324 exam 1

two major theories that helped neuroscience in 19th century

Darwin’s evolution and natural selection, Schwann’s cellular theory

Golgi stain

mix of silver nitrate, absorbs 10% of neurons completely

reticular theory

presented by Golgi, the base unit of the brain is a giant continuous net

why reticular theory is wrong

electricity only moves in one direction, different neurons and branches

neuron doctrine

Ramon y Cajal says the base unit of the brain is one neuron

neurogenesis

birth of new neurons, only happens in the embryo in humans

gray matter

cell bodies of large neurons and all of small neurons

white matter

axons covered in myelin

nissl stain (crassly violet)

binds to the cell body and shows gray matter

fiber stain

shows the white matter by binding to myelin

basic cell types in the brain

neurons and glia

direction of neural signals

dendrite, soma, axon, terminals

types of neurons

1000s but most common are pyramidal, stellate, purkinje

pyramidal cells

main neuron of the cerebral cortex

stellate cells

star shaped, found in abundance in subcortical regions

purkinje cells

found in the cerebellum , connected to tens of thousands of cells at once

projection neurons

they have long axons that project to a different brain area

interneurons

they tend to be smaller, mostly stellate, short axons that only project locally

benefit of synapses

creates opportunity to modify and modulate a signal

microglia

immune system role in the brain

rest (microglia)

small glia covered in receptors that look for evidence of intruding things in the brain like metabolic waste

prime state (microglia)

when they detect a pathogen and go find it

active (microglia)

they blow up into a bigger size and consume the bacteria and wastes

Macroglia

myelinating glia including Schwann cells, oligodendrocytes, and astrocytes

Schwann cells

wrapped completely around the axon, they myeline a single axon in the PNS

oligodendrocytes

they myelinate several axons, work in the CNS

astrocytes

wrapped around capillaries, part of the blood brain barrier, mediates what the brain needs like oxygen, control the environment (i.e. buffer sodium in and out)

gap junctions

proteins on usually astrocytes that act like pieces of lego clicking together, makes it so that the astrocytes act like one giant cell or reticulum

presynaptic site

vesicles and neurotransmitters

tripartite synapse

presynaptic site, postsynaptic, astrocytes

central dogma

DNA codes for mRNA and mRNA creates protein

transcription

DNA to RNA

translation

RNA to protein

histone modification

the more tightly it is wrapped, the less reachable DNA is for transcription

ribosomes

proteins that read the RNA

Golgi apparatus

exports proteins to their terminal location

mitochondria

they eat oxygen and sugar and produce adenosine triphosphate aka ATP as well as carbon dioxide

membrane of a cell

made from a phospholipid bilayer → two molecules with heads facing outward and tails facing in

phospholipid bilayer

has hydrophilic heads (water passes but fat bounces off) and lipid tails (interacts with fats but water bounces off)

cytoskeleton

creates structural stability and allows for kinesin (transport of proteins from cell body to terminal) and dynein (transport of proteins from terminal to cell body)

axodendritic synapse

synapse between axon and dendrite

axosecretetory synapse

axon terminal secretes directly into the bloodstream

dendrites basic forms

spiny and non-spiny, spines make it so that modification becomes more contained where effects on non-spiny neurons are more diffuse

spiny neurons

glutamate neurons

non-spiny neurons

usually GABA, they can be other things too but gluatamate

primary division in the vertebrate nervous system

Central (CNS) (brain and spinal cord) and peripheral (PNS)

first division of PNS

somatic (external, mostly conscious) and autonomic (internal, mostly non-conscious)

