Muscle Lecture For Exam 2

Front 1

Muscle composition and function

Back 1

Made of muscle cells and connective tissue. (conn. contains blood and supplies nerves to the muscle and serves as a "harness to transmit forces of musclular contraction)

Contractiility and conductivity

Front 2

Muscle Tissue

Back 2

Smooth (unstriated;involuntary; visceral
Skeletal (striated voluntary)
Cardiac (striated involuntary)

Front 3

Embrylogically Muscle comes from

Back 3

Mesoder

Front 4

Sarcoplasm

Back 4

cytoplasm

Front 5

sarcolemma

Back 5

plasma membrane

Front 6

sarcoplasmic reticulum

Back 6

S-ER

Front 7

sacromere

Back 7

linear unit

Front 8

myofilaments

Back 8

myofibrils

Front 9

myfibers

Back 9

muscle cells

Front 10

Sketal Muscle General Features

Back 10

Striated (voulntary)
T-tubule system
well developed sarcoplasmic reticulum
multinucleated
nuclei located at cell periphery (just inside sarcolema)

Front 11

Skeletal muscle Fibers (myofiber) Shape

Back 11

Cylindrical (variations in length 1mm to 4cm) Bulky muscles have larger cells; smaller are smaller.

Several hundred nuclei just inide sarcolemma, flattened oval and elongated in appearanc

Front 12

Myofibrils are?

Back 12

Tiny cylindrical rods within sarcoplasm of muscle cell, responsible for appearance of cross striations of muscle (due to registry of alternating ligh and dark portions of myofibrils adjacent to one another)

Appear as small dots when viewed cross sectionally
Bands, zones, lines and functional units of myofibril

Front 13

A-band of myofibril

Back 13

Broad, dark staining band, anisotropic band

Front 14

I band of myofiril

Back 14

Narrower light staining band, isotropic bond

Front 15

z disk (z-line) myofibrins

Back 15

Dense staining;narrow
Bisects I band, distance between 2 z disks=sarcomere

Front 16

Sarcomere

Back 16

Distance between 2 z disks, functional unit of myofibril. Many, many sacro. line up end to end to form myofibril.

LENGTH varies as a function of contration

Front 17

H band

Back 17

Pale staining; narrow
bisects A band
In middle of sacromere

Front 18

M line

Back 18

thin, bisects H band

Front 19

Myofibrils are comprised of?

Back 19

Finer myofilaments
1. Actin filaments (thin) extend from z disks to edge of H band
2. Myosin Fialaments (thick!!)
extend from one end of A band to other end of A band, forms thin cross bridges that extend from each mysoin filament towards actin filaments. This creates M line (at center of H band)

Front 20

M line

Back 20

At center of H band, contains myomesin, c protein and other proteins that interconnect thick myosin filaments to maintain specifi lattice arrangement

Front 21

Z- disk

Back 21

region where attachment of ends of actin filaments in adjacent sacromeres, appears filamentous and somewhat dense, contains a-actinin

Front 22

Sarcoplasm

Back 22

cytoplasm of muscle fibers
A. between myofibrils, beneath sarcoloma, and around nuclie has Golgi and Ribosomes, mitochondria are near nuclie beneath sarcolemma between myofibrils

Front 23

Sarcoplasmic Reticulum

Back 23

Network of cisterns or membrane tubules running between and around myofibriles, tends to form 'collars' at A-I junctions. Binds and releases Ca+

Front 24

Collars at A-I junctions

Back 24

1. INterconnect by longitudinal components
2. Two collars at A-I junction
3. Collars seperated from each other by T-tubules

Front 25

sarcolemma

Back 25

Cell membrane muscle fibers
Numerous invaginations along cell surface. Creates T-tubules (transverse tubules)

Front 26

T-tubules

Back 26

Lumen of T-tubule is continuous with extracellular space.
Wind between myofibrils
Typically seen at A-I junction between the 2 collars of the Sarco. reticulm

