Nervous system/ tissue

Three overlapping functions

sensory input, integration, motor output

Neuroglia

glial cells that support and protect neurons

Neurons types

bipolar, unipolar, multipolar, pyrimidal

Astrocytes

Most abundant and versatile neuroglial that are in the CNS

functions of astrocytes

cover overs capillaries, anchors neurons to supply lines, monitor local environment, guide migration of young neurons

microglial cells

primary immune cell of the CNS

ependymal cells

ciliated cells that central cavities of thebrain and spinal cord

Oligodendrocytes

produce myelin sheath in CNS

satellite cells

surround neuron cell bodies in PNS

Schwann cells

produce myelin in PNS by surrounding the fibers

characteristics of neurons

long lifespans, don't divide, high metabolic rate, conduct electrical impulses

cell body (soma)

contains the nucleus and other parts of the cell needed to sustain its life

Chromatophilic substance (Nissl's Bodies)

very active/developed ribosomes and RER

Neurofibrils

bundles of intermediate filaments (neurofilaments) that provide structure & cell shape

Lipofuscin

byproducts of lysosomal activity; pigments that accumulate with age

Dendrites

Branchlike parts of a neuron that are specialized to receive information.

Ganglia

cell body outside of CNS

Axon

conducting region; nerve impulses travel down axon. Neurotransmitters are released at the end. When split=axon collaterals

Axon Hilloclk

'interprets' all the signals coming into the cell body and where action potentials are started

anterograde vs retrograde transport

away from cell body vs to cell body

myelin sheath in PNS

from wrapped schwann cells

nodes of Ranvier

Spaces between adjacent Schwann cells

speed w/out myelination

Increases speed at which electrical signals travel down the axon• Unmyelinated fibers: impulses travel as continuous waves• Myelinated fibers: impulses 'jump' along the axon length

myelin sheath in CNS

from Oligodendrocytes

matter in the CNS

White matter: myelinated fibers

Grey matter: nonmyelinated fibers

mulitpolar

most popular major CNS cell

motor (efferent) neurons

neurons carry impulses away from the brainand spinal cord to effector organs. Cell bodies in CNS

Interneurons (association neurons)

carry impulses between motor and sensory neurons. 99% of all neurons

sensory (afferent) neurons

neurons carry impulses to the brain and spinal cord

Leakage (non-gated) channels

always open

Gated channels (3 types)

form a molecular gate that changes shape (conformational change)to open and close in response to specific signals

Ligand-gated (chemically)

open/closewhen an appropriate chemical binds

voltage gated

open/close in responseto changes in the membrane potential

Mechanically gated

respond to aphysical change of a receptor

Resting Membrane Potential

-70mV

Na+/ K+ pump

Pumps 3 Na+ out of the cell Pumps 2 K+ into the cell

Repolarization

A return to a resting membrane potential:

graded potential

Signals that operate over short distances and decay with distance

Can result from either depolarization or hyperpolarization

Magnitude depends on signal strength

Cause gated ion channels to open

Action potentials:

all or nothing long-distance signal of neurons

Production of an action potential

requires depolarization that meets a critical level = threshold• After meeting threshold, action potential become self-generating

events of action potential

1: resting stateL all na+ and k + channels are closed

2.: depolarization: na+ channel open

3: repolarization: Na+ channels are inactivated and K+ chnnaels open

4: Hyperpolarization: some k+ channels eemain open and Na+ channels reset

refractory period

Membrane can't respond to another stimulus

absolute refractory period

: from opening of na channels until the channels reset

Ensure every action potential is separate

Keep it moving in one direction

relative refractory period

follows the absolute refractory period and corresponds to most but not all na channels returning to rest and k channels are still open

Repolarization is occurring

The threshold for new AP is higher

two types of synapses

electrical and chemical

Synaptic delay

time it takes for a neurotransmitter to get released to bind to a receptor

Transmission across the cleft is the rate-limiting step of the neuronal transmission

Axodendritic synapse

synapses between the axon ending of a neuron and the dendrites of another neuron

2 other common types of synapase

Axosomatic and Axoaxonic

less common type of synapse

Dendrodentric and Somatodendritic

excitatory postsynaptic potential (EPSP)

Neurotransmitters depolarize the postsynaptic membrane

Inhibitory synapses (IPSP)

Neurotransmitters hyperpolarize the post synaptic membrane

Inhibitory synapses on axon hillock

most effect when located between exoctory synapse and the axon hillock most effect when located between exoctory synapse and the axon hillock

synaptic potentiation

repeat or continuous use enhances the presynaptic neuron's ability to excite the postsynaptic neuron

Neurotransmitter types

acetylcholine, biogenic amines, amino acids, peptides, purines, gases and lipids

Neuromodulators

Affect the strength of synaptic transmission