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PSYC 207: Drugs, Brain, Society > Lecture 3: Brain Basics > Flashcards

Lecture 3: Brain Basics Flashcards

1
Q

Human brain facts

A
  • 2 - 3% of body weight, around 3lbs (probably less on average)
  • Consumes roughly 20% of your energy
  • Slightly larger in men than in women (size does not correlate to intelligence)
  • Huge individual variation
  • Composed of neurons, glia (support/structure), stem cells (proliferate into different cell types), blood vessels
  • More than 10 billion, less than 100 billion neurons (hard to say), more of half (70%) of which are in the cerebellum - only 10% of the brains volume
  • Consistency of soft tofu
  • Convoluted (wrinkled): increasing the amount of cortex, that can fit inside our skull - flattened, cortex is much bigger than the other brain regions
  • Cells are not replaced: neurons you have at 1 years old, you will have the same amount for the rest of your live - neurogenesis does not count for much
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2
Q

It’s not the size that counts

A
  • Bigger animals have bigger brains
  • Above the line of best fit, disproportionately large brain compared to the size of the body - humans, the most
  • Below the line of best fit, disproportionately small brain compared to body size
  • Still doesn’t give us a mechanism, though - the link
Chimpanzee	450
Human	1,350
Bottlenose Dolphin 	1,600
African Elephant	6,075
Fin Whale	7,200
Sperm Whale	9,200
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3
Q

Brain cell density

A
  • Intelligence also correlates with sophistication of cellular connections (i.e. wiring)
  • African Bush Elephant’s brain is much larger, double the size - although a Human’s brain has almost 3 times the neurons
  • More neurons means more intelligence - seem to be a predictor - disproportionately dense brain (humans the most dense)

Human African Bush Elephant
Primate Non-primate
1232 g 2,848 g
16.3 billion neurons 5.5 billion neurons

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4
Q

Two basic cell types

A

Neuron

Glia

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5
Q

Neuron

A

o Type of cell in our nervous system

o Main communicating cells

o Release chemical messengers; chemicals received by other neurons

o Able to communicate really really quickly

o Axon/axon terminals - carries axon potential

o Communicate with things really far away, goes to a specific location - very targeted, very fast (whale, giraffe)

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6
Q

Glia

A

o (Long undervalued within neuroscience)

o Latin word for glue

o Structural support role - especially in development

o Variety of active roles - the way in which brains communicate

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7
Q

The neuron

A

• Many types, but similar design

• Dendrite - soma - axon - terminals
o Dendrite: « input layer » information comes from other cells, converge onto a cell body (soma)
o Soma: from the soma, emerges a single axon
o Axon: input travels down the axon
- Terminals: input/neurotransmitters

1 - pyramidal
2 - stellate
3 - purkinje

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8
Q

Pyramidal

A

o Common in cerebral cortex
o Dendrites reaching to different layers
 Apical dendrites
 Basal dendrites

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9
Q

Stellate

A

o Common in subcortical regions

o Mess, different branches converges on the cell body

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10
Q

Purkinje

A

o Common in cerebellum
o Dense with dendrites - tens and tens and tens of thousands
o Only ever one axon coming out of the cell (axon can branch - axon collateral )

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11
Q

Two basic types of neurons

A

Projection neurons

Interneurons

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12
Q

Projection neurons

A

o Interesting shapes (often)

o Axon is long, projects to different parts of the brain (far away)

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13
Q

Interneurons

A

o Typically star shapes

o Short axons, project locally

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14
Q

Neuron (more info)

A
  • Big long wire, with some interruptions
  • No reason why the axon has to stop - can be very very long
  • Synapse - is not a physical limitation - every synapse, provides an opportunity to modify the signal
  • Surrounding these 2 projection neurons, there are these interneurons - receiving inputs by other interneurons/projection neurons - using that information to modify/modulate the signal
  • Interneurons: synchronizing and timing (motor task, moving together in an intelligent way); suppressing (sleeping; blocking sensory information from coming into your brain)
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15
Q

Glial cells

A
  • Support cells
  • Variety of interesting goals
  • Majority = macroglia (larger)
  • Microglia
  • Schwann cell
  • oligodendrocyte
  • astrocytes
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16
Q

Microglia

A

o Small

o Act as the “immune system” in the brain - walled off, carefully guarded from bacteria/viruses in blood (devastating effects on the brain)

o Detecting; sense debris/cells damages/protein related to bacteria - primed state/become active, searching for bacteria - if found, enlarged to an enormous size, engulf the foreign body & digest it

