Bio Midterm - 2

KILL MEEEEEE PLEASE

Define the term "pathogen"

Define the term "pathogen"

A pathogen is something that can get into your body and cause severe harm to you, eventually becoming a disease.

Define the term "host".

A host is whatever the pathogen wants to enter and infect, an organism that holds the pathogen.

List the three main types of immune systems in your body.

Innate, adaptive, and passive immunity.

List and describe external components of the immune system.

Begins with lymphatic capillaries that take up excess fluid.

It then flows one way from a capillary to ever larger lymphatic vessels and finally to a lymphatic duct, which enters a subclavian vein where it can then be managed by the kidney.

Discuss ways that pathogens can make it past the external defenses of the immune system providing examples.

One way that a pathogen could make it past the external defenses of the immune system is to get a cut on your hand. By receiving a cut, you are much more at risk for pathogens to enter your body.

Discuss the inflammatory response providing the processes and listing the major cells and proteins involved.

An inflammatory response is a nonspecific defense from the immune system. Damaged cells and mast cells release histamines and kinins. When these are released, capillaries dilate and become more permeable. Enlarged capillaries cause skin to redden. 

Swollen areas and kinins stimulate free nerve endings and cause pain. Neutrophils and monocytes migrate to the site of the injury, moving in masses to clean up the mess before it causes a disease. 

• Neutrophils and mast cells phagocytize pathogens. 

• Monocytes differentiate into macrophages (big eaters)

• Both release hydrolytic enzymes when combined with lysosomes that destroy material that was engulfed. 

Discuss the role of phagocytes in the innate immune response.

The meaning of phagocytes is essentially “eat cells”. They eat many of the pathogen cells within the body during an innate immune response.

Describe the function of hydrolytic enzymes.

Hydrolytic enzymes break down protein, lipids, nucleic acids, carbs, and fat molecules into their simplest units.

Describe the function of colony stimulating factors.

CSFs send out signals causing cells to proliferate and differentiate into a specific kind of blood cell (typically leukocytes/white blood cells).

Describe the function of Interferon.

Interferon binds to receptors of non-infected cells, causing them to prepare for possible attack by producing substances that interfere with viral replication. (Preventative measures)

Define the term "antigen".

An antigen is any foreign substance that stimulates the immune system to react. Antigen = antibody generating substance or non-self (not you) protein.

What do antigen receptors allow Lymphocytes to do?

Antigen receptors allow Lymphocytes to recognize antigens and destroy them, stopping the pathogen before it kills you.

Compare and contrast T cells and B cells providing their functions and where they mature.

Immunity is primarily the result of B lymphocytes ( made in bone-marrow, plasma producing) and T lymphocytes ( made in the thymus gland can become a multitude of different immune cells.)

• B cells give rise to plasma cells, which produce antibodies for a pathogen. Once those have been produced, B-memory cells are also produced and they will always remember how to fight that specific pathogen.

• T cells directly attack cells that bear non-self proteins, while others regulate the immune response (helper T-Cells).   

List the homeostatic functions of the lymphatic system.

• Lymphatic capillaries take up and return excess fluid to the bloodstream

• Lacteals receive lipoproteins and transport them to the bloodstream

• Helps defend body against disease (production, maintenance, and distribution of lymphocytes)

What is edema?

Edema is localized swelling due to the accumulation of tissue fluid

What is lymph?

Lymph is tissue fluid that has entered the lymphatic vessels (typically green)

Where is lymph dumped into the bloodstream?

Lymph is dumped into the bloodstream by the subclavian vein, which dumps it back into the blood so that the liquid can be managed by the kidney.

List three lymphoid organs and describe their function. (Listing all for ease)

Lymph Nodes

• Capsule surrounding two distinct regions, the cortex and the medulla

  • Lymphocytes congregate in the cortex (outer layer) when fighting off a pathogen

  • Macrophages concentrated in medulla (inner layer) cleanse lymph

Tonsils

• Patches of lymphatic tissue located around the pharynx

  • First to encounter pathogens that enter via the nose and mouth

Spleen 

• Located in the upper left region of the abdominal cavity just beneath the diaphragm

  • Cleanses blood (white pulp filters bacteria and debris, red pulp filters worn-out RBCs)  

Thymus Gland 

• Located along the trachea behind the sternum in the upper thoracic cavity. Produces thymic hormones (thymic aids in the maturation of T-lymphocytes in this gland [ T-Cells ] )

Red Bone Marrow

• Origin for all types of blood cells

• Area of maturation for most white blood cells

• B-lymphocytes mature here and this is where many stem cells are located [B-Cells])

List the names and functions of all five types of white blood cells.

