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Anatomy > Muscle Histology > Flashcards

Muscle Histology Flashcards

1
Q

One muscle type that is consciously controlled

A

skeletal muscle

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2
Q

T/F: skeletal muscle doesn’t have to cross a joint

A

False
ALL skeletal muscles must cross a joint in order to create movement

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3
Q

functions of skeletal muscles

A
  • body movement
  • posture
  • respiration
  • production of body heat
  • communication
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4
Q

4 basic properties of muscles

A
  • CONTRACTILITY
  • EXCITABILITY (capacity to respond to a stimulus by producing action potentials. In SM, always neurons)
  • EXTENSIBILITY (can be stretched beyond resting length and still contract)
  • ELASTICITY (ability to recoil)
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5
Q

muscles cells are also known as…

A

muscle fibres

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6
Q

skeletal muscle structure

A
  • Composed of fibres, CT, blood vessels, nerves
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7
Q

structure of muscle fibres

A
  • long
  • cylindrical
  • multinucelated
  • striated proteins
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8
Q

why are muscle cells multinucleated?

A

myoblasts fused together to form single muscle cells

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9
Q

how does muscle attach onto bone

A

via tendons (dense regular collagenous CT)
that attach to periosteum (dense irregular collagenous CT)

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10
Q

what are muscle fibres surrounded/separated by?

A

ENDOMYSIUM
(loose areolar CT)

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11
Q

bundles of muscle cells (fibres) are called…

A

fascicles

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12
Q

what holds a single fascicle together?

A

PERIMYSIUM

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13
Q

What bundles all fascicles together?

A
  • EPIMESIUM
  • FASCIA (surrounds groups of muscles)
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14
Q

layer of connective tissue in muscle (outside to inside)

A
  • fascia (surrounds groups of muscles)
  • epimysium (surrounds muscles)
  • perimysiuum (surrounds fascicles)
  • endomysium (surrounds muscle fibres)
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14
Q
A
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15
Q

each muscle cell gets _ connection to a neuron

A

ONE
allows for 1 neuron to contract many cells at the same time

16
Q

synapse between neuron and muscle cell

A

neuromuscular junction

17
Q

muscle fibre structure

A
  • SARCOLEMMA (plasma membrane, where AP occur)
  • SACROPLASIM
  • SACROPLASMIC RETICULM (stores calcium)
  • MYOFIBRILS (long cylindrical groups that contain MYOFILAMENTS actin and myosin)
  • TRANSVERSE TUBULES (surround myofibrils, connect to sarcolemma, allow APs to move through cell)
  • nuceli
  • mitochondria
18
Q

structure of myofibril

A

highly organized pr-
- SARCOMERES along length contain MYOFILAMENTS (actin + myosin) separated by Z disks

19
Q

name and function of enlarged regions of saroplasmic reticulum near transverse tubule

A

TERNIMAL CISTERNAE
- store calcium to release into myofibrils when AP occurs

20
Q

thick filament and thin filament

A

thick: myosin
thin: actin

21
Q

sarcomeres

A

units of contractile pr- that are connected in series along the length of the muscle

22
Q

What connects pr- in sarcomeres to outside of cell?

A

dystrophin pr- connects to membrane pr- in sarcolemma that connects to larger CT

23
Q

M line

A

“middle line” of sarcomere

24
Q

Z disks

A
  • ends of sarcomeres
  • z-shaped proteins
  • attached to actin
25
Q

titin

A
  • gives muscles elasticity
  • pulls z disks closer to m line
  • ends: coiled, connected to z disk
  • middle: straight, connected to m line

longest protein in body!

26
Q

actin myofilament structure + function

A

Structure:
- double helix shape
- F-ACTIN molecules (string) made of G-ACTIN molecules with ACTIVE SITES that can bind to myosin
Regulatory proteins
- TROPOMYOSIN (string-like)
- TROPONIN (binds to G actin, Ca2+ and tropomyosin)

Function
Ca2+ binds to troponin, pulls tropomyosin away from active sites on G actin so actin can bind to myosin via CROSS BRIDGE

27
Q

Myosin myofilament structure + function

A

Structure:
Rod
- 2 myosin heavy chains
Head
- myosin heads (attaches to actin via cross bridge)
- myosin light chains attached
-myosin ATPase
In between
- hinge region

28
Q

Sarcomere organization (bands)

A
  • z disk
  • M line
  • I band (only actin and z disk)
  • H zone (only M line and myosin, no actin)
  • A band (myosin length)

*A bands won’t change size, but H zone and I band can depending on actin-myosin overlap zones

29
Q

connection between action and myosin

A

cross bridge

30
Q

explain NMJ functioning starting with AP

A
  1. Action potential arrives at presynaptic terminal, voltage-gated calcium channels open
  2. Ca2+ enters presynaptic terminal, release of acetylcholine from synaptic vesicles
  3. ACh diffuses across syaptic cleft and binds to ACh receptors on motor end plate, increasing permeability of ligand-gated sodium channels
  4. Na+ into postsynaptic membrane= depolarization
  5. Once threshold has been reached an action potential results, AP moves in all directions AWAY from NMJ
  6. ACh broken down in synaptic cleft by acetylcholinesterase (into acetic acid and choline)
  7. Choline is reabsorbed by presynaptic terminal and combined with acetic acid to form more ACh in synaptic vesicles
    Acetic acid is taken up by many cell types
31
Q

How does muscle contraction occur, starting with the delivery of an action potential in a presynaptic bulb of a NMJ?

A
  1. AP travels along axon membrane to a NMJ
  2. Voltage gated Ca2+ open, Ca2+ into presynaptic terminal
  3. Acetylcholine released from presynaptic vessicles
  4. Ach stimulates ligand gated Na+ channels on motor end plate
  5. Na+ into muscle fibre, depolarization, stimulates AP that travels along sarcolemma and into transverse tubules
  6. AP causes opening of voltage gated Ca2+ channels in terminal cisternae, Ca+ released
  7. Ca2+ binds to troponin, tropomyosin moves away from active site on G-actin molecule
  8. ATP on myosin heads broken down into ADP and P, which release energy needed to move myosin heads
    - P released to form cross bridge
    - ADP released for power stroke
    - ATP releases myosin head from binding site
    - ATP hydrolyzed to bring myosin head to ready position
    *as long as Ca+ present, cycle repeats

Anatomy (36 decks)

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