Neuroscience Sem 1 Flashcards
1
Q
Explain how information is moved from one neuron to another
A
- Information is picked up by receptors on dendrites which pick up signals (neurotransmitters)
- Information interpreted in the Soma (cell body), which contains nucleus (DNA/genetic material of the cell)
- Soma moves information from dendrites to Axon Hillock
- If signal is strong enough, it’s sent to Axon (it is now an Action Potential)
- Axon covered in Myelin (helps stop signal from degrading)
- Signal moves down Axon to Axon Terminal/Synaptic Buttons, which can cause release of Neurotransmitters
2
Q
What are two forces determining the distribution of charged ions?
A
- Diffusion
- Force driving molecules to move from higher concentration to lower concentration - Electrostatic pressure (opposites attract)
- Ions, like magnets, move according to charge.
Like ions repel, unlike ions attract
3
Q
What are the two types of receptors inside the cell membrane?
A
- Ionotropic receptors
- Fast acting
- Open/close ion channels
- Modify permeability of membrane for an ion
- Induce immediate change of membrane potential - Metabotrophic receptors
- Slower, more prolonged action
- Wide variety of effects
- More prevalent
4
Q
What are the two types of postsynaptic potentials
A
Excitatory Postsynaptic Potential (EPSP)
- Depolarization occurs and response is stimulatory
- Depolarization might reach threshold producing an Action Potential
- Common transmitter is Glutamate
Inhibitory Postsynaptic Potential (IPSP)
- Hyperpolarization and the response is inhibitory
- Decrease Action Potentials by moving membrane potential farther from threshold
- Main neurotransmitter is GABA
5
Q
What are the two ways that neurons integrate information from other neurons
A
EPSP or IPSP can be summed either in space or time
Spatial summation
- Sums EPSP in space. Occurs when several excitatory postsynaptic potentials arrive at Axon Hillock simulatneously
Temporal summation
- Sums up IPSP in time. Postsynaptic potentials created in the same synapse in rapid potential can be summed
6
Q
What is an Action Potential and what are three key features that must occur
A
Action Potential = sudden and large positive membrane potential change when neurons fire
Threshold: To generate an AP, an axon requires a stimulus of a certain minimum strength
All or none: Each AP has the same amplitude (-70mV)
Refractory Period: A second AP cannot occur during this period
7
Q
How is an Action Potential induced (4 steps)
A
Resting state: Ionotropic receptors opening, letting Na+ and Cl+ in, raising the Action Potential to the threshold
- Depolarizing phase: As ion becomes more positive, more channels are opened, letting more Na+ ions in
- Repolarizing phase: As it reaches its peak, K+ channels open, letting K+ ions out
- Undershoot: Na+ channels close, K+ channels still open, which gives the undershoot, causing the refractory period from the positive change
DOUBLE CHECK THIS
8
Q
What is Saltatory conduction
A
(to hop, or leap)
Propagation of action potentials along myelinated Axons between nodes of Ranvier, increasing conduction velocity of Action Potentials
9
Q
What is synaptic transmission
A
Means of communicating between neurons.
Neurotransmitters released from pre-synaptic terminal, across the synapse, binding to receptors in the cell body + dendrites
10
Q
What are some Common Neurotransmitters
A
Fast neurotransmitters (short lasting effects
- Acetylcholine (Ach)
- Glutamate (GLU)
- Gamma-aminobutyric acid (GABA)
Neuromodulators (longer lasting effects)
- Dopamine (DA)
- Noradrenaline (NA)
- Serotonin (5-HT)
11
Q
Explain what X-Ray techniques can be used for
A
Brain doesn’t have much variability in its structures, so normal X-rays are not very useful except to confirm foreign objects
Contrast X-Ray
Inject a substance known as contrast agent, provides contrast between blood vessels + everything else in the brain
12
Q
Explain Magnetic Resonance Imaging (MRI) and functional Magnetic Resonance Imaging (fMRI)
A
MRI
- Uses magnetism to ‘see’ position of hydrogen atoms in water molecules, building up detailed, high spatial resolution image of the brain structure
fMRI
- Principle is the same except scanner tuned to iron in the haemoglobin
- Activated brain cells call up more fresh oxygenated blood (hides the iron), fMRI indirectly tells us about brain activity through oxygenation in the blood tissue
- Blood Oxygen Level Dependent (BOLD)
13
Q
Positron Emission Tomography (PET)
A
- Contrast agent specifically targeted to the biological process we want to image
