MCAT BIO CH. 11 PART 1 Flashcards
What are the three types of muscle?
- Skeletal
- Cardiac
- Smooth
What are tendons?
Connect muscles, strong connective tissue formed of collagen
What are the four ways skeletal muscles can move?
- Flexing
- Extending
- Abducting
- Adducting
What skeletal muscle movement is flexing?
Muscles can move a joint by flexing
What skeletal muscle movement is extending?
Increasing the angle of the joint
What skeletal muscle movement is abducting?
Moving away from the body’s midline
What skeletal muscle movement is adducting?
Moving towards the body’s midline
What is the only way for bones and joints to move?
By contracting skeletal muscles
What does it mean when a skeletal muscle has an origin?
Point on this bone where the muscle attaches
What does it mean when a skeletal muscle has a muscle insertion?
Point where the muscle attaches on the bone more distant from the center of the body
What are muscles that are antagonistic?
Muscles that are responsible for movement in opposite direction
What are muscles that are synergistic?
Muscles that move a joint in the same direction
When antagonistic muscles receive stimulation by neurons, how do they differ between contraction and relaxation?
Difference in timing of the signal (frequency) and the amount of neurotransmitter released
What are fascicles based on structure of skeletal muscle?
Connective tissue that holds the contractile tissue together in bundles to allow flexibility within the muscle
What are muscle fibers?
Myofibers; single skeletal muscle cell
Where are myofibers found?
Located within each fascicles bundle
What is an important factor of the nucleus of skeletal muscle cells?
They are multinucleate syncytia
How is the multinucleate syncytia formed in skeletal muscle cells?
By the fusion of individual cells during development
What is sarcolemma?
The myofiber cell membrane
What is the sarcolemma made out of?
Of plasma membrane and an additional layer of polysaccharide and collagen
Why is it important for the myofiber to have sarcolemma?
Helps the cell to fuse with tendon fibers
What are myofibrils?
Smaller myofiber units that generate contractile force of skeletal muscle
What are the proteins in the myofibril that generate contraction?
Actin and myosin
What is the difference between actin and myosin when they polymerize?
Actin polymerizes to form thin filaments, myosin forms thick filaments
What is the reason for the striated appearance of the skeletal muscle?
Due to the overlapping arrangement of bands of thick and thin filaments in sarcomeres
What are the sarcomeres bound by?
Z lines
How are the sarcomeres aligned and where are they located?
End to end, in myofibril
Thick filaments are also attached to the Z lines. T/F
False: they are not
Thin filaments attach to each Z line and overlap with ______ in the middle of each ______?
Thick filaments; sarcomere
What are I bands based on myofibril?
Regions of he sarcomere composed only of thin filaments
What are A band based on myofibril?
The full length of the thick filament represents the A band within each sarcomere
What is the H zone based on myofibril?
Region composed of only thick filaments
Where is contraction generated based on myofibril structure?
Overlapping regions of thick and thin filaments
Based on thick and thin filaments, when does contraction occur based on their structure?
When the thin and thick filaments slide across each other, drawing the Z lines of each sarcomere closer together
During muscle contraction, do thick and thin filaments shorten? What shortens?
No they slide across each other; the sarcomere sheens without them changing their lengths
Filament sliding requires….?
ATP hydrolysis
Which protein uses ATP to create movement?
Myosin - sometimes also named myosin ATPase
Each myosin monomer contains a ___ and a ____?
Head and tail
The head of the myosin monomer attaches to what?
The myosin binding site; a specific site on an actin molecule
When myosin and actin are connected, they’re said to be connected by….
A crossbridge
Contraction occurs when what decreased, based on myosin and actin?
When the angle between the head and the tail decreases
What is the first step of filament sliding in skeletal muscle?
Cross bridge formation; myosin has ADP and Pi bond
What is cross bridge formation?
Binding of the myosin head to a myosin binding site on actin
What is the second step of filament sliding in skeletal muscle?
