nervous system

central nervous system

brain and nerve chord (brain and spinal chord in vertebrates)

peripheral nervous system

all neurons and their projection that are outside the CNS

neurons

cells that send and receive electrical and chemical signals to and from eachother and other cells throughout the body (all animals except sponges)

cell body/ stoma

contains nucleus and organelles

dendrites

extension of cell body, single or branching

receive incoming signals

axon

extension of cell

• carries signals to other cells

• typically, single and varies widely in length

• axon terminals convey electrical or chemical signals to other cells

• typically occur in bundles wrapped by connective tissues called nerves

glial

surround and perform numerous functions

1000x more numerous that neurons

astrocytes

• metabolic support

• form the blood-brain barrier

• maintain stable concentration of ion in extracellular fluid

microglia

• participate in immune functions

• remove cellular debris

• myelin sheath

what is myelin sheath produced by

oligodenrocytes (CNS) and Schwann Cells (PNS)

radial glial cells

produce other cells and neurons

what are the three main types of neurons

sensory, motor, and interneurons

sensory neurons

-detect info from the outside world or internal body conditions

-also called afferent neurons- transmit to CNS

motor neurons

send signals away from CNS (efferent neurons) to elicit respone

interneurons

-form interconnection between other neurons

-critical in interpretation of info and elicit response

reflex arc

stimulus from sensory neurons sent to CNS, little or no interpretation (few to no interneurons), signal transmitted to motor neurons to elicit responese

quick and automatic response

what can generate electrical signals

neurons and muscle cells

membrane potential

'“gatekeeper”

resting membrane potential

when neuron is not sending a signal

the inside is more anions (-) while outside is more (+) cations

anions on the inside are drawn to the cations on the outside, so most ions are near the edge of membrane

electrochemical gradient

-imbalances due to differences inside/outside of the neuron

chemicals: k Na and cl

there is a charge w the chemicals

what are three factors that contribute to resting potential

1. sodium-potassium pump

2. ion specific channels allow passive ion movement

3. polarity

sodium- potassium pump

-requires ATP expenditure

pump 3 NA for every 2 K

ion specific channels allow passive ion movement

-membrane is more permeable to K

-K channels more frequently open at resting potential

polarity

more negative on the inside

voltage gates channels

open and close in response to voltage changes

chemical gated channels

open and close in response to chemical changes

relationship between frequency and nerve impulse

the higher the frequency, the greater the excitation level

resting potential

imbalance between potassium and sodium inside/outside

• membrane selectively permeable to K, but channels closed fro Na and Cl

• outside neuron- 10x more Na 5x more Cl

• inside neuron- 30x more K

action potential

rapid/brief change of a nerve fiber

• electrical potential of the impulse

• self-propagatin

• after passing a given point, membrane returns to resting

• at given point, channels for Na open adn Na diffuse in

• K is already diffusing out but increased at impulse