Function of skeletal system and components

Support
Protection
Movement
Storage
Blood cell production

Support (bone and bone tissue)

Bone is hard & rigid; cartilage is flexible, yet strong.

Protection (bone and bone tissue)

Skull protects the brain, ribs, sternum, vertebrae protects organs of the thoracic cavity.

Movement (bone and bone tissue)

Produced by muscles on bones via tendons. Ligaments allow some movement between bones, but they prevent excessive movement.

Storage (bone and bone tissue)

Calcium & Potassium stored, the released when needed.

Blood Cell Production( bone and bone tissue)

Bone marrow that gives rise to blood cells & platelets.

lacunae

Anatomy A cavity, space, or depression, especially in a bone, containing cartilage or bone cells.

canaliculi

a small channel, furrow, or groove, as in some bones and parts of plants

cell bodies(bones)

cell bodies sit within the lacunae

Cell processes (bones)

connect osteocytes together within the bone matrix

Components of bone matrix

Organic- collagen and proteoglycans 35%
Inorganic - Hydroxyapatite; Ca PO4 crystals 65% (give bone weight and bearing)

Components of bone matrix non specific

Rebar = collagen fibers
Cement = hydroapatite

Understand what would happen if bone were deficient in these...inorganic and organic material

Too much collagen and the bone will be too flexible; too much mineral and the bone will shatter when pressure is applied.

Spongy bone

-composed of trabeculae; convey strength w/ lightweight; found in greater proportion in bone epiphyses; found in greater proportions in flat bones; gaps between ossified material are filled with marrow.

Compact bone

found in greater proportion in bone diaphyses; made up of osteons; found lining superficial region of all bones; has central canals.

What's an osteon? Components?

Osteon is a single functional unit of compact bone. Has a single central canal (filled w/ blood vessels).

Diaphyses (body of bone)

the shaft and is made of compact bone. Epiphysis is at the end of the bone, made of spongy bone. Has epiphyseal plate, made of hyaline cartilage; present until growth stops. Epiphyseal line becomes present when growth in length stops. The medullary cavity

Long Bones

longer than they are wide. Ex. humerus/femur

Short Bones

round or cuboid. Ex. carpal/tarsal bones

Flat Bones

thin/flat/slight curve. Ex. skull, scapula, sternum.

Irregular Bones

don't fit anywhere else. Ex. sphenoid, zygomatic, vertebrae, nasal.

Endochondral Ossification

cartilage template is replaced by bone. Most bones are formed this way.

Intramembranous Ossification

takes place in connective tissue membrane. Direct formation of bone with no template.

Zone of Resting Cartilage

is nearest the epiphysis and contains randomly arranged chodrocytes that do not divide rapidly

Zone of Proliferation

chondrocytes produce new cartilage through interstitial cartilage growth. the chondrocytes divide and form columns resembling stacks of plates or coins.

Zone of Hypertrophy

the chondrocytes produced in the zone of proliferation mature and enlarge. thus, a maturation gradient exists in each column.

Zone of Calcification

chondrocytes die, blood vessels grow in, osteoblasts form.

Factors affecting bone growth
Nutrition

lack of calcium, protein and other nutrients during growth and development can cause bones to be small. Vitamin D - necessary for absorption of calcium from intestines, can be eaten or manufactured by the body, a lack causes decreased mineralization of bo

Factors affecting bone growth
Hormones

growth hormone - increases general tissue growth. Thyroid hormone - required for growth of all tissues. Sex hormones, such as estrogen and testosterone. **cause growth at puberty, but also cause closure of the epiphyseal plate

Bone repair process

1. Hematoma *
localized mass of blood
*
2. Callus Formation
3. Callus ossification
4. Bone Remodeling

Hematoma *
localized mass of blood
*

when bone is fractured, blood vessels in the bone are damaged and a hematoma forms resulting in inflammation and swelling of tissues around bones.

Callus Formation

mass of tissue connects the ends of the broken bone and blood vessels grow into the clot.

Callus Ossification

cartilage in external callus is replaced by ossification, which stabilizes the broken bone.

Bone Remodeling

repair not complete until woven bone and dead bone next to fracture site are replaced by compact bone.

Parathyroid Hormone

increases blood calcium levels. Secreted from parathyroid glands, stimulates osteoclast activity.

Calcitonin Hormone

decreases osteoclast activity, which decreases blood calcium levels. Secreted from thyroid gland.

Functions of the muscular system

1. Movement of the body
2. maintenance of posture
3. Respiration
4. Production of body heat
5. Communication
6. Constriction of organs and vessels

Movement of the body

skeletal muscles attached to bones

Maintenance of Posture

Constant maintenance of muscle tone which allows for sitting and standing positions.

Respiration

muscles of the thorax contract

Production of Body Heat

contractions causes heat to be given off; critical for maintenance of body temperature.

Communication

all types: speaking, writing, typing, facial expressions, gesturing.

Constriction of organs and vessels

smooth muscle within walls of internal organs and vessels cause constriction. - leads to mixtures in digestive tract, secretions from organs and blood flow regulation.