Front 27

Triads

Back 27

T-tubule +2 lateral cisternaie of s. Ret.
Membranes of T-tubules appear to be closely coupled to Sar. Ret. memranes (this facilitates transmission of electical impulses from sarcolmma to interior deps of cell)


2 triads/sacromere

Front 28

Myfibrls are made of

Back 28

Actin,-- G actin (Globular actin)which makes F-actin (fibrous actin) 2 helically wound strands of polymerized G-actin
Myosin (4 Light chains and 2 heavy)
Regulatory Molecules

Front 29

Light meromysin

Back 29

Long molecular subunits rigid, packed together longitudinally to form backbone of myosin filament

Front 30

Heavy meromysin

Back 30

Long felxible moleculare subunits
2 components
1. rod like portion parallel to backbone of filament
2. Globular head (extends laterally as a cross bridge from thick myosin fil. to actin fil. no cross bridges at M-line, ATPase activity has actin binding sites.

**Polarized, globular heads directed away from midpoint of myosin filament.

Front 31

Regulatory molecules of myofibrils

Back 31

Tropomyosin
troponin complex
Ca++

Front 32

Tropomyosin

Back 32

fibrous; arranged head to tail in linear series.
Helically wound along grooves of F-actin helix

Front 33

Troponin Complex

Back 33

(3 Subunits)
Tnt: binds entire troponin molecular to tropomyosin
TnC: great affinity for Ca++
TnL: binds to actin,preventing actin-myosin interactions

Front 34

TnT

Back 34

Binds entire troponin molecular to tropomyosin

Front 35

TnC

Back 35

great affinity for Ca

Front 36

TnL

Back 36

binds actin preventing Actin-myosin interactions

Front 37

Ca++

Back 37

binds to TnC, binding to TnC induces a con. shift in tropomyosin exposing previously blocked active sites on actin filament

Front 38

a-actinin

Back 38

component of Z-disk
Holds actin filaments in register by binding them in parallel array

Front 39

Titin

Back 39

large, linear elastic protein
helps position myosin filaments precisely with the sacromere
extends from each ahlf of myosin filament to z-disk

Front 40

nebulin

Back 40

long non elactic protein
2 molecules of nebulin wrap around each thin filament
help anchor thin filament to z-disk

Front 41

Types of gross muscle organization

Back 41

Endomysium, perimysium, epimysium

Front 42

What is the mechanism of action of NPNs?

Back 42

Urea + urease ---> NH4+. this is normal.

if there are not enough H+, Urea + urease --> NH3 (ammonia). that is bad!

you will see rumen alkalosis and systemic acidosis.

Front 43

Vascular Supply to muscle??

Back 43

Larger arteries follow perimysium, arterioles penetrate fascicles, capillaries // individul fibers

Lymphatics in connective tissue septa

Front 44

Nerve muscle association

Back 44

Motor End Plates (form myo-neural junctions)
Sensory Structures

Front 45

Motor end plate components

Back 45

Myelin sheath of axon is lost as nerve fiber approaches surface of muscle cell

Axon branches close to surface of cell
Subneural Apparatus
synaptic vesicles
Motor units

Front 46

Axon branches characterisics

Back 46

Branches occupy recesses in surface of muscle fiber

RECESSES ARE
Synaptic troughs or primary synaptic clefts

Front 47

Subneural apparatus

Back 47

secondary synaptic clefts caused by infolding of sarcolemma

acetylcholinesterase located at surface of sarcolemma

Front 48

synaptic vesicles

Back 48

in axon terminals, contain acetylcholine

Front 49

Motor Unit

Back 49

Motor neuron and muscle fibers innervated by it Ratio of muscle to fiber reflects control
1:1 very fine control
1:1600 very coarse (gross control)

Front 50

Mysathenia Gravis

Back 50

Disease characterized by weakness and easy fatigue of muscles

Autoimmune response to Acetyl Choline receptor

Treatment::: administer ACHe inhibtors, cause both diagnostic and therapeutic values

