Biology-Animal Form and Function 2 Flashcards
Liver Functions
Vitamin Storage
stores vit A, D, B12.Also stores iron by combining it with apoferritin => ferritin
Portal vein
all carbs absorbed into blood are carried by portal vein to the liver
Liver Function
Glycogenesis
formation of glycogen
Liver Function
Glycogenolysis
if blood glucose levels decrease => glycogen is broken down to glu for release
Liver Function
What happens to blood acidity, when the liver mobilizes fat or protein for energy?
blood acidity increase (ketone bodies are produced => ketosis/acidosis results)
Liver Function
Blood supply
hepatic portal vein supplies blood as does hepatic artery (oxygenates liver); blood leaves via hepatic vein => vena cava
Liver Function
Digestive and Transport
Digestive: produces bile
Transport: synthesizes blood plasma proteins important in clotting
Nervous System
Neuron vs. Endocrine
neuronal communication is rapid/direct/specific. Hormonal is slower/spread through body/affects many cells/tissues in different ways/longer lasting
Nervous System
Neuron
consists of several dendrites, single (branched) axon, and cell body
Nervous System
Dendrites
receive information and transfer it TO cell body
Nervous System
Axon
transfers impulses AWAY from cell body
Nervous System
Glial Cells
nervous tissue support cells; capable of cellular division
- **oligodendrocytes **produce myelin in CNS; wrap many times around axons
-
schwann cells produce myelin in PNS. Myelin sheaths act as insulators and are separated by **nodes of Ranvier. Intead of traveling continuously down axon, action potential jumps from node to node (salutatory conduction**), speeding up impulse
- only vertebrates have myelinated axons. Myelinated axons appear white (white matter); neuronal cell bodies gray (gray matter)
- other glial cells include: microglia (phagocytes of the CNS), ependymal (use cilia to circulate CSF), satellite cells (support ganglia- groups of cell bodies in PNS), and astrocytes (physical support to neurons of CNS; maintain mineral and nutrient balance
Nervous System
3 Types of Neurons
- **Sensory (afferent) **receive initial stimulus (Ex. neurons in retina of eye) A => BRAIN
- **Motor (Efferent) **stimulate effectors, target cells that elicit some response (Ex. neurons may stimulate the muscles, sweat glands, or cells in stomach to secrete gastrin.) BRAIN => M
- Association (Interneuron)- located in spinal cord and brain - receive impulses from sensory and send impulses to motor neurons. They are integrators, as they evaluate impulses for appropriate response. ~99% of nerves are interneurons
Nervous System
Transmission of a Nerve Impulse (Unstimulated Neuron)
the membrane of an unstimulated neuron is polarized, although a high [Na+] is present outside of cell and a high [K+] is present inside the cell (the inside is actually negative due to the negatively charged proteins and nucleic acids residing in the cell). Additionally, neuron membranes are selectively permeable to K+ as opposed to Na+, which helps to maintain the polarization
Nervous System
Transmission of a Nerve Impulse
- Resting Potential- normal polarized state of neuron, -70 mV
- Action Potential- stimulus => gated ion channels let Na+ into cell, depolarizing it. If the threshold level is reached (~-50mV), it will cause an action potential that will result in opening of (voltage gated) Na+ channels down the entire length of the neuron. All or nothing event!
- **Repolarization- **in response to Na+ flow in, more gated ion channels let K+ out of the cell, restoring polarization-but the Na+ are IN and the K+ are OUT
- **Hyperpolarization **By the time the channels close, too much K+ is released (-80 millivolts)
- **Refractory period **Neuron will NOT respond to new stimulus until Na+/K+ pumps return the ions to their resting potential locations (outside/in, respectively) if absolute. If relative, abnormally large stimuli can create an AP. Note that refractory period is what prevents an AP from moving backwards, even though ions are theoretically rushing in and diffusing in both directions
Nervous System
Transmission of Nerve Impulse NOTE
from -70 up to threshold (or -70 downward) is the **graded potential **that cannot travel, but it can potentially (if it surpasses threshold) open the voltage gated channels and this part is the action potential that travels by opening other voltage gated. The other gated types cannot spread unless they trigger this AP. Also note that AP is all or nothing, so strength of a neural signal is based on other factors (frequency of AP firing or how many neuron cells contribute AP’s, etc).
