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207 Cards in this Set
- Front
- Back
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What is an atom |
smallest particle of an element with all of the properties of that element– protons, electrons, neutrons |
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what is the smallest amount of a substance that can exist alone |
molecule = a combination of atoms |
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what is an organelle |
molecules associate in specific ways to form organelles = basic components of living cells |
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what is a cell |
fundamental structural & functional unit of a living thing; cells vary widely in size & shape, reflecting unique functions in the body |
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what is composed of 2-4 tissue types that function to preform homeostasis for example: stomach (epilelial skin, musclesto churn, muscles to push, etc) |
organs |
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what is a Plasma membrane |
Semi permeable membrane |
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mitochondria |
Generate ATP, ATP synthesis |
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ribosomes |
Found in rough er, makes proteins |
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Rough Endoplasmic Reticulum |
protein synthesis |
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smooth ER |
No ribosomes, concerened with lipids and steriod metabolism |
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Golgi apparatus |
Modificaiton of protein and sorting |
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Lysosomes |
cell digestion centre |
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Peroxisomes |
Detoxifies substances, has catalase |
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microtubules |
Anchors organelles, helps in transportation |
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Microfilaments are made of... |
myosin & actin filmaments |
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role of cilia |
Aid in movement (respiratory system is filledwith cilia) , functions to move liquid |
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role of flagella |
Tail that aids in movement in sperm |
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nucleus |
Storage for DNA and genetic information,required for reproduction |
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necleoli |
Ribosomes synthesis |
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chromatin |
Macromolecule made of DNA, protein, and RNA- how your genetic info is stored, packages of chromatin = chromosome, chromatid is one strand of DNA |
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4 types of tissues |
epithelium, connective, muscle, nervous |
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what is epithelial tissue? |
sheet of cells that covers a body surface or lines a body cavity, creates boundaries |
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2 types of epithelial tissue |
covering and lining epithelium, and glandular epithelium |
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function of epithelial tissue |
protection, absorption, filtration, excretion , secretion, sensory reception PAFESSR |
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special functions of the epithelial tissue: |
1. polarity (apical and basal) 2. special contacts (tight junctions and desmosomes) 3. Supported by connective tissue (basal lining + ct) 4. Basal lamina (noncellular, underlying supportive sheet of primarily glycoproteins - support and filter) 5.Innervated but avascular: nourished by the diffusion of CT (nerve supplybut no blood supply) 6. Regeneration: (high regenerative capacity from the basal lining) |
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different cell shapes include: |
squamous, cuboidal, columnar |
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number of layer of cells |
simple (one), stratified (multiple) |
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4 types of simple epithelial tissue: |
simple squamous/cuboidal/columnar epithelial, pseudostratified columnar Epithelium |
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Simple Squamous Epithelium function and location |
thin & permeable - filtration, diffusion (eg: kidney, lungs) |
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Simple Cuboidal epithelium function and location |
- secretion & absorption (eg: kidney tubules, small glands) |
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Simple Columnar epithelium: function + location |
digestion & secretion (eg. digestive tract) |
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what is pseudostratified columnar Epithelium |
- asingle layer - eg: respiratory tract where cilia and mucus secretion are local specializations - lookslike it’s stratified but it’s not (Single cells end up in different levels, it’sjust not in uniform so it looks stacked) |
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what is transitional epithelium |
- changes shape and form depending on how full the bladder is - lines the bladder, an organ that has to fill – |
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Describe the structure of Stratified Squamous Epithelium |
• Two or more cell layers • Regenerate frombelow • Basal (cuboidal) cells divide, cells migrate to surface • More durable than simple epithelia • Protection is major role |
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what is a gland |
1 or more cells that make & secrete aparticular product |
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Glands are classified by |
Site of product release (endo/exo) Relative number of cells forming the gland (multi/uni) |
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what are endocrine glands |