Front 51

Sensory Structures

Back 51

Muscle Spindles
Golgi Tendon Organ

Front 52

Muscle Spindle

Back 52

Small speciallized muscle fibers in c.t. capsule (SMALL fibers= inrafusal fibers

Two zones.... Central region of Intrafusal fibers--Nuclei chain fibers
-----------nuclear bag fibers

Polar regions are long and tapered

Front 53

Muscle Spinde Capsules

Back 53

Internal capsule-immediately surrounds intrafusal fibers; encloses inner axial space

External capsule surrounds internal capsule and creates periaxial space between inner and outer capsules

Front 54

Innervation of Muscle Spindle

Back 54

Sensory-large fibers form annulospiral or primary endings around nuclear bag and nuclear chain regions...smaller diameter afferts form flower spray or secondaryendings on intrafusal fibers on polar segments

Motor-efferent fibers form motor end plates on either side of mid region of inrafusal fibers.

Front 55

Muscle SPindle

Back 55

Front 56

Muscle Spindle Functions

Back 56

Act like minature strain gauges

Front 57

Golgi Tendon Organs

Back 57

Spindle shaped body comprised of collagen and enclosed by thin capsule

Afferent (sensory) nerve fibers penetrate between collagen fibers

Sensitive to stretching forces on tendon

Front 58

Embryological origins of skeletal muscle

Back 58

loose mesenchyme>myoblasts

myoblasts fuse>mutinucleated myotubes
Myofilaments appear--irregularily arrange at first, gradually align into myofibrils

Front 59

Hypertrophy of muscle

Back 59

due to size increse of fibers not number

Front 60

Cardiac Muscle General Features

Back 60

Striated (involuntary)
T-tubule system
sarcoplasmic ret. less well develped than Skeletal muscle
Single Nucleus/Cell
Nucleus at center of cell
Intercalated disks are a diagnostic feature of this tissue

Front 61

KEY features of cardiac muscles

Back 61

Cells are elongated and brancing, messy placement, one nucleus/cell at center of cell an oval and fairly large...

Have myofibrils that branch and sometimes blend with adjacent myofibrils (less distinct)
Sacromeres A, I bands and Z disks
Sarcoplasm typically seen at each pole of nucleus

Interclated disks-dark cross brands, frequently appear step like
occur where a z disk should, mark spots of cell to cell attachment

Front 62

Myofilaments of Cardiac Muscle and Mitochondria Content

Back 62

Actin and myosin present

Many mitochondria, very regularily spread out between myofibrils

Front 63

T-tubule system and Sarcoplasmic Reticulm of cardia muscle

Back 63

T-tubules-- larger than those in skeletal muscle, at Z line instead of A-I juncti.

Sarco. Ret. Less well developed than skeletal muscle, simple plexiform arrangement of tubular elements no terminal cisternae

Front 64

Intercalated disk of cardiac muscle cells

Back 64

Represent a complex of several types of cell2cell junctions,
Gap junction,
Desmosomes
fascia adherens (serve as anchoring points for actin filaments)

Front 65

Cardiac muscle characteristics
golgi?
Glcycogen?
Fat?
Atrial Granule?

Back 65

Has golgi apparataus,
Glycogen is very abundant
Lots of fat droplets
Atrial granules-are unique to atrial cardiac muscle cells, contain atrial natrueric peptide which fuctions to lower BP

Front 66

Atrial natriuretic Peptide

Back 66

Functions to lower BP
Decreases renal tubule capacity to reabsorve (conserve) Na and H2O

Front 67

Cardiac muscle and connective tissue?
Vascular Supply?
Nerve Supply?
Conductive system?

Back 67

CM is surrounded by CT that form a fine net of reticualr and collagenous fibers, collagenous and elastic fibers occur between bundles of cells

EXCELLENT VS, come from coronary artiers and lymphatic drainage

Nerves branch from sypathetic and parasympathetic nerves to terminate on muscle cells

Conductive: composed of modified muscle fibers, (Purkinje Fibers)

Front 68

Purkinje Fibers?

