Chapter 24 …. a little anatomy and physiology

Levels of organization in the vertebrate body

Organ and organ systems 1. Cells

Organ and organ systems 2. Tissues - groups of cells with similar structure and function

Organ 3. Organs - structures composed of several different tissues that form structural/functional unit.

4. Organ systems - group of organs that carry out major activities of the body.

Tissues *epithelial *connective *muscle *nerve Four Types

Epithelial Tissue Epithelium covers every major surface of the vertebrate body (inside and out)

Types of epithelial tissues –simple - one layer thick squamous cuboidal columnar –stratified - several cell layers thick Epithelial Tissue

Cuboidal epithelium Simple columnar epithelium Pseudostratified ciliated columnar epithelium Stratified squamous epithelium Simple squamous epithelium Epithelial Tissue

Simple Epithelium

Cuboidal epithelium Simple columnar epithelium Pseudostratified ciliated columnar epithelium Stratified squamous epithelium Simple squamous epithelium Epithelial Tissue

Stratified Epithelium

Collagenous fiber Loose connective tissue Elastic fiber 120 µm Cartilage Chondrocytes 100 µm Chondroitin sulfate Adipose tissue Fat droplets 150 µm White blood cells 55 µm Plasma Red blood cells Blood Nuclei Fibrous connective tissue 30 µm Osteon Bone Central canal 700 µm Connective Tissue

Mainly binds and supports other tissues

Cells scattered embedded in an extracellular matrix Connective Tissue

Matrix consists of fibers in a liquid, jellylike, or solid foundation Connective Tissue

–Collagenous fibers: strength and flexibility –Elastic fibers: stretch and snap back to their original length –Reticular fibers: join connective tissue to adjacent tissues Connective Tissue 3 connective tissue fibers, all protein:

Connective tissue contains cells, including –Fibroblasts that secrete the protein of extracellular fibers –Macrophages that are involved in the immune system Connective Tissue

Loose connective tissue: binds epithelia to underlying tissues and holds organs in place Cartilage: strong and flexible support material Fibrous connective tissue: in tendons, which attach muscles to bones, and ligaments, which connect bones at joints Connective Tissue in Vertebrates

Adipose tissue: stores fat for insulation and fuel Blood: is composed of blood cells and cell fragments in blood plasma Bone: is mineralized and forms the skeleton Connective Tissue in Vertebrates

Collagenous fiber Loose connective tissue Elastic fiber 120 µm Cartilage Chondrocytes 100 µm Chondroitin sulfate Adipose tissue Fat droplets 150 µm White blood cells 55 µm Plasma Red blood cells Blood Nuclei Fibrous connective tissue 30 µm Osteon Bone Central canal 700 µm

Collagenous fiber 120 µm Elastic fiber Nuclei 30 µm Fat droplets 150 µm Fibrous connective tissue Loose connective tissue Adipose tissue

long cells called muscle fibers, which contract in response to nerve signals Muscle Tissue

3 Types of Vertebrate Muscle

50 µm Skeletal muscle Multiple nuclei Muscle fiber Sarcomere 100 µm Smooth muscle Cardiac muscle Nucleus Muscle fibers 25 µm Nucleus Intercalated disk Muscle Tissue

Multiple nuclei Muscle fiber Sarcomere 100 µm Skeletal muscle, or striated muscle, is responsible for voluntary movement

Nucleus Muscle fibers 25 µm Smooth muscle is responsible for involuntary body activities

NucleusIntercalated disk 50 µm Cardiac muscle is responsible for contraction of the heart

senses stimuli and transmits signals throughout the animal Nervous Tissue

Neurons (nerve cells) transmit nerve impulses Glial cells (glia) nourish, insulate, and replenish neurons

