SNS Biology - Muscles and Locomotion Flashcards Preview

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Flashcards in SNS Biology - Muscles and Locomotion Deck (27):
1


Locomotion

Unicellular

  • Protozoans and algae - cilia or flagella
  • Amoebae - pseudopodia

2

Cilia and Flagella

  • Same structure for all eukaryotic cells
  • Consist of cylindrical stalk of 11 microtubules - 9 paired around circumference, 2 single microtubules in the centre
  • Flagella acheive movement via power stroke - thrusting movement generated by sliding action of microtubules
  • Return of cilia or flagella to starting position called the recovery stroke

3

Pseudopodia

Forward extension of the cell membrane, allowing the cell to move

4


Locomotion

Invertebrates

 

  1. Hydrostatic Skeletons:

    Flatworms

    Segmented worms (annelids)

  2. Exoskeleton

5


Locomotion

Invertebrates

Hydrostatic Skeletons

Flatworms

  • Muscles arranged in circular and longitudinal layers.
  • Contract against the resistance of incompressible fluid within the tissues (the hydrostatic skeleton)
  • Contraction of the circular layer causes incompressible fluid to flow longitudinally lengthening the animal
  • Contraction of the longitudinal layer shortens the animal

6


Locomotion

Invertebrates

Hydrostatic Skeletons

Annelids

  • Same as for flatworms
  • ach segment can expand or contract independently

7


Locomotion

Exoskeleton

  • Found principally in arthropods (eg insects)
  • Insect exoskeletons composed of chitin
  • All exoskeletons composed of noncellular material secreted by the epidermis
  • Limit growth, must be shed periodically and new skeleton deposited to permit growth

8


Vertebrate Skeleton

Cartilage

  • Connective tissue
  • Softer and more flexible than bone
  • Retained in adults where firmness and flexibility are necessary, for example the external ear, nose, laryngeal and tracheal walls, skeletal joints

9


Vertebrate Skeleton

Bone

  • Mineralised connective tissue
  • Has ability to withstand stress and provide body support
  • Two types:
  1. Compact - dense. Deposted in osteons or Haversian systems (structural units) consisting of a central Haversian canal surrounded by concentric circles of bony matrix (calcium phosphate) called lamellae
  2. Spongy - much less dense. Consists of interconnecting lattice of trabeculae (bony spicules). Cavities between them are filled with yellow and/or red bone marrow. Yellow marrow is inactive and infilrated by adipose tissue. Red marrow is involved in blood cell formation

10


Vertebrate Skeleton

Bone

Osteocytes

Two types

  1. Osteoblasts - synthesise and secrete organic constituents of bone matrix. Once surrounded by bone matrix mature into osteocytes
  2. Osteoclasts - large, multinucleated cells. Involved in bone resorption

11


Vertebrate Skeleton

Bone

Formation

  1. Endochondral Ossification - eg long bones
  2. Intermembraneous - mesenchymal (undifferentiated) connective tissue transformed into bone

12



Vertebrate Skeleton

Bone

1. Axial Skeleton

2. Appendicular Skeleton

  1. Basic framework of body. Consists of vertebral column, skull, rib cage. Point of attachment for the appendicular skeleton
  2. Includes bones of appendages and pectoral and pelvic girdles

13



Vertebrate Skeleton

Bone

1. Ligaments

2. Tendons

  1. Bone to bone connectors
  2. Attach muscle to bone and bend the skeleton at moveable joints

14


Muscle

Innervation

1. Skeletal Muscle

2. Cardial Muscle

3. Smooth Muscle

  1. Somatic nervous system
  2. Autonomic nervous system
  3. Autonomic Nervous system

15


Muscle

Appearance

1. Skeletal

2. Cardiac

3. Smooth

  1. Multinucleated, striated, formed from the fusion of several mononucleated embryonic cells, abundant mitochondria
  2. Single central nucleus, lack striations
  3. Striated, one or two centrally located nuclei