- Excellent for informing on specific biological processes (fMRI limited at this)
- Poor spatial + temporal resolution compared to fMRI
14
Q
Electroencephalography (EEG)
A
- Indicates regional brain activity underlying electrodes - good temporal, poor spatial resolution
- Complex/time consuming analysis
- Signals seperate into frequency bands (diff bands = different neurophysiological processes)
- EEG + other techniques can look at brain responses to specific stimulus (Event Related Potential [ERP])
15
Q
Magnetoencephalography (MEG)
A
- Other side of ‘electromagnetic coin’ to EEG
- Detects (small) magnetic field produced by electrical current from a large number of cells
- Less interference by skull + scalp so offers better spatial resolution than EEG
16
Q
What are two imaging techniques that stimulate the brain
A
Transcranial Magnetic Stimulation (TMS)
- Induces electrical current in brain tissue which disrupts ongoing activity so their role in cognitive function can be assessed
Transcranial Direct Current Stimulation (TDCS)
- Pass mild current through brain, between positively charged anode + negatively charged cathode
- Can excite/inhibit underlying brain tissue
- Easy self-administration means it can be misused
17
Q
What are the 3Rs (guiding principles) in Invasive Methods in Animal Models
A
Strictly regulate by Home Office, requires justification of cost/benefit
- Replacement (can another method be used)
- Refinement (can it be done in a better way, that further maximises cost/benefit)
- Reduction (can it be done with less animals/ones further down phylogenetic tree)
18
Q
What are some possibilities with invasive methods (animal models make it possible to do things we cannot [usually] do in humans
A
- Make direct measurements of activity in brain cells (can be intra cellular (electrode inside cell itself vs extra cellular)
- Determine connectivity between structures + flow of information (can see if structures connect by injecting a tracer)
- Anterograde tracer (goes from source [cell body/soma] to termination [synapse])
- Retrograde tracer (goes termination [synapse] to the source [cell body/soma] - Disrupt connectivity between structures to determine effects on circuit function (effect on behaviour / activity in structures)
- Lesion specific structures - inform about what function that structure performs
- Difficult to lesion one and not impact other areas
19
Q
What are the different directional planes in the brain?
A
Coronal plane (across / vertical)
Horizontal plane (horizontal)
Sagittal plane (straight through / side)
20
Q
Explain the Central Nervous System and the Peripheral Nervous System
A
Central Nervous System (brain and spinal cord)
Peripheral Nervous System (everything outside the skull and the spine)
Two subdivisions of the PNS:
1. Somatic nervous system - interacts with external environment (senses)
- Autonomic nervous system - regulates body’s internal environment (internal organs)
Each system made up of:
Afferent nerves - things affected by the outside world (sensory signal) - dorsal root (back of brain)
Efferent nerves - having an effect on the world (motor commands) - ventral root (front of brain)
21
Q
What are the three subdivisions of the brain
A
Hindbrain
- Medulla
- Metencephalon (‘cerebellum’ and ‘pons’)
Midbrain
- Tectum (colliculi / “little hills”)
- Tegmentum (“roof”) - three colourful structures
Forebrain
- Thalamus (hallway)
- Hypothalamus
22
Q
Explain the functions of the Hindbrain
A
Medulla
- carries signals between brain and body
- involved in low level sensorimotor control (balance)
- involved in variety of vital functions (sleep/wakefulness, cardiac, respiratory reflexes)
Metencephalon (contains cerebellum “little brain” and the pons)
- Relays from cortex + midbrain to cerebellum
- low level guidance in movement
23
Q
Explain the functions of the Midbrain
A
Tectum (colliculi / “little hills”)
- Superior Colliculus (sensitive to sensory change - orienting/defensive movement)
- Inferior Colliculus (similar, but for auditory events)
Tegmentum (“roof”) three colourful structures
- Periaqueductal gray (system involving pain)
- Red nucleus (motor control esp arms + legs)
- Substantia nigra (involved in Parkinson’s disease - loss of dopamine)
24
Q
Explain the functions of the Forebrain
A
Thalamus (hallway)
- Relay structure
Hypothalamus
- Regulates pituitary glands (hormone secretion)
- Regulates 4 F’s of human behaviour (Feeding, Fighting, Feeling (temp/pain), Fucking)
25
What is the Cerebral Cortex made up of?
