Lecture 14

Question 1

Pariapulid worms (3)

Answer 1

marine, known since Cambrian period, found in BC

Question 2

What is Nematomorpha? (4)

Answer 2

parasitic larvae, can reach 2 m long, adults are free-living, horsehair worms

Question 3

Loricifera (3)

Answer 3

very small, live in marine sediments, found in 1980s

Question 4

Tradigrades

Answer 4

“water bear”, survive in extreme temperature

Question 5

Onychophora

Answer 5

“velvet worm”, paralyze the prey

Question 6

Arthropods are the most diverse eukaryotic group (4)

Answer 6

1. Beetles
2. Crustaceans
3. Spiders
4. insects

Question 7

Diversity Examples - Arthropods (5)

Answer 7

1. Myriapodes
2. Scorpian
3. Sea spider
4. Amphipode
5. Scolopendra

Question 8

Insects - Dysticus

Answer 8

predaceous diving beetle, adult collect air under wings and use this to breathe underwater

Question 9

Honey bees

Answer 9

highly complex social life - worker bees dance to communicate

Question 10

Characteristics - Arthropods (4)

Answer 10

1. largest eukaryotic group
2. very abundant
3. Grouped segments
4. Jointed appendages for specialized function (rigid exoskeleton)

Question 11

Tagmata

Answer 11

grouped segments, specialized body region

ex. Cephalothorax and abdomen (crayfish)

Question 12

Rigid exoskeleton (6) 
(made of? secreted by? covers? alive? process?)

Answer 12

• grow by moulting
• non-living
• secreted by epidermis
• covers all external surfaces, digestive tract & trachea
• composed of layers
• Chitin, protein + CaCO3

Question 13

Discontinous growth

Answer 13

mass grows continuously but size grows in stepwise

Question 14

Types of Skeleton (3) Examples within each one

Answer 14

1. Hydrostatic skeleton (ex. cnidarian, worms, shell-less mollusks)
2. Exoskeleton (Ex. shelled mollusks, arthropods)
3. Endoskeleton (Ex. Echinoderms, vertebrates)

Question 15

Skeleton muscles - Arthropods (3)

Answer 15

muscles within appendage

• need a resistor to act against (like a skeleton)
• are often found in antagonist pair, act in opposite direction, muscle can only pull not push

Question 16

What is muscle organ and muscle fibre?

Answer 16

muscle organ: muscle tissues and connective tissue

A muscle fibre is a multinucleated cells that contain many myofibrils

Question 17

Myofibrils (muscle)

Answer 17

• composed of protein bundles
  (actin - thin, myosin thick)
• myofibrils make up the sacromere

Question 18

Sarcomere

Answer 18

contractile unit of muscle fibres

Question 19

Motor neuron

Answer 19

• motor neuron spikes drive muscle contractions at neuromuscular junction

Question 20

What is neuromuscular junction?

Answer 20

• synapse between the motor neuron and the muscle fibre

Question 21

What happens when spike reaches neuromuscular junction?

Answer 21

1. Action potential reaches synapse (neuromuscular junction) Voltage-gated Ca+++ channels open and Ca++ flow into presynaptic terminal
2. Increased concentration of Ca++ leads to the fusion of synaptic vesicles containing neurotransmitter with presynaptic membrane (neurotransmitter at neuromuscular junction is acetylcholine)
   Transmitter reaches receptor proteins on postsynaptic membrane via diffusion
   These receptors are ligand-gated ion channels (their ligands is acetylcholine): some Na+ flows into muscle cell, depolarizing it
3. Voltage-gated Na+ channels open and action potential is generated in muscle cell membrane, travels into depth of muscle fiber via T-tubules
   Acetylcholine is broken down to acetic acid and choline by enzymes acetylcholine-esterase; components taken back up into presynaptic terminal for re-use

Question 22

Contraction of sarcomere

Answer 22

caused by sliding of thick filament (myosin) with thin filaments (actin)

Question 23

Low (Ca+++)

Answer 23

= myosin head cannot bind to actin filaments

- Tropomyosin and Troponin work together to block the myosin binding sites on actin

Question 24

High (Ca+++)

Answer 24

= myosin binding sites of actin become exposed

- when a calcium ion binds to troponin, the troponin-tropomyosin complex moves, exposing myosin binding sites

Question 25

Muscle action

Answer 25

- When the muscle is relaxed, myosin is not binded to actin - when muscle is in action, myosin can now bind to actin - actin and myosin become more overlapped - A single spike in a motor neuron causes a single excitatory postsynpatic potential (EDSP) spikes in the associated muscle fibers, followed by a single twitch - During contraction, length of actin and myosin does not change, the amount of overlapping does

Question 26

How does an entire muscle contract?

Answer 26

Force generated by entire muscle depends on - Number of motor units (aka motor neuron + associated muscle fibres) activated - frequency at which motor units are firing

Question 27

Motor units in vertebrates

Answer 27

For vertebrate skeletal muscle, each muscle fiber is innervated by a single motor neuron, but each motor neuron innervates many muscle fibers

Question 28

Types of Muscles

Answer 28

Skeletal muscle Cardiac muscles Smooth muscle

Question 29

Skeletal muscle

Answer 29

- striated - multinucleated - cylindrical - attached to bone via tendon

Question 30

Cardiac muscles

Answer 30

- striated - branched in shape, allows it to within high pressure - Gap junctions btwn cells allow synchronized contraction - smaller than skeleton muscle cells, have only one nucleus

Question 31

Smooth muscle

Answer 31

- blood vessel, digestive tract - actin and myosin is not regularly arranged, so does not appear striated - long, spindle shape with a single nucleus

Question 32

Muscle Summary

Answer 32

- Movement is based on antagonistic muscle groups that act on a skeleton. - Muscle tissue is composed of several muscle fibres, that are composed of myofibrils, composed of successions of sarcomeres. - Muscle contraction happens when myosin proteins move down the length of actin fibres. - Calcium ions play an essential role in muscle contraction, by making the actin in thin filament available for binding by myosin. - In animals with exoskeletons or endoskeletons, muscle are usually arranged in opposing pairs of flexors and extensors.