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17
Q

Myelinated glia

A

• (Schwann cell & oligodendrocyte)

o Wrap around the axon, creating an insulated sheathe

o Fatty substance

o Myelinate the axon - signal travels much faster

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18
Q

Schwann cell

A

o Found in the peripheral nervous system (outside the brain/spinal cord)
o Myelinate only a single axon* wraps its whole body around

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19
Q

Oligodendrocyte

A

o Found in the central nervous system (brain/spinal cord)
o Oligo-: “several or a few”
o Myelinate several different axons

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20
Q

Astrocytes

A

o Blood brain barrier: wrapping around our capillaries

o Provides nutrition to neurons (oxygen/glucose) mediated by astrocytes
 From the blood, to the astrocytes, down to the neuron

o Wrapped around neuron and often the synapse - control over that environment - help to maintain the environment around the area
 Too much potassium - buffer away; too little potassium - bring some extra in)

o Release their own chemicals

o Gliosis: need scarring in the brain, astrocytes do this through gliosis

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21
Q

Ripped from the headlines

A
  • Glia play a key role in brain function, and we will hardly talk about them throughout this course
  • Not just support cells
  • “Key role in regulating motivation for drug and heroin addictions”
  • “Glial cells are critical players in brain’s response to social stress”
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22
Q

The tripartite system

A
  • A conversation of 3
  • Glia have receptors, transmitters
  • Glia shape conditions at the synapse
  • Axon terminal = pre-synaptic
  • Dendrites = post synaptic

• Astrocyte:
o Can release their own transmitters (glio-transmitters); bind to either the pre-synaptic axon or post-synaptic dendrite
o Receive signals: have receptors; can change processes (ex. Bringing in more glucose/oxygen)

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23
Q

Grey matter

A

o Where you find the cell bodies of neurons

o Where you find unmyelinated axons

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24
Q

White matter

A

o Where you find myelinated axons

o Connecting two areas of grey matter

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25
Q

Staining reveals matter

A
  • Take a piece of tissue, expose to some sort of dye, dye taken up by some sort of cell - reveal those specific receptors/systems
  • Nissl-stained: where our cell bodies are
  • Fibre stain: dye taken up my white matter, myelinated glia
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26
Q

Anatomical dimensions

A
  • dorsal
  • ventral
  • anterior
  • posterior
  • medial/left lateral/right lateral
  • coronal section
  • sagittal section
  • horizontal section
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27
Q

Dorsal

A

• superior, top of the brain

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28
Q

Ventral

A

• inferior, bottom on the brain

29
Q

Anterior

A

• front of the brain

30
Q

Posterior

A

Back of the brain

31
Q

Medial/left lateral/right lateral

A

Middle of the brain

32
Q

Coronal section

A

Vertical cut from the left lateral to the right

“Crown”

33
Q

Sagittal section

A

Vertical cut from anterior to posterior

34
Q

Horizontal section

A

Horizontal cut from left lateral to right lateral

35
Q

The nervous system

A
  • efferent nerves
  • afferent nerves
  • somatic nervous system
  • autonomic nervous system
36
Q

Afferent nerves

A

Moving from the body, to the brain

Most likely sensory info

37
Q

Efferent nerves

A

Moving from the brain, to the body

Motor signals

38
Q

Somatic nervous system

A

• voluntary movements, interested in the outside world - conscious access

o Afferent: when you touch something with your hand, signal traveling from hand to the brain

o Efferent: when you want to move your hand to touch something, signal traveling from the brain to the hand

39
Q

Autonomic nervous system

A

o Afferent: sensory information coming from our guts, to the brain

o Efferent: from the brain, to the body (internal environment)
 Sympathetic:
 Parasympathetic

40
Q

Sympathetic nervous system

A

 Sympathetic:
 “Fight or flight”
 Active during first dates - not just danger and violent
 Mobilize your resource to deal with high intensity situations / stressors
 Digestions slows; heart rate increases; pupils dilate; constricts blood vessels

41
Q

Parasympathetic nervous system

A

 Rest and digest”
 Low arousal; low stress
 Heart rate slows down; stimulates digestive system; constricts pupil

42
Q

ANS efferent

A
  • Sympathetic: mobilize energy
  • Parasympathetic: conserve energy

• Not always mutually exclusive/in opposition to one another
o Some situations, need contributions from both systems
o Healthy human sexual functioning: sympathetic and parasympathetic nervous system activation
 Excited, but relaxed at the same time

