PSYC-2900 Chapter 2.1

central nervous system (CNS)

a division of the nervous system comprised of the brain and spinal cord

peripheral nervous system (PNS)

a division of the nervous system comprised of all of the nerves that receives external information/stimuli and directs it between the central nervous system and the rest of the body

nerves

composed of a membrane sheath, bundles of axons, and small blood vessels

neurons

the information-processor/transmitter of the nervous system. includes 3 types: sensory neurons, motor neurons, and interneurons

soma

the cell body of the neuron containing the nucleus (DNA) and cellular machinery. the shape will differ depending on the type of neuron

dendrites

tree-like branches attached to the soma that receive signals using their receptors (receptor sites) on which substances bind to

axons

thin, cylindrical structures extending from the soma that carries action potentials to the terminal buttons of the neuron. depending on the type of neuron, it may be surrounded by a myelin sheath. running on the inner length of it, microtubules move substances between the soma and terminal buttons

myelin sheath

a fatty substance found surrounding the axons of some neurons, giving a lighter appearance. (i.e. the white matter of the brain) it provides insulation to the neuron, and speeds the movement of neural messages within the axon

terminal buttons

bud-like structures at the end of an axon’s branch. they form synapses with other neurons and release neurotransmitters into the synapse

synapse

a junction in between the terminal buttons of one neuron and dendritic/somatic membrane of another neuron

neurotransmitters

molecules/chemicals that are sent between synapses

multipolar neurons

a shape-classified neuron that has multiple dendritic branches and multiple axon branches. unless the neuron is specified to be uni/bipolar, all other neurons are considered to be under this class

unipolar neurons

a shape-classified neuron that has one process (axon) extending from the soma that serves both functions of the dendrites and axons. they are common in invertebrates, and are not present in humans

pseudounipolar neurons

a shape-classified neuron that has that has one process (axon) extending from the side of the soma, which then splits into two branches, one extending into the PNS and one to the CNS. the process serves functions of the dendrites and axons. they play a role in transmitting information related to touch, proprioception, pain, and temperature

bipolar neurons

a shape-classified neuron that has one axon and one dendritic branch extending from the soma. they play a role in transmitting information related to sight, smell, and hearing

proprioception

the sense of the body’s position and movement

anaxonic neurons

a type of neuron that lacks an axon, and can therefore only receive signals, and cannot send signals, and instead communicate through their dendrites. they are found in the retina and the brain

membrane

the outer layer of a neuron

cytoskeleton

a layer within the neuron that extends throughout the cell to transport materials and maintain shape. it is made of 3 kinds of protein strands, including microtubules

microtubules

strands of proteins found within a neuron that act as conveyer belt between the soma and terminal buttons of the axon

cytoplasm

a clear, viscous fluid within the cell body of a neuron that holds organelles and molecules. it is the site of most chemical activities in the cell, including protein synthesis

mitochrondria

a cell organelle within the cytoplasm that produces adenosine triphosphate (ATP)

nucleus

a cell organelle within the cytoplasm that contains genetic material, such as chromosomes made of deoxyribonucleic acid (DNA)

protein synthesis

initiated by genes, it consists of 2 steps:

1. transcription from DNA to messenger RNA (mRNA) within the nucleus

2. mRNA leaves the nucleus, attaches to ribosomes in the soma/cell body where it is translated into a protein

enzymes

proteins that control chemical reactions for the cell

(the construction & demolition crew of the cell)

axoplasmic transport

a process that moves materials between the soma and terminal buttons of the axon. small vesicles hold the materials being moved, attach onto microtubules, and are carried to their destination

anterograde axon transport

axon transport in which vesicles holding materials are carried towards the terminal buttons of the axon

retrograde axon transport

axon transport in which vesicles holding materials are carried towards the soma

glial cells

cells that support and protect other cells in many different functions depending on the type. 3 types include astrocytes, oligodendrocytes, and microglia

astrocytes

a type of star-shaped glial cell found in the CNS that sends branches with u-shaped buttons to the soma of neurons and to capillaries. they use phagocytosis to digest debris (i.e. waste/dead cells) and send it to the vascular system

oligodendrocytes

a type of tube-shaped glial cell found in the CNS that provide support to axons by producing myelin sheaths

nodes of ranvier

exposed parts of the axon between sections of myelin, that allow ions to diffuse in and out of the neuron, propagating action potentials

microglia

the smallest type of glial cell that act as phagocytes, and serve as part of the immune system. they are responsible for inflammatory reaction to damage by cleaning dead cells, and may have a constructive role during development

schwann cells

a type of supporting cell found in the PNS that provide one segment of myelin sheath by surrounding its’ entirety around an axon

blood brain barrier (BBB)

a protective layer found in the CNS that is produced by the cells in walls of the brain’s capillaries, and reinforced by astrocytes. it is selectively permeable, allowing water and small, neutrally-charged molecules in/out, however, larger substances require active transport to enter/exit, using ATP. it regulates the composition of extracellular fluid by protecting the brain from harmful substances, and allowing nutrients to reach the brain

(e.g. can detect toxic substances entering blood and induce vomiting)

area postrema

a weak region of the blood brain barrier