UNIT 3 - Muscle Tissue CH 10

muscle functions, types

what is a muscle tissue?

cells alternating in construction and relaxation

converts chemical energy into mechanical energy

what is excitability in a muscle?

resond to chemicals (stimuli) released from neurons

what is conductivity in a muscle?

ability to propagate/spread electrical signals over membrane

what is contractility in a muscle?

abaility ro shorten and generate force

what is extensibility in a muscle?

ability to be stretched without damaging the tissue

what is elastisity in a muscle?

ability to return to original shape after being stretched

the gernal functions of the muscles…

movement

of the body / body parts

posture

stabilizing ody position

storing and moving material through the body consists of…

1. Smooth and skeletal muscle sphincters prevent the movement of material and regulate organ volumes

2. Smooth muscle in the walls of the digestive system moves material through hollow organs

3. The cardiac muscle moves blood through the arteries

4. Skeletal muscle moves lymph and venous blood

heat production function…

contractions of skeletal muscle (shivering)

What is a skeletal muscle, and what does it consist of?

1. attaches to bone, skin, or fascia

2. striated (light and dark bands

3. voluntary control of contraction/relaxation

4. long, unbranched, multinucleated cells

Function - moves bones, maintains posture

what is a cardiac muscle and what is its function?

1. striated

2. involuntary

3. autorhythmic because of built-in pacemaker cells (generate their own action potential/electrical

4. one nucleus/cell

5. branching fibers

6. intercalated discs and gap junctions

7. many mitochondria

Function - moves blood

what is a smooth muscle and what is its function?

1. in the walls of hollow organs/tubes — blood vessels and digestive tract

2. nonstriated

3. involuntary

4. spindle-shaped fibers

5. 1 nucleus/cell

function - moves material through hollow organs (not the only function)

Types of smooth muscle

1. single unit - cells contact together as a sheet, many cells connected by gap junctions, so fibers contract together

2. multi-unit - individual cells have their own motor neuron ending, cells contract individually

What is fascia, and what are its two components?

Fascia - a sheet of fibrous CT which surrounds muscles

1. superficial fascia

• areolar and adipose CT, deep in the skin

• Function- storage (water and fat), protection, insulation

2. Depp fascia

• dense irregular CT around the muscle

What are the connective tissue components?

1. epimysium - surrounds the whole/entire muscle

2. perimysium - surrounds bundles (fascicles) of 10-100 muscle cells

3. endomysium - surrounds individual muscle cells

what do CT layers extend to become?

to form tendons

how many cells are in a skeletal muscle

many muscle cells (muscle fibers)

Individual cells have their own cell membrane = sarcolemma

What CT layers does a skeletal muscle have?

epimysium, perimysium, and endomysium

They join together to form tendons

Tendons fuse to the peritoneum of the bone

what is aponeurosis?

broad flat tendon sheet

(anterior abdomen, top of skull)

how do mature muscle cells in a skeletal muscle develop?

from numerous myoblast cells that fuse during fetal development → multinucleated

Mature fibers/cells can not divide (satellite cells retain the ability to regenerate

muscle growth results from cell enlargement, not division

what is a sarcolemma?

cell membrane of muscle cell

what is a sarcoplasm?

cytoplasm of muscle cells

contains many mitchondria, myoglobin (red-colored, oxygen-binding protein like hemoglobin), and myofibrils (made of many protein myofilaments)

What is a transverse tubule (T-tubules) in a skeletal muscle?

invaginations/indentations of sarcolemma that penetrate deep into the muscle cell and surround myofibrils

run perpendicular to and are adjacent to the sarcoplasmic reticulum

carry muscle action potentials down deep into the muscle cell

what is a sacrcoplasmic reticulum (SR)?

similar to smooth ER in appearance

used to store calcium and release it during muscle contraction

terminal cisternae = dilated end of SR

What are myofibrils?

many contained in each muscle cell

composed of many protein filaments = myofilaments

what are myofilaments?

thick and thin protein strands arranged to make up the functional unit of a muscle = sarcomere

how many kinds of protein myofilaments are myofibrils made of

3

What are contractile proteins?