Power stroke from myosin
What is the power stroke from myosin and when does it happen during filament sliding?
Myosin head moves to a low energy confirmation and pulls actin chain towards center of sarcomere; ADP is released and during 2nd step
What happens during step two then myosin head moves to a low energy confirmation?
They pull actin chain towards center of sarcomere
In which step of filament sliding does a new ATP molecule binds?
Step 3
What is the third step of filament sliding in skeletal muscle?
ATP binding necessary to release actin by the myosin head
What is the four step of filament sliding in skeletal muscle?
ATP hydrolysis, myosin head cocked formation
What does is mean when mentioned the myosin heads are cocked?
Set in a high-energy conformation
In the myofiber, contraction only occurs when…?
The cytoplasmic Ca2+ increases
Which molecule contains troponin-tropomyosin complex?
Thin filaments
What does troponin-tropomyosin complex?
Prevents contraction when Ca2+ is not present
What is tropomyosin?
A long fibrous protein that winds around the actin polymer, blocking all the myosin-binding sites
What is troponin?
A globular protein bound to the tropomyosin that can bind Ca2+
What happens to troponin when it binds to Ca2+?
It undergoes conformation change that moves tropomyosin out of the way so that myosin heads can attach to actin
What protein is responsible for ATP hydrolysis during muscle contraction?
Myosin protein with the ATPase activity
What is the neuromuscular junction?
The synapse between an axon terminus and a myofiber
The neuromuscular junction is a single point. T/F
False: A long invagination of the cell membrane - axon terminus is elongated to fill the long synaptic cleft
What is the purpose of the neuromuscular junction?
Allow the neuron to depolarize a large region of the postsynaptic membrane at once
What is the motor end plate?
The postsynaptic membrane of the neuromuscular junction
What is the neurotransmitter as the neuromuscular junction point?
ACh acetylcholne
During the impulse transmission at the NMJ, an action potential arrives at the axon terminus and triggers the opening of _______ channels?
voltage-gated Ca 2+ channels
During the impulse transmission at the NMJ, the resulting increase in ________ triggers the _______ of ACh?
Intracellular Ca 2+; release of vesicles of acetylcholine
What does the postsynaptic membrane contain to read ACh?
Contains ACh receptors which are ligand-gated Na+ channels
Based on impulse transmission in NMJ, how does ACh reach their receptors?
By diffusing across the synaptic cleft
What happens when ACh binds to the receptors of the postsynaptic membrane receptors?
A postsynaptic sodium influx, which depolarizes the postsynaptic membrane
What is the end late potential?
The depolarization of the postsynaptic membrane when ACh binds to the receptors of the postsynaptic membrane
What is the miniature EPP?
The smallest measurable AP dcaused by exocytosis of a single ACh vesicle
When does ACh stop stimulating postsynaptic receptors?
Until it is destroyed by acetylcholinesterase
What are T-tubules?
Transverse tubules; deep invaginations of the cell membrane which allow the AP to travel into the thick cell
What is the structure of the sarcoplasmic reticulum?
A huge, specialized smooth endoplasmic reticulum that enfolded each myofibril in the cell
What is the SR specialization?
Specialized to sequester and release Ca 2+
How is the calcium removed from the SR?
Active transporters remove calcium from the sarcoplasm
What is the sarcoplasm?
Myofiber cytoplasm
What happens when the AP travels down the T-tubular network?
It depolarizes the cell and the sarcoplasmic reticulum
The sarcoplasmic reticulum contains what? What does it allow?
Voltage-gated Ca 2+ channels, allows calcium to rush out of the SR into the sarcoplasm upon depolarization
When the cell myofiber repolarizes, what happens to the calcium?
It is actively sequestered by the SR and contracted is ended
The smallest measurable muscle contraction is know as….?
Muscle twitch
What are the two ways the nervous system can increase the force of contraction?
- Motor unit recruitment
2. Frequency summation
What is a motor unit?
