Muscle Tissue - Sheet1

Question 1

smooth muscle

Answer 1

Functions: Contractility and Conductivity

No striations

No T-tubules

**Involuntary **

Question 2

myofiber

Answer 2

muscle cells

Question 3

myofibril

Answer 3

Tiny, cylindrical rods within the sarcoplasm of the muscle cell. Responsible for the appearance of cross-striations in muscle cells.

Question 4

myofilament

Answer 4

A component of myofibrils that has three categories: 1) actin filaments (thin) 2) myosin filaments (thick) 3) Z-disk

Question 5

sarcolemma

Answer 5

Plasma membrane. Nucleus located just inside the sarcolemma.

Question 6

sarcoplasm;

Answer 6

cytoplasm of muscle fibers. Surrounds myofibrils and is beneath the sarcolemma

Question 7

sarcoplasmic reticulum

Answer 7

Network of cisterns and/or membranous tubules running between and around myofibrils. Contains sarcoplasm.

Question 8

actin

2 types…

Answer 8

G-actin (globular actin)–a globular monomer that polymerizes to form F-actin (Two helically-wound strands of polymerized G-actin)

Question 9

myosin

Answer 9

thick, extends accross entire A-band, contains myomesin, C-protein, and others.

Question 10

tropomyosin

Answer 10

Fibrous; arranged head to tail in a linear series.

Helically wound along grooves of F-actin helix

Question 11

alpha-actinin

Answer 11

Component of the Z-disk

Holds actin filaments in register by binding them in parallel array

Question 12

troponin complex

Answer 12

3 subunits:

TnT: binds entire troponin complex to tropomyosin

TnC: great affinity for Ca++

TnI: binds to actin, preventing actin-myosin interactions

Question 13

T-tubule

Answer 13

part of the sarcolemma.

typically seen at A-I junctions.

Question 14

triad

Answer 14

Facilitates transmission of electrical impulse from sarcolemma to interior depths of cell.

Question 15

diad

Answer 15

Cardiac muscle? T-tubule + terminal portion of adjacent sarcoplasmic reticulum

Question 16

nebulin

Answer 16

Long, non-elastic protein

Two molecules of nebulin wrap around each thin filament

Help anchor thin filament to Z-disk

Question 17

titin

Answer 17

Helps position myosin filaments precisely within the sarcomere. Extends from each half of a myosin filament to the Z-disk Helps keep myosin fillaments centrally located by acting like a spring

Question 18

caveolae

Answer 18

Pinocytotic-like invaginations of sarcolemma

Probably play the role of the T-tubules found in skeletal and cardiac muscle

May work in concert with sarcoplasmic reticulum to modulate Ca++ availability

Question 19

dense bodies

Answer 19

Smooth muscle only!

Two locations: 1) Inner aspects of sarcolemma

2) Throughout cytoplasm

Comparable to Z-disks of skeletal & cardiac muscle Contain alpha-actinin

Serve as anchor sites for actin-myosin interactions as well as intermediate filaments (vimentin; desmin)

Question 20

Z-disk

Answer 20

Dense-staining; narrow.

Distance between two Z-disks = a sarcomere

Question 21

Sarcomere

Answer 21

functional unit of the myofibril. defined as that portion of a myofibril extending from Z-disk to Z-disk.

Question 22

intercalated disk

Answer 22

Complex of several types of cell-to-cell junctions:

Gap junctions (nexuses)

Desmosomes Fascia adherens (serve as anchoring points for actin filaments)

Question 23

I-band, A-band, H-band

Answer 23

I-band: narrower, light-staining band, becomes smaller; may disappear as muscle shortens.

A-band; broad, dark-staining band, represents myosin filaments, remains contant during contraction.

H-band: pale-staining and narrow, narrows and is eventually obliterated in contraction.

Question 24

Junction of A and I band = ?

Answer 24

T (transverse) tubule

Question 25

What are the three regulatory molecules in skeletal muscle?

Answer 25

1. **Troponin complex** 2. **tropomyosin ** 3. **Ca++**

Question 26

Ca++ as a regultory ion

Answer 26

**Binds to TnC** induces a **conformational shift in tropomyosin**, **exposing** previously blocked **active sites on the actin filament**

Question 27

In skeletal muscle, the breadth of the _____ stays the same during contraction, while the breadth of the _____ and ____ get shorter.

Answer 27

A band; I band and H band

Question 28

Endomysium

Answer 28

Sheath of fine c.t. around individual muscle fibers Fine reticular fibers and ground substance

Question 29

Perimysium

Answer 29

Connective tissue sheath **around groups of muscle fibers** (fasicles) _**\*\*Continuous with tendon fibers\*\*\***_

Question 30

Epimysium

Answer 30

Outermost sheath of c.t.; **surrounds entire muscl**e

Question 31

Synaptic vesicles of skeletal muscle fibers

Answer 31

In axon terminals **Contain acetylcholine**

Question 32

Motor end plates (structure and function)

Answer 32

form **myo-neural junctions**

Question 33

Golgi tendon organs (structure and function)

Answer 33

Structure: Spindle-shaped bodies comprised of collagen and enclosed by a thin capsule Afferent (sensory) fibers penetrate between the collagen fibers Sensitive to **stretching forces on tendons (aka reflexes)**

Question 34

SYNAPTIC VESSICLES CONTAINING ________ WILL RELEASE UPON ________ AND INTERACT WITH ACETYLCHOLINE RECEPTORS. ACETYLCHOLINE IS BROKEN DOWN BY ACETYLCHOLINE ESTERASE.

Answer 34

ACETYLCHOLINE; Depolarization

Question 35

describe what Purkinje fibers are and do

Answer 35

play a role in cardiac conduction system; Contain more sarcoplasm Nuclei more rounded Large diameter Lack T-tubules More glycogen

Question 36

Muscle spindle

Answer 36

Structure: ** Internal capsule** immediately surrounds intrafusal fibers; encloses inner axial space **External capsule** surrounds internal capsule and creates (periaxial space) between inner and outer capsules

Question 37

Skeletal Muscle Hypertrophy referes to what?

Answer 37

Due to **increase in size** of fibers, not number

Question 38

cardiac muscle-- significant characteristics

Answer 38

**Striated (involuntary)** with **lots of MITO** **Single nucleus/cell; centrally located**—good diagnostic tool. Have intercalated disks.

Question 39

Intercalated disks of cardiac muscle

Answer 39

Dark cross-bands; frequently appear step-like Occur where a Z-disk should be observed Mark spots of cell-cell attachments (i.e, at ends of cells)

Question 40

Atrial granules

Answer 40

**Unique to atrial cardiac muscle cells** Contain **atrial natriuretic peptide** which functions to **lower blood pressure** **Decreases renal tubules capability to resorb (conserve) sodium and water**

Question 41

Contractile mechanisms of smooth muscle

Answer 41

**Ca++**(probably stored in caveolae) + **calmodulin** form a complex --\> activates **myosin light chain kinase** --\> phosphorylates one of the two **light chains associated with the myosin** molecule head.

Question 42

Innervation of smooth muscle

Answer 42

1. **sympathetic innervations**: synaptic vesicles contain **norepinephrine** 2. **parasympathetic innervation:** synaptic vesicles contain **acetylcholine** 3. variations in numbers of cells in a group that are innervated