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Brain Bee by Mr. Shen Zhou > 1. Brain Basics > Flashcards

1. Brain Basics Flashcards

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1
Q

Two functions of spinal cord

A

Reflexes and highway between brain and body

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2
Q

What distinguishes the human nervous system from others?

A

Large size of brain relative to body

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3
Q

3 types of neurons

A

Sensory, motor, interneurons

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4
Q

Sensory neurons

A

Coupled to receptors specialized to detect attributes of the environment. When stimuli to the skin exceed a certain intensity, they can cause tissue damage and nociceptors are activated, giving rise to protective reflexes and the sensation of pain

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5
Q

Motor neurons

A

Control muscle activity, responsible for all forms of behaviour.

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6
Q

Interneurons

A

Interposed between sensory and motor neurons. Most numerous in the brain. Mediate simple reflexes and are responsible for the highest functions of the brain

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7
Q

Cell body

A

Also called the soma. Contains the nucleus, most of its cytoplasm, and molecular machinery for building and transporting proteins

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8
Q

Dendritic spines

A

Tiny protuberances that stick out from dendrites, where incoming axons make their connections

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9
Q

Growth factors

A

Factors taken in by axons and transported to cell body where they influence expression of neuronal genes and manufacture of new proteins. Enable neuron to grow.

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10
Q

Glial cells

A

Previously thought to have a purely supporting function, now known to contribute to the development of the nervous system. Much more numerous than neurons, but don’t transmit information in the way neurons do. Previously thought to outnumber neurons 10:1, but recent research suggests that in some regions the ratio is closer to 1:1.

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11
Q

Four types of glial cells

A

Astrocytes: regulate ion concentrations around neurons, provide them with nutrients, regulate formation of new connections between neurons

Microglia: immune cells of brain, function as phagocytes and regulate formation of new neuronal connections

Ependymal cells: make cerebrospinal fluid (cushions brain)

Oligodendrocytes: wrap axons in myelin sheaths

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12
Q

Resting potential in mammals

A

-70 millivolts, more negative inside cell

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13
Q

Depolarized

A

Making a cell less negative

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14
Q

Hyperpolarized

A

Making a cell more negative

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15
Q

Action potential

A

If the sum of the signals at dendrites reaches the threshold, a series of ion channels (sodium and potassium) opens, triggering an action potential. Starts at the cell body, sodium channels open first and a new equilibrium is established within a millisecond. Membrane potential increases by about 100 mV, which opens potassium channels causing the membrane potential to change back to its original negative value
Over very quickly, can race along at 100 metres per second. Followed by a brief refractory period

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16
Q

Time elapsed between arrival of action potential at synapse and generation of new signal at next neuron

A

1/1000 of a second

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17
Q

Mechanism by which an action potential is propelled

A

Wave of depolarization

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18
Q

Old experiments regarding neurons were conducted with…?

A

Large neurons from sea creatures

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19
Q

Modern day technique for study of the movement of ions in neurons

A

Patch-clamping

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20
Q

Gaps in myelin sheath

A

Where ion channels are concentrated, function as amplifiers

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21
Q

Cerebrum

A

Largest part of the brain. Divided into two hemispheres, left and right, which are connected by bundles of nerve fibres.

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22
Q

Corpus callosum

A

Largest of nerve bundles bridging cerebral hemispheres

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23
Q

Cerebral cortex

A

Surface of the cerebrum. Deeply folded to increase the area, creating more space for neurons.

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24
Q

Frontal lobe

A

Front of brain. Coordinates voluntary movements, speech, memory, emotion, higher cognitive skills, and personality

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25
Q

Parietal lobe

A

Top of brain. Integrates sensory signals from skin, processes taste and some types of visual information

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26
Q

Occipital lobe

A

Back of brain. Processes visual information, responsible for recognition of colours/shapes and integrating them into complex visual understanding

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27
Q

Temporal lobe

A

Sides of brain (bottom). Some visual processing and interprets auditory information

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28
Q

Hippocampus

A

In the temporal lobe. Curved structures lying beneath cerebral cortex. Encodes new memories

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29
Q

Amygdala

A

Deep structure within temporal lobe. Integrates memory and emotion

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30
Q

Thalamus

A

Integrates sensory information and relays it to other parts of the brain (cerebral cortex) which sends messages back to the thalamus

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31
Q

Hypothalamus

A

Sends hormonal signals to rest of body through pituitary gland. Controls functions such as eating and drinking. Regulates hormones involved in sexual functions

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32
Q

Limbic system

A

Group of structures deep within brain that helps regulate emotion and motivation. Includes hippocampus, amygdala, thalamus, hypothalamus

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33
Q

Diencephalon

A

Divided into two areas: thalamus and hypothalamus.

