BPK 205 Chapter Notes - Chapter 11: Sliding Filament Theory, Autonomic Ganglion, Myocyte

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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
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 ]
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
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
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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]
oSympathetic: relaxes airways
oParasympathetic: constricts airways
oSympathetic: speeds up HR
oParasympathetic: slows HR
oSympathetic: bladder relaxes
oParasympathetic: bladder contracts
oSympathetic: inhibits digestion
oParasympathetic: stimulates digestion
oSympathetic: stimulates ejaculation
oParasympathetic: stimulates erection
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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.
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