BIOL 1108 - Sensory

Sensory systems

the ability to perceive your surroundings — to see, hear, and smell what’s around you — depends on your sensory receptors. If your perceptions indicate danger, food, etc., your ability to act on that information depends on your nervous system

Physical or chemical stimulus

light, sound, pain, temp, or chemical molecules/ions

Transduction

transformation of the physical stimulus to neural signals

Transmission

neurons carry the signal towards the brain/spinal cord using action potentials and interneuron communication

Electrical Impulse

in biology, usually we mean the fluctuation of ion concentrations

Cations

positively charged ions (H+, Na+, Ca²+)

Anions

negatively charged ions (Cl-, OH-, CO3-)

Active transport

requires energy (ATP); low → high

Passive transport

doesn’t require energy (ATP); low → high

Dendrites

receive signals from other cells

Cell body

organizes and keeps the cell function

Axon hillcock

junction between soma and the axon, point where signals are summed/accumulated and the action potential is initiated

Nucleus

controls the entire neuron

Axon

transfers signals to other cells and organs; covered by the myelin sheath

Axon terminal

forms junction with other cells

Synapse

gap between neurons; communication point

Resting Phase

-70 mV; all ion channels/gates closed; neuron ready for an action potential; established by Na+/K+ pumps

Na+/K+ Pump

Moves one ATP, moves 3 Na+ ions out and 2 K+ ions in

Initial Stimulus

ions enter through channels in dendrites; reaches threshold potential is reached -55 mV; action potential is generated; otherwise return to resting phase

Depolarization

large, rapid increase in membrane potential; voltage gated channels open at -55 mV, Na+ ions flow into the axon

Repolarization

rapid reduction in internal charge; Na+ channels close; K+ channels open at +40 mV

Hyperpolarization

K+ flowing out through ion channels results in a lower-than-initial concentration; K+ ion channels close

Refractory Period

Na/K pump continues active transport; another action potential cannot be initiated during this time

Restoration of Resting Potential

-70 mV gradient restored until next stimulus.

Excitatory neurotransmitters

DEpolarize the neuron by allowing Na+ ions to enter the cell

Depolarize

close to neutral (& threshold)

Inhibitory neurotransmitters

HYPERpolarize the neuron by allowing Cl- ions to enter the cell

Hyperpolarize

further from neutral

Up-regulation

increased # of receptors “AMPLIFIES” the effect of a NT or hormone (+ or -)

Down-regulation

decreased # of receptors “DAMPENS” the effect of a NT or hormone (+ or -)