they are ductless - products are called hormones |
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what are exocrine glands |
• secrete their products onto body surfaces or into body cavities • mucous, sweat, oil/salivary glands, liver,pancreas, etc. |
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properties of Unicellular exocrine glands: |
· no ducts because only one cell! · really just the goblet cells(digestive & respiratory tracts) |
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properties of multicellular exocrine glands |
Epithelium-derived duct & secretory cells; surrounded by supportive CT which brings blood vessels & nerves - classified by structure and mode of secretion |
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different modes of secretion (exocrine glands)
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merocrine/eccrine, holocrine, apocrine |
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describe Merocrine/eccrine |
• most secrete products by exocytosis as secretions are produced • most common type eg pancreas,salivary glands, most sweat glands |
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describe holocrine |
• accumulate products within then cell rupture(along with secretion there are dead skin cell particles) • only eg sebaceousglands |
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describe apocrine |
• accumulate products within, but only cell apexpinches off with secretory product • whether this type exists in humans is controversial |
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Why are adipose, blood, and bone all considered to be connective tissues? |
they have a common origin, mesenchyme |
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Structural elements of connective tissue: |
ground substance, cells, and fibres |
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what is ground substance |
· interstitial fluid + cell adhesion proteins & proteoglycans: molecular sieve · fibronectin, laminin - help cells attach toC T elements |
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types of fibres |
· Collagen fibers: high tensile strength · Elastic fibers: elastin has coiled structure to allow stretch+ recoil · Reticular fibers: thin collagen protein; fine network to support blood vessels, soft tissues |
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describe cells in CT |
· immature (“blast”) forms vs mature (“cyte”)forms · “blasts” are actively dividing/synthesizing cells during growth & repair · “cytes”primarily provide a level of maintenance |
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types of CT |
– Loose connective tissues (Areolar; Adipose; Reticular) – Dense connective tissues ( fibrous connective tissues)(Dense regular; Dense irregular; Elastic) |
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AREOLAR CT |
- LOOSE CT - gel-like matrix with all 3 fibertypes; cells = fibroblasts, macrophages, mast cells, & some WBCs - loose arrangement of fibers; reservoir of water & salts but is also a prime site of edema during inflammatory reaction |
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ADIPOSE TISSUE |
- LOOSE CT - areolar CT modified to store nutrients; adipocytes - fat-filled adipocytes with displaced nuclei; do not reproduce; scanty matrix |
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RETICULAR CT |
- LOOSE CT - like areolar CT, but only reticular fibers |
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Location and function of areolar ct |
Location: widely distributed under epithelia ofbody - e.g. Function: cushioning of organs, immunity(macrophages) & inflammation; fluid reservoir |
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Location and function of adipose ct |
Location: under skin, around kidneys & eyeballs, inbones & within abdomen, in breasts; 18% of average wt (15% ♂ & 22% ♀) Function: fuel reservoir, insulation, supports& protects organs |
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Location and function of reticular ct |
Loc: lymphoid organs(lymph nodes, bone marrow, spleen) Fcn: fibers form softinternal skeleton that supports free blood cells |
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DENSE REGULAR CT |
bundles of collagen fibers runningparallel to direction of pull à white, flexible tissue with greatresistance to tension |
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DENSE IRREGULAR CT |
same as regular, but collagen bundles thicker& arranged irregularly |
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ELASTIC CT |
like dense regular CT, but a very high contentof elastic fibers; found in some very elastic ligaments; walls of large arteries |
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Location and function dense irregular ct |
Location: dermis, submucosa of digestive tract,fibrous capsules of organs & joints Function: withstand tension exerted in manydirections; strength!!! |
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features of cartilage |
features between dense CT &bone à tough, but flexible • avascular, devoid of nerve fibers • collagen fibers (can have some elastic fibers) • up to 80% H2O |
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features of bones |
35 calcium salts give hardness &strength for support/protection of softer tissues; cavities for fat storage & synthesis of blood cells - contains osteoblasts, osteocytes, osteoclasts (break down) |
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why is blood considered a CT? |
consists of cells (RBCs, WBCs) surrounded by a nonliving fluid matrix, blood plasma - fibre content is only visible during clotting |
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Role of CT |
1)Binding or support 2) Protection 3) Insulation/storing reserve fuel 4)Transportation |
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what is a phospholipid bilayer? |
barrier that has long fatty chain (hydrophilic - head and hydrophobic - tail) |