Neutrophils (granular, all granular end with the suffix -phil)

• Most common of leukocytes, phagocytize pathogens 

Eosinophils 

• Important to phagocytosis, fighting back against allergens

Basophils

• Required to initiate an immune response

Lymphocytes

• Responsible for specific immunity. If they mature in the thymus gland they become T-cells and if they mature in the Bone marrow they are called B-Cells

Monocytes

• Can become the macrophages that phagocytize (eat cells) pathogens and cellular debris

Describe antibody mediated immunity.

If the same antigen enters the system again, the memory B cells divide quickly and make more lymphocytes, which are capable of becoming plasma cells and more quickly produce antibodies.

Describe the clonal selection theory.

States that as your body figures out which B lymphocyte can fight the pathogen, it’ll take that and clone that lymphocyte millions of times.

List three Immunoglobins and their function. (Listing all for ease)

Specific antibodies that are carried in the body all the time. 

IgG - Main antibody type in circulation. Attacks anything foreign. 

• Binds to pathogens, activates complement, and enhances phagocytosis

IgM - Found in circulation. Largest antibody

• Activates complement; clumps cells

IgA - Found in secretions

• Prevents pathogens from attaching to epithelial cells in digestive and respiratory tract

IgD - Found on the surface of immature B cells. 

• Presence signifies the readiness of B Cell

IgE - Found as antigen receptors on basophils in blood and on mast cells in tissue. (Causes runny nose, itchy eyes, etc.)

• Responsible for immediate allergic response; protection against certain parasitic worms. 

What is humor (biologically)?

Any fluid normally occurring in the body.

What are cytokines and list their function.

Cytokines signal chemicals that stimulate various immune cells. They are signaling molecules produced by lymphocytes, monocytes, and other cells. 

• Both interferon and interleukins have been used as immunotherapeutic drugs to enhance the ability of the individuals own T cells (and B cells) to fight cancer. 

• May be used to fight chronic infectious diseases

• Interleukin antagonists may lead to medicines for allergies, autoimmune disease, and organ rejection

What are MHC molecules and HLA molecules.

Major histocompatibility complexes, otherwise known as MHC proteins, are in the plasma membrane of the macrophage and they link to antigens. Human Leukocyte Antigens (HLA) molecules are genes inside MHC that help differ between self and non-self proteins.

Describe Cell-Mediated Immunity.

This is when T Cells attack target cells, creating holes in the cell and bursting it- eliminating the cancer/virus inside the cell.

Discuss Cytotoxic T Cells and list their function.

Cytotoxic T Cells can recognize the antigen and consume it. They then go through a programmed cell death called Apoptosis. 

• Destroy antigen bearing cells

• Contain perforins (will perforate a plasma membrane) this causes holes and other solutes to move in and burst a cancer causing cell or virus 

• Responsible for cell mediated immunity. 

Discuss helper T cells listing their function.

Helper T-Cells regulate immunity by secreting cytokines. HIV infects helper T cells and other cells of the immune system, inactivating the entire specific defenses of the body.

Describe the hypothesis as to why humans of European descent are less susceptible to AIDS.

Humans of European descent may be less susceptible to AIDS because the Bubonic Plague had certain characteristics similar to it. Because of this, natural selection has narrowed down the people of European origin and made them less susceptible.

Describe Induced Immunity.

Immunization is a form of induced immunity, in which the pathogen or pathogen products are treated to remove virulence. That then becomes a vaccine, and it is injected into a person with the antigen. This is dependent on the presence of memory B cells and memory T cells capable of responding to lower doses of antigen.

Discuss why it is necessary to receive a booster shot for vaccinations.

The first response your body receives to a vaccine is called a primary response. The first time you got the injection taught your body how to make antibodies, the second exposure helps to produce lots of antibodies that eliminate the pathogen before it leads to a serious disease.

Describe passive immunity and how it occurs.

Passive immunity occurs when an individual is given prepared antibodies (immunoglobins) to combat a disease. 

• Short-lived

• Newborns are often passively immune due to the mother’s blood.

Describe how Interleukin antagonists can help fight disease.

Interleukin antagonists help to reduce swelling and inflammation throughout the body.

List two uses of monoclonal antibodies.

Monoclonal antibodies are produced by plasma cells, derived from the same B Cells. 

• Used to determine pregnancy from urine 

• Used to detect infections 

• Used to deliver radioactive isotopes and toxic drugs to tumors, specifically made to target them. 