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34
Q

Forebrain

A

Cerebral cortex and limbic system

35
Q

Midbrain

A

Beneath thalamus. Includes groups of neurons that coordinate eye movements and trigger reflexes to sounds. Other regions inhibit unwanted body movements and help coordinate sensory input and motor output to manage fine motor control. Each group of neurons seems to predominantly use a particular type of chemical messenger, but all of them project up to cerebral hemispheres. Thought that these can modulate the activity of neurons in higher centres of brain to mediate functions like sleep, attention, or reward.

36
Q

Basal ganglia

A

Parts of the midbrain and forebrain which form a collection of structures that helps regulate complex body movements (initiation and control of movement).

37
Q

Hindbrain

A

Glucose regulation, sleep, movement control, control of vital functions. Extension of the spinal cord.

38
Q

Cerebellum

A

Underneath occipital lobe at back of brain, arises from roof of hindbrain. Second largest part of brain in volume, contains over half the brain’s neurons. Deeply folded, divided into two hemispheres. Coordinates voluntary movements (control and timing of movements), helps brain learn new motor skills, spatial and temporal perception. Patient with cerebellar damage might have a jerky gait or be unable to accurately touch his nose.

39
Q

Pons

A

Below cerebellum. Influences breathing and posture

40
Q

Medulla

A

Part of hindbrain. Carries nerve pathways connecting brain to spinal cord, helps control basic functions (swallowing, heart rate, breathing)

41
Q

Brainstem

A

Midbrain, pons, medulla. Divided into hindbrain, midbrain, and diencephalon (between brain)

42
Q

Synaptic cleft

A

Space between a dendrite and an axon at a synapse. 20 nanometres. Only verified by electron microscopy in 1950s.

43
Q

When an action potential arrives at the axon terminal, the voltage change triggers…

A

The voltage change triggers ion channels to open, allowing calcium ions to flow into the cell and bind to synaptic vesicles, causing them to fuse with the membrane at the axon terminal and empty their contents into the synaptic cleft (done by activating enzymes that act on proteins called “snare”, “tagmin”, and “brevin”). Afterwards, pieces of the membrane cycle back into the soma as new vesicles re-filled with neurotransmitters

44
Q

Substances that act as neurotransmitters

A

Amino acids, gases, small organic chemicals, short peptides

45
Q

Production of neurotransmitters

A

Small non-peptides (dopamine, acetylcholine) can be made in the axon terminal. Proteins are built in the soma

46
Q

Vesicles come from ______, binding to proteins called _______ that travel down the _____ along _______

A

Golgi apparatus, kinesins, axon, microtubules

47
Q

Acetylcholine

A

Neurotransmitter, acts on both ionotropic and metabotropic receptors. First neurotransmitter to be discovered. Uses ionic mechanisms to signal across neuromuscular junctions. Can also function as a neuromodulator when you want to focus on something

48
Q

Dopamine

A

Neuromodulatory. Reward system.

49
Q

Noradrenaline

A

Released in response to forms of stress, organizes responses to these stresses. Neuromodulatory. Only 1600 noradrenaline neurons in brain, but they reach everywhere. Located in locus coeruleus. Axons distributed throughout midbrain: hypothalamus, cerebellum, cerebral cortex

50
Q

Outer surface of dendrite with high concentration of receptors

A

Postsynaptic density/membrane

51
Q

Two types of receptors

A

Ionotropic and metabotropic

52
Q

Ionotropic receptors

A

Neurotransmitter binds directly to part of an ion channel. Receptor changes shape of channel, widening the tunnel

53
Q

Metabotropic receptors

A

Receptor and channel are different proteins linked by a series of biochemical steps that are triggered by the attachment of a neurotransmitter. May open a channel some distance away or activate other intracellular molecules. Slower and more long-lasting. Neuromodulation.

54
Q

Mechanism by which neurotransmitters attach to receptors

A

Lock and key

55
Q

Process by which neurotransmitters are broken down or reabsorbed

A

Reuptake

56
Q

Excitatory neurons

A

Make neurotransmitters that open ion channels to depolarize membrane. 80% of neurons in brain are excitatory. Send signals that push other neurons to fire. Typically pass signals forward through a circuit and eventually send outputs to rest of brain.

57
Q

Inhibitory neurons

A

Make neurotransmitters that hyperpolarize membrane. Suppress activity of other neurons. Regulate circuit activity. Typically local and loop responses back to earlier sections of a circuit.

