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MCAT BIology > Muscle, Bone, and Skin > Flashcards

Muscle, Bone, and Skin Flashcards

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0
Q

Possible functions of muscle contraction

A
  1. Body movement
  2. Stabilization of body position
  3. Thermoregulation by heat generation
  4. Movement of substances across body
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1
Q

Types of muscle

A

Skeletal
Cardiac
Smooth

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2
Q

Origin of muscle

A

Muscle’s point of attachment at the LARGER bone of a pair of bones that works together to execute motion

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3
Q

Insertion point of muscle

A

Muscle’s point of attachment at the SMALLER of two bones. Muscle may apply energy to move the smaller bone relative to the larger bone upon contraction

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4
Q

Tendons

A

Fibers that connect muscle to bone

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5
Q

Ligaments

A

Fibers that connect bones to bones

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6
Q

Agonist

A

Muscle that contracts to initiate movement

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7
Q

Antagonist

A

Muscle that stretches simultaneous to the contraction, opposing the agonist’s motion

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8
Q

Synergistic muscles

A

Assist agonist muscles by stabilizing the origin or positioning the insertion bone

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9
Q

Muscle organization–components breakdown

A

Sarcomere (basic unit) —made of thick and thin filaments
Myofibril— many sarcomeres stacked end to end in cylindrical fibers
Muscle cells—sarcolemma membrane wraps around multiple myofribrils, sarcoplasmic reticulum, nuclei, mitochondria
Fasciculus—- many bundled muscle fibers
Muscle—- made up of many fasciculae

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10
Q

5 Stage Cycle of Thin/Thick Filament motion

A
  1. Troponin/tropomyosin covers binding sites on actin || myosin is bound to ADP+P, in the ready-to-bind position
  2. Presence of Ca2+ removes Troponin/tropomyosin complex, opening up binding sites for myosin
  3. Myosin releases ADP+P and shortens, dragging the thin filaments with it (aka POWER STROKE)
  4. ATP binds to myosin, forcing it out of the binding sites bc no longer proper conformation so less affinity || Troponin/tropomyosin come back to bind
  5. ATP breaks down into ADP+P, still bound to the myosin so it’s in the ready position and cycle can start all over again
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11
Q

Motor Unit

A

Consists of neuron and muscle fibers it innervates || the number, size, and frequency of APs of motor units recruited determine amount of force per contraction

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12
Q

Myoglobin

A

Looks like one subunit of hemoglobin, can only store one molecule of O2

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13
Q

Types of Skeletal Muscle Fibers

A
  1. Type I : slow oxidative || slow twitch fibers || look red bc lots of myoglobin, many mitochondria, slow rate of energy output, slow rate of fatigue
  2. Type IIA : fast oxidative || look red bc myoglobin! faster rate energy output, faster rate fatigue
  3. Type IIB: fast glycolytic || look white bc little myoglobin! fast contractions, very fast fatigue rate, breaks down glycogen
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14
Q

Muscle Growth by hypertrophy v. Mitosis

A

Hypertrophy: increase in diameter of muscle cell, increase amount mitochondria and sarcomeres, lengthened sarcomeres — changes occur over time as muscles exposed to forceful and repetitive contractions

Muscles cannot grow by mitosis, like most other tissues

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15
Q

Cardiac Muscle Characteristics

A 
Single nucleus
Involuntary
Striated (due to presence of sarcomeres)
Intercalated discs, gap junctions
Action potentials plateau due to slow voltage gated Ca channels---plateau length determines time of contraction
16
Q

Smooth Muscle Characteristics

A

Single nucleus
Involuntary
Not organized into sarcomeres–instead, have thick, thin, and intermediate filaments connected to dense bodies
Innervate by autonomic system
Responds to pH, CO2, and hormones as well

17
Q

Smooth muscle – single unit structure and where are they found

A

Group of muscle fibers/cells innervates by single neuron
Transmit impulse through gap junctions and multiple cells contract together
Found in: small arteries and veins, intestines, urinary bladder, uterus, stomach

18
Q

Smooth muscle—multiunit structure and where can they be found

A

Each cell innervates by single neuron, independent contractions
Found in: bronchioles, iris, large arteries