• Used in immunoassay tests to determine the presence of almost any molecule in the blood.

Define the term "allergy".

Hypersensitivities to substances that ordinarily would not harm the body. 

Immediate response: 

• IgE antibodies

Delayed response:

• Memory T cells

Describe a delayed allergic response and list three things that can cause it.

A few things can create a delayed response, which would include contact dermatitis. This can occur when a person is allergic to poison oak, jewelry, cosmetics, etc.

Describe the immediate allergic response listing the immunoglobin that causes it.

The immunoglobulin that causes an immediate allergic reaction is called IgE, and it causes the runny nose, itchy eyes, etc.

Discuss how an injection of an allergen may give relief to an allergy sufferer.

This causes the body to adapt to the allergen and learn how to fight against it, before large amounts of the real thing infect the body.

Describe ABO blood types and describe immune responses associated with transfusions.

There are two self antigens, the A protein and the B protein. There is also Rh, which is a separate protein in the blood. Anything positive has the Rh factor, anything Rh- does not have an Rh factor. 

Rh- individuals may produce antibodies to Rh factor if exposed. This can cause antibodies to attack the blood surrounding the baby. This makes miscarriage more likely. 

Type A has the A protein 

• A+ has both A and Rh

• A- only has the A 

• Type B has the B protein

  • B+ has both B and Rh

  • B- has only B 

• Type AB has both proteins 

  • AB+ has the A, B and Rh protein

• Type O has neither protein

  • O- has no proteins 

  • O+ has Rh

If the same antigen and active antibody are present in the blood, agglutination occurs. This blood wouldn't be able to flow through the capillaries as well, which can end up killing the organism.  

Define the term " autoimmune disease".

Diseases that destroy the body even if there is no pathogen. 

• Cytotoxic T cells or antibodies mistakenly attack the body’s own cells. 

• Includes multiple sclerosis, rheumatoid arthritis, myasthenia gravis, and systemic lupus erythematosus. Perhaps ever type 1 diabetes, and some types of coronary disease.

List and describe several functions of the skeletal systems as described in the lecture outline.

• Skeleton provides a rigid framework supporting the body and protecting its internal organs

  • Brain and spinal cord are almost completely enclosed within the skull are vertebral column 

  • The rib cage protects the lungs and the heart while the pelvic girdle supports and partially protects the abdominal organs. 

• Allows locomotion

  • Different skeletons will be used for a variety of locomotion, but we all use the same essential bones. 

  • Homologous bones may assume different forms, functions and positions based on the needs of the vertebrate. 

• Participates in sensory function 

  • Bones of middle ear transmit sound vibrations between eardrum and cochlea 

• Bones produce red blood cells, white blood cells, and platelets in the red bone marrow (located in sternum, ribs, upper arms, legs, and hips)

• Bones store calcium and phosphorus 

  • Absorb and release these as needed, maintaining a constant concentration in the blood. 

Discuss bone marrow and the cells it produces as well as its importance for modern medicine.

Bone marrow is very important for the body to have, producing red blood cells that carry oxygen as well as white blood cells like B-Cells. It makes nearly all the components of your blood.

Compare and contrast axial and appendicular skeletons.

Axial skeleton 

• Includes the bones of the head, vertebral column, and rib cage

• Supports and protects the long axis of the body

• Primary function is to protect the internal organs of the body

  • Ribs protect the thoracic and abdominal cavities 

  • Skull protects the brain

  • Vertebral column protects the spinal cord

Appendicular skeleton

• Contains all other bones (includes pectoral and pelvic girdles, and the appendages)

  • The forelimbs (arms and hands) and hindlimbs (legs and feet)

  • The pectoral girdle, which consists of the clavicle and scapula in humans. 

    • Links the arms to the axial skeleton and provides attachments sites for the muscles of the trunk and arms

  • Hip bones form the pelvic girdle

    • Links legs to the axial skeleton, helps protect the abdominal organs, and forms attachment sites for muscles of the trunk and legs 

Compare and contrast bone, cartilage and ligaments listing functions for each.

Cartilage, bone and ligaments are all three types of connective tissue that make up the skeleton. All three consist of living cells embedded in a matrix of collagen protein with various other substances included in the matrix.

Bone 

• Includes large amounts of minerals composed of mostly calcium and phosphate and is therefore hard and rigid. 

• Provides a strong,, rigid framework for the body

• Consists of a hard-outer shell of compact bone that encloses spongy bone in the interior. 

• Well supplied with blood vessels and can repair itself quite quickly. 