A group of myofibers innervated by the branches of a single motor neuron’s axon
What does a muscle twitch result from?
The activation of one motor neuron and a larger twitch can be obtained by activating more motor neurons
What is a motor unit recruitment?
Activating or recruiting more motor neurons and thus more myofibers
When does each contraction ends?
When the SR returns calcium to low resting levels
What is tetanus?
Rapidly repeating series of stimulation resulting in the strongest contraction possible
The skeletal muscle does not have a refractory period.T/F
False: it does
What is frequency summation?
The second contraction builds on the first as there’s no time for calcium to become sequestered
When does frequency summation over through refractory period?
Successive stimulation must be greater than the duration of the refractory period
What is the length-tension relationship?
A muscle contracts more forcefully at an optimum length
What is the length of a sarcomere at the muscle contracting at optimum length?
2.2 microns
What happens at 2.2 microns in sarcomere length based on contraction?
A maximum degree of overlap between thick and thin filaments
Why is greater sarcomere length favorable compared to shorter length?
A shorter length causes filaments to obstruct each other’s movement by bumping together
What molecule is used for intermediate-term energy storage in the myofiber?
Creatine phosphate
What is myoglobin? What is its role?
A globular protein; provide an oxygen reserve by taking O2 rom hemoglobin and then releasing it as needed
What happens when the supply of oxygen runs low in the myofiber?
Metabolism becomes anaerobic and lactic acid is produced
When lactic acid is produced, how does it cause a pH drop in the blood?
Because it moves into th bloodstream
What happens to the lactic acid that infiltrates our blood, how is it removed?
The liver picks up this lactate and converts it into pyruvate
What is rigor mortis?
Rigidity of skeletal muscles which occurs soon after death due to complete ATP exhaustion
Skeletal muscle fibers fall into two categories:….
Slow twitch fibers and fast twitch fibers
What are type I slow twitch fibers known as?
Red slow twitch or red oxidative
Why are they called red oxidative or red slow twitch fibers?
Because of their high myoglobin content
Why do red oxidative have much better blood supply than fast twitch fibers?
Extensive surrounding capillary network
What allows slow twitch fibers to maintain contraction for extended periods of time?
Good oxygen delivery and ability to store oxygen in myoglobin
Why does Type IIA fast twitch fibers has more fatigue resistant than Type II B?
Have more mitochondria
What are Type IIA known as?
Fast twitch oxidative fibers
What type of force does Type IIB fast twitch fibers provide?
Explosive force needed
What is different between the skeletal muscle maximum length and the cardiac muscle maximum length?
Cardiac muscle has no such limitations
What is different between the structure of skeletal and cardiac muscle?
Skeletal muscles are syncytial and cardiacs are not, they each only have one nucleus
All the muscle cells in the cardiac muscle are interconnected with what?
By gap junctions known as intercalated disks
What do the intercalated disks in the cardiac muscle allow?
Allow AP to propagate throughout the entire heart without allowing nuclei and cytoplasmic contents to be shared
What is heart muscle called based on the function of their intercalated discs?
Functional syncytium
What is different between the calcium content between skeletal and cardiac muscle?
Skeletal muscle calcium comes for SR intracellular structure, cardiac muscle requires some from extracellular environment
If neurons don’t trigger cardiac contraction, what does?
Pacing by the sinoatrial node
Which muscle does not depend on stimulation by motor neurons?
Cardiac muscles
The vagus nerve release ACH for heart muscle at chemical synapses with the heart is….?
Inhibitory
What type of channels is the AP in cardiac muscles dependent on?
Na and Ca channels
What are sodium channels in the cardiac muscles called? What about calcium channels?
Sodium: fast channels Calcium: slow channels
Why are calcium channels in cardiac muscles called slow channels?
They respond more slowly to threshold depolarization
What does the voltage-gated calcium channel in cardiac muscle cause the cardiac AP to have?