16



Vertebrate Skeleton

Muscle

Skeletal

Structure

  • Muscle fibres composed of sarcolemma and parallel bundles of myofibrils, each surrounded by sarcoplasmic reticulum
  • Sarcolemma is connected to T-tubules which provide channels for ion flow throughout the muscle fibres and can propagate the AP

17



Vertebrate Skeleton

Muscle

Skeletal

Structure

Sarcoplasmic Reticulum

  • Modified endoplasmic reticulum
  • Envelops myofibrils, stores Ca2+

18



Vertebrate Skeleton

Muscle

Skeletal

Structure

1. Sarcoplasm

2. Sarcolemma

  1. Cytoplasm of a muscle fibre
  2. Muscle fibre cell membrane. Capable of propagating an AP. COntains T-tubules

19


Vertebrate Skeleton

Muscle

Skeletal

Structure

The Sarcomere

Composed of thin and thick filaments composed of actin and myosin filaments respectively

  1. Z lines define border of a single sarcomere and anchor the thin filaments
  2. M line runs down the centre of the sarcomere
  3. I band is region containing thin filaments only
  4. H zone is the region containing thick filaments only
  5. A band spans entire length of the thick filaments and includes regions in which overlap with thin filaments

During contraction A band isn't reduced in size, H and I are

20



Vertebrate Skeleton

Muscle

Skeletal

Contraction

  • Stimulated by somatic NS via motor neurons
  • NT released from presynaptic boutons at NMJ and stimulate postsynaptic receptors
  • If sufficient stimulation, permeability of sarcolemma altered, AP generated
  • AP is conducted along the sarcolemma and T-system into the interior of the muscle fibre
  • Causes release of Ca2+ from the sarcoplasmic reticulum into the sarcoplasm
  • Ca2+ bind to tropomyosin allowing actin and myosin to slide past each other and the sarcomere to contract

21



Vertebrate Skeleton

Muscle

Skeletal

Simple Twitch

  • Response of a single muscle fibre to a brief supra-threshold stimulus
  • Consists of
  1. Latent period - time between stimulation and onset of contraction. AP spreads along the sarcolemma, Ca2+ released into sarcoplasm
  2. Contraction period
  3. Relaxation period - muscle briefly unresponsive to stimuli (absolute refractory period)

22



Vertebrate Skeleton

Muscle

Skeletal

Summation

  • When muscle fibres exposed to a very frequent stimulus, muscle cannot fully relax
  • Contractions begin to combine - temporal summation
  • Become stronger and more prolonged

23


Vertebrate Skeleton

Muscle

Skeletal

Tetanus

  • Continuous contractions of muscle fibres upon high frequency stimulation
  • Stronger than simple twitch of a single fibre
  • If maintained, muscle will eventually fatigue and contraction will weaken

24


Vertebrate Skeleton

Muscle

Skeletal

Tonus

  • State of partial contraction
  • Muscles never completely relaxed and maintain partially contracted state

25


Vertebrate Skeleton

Muscle

Cardiac

  • Possess characteristics of both smooth and skeletal muscle fibres
  • As for skeletal muscle, actin and myosine filaments arranged into sarcomeres, giving striated appearance
  • Controlled primarily for ANS

26


Vertebrate Skeleton

Muscle

Smooth

 

  • Rensponisble for involuntary muscle contraction
  • Innervated by ANS
  • Found in GI tract, bladder, uterus and BV walls for example
  • Lacks striations

27



Vertebrate Skeleton

Muscle

Energy Reserves

  1. Creatine Phosphate - in vertebrates and some invertebrates, energy can be temporarily stored in this high-energy compound
  2. Arginine Phosphate - similar to above. Utilised by invertebrates
  3. Myoglobin - haemoglobin-like protein. Has high O2 affinity and maintains supply in muscles. Can subsequently be used to generate ATP via cellular respiration

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