Cartilage 

• Contains large amounts of glycoproteins and often includes elastic fibers, which make some cartilage quite flexible (for example, the pinna of the outer ear).

• Provides flexible support and connections, and plays many roles in the vertebrate skeleton.

• Also covers the ends of bones at joints, supports flexible portions of the nose and ears, and provides the framework for the larynx, trachea, and bronchi of the respiratory system. 

• Living cells of cartilage are called chondrocytes

  • Secrete glycoproteins and collagen that make up most of the matrix 

• No blood vessels penetrate cartilage. To exchange wastes and nutrients, chondrocytes rely on diffusion of materials through the collagen matrix. 

• Have a very low metabolic rate, so damaged cartilage repairs itself very slowly if at all. 

  Ligaments

• Hold bones together at the joints and have small amounts of elastic fibers.

Compare and contrast compact bone and spongy bone.

Compact bone 

• Dense and strong, providing an attachment site for muscle 

• Develops as small tubes called osteons with collagen and calcium phosphate surrounding a central canal containing blood vessels. 

Spongy bone

• An open network of bony fibers 

• Porous, lightweight, rich in blood vessels

• Bone marrow, where blood cells form, is found in the cavities of spongy bone

Define the term “osteons”.

Tubes with collagen and calcium phosphate surrounding a central canal containing blood vessels. This eventually creates a compact bone.

Define and discuss osteoblasts, osteocytes, and osteoclasts providing the functions for each.

Osteoblasts 

• Bone forming cells

• Always active in body replacing bone where it needs to be replaced

• After osteoclasts have destroyed the cartilage, osteoblasts then secrete a hardened matrix of bone and gradually become entrapped within it.  

Osteocytes 

• Mature bone cells

• Bulk of cells in bone

• As bones mature, the trapped osteoblasts mature into osteocytes. 

• Essential to health because they constantly rework the calcium phosphate deposits, preventing excessive crystallization that would make the bone brittle and likely to break. 

Osteoclasts 

• Bone dissolving cells 

• Become more active as you get older, and you start to lose more bone.

• Early in development, when bone replaces cartilage in the skeleton, osteoclasts invade and dissolve the cartilage.   

Discuss bone remodeling and provide relative amounts of bone loss per year.

Bone remodeling allows skeletal repair and adaptation to stresses.Every year, 5% to 10% of all the bone in your body dissolves and is replaced by the coordinated activity of osteoclasts secreting acid that dissolves small amounts of bone, and osteoblasts that secrete new bone.

This allows the skeleton to alter its shape depending on the demands placed on it. Bones carrying heavy loads or subjected to extra stress may become thicker, providing more support.

Everyday stresses, such as walking, help to maintain bone strength.  

Compare and contrast the differences in bone replacement during an average human's life.

Bone remodeling varies as one ages. 

• Early in life, the activity of osteoblasts outpaces that of osteoclasts, allowing the bones to become larger and thicker as the child grows. 

• In the aging body, however, the balance of power shifts to favor osteoclasts and bones become more fragile as a result.

  • Although both sexes lose bone mass with age, this is typically more pronounced in women.

The ultimate bone remodeling occurs after a fracture.

• A physician moves the ends of the broken bone back into their proper alignment and immobilizes the break with a cast or splint. 

• The rest of the healing process is up to the body’s own repair mechanisms and usually takes approx 6 weeks.

Describe the process of bone healing after a fracture including all the major events.

A fracture ruptures the thin layer of connective tissue, rich in capillaries and osteoblasts, that surrounds the bone.

• Healing begins when a large blood clot surrounds the break 

  • Phagocytic cells from the blood and osteoclasts from the damaged bone ingest cellular debris and dissolve bone fragments.

  • Osteoblasts, alongside cartilage forming cells, secrete a callus and porous mass of bone and cartilage that surrounds the break.

  • The callus replaces the original blood clot and temporarily holds the break together

  • Osteoclasts, osteoblasts, and capillaries invade the callus

  • Nourished by the capillaries, the osteoclasts break down the cartilage while osteoblasts add new bone. 

  • Osteoclasts remove the excess bone and restore the bones original shape, often leaving a slight thickening.

Provide examples of non-movable joints in the human body.

An example of a non-movable joint in the human body is called a suture, joining the bones of the skull together.

Discuss ways that joints in the human body reduce wear and lubricate movable joints providing the correct anatomical structures that accomplish this task.

The portion of each bone forming the joint is coated with a layer of cartilage, which allows the bone surfaces to slide past one another with relatively little friction.

• Friction is reduced in joints by a lubricating fluid produced in the synovial sac (joint cavity).

