Ch. 2.1 The cells of the nervous system

Neurons

units in the brain that process information: taking it in, integrating it, and then sharing that info to other neurons

Do neurons touch eachother?

no, it was debated though since they were so small, scientists couldn’t tell early on. but santiago ramon y cajal stained neurons to find out theres a gap

Neuron Doctrine

• neurons are structurally, metabolically, and functionally independent from other cells in the brain

• info is shared between the synapses (tiny gaps)

what is meant by neurons are contiguous

neurons are close together but not continuous or connected

Synapses

the small gaps in between neurons

what organelles do neurons have?

• Golgi apparatus

• cell body

• mitochondria

• ribosomes

What are the 4 zones of the neuron

• Input zone

• Integration zone

• Conduction zone

• Output zone

What are the parts of the neuron

• dendrites, dendrite spines

• cell body

• axon

• axon collaterals

• axon terminals

dendrites

extensions of the neuron that take in information from the synapses

cell body

incorporates the info taken in by the cell, so it can decide whether to send a neural signal

axon

uses electrical charge to move info from cell body to the axon terminals

axon collaterals

axon spilts into multiple branches/path towards the axon terminals

axon terminals

sends info into the synaptic gap so it can reach other cells

Input zone

where dendrites receive info from other neurons/cells, or environment

Integration zone

around the cell body which decides whether that information gets passed on / make a neural signal

Conduction zone

information is electrically moved to the end of the neuron through the axon. may spilt into axon collaterals (multi paths)

Output zone

area where info can be transferred to other neurons at axon terminal and through the synaptic gap

Motor neurons

responsible for bodily movement (ex. glands, organs, walking), its axons are longer in order to reach synaptic gap on the muscles.
when the brain gives a command, these neurons contract

Sensory neurons

take in sensory information from the skin (peripheral tissue) and move it through long axons, until it reaches spinal cord and the brain.
different forms based on type of sensory info (light, touch)

Interneurons

neurons in the brain; they have short axons, intricate dendrite branches, pass info to other neurons, throughout brain neural network

vertebrae (spine) neurons are fking long

up to a meter long to reach the brain, different sizes based on function of neuron

3 neuron shapes

• multipolar

• bipolar

• unipolar

multipolar neuron

most common neuron shape: has lots of dendrites and a single axon

bipolar neuron

has a single dendrite, and a single axon terminal, commonly the shape of vision sensory neurons

unipolar neuron

this neuron has 2 axon collaterals coming out the cell body, with dendrite like branches at one end and axon terminals at the other. (type used to transfer info form body to spine)

presynaptic neuron

the area of the synapse that releases neurotransmitter

post synaptic neuron

area of the synapse that takes in and responds to neurotransmitter

where are the synapses at the dendrites

synaptic gaps are formed on dendrite spines, or shafts

where are the synapses at the axon terminal

axon terminals will form synaptic gaps with cell bodies, or dendrites

Synapse - 3 parts

• presynaptic membrane

• synaptic cleft

• postsynaptic membrane

presynaptic membrane

membrane on axon terminal that releases neurotransmitter (info)

synaptic cleft

the gap between the presynaptic and postsynaptic membranes

post synaptic membrane

membrane on the dendrites or cell body of postsynaptic (recieving) neuron. takes in information after reacting to neurotransmitter from presynaptic neuron

neurotransmitter

chemicals released from presynaptic neuron, that get passed to postsynaptic neurons

synaptic vesicles

bubbles in the presynaptic neuron carrying neurotransmitters, these bubbles, fuse with membrane, releasing neurotransmitters into the synaptic cleft to be recieved by post synaptic neuron

how do neurotransmitters get from neuron to neuron?

1. electrical signal from axon moves down to axon terminals

2. in reaction to electrical signal, synaptic vesicles (carrying neurotransmitters) fuse into the presynaptic membrane and release the neurotransmitters into the synaptic cleft

3. neurotransmitters spread in cleft space and click in with neurotransmitter receptors on postsynaptic membrane

4. these receptor (proteins) react to neurotransmitter molecules, that electrically exictes, most likely leading post neuron to release its own neurotransmitter at its axon terminals

5. the neurotransmitters are released after binding

neuroplasticity (in relation to neurons)

neurons are always readapting/molding their connections to other neurons after experiences

axonal transport

transports from cell body to axon terminals in both directions. materials are transported faster along the outer axon, and slower transportation is done in inner axon

anterograde

retrograde

Anterograde transport

transports materials from cell body to axon terminals

Retrograde transport

transports materials from axon terminals from cell body

Glial cells (list types)

cells that support the neural system but also comminucate with eachother and with neurons.

• astrocytes

• microglial

• oligodendrocytes

Astrocytes

star shaped, support blood flow which helps give neurons their materials, connected to neuron synapses, and monitors other synapses, speculation that they communicate with neurons

more active neurons recieve more blood

Microglial

small glial cells that remove waste/debris from damaged cells

Myelin

protective insulating layer around axon speeding up axon conduction

Oligodendrocytes

forms a myelin sheath/protective layer,. for brain and spinal cord cells (Central Nervous System)

Schwan cells

used as a protective layer for the myelin of cells outside the brain and spinal cord (Peripheral nervous system)

Nodes of Ranvier

spaces on the axon with no myelin sheath, causes solitary conduction. since electrical signal is forced to jump to next node. this is much faster than going straight down.

some diseases attack this area