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what is a peripheral protein |
attached to integral proteins (usually internal side of PM); can be enzymes, involved inattachment functions, shape changes |
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what is a cytoskeleton |
anchors to PM; can also interact with receptors |
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what is a glycocalyx |
ensemble of carbohydrates attached to lipids & proteins on extracellular face;“sugar coating” |
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what is cholesterol in phospholipid bilayer |
controls fluidity (reduces fluidity and stabilizes structure) |
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what are integral proteins |
proteins within the phospholipid bilayer, either facing pm or both (channel proteins) |
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functions of integral proteins |
· Clustered to form channels, pores · Others act as carriers to bind to substances · Some are enzymes, others are receptors forhormones or other chemical messengers |
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functions of plasma membrane proteins |
transportation, cell recognition, enzyme activity, receptors, intercellular joining, attachment to ECM |
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what are tight junctions |
fusion of adjacent plasma membranes to prevent passage of molecules (VERY TIGHT!) |
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what are Desmosomes |
anchoring junctions: molecular linking of cells to resist mechanical stress (think velcro) |
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what are Gap Junctions |
molecular channelsbetween cells to allow passage of cytoplasmic molecules, they are electrically-excitable tissues |
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List 4 functions of plasma membranes |
1. effective barrier between the intracellular & extracellular fluids 2. selectively permeable 3. allows the cell to respond to changes in the extracellular fluid 4. site of cell-to-cell interaction and recognition |
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if the inside of the phospholipid bilayer is hydrophobic, how does water pass by? |
by specialized proteins |
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what is interstitial fluid, what does it consist of? |
outside the cell, the cell bathes in it - filtrate of blood - contains salts, sugars, amino acids, vitamins, hormones, metabolites, gases |
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4 types of passive processes |
simple diffusion osmosis facilitated diffusion filtration |
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what factors affect diffusion rate? |
1. Gradient slope 2. Molecule size 3. Temperature |
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what must a molecule be in order to pass through the PLM? |
1. carried 2. lipid-soluble 3. small |
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describe simple diffusion |
nonpolar,lipid-soluble, moves down a gradient |
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Features of facilitated diffusion: |
1) specific 2) not ATP-requiring 3) limited by carrier saturation 4) movement down concentration gradient 5) can be inhibited by certain substances 6) carrier and channel mediated |
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when is carrier mediated facilitation needed? |
for when lipid-insoluble molecules too large to pass through membrane pores/channels |
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describe Channel-Mediated |
•selective due to pore size, charges of a.a. that line channels •some are always open (leakage channels) •opening of others is controlled (gated channels) •can be inhibited, can show saturation & are usually specific |
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describe the process of filtration |
water & solutes forced through membrane or capillary wall by fluid or hydrostatic pressure - not selective |
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ATP is used during movement of particles because substance is |
too large for pores lipid insoluble moving against concentration gradient |
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describe active transport |
- requires a carrier:combines specifically & reversibly with substance - solute pumps move substances AGAINSTconcentration gradients - USES ATP |
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coupled active transports |
- symport: eg:Na+ & amino acids or glucose, Na+,K+,2Cl- cotransporter (secondary) - antiport:eg: Na+/K+ATPase (primary) |
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primary active transport |
potassium in and sodium out (3 na out and 2 k in against conc. gradient) - uses ATP directly |
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what is Secondary active transport |
A method of transport in which the electrochemical potential difference created by pumping ions out of the cell is used to transport molecules across a membrane. |
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what is Exocytosis: |
· secretion of hormones, neurotransmitters,mucus, ejection of wastes · substance is enclosed in a vesicle,vesicle moves to PM, fuses with PM, ruptures,releasing contents outside of cell |
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what is endcytosis? |
· means by which large particles can entercell; also ATP-requiring; energy forvesicle movement · vesicleenclosessubstance; pinches off & moves into cytoplasm where contents are digested |
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what is Receptor mediated endocytosis |
is an endocytotic mechanism in which specific molecules are ingested into the cell - binds to ligands outside of cell |
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what is tonicity |
concentrationof nonpenetrating soluteparticles in a solution |
