3-3 cell nucleus - anatomy and physiology web viewproteins determine cell structure and function....
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Chapter 3
The Cellular Level of Organization
3-3 Cell Nucleus Information Storage in the Nucleus
o DNA Instructions for every protein in the body
o Gene DNA instructions for one protein
o Genetic code The chemical language of DNA instructions
o Sequence of bases (A, T, C, G) Triplet code
o 3 bases = 1 amino acid
3-4 Protein Synthesis The Role of Gene Activation in Protein Synthesis
o The nucleus contains chromosomeso Chromosomes contain DNAo DNA stores genetic instructions for proteinso Proteins determine cell structure and function
3-4 Protein Synthesis The Role of Gene Activation in Protein Synthesis
o Gene activation — uncoiling DNA to use it Promoter Terminator
o Transcription Copies instructions from DNA to mRNA (in nucleus) RNA polymerase produces messenger RNA (mRNA)
3-4 Protein Synthesis The Role of Gene Activation in Protein Synthesis
o Translation Ribosome reads code from mRNA (in cytoplasm) Assembles amino acids into polypeptide chain
o Processing RER and Golgi apparatus produce protein
3-4 Protein Synthesis The Transcription of mRNA
o A gene is transcribed to mRNA in three steps1. Gene activation2. DNA to mRNA3. RNA processing
3-4 Protein Synthesis Step 1: Gene activation
o Uncoils DNA, removes histoneso Start (promoter) and stop codes on DNA mark location of gene
Coding strand is code for protein Template strand is used by RNA polymerase molecule
3-4 Protein Synthesis Step 2: DNA to mRNA
o Enzyme RNA polymerase transcribes DNA Binds to promoter (start) sequence Reads DNA code for gene Binds nucleotides to form messenger RNA (mRNA) mRNA duplicates DNA coding strand, uracil replaces thymine
3-4 Protein Synthesis Step 3: RNA processing
o At stop signal, mRNA detaches from DNA molecule Code is edited (RNA processing) Unnecessary codes (introns) removed Good codes (exons) spliced together Triplet of three nucleotides (codon) represents one amino acid
3-4 Protein Synthesis Translation
o mRNA moves: From the nucleus through a nuclear pore
o mRNA moves: To a ribosome in cytoplasm surrounded by amino acids
o mRNA binds to ribosomal subunits tRNA delivers amino acids to mRNA
3-4 Protein Synthesis Translation
o tRNA anticodon binds to mRNA codon One mRNA codon translates to one amino acid
o Enzymes join amino acids with peptide bonds Polypeptide chain has specific sequence of amino acids
o At stop codon, components separate
3-4 Protein Synthesis How the Nucleus Controls Cell Structure and Function
1. Direct control through synthesis of: Structural proteins Secretions (environmental response)
2. Indirect control over metabolism through enzymes
Chapter 6Osseous Tissue and Bone Structure
6-2 Classification of Bones Structure of a Long Bone
o Diaphysis The shaft A heavy wall of compact bone, or dense bone A central space called medullary (marrow) cavity
o Epiphysis Wide part at each end Articulation with other bones Mostly spongy (cancellous) bone Covered with compact bone (cortex)
o Metaphysis Where diaphysis and epiphysis meet
6-2 Classification of Bones Structure of a Flat Bone
o The parietal bone of the skullo Resembles a sandwich of spongy boneo Between two layers of compact boneo Within the cranium, the layer of spongy bone between the compact
bone is called the diploë
6-3 Bone (Osseous) Tissue Bone (Osseous) Tissue
o Dense, supportive connective tissueo Contains specialized cellso Produces solid matrix of calcium salt depositso Around collagen fibers
6-3 Bone (Osseous) Tissue Characteristics of Bone Tissue
o Dense matrix, containing: Deposits of calcium salts Osteocytes (bone cells) within lacunae organized around
blood vesselso Canaliculi
Form pathways for blood vessels Exchange nutrients and wastes
6-3 Bone (Osseous) Tissue Characteristics of Bone Tissue
o Periosteum Covers outer surfaces of bones Consists of outer fibrous and inner cellular layers
6-3 Bone (Osseous) Tissue Bone Matrix
