NEURO 205 - Neurobiology Exam One

Trepanation

The practice of drilling holes into live subjects' skulls to cure ailments such as headaches, mental disorders, or to release evil spirits.

Egypt

Edwin Smith discovered the oldest known surgical text in ancient Egypt; awareness of brain damage; belief that the heart housed soul, consciousness, and memories.

Hippocrates

father of Western medicine; believed that the brain was involved in perception and intelligence; emphasized the principle of "first do no harm”; ancient greece

Aristotle

believed heart was center of intellect and brain was a radiator to cool blood from the overheating of a seething heart - rational temperament explained by cooling capacity of brain; father of comparative anatomy

Galen

dissected animals and identified the cerebrum, cerebellum, and ventricles; deduced that cerebrum received sensations and memories, cerebellum commands muscles, and that the body balanced and moved four vital fluids to aid in the registration of sensation and movement - believed nerves were hollow tubs like vessels. theory lasted about 1500 years

Andreas Vesalius

anatomist, added more detail to brain structure, focus on ventricles

Rene Descartes

mathematician and philosopher, supported fluid-mechanical theory of ventricular brain function but believed it did not account for the full range of human behavior - human mental capabilities exist outside the brain in the “mind”, which is a spiritual entity that receives sensations and commands movements by communicating with the machinery of the brain through the pineal gland

white matter

continuous with body nerves, contains fibers (nerves and axons) to bring information to and from gray matter; on the inside of the brain

Gray matter

The outer tissue of the brain that contains cell bodies

Central division

brain and spinal cord

Peripheral nervous system

network of nerves throughout the body

Gyri

“bumps” on the brain

Sulci and fissures

Grooves on the brain

Lobes

Speculation that different brain functions are localized to different bumps on the brain

beliefs at end of 18th century

injury to brain can disrupt sensation, movement, and thought and can cause death; brain communicates with body through nerves; brain has identifiable parts with different functions; operates like a machine and follows laws of nature; focus shifted from ventricles to brain tissue

Luigi Galvani and Emil du Bois-Reymond

muscles twitched when nerves were stimulated electrically; brain can generate electricity; nerves are “wires” that conduct electrical signals to and from brain - not by fluid movement

Charles Bell and Francois Magendie

cutting ventral root resulted in paralysis (Bell), cutting dorsal root caused issues with sensation(Magendie); each nerve has a mixture of wires, some of which bring information to brain and spinal cord and others send information to muscles

• transmission is strictly one way, but sensory and motor nerve fibers are bundles for most of length until they are segregated at spinal cord (dorsal: sensory, ventral: muscle paralysis)

• bell proposed that origin of motor fibers is cerebellum and destination of sensory fibers is cerebrum

experimental ablation method

destroy parts of brain and test for sensory and motor deficits

Marie-Jean-Pierre Flourens

Used experimental ablation methods in birds to confirm that the cerebellum coordinates movement and the cerebrum is involved in sensation and perception.

Franz Joseph Gall

Proposed that personality traits could be related to dimensions of the head and bumps on the skull, leading to the study of phrenology and of localization

phrenology

“science” of correlating structure of head with personality; Gall collected and measured skulls of hundreds of people with various personality types; criticized heavily by Flourens - proved using ablations that phrenology was incorrect, but incorrectly maintained that all of cerebrum participates equally in cerebral functions

Paul Broca

located region of cerebrum responsible for speech production; observed frontal lobe lesion in dead brain of man who could understand language but not speak

Cerebral Localization

specific regions of the cerebrum are responsible for different functions, supported by experimental evidence in animals

Gustav Fritsch and Eduard Hitzig

electrical currents to exposed dog brain elicited discrete movements

David Ferrier

paralysis of muscles upon regional cerebrum removal

hermann munk

occipital lobe of cerebrum for vision

Charles Darwin

species of organisms evolved from common ancestor, differences due to natural selection - including inheritable behaviors; provides basis for animal models

Animal Welfare

animals need to be treated with respect

Institutional Animal Care and Use Committee (IACUC)

• animals used only for worthwhile experiments that promise to advance understanding of life

