PSYC 304: Midterm 1

neuroscience

study of relationship between brain and behaviour

common neuroscience metaphors

explain what is not possible to observe/know yet

• Galen’s humours

• brain/heart as source of intelligence

• hydraulics

• dualism vs. materialism

• electricity

• Bell and Magendie - direction of charge

• biological machine vs. spirit

• computers

two initial schools of thought for the brain

• doctor: brain is source of intelligence

• philosophers: heart is source of intelligence

evidence for interest in the brain in prehistory

trepanation in ancient skulls (holes drilled in the brain, likely to treat mental health concerns)

ancient Egypt’s brain interest

didn’t ascribe too much value to it, instead preserved the heart during mummification

ancient Greece’s interest in the brain

• Hippocrates: brain injuries are from emotional/intelligence problems

• Aristotle: heart is source of intelligence

ancient Rome’s interest in the brain

Galen: humans and animals are the same - animal dissections

• identified cerebellum (as motor control) and cerebrum (as memories)

• ventricles and nerves

• the 4 humours

• knowledge lost until the Renaissance

materialism in science

assuming that everything in the universe can be physically observed, correspond to physical laws - everything in brain can be observed/measured

brain understanding from Renaissance to the 18th century

• hydraulics

• Descartes

• White/grey matter mapping

• ventricles

• gyri and sulci

the brain in the 19th century

• Benjamin Franklin and electricity - brain functions through electricity? (Galvani and du Bois-Reymond)

• Bell and Magendie found that the “wires” are nerves

• localization of function (Fluorens, Gall, Broca)

• Darwin’s natural selection

• Schwann’s cellular theory

Golgi’s stain

• mixed silver and nitrate to stain neurons, able to see them individually

• reticular theory

2 theories of neuron function

• Golgi: neurons are connected and continuous, signals travel from inside a neuron to another, like mesh

• Cajal: drew neurons in detail and noticed a variety of cell types - neuron doctrine: base unit of nervous system is the neuron (was the more right one)

Ramon y Cajal’s neuron drawings

drew neurons in detail and noticed a variety of cell types

• neuron doctrine: base unit of nervous system is the neuron

• discovered some neurons input info and some output

• discovered synapse

20th century brain

when modern neuroscience was born

the brain as a computer

modern metaphor - binary was chosen because of neurons, neuroscience uses computer-like terms (wiring, coding, processing)

• computers represent info, brains construct info

levels of analysis

1. molecular neuroscience

2. cellular neuroscience

3. systems neuroscience

4. behavioural neuroscience

5. cognitive neuroscience

human brain size

2-3% of body weight, ~3 lbs - consumes 20% of your energy/oxygen

• slightly larger in men, huge individual variation

make-up of the human brain

• neurons (<100 billion, more than half in cerebellum), glia (support cells), stem cells, blood vessels

• consistency of soft tofu

• convolutions = wrinkles on brain

• cells are not replaced

adult neurogenesis?

cell regeneration

• identified in fish and birds

• found some neurogenesis in the hippocampus until 13 years old - not significant enough

locust brain

• nervous system clusters - loosely built

• a lot of sensory organs

• structures ensure speed and reflexes

fish brain

• same regions as us, with small cerebral cortex

• midbrain proportionally aligns with ours

• tectum responds intensely to stimuli, cerebrum is small so not good at pulling away

rat brain

• cerebellum and cerebrum are larger and cover midbrain (not wrinkled)

• olfactory bulb at the end

dog brain

cerebrum is getting larger (wrinkles), olfactory bulb is at the front (strong smell), strong interaction/direction skills, empathetic

monkey brain

• spinal cord goes out below animal’s head like animals

• convolutions

chimpanzee brain

• similar to humans - big cerebrum, convolutions

• smaller frontal lobe

• understand tool use, theory of mind, sense of self

developments as the brain gets more human

• more convolutions

• more system layering

• frontal lobe and forebrain getting bigger

human brain vs. dolphin brain

dolphin brain is huge, with more convolutions - have vocab, play, interact with humans, don’t have limbs/dexterity

human brain vs. parrot brain

can count, talk, answer spoken questions, but have small and smooth brains

brain size significance

doesn’t carry the most weight, but humans do have the disproportionally largest brain for body size

• doesn’t give us function

measuring brain cell density

counting neurons per unit of mass/volume - intelligence correlated with sophistication of cellular connections

grey matter

cell bodies, unmyelinated neuorns

white matter

fatty substane, myelin, makes it white (axons moving info to different parts of the brain)

brain matter staining

• nissel: darker stains = grey matter, nucleic acids in rough ER, cell bodies

  • Best for seeing cell bodies, neuro-degeneration, neuron density

• fibre: darker stains = white matter, binds to myelin, won’t show whole cells

  • Best for seeing white matter and nerve fibres

• golgi: darker stains = neurons and dendrites

  • Best for seeing the entire neuron

neurons

communicating cells, specifically through axon (carry info very fast through action potential)

