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3 types of muscle
1. skeletal
2. cardiac
3. smooth
4 possible functions of muscle contraction.
1. body movement
2. stabilization of body position
3. movement of substances through the body
4. generating heat to maintain body temperature
skeletal muscle
  • voluntary
  • connects one bone to another
  • muscle attached to bone by ligament (tendon connects muscle to bone, ligament connects bone to bone)
  • like many cell types, muscle cells are so specialized they lost ability to undergo mitosis
muscles work in groups
  • agonist: muscle responsible for movement - contracts
  • antagonist: second muscle - stretches (when antagonist contracts, muscle moves in opposite direction)
in addition to antagonistic muscles, there are synergistic muscles
assist agonist by stabilizing origin bone or positioning insertion bone during movement.
sarcomere
  • functional unit of skeletal muscle
  • composed of many thick and thin filament
  • sarcoplasmic reticulum (specialized ER of msucle cell)
  • skeletal muscle is multinucleate
  • modified membrane called sarcolemma
  • thick filament: made up of myosin
  • thin filament: composed of actin

[!] in muscle contraction, H zone and I band get smaller, while the A band does not change size!
5 stage cycle
  • myosin and actin work together
  • in presence of Ca2+ ions, active site exposed allowed myosin head to bind to actin
muscle contraction
  • begins with action potential
  • neuron attaches to muscle cell --> forming neuromuscular synapse
  • action potential releases acetylcholine (activates ion channels in sarcolemma creating action potential)
  • action potential moves deep into muscle cell via T-tubules (small tunnels in membrane) - allow for uniform contraction of muscle by allowing action potential to spread through muscle cell rapidly
  • action potential transferred to sarcoplasmic reticulum, which suddenyl becomes permeable to Ca2+ ions. --> beginning 5 stage cycle
  • at end of each cycle Ca2+ pumped back into sarc. reticulum
myoglobin
  • gives type1/slow twitch muscle fibers red color
  • stores oxygen inside muscle cells
  • but has only 1 protein subunit
  • stores only 1 molecule of oxygen
cardiac muscle
  • striated (composed of sarcomeres)
  • each cardiac muscle cell contains only one nucleus
  • separated from neighbor by intercalated disc (contain gap junction allowing action potential to spread from cardiac cell to cell)
  • involuntary
  • forms a net, isnt connected to bone
smooth muscle
  • involuntary
  • innervated by autonomic nervous system
  • like cardiac, contains only one nucleus
  • also contain thick and thin filaments (but not organized into sarcomeres)
  • contain intermediate filaments attached to dense bodies
compact bone
  • surrounds medullary cavity which holds yellow bone marrow (contains adipose cells for fat storage)
spongy bone
  • contains red bone marrow
bone
  • living tissue
functions:
  • support of soft tissue
  • protection
  • movement
  • mineral storage
  • blood cell production
  • energy storage (adipose cells in bone marrow)
4 types of cells surrounded by matrix:
  • osteoprogenitor
  • osteoblast - secrete collagen and organic compouns which form bone. incapable of mitosis.
  • osteocytes - incapable of mitosis. exchange nutrients and waste materials with blood.
  • osteoclasts - resorb bone matrix, release minerals back into blood. may develop from monocytes (WBC)
Haversian (central) canals
osteoclasts burrow tunnels (Haversian cannals) through compact bone.

contain blood and lymph vessels and are connected by Volkmann's canals.
lamellae
osteoblasts lay down new matrix into tunnel walls forming rings called lamellae

osteocytes trapped between lamellae exchange nutrients via canaliculi
osteon (Haversian system)
entire system of lamellae and Haversian canal
most Ca2+ in the body is stored in the bone matrix as hydroxyapatite
cartilage
  • flexible, resilient connective tissue
  • composed of collagen
  • great tensile strength
  • no blood vessels or nerves except in outside membrane
joints
important functions of the skin

1. Thermoregulation: regulate body temp. sweat/radiation to get rid of heat, blood shunted away from capillaries to reduce heat loss, erected hairs. both warmth and cold receptors.
2. Protection: physical barrier to abrasion, bacteria, dehydration, chemicals, UV radiation
3. Environmental sensory input: gathers info from environ. by sensing temperature, pressure, pain, touch
4. Excretion: water and salts excreted through skin by diffusion.
5. Immunity
6. Blood reservoir: vessels in dermis hold up to 10% of blood
7. Vitamin D synthesis: UV radiation activates molecule in skin --> vitamin D
callus
exposure to friction or pressure stimulates epidermis to thicken, forming callus
epidermis
  • avascular (no blood vessels)
dermis
  • connective tissue derived from mesodermal cells
  • blood vessels, nerves, glands, hair follicles
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