Midterm 1 Flashcards
what is physiology?
- the study of normal mechanisms and their interactions that work within a living system
- focuses on how organisms, organ systems, organs, cells, and biomolecules carry out the chemical or physical functions that exist in a living system
natural selection:
- matting for traits that are best suited to the environment
what is the scientific approach/ hypothetico-deductive?
- ask a question
- propose various hypotheses to explain it
- design experiments or observations
- conduct experiments
- use outcome of experiments to refine the question
- repeat the process to build reproducible outcomes that falsify all alternative hypotheses
- elevate hypothesis to a theory
what is the vertical approach to studying physiology?
hierarchical nature of physiology= atoms, molecules, cells, tissues, organs, organ systems, organisms
what is the horizontal approach to studying physiology?
studying the interactions of all systems together, functional organism
what is the comparative approach of studying physiology?
comparing the mechanisms and processes used by major invertebrates and vertebrates
- universal functions and principles
- unique adaptations
how did the physiology of organisms come to be how it is today?
through evolution of other ancestral processes and mechanisms
-complexity increased
what does the proximate/mechanistic approach to physiology ask?
how the process/function works
what does the evolutionary/ultimate approach to physiology ask?
how the organism got to be that way
what does the meteleological approach to physiology ask?
what the function or purpose of something is
-sometimes things evolve in a way that isn’t logical from an ancestor
how does a theory form?
- when a hypothesis is supported over and over
- a theory is a very strong statement
what is the smallest unit capable of carrying out the processes of life independently
a cell
what are the 4 basic functions of a cell?
- self-organization: using resources in the environment to create the cell
- obtain energy
- preform chemical reactions
- eliminate waste products from metabolic processes
- synthesize things that are needed
- metabolism - self-regulation
- sense and response to environment
- control exchange of material between cell and environment
- repair damage
- homeostasis - self-support and movement
- self-replication
what does it mean when a cell has a specialized function?
it has an elaboration or modification to its basic function in order to be better suited for its role in the environment its in
what are the 4 types of tissue?
- epithelial: sheets of cells that cover surfaces (skin, ducts, passageways, glands)
- connective: very diverse tissues, few cells, many fibres (proteins) and ground substance (to hold tissue together)
- collagen, bone, cartilage, blood, lymph, tissue fluid - muscular: muscle fibres for locomotion
- can be striated (skeletal, cardiac) or non-striated (smooth muscle) - nervous: neurons for cell communication
- used to measure or sense internal and external environments
- decide if change must be made
- initiates process to bring change
why does the surface area to volume ratio matter for organisms?
the larger the organism the smaller the SA: volume ratio which matters for diffusion rates
- its a disadvantage when diffusion is the only way of transport, without bulk transport or distribution system
- but an advantage is it involved retention of heat
what is the basis of Ficks law?
-factors affecting rate of diffusion
what does Ficks law state?
- distance: the further a substance has to diffuse, the slower the diffusion
- concentration gradient: increase in conc gradient leads to faster diffusion
- surface area: more SA, more diffusion
- size of molecule: increase in size (molecule weight), decrease in diffusion
- permeability of barrier: increased permeability leads to increased diffusion
- neuron and muscle cells can chance permeability when needed
what ways can larger organisms overcome the limits to diffusion in multicellular organism?
- bulk transport
- increased SA
- final step (diffusion into the cell) will still rely on diffusion though
what are the rates for O2 over different distance that are relevant to diffusion-based processes?
1 micrometer: 240 microseconds
10 micrometers: 24 ms
100 micrometers: 2.4 ms
what is homeostasis?
maintenance of a desired state (in a narrow range) in face of disturbances
-body condition maintained within limits necessary to preserve life (equilibrium)
what is the private environment that body cells are contained in?
the extracellular fluid (cells exchange nutrients and wastes with it)
-in vertebrates its made up of plasma and interstitial fluid
what factors are regulated by homeostasis?
- energy: concentration of energy rich molecules- fuel
- conc of O2 and CO2:important for pH regulation, carbonic acid-bicarbonate buffer system
- pH: affects nerve and enzyme function, important for optimal effieciency
- waste products: toxicity issues
- water and electrolytes: controls volume and osmolarity of intra and extracellular fluid
- blood volume and pressure: maintain plasma volume for effective bulk transport of nutrients and wastes
- temperature: maintain optimal cellular functions
- social parameters: regulating living conditions and populations levels (important for insects like termites)
how is a compensatory response achieved for homeostasis?
