Physiology 3051 unit 1

physiology

the study of normal functioning of humans throughout the whole body

function vs mechanism

why vs how

epithelial cells

separate internal and external environment

Extra cellular fluid in the body

14 liters

intracellular fluid in the body

28 liters

regulation of homeostasis

nervous system and endocrine system

endocrine system timing

slow response

endocrine system function

diffuse targets, entire tissues and organ systems impacted

nervous system timing

very fast response

nervous system function

negative feedback

positive feedback loop

cause a rapid change in variable, reinforces stimulus rather than decreasing

breaking a positive feedback loop

requires a terminating event (childbirth)

anticipatory response

allows body to start response in anticipation of the change (Pavlov's dogs drooling)

Plasma membrane

selectively permeable phospholipid bilayer

hydrophilic

molecules CANT cross (water loving) fast

hydrophobic

molecules CAN cross (water fearing) slow

facilitated diffusion

no energy needed, needs transmembrane protein, moves down the concentration gradient, ion channels allow charged ions to cross membrane

simple diffusion

substance can freely enter the cell

primary active transport

directly uses ATP, needs transmembrane proteins, pumps AGAINST concentration gradient

secondary active transport

pumps AGAINST concentration gradient, uses energy indirectly

endocytosis

molecules enter through vesicles formed from the plasma membrane

exocytosis

intracellular vesicle attaches to the plasma membrane and releases contents into the ECF

Hydrophilic signaling molecule

bind to the extracellular receptors on the surface of the plasma membrane, initiate 2nd message or cascade, alter ion channel conformations

hydrophobic signaling molecule

bind to intracellular receptors and alter transcription an protein synthesis

hydrophobic signaling molecule speed

slow effect, metabolized slowly

hydrophilic signaling molecule speed

fast effect, metabolized quickly

Autocrine signaling

the target cell is also the secreting cell

paracrine signaling

signal released from cell A binds to neighboring cell B

Neurotransmitter signaling

signal released from axon terminal into synapse, signals bind to nearby cell receptor

Endocrine signaling

Signals enter bloodstream and bind to a receptor that is far away (travels long distances)

neuro hormone signaling

Signal exits axon terminal, goes through he bloodstream and binds to cell receptor

how does water cross cell membranes

aquaporin channels

what mode of transportation does water use

passive transport, always down its concentration gradient

osmolarity

total solute concentration of a solution per unit volume

if water concentration goes down, the solute concentration...

goes up

2 multiple choice options

Tonicity

describes behavior, no units, determined by osmolarity and penetrating vs non penetrating solutes

hyperosmotic

greater than 300 mosm

2 multiple choice options

hypoosmotic

less than 300 mosm

2 multiple choice options

isosmotic

equal to 300 mosm

2 multiple choice options

penetrative solution

urea and ethanol

non penetrative solution

Glucose, Na+, Cl-, K+, and other ions

central nervous system

brain and spinal cord

pheral nervous system

afferent and efferent divisions

astrocytes

monitor and regulate ECF of the CNS, supply metabolic fuel to neurons, important for blood-brain barrier

Oligodendrocytes

synthesize myelin in the CNS

Schwann cells

synthesize myelin in the PNS

microglia

proliferate following neuronal injury, remove cell debris, have immune function

synapse

Gap between neurons

convergence

multiple presynaptic neurons communicate with ONE postsynaptic neuron

Divergence

one presynaptic neuron communicates with MULTIPLE postsynaptic neurons

at rest, membrane potential is...

negative (-70mV)

chemical driving force

concentration gradients

electrical driving force

opposites attract, like charges repel

volume in a cell only changes when...

water enters the cell

resting membrane potential is generated by...

the Na+/K+ATP-ase pump

Na+ leak channels

always leaking IN but a SMALL amount

K+ leak channels

always leaving the cell

Equilibrium potential equation

neurons communicate by...

changes in membrane potential

ligand gated channels

chemicals

leak channels

always open

voltage-gated channels

open and close in response to changes in membrane potential

mechanically-gated channels

open in response to physical deformation of the receptor

graded potentials

summation, initiated by depolarizing and hyperpolarizing, mediated by ligand-gated channels, amplitude varies with stimulus intensity

action potentials

amplitude is all or nothing, initiated by depolarization only, no summation, mediated by voltage-gated channels

action potentials phase 1

threshold reached, Na+ channels open and membrane rapidly depolarizes as the Na+ enters the cell, K+ channels DONT open

action potentials phase 2

sudden decrease in Na+ permeability, sudden increase in K+ permeability

action potentials phase 3

Na+ channels close, K+ channels close slowly so the cell hyper polarizes so it becomes more negative than its RMP, then everything closes and Leak channels bring cell back to RMP

refractory periods

an action potential, the membrane is less excitable than at rest

absolute refractory

not possible for a cell to generate a 2nd action potential voltage-gated Na+ channels CANT open

relative refractory

possible to generate a 2nd action potential, bit needs a larger stimulus than normal, SOME Na+ channels have entered the close state

Unmyelinated neurons

action potential begins at trigger zone and propagates to the axon terminal, propagation is slow (cheaper)

myelinated neurons

myelin creates membrane resistance so ions flow towards the middle of the axon, faster (expensive)

Node of ranvier

brief breaks in the myelin segments

electrical synapse

multiple cells "behave as one"

chemical synapse

slow, allow for more complexity and modifications

pre-synaptic event 1

Action potential propagates to axon terminal

pre-synaptic event 2

voltage-gated Ca2+ channels open

pre-synaptic event 3

rapid influx of Ca2+ actives vesicle exocytosis, vesicles fuse with the plasma membrane

pre-synaptic event 4

neurotransmitter diffuses across synaptic cleft onto post synaptic cell

Excitatory post-synaptic event 1

neurotransmitter binds to post-synaptic receptor

Excitatory post-synaptic event 2

ligand-gated channels open

Excitatory post-synaptic event 3

cations flow through channel into cell

Excitatory post-synaptic event 4

net effect is depolarization (very small), summation is key!

Inhibitory post-synaptic event 1

Neurotransmitter binds to post-synaptic receptor

inhibitory post-synaptic event 2

ligand-gated channels open

inhibitory post-synaptic event 3

EITHER K+ flows out of the cell OR Cl- flows in

inhibitory post-synaptic event 4

net effect is hyper polarization or inhibits further depolarization