• specific commands are for specific areas

• many types, but similar design

• dendrite → soma → axon → terminals

glia

communicating cells, support cells - build brain foundation

• build glia

pyramidal neuron

in the cortex, travels deep into brain

stellate neurons

in cells in central nervous system

purkinje neurons

cells in the cerebellum

projection neurons

often modifying, have long axons that project to different brain areas

• long axon

• pyramidal and purkinje

interneurons

star shaped, projected locally - inhibiting and synchronizing, generate patterns of brain activity

• short axon

macroglia

regulate retinal metabolism, modulate neuron function and blood vessels

• astrocyte, schawan cell, oligodendrocyte

blood-brain barrier

membrane between blood and brain that keeps brain healthy from viruses, brain is often blocked from immune system

microglia

immune system for the brain - protect from foreign pathogens

• covered in receptors

• absorb foreign objects and dissect them

Schwan Cell and Oligodendrocytes

myelinating glia (myelinate axons)

• Schwan: only myelinate single axons for peripheral nervous system

• Oligodendrocytes: myelinate several axons, speed up signals

astrocytes

glial networks - half of the blood-brain barrier, mediate nutrition for the brain (oxygen, glucose)

• maintains brain environment (synapse)

• repair scarring

• gap junctions that create pathways to neighbouring ones that also form reticular nets

synapse

space between neurons - neurotransmitters released at pre-synaptic, bind at post-synaptic receptors after floating through synapse

• pre-synaptic (axon terminal), synapse, post-synaptic (dendrites), astrocyte signals

• astrocytes control environment and release chemical messages

• glia shape conditions

• communication = voltage

central dogma of molecular biology

DNA → mRNA → Protein

proteins

main character of brain activity, do everything including being the basis for neuronal function

• coded by RNA

• many of them combine to create genes to create traits

soma

the nucleus in the neuron - tell when and where to code genes, makes RNA

transcription

process by which info in a strand of DNA is copied into a new molecule of messenger RNA (mRNA)

• occurs if activators are present and the repressor is absent

• little/no transcription occurs if only one activator is present

transcription factors

signalling mechanisms that will determine likelihood of gene being transcribed into RNA

• Epigenetics (changes gene expression) - depends on tightness of histones around a gene (methylation)

ribosomes

in endoplasmic reticulum - produce proteins

endoplasmic reticulum

membrane pieces that can be transported through out the cell by the golgi apparatus (rough or smooth)

mitochondria

powerhouse of the cell - produce ATP (main energy source)

cell membrane

barrier for any foreign threats trying to enter the cell - has pores for things that should be going in and out

cytoskeleton

structural integrity of the cell, transportation path to and from axon (kinesin = anterograde, dynein = retrograde)

• consume ATP to continue transportation

axon

conducts axon potentials in neurons, myelin sheath

dendrites

arms of neurons that receive neural communications

• Dendritic spines = spiny neuron (almost all are glutamate receptors)

• No dendritic spines = non-spiny neuron (GABA receptors)

glutamate receptors

bind to the main excitatory neurotransmitter in the brain

GABA receptors

bind to the main inhibitory neurotransmitter in the brain

central nervous system

brain and spinal cord

• damage: anything from issues with hormone regulation/memory categorization to death

peripheral nervous system

outside of brain and spinal cord - somatic and autonomic nervous system

• damage = sensory system impairments, affects brain’s ability to communicate with muscles/organs

somatic nervous system (SNS)

external environment, mostly conscious - bringing info to the brain, acting in outside world

• afferent signal: sensory receptors to brain

• efferent signal: motor signals from brain to body

• damage = cramps/spasms/loss of control (motor nerve damage), loss of touch sensation/numbness (sensory nerve damage)

autonomic nervous system (ANS)

internal environment, mostly non-conscious sensory info (ex. stomach acid)

• signals to internal signals - sense some like heart rate, stomach ache, headache

• efferent: sympathetic and parasympathetic NS

• damage: nerve damage - high blood pressure, sexual difficulties, difficulty digesting food

sympathetic nervous system and parasympathetic nervous system

SNS: mobilizes energy, fight of flight

• damage = metabolism problems, heart rate issues, dizziness, sexual dysfunction

PNS: conserves energy

• damage = constipation, heart rate problems, sexual dysfunction

• not always mutually exclusive or in opposition to one another (like sexual activity)