  • Joints are held together by ligaments that are strong and flexible but not usually very elastic

  • Tendons attach muscles to bones

Compare and contrast hinge joints and ball and socket joints providing examples of representative anatomical structures that possess them.

Hinge joints are located in the elbows, knees and fingers. They only move in two dimensions. 

• In this case, the antagonistic muscle pair (flexor and extensor muscles) lie roughly in the same plane as the joint.

• When the flexor muscle contracts, it bends the joint; when the extensor muscle contracts, it straightens the joint

  • For example, contraction of the biceps femoris (flexor) bends the leg at the knee, while contraction of the quadriceps (the extensor) straightens it.

• Alternating contractions of flexor and extensor muscles cause the lower leg bones to swing back and forth at the knee joint. 

Ball and socket joints are round at one end of the bone, fitting into a hollow depression of another 

• These allow movement in several directions

• Range of motion is made possible by at least two pairs of antagonistic muscles oriented at angles to each other to move the joint in three dimensions.

Discuss how muscles work with the skeleton to cause movement.

Muscles and skeletons work together to provide movement. Without a skeleton, something with muscles would just lay on the floor and twitch. 

Despite enormous differences in body form and structure, nearly all animals move using the same fundamental mechanisms:

• Contracting muscles exert forces on the structure that supports the body, called a skeleton, and cause the body to change shape. 

• A body with its full complement of muscles, but no skeleton, would not have coordinated movement. 

• A skeleton without muscles would remain in one position unless someone else moved it.

Muscles produce force by contracting, only able to contract or not contract. It cannot use cellular energy to make itself longer. 

Explain what is meant by muscle lengthening is “passive” and relate lengthening to antagonistic muscles.

Muscle lengthening is passive because it occurs when muscles relax and are stretched by other forces, such as contractions of other muscles, the weight of a limb, or pressure from food (in the digestive tract).

Coordinated movement of an animal's body is produced by alternating contractions of muscles with opposing actions (called antagonistic muscles) which can make the digestive tract thinner or fatter, or move appendages back and forth.

Compare and contrast hydrostatic skeletons, exoskeletons, and endoskeletons.

Hydrostatic skeletons

• Water balloon, or a sac or tube filled with liquid 

• Means “to stand with water”, which is what hydrostatic skeletons do

  • Stands up because it contains water, but if punctured, it collapses. 

  • Volume is fixed, but you can change its shape by squeezing it in various places (which is what a muscle would do)

• Seen in jellyfish, worms, and many mollusks have this. 

Exoskeletons 

• Similar to a shell, skeleton on the outside. 

• Movement of the exoskeleton only occurs at joints in the legs, mouthparts, antennae, bases of wings, and body segments where thin and flexible join stiff sections of the skeleton. 

• Antagonistic muscles attach to opposite sides of the inside of a joint

  • Contraction of a flexor muscle bends a joint; contraction of an extensor straightens a joint 

  • Alternating contraction of the antagonistic muscles moves joints back and forth, allowing the animal to walk, fly or spin a web. 

• Because the exoskeleton cannot expand, it must be periodically molted. 

• Seen in crabs or lobster, arthropods. 

Endoskeletons

• Inside skeleton/internal skeletons 

• Movement also occurs primarily at joints, where two parts of the skeleton are attached to one another firmly but flexibly. 

• Antagonistic muscles such as the biceps (flexor) and triceps (extensor) attach on opposite sides of the outside of a joint and move the joint back and forth or rotate them in one direction or the other. 

• Seen in humans, found in echinoderms (sea stars and their relatives) and chordates (animals with a notochord, mostly vertebrates)

Compare and contrast flexor and extensor muscles.

Flexor

• Help to reduce the angle between two bones on either side of a joint.

• Think of bending your finger inward.

Extensor

• Play a crucial role in initiating extension, the straightening movement that increases the angle between two body parts.

• Think of straightening your knees.

Compare and contrast skeletal, smooth, and cardiac muscle tissue.

Skeletal muscles

• Moves the skeleton, appears striated (striped) when viewed through a microscope. Nearly all skeletal muscle is under voluntary or conscious control.

• Produce contractions ranging from quick twitches to powerful and sustained tension

• Highly organized, repeating structures (consists of a series of nested, repeating parts). 

• Skeletal muscles are encased in connective tissue sheaths and attached to the skeleton by fibrous tendons. Within the muscle’s outer sheath, individual muscle fibers (cells) are grouped into bundles by further coverings of connective tissue.

