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
Body temperature
Regulated by dilation (cooling) and constriction (warming) of dermal vessels
Sweat glands increase secretions to cool the body
Cutaneous sensation – exoreceptors sense touch and pain
d. Metabolic functions – synthesis of vitamin D in dermal blood vessels
Blood reservoir – skin blood vessels store up to 5% of the body’s blood volume
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
Protection from abrasion and penetration
Renders the body relatively insensitive to biological, chemical, and physical assau
Dermis - Second major skin region containing strong, flexible connective tissue
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
Filamentous strands of dead keratinized cells produced by hair follicles
Contains hard keratin, which is tougher and more durable than the soft keratin of the skin
Made up of the shaft projecting from the skin and the root embedded in the skin
Consists of a core called the medulla, a cortex, and an outermost cuticle
A knot of sensory nerve endings (a root hair plexus) wraps around each hair bulb
Bending a hair stimulates these endings, hence our hairs act as sensitive touch receptor.
Alopecia – hair thinning in both sexes
True, or frank, baldness – genetically determined and sex influenced condition (i.e., male pattern baldness)
Skeletal system – Ch 6
Functions - ESSAY
a. Support – form the framework that supports the body and cradles soft organs
Protection – provide a protective case for the brain, spinal cord, and vital organs
Movement – provide levers for muscles
Mineral storage – reservoir for minerals, especially calcium and phosphorus
Blood cell formation – hematopoiesis occurs within the marrow cavities of bones
Composition of bones
a. Osteoblasts – bone-forming cells
Osteocytes – mature bone cells
Osteoclasts – large cells that resorb or break down bone matrix
Osteoid – unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen
Hydroxyapatites, or mineral salts
Sixty-five percent of bone by mass
Mainly calcium phosphates
Responsible for bone hardness and its resistance to compression
Bone deposition
Occurs where bone is injured or added strength is needed
Requires a diet rich in protein, vitamins C, D, and A, calcium, phosphorus, magnesium, and manganese
Alkaline phosphatase is essential for mineralization of bone
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
Accomplished by osteoclasts
Resorption bays – grooves formed by osteoclasts as they break down bone matrix
Resorption involves osteoclast secretion of:
Lysosomal enzymes that digest organic matrix
Acids that convert calcium salts into soluble forms
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
Calcium is necessary for:
Transmission of nerve impulses
Muscle contraction
Blood coagulation
Secretion by glands and nerve cells
Cell division
Controling bone remodeling
Two control loops regulate bone remodeling - ESSAY
Hormonal mechanism maintains calcium homeostasis in the blood
Mechanical and gravitational forces acting on the skeleton
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
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
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
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
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