Test 4/Final Flashcards
pathogen
anything that causes disease. (microbes like bacteria or pollen, secretions like venom, non-self tissue, some cancer cells)
antigens
cell surface proteins that body recognize as non-self. pathogens have antigens.
WBC
protect the body against pathogens. some circulate through lymph, blood, and interstitial fluid and some are housed in lymph nodes, thymus gland, spleen, appendix, etc.
Innate immunity
born with this immunity, broad– any pathogen is targeted.
Innate immunity: first line of defense
Includes skin as a barrier, mucous membranes to trap, and secretions in mucous membranes with anti-microbial proteins. Stomach secretes acids.
Innate immunity: second line of defense
non-specific WBC attack. Ingest and destroy microbes. Neutrophils, monocytes (macrophages), dendritic cells, eosinophils, basophils
neutrophils
most abundant WBC, short lived
macrophages
develop from monocytes. large and long-lived
dendritic cells
stimulate acquired immune system
eosinophil
destroy multicellular parasites by releasing toxic enzymes.
basophils
contribute to inflammatory and allergic responses.
lysozymes
lysozymes work in macrophages and in saliva, tears, and mucous.
Interferons
limit intra-cellular spread of viruses.
complement proteins
result in lysis; also help trigger inflammation and activate acquired immunity
defensins
secreted by macrophages, attack pathogens
natural killer cells
attack virus-infected cells and cancer cells
inflammatory response
usually localized in response to injury. Causes swelling as fluid and immune cells leak out of blood
Invertebrate Innate defense system
amoeboid cells in echinoderms, insect exoskeleton, hemocytes in insect hemolymph function as WBC, they have little immune system memory
acquired immunity
develops over time in response to exposure to pathogens. Highly specific. Includes b and t cells.
How does blood access immune system structures?
Since the lymph system is closely tied to the circulatory, pathogens in blood and exposed to phagocytes and lymphocytes in the lymph system
antigen recognition
recognized by antigens. most pathogens have several antigens, so several different lymphocytes recognize and respond to it
epitopes
specific binding sites on all antigens
lymphocytes (b and t cells)
each lymphocyte only recognizes a single antigen, but the receptor molecules and recognition process are different b/w b and t cells.
constant vs. variable regions
constant regions have stable amino acid sequences from cell to cell while variable regions have different amino acid sequences
b-cell receptors and antigen recognition
are y-shaped and each branch has two parts called chains. Inner, heavy chain makes full Y while outer light chain is located on the branches of the Y. both chains are proteins linked by chem. bonds. Both chains have variable amino acid sequences that act as antigen binding sites and bind to epitopes.
t cell receptors
unbranched with alpha and beta chain chemically linked with a single antigen binding site at the terminus.
T cell antigen recognition
recognize antigen fragments that have been bound to a self-cell protein called MHC. Does not recognized intact antigens on intact pathogens.
MHC
major histocompatibility complex; bind to antigen fragments at surface of cell and T cells detect presented antigen+MHC complex. Very varied among individuals due to multiple alleles. Very rare for people to have the exact same MHC
Class 1 MHC
found in most nucleated cells and bind to antigen fragments if cell has been infected or is cancerous. Class 1 MHC antigen complexes are recognized by cytotoxic T cells and they then destroy the “sick” cell
Class II MHC
found in dendritic cells, macrophages, and B cells. Presents antigens from pathogens that have been engulfed by phagocytosis. Recognized by helper T’s and begin a cascade of event to control the infection
difference between b and t cell receptors
b cell receptors bind directly to antigen on intact pathogen and t cell receptors bind to MHC+antigen complex on self-cells.
lymphocyte overview
produced from stem cells in bone marrow, some mature in the bone marrow (b cells) and rest mature in thymus (t cells)
maturation of lymphocytes overview
the development of b and t cell receptors. Once mature they either stay in organs of lymph system or circulate throughout blood, lymph, and interstitial fluid
lymphocyte development steps
- generation of diversity
- testing and removal
- clonal selection
lymphocyte development step 1
generation of diversity: genes that code for the antigen receptors are randomly rearranged by enzymes. during differentiation of each B cell one variable segment is snipped out and attached to one joining segment.