Generate force for contraction

1. myosin - thick filament

• contains a tain and a head/cross bridge that projects toward actin

2. Actin - thin filament

• anchored to Z disc / Z line

• has myosin binding site where cross-bridge of myosin will interact

what is a regulatory protein

Turns the contraction on and off

1. Tropinand propomsyosin (T-T complex)

• part of the thin filament

• When the muscle is relaxed, tropomyosin covers the myosin binding site on the actin

• Troponin holds tropomyosin in place

what is a structural protein?

provides proper alignment, elasticity, and extensibility

1. Titin

• main one

• goes from Z disc to M line to help hold myosin in place

What are thick filaments in myosin?

resembles two golf clubs twisted

Myosin heads (cross-bridges) extend toward the thin filaments, attempting to interact with actin

help in place by the M line proteins

What are the thin filaments in actin? (troponin and tropomyosin)

The myosin-binding site on each actin molecule is covered by tropomyosin in relaxed muscle

The thin filaments are held in place by Z lines

What are sarcomeres in the microscopic skeletal system?

1. Myofilaments are arranged in functions units called sarcomeres

2. delineated by Z lines (between 2 Z lines = sarcomere)

3. create alternating dark and light bands = striations

What are the parts and rgions of a sarcomere?

1. I band - light band = actin (and T-T complex around it)

• Z line in the middle of the I Band

• overlap adjacent sarcomeres

2. A Band - dark band = myosin + some actin (where it overlaps myosin)

• H Zone: in the middle of the A band, contains only myosin

• M line: in the middle of the H zone/Aband/sarcomere, adjacent myosins attach

What does the blood supply in the body consist of?

muscles need blood to carry mutrients to cells for ATO production

artery and vein often travel along with nerve

What does the nerve supply in teh body consist of?

1. In order for a muscle to contract, it must receive impulses from motor neurons connected to the central nervous system

2. The cell body is in the CNS, and the axon travels from the cell body to the muscle

3. Motor neuron axons often branch to several muscle fibers

4. loss of nerve supply, paralysis, and atrophy

What consists of the motor unit in the body? (motor neuron + all muscle cells it innervates)

1. Fine control units have fewer cells in the motor unit associated with each motor neuron

2. gross control units have many more cells in the motor unit associated with each motor neuron

3. all muscle cells in motor unit contract together

4. to increase strength of contraction, must increase numner of motor units being used

What is a neuromuscular junction?

Junction between neuron and muscle cell

1. Synaptic cleft - space between 2 neurons or between a neuron and a muscle

2. Axon terminal with a synaptic end bulb

3. motor end plate - muscle cell membrane/sacrolemma under axon terminals/synaptic end bulbs that have receptors for neurotransmitters

4. Function - motor impulse reaches the axon terminal with SEB, neurotransmitter is released onto synaptic cleft, ACh binds with ACh receptor on MEP, impulse spreads over muscle fiber, muscle contraction

What is the sliding filament theory?

1. electrical impulse travels in dendrites of motor meuron

2. electrical impulse travels out axon of motor neuron to axon terminals with synaptic end bulb which contains neurotransmitter-filled vesicles

3. ACh released into synaptic cleft

4. ACh binds to and stimulates receptors on motor end plate of muscle cell membrane/sarcolemma

5. impulse spreads over sarcolemma

6. Impulse goes deep into muscle cell through the transverse tubules

7. Ca++ released from sarcoplasmic reticulum

8. Ca++ combines with t-t complex which then moves to uncover myosin binding side on actin

9. myosin cross-bridges interact with myosin binding site on actin

10. actin slides over myosin

11. sarcomeres shorten, contraction

12. must have Ca++ and ATP to do this!!!!!!

What is relaxation in the muscle?

1. impulse ceases to travel down motor neuron, no more ACh released from SEB

2. ACh still in synaptic cleft is broken down by acetylcholinesterase

3. MEP receptors stop binding ACh and electrical impulses over sarcolemma and impulses traveling down T-tubules cease

4. Ca++ returns to the sarcoplasmic reticulum by active transport

5. t-t complex returns to re-cover myosin binding site one actin

What is atrophy in the muscle?

wasting away of muscles

caused by disuse or damage to the nerve supply

muscle fibers replaced with fibrous tissue

what is hypertrophy in the muscle?

increase in the diameter of muscle fibers

resulting from forcing, repetitive muscular activity and an increase in myofibrils, SR and mitochondria

what is a red muscle fiber?

more myoglobin, capillaries and mitochondria

What are white muscle fibers?

less myoglobin and capillaries give fibers their pale, white color

what are slow oxidative fibers?

most red fibers, much myoglobin, generate ATP aerobically

use APT slowly, slow contractions, resistant to fatigue

what is a fast oxidative-glycolytic fiber?

intermediate fibers

most red fibers, much myoglobin

contract fast

somewhat resistant to fatigue

use aerobic metabolism

What are fast glycolytic fibers?

mostly white fibers, nit as much myoglobin

generate ATP quickly ny anaerobic metabolism

contract quickly

fatigue easily

has more myofibrils, more powerful