Homeostasis Flashcards
what is homeostasis
the ability of living organisms to regulate it’s internal conditions, despite the changing environment
stimulus response model
Homeostasis involves a stimulus-response model in which the change in the condition of the external or internal environment is detected and appropriate responses occur via negative feedback
what are sensory receptors
sensory receptors (chemoreceptors, thermoreceptors, mechanoreceptors, photoreceptor, nociceptor) detect stimuli and can be classified by the type of stimulus
types of effectors
effectors are either muscles (which contract in response to neural stimuli) or glands ( which produce secretions)
what are hormones
hormones are chemical messengers ( produced mostly in endocrine glands) that relay messages to cells displaying specific receptors for reach hormone via the circulatory or lymphatic system
cells sensitivity to hormones
a cells sensitivity to a specific hormone is directly related to the number of receptors it displays for that hormone (an increase in receptors = upregulation, a decrease = downregulation)
innate immune responses in plants and animals
all plants and animals have innate immune responses ( general/non-specific)
examples of physical defence strategies of plants in response to pathogens
barriers and leaf structures
examples of chemical defence strategies of plants in response to pathogens
plant defensins and production of toxins
what is transmission of disease facilitated by
the transmission of disease is facilitated by regional and global movement of organisms
innate immune response in vertebrates
the innate immune response in vertebrates compromises surface barriers (skin, mucus, and cilia), inflammation and the complement system
Types of cellular (living) pathogens
o Bacteria; Leprosy
o Fungi; Athlete’s
foot (tinea)
o Protozoa;
Malaria ( genus
plasmodium)
o Parasites;
Tapeworm
(Platyhelminthes)
Types of acellular (non-living)
o Prions; CJD
o Virus; Covid-19
what are the Virulence factors
*Adherence factors: Factors that makes a pathogen stick to host cell
*Invasion factors: Components that allow bacterium to invade host cells
*Capsules: Large structure of cells that causes a polysaccharide layer that lies outside the cell envelope
Block and switch off hosts immune system
*Toxins: Poisonous substance produced within living cells or organisms
*Lifecycle change: Development changes through which an organism passes from its inception through the stage at which it reproduces
what is an infectious disease
invasion by a pathogen and can be transmitted from one host to another e.g. malaria or polio
what is a non-infectious disease
genetic and lifestyle diseases e.g. diabetes and asthma
what are the modes of transportation
- direct contact
-contact with bodily fluids
-contaminated food/water
-disease specific vectors
what is direct contact
when an infected person or organism comes in contact/touches another person therefore spreading the disease e.g kissing, shaking hands, contact with vegetation
what is contact with bodily fluids
when a pathogen spreads from blood or other bodily fluids e.g. saliva and can be transferred through the mouth, broken skin, ect
what is disease specific vectors
is when a disease is contracted through any agent who carries and transmits an infectious pathogen to another living organism e.g. Lyme disease through ticks Anthropoids are the major group of pathogen vectors ( ticks, flies ect) - many feed on blood (how pathogen enters host)
what is contaminated food/water
is when a disdeas is contracted through ingesting water/food that has been contaminated with disease causing pathgens ans is often spread through faecal route e.g. cholera, diarrhoea
what kind of immune system dies vertebrates have
vertebrates have booth innate and adaptive (specific) immune response
types of physical defence mechanisms (passive)
Thick barriers (e.g., bark); resistant to pathogens
Leaf hairs (often containing chemicals), spines or prickles; defence against herbivores
Waxy cuticles; prevents formation of moisture to inhibit bacterial infection
Stoma size; small = less pathogens can enter
types of chemical defence mechanisms (active)
Plants produce toxic chemicals in response to pathogens (caffeine, morphine, etc.,)
Some produce defensins – proteins that inhibit development of pathogens
what is 1st line of defence
they are physical barriers to reduce pathogen invasion
types of 2nd line of defence
-phagocytosis
-inflammatory response
-fever
what is phagocytosis
Phagocytosis is when Phagocytic leukocytes migrate to infection sites and engulf foreign bodies to kill it
