Animal Form & Function Flashcards
Cleavage
zygote begins rapid mitosis without cell growth to create a blastula (hollow ball of cells)
Gastrulation
the blastula folds in on itself to create a gastrula, which contains three distinct germ layers of cells
- ectoderm (out)
- mesoderm (middle)
- endoderm (in)
Gastrulation: Ectoderm
creates nervous system, skin, & eyes
Gastrulation: Mesoderm
creates muscular, excretory, reproductive, circulatory, skeletal, & systems
Gastrulation: Endoderm
creates epithelial linings of digestive, respiratory, & excretory systems (organs with openings)
Organogenesis
“creation of organs”
germ layers develop into rudimentary organs (lungs are last)
Morphogenesis
The process that controls the spatial distribution of cells during embryonic development as fetus takes on human shape
• Causes cells to change shape, location, or adhesion
• Some cells are programmed for apoptosis (ex: webbing between human fingers)
• Induced by hormones but can be affected by environmental chemicals
Hierarchical Classification: Cells
form a working body due to emergent properties (these arise from successive levels of structural & functional organization)
• organized into TISSUES
Hierarchical Classification: Tissues
Groups of cells with similar appearance & a common function • organized into ORGANS
Hierarchical Classification: Organs
Tissues that create functional units
• organized into ORGAN SYSTEMS
Hierarchical Classification: Organ Systems
Groups of organs that work together & coordinate to
complete a task
circulatory system
heart, blood vessels, blood
• internal distribution of materials
digestive system
mouth, pharynx, esophagus, stomach, intestines, liver, pancreas, anus
• food processing (ingestion, digestion, absorption, elimination)
excretory system
kidneys, ureters, urinary bladder, urethra
• disposal of metabolic wastes; regulation of osmotic balance of blood
respiratory system
lungs, trachea, other breathing tubes
• gas exchange (uptake of oxygen, disposal of carbon dioxide)
Regulators
Use internal mechanisms to control internal change in response to external fluctuation
• internal conditions remain constant, energy-expensive, can survive in a greater variety of environments
Conformers
Allows for internal conditions to change with external changes
• requires less energy, more susceptible to environmental change
Homeostasis
maintaining of internal balance
• negative feedback loops
negative feedback loops
- A variable is maintained at a particular value (set point)
- Fluctuations above or below are detected by a sensor (receptor), which act as a stimulus to elicit a response
- Once the variable returns to the set point the response is turned off
Homeostasis: Thermoregulation
The process by which animals maintain an internal temperature within a normal range
• Endothermic animals are warmed by the heat created from metabolism
• Ex: mammals & birds
• Ectothermic animals gain their heat from external sources and internal temp. fluctuates with environment
• Ex: amphibians, fishes, reptiles, & invertebrates
Mammal Thermoregulation
negative feedback
mechanism
• hypothalamus (brain) contains sensors for body
temperature
• If body temperature decreases, the hypothalamus detects the change & elicits a response until the body temperature increases to the appropriate range
• shivering (simultaneous muscle contraction), vasoconstriction (blood vessels in skin constrict)
• Vice versa for when body temperature increases
• sweating (evaporative cooling), vasodilation (blood carried to surface of the skin so heat is lost through convection)
Homeostasis: Childbirth
positive feedback mechanism
• A change in the variable results in amplification rather than reverse of the stimulus
• In childbirth the pressure of the baby’s head on receptors in the uterus release oxytocin to stimulate contraction, which cause more pressure, causing more contractions until childbirth is complete
Endocrine System:
To maintain homeostasis, cells of organ systems must communicate & coordinate
response
• nervous & endocrine systems
Endocrine System: hormones
• Hormones are released by endocrine cells
into the bloodstream and carried to target
locations throughout the body
• Only target cells with specific receptor will
respond
• Long lasting effects
• Best for gradual, long lasting changes in the
body (growth, development, reproduction, puberty, digestion & metabolic processes)
Endocrine Pathway
Internal/environmental stimulus → hormone release → hormone travels in bloodstream → interaction with target cell → signal transduction → response
control of pH in the
duodenum
Partially digested food with a low pH is passed from the acidic stomach to the duodenum & it must be neutralized
• S cells of duodenum respond to low pH by secreting the hormone secretin into the bloodstream, which causes the pancreas to release bicarbonate into the duodenum, neutralizing the pH
Neuroendocrine Pathway
Many endocrine pathways depend on a sensor in the nervous system
• Therefore, the hypothalamus plays a central role in both systems (monitors internal temp., hormone release, etc.)