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what is osmosis |
diffusion of water from high to low concentration |
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- hypertonic |
causes cell to shrink (water out)
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hypotonic |
causes cell to expand (water in) |
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what is Osmolarity: |
total conc of solute particles in a solution |
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3 functional regions of a neuron |
1. Receptive region 2. Conducting region 3. Secretory region |
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what is a neuron cell body? |
- biosynthetic centre - large sperical nucleus + granular cytoplasm- extensive RER and ribosome clusters, lots of golgi to modify and storage, lots of mitochondria |
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what is a tract: |
bundle of nerve processes in CNS |
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what is a nerve: |
bundle of nerve processes in PNS |
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what are dendrites? what do they consist of? |
·short, tapering, branched extensions; usually hundreds/cell body ·enormous SA for reception from other neurons ·conduct impulses toward cellbody · short distance, graded potentials |
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what is an axon? |
- arises from axon hillock - rate of conduction increases with axon diameter - end in axonal terminals - neurotransmittersconvery information from one axon to next - same organelles as cell body – but no nissl bodies - quickly degenerate if cut - increase diameter, increase conduction velocity(myeline will increase the velocity) |
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what is anterograde |
NT from cell body to the axon terminal |
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what is retrograde |
signals going to the cell body (viruses can reach cell body via this transport) |
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what is an axon hillock |
a specialized part of the cell body (or soma) of a neuron that connects to the axon |
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what is a voltage? |
electrical potential energy due to separation of PM or oppositely charged particles (-70mV inside cell) |
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what is resting membrane potential? |
all cells are polarized (-70mv) |
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what ions are outside and inside the neuron? |
- sodium and chloride outside cell,potassium cell inside (negatively charged protein ions inside) |
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At rest: membrane somewhat permeable to K+ but only very slightly permeable to Na+... what happens? |
- net result of permeabilty ofpotassium and sodium = equal - if there areonly potassium channels, resting membrane would be -90mV |
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role of Na & K ATPase pumps |
moves 3 Na OUT for every 2 K+ IN - maintains concentration gradient, maintains resting membrane potential |
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why do we need both NA and K pumps? |
no na pumps would mean -90mv, only na pumps would make it too positive |
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types of Channels in plasma membranes are... |
1. Passive or leakage channels: always open 2. Active or gated channels: signal required to open/close - ion specific |
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chemically-gated channels open due to |
neurotransmitter/hormone |
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voltage-gated channels open due to... |
(change in membrane potential) |
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neurons& muscle cells communicate by changing |
membrane potentials |
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what are the 2 types of signals? |
graded and action potential |
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depolarization ______ the probability of producing nerve impulses; hyperpolarization_______ this probability |
increases, decreases |
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what is a passive channel? |
potassium leakage current, always open, always leaking = results in negative membrane potential |
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what is a gated channel? |
typical closed, but under certain circumstances it will open for brief period of timeand will snap shut – react to neurotransmitters |
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what is a graded potential? describe it |
- short-lived depolarizations or hyper polarizations - current decreases with distance traveledgraded - magnitude determined by strength of stimulus |
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describe the process of a graded potential |
- stimulus depolarizesor hyperpolarizes local area of membrane - movementof ions on either side of membrane propagates signal for short distance |
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what can generate an action potential? |
cells with excitable membrane, and axons - the larger the diameter, the faster the AP |
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what does an action potential entail? |
use voltage gated channels, not limited in distance,all or none, self regenerating - action potentials spreads by a graded potential until the next node of ranvier - action potentials go in one direction becausethe activation gates are closed |
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step by step action potential |
- resting stage (both gates are closed) - both NA gates open (depolarization) then close (start to repolarize) - K permeability increases for a bit (depolarization) - hyperpolarization - k channels open longer than needed |