Nervous System
Transmission across synapse
presynaptic cell => postsynaptic cell
I. Electrical- action potential travels along membranes of gap junctions (less common); fast; cardiac and visceral smooth muscle
II. Chemical- most typical in animal cells; unidirectional (unlike electrical)
- Ca2+ gates open- depolarization allows Ca2+ to enter cell
- Synaptic vessels release neurotransmitter- influx causes release into cleft
- Neurotransmitter binds with postsynaptic receptors. Diffusion (via Brownian motion) and binding
- **Postsynaptic membrane is excited or inhibited. **Two possible outcomes:
- Na+ gates open, membrane is depolarized => excitatory postsynaptic potential (EPSP), if threshold potential is succeeded, action potential is generated
- K+ gates open, membrane becomes hyperpolarized => inhibitory postsynaptic potential (IPSP)…it becomes more difficult to generate action potential
- Neurotransmitter is degraded and recycled. Broken down by enzymes in cleft and recycled.
Nervous System
Acetylcholine (neurotransmitter)
secreted at neuromuscular junctions (gaps between motor neurons and muscle cells) => muscle contraction/relaxtion. Inhibitory everywhere else.
a. parasympathetic nervous system
Nervous System: Neurotransmitters
Epinephrine, norepinephrine, dopamine, and serotonin (5HT)
AA derived, secreted between neurons of CNS
a. sympathetic nervous system
Nervous System: Neurotransmitter
Gamma aminobutyric acid (GABA)
inhibitory neurotransmitter among brain neurons
Nervous System
Diameter and mylineated axons
Greater diameter and more heavily myelinated axons will propagate faster impulses (greater diameter because less resistance to “flow” of ions- think water through a large pipe vs. a small one, and myelinated because of saltatory conduction; the Na doesn’t gradually defuse outward [charge leakage] at every successive AP requiring new Na to rush in to keep the impulse going; it can’t leak out of myelin wrapped sections so it drives straight from node to node
Nervous System
Synaptic vesicles
synaptic vessels fuse w/ presynaptic membrane => neurotransmitter => postsynaptic
Nervous System
Neurotransmitter
may be taken back into nerve terminal (active transport), degraded synaptic clef enzymes (recycle back to presyn), or diffuse out of the synapse
Central Nervous System
Central Nervous System consists of what two parts?
Brain and spinal cord
Central Nervous System
Brain
outer grey matter (cell bodies) and inner white matter (axons);
- forebrain largest/most important brain region. Contains cerebral cortex (processes sensory input/ important for memory and creative thought), olfactory bulb (smell), **thalamus **(relay for spinal cord and cerebral cortex), hypothalamus visceral function (water balance, blood pressure, and temp. regulation, hunger, thirst, sex)
- **midbrain **relay center for visual/ auditory impulses; motor control
- **hindbrain **posterior part of brain; cerebellum (maintainence of balance, hand-eye coord, timing of rapid movements), pons (relay center to allow communication b/w cortex and cerebellum), medulla oblongata (breathing, heart rate, gastrointestinal activity)
- brainstem consists of midbrain + medulla oblongata + pons. Connects the cerebrum with the spinal cord
Central Nervous System
Cerebrum
largest part of brain w/ two hemispheres connected by corpus callosum (thick nerve bundle); contains sensory, motor, association areas
- Divided by lobes:
- frontal (conscious thought; voluntary skeletal muscle movement)
- partietal (sensory areas-temperature, touch, pressure, pain)
- temporal (sensory-hearing and smelling)
- occipital (sensory-vision)
- has outer portion (cerebral cortex- gray matter
- inner portion (medulla-white matter)
Peripheral Nervous System
Peripheral Nervous System (PNS)
consists of sensory branch and motor branch. Motor consists of somatic and autonomic nervous systems:
- **somatic **responsible for VOLUNTARY movement of skeletal muscles
- **autonomic **involuntary movement; innervates cardiac and smooth muscle
- sympathetic- flight or flight (higher BP and HR)
- Parasympathtic- rest and digest; non-emergency (lower HR, digestion, relaxation, and sexual arousal)
Reflex Arc
rapid, involuntary response to stimulus involving 2 to 3 neurons, but brain DOES NOT integrate the sensory and motor activities…instead synapse in spinal cord.
