoplasmic reticulum • Ca binds to troponin • Troponin changes shape and shifts tropomyosin to expose binding sites of actin • Myosin binds to actin (cross bridge is formed)(ADP released from myosin) • Myosin head pivots (pulling actin) • Myosin releases from actin (cross bridge is broken)(another ATP binds to myosin) • Myosin re-extends into “ready” position (ATP>ADP+Pi)(ADP is bound to myosin) Functions of posterior, lateral and anterior horns of gray matter • Posterior: receive sensory information that enters the spinal cord via the dorsal roots of the spinal nerves. • Lateral: present primarily in the thoracic region and contain the preganglionic visceral motor neurons that project to the sympathetic ganglia. • Ventral: contain cell bodies of motor neurons that send axons via the central roots of the spinal nerves to terminate on striated muscle. Tracts in the spinal cord and specific examples • Highways of information up and down spinal cord. • Ex: Spinothalamic: carries sensory info (pain, temp, itch, pressure) from spinal cord to thalamus for processing. • Ex: Lateral Corticospinal: carries info from cerebral cortex to spinal cord, eventually causing voluntary muscle movement through action of motor neurons in spinal nerves Parts of a reflex arc • Sensory receptor: responds to a stimulus by producing a generator or receptor potential • Sensory neuron: axon conducts impulses from receptor to integrating center • Integrating center: one or more regions within CNS that relay impulses from sensory to motor neurons • Motor neuron: axon conducts impulses from integrating center to effector • Effector: muscle or gland that responds to motor impulses Reflex arcs (spinal withdrawal, crossed extensor reflex) • Spinal Withdrawal (flexor reflex) – causes withdrawal of a part of the body in response to a painful stimulus. • Crossed Extensor Reflex – causes contraction of muscles that extend joints in the limb opposite a painful stimulus. • Tendon Reflex – causes relaxation of the muscle attached to the stimulated tendon organ • Stretch Reflex – causes contraction of a muscle that has been stretched. Anatomical organization of the spinal cord • Four regions: cervical, thoracic, lumbar, and sacral • 31 pairs of spinal nerves • C1-C8 ; T1-T12 ; L1-L5 ; S1-S5 ; Co1 • Cord has three meninges; dura is tough outer sheath, the arachnoid lies beneath it, and the pia closely adheres to the surface of the cord. Lumbar enlargement • Widened area of the spinal cord that gives attachment to the nerves which supply the lower limbs. It commences about the level of T11 and ends at S2, and reaches its maximum circumference, of about 33mm. Nerves that supply the muscles of the thigh/leg • Femoral nerve : anterior portion of the thigh/leg • Sciatic nerve : posterior portion of the thigh/leg • Obturator nerve : medial component of the thigh/leg