o Minerals Two-thirds of bone matrix is calcium phosphate, Ca3(PO4)2
o Reacts with calcium hydroxide, Ca(OH)2 o To form crystals of hydroxyapatite, Ca10(PO4)6(OH)2
o Which incorporates other calcium salts and ions
6-3 Bone (Osseous) Tissue Bone Matrix
o Matrix proteins
One-third of bone matrix is protein fibers (collagen)
6-3 Bone (Osseous) Tissue Bone Cells
o Make up only 2 percent of bone masso Bone contains four types of cells
1. Osteocytes2. Osteoblasts3. Osteoprogenitor cells4. Osteoclasts
6-3 Bone (Osseous) Tissue Osteocytes
o Mature bone cells that maintain the bone matrixo Live in lacunae o Are between layers (lamellae) of matrixo Connect by cytoplasmic extensions through canaliculi in lamellaeo Do not divideo Two major functions of osteocytes
1. To maintain protein and mineral content of matrix2. To help repair damaged bone
6-3 Bone (Osseous) Tissue Osteoblasts
o Immature bone cells that secrete matrix compounds (osteogenesis)
o Osteoid — matrix produced by osteoblasts, but not yet calcified to form bone
o Osteoblasts surrounded by bone become osteocytes
6-3 Bone (Osseous) Tissue Osteoprogenitor Cells
o Mesenchymal stem cells that divide to produce osteoblastso Located in endosteum, the inner cellular layer of periosteum o Assist in fracture repair
6-3 Bone (Osseous) Tissue Osteoclasts
o Secrete acids and protein-digesting enzymeso Giant, multinucleate cellso Dissolve bone matrix and release stored minerals (osteolysis)o Derived from stem cells that produce macrophages
6-3 Bone (Osseous) Tissue Homeostasis
o Bone building (by osteoblasts) and bone recycling (by osteoclasts) must balance
More breakdown than building, bones become weak Exercise, particularly weight-bearing exercise, causes
osteoblasts to build bone
6-4 Compact Bone and Spongy Bone The Structure of Compact Bone
o Osteon is the basic unit Osteocytes are arranged in concentric lamellae Around a central canal containing blood vessels Perforating canals
o Perpendicular to the central canalo Carry blood vessels into bone and marrow
6-4 Compact Bone and Spongy Bone
The Structure of Compact Bone o Circumferential lamellae
Lamellae wrapped around the long bone Bind osteons together
6-4 Compact Bone and Spongy Bone The Structure of Spongy Bone
o Does not have osteonso The matrix forms an open network of trabeculaeo Trabeculae have no blood vesselso The space between trabeculae is filled with red bone marrow
Which has blood vessels Forms red blood cells And supplies nutrients to osteocytes
o Yellow bone marrow In some bones, spongy bone holds yellow bone marrow Is yellow because it stores fat
6-4 Compact Bone and Spongy Bone Weight-Bearing Bones
o The femur transfers weight from hip joint to knee joint Causing tension on the lateral side of the shaft And compression on the medial side
6-4 Compact Bone and Spongy Bone Compact Bone Is Covered with a Membrane
o Periosteum on the outside Covers all bones except parts enclosed in joint capsules Made up of an outer, fibrous layer and an inner, cellular layer Perforating fibers: collagen fibers of the periosteum
Connect with collagen fibers in bone And with fibers of joint capsules; attach tendons, and
ligaments
6-4 Compact Bone and Spongy Bone Functions of Periosteum
1. Isolates bone from surrounding tissues2. Provides a route for circulatory and nervous supply3. Participates in bone growth and repair
6-4 Compact Bone and Spongy Bone Compact Bone Is Covered with a Membrane
o Endosteum on the inside An incomplete cellular layer:
o Lines the medullary (marrow) cavityo Covers trabeculae of spongy boneo Lines central canalso Contains osteoblasts, osteoprogenitor cells, and
osteoclastso Is active in bone growth and repair
6-5 Bone Formation and Growth Bone Development
o Human bones grow until about age 25o Osteogenesis
Bone formationo Ossification
The process of replacing other tissues with bone
6-5 Bone Formation and Growth Bone Development
o Calcification The process of depositing calcium salts Occurs during bone ossification and in other tissues