ex. knee-jerk (patellar) reflex
Sensory Receptors
- mechanoreceptors (touch)
- thermoreceptors (temperature)
- nociceptors (pain
- electromagnetic receptors (light)
- chemoreceptors (taste, smell, blood chemistry)
respond strongly to own stimuli, weak to others; neural pathways separate + terminate in CNS
*all nerves not directly inside the brain or spinal cord are all part PNS. Cranial and spinal nerves come OUT of those structures and are part of PNS
Eye
Eye
**cornea **(focuses light) => **pupil **(diameter controlled by iris {pigmented})=> **lens **(controlled by ciliary muscles; focuses img) => **retina **(light sensitive cells)
Eye
cones
high-intensity illumination; sensitive to color
Eye
Rods
low intensity; important in night vision; no color
- Rhodopsin (rod pigment) is struck by photons from light, causing hypolarization transduced into neurl AP sent to brain
- photoreceptor cells synapse to bipolar cells => ganglion cells => axions of ganglion cells bundle to optic nerve
- point at which optic nerve exits is blind spot (no photoreceptors there)
Eye
Fovea
densely packed with cones; important for high acuity vision
Eye
Vitrous Humor
Aqueous Humor
(jelly like, maintains eye shape and optical properties)
(anterior chamber, eye produces it)
Eye
Eye disorders
- myopia-nearsightedness
- hyperopia-farsightedness
- astigmatism-irregularly shaped cornea
- cataracts-lens becomes opaque => light cannot enter
- glaucoma- increase in pressure of eye due to blocking of outflow of acqueous humor
Ear
Ear
structure is 3 main parts: outer, middle, and inner ear; tranduces sound energy into impulses
Ear
outer ear
auricle/pinna (what we think of as the ear) and auditory canal; direct sound into external auditory canal => then goes to middle ear
Ear
middle ear
amplifies sound; tympanic membrane (eardrum) begins the middle ear and vibrates at the same frequency as incoming sound => ossicles (malleus, incus, and stapes) => inner ear
Ear
Inner Ear
wave moves through the cochlea (vibration of ossicles exert pressure on fluid). As wave moves through pressure alternates, moving the vestibular membrane in and out; this movement is detected by hair cells (not actual hair but specialized stereocilia) of the organ of Corti => transduced neural signal => action potential
- inner ear also has **semicircular canals **responsible for balance (fluid + hair cells sense orientation + motion)
Muscular System
Muscle contraction
may result in movement, stabilization of position, movement of substances throughout body, generation of body heat
Muscular System
Organization of Vertebrate Skeleton
- Axial skeleton basic framework (skull, vertebral column, rib cage)
- **Appendicular skeleton **bones of appendages, pectoral, and pelvic girdles
- **Bone organization **
- **Sutures **immovable joints (holds together bones of skull)
- **Moveable Joints **bones that move relative to each other
- **ligaments **bone-to-bone connectors; strengthen joints
- **tendons **muscle-to-bone; bend skeleton at moveable joints
- **Origin **point of attachment of muscle to *stationary *bone
- **Insertion **point of attachment of muscle to bone that moves
- **Extension **= straightening of joint
- **Flexion **= bending of joint
Muscular System
Joint types
- Fibrous- connect bones w/o allowing any movement (ex. skull, pelvis, spinous process, and vertebrae)
- Cartilaginous- bones attached by cartilage, allow little movement (ex. spine and ribs)
- Synovial- allow for much more movement; most common; filled with synovial fluid which acts as a lubricant (ex. carpals, wrist, elbow, humerus and ulna, shoulder and hip joints, knee joint)
Muscular System
Muscular System
consists of contractile fibers held together by connective tissue
- **Skeletal muscle **(striated muscle)- voluntary movement, fibers are **multinucleated **cells
- myofibrils: filaments divided into sarcomeres
- sarcomeres: individual contractile units separated by a border (Z-line)
- sarcoplasmic reticulum- stores Ca2+; surrounds myofibrils
- sarcoplasm-cytoplasm
- sarcolemma- plasma membrane of muscle cells; can propagate action potential
- invaginated by T-tubules (transverse)- channels for ion flow
- wraps several myofibrils together to form a muscle cell/muscle fiber
- mitochondria- present in large amounts of myofibrils
Muscular System
Muscle fibers
muscle cells
Muscular System
myofibrils
consist of two types of filaments:
- Thin- made of 2 strands of actin arranged in double helix. Along the length of helix are troponin and tropomyosin molecules that cover special binding sites on the actin
- Thick- consist of groups of the filamentous protein myosin. Each myosin filament forms a protruding head at one end. An array of myosin filaments possesses protruding heads at numerous positions at both ends
Muscular System
Sarcomere
is composed of thin filaments (actin) and thick filaments (myosin)
- **Z line **boundary of a single sarcomere; anchor thin filaments
- **M line **center of sarcomere
- I band region containing thin filaments (actin) only (on ends, only purple)
- H zone region containing thick filaments (myosin) only (in middle, only green)
- **A band **actin and myosin overlapping (one end of overlap to other end of overlap)
- **H **and **I **reduce during contraction, while **A **does NOT
Muscular System
Muscle Contraction
Stimulation Process of Sliding Filament Model- “all-or-nothing” response
- Action Potential of neuron releases acetylcholine when meets neuromuscular jxn
- AP then generated on sarcolemma and throughout T-tubules
- Sarcoplasmic reticulum releases Ca2+
- Myosin cross bridges form-result of Ca2+binding to troponin on actin helix
Muscular System
Sliding Filament Model
- **ATP binds to myosin head **converted to ADP + Pi, which remain attached to head
- **Ca2+exposes binding sites on actin **binds troponin => tropomyosin exposes attachment sites
- Cross bridges between mysoin heads and actin filaments form
- **ADP + Pi are released **=> sliding motion of actin brings **Z lines **together (contraction, power stroke)
- **New ATP attaches to myosin head, causes cross bridges to unbind - **new phosphorylation breaks cross bridge
w/o new ATP, the cross bridges remain attached to myosin head…this is why corpses are stiff
Strength of contraction of single muscle fiber cannot be increased, but strength of overall contraction can be increased by recruiting more muscle fibers
Muscular Response
Simple Twitch
response of a single muscle fiber to brief stimulus; latent, contraction, relax
- Latent period- time btw stimulation and onset of contraction; lag; AP spreads on sarcolemma and Ca2+ ions released
- Contraction
- Relaxation (absolute refractory period)- unresponsive to stimulus
Muscular Response
Summation and Tetanus
- Summation contractions combine and become stronger and more prolonged (repeated APs summate)
- **Tetanus **continuous sustained contraction; muscle cannot relax; will release if maintained (in tetanus, rate of muscle stimulation so fast that twitches blur into one smooth constant)
Muscular Responses
Tonus
state of partial contraction; muscle never completely relaxed
Muscular System
Smooth Muscle
mainly involuntary, ONE central nucleus; LACK striation; stimulated by autonomic nervous system (ex. lining of bladder, uterus, digestive tract, blood vessel walls, etc.) No sarcomere organization: intermediate filaments attached to dense bodies spread throughout cell. Thick and thin filaments attached to IFs, contract => IF’s pull dense bodies together => smooth muscle length shrinks.
Two types of smooth muscle:
- single-unit: aka visceral, connected by gap jxns, contract as single unit (stomach, uterus, urinary bladder)
- multi-unit: each fiber directly attached to neuron; can contract independently (iris, bronchioles, etc)
in addition to neuronal response, can respond to: hormones, change in pH, O2, CO2 levels, temperature, [ion]
Muscular System
Cardiac Muscle
striated appearance (sarcomeres); one or TWO central nuclei; cells separated by intercalated discs that have gap jxn to allow AP’s to chain flow via electricl synapse; involuntary; lots of mitochondria
both smooth and cardiac muscle are myogenic- capable of contracting w/o stimuli from nerve cells
Muscular System
Muscle fibers and motor units
muscle fibers of single muscle don’t all contract at once. Single neuron innervates multiple muscle fibers (collectively called **motor **unit). Usually: smaller motor units activated first, then larger ones as need => smooth increase in force. Fine movement uses smaller motor units.
Muscular System
Skeletal muscle
attached to bones and causes movements of the body
- Type I: slow-twitch, lots of myoglobin, lots of mitochondria, aerobic endurance
- Type IIA: fast-twitch, endurance by not as much as type 1 (anaerobic endurance)
- Type IIB: fast-twitch, low myoglobin, lots of glycogen, power.