“ eats cells that shouldn’t be there”
what does the inflammatory response do
the inflammatory response Increases capillary permeability at infected sites, recruiting leukocytes (leads to localised swelling) to kill the pathogen/bacteria
what happens during a fever
Increase body temp to activate heat-shock proteins and support microbial growth
where are leukocytes (white blood cells) found
in the blood, tissue and lymphatic system
types of leukocytes
- Neutrophils
- Basophils
- Eosinophils
- Monocytes
- Lymphocytes (3rd line of defence)
describe neutrophils leukocytes
-most abundant type
-first responder to infection
-Die after phagocytosing a few pathogens
describe Basophils leukocytes
o Circulate in bloodstream
o Responsible for initiating inflammatory responses by releasing chemicals (histamine)
describe Eosinophils leukocytes
o Prominent at sites of allergic reaction and parasite infections
o Rare in blood, common at mucous membranes
describe monocytes leukocytes
o Share phagocytosis with neutrophils
o Longer lasting
o Differentiate into two types of cells
Macrophages (phagocytose)
Dendrite cells
describe Lymphocytes leukocytes
o Responsible for production of antibodies
Antibodies; target specific antigens on pathogens
o Include B and T cells
o Involved in destruction of virus-infected body-cells
o Slowest to respond (require antigen presentation)
what is the inflammatory response
- The way the body reacts when pathogens damage cells
- Damaged cells release prostaglandins (chemical that directs blood flow to an injured area) which work like histamine (causes vasodilation to recruit leukocytes to area)
- Damaged cells also release chemokines that recruit phagocytes to site of damage to fight infection
what is the complement system
- Works in conjunction with innate immune system
- Where your body produces proteins that can trigger phagocytosis (usually from liver)
what is Acquired (adaptive immunity)
*Responds to specific antigens by creating antibodies and memory cells
*Relies on the clonal expansion of plasma cells to produce large numbers of antibodies thus there is a delay between initial exposure to pathogen and production of large quantities of antibodies
*Distinguishes self-cells from antigens via lymphocytes that enter the blood from the bone marrow or thymus and become either T lymphocytes (thymus) or B lymphocytes (bone marrow)
what is the Humoral Immune Response
*From serum antibodies (produced by plasma cells)
*Refers to bodily fluids where free-floating serum antibodies bind to antigens and assist in elimination
*When they encounter pathogen, produce antibodies that complimentarily fit antigen
*B-cells divide rapidly to produce cells with replicates of the antibodies or cells that remain long after in case of reinfection (memory cells)
what is the Cell-mediated immune response
*Response carried out by T-cells
*Helper T-cells activate other immune cells
*Cytotoxic T-cells assist with elimination of pathogens and infected host cells
what are T-cells
- Attract and activate phagocytes
- Localise pathogen to prevent locomotion
- Rupture pathogen membrane and destroy it
- Can also become memory cells
Passive Vs active immunity
Active:
- The production of antibodies by the body itself
- Longer-lasting
*Creates memory cells
Types of active
- NATURAL; infection
-ARTIFICIAL; vaccination
Passive:
-The acquisition of antibodies from another source
-short-lived
*No memory cells developed
Types of passive
NATURAL; maternal antibodies
ARTIFICIAL; monoclonal antibodies
what are FACTORS THAT AFFECT IMMUNITY
*Persistence of pathogens within host
*Transmission mechanism
*Proportion of the population that is immune/has be immunised
*Mobility of
individuals in the affected population
what is metabolism
*chemical reactions occurring in the cells = metabolism
o these metabolic processes process in small steps, the sum of which is called a metabolic pathway
o all the anabolic and catabolic reactions happening in an organisms metabolism as a whole
CATABOLIC REACTIONS BREAK DOWN (e.g., C6H12O6(glucose) to CO2 and H2O)
ANABOLIC REACTIONS BUILD COMPLEX MOLECULES (E.G., from H2O and CO2 to C6H12O6(glucose) in photosynthesis)
- Require energy
what are optimal conditions
-Each step of metabolic pathways requires a specific enzyme (THE 5 FACTORS THAT AFFECT ENZYME ACTIVITY)
what is Tolerance limit
-The range of particular environment (eg. light, temperature, availability of water) or physiological (particular chemical concentrations) factor within which an organism can survive.
