unit 6 myology

What are the three types of muscle tissue?

skeletal, cardiac, and smooth

In which two types of muscles are the muscle cells elongated and considered muscle fibers?

skeletal and smooth muscle cells

What are two key descriptors of skeletal muscle tissue?

striated and voluntary

What type of muscle is nonstriated?

smooth muscle

What type of muscle is this?

smooth muscle

What type of muscle is this?

skeletal muscle

What type of muscle is this?

cardiac muscle

Excitability, is the ability of a cell to _____________.

receive and respond to a stimulus by changing its membrane potential.

Contractility is the ability to ________.

to shorten forcibly when adequately stimulated.

Extensibility is the ability to _______.

extend or stretch

Elasticity is the ability of a muscle cell to ______.

recoil and resume its resting length after stretching.

What is the layer of dense irregular tissue that surrounds the whole muscle?

epimysium

What is the layer of dense irregular tissue that surrounds the fascicles?

perimysium

Muscle fibers are grouped into bundles called:______.

fascicles

What is the layer of connective tissue that surrounds each individual muscle fiber?

endomysium

What are the four important functions of muscle?

1. produce movement

2. maintain posture

3. stabilize joints

4. generate heat while contracting

Muscle attachments can be _____ or _____.

direct or indirect

Direct attachments mean the ______ is fused to the _____.

epimysium, periosteum

Indirect attachments are linked to the bone by ________.

connective tissue wrappings that extend as tendons or aponeurosis

What is the sarcolemma?

plasma membrane surrounding muscle fiber

What is a muscle fiber made up of?

myofibrils + other organelles

What are myofibrils ?

rodlike contractile elements that occupy most of muscle cell

What are myofibril segments called?

sarcomeres

What is the thick filament called in sarcomeres?

myosin

aponeurosis

Fibrous or membranous sheet connecting a muscle and the part it moves / strong sheet of tissue that acts as a tendon to attach muscles to bone

origin

attachment of a muscle that remains relatively fixed during muscular contraction

Insertion

attachment to movable bone

fascia

a band or sheet of fibrous connective tissue that covers, supports, and separates muscle

Muscle Fiber Types

slow twitch and fast twitch / different cell types = different movement

glycogen

Storage form of glucose

Myoglobin

An oxygen-storing, red - pigmented protein in muscle cells.

sarcoplasmic reticulum

specialized endoplasmic reticulum of muscle cells

terminal cisternae

dilated end-sacs of SR which cross the muscle fiber from one side to the other

transverse tubules

System of tubules that provides channels for ion flow throughout the muscle fibers to facilitate the propagation of an action potential.

Z line

A dark thin protein band to which actin filaments are attached in a striated muscle fiber, marking the boundaries between adjacent sarcomeres.

thin filaments

actin, troponin, tropomyosin

actin

A globular protein that links into chains, two of which twist helically about each other, forming microfilaments in muscle and other contractile elements in cells.

What does tropomyosin do ?

it keeps the muscles relaxed (unless signaled) by covering the actin binding sites where myosin heads attach during contraction

Troponin

When a muscle is stimulated, calcium ions flood the cell and bind to troponin. This binding changes troponin's shape, causing it to pull tropomyosin away from the actin filament. With the blocking protein moved, myosin heads can attach to actin and pull.

Myosin

A protein present in muscle fibers that aids in contraction and makes up the majority of muscle fiber

neuromuscular junction

point of contact between a motor neuron and a skeletal muscle cell

Acetylcholine (ACh)

A neurotransmitter that enables learning and memory and also triggers muscle contraction

muscle fatigue

inability of muscle to maintain force of contraction after prolonged activity

cramps

prolonged, involuntary muscular contractions

Rigor mortis occurs because ________.

no ATP is available to release attached actin and myosin molecules

4 steps of muscle contraction

1) ATP binds to myosin head, break cross-bridge that holds actin & myosin together

2) energy from ATP (ATP ==> Pi + ADP) used to changed myosin to energized state

3) myosin binds to actin, forms cross-bridge

4) power stroke

fast twitch fibers

muscle fibers that contract rapidly and forcefully but fatigue quickly

slow twitch fibers

red muscle fibers that are slow to contract but have the ability to continue contracting for long periods of time

intermediate fibers

mid-sized, low myoglobin, more capillaries than fast fibers, slower to fatigue

How are striations formed?

repeating series of dark and light bands along myofibrils

What are the dark regions on myofibrils?

A bands

What are the lighter regions of myofibrils ?

I bands

What is the lighter region in the middle of the A band?

H zone

What protein divides the H zone in half ?

myomesin, M line

What is the lines that separate sarcomeres?

Z disc line

How are cross bridges formed?

during contraction, heads link thick and thin filaments together to form cross bridges