zoo 14 le2

• Movement


  • A key characteristic in animals
  • An act of changing location or position
  • Can be at the molecular, cellular, tissue or organismic level
• Types of Movements in Animals


  • Non-muscular movement
  • Muscular movement
• Non-muscular movement


  • Amoeboid movement
  • Ciliary movement
  • Flagellar movement
• Muscular movement


  Use of skeletal muscles, smooth muscles or cardiac muscles for movement
• Amoeboid movement in protozoans


  • Uses pseudopodia (singular: pseudopodium) or false feet
  • Purposes: Capture food, Glide across surface, Escape danger
• Movement of amoeboid protozoan


  1. Portion of its ectoplasm is transformed into a gel and its endoplasm flows into this direction

  2. The cell membrane expands forming a pseudopodium that pushes forward

  3. When the endoplasm reaches the tip of the pseudopodium it is converted into a sol (ectoplasm)
• Amoeboid protozoans

  • Entamoeba histolytica
  • Naegleria fowleri
• Amoeboid movement in animals

  • Leukocytes like neutrophil, eosinophil and monocyte respond to chemicals released from site of infection or tissue injury
  • This response is known as chemotaxis
• Amoeboid movement of leukocytes in animals


  1. Diapedesis is the movement into and out of blood vessel wall

  2. Leukocyte moves by amoeboid motion

  
• Amoeboid movement of macrophages


  • A monocyte transforms into a macrophage outside blood vessels
  • A macrophage can "move" about tissue spaces
  • When macrophage encounters a pathogen like bacteria, it extends portions of its cytoplasm around the bacterium to enclose it in a vacuole called phagosome for digestion
  • This process is called phagocytosis

  
• Cilium (plural: cilia)

  • 1-10 µm long and less than 1 µm wide
  • Hair-like structure
  • Each cilium has a microtubule backbone characterized by '9+2' architecture
  • Function: used to move an entire cell or substance along the outer surface of a cell

  
• Ciliary movement in protozoans

  • Balantidium coli

  
• Ciliary movement in invertebrates


  • Gill filaments of molluscs - beat to drive water through the mantle cavity or clean gills
  • Tube feet of echinoderms - at inner surface of the tube feet; help circulate water
• Ciliary movement in vertebrates


  • Respiratory tract - for transport of mucous = mucociliary clearance
  • lining of the inner wall of Female fallopian tube - move egg cell or ovum
• • Smoking, vaping or air pollutants destroy cilia along the respiratory tract
  • Mucous with trapped dirt and chemicals clog the airways
  • These eventually cause damage and infections
• Flagellum


  • A whip-like appendage used for locomotion
  • With pair of central microtubules surrounded with nine fused pairs of protein microtubules
  • With side arms of motor molecule dynein that originate from the centriole
• Flagellar movement in animals

  • Sperm cell - move up the female reproductive tract
• Muscular movement

  • Movement in animals is possible because of striated muscles or smooth muscles
  • Invertebrates have smooth muscles
  • Vertebrates possess both striated and smooth muscles
• Types of Muscles in Vertebrates


  • Skeletal muscle
  • Cardiac muscle
  • Smooth muscle
• Skeletal muscle

  • Structural unit is muscle fiber
  • Attached to bone/cartilage
  • Voluntary control through the somatic nervous system
• Cardiac muscle

  • Structural unit is muscle fiber
  • Not attached to bone/cartilage
  • Involuntary control through sinoatrial node or cardiac pacemaker and autonomic nervous system
• Smooth muscle

  • Structural unit is muscle fiber
  • Not attached to bone/cartilage
  • Involuntary control through autonomic nervous system
• Skeletal muscle organ

  • Attached to bone through a tendon
  • Enclosed by epimysium, a connective tissue
  • Contains bundles of skeletal muscle fibers
  • Each bundle is enclosed by perimysium, a connective tissue
  • Each skeletal muscle fiber is enclosed by endomysium, a connective tissue
• Skeletal muscle fiber


  • Contains myofibrils
  • Contains myofilaments
  • Types of myofilaments: thin actin, thick myosin
  • Arrangement of actin and myosin forms the striation
• Sarcomere