what is the negative feedback loop
o Causes a response that brings the body back to normal
E.g., FEVER:
High temp detected by sensors
Relayed to temp-regulatory control centre in brain
Control centre processes info and activates effectors (e.g., sweat glands)
what is postive feedback loop
o Involves an increase in function away from normal
E.g., CHILDBIRTH:
Head presses on cervix
Pressure activates a signal
Oxytocin gets released from pituitary gland
Oxytocin increases contractions
what are sensory receptors
Structures that detect changes in the external of internal environment
steps of Stimulus model
Input -> receptor
->regulator -> effector ->output
types of sensory receptors
*NOCICEPTOR
o Responds to damaging or potentially damaging stimuli by sending signals to spinal cord and brain
*THERMORECEPTOR
o Detects differences in temp
*CHEMORECEPTOR
o Detects chemical composition of blood levels (CO2, O2, ion conc.)
*MECHANOCEPTOR
o Detect touch, pressure, vibration and sound from ex. And int. environments
*PHOTORECEPTOR
o Detects changes in light (RETINA)
what is a stimulus
: a detectable change in internal or external environment (INPUT). Can be physical or chemical
process of stimulus model
*sensory RECEPTORs detect the stimuli
*A chemical message is then transmitted to the coordinating centre (REGULATOR) that determines if a change is required
*Another chemical messenger brings about a response (OUTPUT) within a cell or EFFECTOR organ
types of neurons
*Sensory neurons:
o Convert external stimuli from organism’s environment into internal electrical impulses
*Motor neurons:
o Form the pathway which impulses pass from brain/spinal cord to effectors
how nerve implus occur in ACTIVE TRANSPORT/DIFFUSION/SELECTIVE PERMEABILITY OF CELL MEMBRANE
- ACTION POTENTIAL (when nerve impulse passes through)
o Occurs when resting potential across membrane has high stimulis (ex. Mechanical)
o AXON becomes depolarised (inside becomes less negative)
o 35mV
o Then returns to resting potential (REPOLARISATION)
what are nerve impulses
- Neurons convey info via nerve impulses (electrical signal)
- RESTING POTENTIAL
o When a nerve is not sending a nerve impulse it has a resting potential of -70mV
Inside of neuron is negative relative to outside
INSIDE; lots of large negative ions
OUTSIDE; lots of Na, Cl and Ca ions
how does action potential occur
- VOLTAGE-gated ion channels (closed during resting potential) open allowing sodium ions to move in (makes inside more positive)
AT PEAK OF ACTION POTENTIAL; Na channels close K channels open K leaves inside becomes negative again
transmission of nerve impulse
- Impulse forms because action potential causes a small current to flow in cytoplasm and in extracellular fluid which stimulates depolarisation of the next part of the nerve membrane
what are synapses
- The junction between a neuron and another neuron or effector by passage of a nerve impulse or of a chemical called a neurotransmitter
what is signal transduction
- the conversion of chemical signals that are transmitted from outside the cell to a functional change or response within the cell
hydrophilic signals
Received by receptors on cell membrane
1. signal molecules binds to specific receptors outside of cell membrane. When combined the receptor changes shape or activates an internal response
2. activation inside the cell causes a signal transduction cascade creating effector protein
3. the resulting effector protein results in
* changes to cellular metabolism/function/movement
* gene expression change
4. sometimes there is no transduction cascade and the effector protein is produced from the change in receptor shape
5. receptor can be ‘reset’ and release the signal molecule
thermoregulation
ENDOTHERM
animal that produces it’s own heat
STRUCTURAL FEATURES
- Brown Adipose Tissue
o Specialised for rapid heat production
o Stores lipids (lots of energy)
o Contains more mitochondria than white fat
o Provides insulation
o Skin, feathers, fur and blubber provide insulation
Reduce heat flow between animals and environment