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what is local depolarization |
voltage gated na channels open |
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what is hyperpolarization |
when the potassium channel stays open for alittle longer than needed, causing it to go more negative |
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when does depolarization occur |
- if the stimulus is strong enough to depolarize cell to -55mv, then action potential will occur |
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what is refractory period |
(cannot be changed) – the depolarization period - - hypderpolarization period is not really refactory – just needs a strong stimulus to trigger AP |
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what is a myelin sheath? |
· white, lipid-protein; insulates/protectsperipheral nerves · increases rate of impulse propagation - made of schwaan cells (fast pain is myelinated) |
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what is a node of ranvier |
space between myelin sheaths, currents are generated here |
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difference between ogliodendrocytes and schwaan cells |
Oligodendrocytes is the insulation of the axons in the CNS of the higher vertebrates, a function performed by Schwann cells in the PNS. - oligo can wrap around 50, schwaan only 1 |
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the synapse includes & 2 diff types of synapse |
- (neuromuscular) junction between 2 neurons or neuron +effector - presynaptic vs postsynapticneuron - electrical and chemical |
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what are electrical Synapses
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- much less common; like gap junctions - direct current flow - protein channels - rapid transmission(electrically-coupled) - neurons can be synchronized ex. eye movements |
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what are chemical synapses |
releaseand binding of neurotransmitters 2 parts: axonal terminal & receptor region - unidirectional |
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Mechanism of Synaptic Communication Initiation: |
1. Ca++ gates open in presynaptic terminal 2. vesicles will merge with the presynaptic membrane and releases neurotransmitters 3. Neurotransmitter binds to postsynaptic receptors 4. Ion channels open in postsynaptic membranes |
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termination of nt (how)? |
(i) degradation by enzymes of postsynaptic membrane (acetylcholinease) (ii) reuptake by presynaptic terminal (norepinephrine) iii) diffusion away from synaptic site (nitric oxide) |
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what is synaptic delay |
time for NT relase, diffusion of it, and receptor binding (0.3-5ms) - rate limiting step |
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2 types of post synaptic potentials |
(i) excitatory postsynaptic potentials (EPSPs) (ii) inhibitory postsynaptic potentials (IPSPs) |
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EPSP: |
a local depolarization of the post synaptic membrane that bring the neuron closer to AP threshold. (Neurotransmitter binding opens chemically gated ion channels, allowin Na and K to pass through simultaneously) - WHAT IS GENERATED IS NOT AN AP |
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IPSP |
a local hyperpolarization of the postsynapticmembrane that drives the neuron away from AP threshold. Neurotransmitter binding opens k or cl channels |
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what is summation |
the addition of EPSPs to influence - determines whether or not an action potential will be triggered by the combined effects |
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2 types of summation |
temporal and spatial |
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temporal summation |
(one or more presynaptic neruons transmitimpulses in rapid fire order) |
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· spatial summation |
2/more stimuli simultaneously come at different locations and add up - IPSP + EPSP can cancel each other out |
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what is cardiac muscle |
- only in heart - striated, involuntary, pacemaker sets rate of contraction - neural input can increase rate |
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what is skeletal muscle |
- attach to & cover bony skeleton - longest muscle fibre - striated, voluntary - can contract rapidly but tires and must rest - strong and adaptable - 40% of body mass |
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what is smooth muscle |
- walls of hollow, visceral organs - nonstriated, involuntary, slow and sustained contractions |
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list the muscle functions |
- generate movement - maintain posture - join stabilization -heat |
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4 characteristics of muscle |
- excitability (receive and respond to stimulus) - contractility (shorten) - extensibility (stretch) - elasticity (resume resting length after stretch) |
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MICROSCOPIC ANATOMY OF A SKELETAL MUSCLEFIBER |
- long, cylindrical cell with many oval nuclei - huge cells - lots of glycogen & myoglobin |
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list the group of muscle fibres from biggest to smallest |
- epimysium (bundles all fascicles) - permysium (bundles fascicles) - fascicle (bundles all muscle fibres) - endomysium/sarcolemma (bundles all muscle fibres) |
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what are sarcomeres |
- extend from one Z disc to the next Z; sarcomeres give this muscle type the name “striated muscle” - a structural unit of a myofibril in striated muscle, consisting of a dark band and the nearer half of each adjacent pale band. |
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types of myofilaments: |