Constriction of the Heart

cardiac muscle causes heart to beat, pumping blood to all parts of the body.

Understand the 4 general properties of muscle

1. Contractility
2. Excitability
3. Extensibility
4. Elasticity

1. Contractility

ability of a muscle to shorten with force.

2. Excitability

capacity of muscle to respond to a stimulus (from our nerves).

3. Extensibility

muscle can be stretched beyond its normal resting length and beyond to a limited degree and still contract at the same time.

4. Elasticity

ability of muscle to recoil to original resting length after stretched.

Skeletal Muscle Tissue

responsible for locomotion, facial expressions, posture, respiratory movements, other types of body movement. Voluntary *
conscious control
*

Smooth Muscle Tissue

walls of hollow organs, blood vessels, eye, glands, skin. Propels urine, mix food in digestive tract, dilating/constricting pupils, regulating blood flow. Involuntary - controlled by endocrine and automatic nervous systems.

Cardiac Muscle Tissue

Heart - major source of movement of blood. Involuntary - controlled by endocrine and nervous systems.

Skeletal Muscle Structure

Skeletal muscle fibers are surrounded by a PM called the sacrolema. Immediately superficial to the sacrolema is the external lamina and underneath that is the endomysium.

Skeletal Muscle Structure
a. Make sure you understand this from the smallest component to the largest component.

Multiple skeletal fibers grouped together is called a fasiculus. Each fasiculus is covered by another connective tissue called perimysium. The entire muscle is covered by a connective tissue called the epimysium.

Actin Myofilaments

are thin. Each one is composed of 2 strands of fibrous*
F actin - long strands wound in a helix
, a series of tropomyosin
an elongated protein that winds along the groove of the F actin helix
and troponin
composed of three subunits: one that binds to acti

Myosin Myofilaments

are thick; shaped like golf clubs. It consists of 2 myosin heavy chains wound together to form a rod portion and 2 heads that extend laterally. Myosin heads: can bind to active sites on the G actin molecules to form cross bridges; are attached to the rod

Sarcomeres

the basic functional unit of muscle fiber. The arrangement of actin and myosin myofilaments creates a striated appearance. They are joined end to end to form myofibrils.

What's the sliding filament theory?

A. Actin myofilaments sliding over myosin heads to shorten sarcomeres. Actin and myosin do not change length. Shortening sarcomeres are responsible for skeletal muscle contraction. Durinf relaxation sarcomeres lengthen because of some external force, cont

Resting Membrane Potential

Membrane voltage difference across membranes (polarized)
Inside cell more negative due to accumulation of large protein molecules.
More K+ on inside than outside; K+ leaks out but not completely because negative proteins hold some back.
Outside cell more

Importance of polarized membrane?

relatively high K+ concentrations
but low Na+ concentrations
This is due to the Na+/K+ pump and active transport

What contributes to this charge difference across the membrane?

The inside cell is more negative than the outside due to accumulation of large protein molecules. There's more Na+ on the inside than outside. K+ leaks, but not all of it because some negative proteins hold them back.

Role of Na/K Pump?
i. What does this pump do in detail

The sodium-potassium pump binds 3 intracellular Na+ ions and ATP. The ATP is then broken down and causes a shape change allowing the pump to expose the Na+ ions to the extracellular side. The pump then bind 2 extracellular K+ ions and a phosphate is lost

Types of Ion channels important in muscle contraction

1. Ligand -gated
2. Voltage-gated
**Each is specific for certain ions and are dependent on concentration gradient.

Ligand-gated channels

Ligands: molecules that bind to receptors
Receptor: protein or glycoprotein with a receptor site to which a ligand can bind.
Example: neurotransmitters

Voltage-gated

Open and close in response to small voltage (charge) changes across plasma membrane- (membrane potential changes)
Ca2+, Na+ K+ channels

action potential

a reversal of the resting membrane potential, such that the inside of the cell becomes positive compared to the outside of the cell.

Depolarization- what is happening with

Inside of plasma membrane becomes less negative.
If change reaches threshold an action potential is triggered.
When threshold is achieved, further depolarization occurs and the inside of the cell becomes positively charged

Repolorization- what is happening with

return of resting membrane potential.

All or None Principle

Stimulus is enough to produce a depolarization that meets or exceed threshold an action potential will occur
Stimulus is too weak and depolarization does not reach threshold, membrane potential returns to resting level without producing an action potentia

Propagation

A.P. occur in a very small area of the plasma membrane and do not affect the entire plasma membrane at one time
A.P. can travel across the plasma membrane. Not a physical movement but stimulation of another A.P. at another location.
Ex-Domino effect

Neuromuscular Junction (NMJ)

Axons or motor neurons carry action potentials from the brain and spinal cord to skeletal muscle fibers

Presynaptic Terminal

filled with synaptic vesicles
Axon terminal

Synaptic Cleft

Physical Space between the axon and muscle fiber

Postsynaptic membrane

Sarcolemma *
muscle PM
*

Can you list the steps that occur like you wrote in your notes during class? Look at video...