ANS efferents

sympathetic and parasympathetic NS

sympathetic NS

mobilizes energy, e.g. heartbeat becomes faster to bring more blood to brain, airways dilate, digestion slows down, fat and glycogens storage broken down to get more ATP

parasympathetic NS

conserves energy, digestion speeds up, fats and glycogens are stored

sympathetic and parasympathetic NS relationship

not always mutually exclusive, not completely global

nucleus

cell clusters in the CNS

ganglion

cell clusters in the PNS

tract

bundles of axons in the CNS

nerve

bundle of axons in the PNS

anterior/rostral

front, toward the nose

posterior/caudal

back, toward the tail

superior/dorsal

toward the spine/sky

inferior/ventral

toward the ground/belly

medial line

the line of symmetry in the middle of the brain

lateral

term used as we move away from the medial line regardless of which side

coronal section

front to back view of the brain, sliced like toast

horizontal section

sliced along the horizon, creating a top and bottom part of the brain

mid-sagittal section

cut through the medial line, creating a left and right side

spinal cord sections (anterior to posterior)

cervical, thorasic, lumbar, sacral

the reason spinal cord narrows from cervical to coccygeal

more motor neurons are coming in from the brain and they become less as we move to caudal

sensory component of spinal cord

gets larger as we move to rostral

cauda equina

the nerves fraying from the spinal cord

gray matter in spinal cord

is inside in an H shape

white matter in spinal cord

outside, opposite of how it is in the brain

dorsal side of spinal cord

afferent, where all the sensory information is coming in

ventral side of spinal cord

efferent, where the motor information is going out

3 divisions of brain

forebrain, midbrain, and hindbrain (rostral to caudal)

5 divisions of brain

telencephalon and diencephalon (forebrain), mesencephalon (midbrain), metencephalon and myelencephalon (hindbrain)

myelencephalon

medulla, has lots of tracts connecting the brain to the spinal cord

functions of medulla

control of involuntary life sustaining functions such as heartbeat and swallowing

medulla injury

often fatal, doctors will be reluctant to perform surgery here

reticular formation location

runs through the myelencephalon to the mesencephalon

function of reticular formation

~100 nuclei critical for arousal, wakefulness, attention, sleep

reticular formation injury

causes major disruptions to life and can be fatal

metencephalon

lots of tracts, also houses the reticular formation, has a dorsal (cerebellum) and ventral part (pons)

pons

large white matter bulge continuing from the medulla, controls a part of breathing and is connected to many functions

cerebellum

10% of brain volume and has half of all brain neurons, corrects movement, important for motor coordination, smoothness, and accuracy

damage to cerebellum

correcting movements becomes conscious, alcohol affects it the most which is why drunk people will have trouble coordinating their body

mesencephalon

the midbrain, comprised of a roof (tectum) and a floor (tegmentum)

tectum

has a superior and inferior colliculi that orient our body and attention toward stimuli involuntarily

superior colliculi

sensory and motor region, brings in sensory information and adjusts our eye movement accordingly

inferior colliculi

audition with respect to head/body movement

damage to tectum

causes problems with unconscious vision but not conscious vision

tegmentum

contains part of reticular formation, carries afferent and efferent fibres, periaqueductal grey (PAG), DA producing regions (substantia nigra and VTA), and red nucleus

periaqueductal grey function

controls behaviours that emerge under intense or emotional moments like screaming, flinching, punching, etc. related to pain relief

DA producing regions

substantia nigra, ventral tegmental area

red nucleus

plays a role in species specific behaviours (dogs barking, mice squeaking), not much role in humans except when babies are learning to crawl and our arms swinging when we walk

pattern in tegmentum areas

all are motor related and outside of conscious control

damage to tegmentum

motor related changes, i.e. parkinson’s caused by loss of substantia nigra, side effects of anti-psychotics being an overactive red nucleus which leads to jerking movements

diencephalon

part of the forebrain, comprised of 2 structures (thalamus and hypothalamus)

thalamus

many nuclei inputting from sensory sensory systems, cerebellum, basal ganglia. often called a sensory relay centre (which is true but incomplete)

corticothalamic loops

reciprocal circuits that process sensory information, regulate attention, and control brain states

role of interneurons in thalamus

they block signals (why we don’t hear when we’re asleep)

damage to thalamus

leaves people in a minimally or non conscious state