-usually through negative feedback (a change in a controlled variable triggers a response that opposes the change which then moves the variable in opposite direction of initial change)
to maintain homeostasis, compensatory responses are required, how are most of these responses achieved?
- negative feedback mechanisms: a change in a controlled variable triggers a response that opposes the change and moves the variable in the opposite direction of the initial change
- can be simple (unreferenced) or complex (references to a specific condition)
what two things could a response effector to homeostasis be?
- antagonistic: works against the variable
- behavioural: getting away from the variable
what are the steps of a negative feedback loop?
- a deviation in a controlled variable occurs
- gets detected by a sensor
- the sensor informs an integrator
- instructions are sent from integrator to an effector
- the effector brings about a compensatory response
- the response results in the controlled variable restoring to normal
- system responsible for response is shut off by negative feedback
what problems can occur from negative feedback and how are the resolved?
- delayed response: anticipation
- overshooting: feed-forward system
what is acclimatization in homeostasis?
- systems alter existing feedback to a new situation over time period
- includes up regulation and down regulation
how does anticipation/feed-forward happen?
- oncoming disturbance
- sensor detects this
- anticipator activates the corrective response before the variable
- integrator response
- effector brings about the response
what is acclimation in regard to homeostasis?
- acclimitization that takes place in a controlled situation
- usually not the external environment
- 1 to 2 controlled or defined variables are usually involved
what is adaptation in regard to homeostasis?
- acclimation or acclimation to new situation on longer term
- apdated to new set of conditions or environment
there are other change processes aside from negative feedback to maintain homeostasis?
- dormancy: maintaining homeostasis in broader sense, slowing down normal function over a period of time
- voluntary or on-demand: locomotion, growth, development, muscle and gland activity
- reset systems: change the set point of negative feedback system (night time body temp, sexual maturity)
- positive feedback: mechanisms to create rapid change when conditions demand it (birth, blood clots, immune system reactions)
what resets the negative feedback set point?
higher regulators, change set point which effectors the integrators timing of response
ex. sexual maturity, hibernation, mating behaviours, fever (temp control)
how does positive feedback work?
- a deviation in the controlled variable occurs
- sensor may be used to signal integrator or regulatory process
- output (effector) released
- change is enhanced by the output
positive feedback (bird of mammal) example:
- signal from mature fetus
- uterus begins contractions
- stretch sensors
- mothers hypothalamus is triggered
- pituitary gland is told to secrete oxytocin
- contractions are enhanced by to oxytocin and the signal repeats
what systems affect the whole body?
- nervous system: fast responses, CNS and PNS, reflexes
- endocrine systems: hormonal, duration over speed
what systems are required for support and movement?
- skeletal
- muscular
what systems are involved in maintenance?
- integumentary (skin)
- respiratory
- circulatory
- digestive
- excretory
- defence/immune
what are the universal components of the cell?
- water: universal solvent
- inorganic chemicals (NA+, K+, Cl-, Ca2+, PO4 3-)
- organic molecules: carbohydrates, amino acids and proteins, nucleotides and nucleic acids, lipids (glycerol and fatty acids)
what does the plasma membrane control movement of molecules between?
-intracellular and extracellular fluid
what is the function of the two endoplasmic reticules?
smooth: synthesis and storage of lipids
rough: protein synthesis
what is the function of the Golgi complex?
-refine, sorting and directing of ER products
what is the functions of lysozyme, proteosomes, and peroxisomes?
-recycle (breakdown) and detoxify using endocytosis
in what forms can energy be stored in the body?
- triglycerides: stored in adipose tissue (fatty acid source)
- glycogen: stored in liver and muscle tissue (source of glucose)
how does the plasma membrane ensure that cells maintain required intracellular conditions?
the membrane is a selectively permeable barrier that only lets in/out what it needs to
what are the functions of the proteins in the cell membrane?
- channels
- carriers
- receptors
- docking marker acceptors
- enzymes
- cell adhesion molecules
- self-identity marker
what are the four ways cell membrane transport can occur?
- passive
- active
- carrier-mediated transport
- vesicular transport
how does passive transport work?