BEHAVIOURAL RESPONSES
- Kleptothermy
o The sharing of heat amongst animals - Hibernation
o Prolonged, usually seasonal state (colder months) of reduced activity and metabolic depression
o Body temp drops
o Reduced energy expenditure
o Can also delay reproduction - Torpor
o Reduction of metabolic activity daily (or usually nightly)
o Period of torpor depends on air temp (colder means greater days in torpor) - Aestivation
o Form of hibernation/torpor that occurs during warmer months
o Usually in response to a lack of food in arid environments
PHYSIOLOGICAL MECHANISMS
- Construction of the capillaries restricts blood flow in the skin, lowering heat loss
- Vasodilation allows blood to flow through the skin capillaries and transport heat from the body to the skin facilitating heat loss
EVAPORATIVE HEAT LOSS
- Panting increases the cooling effects in birds and many mammals
- Sweating moistens the skin, helping to cool an animal down
what is COUNTERCURRENT HEAT EXCHANGE
- The arrangement of blood vessels in many marine animals and birds allows for counter current heat exchange
- Transfer of heat between fluids flowing in opposite direction and reduce heat loss
HOMEOSTATIC MECHANISMS rolw
The hypothalamus has a central role in thermoregulation – it registers core body temp and coordinates nervous and hormonal responses to restore normal body temps
insulin role
- Insulin signals cells to take up glucose from the blood -> increasing metabolic activity
what is osmoregulation
Osmoregulation is the process of maintaining salt and water balance (osmotic balance) across membranes within the body.
nephron role
- Filters blood
- Reabsorbs nutrients
- Secretes excess waste molecules
- Water is absorbed from
o Collecting duct
o Distal convoluted tubule
WHAT CONTROLS THE BODY’S REABSORPTION OF WATER?
- Anti-diuretic hormone (ADH)
o Produced in hypothalamus
o Increases permeability of the distal convoluted tubules and collecting ducts to water
o This results in more water being reabsorbed from the glomerular filtrate back into the blood
o Thus less concentrated urine is excreted
o Restores normal water balance (negative feedback loop)
what happens in opposite of ADH
if osmoreceptors detect higher water content -> less ADH released -> decreases permeability and so forth
what triggers anti-diuretic hormones
- High blood concentration
- Low blood volume
- Low blood pressure
what are Osmoconformers
o Cannot regulate
o Match their body’s salt levels/osmolarity of body fluids to their environment
o Make substances to keep external and internal molarity equal
o No energy used
e.g. some marine animals
what are osmoregulators
2) OSMOREGULATORS
o Actively control internal salt and water balance/keeps osmolarity of body fluids constant
o Need to be able to get rid of excess salts or actively promote uptake of salts from environment
o Use energy to maintain the osmatic gradients via active transport
(e.g., most land animals & fish)
Hydrophyte
- Any plant adapted to grow wholly or partly submerged in water or wet habitats
Mesophyte
o A plant adapted to growing in well-watered soil.
- XEROPHYTE
o A plant that has adaptations to survive in an environment with little liquid water.
- HALOPHYTE
o A plant that grown in waters of high salinity.
stomata
o Openings on the underside of leaves
o When the plant has enough water, stomata open. Oxygen and water vapor can exit.
o When plant is low on water stomata to close. This reduces water loss through transpiration, helping the plant conserve water and maintain its internal balance.
- VACUOLES
o Vacuoles regulate the turgidity by regulating the amount of water present inside the cell.
o cell has excessive water: vacuole usually absorbs the water and then diffuses it out of the cell
o cell lacks water: water from the vacuole tends to revert into the cell thereby maintaining turgidity
- CUTICLE
o prevents evaporation of water from the epidermal surface (DRY/HOT ENVIRONMENT)
o can also prevents external water and solutes from entering the tissues (WET/HUMID ENVIRONMENT)