  • Blood vessels and nerves pass through the muscle in the spaces between the bundles, and each individual muscle fiber has its own thin connective tissue wrapping.  

    • These provide the strength for the muscle to keep from bursting apart during contraction  

Cardiac muscles

•  Also striated, located in the heart

• Is spontaneously active (initiating its own contractions) but is also influenced by the nervous system and hormones. 

• Usually not voluntary, but biofeedback training allows some people to regulate their heartbeat to a limited extent. 

Smooth muscles

• Smooth muscle is not striated

• Surrounds large blood vessels and most hollow organs, producing slow and sustained contractions that cannot be controlled voluntarily. 

• Movement of smooth muscle is termed “peristalsis”

Discuss the role of the multiple connective layers surrounding a muscle cell.

The connective tissue bundles the muscle fibers together.

Define and discuss myofibrils.

Individual muscle fibers contain many parallel cylinders called myofibrils. They are bundles of protein filaments that connect the contractile elements of skeletal muscles.

Discuss the role of the sarcoplasmic reticulum

Sarcoplasmic reticulum (SR) is a special type of endoplasmic reticulum, covering the myofibril. This consists of flattened, membrane enclosed compartments filled with fluid that contain a high concentration of calcium ions (which play a crucial role in muscle contraction).

Discuss how sarcomeres and Z lines relate to myofibrils.

Each myofibril consists of repeating subunits called sarcomeres that are aligned end to end along the length of the myofibril, connected to one another by protein discus called Z lines.

Discuss how thin and thick filaments relate to sarcomeres.

Within the sarcomere lies a precise arrangement of thin(actin) and thick(myosin) protein filaments. These interact with one another to contract the muscle fiber. 

• Each thin filament is anchored to a Z line at one end of the sarcomere

• Suspended between the thin filaments are thick filaments

• This arrangement gives the muscle fiber its striated appearance

List and discuss the two proteins that make up the thin and thick myofibrils.

Actin (thin) and Myosin (thick).

Discuss the role of dystrophin in muscle contraction.

Dystrophin binds thin filaments to proteins in the plasma membrane, which in turn are attached to extracellular proteins that surround the muscle fiber. This helps to distribute the forces generated during muscle contraction so the fiber doesn’t tear itself apart.

Certain types of muscular dystrophy are caused by the inability to produce functioning dystrophin.

Discuss how tropomyosin relates to muscle contraction.

Tropomyosin is one of two accessory proteins (tropomyosin and troponin) that regulate contraction. They lie atop the actin.

Discuss the sliding filament mechanism and how it relates to muscle contraction.

The sliding filament mechanism is when the molecular architecture of thin and thick filaments allow them both to grip and slide past one another, shortening the sarcomeres and producing a muscle contraction. 

• Each spherical actin protein has a binding site for the myosin head

• In a relaxed muscle cell, the binding sites on the actin are covered by the tropomyosin; stopping the myosin heads from attaching and the muscle from contracting.

• When the muscle contracts, tropomyosin moves aside and exposes the binding sites on the actin. Myosin heads then bind to these sites and temporarily link the thick and thin filaments. Those heads then flex, pulling on the thin filaments and causing them to slide a tiny distance along the thick filament. They then pull the thin filaments to the middle of the sarcomere. 

  • Because the thin filaments are attached to the Z lines at the ends of the sarcomere, this movement shortens it. All of the sarcomeres of the entire muscle fiber shorten simultaneously, so the whole muscle fiber contracts.  

  • Myosin heads then release the thin filament and reattach farther along before flexing and shortening the muscle fiber a little more (heave ho). This cycle will repeat for the duration of the contraction. 

Compare and contrast the ATP use for brief high intensity muscle exertion and prolonged low intensity muscle exertion.

ATP is the fuel for muscle contraction, meaning that it will be depleted very fast by it. Prolonged low intensity results in lower loss of ATP (?)

Discuss how the intensity of a muscle contraction is controlled.

To control the force, distance and duration of muscle contraction: 

• A single motor neuron typically synapses with several muscle fibers in a single muscle. 

  • A motor neuron and all the muscle fibers that it innervates are called a motor unit. These vary in size. 

    • In muscles for fine control (fingers, eyes) motor units are small. A single motor neuron may synapse on just a few muscle fibers. 

    • In muscles used for large-scale movements, such as those of the thigh or butt, motor units are large. A single motor neuron may synapse on dozens or even hundreds of muscle fibers.

Define and discuss “motor units”

A motor unit is a motor neuron and all the muscle fibers that it innervates.

Explain how the nervous system controls the strength of muscle contractions.