o Ossification Two main forms of ossification
1. Endochondral ossification2. Intramembranous ossification
6-5 Bone Formation and Growth Endochondral Ossification
o Ossifies bones that originate as hyaline cartilageo Most bones originate as hyaline cartilageo There are seven main steps in endochondral ossification
6-5 Bone Formation and Growth Appositional Growth
o Compact bone thickens and strengthens long bone with layers of circumferential lamellae
6-5 Bone Formation and Growth Epiphyseal Lines
o When long bone stops growing, after puberty: Epiphyseal cartilage disappears Is visible on x-rays as an epiphyseal line
Mature Boneso As long bone matures:
Osteoclasts enlarge medullary (marrow) cavity Osteons form around blood vessels in compact bone
6-5 Bone Formation and Growth Intramembranous Ossification
o Also called dermal ossification Because it occurs in the dermis Produces dermal bones such as mandible (lower jaw) and
clavicle (collarbone)o There are five main steps in intramembranous ossification
6-5 Bone Formation and Growth Blood Supply of Mature Bones
1. Nutrient artery and vein A single pair of large blood vessels Enter the diaphysis through the nutrient foramen Femur has more than one pair
2. Metaphyseal vessels Supply the epiphyseal cartilage Where bone growth occurs
3. Periosteal vessels
Blood to superficial osteons Secondary ossification centers
6-5 Bone Formation and Growth Lymph and Nerves
o The periosteum also contains: Networks of lymphatic vessels Sensory nerves
6-6 Bone Remodeling Process of Remodeling
o The adult skeleton: Maintains itself Replaces mineral reserves Recycles and renews bone matrix Involves osteocytes, osteoblasts, and osteoclasts
6-6 Bone Remodeling Process of Remodeling
o Bone continually remodels, recycles, and replaceso Turnover rate varies:
If deposition is greater than removal, bones get stronger If removal is faster than replacement, bones get weaker
6-7 Exercise, Hormones, and Nutrition Effects of Exercise on Bone
o Mineral recycling allows bones to adapt to stresso Heavily stressed bones become thicker and stronger
Bone Degenerationo Bone degenerates quickly o Up to one-third of bone mass can be lost in a few weeks of
inactivity
6-7 Exercise, Hormones, and Nutrition Normal Bone Growth and Maintenance Depend on Nutritional and
Hormonal Factorso A dietary source of calcium and phosphate salts
Plus small amounts of magnesium, fluoride, iron, and manganese
6-7 Exercise, Hormones, and Nutrition Normal Bone Growth and Maintenance Depend on Nutritional and
Hormonal Factorso The hormone calcitriol
Made in the kidneys Helps absorb calcium and phosphorus from digestive tract Synthesis requires vitamin D3 (cholecalciferol)
6-7 Exercise, Hormones, and Nutrition Normal Bone Growth and Maintenance Depend on Nutritional and
Hormonal Factors
o Vitamin C is required for collagen synthesis and stimulation of osteoblast differentiation
o Vitamin A stimulates osteoblast activity o Vitamins K and B12 help synthesize bone proteins
6-7 Exercise, Hormones, and Nutrition Normal Bone Growth and Maintenance Depend on Nutritional and
Hormonal Factorso Growth hormone and thyroxine stimulate bone growtho Estrogens and androgens stimulate osteoblasts o Calcitonin and parathyroid hormone regulate calcium and
phosphate levels
6-8 Calcium Homeostasis The Skeleton as a Calcium Reserve
o Bones store calcium and other mineralso Calcium is the most abundant mineral in the body
Calcium ions are vital to:o Membraneso Neuronso Muscle cells, especially heart cells
6-8 Calcium Homeostasis Calcium Regulation
o Calcium ions in body fluids Must be closely regulated
o Homeostasis is maintained By calcitonin and parathyroid hormone (PTH) Which control storage, absorption, and excretion
6-8 Calcium Homeostasis Calcitonin and Parathyroid Hormone Control
o Affect:1. Bones
Where calcium is stored2. Digestive tract
Where calcium is absorbed3. Kidneys
Where calcium is excreted
6-8 Calcium Homeostasis Parathyroid Hormone (PTH)