58
Q

Most common excitatory neurotransmitter

A

Glutamate. Amino acid, used by half of excitatory synapses in brain. can bind to several ionotropic receptors, including AMPA and NMDA receptors. AMPA is quicker, NMDA slower. Important in learning and memory

59
Q

Most common inhibitory neurotransmitter

A

GABA: binds to both types of receptors. Ionotropic: lets chloride ions into cell. Metabotropic: lets potassium ions out. In both cases, makes potential more negative

60
Q

Hormones

A

Send brain cues about condition of distant tissues in body

61
Q

Neuromodulators

A

Endocannabinoids that suppress neurotransmitter release

62
Q

Prostaglandins

A

Small lipids that change brain’s response to pain and inflammation (increase pain sensitivity)

63
Q

If a receptor is on the surface of the cell…

A

Molecule changes receptor’s shape and starts chain of intracellular reactions, ultimately modifying neuronal function by shifting ion balance or enzyme activity

64
Q

If molecule can diffuse through membrane…

A

Receptor may be inside soma. When bound, complex can transform into a transcription factor that enters nucleus, binding to genes and altering their activity. E.g., steroid hormones

65
Q

Gene expression depends on…

A

Chemical changes to chromatin

66
Q

Tay-Sachs disease

A

Fatal degenerative neurological condition caused by mutations in a gene that codes for the fat-metabolizing enzyme beta-hexosaminidase A. Fats build up in neurons and become toxic

67
Q

In early vertebrates, the brain end of the nerve cord developed into ___ bulges. These bulges became…

A

3 bulges: forebrain, midbrain, hindbrain

68
Q

Forebrain (brain evolution)

A

Able to detect chemicals. Expanded to form olfactory bulbs. With the evolution of image-producing eyes, light-sensing regions expanded and processed more complex visual signals

69
Q

Cerebellum (brain evolution)

A

Cerebellum appeared as the hindbrain and expanded regions that control escape movements and orient the body

70
Q

Nerve tracts

A

Distinct bundles of nerve fibers of region-spanning neurons. E.g., corpus callosum, smaller anterior commissure transmitting signals between left and right temporal lobes

71
Q

Neural networks

A

Group of nerve tracts connecting a series of regions in the brain

72
Q

Describe the neural network involved in watching a movie

A

Photoreceptors trigger electrical signals in response to specific wavelengths of light → signals reach optic nerve → travel through optic tract to thalamus → passes signals to primary visual cortex in occipital lobe → integrates these signals to create a 3D representation of the world → image refined as signals are sent down two parallel streams → one to temporal lobe (identifies objects) and one to parietal lobe (detects spatial location)

73
Q

Thalamocortical loop

A

Visual cortex sends signals to thalamus to be integrated with other sensory information

74
Q

EEG

A

Electroencephalograph, detects brain waves: signals that travel through loops, producing oscillating electrical patterns

75
Q

Four types of brain waves

A

Alpha waves: originate in parietal and occipital lobes when brain is relaxed and eyes are closed. Between 8 and 13 Hz. Produced by awake brain.

Beta waves: produced by frontal and parietal lobes when processing sensory input or concentrating on a task. 14 to 30 Hz. Produced by awake brain.

Theta waves: 4 to 7 Hz. Produced during sleep.

Delta waves: less than 3.5 Hz. Occur during deep sleep.

Alpha and delta waves have higher amplitudes (are stronger) but all four signals are in the microvolt range (20-200 microvolts for alpha and delta, 5-10 microvolts for beta and theta)

76
Q

Spinal tracts

A

Another example of a neural network. Chains of neurons that pass signals through brainstem and spinal cord. Signals either travel upward from sensory receptors to thalamus and parts of cortex, or travel downward from brain regions that induce movement through medulla and spinal cord to muscles

77
Q

5 other neural networks

A

Basal ganglia part of a feedback loop that takes information from cortical areas that elicit movement and makes signals that feed back to cortex to excite/inhibit movements

Loops connecting brainstem and cerebellum influence timing and strength of motor signals

Networks looping hippocampus into sensory cortex pathways help brain analyze whether environmental signals are familiar or new

Networks linking hippocampus to thalamus and hypothalamus allow memory to influence conscious behaviour and unconscious physiological responses

Reflex loops elicit action before thoughts. Usually controlled locally by information going in/out of spinal cord or subcortical regions of brain, never reach cortex

78
Q

Arrangement of neurons in neural circuits

A

Neurons organized into a stack of distinct layers that span the thickness of the cortex. Circuits arranged in columns as each neuron forms connections with cells in layers above and below. Neurons in a column form a single chain, signals travel down that chain. Each time the signal moves forward, it is modified in some way, building outputs that encode complex information.

79
Q

Most common type of excitatory neuron

A

Pyramidal cell: cone-shaped cell body, two sets of dendrites - one at apex, another set of shorter ones at base. Multi-branched axon that sends a single signal to multiple destinations.

80
Q

__________ may be caused by imbalances in activity of excitatory and inhibitory neurons

A

Seizure disorders

81
Q

Feed-forward inhibitory circuit

A

Inhibitory interneurons connect neighbouring circuits in a way that excitatory signals in one column simultaneously send inhibitory signals to adjacent columns, reducing their activity

82
Q

Feedback inhibition

A

Neurons send signals to downstream excitatory neighbours and to interneurons that reach back and inhibit preceding layers of the same circuit.

83
Q

Recurrent neural networks

A

Neurons inside interconnected circuits send feedback signals to one another. Examples: feed-forward inhibitory circuit, feedback inhibition

Brain Bee by Mr. Shen Zhou (14 decks)

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