Muscle Tissue (Exam 2) Flashcards Preview

Spring of 2012 > Muscle Tissue (Exam 2) > Flashcards

Flashcards in Muscle Tissue (Exam 2) Deck (45):
0

General characteristics

Excitable tissue
Contracts
Relaxes
Makes up about 40% of the average persons body mass

1

Excitable tissue

Only contracts in response to electrical activity on the surface of the muscle cell membrane

2

General functions

Body movement (skeletal)
Maintenance of posture (skeletal)
Production of heat as a by product of activity (all)
Constriction of organs and blood vessels (smooth)
Production of heart beat (cardiac)

3

Gross anatomy

Connective tissue
Neural innervation

4

Connective tissue

Epimysium
Perimysium
Endomysium

5

Epimysium

Dense connective tissue layer around the whole muscle
Also called fascia

6

Perimysium

CT covering around the bundles of muscle fibers called fasciles

7

Endomysium

Reticular CT that surrounds each of the fibers in the fascile

8

Motor neuron

Specialized nerve cells
Somas are in the spinal cord
Axons extend to muscle fibers
Function: electrically stimulate the muscles to contract

9

Neuromuscular junction

The contact between the axon terminal and the muscle

10

Motor unit

One motor neuron + all the muscle fibers it innervates

11

Sarcolemma

Plasma membrane

12

Sarcoplasm

Intracellular fluid
Contains glycosomes and myoglobin

13

Glycosomes

Store glycogen for energy

14

Myoglobin

Red pigmented oxygen storing protien

15

Microscopic general characteristics

Each fiber is a long cylindrical cell with multiple oval nuclei
Each muscle fiber is made of many myofibrils

16

Myofibrils

Thread like structures that extend from one end of the muscle to the other
Made of myofilaments

17

Myofilaments

Action (thin filament)
Myosin (thick filament)

18

Actin

Each myofilament is made of:
Tropomyosin
Troponin
F-actin

19

F-actin

Fibrous actin
Coiled to form a double helix
Made of 200 G-actin

20

G-actin

Small globular protiens
Has an active site to which myosin binds during contraction

21

Tropomyosin

Stabilizing protien that winds along a groove in the F-actin strand

22

Troponin

3 polypeptide complex

TnI bonds to G-actin
TnT binds to tropomyosin, anchoring it to the F-actin strand
TnC binds to Ca+2

23

Myosin

Each filament has:
a rod like tail consisting of two entwined polypeptide chains
Two heads that have three components each

Binding site for actin
Binding site for ATP
Hinge region

24

Binding site for actin

Has ATPase activity
Splits an ATP to yield ADP, Pi, and energy

25

Hinge region

Junction of the head and the tail
Allows the head to bend and straighten during contraction

26

Z-disk/line

Protien attachment site for the actin

27

Sarcomer

Structural units of actin and myosin
Functional unit of a muscle

Extends from one Z-disk to another
Striations can be seen under a microscope due to alternating light and dark bands

A bands
I bands
H zone
M line

28

A bands

Dark bands consisting of actin and myosin

29

I bands

Light bands consisting of actin only

30

H zone

Band in the middle of the A band
Myosin only

31

M line

One in the middle of the H zone that holds the myosin in place

32

Sarcoplasmic reticulum (SR)

Surrounds each myofibril
Upon electrical stimulation it releases Ca+2 from the lateral sacs

33

Transverse tubule (T-Tubule)

Invagination of the muscle cell sarcolemma
Runs between lateral spaces to form a triad (1 t tubule+2 lateral sacs= a triad)
Functions to quickly transmit AP through out the muscle cell

The AP signals the release of Ca+2 from the lateral sacs

34

Functions of ATP

Contraction
Relaxation

35

Contraction

Powers the ratcheting movement of the myosin head
After each ratcheting movement a new ATP molecule binds to the myosin head so it can detach, then bind again to the next G-actin molecule

36

Relaxation

Powers the pump that removes Ca+2 from the sarcomere

37

Muscle metabolism

Continuous muscle contraction requires continuous ATP production
Accomplished via 3 pathways:
Direct phosphorylation
Anaerobic respiration/glycolysis
Aerobic respiration/oxidative phosphorylation

38

Direct phosphorylation of ADP by creatine phosphate (CP)

CP is an extremely high energy molecule that is stored in muscle
1st source of energy
Reaction:
Creatine phosphate + ADP= creatine + ATP
Enzyme: creatine kinase
Yield: 1 ATP per creatine phosphate
About 15 seconds of activity

39

Anaerobic respiration/glycolysis

Does not require O2
Involves catabolism of glucose that has been obtained from the blood stream or from the breakdown of glycogen stores in the muscles (within glycosomes)
Reaction: the glucose is broken down into ATP and pyruvic acid
Yield: 2 ATP per 1 glucose
About 30-60 seconds of activity

40

Aerobic respiration/oxidative phosphorylation

Requires O2
Pyruvic acid from glycolysis is transferred to the Kreb's cycle
Within mitochondria high energy bonds are broken and ATP is released
Yield: 34 ATP per 1 glucose
Hours at activity

+ the 2 from glycolysis

41

Skeletal muscle fiber types

Slow oxidative fibers
Fast glycolytic fibers
Fast oxidative fibers

Most muscles are a mixture of fiber types
The predominant type can change based on need/use

42

Slow oxidative fibers

Myosin ATPases work slow, therefore speed of contraction is slow
Uses oxidative phosphorylation for ATP production
Red in color due to high myoglobin stores
Relatively fatigue resistant and have high endurance
Uses: long distance running and posture

43

Fast glycolytic fibers

Myosin ATPases work fast therefore speed of contraction is fast
Uses glycolysis to generate ATP
White in color because there is no need for oxygen so no need for myoglobin
Very susceptible to fatigue because of limited glycogen stores
Uses: short term intense movements like lifting a large load

44

Fast oxidative fibers

Intermediate between slow oxidative and fast glycolytic
Myosin ATPases work fast therefore speed of contraction is fast
Uses oxidative phosphorylation and glycolysis for ATP production
Has both myoglobin and glycogen stores
Pink in color
Moderately fatigue resistant
Uses: walking

Decks in Spring of 2012 Class (56):