• minimize pain and distress

• all possible alternatives considered

Institutional Review Board (IRB)

ensures people are treated properly in experiments

Scientific Process

observation, hypothesis, replication, interpretation, conclusion, and verification by other scientists

Neurons

The basic functional unit of the nervous system, consisting of a central cell body and thin projections known as processes

Schwann

cell theory; all tissues composed of cells; dual existence as a distinct entity and building block in construction of organisms

Golgi

reticular theory (single continuous network)

Cajal

late 1800s - neuron doctrine (discrete units/cells)

• communicate by contact not continuity; used Golgi stains to draw neural circuitry

Microscopy

use of various types of microscopes to visualize and study neural structures; light microscopy not powerful enough to visualize gaps in neurons

Histology

study of stained tissues under a microscope

Nissl Stain

stains Nissl bodies (roughER in cell bodies), studies cytoarchitecture of neuronal tissue

Golgi Stain

silver chromate stain taken up by small, random percentage of neurons in their entirety - visualizes soma and neurites; proposed that neurons were fused together in reticulum

levels of neuroscience

molecular, cellular, systems, cognitive, behavioral, clinical

neuron doctrine

neurons are not continuous with each other and communicate through contact not continuity

neurons

sense changes in environment, communicate changes to other neurons and command bodily responses to the changes

glia

insulate, support and nourish neurons

cell body, soma, perikaryon

region surrounding cell nucleus, roughly 20 µm in diameter

cytosol

salty, potassium-rich solution separated from the outside from neuronal membranes

cytoplasm

everything confined within cell membrane including organelles but not nucleus

nucleus

spherical, centrally located, 5-10 µm diameter, double membrane known as nuclear envelope

chromosomes

contain genetic material DNA, genes assemble cell through protein synthesis in the cytoplasm

mRNA

carries genetic message from nucleus to cytoplasm

transcription

assemble mRNA from DNA to contain genetic information

promotor

RNA polymerase binds to initiate transcription

RNA splicing

introns removed and exons are fused together; exons removed to code for new proteins, known as alternative splicing

translation

assembling proteins from amino acids under mRNA

single nucleotide polymorphisms

either same nucleotides code for different proteins or different nucleotides code for same proteins

Rough Endoplasmic Reticulum

contains ribosomes where protein synthesis occurs; neurons have large quantities of rough ER to construct specialized membrane proteins

polyribosomes

multiple ribosomes working on same mRNA to produce multiple copies of same protein

Smooth Endoplasmic Reticulum

continuous with ER, folding of proteins, regulate internal concentrations of substances; sequester large scale changes in calcium to avoid signaling cell death

golgi apparatus

post-transitional chemical processing of proteins, sorting of proteins for delivery

mitochondrion

cellular respiration, “inhales” pyruvic acid and oxygen and undergoes Krebs cycle to form ATP (17 ATP per pyruvic acid); neurons have more mitochondria than other cells; mostly in soma and axon terminals; ATP used to establish membrane potential

Neuronal Membrane

encloses cytoplasm and excludes substances that float in the fluid that bathes the neuron; 5 nm thick with proteins

Cytoskeleton

composed of microtubules, microfilaments, and neurofilaments; dynamically regulating and are in continual motion

Microtubules

relatively large and run longitudinally composed of braided strands of the protein tubulin, created by microtubule-associated proteins; used for transport, 20 nm

axons (end before terminal) and dendrites

Microfilaments

about same thickness as cell membrane, composed of braided strands of actin; constantly undergoing assembly and disassembly; anchored to membrane by fibrous proteins lining the inside of the membranes; shape and stability, 5 nm

near plasma membrane

Neurofilaments

known as intermediate filaments; closely resemble the bones and ligaments of the skeleton in a ropelike structure; architecture, 10 nm

axons

neurites

thin tubes that radiate from the soma

axons

single axon of uniform diameter, thicker axons have faster impulses; branches extend at right angles; no ER and only few free ribosomes in mature axons, protein composition of axon membrane different than soma membrane; sends information; beginning (axon hillock), middle (axon proper), and end (axon terminal / terminal bouton); comprises white matter