Plateau
What is the significance of the plateau phase in cardiac muscle?
- Longer duration of contraction
2. Longer refractory period to prevent disorganized impulses
Smooth muscles have T-tubules. T/F
False: they’re too small
Smooth muscles are narrower and shorter than skeletal muscles. T/F
True
How many nucleus do smooth muscle cells have? How is it connected to its neighbors?
One nucleus; by gap junctions
Why does the cell appear smooth and not striated in smooth muscle cells?
Thick and thin filaments not organized into sarcomeres in smooth muscle
What molecules control contraction in smooth muscle cells?
Calmodulin and myosin light-chain kinase
What does calmodulin do and what does myosin light-chain kinase do?
Binds Ca 2+ and activates MLCK, MLCK then phosphorylates a portion of the myosin molecule
What is different with the calcium storage of smooth and skeletal muscle?
Smooth muscle also relies on extracellular calcium
What does the smooth muscle cell action potential vary on?
Depending on the location of the smooth muscles
How do smooth muscles cells sometimes sustain prolonged contractions?
Has action potentials similar to those of cardiac muscle, although with a less sharp spike
How are the resting potentials of smooth muscle cells?
Fluctuating
The fluctuations in resting potentials are called what and due to what?
Called slow waves; ion pass through the gap junctions between neighboring cells, causing the changes in resting potential to propagate like waves
What are slow waves necessary for based on smooth muscle cells?
Coordinate the action potentials
How are the amplitudes of slow waves passing through smooth muscle cells altered?
Increased by ACh, decreased by NE
How do the motor neurons differ between smooth muscle cells and skeletal muscle cells?
Smooth: autonomic motor neurons while skeletal have somatic motor neurons
How does the action potential differ between smooth, skeletal and cardiac?
Skeletal: Each AP limited to one large myofiber
Cardiac: One large function syncytium
Smooth: Spreads from cell to cell; shares features of bot
What does the skeletal system synthesize and what is it called?
The elements ht blood; hematopoiesis
What are the axial components of the skeleton? What are the appendicular?
Axial: Skull, vertebral column and rib cage
Appendicular: all other bones
What are connective tissues derived from?
Fibroblast, progenitor
What are two important fibrous protein?
Collage, elastin
What are three important fibroblast cells?
Adipocytes (fat cells), Chondrocytes (Cartilage cells), Osteocytes (Bone cells)
Why does connective tissue differ from other tissue types in the body?
Primarily extracellular material wit few cells scattered in it
What is the matrix based on connective tissue?
Extracellular material
What are ground substance based on connective tissue?
Fibers in connective tissue, thick viscous material
What are the main ingredients of the ground substance in connective tissue?
Proteoglycans
What are proteoglycans?
Large macropolymers consisting of protein core with many attached carbohydrate chains in connective tissue
What are glycosaminoglycans?
Carbohydrate chains that attach proteoglycans in connective tissue
What gives connective tissues their thickness and firmness?
The carbohydrate chains of the connective tissue are hydrophilic
What are the two types of connective tissue?
- Loose
2. Dense
What is loose connective tissue?
Packing tissues including areolar tissue and adipose tissue
What is areolar tissue and what is adipose tissue?
Areolar: Soft material between cells Adipose: Fat tissue
What is dense connective tissue?
Tissues that contain large amounts of fibers
What are the two types of bone shapes?
Flat and long
What are flat bones mostly used for?
Protection of organs
What are long bones used for?
Support and movement
What is a diaphysis? What about. an epiphysis?
Main shaft of a long bone; flared end
What are the two general structures of a bone?
Compact or spongy
How are compact bones based on structure? What about spongy?
Compact: hard and dense
Spongy: Porous
Where are spongy bones always found?
Surrounded by a layer of compact bone
What are the three different types of marrows?
- Bone marrows
- Yellow marrow
- Red marrow
What is bone marrow?
Non-bony material found int he shafts of long bones and pores of spongy bones
What is red marrow?