• Drugs often act on these
o Sympathetic nervous system: stimulants
 Raise heart rate; increasing function / mimicking of the sympathetic nervous system

43
Q

Major divisions of the brain

A
  • We have disproportionately large forebrains as compared to, say, fish (all roughly the same size)
  • Humans forebrains, very large (cortex is huge); midbrain about the same size as a fish’s midbrain; hindbrain at the back, includes cerebellum and more primitive brain structures (medulla)
  • When drugs are dangerous, potentially lethal: affects are in the hindbrain, not the forebrain
44
Q

Convolutions

A
  • Cortex is wrinkled: convolution
  • Gyrus/gyri (outward fold) and sulcus/sulci (inward fold)
  • Sulci sometimes called fissures - really deep, or meaningful
  • Not functionally meaningful, per se - labelling, mostly done by identifying gyrus
45
Q

Lobes of the brain

A
  • Cerebral cortex
  • Lobes are a human distinction, based on the bones of the skull
  • Frontal lobe
  • Parietal
  • Temporal
  • Occipital
  • Cerebellum (“little brain”)
46
Q

Clusters and bundles

A
  • Under the cortex are grey matter clusters called nuclei (more forebrain)
  • Grey matter: terminals, cell bodies (unmyelinated)
  • Nuclei pays important roll in discussion drugs & the brain; addiction

• Basal ganglia (addiction)
o Caudate nucleus & putamen: together = corpus striatum

47
Q

Important brain structures

A
  • medulla
  • hypothalamus
  • limbic system
  • nucleus accumbens
48
Q

Medulla

A

o Part of the hindbrain (where spinal cord become the brain)

o If a drug is potential lethal (overdose), its because it has effect on the medulla

o Looks like spinal cord, almost (thicker)

o Most basic biological functions: keeping the heart beating, moving the diaphragm to breathe

o Breaks down/disfunction: affects heart and lungs - dangerously lethal

49
Q

Hypothalamus

A

o Forebrain; older part of the forebrain

o Sex; salt regulation; sleeping

o Main interface/interaction area between the nervous system and endocrine system (hormones)
 Example of affecting the endocrine system, alcohol (increases sexual urges)

50
Q

Limbic system

A

o Limbic: on the border of the brains stem & the cortex
o Include: basal ganglia regions
o Often referring to: hippocampus, amygdala - very complex term
o Many subcortical structures

51
Q

Nucleus accumbens

A

o Part of the striatum, basal ganglia

o Seems to play a critical role in the development of addiction

52
Q

Do We Only Use 5%/10%/etc of Our Brains?

A

• No. All of our brain is doing tremendous work, all of the time - even taking notes!
o E.g. Controlling voluntary movement (reaching out and having a drink of water)

53
Q

o E.g. Controlling voluntary movement (reaching out and having a drink of water)

A

 Prefrontal cortex:
- Decide I am thirsty, recognize my need & identify the goals to satisfy that need

 Premotor areas:
-Turn that goal into a specific action, motor patterns

 Motor cortex:
-Directly map those signals onto the body - hand

 Basal ganglia:
-Subcortical nuclei, important for habit
-Not to lift the glass too fast; how much force to apply for a heavy glass vs a light glass

 Pons:
-Information travelling out of the motor cortex, travel to the pons
-Where the axons travel through

 Cerebellum
-Variety of sensory information; hands, stretch receptors in muscles in arms and eyes
-Constant course correction - stabilization

 More

54
Q

Learning and memory

A
  • Number of drugs affect our memory, mostly for the worst (alcohol), some help better retain information [modest effect]
  • Short-term (working) memory

• Long term (semantic) memory
o Hippocampus, key role in transition memory from short-term to long term
o Hippocampus damaged, short-term memory will not convert to long term

  • But, the story is much more complicated
  • Important to consider because of the many drugs effects
55
Q

Cerebral blood flow

A

• Drugs flow through the blood to the brain - very rarely are drugs directly injected in to the brain

• Limited supply/limited access to the brain
o 2 arteries on the front: left & right internal carotid
o 2 arteries on the back: vertebral
o Gets all of its blood from these 2 sets of arteries

• No redundancy
o If one artery is damaged, there are no other arteries that also go to the brain to make up for the loss
o Why stroke is so devastating