The nervous system controls the strength of muscle contraction by varying both the number of muscle fibers stimulated and the frequency of action potentials in each fiber. 

• Because motor neurons synapse on multiple muscle fibers in any given muscle, and because the muscle fibers are attached to one another and to the muscle’s tendons, a single action potential in a single motor neuron will cause contraction of the entire muscle.  

  • Large contractions are caused by a single motor neuron by firing multiple action potentials in rapid succession.

  • Firing multiple motor neurons that innervate fibers in the same muscle will also cause a large contraction of the muscle.

  • Finally, rapid firing of all the motor neurons that innervate all the fibers in the muscle will cause a maximal contraction.

Compare and contrast slow-twitch and fast-twitch muscles.

Slow twitch and fast twitch fibers have different forms of myosin, causing them to contract slowly and more rapidly, respectively. 

Slow twitch 

• Fibers contract with less fiber than fast-twitch, but keep contracting for a very long time. 

• Have lots of mitochondria and a plentiful blood supply that provides oxygen for cellular respiration in the mitochondria

• Slow-twitch fibers are also thin

  • Packed with mitochondria and have fewer myofibrils, but they trade decreased power for rapid diffusion of oxygen in → wastes out. 

• They produce abundant ATP and have fewer filaments to use it up, resisting fatigue. 

• Known as “dark meat”

Fast-twitch

• Have smaller blood supply, fewer mitochondria, and a larger diameter.

  • Thick fibers with relatively few mitochondria have more myofibrils and are therefore more powerful.

• Extreme versions of fast twitch fibers use mostly glycolysis for energy production, which doesn’t require oxygen but supplies a lot less ATP than cellular respiration does.

• Fatigue more rapidly than slow-twitch fibers, used for extreme bursts of energy, but not longevity. 

• Known as “white meat”     

List the four main functions of the digestive system.

• Ingest food

• Break down food into small molecules that can be absorbed through the plasma membrane

• Absorb nutrient molecules

• Eliminate non digestible food through excretory system

Compare and contrast intracellular and extracellular digestion.

Extracellular digestion 

• Breaks down food within the digestive tract

Intracellular digestion

• Digestion is completed within the cell by lysosomes and hydrolytic enzymes.

Compare and contrast complete and incomplete digestive systems (tracts)

Incomplete (Sac)

• A single hole for bringing in and expelling material

• A good example of this would be a planarian 

  • Digestive tract begins with mouth and muscular pharynx and then the gastrovascular cavity branches throughout the body

  • Notable for lack of specialized parts

Complete (Tube within a tube)

• Mouth and anus (separate holes)

• A good example of this would be an earthworm

  • Surface area of tract is often increased for nutrient absorption

    • Intestinal fold - typhlosole

Explain the advantage of increasing surface area in the digestive tract and list two structures that help to increase the surface area.

The advantage of increasing surface area in the digestive tract is that it helps with nutrient absorption. Two structures that help to increase the surface area would be the Typhlosole, which is an intestinal fold, and the villi.

Compare and contrast continuous versus discontinuous feeding organisms explaining what structures are required for each.

Continuous feeders

• Constantly feeding on something, never stops eating. 

• Example of this is a clam

  • Particles deposited on gills. 

  • Do not need food storage area

Discontinuous Feeders

• Needs to catch prey, not constantly eating.

• Example of this is squid

  • Uses tentacles to seize prey and allow the beaklike jaws to pull pieces into the mouth with the radula. 

  • Need food storage area (stomach)

Provide a representative organism from each of the following feeding groups: omnivores, herbivores, and carnivores. In addition, list adaptations that these organisms possess which allow them to use their particular food source.

Omnivores

• Variety of specializations to accommodate both vegetation and meat (intermediately long intestinal tract)

• Humans

  • Have a combination of sharp and flat teeth

  • Medium length intestinal tract

Carnivores

• Use pointed incisors and enlarged canines to shear off pieces small enough to swallow (relatively short intestinal tract)

• Wolves

  • Possess sharp front teeth for cutting and tearing meat

  • Simple stomachs and relatively short small intestines

Herbivores

• Often have incisors for clipping, premolars and molars for grinding (very long intestinal tract). 

• Sheep

  • Broad and flattened teeth for grinding plant material 

  • Complex stomachs and long intestines since plant material is hard to break down.

List the two major ways humans break down food.

• Mechanical digestion (chewing and churning)

• Chemical digestion (use of enzymes to break down food)

List the enzyme produced by the salivary glands and describe what it works to break down.

