Physiological Systems: signalling mechanisms Flashcards
Homeostasis
stable internal operating environment: keeps internal env. within limits
Physiology
study of function (cells, tissues, etc)
Physiological integration
body systems work together, all body systems under control/regulation of nervous system
Intercellular signaling
between cells
intracellular signaling
within cells
Neurons
communicate via generation of chemical/electrical signals
Chemical signals
communication at synapse; main chem signal: neurotransmitter
Electrical sugnal
along plasma membrane of neuron; moving ions (movement of charge)
Separation of charges
ions on either side of semi-permeable membrane: contributes to formation of membrane voltage (potential)
Resting neuron
asymmetric distribution of ions across membrane (K+ more concentrated inside, others outside) –> resting membrane potential of ~ -70mV
Ion transport
- facilitated diffusion (molecules that cant cross membrane on own) 2. active transport (energy used to transport substances against concentration gradient)
Ion Channels
ion transport path: selective for specific ions, gated
Ligan-gated
chemically gated
Voltage-gated
changes in membrane voltage gated
mechanical-gated
changes in membrane stretch gated
Concentration Gradient
influences direction of ion movement: generated by differences in concentration b/ two regions (high to low)
Electrical gradient
influences direction of ion movement: asymmetric distribution of charge, attraction between opposites: driving force, time/access no electrical gradient
Electrochemical gradients
determines net flux (in or out of cell) for ion : presence/direction/strength of electrical/concentration gradients
Equilibrium potential
Potential across membrane that produces electrical force on ion EXACTLY oppoite to force of concentration gradient: BALANCES ionic concentration gradient
Electrical signals generated in a neuron
neurotransmitters bind to receptors (ion channels to open) –> temp. change in membrane potential bc change in movement of ions across membrane
Neurotransmitter binding to receptor changes
Depoloarization: membrane potential = less negative/less polarized: Excitatory Post-Synaptic Potential (EPSP)
Hyperpolarization: membrane potential gets more negative: Inhibitory “ “ (IPSP)
Action Potential
if graded potentials depolarize membrane –> threshold voltage: neuron fires action potential
Excitatory effect
brings membrane CLOSER to threshold to fire action potential
Inhibitory effect
moves membrane AWAY from threshold
Action Potential Phases
rising phase (upstroke), falling phase (repolarization), undershoot (hyperpolarization)
