nervous system

-brain plus spinal cord -composed on interneurons (association neurons) 99% of all neurons in humans

-collects information and initiates reponses 1)Sensory(afferent) neurons-impulses from sensory receptors to CNS 2)Motor (efferent) neurons-impulses from CNS to effectors; muscles and glands -somatic nervous system: motor neurons that stimulate skeletal muscles -autonomic nervous system: motor neurons that stimulate smooth muscles, cardiac muscles and glands,

Sensory(afferent) neurons-impulses from sensory receptors to CNS

Motor (efferent) neurons-impulses from CNS to effectors; muscles and glands -somatic nervous system: motor neurons that stimulate skeletal muscles -autonomic nervous system: motor neurons that stimulate smooth muscles, cardiac muscles and glands,

somatic(conscious control) nervous system: motor neurons that stimulate skeletal muscles

autonomic nervous system: motor neurons that stimulate smooth muscles, cardiac muscles and glands,

Dendrites-branches off Axon-tube Neurons are srurrouned by supported nerugolical cells 1) Schwann cells produce myelin sheaths around axons in PNS 2)Oligodendrocytes do the same in the CNS in PNS bundles of axons form nervres

1) Schwann cells produce myelin sheaths around axons in PNS

Oligodendrocytes produce myelin sheaths around axons in CNS

Brain to body

Body to brain

the ability to create and alter electric potential across plasma membrane

the electrical gradient between a resting neuron and surrounding environment

Fixed anions with cells (proteins and nucleic acids) negative charge membrane more permeable to K+ than to Na+ (leakage channels) The concentration gradient favors k+ out of cell electrical gradient: k+ attracted to anions in cell

resting membrane potential (-70mV)

A nerve impulse or action potential is produced

Action potentials: a rapidly moving change in electrical membrane potential along the axon of a neuron -action potentials are caused by voltage-gated ion channels two types: Na+ and K+

1)Stimulus- gated channels open in response to chemical signals (Action potential beings at -55mV) 2)Voltage-gated Na+ channels now open, allowing NA+ to enter the cell via diffusion (pos outside, neg inside) 3)Na+ ions cancels out RMP (depolarization) Na+ channels close in response 4)Depolarization causes voltage-gate K+ channels to open, K+ moves outside of cell (repolarization). k+ channels close in reponse 5)action potential passes: membrane returns to RMP Left to right of axon, self-propagating wave (burning fuse)

Does not return cell to RMP. There is now a high concentration of Na+ inside cell and K+ outside. Thus a new action potential is not possible -NaK pump, pushes Na out of cell and K back in using energy, corrects repolarization Action potentials are an all-or-nothing event.

alive, just need to get to 30mV

Cundciton velocity on an AP is a function of axon diameter and the presence or absence of myelin

when action potential passes along a neuron is must cross a synapse -axon terminals contain vesicles of neurotransmitters that relay messages across synapse 1)Action potential opens up calcium channels and trippers the inward diffusion of Ca+ which causes synaptic vesicles to bind with the plasma membrane and then release neurotransmitters into the synapse 2)Neurotransmitters bind to receptor proteins on postsynaptic cell, opening their gated ion channels 3)if the resulting voltage change across the cell reaches -50mV an action potential in the postsynaptic cell is initiated 4)Neurotransmitters are rapidly removed from synaptic cleft by enzymatic digestion and reuptake by the neuron 5) neuron reabsorbs and resynthesizes components into neurotransmitters