Back 68

Specialized muscle cells
1. myfibrils are reduced in #,
2. contain more sacroplasm
3.nuclie are rounded
4.large diameter
5.lack T-tubules
6. more glycogen

Front 69

Heart Diagram with Purkinje Fibers

Back 69

Front 70

Cardiac muscle comes from where??

Back 70

Mesoderm>myoblasts, no fusion of myoblasts

Front 71

SMooth muscles General features

Back 71

No striations or T-Tubules.
Found in walls of hollow viscera, (GI tract, portions of urinary and reproductive tracts, walls of BV, larger ducts of cmp. glands)

Acts involuntary, is regualted by autonomic NS, hormones, or local physiological conditions.

Acts for contractility, conductivity, and production of EC products(collagen, elastin, glycoaminglycans etc.)

Front 72

Smooth Muscle Appearance

Back 72

Fusiform shape, ends are tapered, oval nucleus in center of cell takes on a corkscrew appearance durin contraction, form sheets or clusters

Cytoplasm is eosinophilic
CT contibutions, every cells is surrounded by thin external lamina that seperates the PM of ajacent SM cells
Reticular Fibers are prevalent in external lamina, help harness force of contration.

Front 73

Smooth Muscles Electron micros..

Back 73

Mitochondria and other organells cluster at the poles of nuclei,
lots of interweaving filaents
,
thin filaments (tropomysin present, troponin absent)

thick filaments (myosin type 2) difficult to see.

NB- the actin and myosin filaments are not arranged in the percise manner noted is SKM or CAM, they tend to form bundles that run obliquely to cytoplasm. IF's are numerous

Front 74

SM Cells have a special characteristic of??

Back 74

Dense bodies, located along inner aspects of sarcolemma, and scattered in sarcolemma.

Similar to z-disks of SKM and CAM
contain alpha-actinin
serve as anchor sites for actin-myosin filament bundles as well as IF's

Front 75

SM cells also have Caveolae for?

Back 75

Pincytotic activities, may function as the equivalent of T-tubule in SKM and CAM, may work in concert with Sarcoplasmic RETiculum to modulate Ca availability

Front 76

Caveolae in SM Cells?

Back 76

Used to regulate Ca+ availability with The SR. Stores the Ca+

Front 77

Contractile method of SM Cellsq

Back 77

1. Ca+ +calmodulin form complex
2. Ca+-calmodulin complex activates myosin light chain kinase
3.Mysone LC kinase phosphorylates one of the 2 LC's associated with myosin molecule head
4.Phosphor. of LC exposes 'actin-binding' site on myosin head.
a. also allows myosin head to straighten out and form small bipolar filaments.
b.phosph. is slow process (takes time for SM contraction)
c. ATP hydrolysis occurs more slowly also, so SM requires less muscle to contract

Front 78

Innervation of SM cells caused by?

Back 78

Sympathetic Innervation
Parasympathetic Innervations
Variations of number of cells in a group that are inervated.

Front 79

Regeneration of SM cells

Back 79

Reatains mitotic capability, can also be formed from pre-existing pericytes

Front 80

Sympathetic innervations of SM cells?

Back 80

Caused by synaptic vesicles contain norepinephrine

Front 81

Parasympathetic innervation of SM cells?

Back 81

synaptic vesicles contain acetylcholine

Front 82

Variation in # of cells in group that are innervated?

Back 82

Iris SM: every muscle fiber is innervated
SM in GI/uterus: only small % of SM cells are innervated. (impulse transmission from muscle cell to muscle cell accomplished via gap junctions between adj. muscl. cells

Front 83

CONTRACTILE MECHANISM OF SM======Myosin activation,

Front 84

CONTRACTILE MECHANISM OF SM======Myosin activation,

Back 84

Front 85

Myosin activation second view

Back 85

Front 86

SM contraction

Back 86