i. An action potential in the nerve causes voltage gated calcium channels to open; calcium rushes into the presynaptic terminal.
ii. Influx of calcium causes ACH to be released from synaptic vesicles.
iii. ACH is released into the synaptic cleft.
iv. ACH

Importance of Calcium, Ach, Ach-ase, etc....

when calcium rushes in it causes the ACH to be released into the synaptic cleft. ACH binds to the sodium channels in order to get it to open and for the sodium to escape which lead to depolarization. ACH-ase breaks down the ACH forcing acetic acid to diff

Excitation-Contraction Coupling

Mechanism where an action potential causes muscle fiber contraction
Involves
-sarcolemma
Transverse (T) tubules: invaginations of sarcolemma
Sarcoplasmic reticulum(stores calcium): smooth ER
-Ca2+
-Troponin

Cross Bridge Formation
a. Know the steps in order and general idea of what is happening in each? 1-3

1.Exposure of Active Sites
Ca2+ binds to troponin causing tropomyosin to move and exposure of active sites on actin myofilaments (specifically on g-actin monomers)
ADP and P are bound to myosin from previous contractions.
2. Cross-bridge formation
Myosin

Cross Bridge Formation
a. Know the steps in order and general idea of what is happening in each? 4-6

4. Cross Bridge Release
ATP binds to myosin heads causing them to detach from actin myofilaments
5.Hydrolysis of ATP
The ATPase portion of the myosin heads aplit ATP into ADP and Phosphate
ADP and Phosphate remain attached to the myosin heads
6. Recovery

What is a motor unit

a single motor neuron and all of the muscle fibers innervated by it

How can motor units vary in large or small muscles

Large muscles have motor units with many muscle fibers.
Small muscles that make delicate movements contain motor units with few muscle fibers

How can we increase muscle force?

Force of a muscle contraction can be increased in 2 ways:
1. motor unit recruitment: based on the strength of the stimulus.
2. summation: based on the frequency of the stimulus.

Remember muscle has a graded response....

Strength of contraction is graded: ranges from weak to strong depending on stimulus strength

Motor Unit Recruitment-?

The stronger the stimulus the more motor units we need to recruit
The degree of contraction is influenced by the number of motor units being stimulated.

Motor Unit Summation

As the frequency of action potentials increase, the frequency of contraction increases until a period of sustained contraction, tetanus

Incomplete tetanus

muscle fibers partially relax between contraction; Some time between A.P.

Complete tetanus

no relaxation between contractions; A.P. produced too rapidly for rest

What does it mean if a muscle is at optimal length for force production

Muscle produces the most force at optimal length; in optimal length, actin overlap myosin for cross bridge formation.

Types of muscle fatigue

Can occur at 3 sites:
1. Nervous System
Psychological: depends on emotional state of individual
2. Muscles
Muscular: results from ATP depletion
3. NMJ
Synaptic: occurs in NMJ due to lack of acetylcholine

Energy systems information

ATP provides immediate energy for muscle contractions. If adequate ATP is available muscle contract repeatedly for a long time
ATP is produced from three sources:
1. Creatine Phosphate
2. Anaerobic respiration
3. Aerobic respiration

Creatine Phosphate

During resting conditions stores energy to synthesize ATP (creates 1 ATP for each reaction) (1 ATP produces 8 to 10 seconds of energy)

Anaerobic respiration

Occurs in absence of oxygen and results in breakdown of glucose to yield ATP and lactic acid(glycolosis) (2 ATP) (2 ATP last up to 3 minutes of activity)

Aerobic respiration

Requires oxygen and breaks down glucose to produce ATP, carbon dioxide and water
More efficient than anaerobic
Crebs cycle and electron transport chain
These produce (36 ATP per glucose molecule) (can last hours)

Can you explain why rigor mortis occurs?

development of rigid muscles several hours after death.
Ca leaks into sarcoplasm and crossbridges form.
No ATP to release so the tissue stays rigid and (the myosin heads from actin).
Rigor ends as tissues start to deteriorate.

Differences between type I and type II fibers

Slow Twitch or Type I
Fast Twitch or Type II

Slow-twitch *
Type I
*

* Contract more slowly
* Have a myosin that breaks down ATP very slowly
* Smaller in diameter
* Good blood supply
* Many mitochondria
* Postural muscles, more in lower than upper limbs. Dark meat of chicken. Mitochondria make the meat dark.

Fast-twitch
Type 2

Type IIa and Type IIb
* Contain myosin that can break down ATP more rapidly than that in Type I
* Less blood supply
* Fewer and smaller mitochondria than slow-twitch
* Lower limbs in sprinter, upper limbs of most people. White meat in chicken.

Hypertrophy

: increase in muscle size
Increase in myofibrils
Increase in nuclei due to fusion of satellite cells
Increase in strength due to better coordination of muscles, increase in production of metabolic enzymes, better circulation, less restriction by fat

Atrophy

decrease in muscle size
Reverse except in severe situations where cells die

Just wanted 100 slides
Study videos

There are 4 of these:
1. Cross Bridge Formation
2. Neuromuscular Junction Material
3. um im gna edit this later cant remember the rest