Review the types of Tissue, Different Cells that make up tissues



Download 32.31 Kb.
Date03.05.2017
Size32.31 Kb.
Test 2 Study guide
Review the types of Tissue, Different Cells that make up tissues.

Review the function of each type of Tissue cells



  • Groups of cells similar in structure and function

  • The four types of tissues

    • Epithelial, classification and examples, functions

    • Connective, classification and examples, functions

    • Muscle, classification and examples, functions

    • Nerve, classification and examples, functions

1)Integumentary system – functions

a. Protection – chemical, physical, and mechanical barrier


  1. Body temperature

    1. Regulated by dilation (cooling) and constriction (warming) of dermal vessels

    2. Sweat glands increase secretions to cool the body

  2. Cutaneous sensation – exoreceptors sense touch and pain

d. Metabolic functions – synthesis of vitamin D in dermal blood vessels

  1. Blood reservoir – skin blood vessels store up to 5% of the body’s blood volume

  2. Excretion – limited amounts of nitrogenous wastes are eliminated from the body in sweat

Skin functions – epidermis and dermis

Epidermis - Stratum corneun

Outermost layer of keratinized cells

Accounts for three quarters of the epidermal thickness

Functions

a. Waterproofing


  1. Protection from abrasion and penetration

  2. Renders the body relatively insensitive to biological, chemical, and physical assau

Dermis - Second major skin region containing strong, flexible connective tissue



  1. Cell types include fibroblasts, macrophages, and occasionally mast cells

and white blood cells
Hair - Helps maintain warmth, alerts the body to presence of insects on the skin, and

guards the scalp against physical trauma, heat loss, and sunlight



  1. Filamentous strands of dead keratinized cells produced by hair follicles

  2. Contains hard keratin, which is tougher and more durable than the soft keratin of the skin

  3. Made up of the shaft projecting from the skin and the root embedded in the skin

  4. Consists of a core called the medulla, a cortex, and an outermost cuticle

  5. A knot of sensory nerve endings (a root hair plexus) wraps around each hair bulb

  6. Bending a hair stimulates these endings, hence our hairs act as sensitive touch receptor.

  7. Alopecia – hair thinning in both sexes

  8. True, or frank, baldness – genetically determined and sex influenced condition (i.e., male pattern baldness)




  1. Skeletal system – Ch 6

Functions - ESSAY

a. Support – form the framework that supports the body and cradles soft organs



  1. Protection – provide a protective case for the brain, spinal cord, and vital organs

  2. Movement – provide levers for muscles

  3. Mineral storage – reservoir for minerals, especially calcium and phosphorus

  4. Blood cell formation – hematopoiesis occurs within the marrow cavities of bones

Composition of bones

a. Osteoblasts – bone-forming cells



  1. Osteocytes – mature bone cells

  2. Osteoclasts – large cells that resorb or break down bone matrix

  3. Osteoid – unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen

  4. Hydroxyapatites, or mineral salts

  5. Sixty-five percent of bone by mass

  6. Mainly calcium phosphates

  7. Responsible for bone hardness and its resistance to compression

Bone deposition

  1. Occurs where bone is injured or added strength is needed

  2. Requires a diet rich in protein, vitamins C, D, and A, calcium, phosphorus, magnesium, and manganese

  3. Alkaline phosphatase is essential for mineralization of bone

  4. Sites of new matrix deposition are revealed by the:

    • Osteoid seam – unmineralized band of bone matrix

    • Calcification front – abrupt transition zone between the osteoid seam and the older mineralized bone

Bone reabsorption

  1. Accomplished by osteoclasts

  2. Resorption bays – grooves formed by osteoclasts as they break down bone matrix

  3. Resorption involves osteoclast secretion of:

    • Lysosomal enzymes that digest organic matrix

    • Acids that convert calcium salts into soluble forms

  4. Dissolved matrix is transcytosed across the osteoclast’s cell where it is secreted into the interstitial fluid and then into the blood

