Chapter 16- Muscle and locomotion Flashcards
How do protozoans and primitive algae move?
They more by beating cilia or flagella
Each cilia and flagella of all eukaryotic cells possess what type of basic structure?
A cylindrical stalk of 11 microtubules- 9 paires microtubules arranged in a circle with 2 single microtubules in the center.
How do flagella acheive movement?
By a power stroke
Power stroke
A thrusting movement generated by the sliding action of microtubules.
Recovery stroke
Return of the cilium or flagellum to its original position
Pseudopodia
Used by amoeba for locomotion, the advancing cell moves forward, allowing cell to move.
What kine of skeleton do invertebrates have? (flatworms and annelida)
Hydrostatic
Muscles in flatworms such as planaria are arranged:
in two antagonistic layers: longitudinal and circular
What is a hydrostatic skeleton?
When muscles contract against the resistance of the incompressible fluid within the animal’s tissue
Contraction of the circular layer of muscles causes:
the incompressible interstitial fluid to flow longitudinally, lengthening the animal.
Contraction of the longitudinal layer of muscles:
shortens the animal
Setae
Bristles in the lower part of each segment in annelids anchor the earthworm temporarily in the earth while muscles push it ahread.
Exoskeleton
A hard skeleton that covers all muscles and organs of some invertebrates.
What are exoskeletons found in?
Principally in arthropods such as insecrs
Chitin
What insect exoskeletons are composed of: non cellular material secreted by the epidermis.
What must happen for insects to grow?
Periodic molten and new skeleton deposition
Endoskeleton
Framework within all vertebrate organisms. Muscles are attached to the bone, permitting movement.
Rib cage protecs
thoracic organs (heart and lungs)
Vertebrate column
protects the spinal cord
Bone
Mineralized connective tissue
Two types of bone
Compact
Spongy
Compact bone
Dense bone- does not have cavities when looked at with naked eye
Osteons
structural units of bony matrix of compact bone
Haversian Canal
Central microscopic channel that each osteon is made of.
Lamellae
Concentric circles of bony matrix that surround the Haversian canal.
Spongy bone
Much less dense than compact bone. Made of of an interconnected lattice of bony spicules (trabulae).
What is the cavities in between the spicules filled with?
Red or yellow bone marrow.
Yellow marrow
inactive and infiltrated by adipose tissue
Red marrow
Involved in blood cell formation
What are the two types of bone cells?
Osteoblasts and osteoclasts
Osteoblasts
Synthesize and secrete the organic constituents of of the bone matrix; once they have become surrounded by their marrix, they mature into OSTEOCYTES.
Osteoclasts
Large, multinucleated cells involved in bone resorption
Bone formation occurs by either:
Endochondral ossification or by intramembranous ossification.
Endochondral ossification
existing cartilage is replaced by bone– how long bones arise.
Intramembranous ossification
Mesenchymal (embryonic or undifferentiated) connective tissue is transformed into, and replaced by, bone.
Axial skeleton
Basic framework of the body, consisting of skull, vertrebral column, and the rib cage. Point of attachment of the appendicular skeleton
Appendicular skeleton
Bones of the appendages and the pectoral and pelvic girdles.
How are bones of skull held together?
Sutures or immovable joints that hold bones of skull together
Bones that move relative to one another are held together by
movable joints and are additionally supported and strengthened by ligaments.
Ligaments
Serve as bone-to bone connectors.
Tendons
Attach skeletal muscle to bones and bend the skeleton at the movable koints
Origin
Point of attachment of a muscle to a stationary bone
Insertion
The point of attachment of a muscle to the bone that moves
Extension
Straightening of a bone
Flexion
Bending of a joint
Muscle tissue consists of
Bundles of specialized contractile fibers held together by connective tissue
3 types of muscles in mammals
Skeletal, Cardiac and smooth
The axons of the pyramidal cells of motor cortex descent to
synapse on lower motor neurons in the brain stem and the spinal cord.
Pyramidal system
Provides rapid commands to skeletal muscles and other organs.
No intervening synapses, hence rapid
Extrapyramidal system
Centers that issue somatic motor commands as a result of processing performed at the unconscious, involuntary level.
Red nucleus
Located in the mesencephalon, component of the extrapyramidal system primarily in control of skeletal muscle tone.
Skeletal muscle is responsible for:
the voluntary movements
What is skeletal muscle innervated by?
The somatic nervous system
Each fiber of the skeletal muscle is
multinucleated cell created by the fusion of serveral mononucleated embryonic cells
Myofibrils
Embedded in fibers
Filaments– divided into contractile units called sarcomeres
What are the myofibrils enveloped by?
A modified endoplasmic reticulum that stores calcium ions
What is the modified endoplasmic reticulum called?
Sarcoplasmic reticulum
Sarcoplasm
Cytoplasm of the muscle fiber
Cell membrane of the muscle fiber
sarcolemma
Sarcolemma
Propagates action potential
What is the sarcolemma connected to?