• Signals travel from the hypothalamus to the pituitary gland
• Anterior (front) pituitary releases hormones to regulate other endocrine glands in the body
• Posterior pituitary releases two hormones, oxytocin &
antidiuretic hormone
Antidiuretic Hormone (ADH)
“anti-pee”
negative feedback loop
• Hormone responsible for regulating water balance in blood through the kidneys
• Osmoreceptors in brain detect water levels as too low in blood → release of ADH → ADH increase water reabsorption in kidneys
(reducing urine output by decreasing amount of water in urine) → osmolarity return to acceptable range and makes person thirsty
-high concentration of water; low osmolarity (dilution)
-low concentration of water; high osmolarity (highly concentrated)
Oxytocin
Hormone responsible for uterine contractions in childbirth & release of breast milk during lactation
• Example of positive feedback
• Lactation: baby suckling → receptors in skin send impulse to hypothalamus → oxytocin release → milk is released → baby continues to suckle (& the cycle continues)
Multiple Effects of Hormones
• Hormones may result in more than one type of response
• epinephrine
• Fight or flight response that raises blood glucose, increases blood
flow to muscles, decreases blood flow to digestive tract
• Different receptors and transduction pathways on the target cells will determine the response
Immune System
Enable an animal to avoid or limit infections from pathogens that find our internal environment an ideal habitat
Innate Immunity
Active immediately upon exposure to pathogens & is the same response regardless of previous exposure • Consists of: • Barrier defenses • Phagocytosis • The inflammatory response
Barrier Defenses
Block entry of pathogens
• Skin
• Mucous membranes
• Secretions create a hostile environment
• Lysozyme in tears, saliva, & mucus will destroy cell walls of certain bacteria
• Swallowed bacteria cannot withstand the acidic stomach
• Sebaceous & sweat glands create skin that is acidic enough to prevent bacteria growth
Phagocytosis
Pathogens that enter the body are engulfed by phagocytic cells and destroyed by enzymes
• Non-specific; consume non-self cells
• Two most common in mammals
• Neutrophils: circulate in blood & are attracted by signals from infected tissue
• Macrophages: larger phagocytic cells that travel throughout the body & reside in organs/tissues likely to have pathogens
Inflammatory Response
Injury or infection of tissue cause swelling to increase the presence of white blood cells, aid in repair, & destruction of pathogens
• Mast cells (in connective tissue) release histamine that trigger blood vessels to dilate & become more permeable
• Activated macrophages & neutrophils at the site of injury will release cytokines to promote blood flow to the area bringing more macrophages
• Macrophages consume pathogens & cell debris (creating pus) while the wound heals
Adaptive Immunity
acquired immunity
• Unique to vertebrates
• Allows for specificity, memory, & self-nonself recognition
Lymphocytes
white blood cells that originate from stem cells in the bone marrow. Classified into two categories:
• T cells: lymphocytes that move to & mature in the thymus
• B cells: lymphocytes that remain & mature in the bone marrow
Antigen
a substance that elicits a response from a B or T cell (typically a bacterial or viral protein)
Epitope
the portion of the antigen that binds to an antigen receptor on a T or B cell
• One antigen has several epitopes
• B cells & T cells bind only to one epitope (specificity) & can to respond to any pathogen with the same epitope
Four major characteristics of adaptive immunity:
- There is diversity in lymphocytes & receptors allowing for detection of never before encountered pathogens
• 1 million B cell antigen receptors
• 10 million different T cell antigen receptors
*each cell has random selection of epitope knowledge - There is self-tolerance, meaning there is no reactivity against your own molecules & cells (unless infected, cancerous, or mutated)
- Cell proliferation triggered by activation greatly increases the number of B & T cells for a specific antigen
- There is stronger & more rapid response to an antigen encountered previously due to immunological memory
Proliferation of B & T Cells
Typically, there is only a few B & T cells for any epitope
• Once a B or T cell become activated it will then go through multiple cell divisions creating clones for different roles
• effector & memory cells
Effector cells
short-lived cells that take effect immediately against the antigen (majority)
• B cells form into plasma cells that create antibodies
• T cells create helper T cells & cytotoxic T cells
Memory cells
long lived cells that can give rise to effector cells if you are exposed to the same antigen again
Antigen Recognition by B Cell
B cell receptor binds to an antigen (epitope specificity)
• More (effector) B cells will be formed that secrete antibodies (free-floating antigen receptors)
• B cell antibodies bind to the antigens in the blood & lymph
• This neutralizes pathogens or makes them easier targets for phagocytosis- prevents pathogens from infecting other cells and causes agglutination (clumping)
Antigen Recognition by
Helper T Cells
- Helper T cells bind with fragments of antigen that are displayed on the surface of infected host cells
- A pathogen infects or is taken up by host cells
- Enzymes within the host cell break the antigen into smaller fragments that are moved to the cell’s surface for antigen presentation
- Helper T cell releases cytokines to activate humoral immunity (in blood and lymph) & cell-mediated immunity
- These will divide to create more helper T effector cells & helper T memory cells
Humoral Immune Response
• B cells are used to create antibodies help to eliminate
pathogens in the blood & lymph
• B cells create clones that become B memory cells & antibody secreting plasma cells
• Each plasma cell can give rise to thousands of identical copies, each of which can produce 2,000 antibodies every second
Cell-Mediated Immune
Response
- Cytotoxic T cells use toxic proteins to kill cells infected by pathogens
- These are activated by helper T cells & interaction with antigen-presenting cells which results in production of effector & memory cytotoxic T cells
- The cytotoxic T cell binds to the antigen-presenting cell & secretes proteins that disrupt the membrane & trigger cell death
- The freed pathogen will come in contact with an antibody
Immunological Memory
- Prior exposure to an antigen alters the speed, strength, & duration of an immunological response
- Primary immune response: production of effector cells from the first exposure to an antigen
- This will peak 10-17 days after the initial exposure
- Secondary immune response: a response that is faster (peaks between 2-7 days), has greater magnitude, & more prolonged
- B & T memory cells are long-lived & can quickly create clones
Active & Passive Immunity
- Passive immunity: antibodies are passed between individuals providing short-term protection
- Ex: mother providing antibodies to developing fetus & then to a newborn infant through breast milk
Artificial Active & Passive Immunity
• Active immunity: Immunizations created a primary immune response & immunological memory
• Passive immunity: antibodies can be taken from immune animals
& injected into an infected animal (ex: snake bite victims receive antivenom from sheep/horses that are immunized against snake
bites which allows for the marking & destruction of the toxins before massive damage is done)
