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BPK 205 (11)
Chapter 11

Ch. 11 Study Questions

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Simon Fraser University
Biomedical Physio & Kines
BPK 205
Parveen Bawa

Chapter 11 1. What is the difference between the somatic and the autonomic output neurons? Provide all details. [ 2-3 pages, at least one figure] Somatic Output Neurons: • Are called motoneurons • Motoneurons located in Ventral horn of the spinal cord • No cell bodies outside CNS • Target is skeletal muscle • Always excitatory • Posture and Movement Autonomic Output Neurons: • Target is heart, smooth muscle, or gland • Cells which innervate the target cells lie outside the CNS in a ganglion. Called POST-GANGLIONIC CELLS • Pre-ganglionic cells lie in lateral horn of spinal cord (but exits via ventral horn), or brain stem • Pre-ganglionic axons are myelinated, post-ganglionic axons are unmyelinated • These neuron pathways are divided into sympathetic and parasympathetic ANS • Excitatory or inhibitory • Controls metabolism, visceral fxn, secretion 2. What are the differences between the sympathetic and the parasympathetic nervous systems? [1-2 pages, at least one figure ] Sympathetic: • Short pre-ganglionic axon. Long Post ganglionic axon • Pre-ganglionic neurons lie in thoracic and lumbar regions of spinal cord • Autonomic ganglion uses neurotransmitter: norepinephrine to bind to adrenergenic receptors of target tissue • Post-ganglionic cells increase HR, vasoconstriction, sweating, inhibition of paristaltic movements. Diverts blood to skin and muscles Parasympathetic: • Long pre-ganglionic axon. Short post ganglionic axon • Pre-ganglionic neurons lie in Sacral region of spine and brain stem • Autonomic ganglion uses neurotransmitter: ACh to bind to muscarinic receptors of target tissue. The ACh activates G-protein which opens K+ channels which hyperpolarizes the membrane • Slows HR, increases motility of GI tract. Diverts blood to internal organs 3. Give examples of neurons whose cell bodies lie outside the CNS. [3-4 lines] • Post-ganglionic sympathetic autonomic neurons • Post-ganglionic parasympathetic autonomic neurons 4. Give names of structures which contain nicotinic ACh synapses outside the CNS. [you know two] • Post-ganglions of the Sympathetic and Parasympathetic autonomic systems • Synapses that connect motoneurons to skeletal muscle 5. Give 5 examples of organs which have both sympathetic and parasympathetic innervations. What are the effects of each type of innervation in these organs? [try this question on your own from the big complex figure. [half a page] Lungs: o Sympathetic: relaxes airways o Parasympathetic: constricts airways Heart: o Sympathetic: speeds up HR o Parasympathetic: slows HR Bladder: o Sympathetic: bladder relaxes o Parasympathetic: bladder contracts Stomach: o Sympathetic: inhibits digestion o Parasympathetic: stimulates digestion Penis: o Sympathetic: stimulates ejaculation o Parasympathetic: stimulates erection Chapter 12. 1.Starting from a whole muscle, describe the structure of a muscle using the terms muscle fibre, myofibril, sarcomere, thick and thin filaments. Where does the nucleus of a muscle fibre lie? [~ 2 pages of writing plus figures] Sacromeres: contractile units containing thin actin filament, and thick myosin filament. Myofibril: bundles of sacromeres. Surrounded by sacroplasmic recticulum and T-tubules Muscle fibre: bundles of myofibril Muscle Fascicle: Bundled up bunches of muscle fibre Bundles of Muscle Fascicle form the muscle body itself. Connective tissue wraps the muscle fascicles. Nucleus of a muscle fibre lies on the sacrolemma (membrane of the muscle fibre) 2. When one action potential is produced at the end plate region of the muscle fibre, describe how this action potential results in the twitch contraction of that single muscle fibre. Use the sliding filament theory of muscle contraction to describe contraction. [3-4 pages plus figures] {Hints: AP at the end plate region spreads along the sarcolemma, T- tubule, DHP receptor, Ryanodine receptor, Ca++ release, steps leading to contraction according to Huxley�s sliding filament theory, sliding of all thin filaments along thick filaments, pull on the tendon giving rise to force. Ca++ pumped back, relaxation occurs. • Action potential travels along sacrolemma (membrane of muscle fibre) until it reaches a T-tubule. • In the T-tubule, the action potential reaches a Dihydropyridine receptor, depolarizing it. • This causes a conformational change that opens the Rynodine receptor in order to release Ca++ from Sacroplasmic reticulum into the cytoplasm of the muscle fiber cell. • A relatively slow ATP pump pumps Ca++ back into the Sacroplasmic Reticulum immediately following the release into the cytoplasm. • Ca++ binds to Troponin C. This moves Tropomyosin out of the way of myosin binding sites. • Myosin head binds to myosin binding site in the actin. o Start in the rigor state, where actin and myosin head are bound together and cannot release without ATP o ATP binds to ATP binding site of the myosin. Myosin is released from actin o Myosin ATPase hydrolyses the ATP into ADP and Pi. ADP and Pi remain attached to myosin. o Myosin head changes configuration and attaches weakly to a new actin molecule. Configuration is at a 90 degree angle. o Pi is released providing energy for the power stroke. Myosin head returns to original configuration while attached to actin. Actin is moved and force is created. o ADP released, and it returns to rigor state. 3. Define twitch of a muscle fibre.[one sentence] When Ca ++ in the cytoplasm binds to troponin and results in a biphasic mechanical response of the muscle fibre. It is the mechanical response of a muscle fibre to a single action potential 4. Draw and describe, in detail, the release of Ca++ from the SR once an action potential depolarizes the terminal bouton of the motoneuron. [1-2 pages plus figures] Once Ca++ is released, where is ATP used before the muscle relaxes? [two actions] • Ca++ channels are opened in the terminal bouton of the motoneuron. This triggers release of synaptic vesicle contents. • The synaptic vesicles travel to docking proteins where they attach. This complex opens forming a channel that allows ACh from the synaptic vesicles to travel across the synapse and two bind onto one ACh receptor of the post-synaptic muscle cell. This opens a channel that allows Na+ and K+ to flow through. More Na+ flows in than K+ flows out, so a depolarization called End Plate Potential is produced. (~70mV depolarization) • EPP graded potential travels in both directions outwards, and is enough to open voltage gated Na+ channels that start action potentials that travel in both directions. • This action potential reaches a T-tubule where a Dihydropyridine receptor is depolarized. The DHP receptor mechanically changes to open the Rynodine receptor channel of the Sacroplasmic Reticulum. This allows Ca++ to into the
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