o Produced by parathyroid glands in necko Increases calcium ion levels by:
1. Stimulating osteoclasts 2. Increasing intestinal absorption of calcium 3. Decreasing calcium excretion at kidneys
Calcitonino Secreted by C cells (parafollicular cells) in thyroido Decreases calcium ion levels by:
1. Inhibiting osteoclast activity2. Increasing calcium excretion at kidneys
6-9 Fractures Fractures
o Cracks or breaks in boneso Caused by physical stress
Fractures are repaired in four steps1. Bleeding2. Cells of the endosteum and periosteum3. Osteoblasts4. Osteoblasts and osteocytes remodel the fracture for up
to a year
6-9 Fractures Bleeding
o Produces a clot (fracture hematoma)o Establishes a fibrous networko Bone cells in the area die
Cells of the endosteum and periosteumo Divide and migrate into fracture zoneo Calluses stabilize the break
External callus of cartilage and bone surrounds break Internal callus develops in medullary cavity
6-9 Fractures Osteoblasts
o Replace central cartilage of external calluso With spongy bone
Osteoblasts and osteocytes remodel the fracture for up to a yearo Reducing bone calluses
6-9 Fractures Major Types of Fractures
o Transverse fractureso Displaced fractureso Compression fractureso Spiral fractureso Epiphyseal fractureso Comminuted fractureso Greenstick fractureso Colles fractureso Pott’s fractures
6-10 Effects of Aging on the Skeletal System Age-Related Changes
o Bones become thinner and weaker with age Osteopenia begins between ages 30 and 40 Women lose 8 percent of bone mass per decade; men lose
3 percento The epiphyses, vertebrae, and jaws are most affected
Resulting in fragile limbs Reduction in height Tooth loss
o
6-10 Effects of Aging on the Skeletal System Osteoporosis
o Severe bone loss o Affects normal functiono Over age 45, occurs in:
29 percent of women 18 percent of men
6-10 Effects of Aging on the Skeletal System Hormones and Bone Loss
o Estrogens and androgens help maintain bone masso Bone loss in women accelerates after menopause
Cancer and Bone Losso Cancerous tissues release osteoclast-activating factor
That stimulates osteoclasts And produces severe osteoporosis
Chapter 10 Muscle Tissue
An Introduction to Muscle Tissue Muscle Tissue
o A primary tissue type, divided into: Skeletal muscle tissue Cardiac muscle tissue Smooth muscle tissue
10-1 Functions of Skeletal Muscle Tissue Skeletal Muscles
o Are attached to the skeletal systemo Allow us to moveo The muscular system
Includes only skeletal muscles
10-1 Functions of Skeletal Muscle Tissue Six Functions of Skeletal Muscle Tissue
1. Produce skeletal movement2. Maintain posture and body position3. Support soft tissues4. Guard entrances and exits5. Maintain body temperature6. Store nutrient reserves
10-2 Organization of Muscle Skeletal Muscle
o Muscle tissue (muscle cells or fibers)
o Connective tissueso Nerveso Blood vessels
10-2 Organization of Muscle Organization of Connective Tissues
o Muscles have three layers of connective tissues1. Epimysium2. Perimysium3. Endomysium
10-2 Organization of Muscle Epimysium
o Exterior collagen layero Connected to deep fasciao Separates muscle from surrounding tissues
10-2 Organization of Muscle Perimysium
o Surrounds muscle fiber bundles (fascicles)o Contains blood vessel and nerve supply to fascicles
10-2 Organization of Muscle Endomysium
o Surrounds individual muscle cells (muscle fibers)o Contains capillaries and nerve fibers contacting muscle cellso Contains myosatellite cells (stem cells) that repair damage
10-2 Organization of Muscle Organization of Connective Tissues
o Muscle Attachments Endomysium, perimysium, and epimysium come together:
o At ends of muscleso To form connective tissue attachment to bone matrixo i.e., tendon (bundle) or aponeurosis (sheet)
10-2 Organization of Muscle Blood Vessels and Nerves
o Muscles have extensive vascular systems that: Supply large amounts of oxygen
Supply nutrients Carry away wastes
o Skeletal muscles are voluntary muscles, controlled by nerves of the central nervous system (brain and spinal cord)
