Quiz #3 Flashcards by Jess Black

What is the role of the somatic nervous system?

control skeletal muscles

voluntary

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What is the role of the autonomic nervous system?

control smooth and cardiac muscle

involuntary

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What are the divisions of the autonomic nervous system?

sympathetic
- fight of flight

parasympathetic
- rest and digest

both innervate most effector organs in antagonistic ways

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Describe autonomic neuron pathways.

2 neurons in series
1 preganglionic neuron can synapse with 8-9 postganglionic neurons at autonomic ganglion, each innervate a different target

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What is a ganglia?

cluster of synapses

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How do sympathetic and parasympathetic neurons differ?

sympathetic

originate in thoracic and lumbar spinal cord, run down vertebrae
preganglionic neuron is shorter (ganglia close to spinal cord)

parasympathetic

most originate in brain stem and leave as cranial nerves, some originate near the sacral end of spinal cord
75% originate from vagus nerve
preganglionic neuron is longer (ganglia close to target tissues)

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Describe the chemicals used in autonomic chemical signalling.

PNS

preganglionic neurons: ACh on nicotinic cholinergic
postganglionic neurons: ACh on muscarinic cholinergic

SNS

preganglionic neurons: ACh on nicotinic cholinergic
postganglionic neurons: NE on adrenergic

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What are the types of adrenergic receptors?

alpha and beta

alpha and beta 1 are excitatory, alpha and beta 2 are inhibitory, beta 3 stimulates fat cell lipolysis

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What are varicosities?

the neuroeffector junction between postganglionic autonomic neuron and target cell

swollen areas at distal ends of axons
contain vesicles full of NT, released identical to typical synapse

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What is the adrenal medulla?

specialized neuroendocrine tissue associated with SNS

sits ontop of kidney

secretes epinephrine into blood and target tissue

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Where are some places that dual innervation does not occur (no PNS)?

adrenal medulla
sweat glands
most blood vessels

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How many neurons innervate a single muscle fiber? How many muscle fibers can a single neuron innervate?

muscle fiber innervated by 1 neuron

neuron can innervated multiple muscle fibers

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What are the components of somatic neuromuscular junctions?

axon terminals
motor end plates
- on muscle membrane
- folds with many nicotinic receptors
Schwann cell sheaths

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Describe skeletal muscle.

large, multinucleated cells
appears striated
can shorten/contract to produce skeletal movement/maintain posture

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Describe they layers of the skeletal muscle.

epimysium

exterior collagen layer
connected to deep fascia
separate muscle from surrounding tissue

perimysium

surrounds muscle fiber bundles (fascicles)
contain blood vessel and nerve supply for fascicles

endomysium

surrounds individual muscle fibers
contains blood vessel and nerve supply that contact muscle cells

all come together at ends of muscle to form a tendon (bundle) or an aponeurosis (sheet)

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What is the sarcolemma?

cell membrane specific to muscle

surrounds sarcoplasm, the cytoplasm of the muscle

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What are T-tubules?

run perpendicular to cell organization, penetrating myofibrils

transmit AP through cell so entire fiber can contract simultaneously

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What are myofibrils?

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organization of protein filaments

- thick and thin

What are myofilaments?

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individual thick (myosin) and thin (actin) filaments

responsible for muscle contraction

What is the sarcoplasmic reticulum?

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membranous structure surrounding each myofibril

main source of calcium

form terminal cisternae

What are terminal cisternae?

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regions with higher concentration of calcium

attached to T-tubules

release calcium into sarcomere to begin muscle contraction

What is a triad?

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1 T-tubule and 2 terminal cisternae

What gives muscle its striated appearance?

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parallel organization of myofibrils

What are sarcomeres?

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contractile unit of muscle

Z line to Z line

List the structural components of a sarcomere.

``` A band H zone M line I band Z line ```

What is the A band?

- dark band | - full length of thick filament

What is the H zone?

- thick filaments | - no overlap

What is the M line?

- links thick filaments in the centre of the sarcomere

What is the I band?

- light band - thin filaments - no overlap

What is the Z line?

- links thin filaments

What is actin?

thin, contractile protein | holds myosin binding site

What is tropomyosin?

regulatory protein that overlaps myosin binding sites on actin

What is troponin?

regulatory protein that attaches to actin, tropomyosin, and calcium (reversibly) calcium binding to troponin regulates skeletal muscle contraction

Describe the orientation of the thick myofilament.

myosin head is toward I band | myosin tail is toward M line

What is titin?

strands of elastic protein that extend from Z line to next M line largest known protein stabilizes position of contractile filaments/attaches them together

What are the mechanisms of force generation in a muscle?

sliding filament model crossbridge cycle excitation-contraction coupling muscle cell metabolism

Describe the sliding filament model.

muscle shortens but neither thick or thin filaments shorten, they slide bast each other

Describe how the length of a sarcomeres' regions change during contraction.

sarcomere - shortens I band - shortens H zone - shortens A zone - remains the same

Describe the steps of the crossbridge cycle.

ATP is hydrolyzed, myosin is in high energy state, binds to actin inorganic phosphate is released powerstroke - actin pulled towards midline of sarcomere ADP released rigor - myosin in low energy form new ATP binds to myosin myosin and actin unbind ATP hydrolyzed cocking of myosin head

What is excitation contraction coupling?

sequence of events where an action potential causes contraction steps: ACh released from motor neuron, binds to receptors in motor end plate (end plate potential, triggers AP in muscle cells) AP propagates along sarcolemma and down T-tubules reachers DHP receptors on T-tubules that trigger ryanodine receptors to open Ca2+ is released from SR into cytosol Ca2+ binds to troponin, moving tropomyosin and exposing myosin-binding sites crossbridge cycle begins, muscle contraction occurs Ca2+ is actively transported back into SR tropomyosin reblocks binding sites on actin, muscle fiber relaxes

What is a powerstroke?

movement of myosin head to propel thin filament in towards the muscle centre

In what ways does a contraction stop?

AChesterase degrades ACh in motor end plate, stops neural impulse in the muscle fiber, causes closure of T-tubule voltage gated Ca2+ channels, ending calcium supply Ca2+ needs to be actively removed from cytoplasm - requires ATP

Describe the roles of ATP in muscle contraction and relaxation.

cross-bridge formation - bind to myosin heads to be hydrolyzed to enter high energy state unbinding of actin and myosin - rebinds to myosin head in low energy state so it unbinds from actin power Ca2+ pump - get calcium back into SR

What is rigor mortis?

state of muscular rigidity begins 2-3 hours after death, lasts about 24 hours Ca2+ ions leak out of SR and allow myosin and actin to bind - no more ATP present so crossbridges cannot detach and ion pumps no longer function - need enzymes to begin digesting decomposing cells

Quiz #3 Flashcards

(44 cards)