- diffusion, osmosis (water facilitated)
- aquaporins: allow water diffusion so cell can regulate the amount of water in it
how does active transport work?
- using an enzyme that pumps protons or electrons
- can be symporter or antiporter
- coupled with ATP
- secondary active transport can use electrochemical gradient to power it (ex. using Na+ gradient to power entrance of glucose)
how does carrier-mediated transport work?
can be passive or active
how does vesicular transport work?
by end or exocytosis
-phagocytosis, pinocytosis, potocytosis
how is the rate of water diffusion regulated?
-amount of aquaporins is up- or down-regulated depending on what the cell needs
how does the Na+/K+ pump work?
- the pump has 3 high-affinity sites for Na+and 2 low-affinity sites for K+ when its exposed to intracellular fluid
- 3 Na+ from ICF (Low conc.) bind to pump and it splits ATP to ADP and Pi, Pi binds to pump
- phosphorylation causes the pump to change conformation, Na+ binding site is now exposed to opposite side of membrane and 3 Na+ are released to ECF because affinity to Na+ decreases
- pumps binding site for K+ to ECF is exposed and affinity for K+ increases
- 2 K+ from ECF (low concentration) bind to pump, pump releases phosphate group, depos cause pump to revert to original shape
- 2 K+ are released to ICF (high conc) affinity for K+ decreases during change in shape
Na+ affinity increases and step 1 repeats
how does glucose get into the cell by secondary active transport?
- Na+/K+ pump uses energy to drive Na+ uphill out of cell, binding Na+ where conc is higher increases affinity for glucose
- Na+ conc gradient is used to simultaneously move Na+ downhill and glucose uphill from lumen into cell, Na+ and glucose are bound to the protein which causes it to open to cell interior, Na+ is released to inside of cell where conc is lower, because the affinity lowers, glucose is released into cell too (high conc)
- GLUT passively moves glucose downhill out of cell into blood Na+ is released to inside of cell where conc is lower
what is facilitated diffusion?
- required transport proteins, molecules move down conc gradient (high to low)
- limited by the carrier becoming saturated, trans max (Tm)
what are the methods of intercellular communication?
- direct: intercellular connections
- indirect: intercellular messages
what are the types of direct cell communication?
-gap junctions: tunnels (connexions) that allow movement of small molecules and ions between cells
important in smooth muscle contraction
-transient direct link up: signalling molecules on the membrane surface (ex. MHC antigens)
-nanotubes: long tubes of plasma membrane that allow exchange of molecules and organelles
what are the types of indirect cell communication?
chemical messengers:
- paracrine signals: regulate nearby cell activity
- neurotransmitters: from neurons, act on local target cell
- hormone secretion: endocrine cells release, travel in the blood, act on any cell with receptor
- neurochrome secretion: from neurons, product is hormone, act distantly
- autocrine: cell releases messenger that regulates its own cellular activities
pheromones: released into environment to act on another organism
how do receptors respond to signals depending on the type of receptor they are?
- ion channel receptor: ions enter cell to generate cellular response
- enzyme receptor: activates protein kinase to change other proteins and give a cellular response
- secondary messenger system
example of a secondary messenger system (cAMP):
- the messenger binds to the receptor in the cell
- G protein is activated by binding
- G protein activates adenylate cyclase
- adenylate cyclase causes conversion of ATP to cAMP (this is the second messenger)
- cAMP activates protein kinase A
- PKA can phosphorylate (activate) many other enzymes
- active enzymes convert substrate to product and give a cellular response
what is membrane potential?
- critical to cell function
- occurs due to differential Na+ and K+ concentrations
- membrane is polarized
what is resting membrane potential and how is it maintained?
when excitable cells (nerve and muscle) are at rest (-70mV)
-maintained by Na/K-ATPase pump and different solubilities in cell water and affinity for cell proteins
where is Na+ concentration high and where is K+ concentration high?
- Na+ conc is high outside of the cell in the extracellular fluid (will move into the cell)
- ENa+= 60mV
- K+ is high in the cell in the intracellular fluid (will move out of the cell)
- EK+= -90mV (equilibrium potential)
- membrane potential is -70mV because K+ is dominant because its more permeable
how do nerve and muscle cells use the membrane potential?