Skeletal muscle generally doesn’t undergo mitosis to create new muscle cells (hyperplasia), but will increase in size (hypertrophy)
Muscular System
Movement in lower forms (unicellular locomotion)
- protozoans and primitive algae-cilia or flagella by means of power stroke and recovery stroke
- amoeba- extend **pseudopodia; **advancing cell membrane extends forward
Muscular System
Movement in lower forms (Invertebrate)
-
hydrostatic skeletons
-
flatworms- bilayered muscles, longitudinal and circular, contract against hydrostatic skeleton
- contraction causes hydrostatic skeleton to flow longitudinally, lengthening animal
- segmented worms (annelids)- advance by action of muscles on hydrostatic skeleton
- bristles in lower part of each segment, setae, anchor worm in earth while muscles push ahead
-
flatworms- bilayered muscles, longitudinal and circular, contract against hydrostatic skeleton
Skeletal System
Exoskeleton
arthropods- insect exoskeletons composed of hard chitin, necessitates **molting **for growth
Skeletal System
Vertebrate Skeleton
comprised of an endoskeleton. Two major components are **cartilage **and bone
Skeletal System
Vertebrate Skeleton (Cartilage)
avascular connective tissue; softer and more flexible; (ex. ear, nose, larynx, trachea, joints
- 3 types:
- hyaline- most common, reduced friction/absorbs shock in joints
- fibrocartilage
- elastic
- from mesenchyme tissue => chondrocytes => produce collagen (present in tissue as triple helix w/ hydroxyproline and hydroxylysine, ground substance, and elastin fibers. Composed primarily of collagen, receive nutrients via diffusion
Skeletal System
Vertebrate Skeleton (Bone)
connective tissue; hard/strong, while elastic and lightweight
- Functions: support of soft tissue, protection of internal organs, assistance in body movement, mineral storage, blood cell production, and energy storage in form of adipose cells in marrow
Skeletal System
Bone
4 types of cells surrouned by extensive matrix:
- **Osteroprogenitor/Osteogenic: **differentiate into osteoblasts
- **Osteoblasts: **secrete collagen and org. cmpds upon which bone is formed. Incapable of mitosis. As matrix release around them => enveloped by matrix => differentiate into osteocytes (remember, Blast means Build)
- **Osteocytes: **incapable of mitosis; exchange nutrients and waste material w/ blood
- **Osteoclasts: **resorb (destroy) bone matrix, releasing minerals back to blood. Develop from monocytes
Skeletal System
Structure (Compact bone)
highly organized, dense bone that doesn’t appear to have cavities from outside: osteoclasts burrow tunnels (Haversian canals) throughout.
- Osteoclasts are followed by osteoblasts, which lay down new matrix onto tunnel walls forming concentric rings (lamellae).
- Osteocytes trapped between the lamella (lacunae) exchange nutrients via canaliculi.
- The Haversian canals also contain blood + lymph vessels and are connected by Volkmann’s canals. Entire system of lamellae+ Haversian canals is called an osteon (Haversian system).
- Compact bone is filled w/ yellow bone marrow that contains adipose cells for fat storage.
Skeletal System
Structure (spongy [cancellous bone])
less dense and consists of an interconnecting lattice of bony spicules (trabeculae); filled w/ red bone marrow (site of RBC development)
- Bone growth occurs at cartilaginous epiphyseal plates that are replaced by bone in adulthood. Bone increases in length but also in diameter along the diaphysis as well.
