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 TissueEpithelium 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

Cuboidalepithelium

Simplecolumnarepithelium

Pseudostratifiedciliatedcolumnarepithelium

Stratifiedsquamousepithelium

Simplesquamousepithelium

Epithelial Tissue

Simple Epithelium

Cuboidalepithelium

Simplecolumnarepithelium

Pseudostratifiedciliatedcolumnarepithelium

Stratifiedsquamousepithelium

Simplesquamousepithelium

Epithelial Tissue

Stratified Epithelium

Collagenous fiber

Looseconnectivetissue

Elastic fiber12

0 µ

m Cartilage

Chondrocytes

10

0 µ

m

Chondroitinsulfate

Adiposetissue

Fat droplets

15

0 µ

m

White blood cells

55

µm

Plasma Red bloodcells

Blood

Nuclei

Fibrousconnectivetissue

30

µm

Osteon

Bone

Central canal

70

0 µ

m

Connective Tissue

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 Tissue3 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

Looseconnectivetissue

Elastic fiber12

0 µ

m

Cartilage

Chondrocytes

10

0 µ

m

Chondroitinsulfate

Adiposetissue

Fat droplets

15

0 µ

m

White blood cells

55

µm

Plasma Red bloodcells

Blood

Nuclei

Fibrousconnectivetissue

30

µm

Osteon

Bone

Central canal

70

0 µ

m

Collagenous fiber

120

µm

Elastic fiber

Nuclei

30 µ

m

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 µmSkeletalmuscle

Multiplenuclei

Muscle fiber

Sarcomere

100 µm

Smoothmuscle

Cardiac muscle

Nucleus

Musclefibers

25 µm

Nucleus Intercalateddisk

Muscle Tissue

Multiplenuclei

Muscle fiber

Sarcomere

100 µm

Skeletal muscle, or striated muscle, is responsible for voluntary movement

Nucleus

Musclefibers

25 µm

Smooth muscle is responsible for involuntary body activities

Nucleus Intercalateddisk 50 µm

Cardiac muscle is responsible for contraction of the heart

senses stimuli and transmits signals throughout the animal

Nervous Tissue

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 ofmuscle 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

Thickfilaments(myosin)

M line

Z line Z line

Thinfilaments(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 ofmuscle fibers

Muscle

Single muscle fiber(cell)

Nuclei

Z lines

Plasma membrane

Myofibril

Sarcomere

Sarcomere

TEM

Thickfilaments(myosin)

M line

Z line Z line

Thinfilaments(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

Relaxedmuscle

M Z

Fully contractedmuscle

Contractingmuscle

Sarcomere0.5 µm

ContractedSarcomere

Sliding filament mechanism of contraction

Interaction of thick and thin filaments

Thinfilaments

ATP Myosin head (low-energy configuration

Thick filament

Thin filament

Thickfilament

Thinfilaments

ATP Myosin head (low-energy configuration

Thick filament

Thin filament

Thickfilament

Actin

Myosin head (high-energy configuration

Myosin binding sites

ADP

P i

Thinfilaments

ATP Myosin head (low-energy configuration

Thick filament

Thin filament

Thickfilament

Actin

Myosin head (high-energy configuration

Myosin binding sites

ADP

P i

Cross-bridgeADP

P i

Thinfilaments

ATP Myosin head (low-energy configuration

Thick filament

Thin filament

Thickfilament

Actin

Myosin head (high-energy configuration

Myosin binding sites

ADP

P i

Cross-bridgeADP

P i

Myosin head (low-energy configuration

Thin filament movestoward 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 (Ca2+) bind to a set of regulatory proteins, the troponin complex

• Muscle fiber contracts when the concentration of Ca2+

is high; muscle fiber contraction stops when the concentration of Ca2+ is low

Myosin-binding site

Tropomyosin

(a) Myosin-binding sites blocked

(b) Myosin-binding sites exposed

Ca2+

Ca2+-binding sites

Troponin complexActinTropomyosin: that blocks myosin from binding to thin filament

Troponin complex: regulatory proteins which binds to Ca2+

Control of muscle contraction

SarcomereCa2+ released from SR

Synapticterminal

T tubule

Motorneuron axon

Plasma membraneof muscle fiber

Sarcoplasmicreticulum (SR)

Myofibril

Mitochondrion

Sarcoplasmic reticulum

Ca2+

ATPasepump

Synaptic terminalof motor neuron

Synaptic cleft T Tubule Plasma membrane

Ca2+

Ca2+

CYTOSOL

SR

ATP

ADPP 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 Ca2+

• The Ca2+ binds to the troponin complex on the thin filaments

• This binding exposes myosin-binding sites and allows the cross-bridge cycle to proceed

Bundle ofmuscle fibers

TEM

Muscle

Thickfilaments(myosin)

M line

Single muscle fiber(cell)

Nuclei

Z lines

Plasma membrane

Myofibril

Sarcomere

Z line Z line

Thinfilaments(actin)

Sarcomere

0.5 µm