A system of tranverse tubules (T system) which are oriented perpendicularly to the myofibrils.
What does the T system provide?
Channels for ion flow throughout the muscle fibers and can also propagate an action potential.
Are mitochondria abundant in muscle cells? Why?
Yes because the energy requirements of contraction are very high.
Striated muscle
Skeletal muscle is called striated because it has striations of light and dark bands
Sarcomere is composed of:
Thin and thick filaments.
Thin filaments of the sarcomere are
Chains of actin molecules
Thick filaments of the sacromere are
Organized bundles of myosin molecules
Z line
Define the boundaries of a single sarcomere and anchor the thin filaments
I band
Region containaing the thin filaments only
H zone
Region containing thick filaments only
A band
Spans the entire length of thick filaments and the overlapping portions of the thin filaments
What bands are reduced during contraction?
H and I, NOT A
What is muscle contraction stimulated by?
Message from the somatic nervous system sent via a motor neuron.
Neuromusclular junction
The link between the nerve terminal and the sarcolemma of the muscle fiber.
Synpase
The space between the nerve terminal and the sarcolemma of the muscle fiber
Depolarization of motor neuron results in
The release of neurotransmitters from the nerve terminal
What does the neurotransmitter do after it has been relaeased?
Diffuses across the synaptic cleft and binds to special receptor sites on the sarcolemma.
What needs to happen for the permeability of the sarcolemma to be altered and an action potential to be released?
Enough of receptor sites on the sarcolemma need to be stimulated.
What happens when an action potential is generated?
It is conducted along the sarcolemma and the T system and into the interior of the muscle fiber. This causes release of calcium from sarcoplasmic reticulum into the sarcoplasm
Calcium ions:
Initiate the contraction of the sarcomere
Actin and myosin must ____ in order for the muscle to contract
Slide past each other
Rigor mortis
Caused by absense of adensine triphosphate, which is required for the myosin heads to be released and stop contraction
5 types of muscle contraction
Isotonic, concentric, cynamic, eccentric, and isometric
Isotonic
Occurs when a muscle shortens against a fixed load whie the tension of that muscle remains constant
Shortens
Tension constant
fixed load
Concentric
Dynamic contraction when the muscle fibers shorten and the tension on the muscle increases
Shorten
Tension increase
Dynamic
Both concentric and isotonic results in a change of length of the muscle with a corresponding change in tension of that muscle
Eccentric
A type of dynamic contraction
Lengthens, and tension increases
Isometric
Occurs when both ends of the msucle are fized and no change in length occurs
Tension increases
All or non response
Individual muscle fibers generally exhibit an all-or-none response, meaning only a stimulus above a minimal value can elicit contraction.
How can strength of single muscle increase?
Cannot, all or none
How can strength of whole muscle increase?
Recruit more muscle fibers
Simple twitch
A response of a single muscle fiber to a brief stimulus at or above the threshold stimulus
What does a simple twitch consist of?
Latent period, contraction period, and relaxation period
What happens during the latent period?
The action potential spreads along the sarcolemma, and CA2+ ions are released
Absolute refractory period
Occurs after contraction period– a brief relaxation period in which muscle is unresponsive to a stimulus
Temporal summation
When fibers of a muscle are exposed to very frequent stimuli– muscle cannot fully relax. Contraction begin to combine becoming stronger.
Tetanus
When contractions become continuous and cannot relax at all. Results in fatigue in order to contract.
Tonus
A state of partial contraction. Muscles are never completely relaxed and maintain a partially contracted state at all times.
What do skeletal muscles do in period of strenuous activity?
Convert glucose to pyruvic acid in the process of glucolysis.
What does conversion of glucose to pyruvic acid allow the muscles to do?
Continue contracting in the absence of oxygen
When is lactic acid generated?
When pyruvic acid is reacted with the enzyme lactate dehydrogenase– which allows the puruvate to enter Krebs or tricarboxylic cycle
Cori cycle
Convert lactic acid in the liver to glucose for discharge into the bloodstream– not related to the conversion of glucose.
Smooth muscle
Responsible for involuntary actions. Smooth continuous contractions
What are smooth muscles innvervated by?
Autonomic nervous system
Where is smooth muscle found?
Found in the digestive tract, bladder, uterus, and blood vessel walls
True or false: smooth muscles have striations
FALSE
How many nucleus/nuclei do smooth muscles have?
1 centrally located nucleus
Cardiac muscle
Striated
One or two nuclei per cell
Involuntary/autonomic nervous system
Strong forceful contraction
What is the primary source of energy for muscle contraction?
ATP– however, very little ATP is actually stores in the muscles so other forms of energy must be stores and rapid converted to ATP
Creatine phosphate
A high-energy compound- in vertebrates and some invertebrates, where energy can temporarily be stored.
Arginine phosphate
Similar to creatine phosphate, many invertebrates use to store energy.
Myoglobin
Hemoglobin like protein found in muscle tissue- Has high oxygen affinity and maintains the oxygen supply in muscles by binding to oxygen tightly.