Saliva secretes salivary amylase, which breaks down starches into glucose. 

• Begins with starch (amylose) digestion 

  • Starch + Water + Salivary amylase → Maltose + glucose

Describe the function of the tongue during digestion.

The tongue is composed of striated muscle which mixes chewed foods with saliva, forming the mixture into bolus.

Define the term “bolus”.

Bolus is a mixture of food ground up by mechanical mixing mixed with enzymes to move down to the stomach for further digestion.

Describe the pathway of food from the mouth to the stomach listing all of the structures discussed in lecture.

Mouth/Tongue/Teeth → Pharynx → Esophagus → Stomach → Small intestine (duodenum, pancreas, liver, villi) → Large intestine → Anus

List the structures that keep food from entering the respiratory system.

The soft palate closes off the nasopharynx, keeping the food from getting in the nasal respiratory passages. The epiglottis covers the opening into the trachea (glottis), blocking air passages.

Define “peristalsis” and describe how this musculature action aids the movement of bolus.

Peristalsis is the rhythmical contraction of the smooth muscles of the digestive system that move food contents in tubular organs, pushing it down into the stomach.

List the components of the stomach and explain why stomach acid does not eat through the stomach wall.

Stomach wall 

• Possesses deep folds, which disappear as the stomach fills to an approximate capacity of one liter.

• Epithelial lining of the stomach possesses millions of gastric pits, leading to gastric glands (releases pepsin to break down proteins called peptides). 

  • This is why stomach acid does not eat through the wall

Describe an ulcer and explain how they can occur.

An ulcer is developed when the lining of the stomach has been exposed to pepsin, creating a hole in that lining. Excess use of painkillers, alcohol, or smoking are implied to be causes of ulcers.

Define the term “chyme”.

Chyme is defined as the food mixing with gastric juices. Whenever the pyloric valve between the stomach and small intestine relaxes, a small quantity of chyme passes through the opening of the small intestine called the duodenum.

List the function in the small intestine for each of the following organs: duodenum, pancreas, and liver.

Duodenum 

• Opening into the small intestine, allowing chyme to enter. 

• Secretes enzymes, molecules and hormones to neutralize the acidic conditions of chyme.

Pancreas

• Sends secretions to the duodenum

• Produces pancreatic juice and digestive enzymes

  • Pancreatic amylase digests starch to maltose

  • Trypsin digests protein to peptides

  • Lipase emulsifies and digests fat droplets to glycerol and fatty acids.

  • Secretin causes cells of the duodenum to produce water and bicarbonate which neutralizes the acidic chyme.

Liver

• Sends secretions to the duodenum

• Produces bile which is stored in the gallbladder.

  • Contains bile salts that break up fat into fat droplets via emulsification

Define the term “emulsification”.

Emulsification is when large substances are broken down into smaller droplets. One example is dropping oil into a hot pan, the big droplet will break down into smaller droplets.

List the exocrine and endocrine functions of the pancreas.

Exocrine 

• Exocrine gland when it produces and secretes pancreatic juices into the duodenum

Endocrine 

• Endocrine gland when it produces insulin and glucagon to be secreted into the blood. 

Discuss the pH of the stomach and the intestines explaining how this regulates enzyme functions and prevents disease.

The stomach should be very acidic, pH wise, so that it can digest nutrients properly. It becomes more basic as it enters the small intestine, chyme becomes neutralized by secretions from the pancreas.

List eight functions of the liver. (Listed all for ease)

• Removes poisonous materials and detoxifies them

• Stores iron and vitamins A, D, E, B12, and K

• Produces plasma proteins

• Regulates cholesterol 

• Produces bile

• Removes bilirubin

• Stores glucose

• Produces Urea

Describe the hepatic portal system providing its major functions.

• Small intestine absorbs products of digestion

• Nutrient molecules travel in hepatic portal vein to liver

• Liver monitors blood content

• Blood enters general circulation by way of the hepatic veins, which empty into the inferior vena cava. 

List the components of the large intestine and provide their functions.

Cecum 

• Has small projection named the vermiform appendix

Colon

• Subdivided into ascending, transverse, descending, and sigmoid colon. 

Rectum 

• Passage to the anal canal

Anal Canal 

• Opens to anal canal/anus

List and describe the macromolecules that all animals need for energy and body structures.

All animals need carbohydrates, proteins, and lipids.

List and describe what products are broken down for digestive absorption for carbohydrates, lipids, and proteins.

• Carbohydrates → Monosaccharides

• Proteins → Amino acids

• Peptides + Lipids → Monoglycerides