actin: = thin filaments - across I band & partly into A band myosin: = thick filaments - entire width of A band |
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what is a Z disc |
anchors thin filaments & connects all myofibrils of a cell (nebulin, connectin) |
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what is the Hzone: |
area with no thin filaments - thick filaments are present but do not have heads |
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what is the Mline: |
fine strands connecting adjacent thick filaments - in the middle of the h zone |
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properties of thick filaments |
-Myosin head forms cross bridges onceconnected to actin, requires ATP - Has abinding site of for atp - myosin head contains atp |
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properties of thin filaments |
-Small cup on actin that alllows formyosin head attachment -Thin filament consist of g actin, tropomyosin, andtropmonin -Calciumis key for contraction |
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role of troponin and tropomyosin |
-Troponin and tropomyosin precent myosin heads from compleating the power strock, like a safety latch on a gun -Tropomyosin parially blocks the binding sites for myosin during rest. - Contraction is initiated when calcium is present -(together act as the trigger for muscular contraction, bc they respond to increase in calcium) |
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Sarcoplasmic Reticulum:· |
- surrounds each myofibril and is physically separated from the sarcolemma. - stores calcium and releases it |
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what is a sarcolemma |
name of the cell membrane that encloses each muscle cell |
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t-tubules |
- has high sodium levels, open of the sodium channels inside will bepolarized -Ttubles bring extra cellular space and has advantage in large muscle cellsbecause it ensures the depolarization will reach the deep muscle cells -Withoutt tubules, only the superficial filaments are activated |
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what is a triad: |
structure formed by a T tubule with a sarcoplasmic reticulum - part where sr and t tubule meets |
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what lengths get reduced/diminished during muscle contraction? |
- distance between Z discs reduced - I bands shorten - H zones disappear - A bands move closer together, but stay same length (area of thick filaments) |
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how does calcium affect binding? |
- binds to troponin to change shape and to open actin - relaxation occurs with sr claims calcium back |
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what is the motor end plate? |
the muscle side receiving stimulation |
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what is a neuromuscular junction consist of? |
motor end plate and axon terminal w/ synaptic cleft |
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What is excitation-contraction coupling |
process of converting an electrical stimulus to a mechanical response. |
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what is an action potential |
an impulse along the membrane of a muscle cell or nerve cell. |
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what is a latent period |
-Latent period is the time the calcium needs to be released and diffused to tropomyosin and troponin |
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what is a motor unit |
1 motor neuron+ all muscle fibers it supplies |
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what allows for finer movements? (i.e. movements of fingers) |
-We have a lot motor units will allow us to do fine movements - The more discreet we want a muscle activity to preform the moremotor neurons |
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• 2 types of graded responses: |
1) change speed of stimulation 2) change # of motor units activated - Increase contraction of muscle by increasing the firing rate of the stimulation - Continuous contraction will require high frequency - Increase number of motor neurons + increase high frequency stimulation = continuos muscle movement |
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Slow oxidative fibers: |
thin cells with slow-acting myosin ATPases - - contract slowly (red = lots of myoglobin); primary energy fuel is fat • lots of mitos, capillaries, aerobic enzymes: oxidative • fatigue-resistant, but not powerful |
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Fast glycolytic fibers: |
large, pale (white), little myoglobin & diameter 2x that of slow oxidative fibers; fast-acting myosin ATPases • few mitochondria; lots of glycogen reserves: glycolytic • will fatigue because anaerobic |
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Fast oxidative fibers: |
red or pink, intermediate cell size; fast-acting myosin ATPases & contract quickly; high myoglobin content & O2-dependent; fairly fatigue-resistant |
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what is MuscleF atigue |
- state of physiological inability to contract; results from a relative deficit of ATP • contributors: build-up of lactic acid, ion imbalances |
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anaerobic threshold: |
point at which muscle converts to anaerobic |
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what is oxygen debt |
- extra amount of oxygen needed to be taken in to accomplish theabove (lactic acid indirectly stimulates respiratory centre of brain) - muscles need oxygen to recover metabolic fatigue - new term is excess post-exercise oxygen consumption |
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what happens after oxygen debt? |
• post exercise need to: replenish O2 reserves, convert lactic acid to pyruvic acid, replace glycogen stores, restock ATP & CP • liver converts additional lactic acid to glucose/glycogen (Cori cycle) |
