Lecture Final - 231 - Lectures 14, 15, 16

Control of growth

Two growth spurts

• Bran, total body height, and reproductive organs do not grow at same rate

Control of growth- factors

Endocrine factors = promotes or inhibits growth

• Growth hormone

• thyroid hormone

• sex steroids

• cortisol

Environmental factors = need proper nutrition to grow

• Nutrition

Genetics vs environment

• Height mostly due to genetics but better acces to food and nutrition increases height

Growth hormone

• ANTERIOR PITUITARY GLAND secretes GROWTH HORMONE to the LIVER to produce INSULIN-LIKE GROWTH FACTOR

• Insulin-like growth factor does most of growth for cartilage and bone

• Growth hormone has an anti-insulin effect that shifts the body toward using fat for energy

Growth Hormone Disorders

Acromegaly

• Growth hormone released in adulthood thickens cartilage but do not grow taller

Gigantism

• Excess growth hormone during childhood

Dwarfism

• Decreased Growth hormone in childhood

*Usually caused by pituitary tumor which hyper secretes

Steriod Hormones and Thyroid Hormone

Glucocorticoids (cortisol)

• decreased bone productoin

• cell death of osteocytes

Estradiol and Testosterone

• Increased bone formation

• decreases osteoclast activity

  • Important during puberty

  • Ovaries = estrogen faster at closing epiphyseal plates

  • Testosterone slower at closing epiphyseal plates

Thyroid hormone

• permissive effects for other hormones

• stimulates release growth factors

How are bones held together to form joints?

Structural classification (BASED ON TYPES OF CT)

• Fibrous

• Cartilaginous

• Synovial

Functional classification (AMOUNT OF MOVEMENT)

• Synarthrosis

• Amphiarthrosis

• Diarthrosis

*Typically go together

Structural type: FIBROUS

Suture = HELD TOGETHER BY FIBERS

• Only in skull

• Bones overlap, and fibers overlap

Syndesmosis

• JOINT HELD BY LIGAMENT

Gomphosis

• HOLD TOOTH

Structural Type: CARTILAGINOUS

Synchondroses

• United by hyaline cartilage

Symphyses

• United by fibrocartilage

Structural Type: SYNOVIAL

• Held by ligament, but has synovial membrane around joint

• Gap between bones

Other synovial joint structures:

Burse = rolls along with movement (like a ball) which stops friction

Planes of Movement

• Sagittal

  • Bicep curl, lunges

• Frontal

  • Jumping hacks

• Transverse

  • Spinning

Types of Synovial joints - Plane and Hinge

Plane joint

• Non-axial

• Only glide

Hinge joint

• Uniaxial

• Action in one plane

• Flexion, extension

Types of Synovial Joints - Pivot and Condyloid

Pivot

• Uniaxial

• Pronation, supination

Condyloid joint

• Biaxial

• Flexion, extension, adduction, abduction

Types of synovial joints - Saddle and Ball-and-socket

Saddle joint

• Saggital, frontal

• Biaxial

Ball-and-socket

• Multiaxial

Ligaments

• Can stop movement in a different plane

• Limits movement

• Ligaments not vascular (hard to heal)

Damage to Ligaments: Sprains

Hard to put ligament together

Dislocations (luxation)

Ball-and-socket susceptible

Inflammatory and Degenerative Conditions

Inflammation = Immune response

• Bursitis

  • Irritation to bursa

• Tendonitis

  • Irritation to tendons

• Artritis

  • Hyaline cartilage degrading at ends of bones

Inflammatory and Degenerative Conditions

Glucosamine, Chondroitin Sulfate, and Combination

Primary response dropped 20%

Effects of glucosamine and chondroitin sulfate on cartilage

Rate of dying chrondrocytes slowed

Joint Replacement

How is action created in a joint?

Muscles attach to bones and cross joints

• Points of attachment

  • Origin = POA that doesn’t move

  • Insertion = POA that does move

Lever systems

• Longer effort arm = if the effort arm is longer than the load arm, the effort is smaller

• Longer load arm = if the load is further from the fulcrum than the effort, you must apply greater force

Lever Systems - Mechanical advantage

• If the distange to the fulcrum is longer for the effort than compared to the load

Lever system - Mechanical Disadvantage

If the distance to the fulcrum is shorter for the “effort” compared to the “load”, the lever is at a mechanical disadvantage

Lever systems in the body

• Most joints work at a mechanical disadvantage

• The insertion of the muscle is very close to the fulcrum compared to the weight of the load

Lever systems - Classes

1 + 2 = mechanical advantage

3 = mechanical disadvantage

Organization of muscle tissue

Epimysium → Perimysium → Fascicle → Endomysium → Muscle Fiber

• Muscle fiber = muscle cell

Miscroscopic Anatomy

• Muscle cell = bundles of myofibrils

Muscle fiber → Sarcolemma → myofibril

• Myofibril = intracellular proteins

Microscopic Anatomy - Inside a muscle fiber (cell)

• Between myofibrils = Sarcoplasmic reticulum, T-Tubules, mitochondria

• A band = dark space (where there are myosin)

• I band = light space (where there are only actin)

Sarcoplasmic reticulum = STORAGE FOR CALCIUM

Microscopic Anatomy

Myofibrils are bundles of myofilaments

• SARCOMERE = BETWEEN Z DISCS

Microscopic Anatomy - Myofilaments: THICK

Thick filaments = Bundles of Myosin

Microscopic Anatomy - Myofilaments: THIN

Thin filaments = Bundles of actin

• Tropomyosin blocks myosin head from attaching to actin

Sliding Filament Theory

• A band stays the same

• H band disappears (Between ends of actin)

• I band gets smaller (between Myosin)

How does a muscle fiber generate force?

Interaction of myosin and actin generates force

• Sarcomeres shorten

• Filaments slide past each other (SLIDING FILAMENT THEORY)

How does the muscle fiber generate force? - Cross bridge cycling

1. Bind

   1. Calcium causes troponin to move tropomyosin so that myosin can attach

2. Powerstroke

   1. ADP and P released, as head of myosin pushes/pulls

3. Release

   1. Attachment of ATP causes myosin head to release

   2. No release = rigor mortis = no ATP

4. Reset

   1. Calcium go back to sarcoplasmic reticulum - ATP turns into ADP and P

How does production stop?

1. calcium pumps move calcium to SR

2. Calcium no longer binds to troponin

3. Myosin cannot bind to actin - cross bridge cycling stops

What stimulates force production in a muscle?

Stimulation of muscle fiber

• Action potential arrives at axon terminal

• ACh released, binds to receptos on sarcolemma

• Ion permeability of sarcolemma change

• Local change in membrane voltage (depolarization) occurs

• Local depolarization (end plate potential) ignited AP in sarcolemma

Excitation-contraction coupling

• AP travels across the entire sarcolemma

• AP travels along t Tubules

• SR releases Ca2+, Ca2+ binds to troponin; myosin-binding sites on actin exposed, contraction begins

Stimulation of muscle (excitation)

ACh effects are terminated by its enzymatic breakdown in the synaptic sleft by acetylcholinesterase

….

Smooth muscle

Innervation of Smooth Muscle

• Autonomic nerve fibers have varicosities that act like axon terminals

  • This is so one neuron can stimulate multiple cells at one time

• GAP JUNCTIONS ensure stimulation of smooth muscle cells all at once

Arrangement of Myofilaments

Smooth muscle cells “twist and scrunch”

• don’t shorten in one direction