19
Q

Vagus nerve

A

Parasympathetic nerve that innervates SA node of heart

Tonically slows down the SA node’s default setting contraction (100bpm) to resting heart rate

20
Q

Bone Functions

A
  1. Blood cell production
  2. Energy storage in adipose tissue in bone marrow
  3. Body movement
  4. Internal organ protection
  5. Support soft tissue
  6. Mineral storage
21
Q

Bone Cell Types

A
  1. Osteoprogenitors || differentiate into osteoblasts
  2. Osteoblasts || don’t undergo mitosis, secrete collagen and other materials to build bone matrix, get encased in the matrix and differentiate into osteocytes
  3. Osteocytes || don’t undergo mitosis! exchange nutrients and waste with bloodstream
  4. Osteoclasts || develop from monocytes (a kind of white blood cell), resorb bone (degrade the matrix) to release minerals into bloodstream
22
Q

Hemopoeisis and where it happens

A

Blood cell production

Occurs in spongy bone (which contains red bone marrow) encased within the epiphyseal portion of long bone

23
Q

Generic Long Bone Structure (surface)

A

Diaphysis: shaft with two ends
Epiphysis: further most ends of the diaphysis
Metaphysis: section sandwiched between epiphysis and diaphysis

24
Q

Epiphysis

A

Contains spongy bone, which contains red bone marrow. Site of hemapoeisis

25
Q

Metaphysis

A

Contains cartilage, site of long bone growth (elongation)

26
Q

Diaphysis

A

Made of compact bone, contains medullary cavity inside (yellow bone marrow, site of energy storage within adipose tissue)

27
Q

Generic Long Bone Structure (inner)

A
  • Haversian canals (made by osteoclasts) house blood vessels and are composed of concentric circular layers called LAMELLAE
  • Osteocytes (used to be osteoblasts) are trapped between lamellae sheets
  • Volkmann canals run perpendicular to Haversian canals and also house blood vessels
28
Q

Canaliculi

A

Channels in osteoblasts that facilitate exchange of nutrients and waste once the osteoblasts have been trapped between lamellae

29
Q

Osteon (Haversian system)

A

Name describing bone organization in terms of lamellae and canals

30
Q

Ca2+ , Bones, Homeostasis

A

|| Ca2+ slightly soluble, plasma: mostly bound to proteins
|| bone storage forms: hydroxyapatite crystals (compressive strength)
: CaHPO4 salts (buffer plasma Ca2+ concentration)

31
Q

Disrupted Free Calcium Ion Homeostasis Effects

A

Too much || cell membrane hypoexcitability, leads to memory loss! fatigue, lethargy

Too little || cramps, convulsions

32
Q

Types of cartilage

A
  1. Hyaline (reduces friction and absorbs shock)
  2. Fibrocartilage
  3. Elastic
33
Q

Cartilage characteristics

A

Made of collagen (primarily)
Tensile strength, flexible
No vasculature except in outer membrane (perichordium)

34
Q

Types of Joints

A
  1. Fibrous joints || bones tightly connected by fibrous tissue! little or no movement between the bones (skull bones, teeth to mandible)
  2. Cartilaginous joints || bones connected by cartilage, also few degrees of freedom (ribs to sternum)
  3. Synovial joints || bones not directly connected to cartilage, instead separated by capsule filled with synovial fluid (provides nourishment, lubrication to cartilage | contains phagocytotic cells to protect from microbes and particles that result from wear and tear.) | allow for wide rename of motion
35
Q

Skin Functions

A
  1. Thermoregulation || too hot: blood conducts heat away from core and to skin, to dissipate through sweat evaporation or radiation | too cold: blood stays near core to keep body warm, piloerection (via sympathetic stimulation) keeps insulating air trapped near the skin
  2. Excretion || not sweat, insensible water loss
  3. Vitamin D production || UV rays activate precursor in the skin
  4. Immunity
  5. Protection || physical barrier
  6. Sensory inputs
  7. Blood reservoir
36
Q

Epidermis (characteristics and cell types)

A
    • avascular
    • five layers
      1. Keratinocytes || 90% of skin, keratin makes skin waterproof
      2. Melanocytes || melanin! pigment protein
      3. Merkel cells || provide touch information to nervous system
      4. Langerhans cells || part of immune system! interact with helper T cells

MCAT BIology (4 decks)

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