• No reserves
o If you have a problem with blood flow to the brain - overdose, having respiratory problems or failure - brain tissue will start dying right away (within 3-4 minutes) from disruption with blood flow

56
Q

Blood brain barrier

A
  • Brain walled off from the rest of the body
  • Protection from viruses/bacteria (even relatively benign bacteria can be fatal in the brain)

• Tightly packed:
o Cells smushed, no space between them “tight junctions” - no pores
o Astrocytes wrapped all around the blood vessels to “double-up” - very effective of keeping most things out… Can be a problem, some of the drugs (that we want) cannot cross the blood brain barrier (require active transport/pump)
o Some molecular shapes better at crossing the barrier
o Rest of the body, capillaries quite porous: have holes, water-line pores where things can move in and out

• Active transport for large molecules

• Drugs that cross the BBB better, work better - big predictor in how effective a drug will be
o Different opioids, all relatively the same shape - slight changes… do not change how they interact with the receptors, only change how effective they are at crossing the BBB

57
Q

Skull and meninges

A
  • Primarily protection for the brain
  • Skull

• Meninges: 3 “layers”
I. Dura mater: outermost layer, thickest, “like a pillow-case”
II. Arachnoid mater/membrane: tough to find, spider-web like texture
III. Pia mater: thinnest, pale colour, clinging to the brain

58
Q

Ventricles and cerebrospinal fluid (CSF)

A
  • Between the arachnoid & pia mater: contains fluid
  • Brain produces this CSF to support, protection*, nutrition
  • Like an “air-bag” - brain is soft, skull is very hard (banging your head, is like throwing jello at a wall) - fluid slows down momentum, causes the impact to be reduced
59
Q

The central dogma of molecular biology

A
  • DNA - mRNA - protein
  • Transcription from DNA to mRNA, and translation from mRNA to protein
  • Proteins: stuff in membrane, signalling molecules - you are your proteins
  • Might have an enzyme gene that breaks down a drug very efficiently - receive less of the drugs effects… or an enzyme gene that breaks down a drug much less efficiently - receive the effects longer in the system, stronger effects
60
Q

Genes

A

• Cell nucleus contains 46 chromosomes

• Chromosomes are made of DNA
o Genes: DNA
o Can have slight differences: polymorphisms/single nucleotide polymorphism (very small difference between the genes)

61
Q

Polymorphism

A

o lead to differences in the protein & how they function

62
Q

Transcription

A

o how genes transcribe into mRNA, then the mRNA translates to proteins

 Some drugs increase or decrease transcription/translation

63
Q

Epigenetics

A

o things that get passed on, from one generation to the next, but they are not carried in your genes

 If genes are wrapped lose - easy to transcribe them

 If genes are wrapped very tight - difficult to transcribe

 Effecting the amount of protein

 Can be affected by the environment: living in chronic stress, living during a famine - changes the epigenetics/how tightly or loosely genes are wrapped up & this can be passed along to your children

 Field/influence pretty limited

 Previous school of thought: I can only pass along my genes, only DNA

64
Q

Neurogenetics

A

 Studying genes related to nervous system development and nervous system function

65
Q

Genetically modified organisms

A
  • transgenic animals
  • knockout animals
  • conditional knockout mice
66
Q

Transgenic animals

A

o Animals that has genetic content, not naturally found in the species

o Add a gene from another organism (produce, reduce the amount of damage to the produce when there is flash freeze, less susceptible to quick changes in temperature - or how quickly the apples brown)

o Insert some genes to over-express something

67
Q

Knockout animals

A

o More commonly, when looking at drugs/neuro-transmitting systems, removing a gene, thus removing that protein from the animal

o Standard: remove a specific gene
 Ex. Dopamine receptor
 Problem: we need these proteins to be viable/survive, effects are lethal, in development - the animal is going to develop in a really weird way (is it due to missing that gene or is it a mental abnormality?)

68
Q

Conditional knockout mice

A

o Animals will be raised to look normal at first - develop normally

o Little “time-bomb” in their genome - can be turned off or on, based on a chemical you put into their diet

o One day, start feeding diet with a special molecule - interacts and suddenly will turn off the expression of that gene - that protein will no longer be produced

o Study the effects of not having that protein

o You can compare the exact same animal with the gene knocked out and with an animal who produces that gene normally

o Can be useful, studying the dopamine system or the serotonin system

PSYC 207: Drugs, Brain, Society (8 decks)

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