• effects aren’t always generalized across body

cell clusters

• CNS: grey matter region - nuclei (different from cell nucleus)

• PNS: ganglia

bundle of axons

white matter

• CNS: tracts

• PNS: nerves

• Both: fibres

anterior

in front of, toward the face

posterior

behind, toward the back

superior

above, toward the head

inferior

below, toward the feet

medial

toward the middle

lateral

toward the edge

dorsal

toward the top of the brain/back of the spinal cord

ventral

toward the bottom of the brain/front of the spinal cord

anterior vs. posterior in animals

2-legged: posterior is feet, move vertically to anterior frontal lobe

4-legged: posterior is tail, move laterally to nose

brain sections/cuts

• coronal (frontal) section

• horizontal section

• mid-sagittal (medial) section

line of symmetry

down the middle of humans (medial to lateral)

• indicate direction from patient/participant’s point of view

intermittent projections from spinal cord

protected by bone, so axons can only go through this area

cervical nerves

1. cervical

2. thoracic

3. lumbar

4. sacral

5. coccygeal

• narrow as the move down the spinal cord because axons travel up spinal cord, so there are barely any axons at the end

• grey/white matter divisions

• dorsal/ventral side organization

• spinal cord damage to a spot will also affect everything below it

development of human brain

starts as a neural tube - 3 swellings (forebrain, midbrain, hindbrain)

1. forebrain

largest part of the brain, responsible for higher cognitive functions.

includes structures

• cerebrum: sensory processing, reasoning

• Thalamus: sensory information

• Hypothalamus: homeostasis, temperature, hunger, and thirst

• Limbic System: emotions and memory

• disproportionally large

• damage considers so much of the brain so anything from issues with decision making or spatial awareness or vision problems to sensory issues to hunger control to motor issues to memory to processing emotion problems

cerebrum

largest/most developed part of the brain (85% of brain’s total weight) - functions include cognition, sensory perception, voluntary motor actions, higher order thinking

• left and right hemisphere

• cerebral cortex

• white matter

• lobes (frontal, parietal, temporal, occipital)

• basal ganglia

• limbic system

2. midbrain

vital for

• Vision and Hearing: superior and inferior colliculi

• Motor Control: regulates movement

• Arousal and Alertness: sleep-wake cycle and attention - processing sensory information and coordinating responses

• tegmentum

• tectum

3. hindbrain

located at the lower back of the skull, consists of three main structures:

• Medulla Oblongata

• Pons

• Cerebellum

medulla oblongata

autonomic functions like breathing and heart rate

pons

connects brain parts, regulates sleep and arousal, holds a lot of myelin (sensory and motor loss when damaged)

cerebellum

coordination, balance, correcting what you did with what you meant to do - essential for vital bodily functions and motor control.

1. myelencephalon

most posterior region of the brain - medulla oblongata

• adjacent to spinal cord

• lots of tracts (afferent signals going in, efferent going out)

• damage here is often fatal

reticular formation

brain stem - runs from myelencephalon to mesencephalon

• critical for arousal, wakefulness, attention, sleep

• damage to this region can be critical/fatal

2. metencephalon

• ventral side: pons - lots of tracts, strokes can cause sensory/motor impairments, difficulties with wakefulness

• dorsal side: cerebellum - critical for motor coordination, but being born without is manageable (damaging it later on is difficult)

  • alcohol affects cerebellum and balance when drunk

3. mesencephalon

midbrain - roof (tectum, dorsal side), floor (tegmentum, ventral side)

• damage = vision/hearing problems, ataxia, lack of pain inhibition, tremors, motor deficits

tegmentum

reticular formation, fibres, periacqueductal grey (amygdala connection) (dopamine producing regions, linked to movement, motivation; red nucleus)

tectum

colliculi (vision with respect to eye movement, audition with respect to orientation)

4. diencephalon

thalamus and hypothalamus

thalamus

“relay” centre for sensory information, receives almost as much from cortex as it sends to cortex

• another site of modification, reverberate connection

• damage = sleep disorders, sensory problems

hypothalamus

interacts with with endocrine system via pituitary gland to influence hormonal release - affects sex, aggression, feeding, sleep, wake

• damage = uncontrollable behaviours like eating compulsively or halting these behaviours, narcolepsy, sex aggression

5. telencephalon

largest and most sophisticated division of brain - cortex and underlying structures

• cerebral cortex

• convolutions

• cerebrum hemispheres

• commissures

• limbic system

• basal ganglia

cerebral cortex

outermost layer of brain - sulci grooves and raised gyri

• layered

• convolutions (continuous)

commissures

connect the two hemispheres

• largest = corpus callosum