Impotance of calcium in the diet

  1. Calcium is necessary for:

    • Transmission of nerve impulses

    • Muscle contraction

    • Blood coagulation

    • Secretion by glands and nerve cells

    • Cell division

Controling bone remodeling

  1. Two control loops regulate bone remodeling - ESSAY

    • Hormonal mechanism maintains calcium homeostasis in the blood

    • Mechanical and gravitational forces acting on the skeleton

  2. Hormonal remodeling - ESSAY

Rising blood Ca2+ levels trigger the thyroid to release calcitonin

Calcitonin stimulates calcium salt deposit in bone

Falling blood Ca2+ levels signal the parathyroid glands to release PTH

PTH signals osteoclasts to degrade bone matrix and release Ca2+ into the

Blood


  1. Response to mechanical stress - ESSAY

Wolff’s law – a bone grows or remodels in response to the forces or

demands placed upon it

Observations supporting Wolff’s law include


    • Long bones are thickest midway along the shaft (where bending stress is greatest)

    • Curved bones are thickest where they are most likely to buckl

  1. Osteomalacia

    • Bones are inadequately mineralized causing softened, weakened bones

    • Main symptom is pain when weight is put on the affected bone

    • Caused by insufficient calcium in the diet, or by vitamin D deficiency

  2. Osteoporosis

    • Group of diseases in which bone reabsorption outpaces bone deposit

    • Spongy bone of the spine is most vulnerable

    • Occurs most often in postmenopausal women

    • Bones become so fragile that sneezing or stepping off a curb can cause fractures

g. Osteoporosis treatment

Calcium and vitamin D supplements

Increased weight-bearing exercise

Hormone (estrogen) replacement therapy (HRT) slows bone loss

Natural progesterone cream prompts new bone growth

Statins increase bone mineral density


3. Muscle tissue

  • Skeletal and smooth muscle cells are elongated and are called muscle fibers

  • Muscle contraction depends on two kinds of myofilaments – actin and myosin

  • Muscle terminology is similar

Skeletal muscle

  • Packaged in skeletal muscles that attach to and cover the bony skeleton

  • Has obvious stripes called striations

  • Is controlled voluntarily (i.e., by conscious control)

  • Contracts rapidly but tires easily

  • Is responsible for overall body motility

  • Is extremely adaptable and can exert forces ranging from a fraction of an ounce to over 70 pounds

Cardiac Muscle – ESSAY diferences between Striped, Smooth and Cardiac.

  • Occurs only in the heart

  • Is striated like skeletal muscle but is not voluntary

  • Contracts at a fairly steady rate set by the heart’s pacemaker

  • Neural controls allow the heart to respond to changes in bodily needs

Smooth muscle

  • Found in the walls of hollow visceral organs, such as the stomach, urinary bladder, and respiratory passages

  • Forces food and other substances through internal body channels

  • It is not striated and is involuntary

Striated muscle – sarcomere – myofibril

  • Thick filaments – extend the entire length of an A band

  • Thin filaments – extend across the I band and partway into the A band

  • Z-disc – coin-shaped sheet of proteins (connectins) that anchors the thin filaments and connects myofibrils to one another

  • Thin filaments do not overlap thick filaments in the lighter H zone

  • M lines appear darker due to the presence of the protein desmin

  • Thick filaments are composed of the protein myosin

  • Each myosin molecule has a rodlike tail and two globular heads

    • Tails – two interwoven, heavy polypeptide chains

    • Heads – two smaller, light polypeptide chains called cross bridges

  • Thin filaments are chiefly composed of the protein actin

  • Each actin molecule is a helical polymer of globular subunits called G actin

  • The subunits contain the active sites to which myosin heads attach during contraction

  • Tropomyosin and troponin are regulatory subunits bound to actin

Acetylcholinbe synapse

Action potential, Ca++ function, Neurotranmitter vesicles

Pre Syn bulb, Synaptic cleft, Post syn membrane.

Receptors for Ach, degradation of Ach

Pharmacologic action. ACH mimic, blocking

Achase mimic, and blocking AChase.