10-3 Characteristics of Skeletal Muscle Fibers Skeletal Muscle Cells
o Are very long o Develop through fusion of mesodermal cells (myoblasts)o Become very large o Contain hundreds of nuclei
10-3 Characteristics of Skeletal Muscle Fibers The Sarcolemma and Transverse Tubules
o The sarcolemma The cell membrane of a muscle fiber (cell) Surrounds the sarcoplasm (cytoplasm of muscle fiber) A change in transmembrane potential begins contractions
10-3 Characteristics of Skeletal Muscle Fibers The Sarcolemma and Transverse Tubules
o Transverse tubules (T tubules) Transmit action potential through cell Allow entire muscle fiber to contract simultaneously Have same properties as sarcolemma
10-3 Characteristics of Skeletal Muscle Fibers Myofibrils
o Lengthwise subdivisions within muscle fibero Made up of bundles of protein filaments (myofilaments)o Myofilaments are responsible for muscle contraction o Types of myofilaments:
Thin filaments o Made of the protein actin
Thick filamentso Made of the protein myosin
10-3 Characteristics of Skeletal Muscle Fibers The Sarcoplasmic Reticulum (SR)
o A membranous structure surrounding each myofibril o Helps transmit action potential to myofibril
o Similar in structure to smooth endoplasmic reticulumo Forms chambers (terminal cisternae) attached to T tubules
10-3 Characteristics of Skeletal Muscle Fibers The Sarcoplasmic Reticulum (SR)
o Triad Is formed by one T tubule and two terminal cisternae Cisternae
o Concentrate Ca2+ (via ion pumps) o Release Ca2+ into sarcomeres to begin muscle contraction
10-3 Structural Components of a Sarcomere Sarcomeres
o The contractile units of muscleo Structural units of myofibrils o Form visible patterns within myofibrilso A striped or striated pattern within myofibrils
Alternating dark, thick filaments (A bands) and light, thin filaments (I bands)
10-3 Structural Components of a Sarcomere Sarcomeres
o The A Band M line
o The center of the A bando At midline of sarcomere
The H Bando The area around the M lineo Has thick filaments but no thin filaments
Zone of overlapo The densest, darkest area on a light micrograph o Where thick and thin filaments overlap
10-3 Structural Components of a Sarcomere Sarcomeres
o The I Band Z lines
o The centers of the I bandso At two ends of sarcomere
Titino Are strands of protein
o Reach from tips of thick filaments to the Z lineo Stabilize the filaments
10-3 Structural Components of a Sarcomere Thin Filaments
o F-actin (filamentous actin) Is two twisted rows of globular G-actin The active sites on G-actin strands bind to myosin
o Nebulin Holds F-actin strands together
10-3 Structural Components of a Sarcomere Thin Filaments
o Tropomyosin Is a double strand Prevents actin–myosin interaction
o Troponin A globular protein Binds tropomyosin to G-actin Controlled by Ca2+
10-3 Structural Components of a Sarcomere Initiating Contraction
o Ca2+ binds to receptor on troponin moleculeo Troponin–tropomyosin complex changeso Exposes active site of F-actin
10-3 Structural Components of a Sarcomere Thick Filaments
o Contain about 300 twisted myosin subunits o Contain titin strands that recoil after stretchingo The mysosin molecule
Tailo Binds to other myosin molecules
Heado Made of two globular protein subunitso Reaches the nearest thin filament
10-3 Structural Components of a Sarcomere Myosin Action
o During contraction, myosin heads:
Interact with actin filaments, forming cross-bridges Pivot, producing motion
10-3 Structural Components of a Sarcomere Sliding Filaments and Muscle Contraction
o Sliding filament theory Thin filaments of sarcomere slide toward M line, alongside thick
filaments The width of A zone stays the same Z lines move closer together
10-3 Structural Components of a Sarcomere Skeletal Muscle Contraction
o The process of contraction Neural stimulation of sarcolemma
o Causes excitation–contraction coupling Muscle fiber contraction
o Interaction of thick and thin filaments Tension production