- Most of the Ca2+ in body is stored in bone matrix as hydroxyapatite
- bones can be made from a combination of compact and spongy
Skeletal System
Bone formation
during FETAL state of development
- endochonral ossification- cartilage => bone (EX: long bones; limbs, fingers, toes)
- intramembranous ossification- undifferentiated connective tissue replaced by bone (EX: flat bones; skull, sternum, mandible, clavicles)
Skeletal System
Haversian canal
contains bones, nerves, and blood supply
Integumentary (Skin) System
Skin Functions
- Thermoregulation helps regulate body temp
- **Protection **physical barrier to abrasion, bacteria, dehydration, many chemicals, UV radiation
- **Environmental sensory input **skin gathers info about environment by sensing temp, pressure, pain, touch
- **Excretion **water and salts excreted through skin
- **Immunity **specialized cells of the epidermis are components of immune system
- **Blood Reservoir **vessels in the dermis hold up to 10% of the blood in resting adults
- **Vit D synthesis **UV radiation activates skin molecule that is a precursor to Vit D
Integumentary (Skin) System
Epidermis
superficial; avascular epithelial tissue (depends on dermis for oxygen and nutrients). Layers from top down:
-
Stratum corneum 25-30 dead layers; filled w/ keratin and surrounded by lipids
- Lamellar granules make it water repellent
- **Stratum lucidum **only palms and soles of feet, and fingertips; 3-5 layers, clear/dead
- **Stratum granulosum **3-5 layer of dying cells; lamellar bodies release hydrophobic lipids
- **Stratum spinosum **strength and flexibility; 8-10 layers held together by (desmosomes-keratin involving adhesion proteins)
- **Stratum basale (germinativum) **contains Merkel cells and stem cells that divde to produce keratinocytes; attached by basement membrane
- The keratinocytes are pushed to the top layer. Rise =>accumulate keratin and die => lose cytoplasm/nucleus/ other organelles => at outermost layer of skin, slough off body
Integumentary (Skin) System
Cells of Epidermis
- Keratinocytes: produce the protein keratin that helps waterproof the skin
- **Melanocytes: **transfer skin pigment melanin to keratinocytes
- **Langerhans cells: **interact with helper T-cells of immune system
- Merkel cells: attach to sensory neurons and fxn in touch sensation
Integumentary (Skin) System
Structure of Skin
Epidermis, Dermis, Hypodermis (subcutaneous)
Integumentary (Skin) System
Dermis
primarily connective tissue; collagen and elastic fibers; contains hair follicles, glands nerves and blood vessels
- Papillary region- top 20%
- Reticular region- dense connective tissue, collagen and elastic fiber; packed with oil glands, sweat gland ducts, fat, and hair follicles; provides strength, and elasiticity (stretch marks are dermal tears)
Integumentary (Skin) System
Hypodermis (subcutaneous)
not part of skin; areolar and adipose tissue; fat storage; pressure sensing nerve endings; passage for blood vessels
Integumentary (Skin) System
Glands of the Skin
- Sebaceous (oil) glands- connected to hair follicles; absent in palms and soles
-
Sudoriferous (sweat) glands
- Eccrine (most of the body)- regulate temperature through perspiration; eliminate urea
- apocrine- armpits, pubic region, and nipples; secretions are more viscous
- Ceruminous (wax) glands- found in ear canal; produce wax-like material as barrier to entrance
- Mammary (milk) glands
Immune System
Nonspecific 1st line of defense
innate immunity- generalized protection
- _Skin: _physical and hostile barrier covered with oily and acidic (pH 3-5) secretions from sweat glands
- Antimicrobial proteins: lysozyme (saliva, tear) which breaks down cell wall of bacteria
- Cilia: line the lungs serve to sweep invaders out
- Symbiotic bacteria: digestive tract and vagina outcompetes many other organisms
- Gastric Juices: stomach kills most microbes
Immune System
Nonspecific 2nd line of defense
innate
- Phagocytes: leukocytes (WBC’s) engulf pathogens by phagocytosis (neutrophils and monocytes- enlarge into macrophages). Other WBCs called **natural killer cells (NK cells) **attack abnormal body cell-tumors or pathogen-infected
- Complements: 20 complement proteins; help attract phagocytes to foreign cells and help destroy by promoting cell lysis
- Interferons: secreted by cells invaded by viruses/pathogens that stimulate neighboring cells to produce proteins to defend against virus
- Inflammatory- series of non-specific events that occur in response to pathogens. EX: when skin is damaged and bacteria enter body
Immune System
Nonspecific 2nd line of defense (Inflammatory)
- Histamine: is secreted by basophils (white blood cells found in CT) => causes vasodilation
- Vasodilation: stimulated by histamine, increases blood supply to area- increase in temperature that stimulates WBCs and can kill pathogens
- Phagocytes: attracted to injury by chemical gradients of complement, engulf pathogens and damaged cells.
