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KP222 > Quiz #3 > Flashcards

Quiz #3 Flashcards

1
Q

What is the role of the somatic nervous system?

A

control skeletal muscles

voluntary

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2
Q

What is the role of the autonomic nervous system?

A

control smooth and cardiac muscle

involuntary

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3
Q

What are the divisions of the autonomic nervous system?

A

sympathetic
- fight of flight

parasympathetic
- rest and digest

both innervate most effector organs in antagonistic ways

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4
Q

Describe autonomic neuron pathways.

A

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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5
Q

What is a ganglia?

A

cluster of synapses

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6
Q

How do sympathetic and parasympathetic neurons differ?

A

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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7
Q

Describe the chemicals used in autonomic chemical signalling.

A

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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8
Q

What are the types of adrenergic receptors?

A

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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9
Q

What are varicosities?

A

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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10
Q

What is the adrenal medulla?

A

specialized neuroendocrine tissue associated with SNS

sits ontop of kidney

secretes epinephrine into blood and target tissue

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11
Q

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

A

adrenal medulla
sweat glands
most blood vessels

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12
Q

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

A

muscle fiber innervated by 1 neuron

neuron can innervated multiple muscle fibers

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13
Q

What are the components of somatic neuromuscular junctions?

A 
axon terminals
motor end plates
- on muscle membrane
- folds with many nicotinic receptors
Schwann cell sheaths
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14
Q

Describe skeletal muscle.

A

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

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15
Q

Describe they layers of the skeletal muscle.

A

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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16
Q

What is the sarcolemma?

A

cell membrane specific to muscle

surrounds sarcoplasm, the cytoplasm of the muscle

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17
Q

What are T-tubules?

A

run perpendicular to cell organization, penetrating myofibrils

transmit AP through cell so entire fiber can contract simultaneously

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18
Q

What are myofibrils?

A

organization of protein filaments

- thick and thin

19
Q

What are myofilaments?

A

individual thick (myosin) and thin (actin) filaments

responsible for muscle contraction

20
Q

What is the sarcoplasmic reticulum?

A

membranous structure surrounding each myofibril

main source of calcium

form terminal cisternae

21
Q

What are terminal cisternae?

A

regions with higher concentration of calcium

attached to T-tubules

release calcium into sarcomere to begin muscle contraction

22
Q

What is a triad?

A

1 T-tubule and 2 terminal cisternae

23
Q

What gives muscle its striated appearance?

A

parallel organization of myofibrils

24
Q

What are sarcomeres?

A

contractile unit of muscle

Z line to Z line

25
Q

List the structural components of a sarcomere.

A 
A band
H zone
M line
I band
Z line
26
Q

What is the A band?

A
  • dark band

- full length of thick filament

27
Q

What is the H zone?

A
  • thick filaments

- no overlap

28
Q

What is the M line?

A
  • links thick filaments in the centre of the sarcomere
29
Q

What is the I band?

A
  • light band
  • thin filaments
  • no overlap
30
Q

What is the Z line?

A
  • links thin filaments
31
Q

What is actin?

A

thin, contractile protein

holds myosin binding site

32
Q

What is tropomyosin?

A

regulatory protein that overlaps myosin binding sites on actin

33
Q

What is troponin?

A

regulatory protein that attaches to actin, tropomyosin, and calcium (reversibly)

calcium binding to troponin regulates skeletal muscle contraction

34
Q

Describe the orientation of the thick myofilament.

A

myosin head is toward I band

myosin tail is toward M line

35
Q

What is titin?

A

strands of elastic protein that extend from Z line to next M line

largest known protein

stabilizes position of contractile filaments/attaches them together

36
Q

What are the mechanisms of force generation in a muscle?

A

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

37
Q

Describe the sliding filament model.

A

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

38
Q

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

A

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

39
Q

Describe the steps of the crossbridge cycle.

A

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

40
Q

What is excitation contraction coupling?

A

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

41
Q

What is a powerstroke?

A

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

42
Q

In what ways does a contraction stop?

A

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

43
Q

Describe the roles of ATP in muscle contraction and relaxation.

A

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

44
Q

What is rigor mortis?

A

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

KP222 (7 decks)

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