Lecture 11 Levers And Muscles

Front 1

Muscle tissue is tissue that is specialized for contraction. What are the three main functions of muscles?

Back 1

1) move the skeleton
2) stabilize joints
3) move materials through various passageways in the body

Front 2

There are four major properties of muscles: 1) they are contractile
2) they are excitable
3) they are extensible
4) they are elastic
Explain what is of each of these properties mean

Back 2

1) they are contractile, meaning they can shorten forcefully, but cannot forcefully lengthen.
2) they are excitable, meaning that they contract in response to an external stimulus
3) they are extensible, they can stretch about 30% beyond their resting length
4) they are elastic, meaning that if they are stretch they will develop a counter force to return back to resting length.

Front 3

The stimulus to contract can be either neurogenic or myogenic. Describe them.

Back 3

Neurogenic comes from the nervous system
Myogenic comes from neighboring muscle cells

Front 4

The arrangement of muscles change through the vertebrate lineage. The muscles in fish are largely segmental, with a few specialized limb and jaw muscles. In amniotes, muscles become increasingly differentiated and have much more division or labor. Given this variability in the distribution of muscles in different groups of vertebrates, what happens to the properties of vertebrate muscles? do they change or stay consistent

Back 4

the properties of vertebrate muscles are remarkably consistent

Front 5

Skeletal muscle tissue is the most common type in body.
Location in body: attaches to the skeleton
Control: Voluntary
Myofilament arrangement: striated
stimulus for contraction: Neurogenic

Name the other two basic kinds of muscle in vertebrates and describe the characteristics for each.

Back 5

Cardiac: Location: Heart wall
Control: involuntary
Nuclei: single nucleus
myofilament arrangement: striated
stimulus for contraction: myogenic with neural modulation

Smooth: walls of many visceral organs: digestive and urinary tracts, blood vessel walls; involuntary; single nucleus; random; can be neurogenic or myogenic with neural modulation

Front 6

What ultimately causes muscle contraction?

Back 6

interaction between two kinds of myofilaments: thick and thin filaments

Front 7

What are thick filaments made up of?

Back 7

bundles of the protein MYOSIN, which has a globular head attached to a rod like base

Front 8

What are thin filaments made up of ?

Back 8

protein ACTIN which consists of a string of globular proteins

Front 9

There are two accessary proteins that associate with actin. One of these proteins winds around the actin filament and covers the myosin binding sites when the muscle is inactive, and the other attaches to both actin and the first protein. what are they?

Back 9

Tropomyosin (filamentous); troponin

Front 10

What is a Sacromere?

Back 10

functional contractile unit

Front 11

In a sacromere, where are myosin filaments and actin filaments located?

Back 11

myosin filaments are in the supported in the center of the sacromere by a thin sheet of connective tissue , and actin filaments are secured to the ends of the sacromere at the Z discs

Front 12

there is a length in the sacromere of the myosin filaments and it includes the region where it overlaps with actin. What is the region called

Back 12

A band (dark)

Front 13

The I bands are defined by the length of the actin filaments. describe where they start and end.

Back 13

go from the end of the actin filament in one sacromere, across the Z disc and to the end of the actin filament in the adjacent sacromere.

Front 14

What is the zone that lies within the A band that contains of myosin?

Back 14

H zone

Front 15

What does the H zone disappear?

Back 15

when actin completely overlaps the myosin

Front 16

Do A and I bands remain the same length? why or why not

Back 16

they remain the same length because the actin and myosin don't change length.

Front 17

Myofilaments are bundled together into groups called _____.

Back 17

myofibrils: have a banded appearance dark A bands alternating with light I bands

Front 18

When ___ is released into the cell the muscle cell is stimulated to contract. this binds the troponin and causes its shape to change, pulling the tropomyosin filament away from the myosin binding sites. the myosin then bind to the exposed binding sites

Back 18

Ca2+

Front 19

what is a cross bridge?

Back 19

connection between actin and myosin

Front 20

When is energy needed, for myosin head to attach to actin or detach from it?

Back 20

energy is required to detach it, because myosin has a natural affinity for actin

Front 21

____ binds to myosin head and when it is dephosphorylated by an atpase, energy is released and the bond it broken. when the myosin head releases from the binding site, it pivots back to its original position, ready to bind to the next exposed site. This process continues as long as ___ is present in the cytoplasm

Back 21

ATP; Ca2+

Front 22

actin and myosin filaments are bundled together to form a muscle fiber enclosed in a cell membrane called the ___.

Back 22

sacrolemma

Front 23

surrounding the muscle fiber is a layer of connective tissue called an endomysium. Muscle fibers are in true bundled together to form ____ and then surrounded by another layer of connective tissue called the ______. figure 10-2

Back 23

fasciculus: perimysium

Front 24

groups of fasciculus are bundled together to form what we commonly call a muscle: what are the two layers of connective tissue that surround muscle?

Back 24

epimysium and fascia

Front 25

what is a tendon

Back 25

connective tissue that connects muscle to bone

Front 26

name the connective tissue that surrounds bone which the tendon fuses to

Back 26

periosteum

Front 27

What are the two component to muscle

Back 27

a contractile component make up of myofilament arrays, and an elastic component made up of the connective tissue layers thought out the muscle

Front 28

describe a graded response

Back 28

you can use that same muscle to generate small amounts of force or large amounts of force

Front 29

muscle fibers are organized into motor units. define a motor unit

Back 29

single motor neuron and all of the muscle fibers it supplies.

Front 30

In areas that require fine control, such as the human hand, each muscle will have ____motor units containing a ____ number of fibers

Back 30

many; small

Front 31

When a strong force is required, such as the thigh muscle, muscles will have ___ motor units containing ____numbers of fibers

Back 31

few; large

Front 32

the presence of ??? allows the force a muscle produces to be graded

Back 32

motor units

Front 33

The force of a muscular contraction can also be modulated by the rate at which it is stimulated. What is the name of the phenomenon

Back 33

multiple wave summation

Front 34

what is a twitch fiber

Back 34

type of fiber that rapidly develops tension when stimulated and then relaxes

Front 35

What happens when a muscle is stimulated multiple times slowly ?
what happens when if there are repeated stimulations delivered before the muscle the muscle has time to relax completely?
Finally when happens when the stimulations are delivered so fast that the muscle does not have time to relax at all?

Back 35

1) it twitches, then relaxes back to its resting state after each stimulation. each twitch produces same amount of force.

2) the force peak will increase for the subsequent stimulations

3) a maximal tension plateau is reached and this state is called tetanus (disease called lock jaw where there is uncontrolled stimulation of the muscle and it is unable to relax. )

Front 36

Name one of the factors that tension developed by a muscle depends on. (hint: associated with length tension curve)

Back 36

length of muscle fiber

Front 37

length tension curve resembles upside down U. no tension at the minimum length, rising to max, and dropping back down to zero at the maximum length. describe what is happening at the sacromere level at these three points.

FOCUS 10-1

Back 37

at min length : the actin myofilaments are drawn completely into the array of myosin myofilaments and there is nowhere left for them to go, so NO additional tension can be generated

2) at max tension: there is maximal overlap between actin and myosin so that the max number of cross bridges are formed

3) at the greatest length the muscle is stretched so that the actin myofilaments are pulled completely out of the myosin array such that no cross bridges can be formed , there fore there is no tension

Front 38

what is the length at which maximal tension occurs ?

Back 38

resting length for the muscle, meaning that the typical length of muscles at rest is optimized for maximal force generation