- initiate rapid and transient change in membrane permeability which causes MP to fluctuate
- this produces a nerve impulse for muscle contraction
the ECF needs to be maintained so exchanges of what can occur with the cell?
- nutrients
- O2 and CO2
- easte
- chemical messengers
- specific messengers
what is an obligate aerobes?
-requires O2 continuously for survival (mammals)
what is a facultative anaerobes?
can adapt to anaerobic conditions for days or months (brine shrimp embryos)
what is an obligate anaerobes?
- thrives in anaerobic environments
- killed/inhibited in presence of O2
- achaea, bacteria
what is a membrane potential?
-charge difference across membrane, caused by movement of ions across membrane due to trigger or stimulation
what is the normal membrane potential at rest?
-70mV
how can you measure the membrane potential?
- voltage clamps: hold V constant with electrical circuit to measure ion movement
- patch clamping: isolate specific portions of membrane
what possible triggering events could cause membrane permeability to change and ion movement to occur?
- stimuli
- change in electrical field near ion channel in excitable cells
- interaction of chemical messenger with receptor on a neurone or muscle cell membrane
- spontaneous change of MP caused by inherent inter-balance in leak-pump cycle
since ions can normally cross membrane, they need channels, what are the two types?
- leaky: always open (K+ channel is example)
- gated: open and close in response to triggering event
- event alters membrane permeability, usually causes conformational change in channel protein
what are the types of gated ion channels?
- voltage gated: response to voltage change in MP
- chemically gated: change conformation in response to binding of specific chemical messenger
- mechanically gated: réponse to stretching or deformation
- thermally gated: respond to local changes in temp
what is a graded potential?
- type of electrical signal
- brain and neurons use these
- spread in all directions from stimuli
- differ in size
- smaller than AP
- short distances
- dissipate (related to Oms law) less current flow as yo get farther away
- the stronger to signal the more depolarizing
- can be depolarization or hyperbole
what is an action potential?
- brief and rapid
- cause large change in MP
- non-decrimental, don’t diminish in strength
- needs to reach threshold for complete depolarization
- all or nothing response
- unidirectional
- resting MP is established very quickly after
- long distances
what is threshold for an action potential to occur?
-55mV
what channels cause action potential to occur in a cell?
-Na+ (has two gates, one to inactivation before protein returns to rest) and K+ voltage gated channels
how can membrane potential be reestablished so quickly?
-only small amounts of ions have left or entered the cell
what are the four parts that make up a neuron?
- cell body: contains nucleus and organelles
- dendrites: project out to increase SA to receive input signals (carry signal toward body, contain proteins and receptors for binding chemical messengers (neurotransmitters) from other neurons)
- axon or nerve fiber: single tubular extension that conducts signal away from cell body to other cells
- axon hillock: where axon meets body (threshold needs to be meet here for AP to be triggered)
where does a signal go after the axon hillock?
-travels along to axon (conducting zone) to axon terminals (output zone)
what is a nerve?
-a bundle of axons outside CNS
what is included in the CNS?
-spinal cord and brain
what is a fiber tract?
-bundle of axons inside the CNS
what are the 2 ways an AP can be conducted along surface of axon?
- contiguous conduction
2. saltatory conduction
hoe does contiguous conduction work?
- a local current flow between active area t peak of AP and adjacent inactive area still and resting reduces the potential in inactive area to threshold, triggering AP in previously inactive site, original active site returns to resting and new active site induces action potential in next adjacent inactive area by local current flow
- done by depolarization of neighbour triggering next site
what is a refractory period for AP?
- reason why Ap only travels in one direction
- portion of membrane has just undergone AP and cannot be rsetimulated, Na+ gates in inactive position (absolute refractory period)
- a relative refractory period can occur if Na+ channels are capable of opening again but K+ channels are open (making cell more negative), only a strong enough stimuli can bring cell membrane to -55mV by countering K+ leaving will cause AP
what is the speed of an action potential determined by?
- myelination
2. diameter of fibre
what is myelin mostly made out of?
-lipids, act as electrical conductor around neuron axon (prevents leakage of ions or electrons
what cells is myelination produced by?
- schwann cells in PNS
- oligodendrocytes in CNS
what is saltatory conduction?
- AP jumps to each node of ranvier
- conserves energy
- used for urgent messages (myelin is costly)
- speeds up AP by 50x (myelination)
What is white matter?
-myelinated axons
