8-31 Neuron

synaptic terminal

the end of an axon where a neuron communicates with the next cell.

neurons, glia

two cell classes in nervous system

neurons

excitable cells specialized for electrochemical signaling

glia

traditional support cells, and sometimes help regulate neuron firing. they outnumber neurons and used to be ignored but are increasingly recognized as active participants in signaling

synapse

connections/gaps where neurons communicate with each other. One neuron can have many synapses

86 billion

how many neurons in the nervous system?

86 billion to 860 billion

how many glial cells in nervous system?

100 trillion–1 quadrillion

how many synapses in nervous system?

At the end of the axon, where it sends messages to the next cell.

where is axon terminal?

Branch off from the cell body and receive messages from other cells.

where are dendrites?

The central part of the neuron that contains the nucleus.

where is cell body?

Extends from the cell body and carries messages away from it.

where is axon?

cell body (or soma)

part of neuron contains nucleus of cell and endoplasmic reticulum, where proteins are synthesized

dendrites

the branches that receive the inputs to the cell as signals from other neurons axon terminals

axon

main output from cell body. usually one long process. sends info out of the cell in form of action potential

myelin sheath

fatty insulation around axon (made up of glial cells). broken up by non-insulated areas called “nodes of ranvier”

nodes of ranvier

non-insulated areas on axon terminal

axon terminal

site of neurotransmitter release, connection with other neurons

different

the structure of a neuron and an animal cell looks ________, but has the same parts

microtubules

what is the axon lined with? provides mechanical strength to the neuron, arranged in long parallel bundles down axons and dendrites. can be thought of as railroad tracks carrying neurotransmitter vesicles long distances down axon

smooth endoplasmic reticulum

stores calcium, helps with signaling and transport, and makes lipids needed for the neuron's cell membrane.

sensory neuron

neuron that carries info toward the CNS

motor neurons

neuron that carries info away from CNS to mucles/glands

interneurons

neurons that connect/process information within the CNS

unipolar

neuron shape with one main extension

bipolar

neuron shape with one dendrite and one axon

pseudounipolar

neuron shape with one extension that splits into two branches; common in sensory neurons

multipolar

neuron shape with many dendrites and one axon; very commo, including motor neurons

pyramidal

dominant neuron type in the cortex, including cortical language areas

afferent or efferent (SAME)

signals from neurons can be either _____

afferent

from the sensory organs to the brain (bottom up)

efferent

from the brain to the body, often motor (top down) ex: exerting cognitive effort

micro & macro

types of glial cells

microglia

involved in immune response to respiratory infections, cleans up waste from neurons (removes necrotic dying cells from phagocytosis)

astrocytes, oligodendrocytes, and schwann cells

types of macroglia

astrocytes

surround synapses, form blood brain barrier, protect and metabolically support neurons

oligodendrocytes

generate myelin in central nervous system (insulates nerve cells and makes communication faster)

closely

gial cells are mixed throughout the brain, interact ____ with the neurons and their dendrites, help form the blood-brain barrier which controls what can enter the brain from the blood and helps protect the brain

schwann cells

generate myelin in peripheral nervous system (insulates nerve cells and makes communication faster)