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what is the speed of contraction determined by? |
- determined by the iso forms of myosin present in the thick filaments - isoformes have diff ATPase activty |
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what is contraction duration determined by |
- according to fibre type - dependent on the rate of ca removal |
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ATP from creatine phosphate (describe process) |
- phosphate group on creatine phosphate directly phosphorylates adp to atp - creatine kinase (enzyme used) - creatine stored in muscles |
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ATP from anaerobic respiration |
- glycogen in muscle turns into glucose - undergoes glycolysis to create 2 atp - 2 pyruvic acid = lactic acid into blood |
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ATP from aerobic respiration |
- uses stored energy (pyruvic acid, fatty acids, amino acids, glucose) - go through mitochondria - produce 36 atp, co2, h2o and heat |
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stored atp in muscle is used when? |
4-6 secs only |
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what is unfused tetanus? |
partial relaxation between stimulus (so there is a wave) - muscle contraction is quivery |
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what is fused tetanus? |
high stimulus frequencies = no relaxation between stimuli |
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what is tetanus? |
fused contractions - inter-stimulusinterval too short to allow inter-twitch muscle relaxation - eventually followed by muscle fatigue |
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what is maximal stimulus: |
strongest stimulus that produces an increase in contractile force (more motor units recruited) - smallest motor units controlled by most excitable neurons - more intense stimulation recruits larger motor units |
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what is muscle tone |
even relaxed muscle a bit contracted (tone) due to spinal reflexes activated by stretch receptors |
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what are isotonic contractions?: |
muscle changes in length & moves load |
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what are isometric contractions? |
tension increases but muscle remains samelength |
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concentric and eccentric ? |
- concentric (contracting) - eccentric (lengthening of muscle) |
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Velocity & Duration of Contraction depends on: |
1) Load: greater load = longer latent period = slower contraction = shorter contraction duration |
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arrangement of fibres in smooth muscle cells |
- small spindle fibres (only one centrally located nucleus) - no NMJ, but varicosities - nt releases to synaptic cleft (diffuse junctions) -The form together in sheets -Varicosties –the axon in the case fro the autonomitc fibre will branch exensively over thesmooth muscle and will release neurotransmitters but there’s not motor endplate -Caneither be sympathetic or parasympathetic |
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properties of smooth muscle |
• SR less developed than in skeletal muscle; no T tubules; but SR touches sarcolemma & smooth muscle cells have large SA/volume ratio• no striations, but do have interdigitating thick & thinfilaments: 1) a lot of thin filaments 2) tropomyosin but no troponin (calmodulin instead) 3) no sarcomeres: thick & thinfilaments spiral down smooth muscle cell 4) noncontractile intermediate filaments & dense bodies (attach to thin filaments) -No t tubules, the SR is found very close to the plasmamembrane of the muscle cell - (all cells are connectedso that they move together) |
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Contractionof Smooth MuscleMechanism: |
electrical coupling via gap junctions -slow, synchronized contractions • some smooth muscle cells are pacemaker cells • contraction of smooth muscle is slow(30x), sustained, fatigue-resistant • few mitos; most ATP generated aerobically |
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Contraction of Smooth Muscle steps: |
1) actin & myosin interact by slidingfilament mechanism 2) final trigger is rise in intracellular Ca++ 3) sliding process is energized by ATP |
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Special features of smooth muscle contraction |
- response to stretch - length and tension changes - hyperplasia (the enlargement of an organ or tissuecaused by an increase in the reproduction rate of its cells - cancer) - secretory functions |
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Single-unit(unitary) smooth muscle: |
visceral muscle; more common 1) contracts as a unit & rhythmically 2) electrically coupled by gap junctions 3) often spontaneous action potentials 4) all other smooth muscle characteristics |
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Multiunitsmooth muscle: |
• eg: large airways to lungs, large arteries, arrector pili muscles of skin hair follicles, internal eye muscles for focus 1) gap junctions, spontaneous, synchronized depolarizations rare 2) muscle fibers structurally independent of each other 3) richly supplied with nerve endings, each forms a motor unit with a number of muscle fibers 4) responds to neural stimulation with graded contractions (still regulated by autonomic ns, hormones) |
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what is a ganglion |
a structure containing a number of nerve cell bodies |
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what is a connexon |
an assembly of six proteins called connexins that form the pore for a gap junction between the cytoplasm of two adjacent cel |