Sarcoplasmic reticulum and T tubules


  • SR is an elaborate, smooth endoplasmic reticulum that mostly runs longitudinally and surrounds each myofibril

  • Paired terminal cisternae form perpendicular cross channels

  • Functions in the regulation of intracellular calcium levels

  • Elongated tubes called T tubules penetrate into the cell’s interior at each A band–I band junction

  • T tubules associate with the paired terminal cisternae to form triads

Sliding filament model of contraction - ESSAY

  • In order to contract, a skeletal muscle must:

    • Be stimulated by a nerve ending

    • Propagate an electrical current, or action potential, along its sarcolemma

    • Have a rise in intracellular Ca2+ levels, the final trigger for contraction

  • Linking the electrical signal to the contraction is excitation-contraction coupling

  • Once generated, the action potential:

    • Is propagated along the sarcolemma

    • Travels down the T tubules

    • Triggers Ca2+ release from terminal cisternae

  • Ca2+ binds to troponin and causes:

    • The blocking action of tropomyosin to cease

    • Actin active binding sites to be exposed

  • Myosin cross bridges alternately attach and detach

  • Thin filaments move toward the center of the sarcomere

  • Hydrolysis of ATP powers this cycling process

  • Ca2+ is removed into the SR, tropomyosin blockage is restored, and the muscle fiber relaxes

  • Each myosin head binds and detaches several times during contraction, acting like a ratchet to generate tension and propel the thin filaments to the center of the sarcomere

  • As this event occurs throughout the sarcomeres, the muscle shortens

Thin filaments slide past the thick ones so that the actin and myosin filaments

overlap to a greater degree



  • In the relaxed state, thin and thick filaments overlap only slightly

  • Upon stimulation, myosin heads bind to actin and sliding begin

Contraction at the organ level

  • Contraction of muscle fibers (cells) and muscles (organs) is similar

  • The two types of muscle contractions are:

    • Isometric contraction – increasing muscle tension (muscle does not shorten during contraction)

    • Isotonic contraction – decreasing muscle length (muscle shortens during contraction)

Muscle response with change in stimulus

  • Threshold stimulus – the stimulus strength at which the first observable muscle contraction occurs

  • Beyond threshold, muscle contracts more vigorously as stimulus strength is increased

  • Force of contraction is precisely controlled by multiple motor unit summation(recruitment)

  • This phenomenon, called recruitment, brings more and more muscle fibers into play

  • Staircase – increased contraction in response to multiple stimuli of the same strength

  • Contractions increase because:

    • There is increasing availability of Ca2+ in the sarcoplasm

    • Muscle enzyme systems become more efficient because heat is increased as muscle contracts

Muscle metabolism

  • ATP is the only source used directly for contractile activity

  • As soon as available stores of ATP are hydrolyzed (4-6 seconds), they are regenerated by:

    • The interaction of ADP with creatine phosphate (CP)

    • Anaerobic glycolysis

    • Aerobic respiration

Review anaerobic and aerobic respiration, oxygen debt

60% of energy goes to heat production.

Muscle fatigue


  • Muscle fatigue occurs when:

    • ATP production fails to keep pace with ATP use

    • There is a relative deficit of ATP, causing contractures

    • Lactic acid accumulates in the muscle

    • Ionic imbalances are present

  • Intense exercise produces rapid muscle fatigue (with rapid recovery)

  • Na+-K+ pumps cannot restore ionic balances quickly enough

  • Low-intensity exercise produces slow-developing fatigue

  • SR is damaged and Ca2+ regulation is disrupted

Red and white muscle fiber, compare and conjtrast - ESSAY

  • Speed of contraction – determined by speed in which ATPases split ATP

    • The two types of fibers are slow and fast

  • ATP-forming pathways

    • Oxidative fibers – use aerobic pathways

    • Glycolytic fibers – use anaerobic glycolysis

  • These two criteria define three categories – slow oxidative fibers, fast oxidative fibers, and fast glycolytic fibers

Muscles in lever systems Ch 10




  • Lever – a rigid bar that moves on a fulcrum, or fixed point

  • Effort – force applied to a lever

  • Load – resistance moved by the effort

Know how to calculate the force in an example muscle

Load x d1 = Effort x d2
Download 32.31 Kb.

Share with your friends:




The database is protected by copyright ©sckool.org 2020
send message

    Main page