- Complement: helps phagocytes engulf foreign cells, stimulate basophils to release histamine, and help lyse foreign cells
Immune System
Basophils
release histamines for inflammatory response
Immune System
Types of WBCs (leukocytes)
all WBC’s originate form bone marrow but some multiply and become non-naive in the lymph node (lymph drainage acts as a sewer system of antigens; cell recognizes antigen, goes from naive => activated; multiplies
- Phagocytes
- Lymphocytes
- Basophils
Immune System
Phagocytes
engulf foreign particles/bacteria/dead or dying cells
- **neutrophils **fxn in destruction of pathogens in infected tissues; drawn to infected or injured areas by chemicals in process called chemotaxis; slip between endothelial cells of capillary (into tissue) via diapedesis
- **monocytes **move into tissues (diapedesis) where they develop into macrophages (which phagocytize cell debris + pathogens, are a professional antigen-presenting cell)
- **eosinophils **work collectively to surround and destroy multicellular parasites
- **dendritic cells **responsible for the ingestion of pathogens and stimulate acquired immunity ( “main function as APCs that activates T-lymphocytes”)
- **mast cells **fxn in allergic response; inflammatory response (histamine release), anaphylaxis
Immune System
Specific 3rd line of defense
immune response-targets specific antigen; acquired immunity- develops after body has been attacked
- Lymphocytes
- T cells (foreign)
Immune System
Specific 3rd line of defense (lymphocytes)
primary agents of immune response, leukocytes that originate in bone marrow but concentrate in lymphatic tissues such as lymph nodes, thymus gland, and spleen
-
B cells (antibodies): originates and mature in bone marrow (B cell for bone); response to antigens. Plasma membrane of B cells contains **antigen receptor-antibodies **(immunoglobulins).
- are proteins; specific to each antigen; five classes (IgA, IgD, IgE, IgG, IgM-variation in Y-shaped protein-constant region and variable regions)
- antibodies inactivate antigens upon binding => mark for macrophage or natural killer cell phagocytosis, lysis by complement proteins, agglutination of antigenic substance, or chemical inactivation (if a toxin)
- When antigen bound to B cell => proliferation (2 copies) into daughter B cells (assisted by helper T) =>
- plasma cells: B cells that release specific antibodies that circulate in blood
- memory cells: long-lived B cells that do not release antibodies in reponse to immediate antigen invasion; instead, they circulate the body, proliferate, and response quickly (via antibody synthesis) to eliminate **subsequent **invasion by same antigen. (2ndary response-takes less time, ~5 days)
Immune System
T cells (foreign)
originates in bone marrow but matures in thymus gland (T for thymus). T cells have antigen receptors but do not make antibodies; they check molecules displayed by nonself cells. In the thymus, if a T cell binds to a self-antigen, it is destroyed. If not, released for work in lymphoid tissue. Discrimination of self and nonself are as follow:
- MHC markers on plasma membrane of cells distinguish between self and nonself
- When body cell is invaded by pathogen (nonself), it displays a combination of self and nonself markers. T cells interpret this as nonself
- Cancer cells or tissues transplant cells are often recognized as nonself by T cells due to the combination
Immune System
What happens when T cells encounter nonself cells?
They divide and produce 4 kinds of cells:
- **Cytotoxic T cells **killer T cells recognize and destroy by releasing perforin protein to puncture them (lysis)
- **Helper T cells **stimulate activation of B cells, cytotoxic T cells, and supressor T cells
- **Suppressor T cells **play neg. feedback role in immune system
- **Memory T cells **similar fxn to memory B cells
Immune System
Specific 3rd line of defense (Natural killer cells)
attack virus-infected cells or abnormal body cells (tumors)
Immune System
Clonal selection
when antigen bind to B cell or when nonself binds to T cell => divide into daughter cells, only B or T cells that bears effective antigen receptor is “selected” and reproduces to make clones
Immune System
Response of Immune System
Cell-mediated response and humoral (antibody-mediated) response
Immune System
Immune System Response (Cell-mediated)
effective against infected cells. Uses mostly T cells and responds to any nonself cell, including cells invaded by pathogens. Nonself cell binds T cell => clonal selection => chain of events:
- Produce **cytotoxic T cells (destroy) and ** helper T cells
- **Helper T cells **bind **macrophages **(macrophages engulf pathogens = whole is nonself)
- **Helper T cells then produce interleukins to stimulate proliferation of T cells and B cells **and macrophages
Immune System
Immune System Response (Humoral response [antibody-mediated response])
responds to *antigens or pathogens *that circulate in the lymph or blood (bacteria, fungi, parasites, viruses, blood toxins). Basically the B-cell stuff. Humor is body fluid and the following events:
a. B cells produce plasma cells
b. B cells produce memory cells
c. **Macrophage and helper T cells **(in cell-mediated of macrophages engulf-nonself) stimulate B cell production
d. General progression: Naive => Mature => Plasma => Antibody
Note that antibodies are released from plasma cells, are specific for an antigen, and a single B lymphocyte produces only one
Immune System
How do humans supplement natural body defenses by?