voltage gated channels and Ca2+ at terminal allows for action potentials

axon hillock

tapers away from soma to form initial segment of axon proper; determines if signal is strong enough to send down axon

axon collaterals

branches to communicate with different parts of nervous system

recurrent collaterals

axon collateral returns to communicate with the same cell that gave rise to the axon or with the dendrites of neighboring cells

axon terminal

site where axon contacts other neurons / cells to pass information at the synapse; lot of mitochondria, synaptic vesicles, microtubules end here, high protein density in bouton

terminal arbor

short branches at the end of axons that form a synapse on dendrites/cell bodies in the same region

branching of axon

boutons en passant

axons form synapses at swollen regions along length and continue to terminate elsewhere

innervation

synaptic contact with another cell

axon cytoplasm

microtubules do not extend into terminal, terminal contains synaptic vesicles, inside surface of membrane facing synapse has dense covering of proteins, numerous mitochondria

presynaptic cell

cell sending signal, supplies axon

postsynaptic cell

cell receiving signal, supplies dendrite (not always, can be at axon hillock or soma)

synaptic cleft

space between pre and post synaptic membranes

synaptic transmission

transfer of information at the synapse

neurotransmitter

chemical signal stored in and released from synaptic vesicles

axoplasmic transport

movement of material down the axon

slow: ~1-10mm/day

fast: ~1000 mm/day

Wallerian degeneration

degeneration of axons when cut from cell body

anterograde transport

material enclosed in vesicles which are transported down the microtubules by Kinesin (kinesin only moves material from soma to terminal)

retrograde transport

terminal to soma, reverse of anterograde transport, powered by dynein; believed to provide signals to soma about metabolic needs of axon terminal

dendrites

rarely longer than 2 mm, extend from cell body and taper to a fine point, receive incoming signals; thousands of synapses with receptors that detect neurotransmitters in synaptic cleft

dendritic spines

structures hanging off dendrite believed to isolate chemical reactions triggered by some types of synaptic activation

• found that children with intellectual disabilities had fewer, longer, and thinner spines

• dendrites of a single neuron referred to as a dendritic tree, while each branch is a dendritic branch

• density determined by synaptic input and experience

• polyribosomes may be present

number of neurites

unipolar: one axon

bipolar: two neurites (one axon, one dendrite, largely in sensory neurons)

multipolar: 3+, comprises most neurons in the brain

pseudounipolar: sensory neurons from environment, no dendrites and one long axon

stellate

star shaped; can be spiny or aspinous; inhibitory neurons, CNS

pyramidal

pyramid shaped; all spiny; excitatory neurons; cortex

primary sensory neurons

neurons with neurites in sensory surfaces of body, such as skin and retina of the eye

motor neurons

axons that form synapses with muscles and control movement

interneurons

neurons form connections only with other neurons

Golgi type I / projection

long axons that extend from one part of the brain to another

Golgi type II / local circuit

short axons do not extend beyond vicinity of cell body

astrocytes

fill most of space between neurons, probably influences growth or retraction of neurite; regulates chemical content of extracellular space; metabolic support

• restricts spread and actively removes neurotransmitters

• contain own neurotransmitter receptors that can trigger electrical and biochemical events inside glial cell

• control extracellular concentration substances that could interfere with proper neuronal function - soak excess potassium

myelinating glia

oligodendroglial (CNS, attach to many axons) and Schwann cells (PNS, one cell per one axon) insulate axons in myelin sheath, gaps in sheath known as a node of Ranvier

node of ranvier

gap in sheath, booster station for neuronal signal traveling down axon

ependymal cells

line fluid-filled ventricles and direct cell migration during brain development; create cerebrospinal fluid by filtering blood from capillaries

microglia

phagocytes to remove debris, can migrate into brain from blood and interfere with brain functions and behavior, act as white blood cells, remodel synaptic connections and release cytokines

action potential

signals of fixed size and duration due to separation of electrical charge across membrane

excitable membrane

cells capable of generating and conducting action potentials