  • Structural unit of a muscle fiber
  • Extends between two Z lines or Z discs
  • Has dark A band and light I band
• Myosin


  • Thick myofilament forming the dark A band
  • Anchored at the M line at middle of the sarcomere
• Actin


  • Thin myofilament forming the light I band
  • Anchored at the Z disc
  • Extends into the A band towards the M line and overlaps with myosin
• H zone


  At the middle of the A band without actin
• Troponin and Tropomyosin


  • Regulatory proteins blocking interaction between myosin and actin
  • Tropomyosin covers myosin-binding sites in actin
  • Troponin binds to tropomyosin
• Neuromuscular junction


  Formed by the nerve fiber and the muscle it innervates
• Sliding Filament Theory of Muscle Contraction


  1. During muscle contraction, myosin binds to actin and pulls actin towards the center of the sarcomere

  2. Actin "slide" over myosin

  3. Results to shortening of the sarcomere, with compression of I and H bands

  4. Length of A band remains the same during shortening of the sarcomere because length of the myofilaments do not change
• Resting Membrane Potential


  • Result of difference in the concentration of ions inside and outside the cell
  • Difference in the number of potassium ions (K+) across the cell membrane dominates the resting membrane potential
  • All voltage-gated sodium ion (Na+) channels and some voltage-gated potassium ion (K+) channels are closed
  • The Na+/K+ transporter pumps K+ into the cell and Na+ out of the cell
• Action Potential


  • A change in the resting membrane potential as a result of depolarization and repolarization
  • Results to an electrical impulse travelling along the length of the cell membrane
• Action Potential: Depolarization


  1. Some sodium channels open causing Na+ ions to enter the cell

  2. Cytoplasm becomes less negative

  3. Results to depolarization where electrical charge across the membrane is reduced (lessens)

  4. All Na+ channels open when the threshold of excitation is reached
• Action Potential: Repolarization


  1. Voltage-gated Na+ channels slowly close while voltage-gated K+ channels open

  2. Results to movement of K+ from the cytoplasm to the extracellular medium

  3. Potential across the plasma membrane becomes less negative resulting to repolarization
• Action Potential: Hyperpolarization


  1. Results from K+ continually leaving the cell

  2. Na+ channels are still closed

  3. K+ continue to leave the cell

  4. Membrane potential becomes more negative than its resting potential

  5. Cell membrane in a refractory state and cannot fire

  6. Stops when K+ channels close
• Muscle Fiber Activation


  1. Impulse (action potential) from the brain or spinal cord travels along the neuron's axon to the neuromuscular junction

  2. Upon reaching axon terminal, it stimulates release of synaptic vesicles containing the neurotransmitter acetylcholine (ACh)

  3. ACh is released into the synaptic cleft, a space between the axon and the skeletal muscle cell's plasma membrane

  4. ACh then binds to acetylcholine receptors on the surface of the membrane

  5. Binding of acetylcholine generates action potential that travels along T tubules of the skeletal muscle fiber

  6. Stimulates release of calcium ions (Ca2+) from the sarcoplasmic reticulum to the cytoplasm

  7. Ca2+ binds to troponin, which shifts tropomyosin to expose myosin-binding sites in actin

  8. Results to myosin head binding to actin

  9. Binding of myosin and actin allows myosin to pull actin towards the center of sarcomere at the expense of one ATP

  10. Results to shortening of the muscle fiber (contraction)

  11. When impulse from neuron stops, acetylcholinesterase removes ACh at the synaptic cleft

  12. Results to Ca2+ being moved back into the sarcoplasmic reticulum

  13. Without Ca2+ binding to troponin, troponin and tropomyosin shift back covering myosin-binding sites on actin

  14. Actin is released from binding to myosin head, the sarcomere goes back to its original length (relaxation)
• Cardiac muscle cell


  • Striated
  • With one nucleus
  • Branching
  • Connected to each other through an intercalated disc
• Sinoatrial node


  Pacemaker that initiates cardiac muscle contraction
• Smooth muscle cell


  • Spindle-shaped
  • With one nucleus per cell
  • Not striated