Glial cells 15 µm Dendrites Cell body Axon Neuron Axons Blood vessel 40 µm

Dendrites Cell body Axon 40 µm Neuron

Glial cells Axons Blood vessel 15 µm Glial cells

Muscle contraction p. 1105

Bundle of muscle fibers Muscle Single muscle fiber (cell) Nuclei Z lines Plasma membrane Myofibril Sarcomere Vertebrate skeletal muscle structure Muscle Muscle fibers (cell) Myofibril Thin filaments Thick filaments

Myofilaments TEM Thick filaments (myosin) M line Z line Thin filaments (actin) Sarcomere 0.5 µm *Thin filaments consist of two strands of actin and one strand of regulatory protein *Thick filaments are myosin molecules

Myosin (thick)

Actin (thin)

Bundle of muscle fibers Muscle Single muscle fiber (cell) Nuclei Z lines Plasma membrane Myofibril Sarcomere

TEM Thick filaments (myosin) M line Z line Thin filaments (actin) Sarcomere 0.5 µm Sarcomere

Filaments slide past each other longitudinally, producing more overlap between thin and thick filaments A muscle contracts and shortens because its myofibrils contract and shorten. The Sliding-Filament Model of Muscle Contraction

Z Relaxed muscle M Z Fully contracted muscle Contracting muscle Sarcomere 0.5 µm Contracted Sarcomere Sliding filament mechanism of contraction

Interaction of thick and thin filaments

Thin filaments ATP Myosin head (low- energy configuration Thick filament Thin filament Thick filament

Thin filaments ATP Myosin head (low- energy configuration Thick filament Thin filament Thick filament Actin Myosin head (high- energy configuration Myosin binding sites ADP P i

Thin filaments ATP Myosin head (low- energy configuration Thick filament Thin filament Thick filament Actin Myosin head (high- energy configuration Myosin binding sites ADP P i Cross-bridge ADP P i

Thin filaments ATP Myosin head (low- energy configuration Thick filament Thin filament Thick filament Actin Myosin head (high- energy configuration Myosin binding sites ADP P i Cross-bridge ADP P i Myosin head (low- energy configuration Thin filament moves toward center of sarcomere. ATP ADP P i + Cross bridge cycle

A skeletal muscle fiber contracts only when stimulated by a motor neuron When a muscle is at rest, myosin-binding sites on the thin filament are blocked by the regulatory protein tropomyosin The Role of Calcium and Regulatory Proteins

For a muscle fiber to contract, myosin-binding sites must be uncovered This occurs when calcium ions (Ca 2+ ) bind to a set of regulatory proteins, the troponin complex Muscle fiber contracts when the concentration of Ca 2+ is high; muscle fiber contraction stops when the concentration of Ca 2+ is low

Myosin- binding site Tropomyosin (a) Myosin-binding sites blocked (b) Myosin-binding sites exposed Ca 2+ Ca 2+ -binding sites Troponin complex Actin Tropomyosin: that blocks myosin from binding to thin filament Troponin complex: regulatory proteins which binds to Ca2+ Control of muscle contraction

Sarcomere Ca 2+ released from SR Synaptic terminal T tubule Motor neuron axon Plasma membrane of muscle fiber Sarcoplasmic reticulum (SR) Myofibril Mitochondrion Sarcoplasmic reticulum

Ca 2+ ATPase pump Synaptic terminal of motor neuron Synaptic cleft T Tubule Plasma membrane Ca 2+ CYTOSOL SR ATP ADP P i ACh

Control of Muscle Contraction When Ca ++ concentration of the muscle cell cytoplasm is low, tropomyosin inhibits cross-bridge formation and the muscle is relaxed. Action potentials travel to the interior of the muscle fiber along transverse (T) tubules The action potential along T tubules causes the sarcoplasmic reticulum (SR) to release Ca 2+ The Ca 2+ binds to the troponin complex on the thin filaments This binding exposes myosin-binding sites and allows the cross-bridge cycle to proceed

Bundle of muscle fibers TEM Muscle Thick filaments (myosin) M line Single muscle fiber (cell) Nuclei Z lines Plasma membrane Myofibril Sarcomere Z line Thin filaments (actin) Sarcomere 0.5 µm