If the coding gene has 40 variable segments and 5 joining segments, how many total combinations are possible?
200
V+J segment is attached via an ________ to the ___ segment that codes for the constant region of the light chain
intron, constant
what is the difference between heavy and light chain DNA coding
while the light segment has 40 Variable segments and 5 Joining segments, the heavy chain has more V segments
lymphocyte development step 2
Testing and removal: each new receptor is tested against self cells during development and migration into lymph system organs. Receptors that bind to self cells or self MHC molecules are eliminated or deactivated.
lymphocyte development step 3
clonal selection: each b and t cell has receptors that are specific to a single antigen. Incoming pathogens typically display several antigens, and when a lymphocyte receptor encounters a matching antigen the lymphocyte is activated. 2 clonal populations are formed: effector cells and memory cells
activation of a lymphocyte
stimulation of the lymphocyte to begin mitotic cloning.
effector cells
one type of clonal populations of a lymphocyte. They are short-lived and carry out immune system responses.
memory cells
long lived type of clonal lymphocyte. They remember the epitope
recombinase enzyme
randomly snip v segment and join to a j segment
helper t cells
almost all pathogens activate helper T cells. stimulate cytotoxic t cells and b cells. 2 types: naïve and memory
naïve helper t cells
activated by dendritic phagocytes; important in primary immune response
memory helper t cells
important in secondary immune response. activated by macrophages
cytotoxic t cell function
release proteins that perforate target cells and initiate apoptosis
b cell function
recognize and bind to specific intact pathogens. Also engulf some pathogens by phagocytosis. Some are activated by presence of pathogen and others through helper t cells. activated b cells form 2 clones- plasma cells and memory cells.
plasma cells
release antibodies
antibodies
each clonal b cell releases nearly a billion antibodies. 5 classes of antibodies are secreted attacking specific pathogens.
active immunity
generated when acquired immune system is activated. Memory cells are generated and confers long-term protection. Usually through exposure to pathogen or vaccination.
passive immunity
generated when antibodies alone are transferred, does not generate memory cells and offers short term protection. ex: antibodies cross placenta
allergic responses
Generated by IgE antibodies. hypersensitive response to allergenic antigens. antibody tails bind to mast cells and IgE accumulates on mast cell surface. Eventually allergen binds between 2 IgE and exposure causes massive histamine release causing dilation of blood vessels.
autoimmune diseases
immune system fails to distinguish self-cells. Ex: rheumatoid arthritis, diabetes, multiple sclerosis, lupus
immunodeficiency diseases
immune system fails. Can be genetic, developmental or acquired. Ex: aids, cancers, chemo, stress.
cephalization
development of a brain, associated with development of bilateral symmetry. Complex systems are usually split into PNS and CNS
sensory neurons
transmits information from sensory structures that detect external and internal conditions
interneurons
analyze and interpret sensory information to formulate response
motor neuron
transmits information to effector cells
cell body of neuron
contains cytoplasm and organelles, extensions branch off of body
dendrites
highly branched extensions, receive signals from other neurons.
axon
comes off of cell body unbranched until the end. transmits signals to other cells
axon hillock
enlarged region at base of axon where axon signals are generated
myelin sheath
insulating sheath around axon; speeds up signal transmission
synaptic terminal
end of axon branches, each branch ends in a synaptic terminal
synapse
site of signal transmission between cells
glia cells
maintain structural integrity and function of neurons. major categories include astrocytes, radial glia, oligodendrocytes, and schwann cells
astrocytes
structural support for neurons. regulates extracellular ion and neurotransmitter concentrations. facilitates synaptic transfer, induce formation of blood-brain barrier
how do astrocytes help create the blood-brain barrier
tight junction allow more control over extracellular environment in brain and spinal cord
radial glia
function during embryonic development to form tracks to guide new neurons out from the neural tube. can also function as stem cells to replace glia and neurons
oligodendrocytes (CNS) and Schwann cells (PNS)
form myelin sheath around axons. They are rectangular and flat, wrapped around axons. High lipid content insulates axon
nodes of ranvier
spaces between myelin sheaths to speed up signal transmission
resting potential
-70mV. unequal distribution of anions and cations on opposite sides of the membrane. maintained largely because cell membranes are more permeable to K than Na, so more K leaves than Na enters. K/Na pumps also help maintain gradient
at resting potential is there more K inside or outside of the membrane? Na?