Found in spongy bone within flat bones and is the site of hematopoiesis
What is yellow marrow?
Found in the shafts of long bones filled with fat and is inactive
Bones are composed of two principal ingredients, what are they?
- Collagen
2. Hydroxyapatite
What is hydroxyapatite?
Solid material consisting of calcium phosphate crystals
What characteristic does hydroxyapatite provide for bone structures?
strength and inflexibility
What are spicules or trabeculae?
Spikes of bone in spongy
What is an osteon?
The basic unit of compact bone structure
What is the osteon sometimes referred to?
Haversian system
What is the central canal of the osteon?
A hole which contains blood, lymph vessels and nerves
What are lamellae in compact bones?
Surrounding the cancel, concentric rings of bone
What is the canaliculi of compact bones? What about the lacunae?
Tiny channels; spaces
Where are osteocytes located and what are they?
In each lacuna; mature bone cell
Why do osteocytes have long processes that extend down the canaliculi?
To contact other osteocytes through gap junctions allowing cells to exchange nutrients and waste
What are perforating or volkmann’s canals?
Channels that run perpendicular to central canals to connect osteons
What is cartilage?
A strong, flexible extrcellular tissue
What is cartilage secrete by?
Chondrocytes
What are the three types of cartilage?
Hyaline, elastic and fibrous
What is hyaline cartilage and found where?
Strong and somewhat flexible; found in larynx and trachea
What is elastic cartilage?
Contains elastin; found in areas that require support and more flexibility - outer ear and epiglottis
What is articular cartilage?
Joints lined by hyaline cartilage
What is fibrous cartilage?
Rigid and found in places where very wrong support is needed
What does avascular mean? Which component the body is that?
No blood vessels; cartilage
How does cartilage receive nutrition and immunity since its avascular?
From surrounding fluid
What is the difference between ligaments and tendons?
Ligaments connect bones to other bones, tendons connect bones to muscles
What are synarthroses joints?
Immovable joints
What are amphiarthroses joints?
Slightly movable joints
Wha are diarthroses joints?
Freely movable joints
What are Immovable joints called?
synarthroses
What are Slightly movable joints called?
amphiarthroses
What are Freely movable joints called?
diarthroses
What is synovial fluid?
Lubricate movable joints, kept within the synovial capsule
What does arthritis damage?
Destruction of articular cartilage
Bone growth occurs by what?
Endochondral ossification - hyaline cartilage is produced and replaced by bone
What is intramembranous ossification?
Synthesis of bone from an embryonic tissue called mesenchyme
What does intramembranous ossification result in?
Flat bones
What is the epiphyseal plate?
A disk of hyaline cartilage that is actively being produced by chondrocytes
Where is the epiphyseal plate found?
Between the diaphysis and epiphysis
What is the epiphyseal line?
The fusion point where the diaphysis and epiphysis have fused together
What is the bone process called remodeling?
Bones are degraded and remade
What are osteoblasts?
Cells that make bone by laying down collage and hydroxyapatite
What do osteoclasts do?
Dissolve hydroxyapatite crystals
Which hormones control the activity of osteoclasts and osteoblasts?
Parathyroid hormone, calcitonin and calcitriol
What is calcitriol derived from?
Kidney from vitamin D
Which hormones controlling the osteoclast to osteoblast activity reduces it?
Calcitonin
Which hormones controlling the osteoclast to osteoblast activity increases it?
PTH and calcitriol
What is the effect of parathyroid hormone on the kidney?
Increases absorption of calcium
What is the effect of parathyroid hormone on the intestines?
Increases intestinal calcium absorption
What is the effect of calcitriol on the intestines?
Increases intestinal calcium absorption
What is the effect of calcitriol on the kidneys?
Increases reabsorption’s of phosphorus
What is the effect of calcitonin on the kidneys?
Decreases reabsorption of calcium
What is the effect of calcitonin on the intestines?
Doesn’t have any