- Antibiotics: are chemicals derived from bacteria/fungi that are harmful to other microorganisms
- Vaccines: stimulate production of memory cells from inactivated viruses or weakened bacteria (artificially active immun)
-
Passive immunity: transferred antibodies from another individual- EX: newborns from mother
- Acquired immediately, but short-lived and non-specific
- Gamma globulin (blood containing antibodies)- can confer temporary protection against hepatitis and other diseases
Immune System
Immune System exposure to antigen and recap of humoral response
- First time immune system is exposed to an antigen => primary response, requires 20 days to reach full potential
- Recap of humoral response: imagine a bacterial infxn. 1st, inflammation. Macrophages + neutrophils engulf the bacteria. Interstitial fluid flushed into lymphatic system where lymphocytes are waiting in lymph nodes. Macrophages process + present bacterial antigen to B-lymphocytes. W/ help of helper-T, B differentiate into plasma and memory cells. Memory cells prepare for event of same bacteria ever attacking again (2ndary response); plasma cells produce antibodies released to blood to attack the bacteria.
Endocrine System
Endocrine
synthesize and secretes hormones into bloodstream
Endocrine System
Exocrine
secrete substances into ducts (ex. gall bladder) (Pancreas is both exo and endo)
- Sudoriferous (sweat), sebaceous (oil), mucous, digestive, mammary glands are examples
Endocrine System
Paracrine
cell signaling where target is nearby; Autocrine is cell signaling via hormone/chemical messenger that binds to receptors on same cell
Endocrine System
Prostaglandins
locally acting autocrine/paracrine lipid messenger molecules that have physiological effect (e.g. contract/relax smooth muscle)
Endocrine System
General characteristics of hormone
are transported throughout body in blood; small amount = large impact; slower effect
Endocrine System
Hormone Types
Peptide, Steroid, Tyrosine Derivatives
all hormones bind to receptors highly specific to them. Some hormones have receptors on almost all cells, some have receptors only on specific tissues. Hormone regulation can occur by increasing/decreasing # of these receptors in response to hormone amount
Endocrine System: Hormone Types
Peptide
synth’d in rough ER and modified in Golgi (requires vesicle to cross membrane), acts on surface receptors typically via secondary messengers (ex. Cyclic AMP)
- manufactured in rough ER as larger preprohormone => cleaved in ER lumen to prohormone => cleaved again (possibly modified w/ carbs) in Golgi to final form
- Receptor-mediated endocytosis: protein stimulates production of 2nd messengers (G-protein => cAMP-produced from ATP, IP3-produced from membrane phospholipids which triggers Ca release from ER)
- include (AP) FSH, LH, ACTH, hGH, TSH, prolactin; (PP) ADH and oxytocin; (PT) PTH; (PANCR) glucagon and insulin
Endocrine System: Hormone Types
Steroid
synth’d from cholesterol in smooth ER; hydrophobic = freely diffuse but require protein transport molecule to dissolve in blood; intracellular receptors
- direct stimulation: “steroid” diffuses past plasma membrane and binds receptors in cytoplasm => hormone and receptor transported to nucleus => binds activate portion of DNA
- includes glucocorticoids and mineralicorticoids of the Adrenal Cortex: cortisol and aldosterone; the gonadal hormones: estrogen, progesterone, and testosterone (estrogen and progesterone are also produced by placenta)
Endocrine System: Hormone Types
Tyrosine Derivatives
formed by enzymes in cytosol or on rough ER
- Thyroid hormones: lipid soluble; require protein carrier in blood; bind to receptors in nuclues
- Catecholamines: (epi and nonepi) water soluble; dissolve in blood; bind to receptors on target tissue and mainly act via 2nd messenger
- includes thyroid hormones (T3 andT4 aka thyroxine) and catecholamines formed in adrenal medulla: epi and norepi
Endocrine System:
Hypothalamus
monitors external environment and internal conditions of the body; contains neurosecretory cells that link the hypothalamus to the pituitary gland. Regulation of the pituitary = neg. feedback mechanims and by secretion of releasing and inhibiting hormones; secretes ADH (vasopressin) and oxytocin to be stored in posterior pituitary; also secretes GnRH (gonadotropin releasing hormone) from neurons, which stimulates anterior pituitary to secrete FSH and LH