more K inside of the cell and more Na outside of the cell. They will both diffuse across gradients. equilibrium is prevented by K/Na pumps
K/Na pump
transfers 3 Na out of membrane for every 2 K ions it moves back in. This means there is a net positive transfer out of the cell.
gated ion channels
neurons can change membrane potential in response to stimulus. include stretch, ligand, and voltage gates.
stretch gates
respond when membrane is stretched
ligand gates
respond when a molecule binds (ex: neurotransmitter)
voltage gates
respond when membrane potential changes
hyperpolarization
inside of neuron becomes more negative
depolarization
inside of neuron becomes more positive
action potential
triggered by depolarization, not graded, it either happens or does not. controlled by voltage gated ion channels
voltage gate activity steps
resting: Na and K activation gates closed; Na inactivation gate open.
depolarization: Na activation gates open and Na enters cell
rising phase: threshold is crossed, Na floods into cell raising membrane potential to +35mV
falling: Na inactivation gates close, K open. Na influx stops, K efflux is rapid
undershoot: K activation gates close after membrane potential is under resting
refractory: Return to resting. Na inactivation remain closed during undershoot and falling, limiting # of action potentials.
is depolarization directional like electrical signals
no, but it only travels in one direction due to refractory period (Na gates locked)
what increase speed in neurons?
nodes of ranvier, larger diameter= less resistance
electrical synapses
occur at gap junctions. Action potential is transmitted directly from cell to cell; important in rapid responses and controlling heart beat
chemical synapses
most synapses are chemical. signal is converted from electrical to chemical to electrical via neurotransmitters.
how chemical synapses work
depolarization triggers opening of Ca channels and influx of Ca stimulates synaptic vesicles to fuse with neuron cell membrane and release of neurotransmitters via exocytosis, it diffuses across synapse, and binds to a receptor stimulating a response on the next neuron.
direct synaptic transmission
neurotransmitters bind directly to ligand-gated channels which opens Na, K or both channels
indirect synaptic transmission
neurotransmitter binds to receptor on membrane (not a channel protein) and a signal transduction pathway is initiated. second messengers eventually open channels causing a slower but amplified response.
modification of signals with chemicals synapses
as it travels, type, amount of neurotransmitter varies and some receptors promote depolarization while others promote repolarization.
what is the brain and spinal cord derived from
hollow, dorsal embryonic nerve cord. Hollow remnants remain in ventricles that fill with cerebrospinal fluid to circulate nutrients, hormones, and wastes.
white matter
aggregation of axons
PNS major role
transmitting info from sensory structures to the CNS and from CNS to effector structures. Therefore nerves are always in left/right pairs to serve both sides of body
cranial nerves
originate in brain and connect to the head and upper body (some only have sensory neurons like eyes and nose)
spinal nerves
originate in spinal cord and connect to rest of body. contain both sensory and motor neurons.
somatic PNS
nerves that transmit signals to and from skeletal muscles. respond to external stimuli and largely under voluntary control
autonomic PNS
nerves that control internal environment; respond to both internal and external signals. involuntary. Three sub divisions: sympathetic, parasympathetic, enteric
Sympathetic nervous system
activates fight or flight. Increases sensory perception and ATP levels and inhibit non-essential functions such as digestion and urination
Autonomic nervous system
returns body systems to base-line function. promotes digestion and other normal functions. antagonistic to sympathetic division
Enteric nervous system
controls digestive system. regulated by both parasympathetic and sympathetic NS.