- White matter: fibres/axons
- Gray matter: (6 layers) some layers info comes in, some layer send info to other parts of the brain
- Biggest part of the brain in primates
26
Briefly explain the structures that light travels through in the eye
- The iris regulates the size of the pupil, which controls the amount of light entering the eye
- The cornea (75% of focus) + the lens focus the light on the retina
- The retina converts the light into neural signals, which then travel down the optic nerve
- Some initial processing is carried out by the retinal circuit, relating to colour and contrast sensitivity
27
What are the two properties of the sensory system that allow for the after effects illusions
1. Feature Detection: The brain has specific neurons / circuits of neurons specialised for detection particular features of the sensory world (edges, lines, movement in particular directions), illusions often trick a specific 'feature detection' system
2. Adaptation: The brain is mainly interested in changes to your environment, when a feature remains constant (even if the feature is movement), neural signals are 'dampened down' (no longer as important)
28
What are the three main layers of cells in the retina?
1. Photoreceptors (convert light into neural signals) Two types:
- Rods (scotopic - dim light, don't allow us to see in colour. Outnumber cones, except in fovea)
- Cones (photopic - well lit. Three types: red, green, blue, allow us to see colour in normal lighting)
2. Bipolar Cells
- Process input from photoreceptors and output to the retinal ganglion cells
- Allow some low-level signal processing in retina, aided by interneurons (horizontal and amacrine cells)
3. Retinal Ganglion Cells
- Wired up to bipolar cells + photoreceptors in such a way to facilitate the detection of edges in images
29
What are the Macula and the Fovea?
Macula
- Centre of the retina, contains high concentration of photoreceptor cells
Fovea
- Centre of the macula, provides highest acuity vision
- No rods, lots of cones
- Eye continually scans visual field with the fovea, making 3 fixations per second as brain can't handle constant foveal vision
30
What is the Optic Disk
- Ganglion cell axons leave the retina in a cluster called the optic disk, which has no photoreceptors, creating a blind spot
- Brain uses completion (info from around blind spot to fill the gap
- After leaving the retina, ganglion cells are called optic fibres + carry visual info to the brain to be processed
31
Why do our eyes reflect red when a flash photo is taken
- Flash from the camera is reflected off of blood vessels in the choroid (layer of tissue between the sclera and the retina) and back through the pupil
- Many nocturnal animals have a layer of reflective tissue called tapetum lucidum
32
What does it mean to have Colour Blindness
- A range from near normal vision (trichromats) to monochromacy
- Either altered sensitivity in one of the cones or absence of a cone
- Deuteranomaly is most common - 'green' cones shifted towards 'red', making reds + greens hard to distingush
- 8% men and 0.5% women have colour vision deficiency
33
Explain how Lateral Inhibition works
- First identified in eyes of horseshoe crab - contain large visual receptors called ommatidia
- When light hits the ommatidia (photoreceptors), they fire at a rate proportional to the intensity of the light
- The more they fire, the more they inhibit neighbouring receptors
34
Explain how the Hermann Grid illusion works
- Grey blobs appear in the grid
- The blobs at the intersection disappear when the intersection is foveated
- This is caused by 'lateral inhibition' - intersection is surrounded by more activated receptive fields
35
Explain how Mach Bands work
- The apparent change in lightness between bands is caused by lateral inhibition
- Mediated by horizontal cells, which inhibit other cells they contact when activated
36
Explain how Visual Pathways project contralaterally
- Retinal ganglion cells sensitive to light in left + right visual fields have different projections in optic nerve
- They separate at the optic chiasm, so info from the left and right field projects contralaterally to Superior Colliculus and Visual Cortex
37
What does the Retino-Geniculate Striate Pathway do
This pathway takes information from the retina to the lower layer of the Primary Visual Cortex (V1) via the Lateral Geniculate Nuclei (LGN) of the Thalamus
38
Explain the properties of Parvocellular + Magnocellular layers
Parvocellular (P-Layers)
- Small cell bodies
Responsive to colour, fine detail and stationary/slow moving objects (good for scene analysis identification)
- Cones provide the majority of input
Magnocellular (M-Layers)
- Large cell bodies
- Particularly responsive to luminance change - on/off movement
- Rods provide majority of the input
- Similar properties to Superior Colliculus
39
What is the most basic unit of the motor system?
The motor unit
40
What are the three types of muscles
Skeletal, Smooth, Cardiac
41
What is Antagonistic arrangement
Combined, co-ordinated action
42
Explain the key features of a Motor Unit
A motor unit = a single alpha motor neuron + all the muscle fibres it innervates
- Different motor neurons innervate diff muscle fibres - fewer fibres = greater movement precision + less force (eyelids)
- Activation of alpha motor neuron depolarises + causes contraction of all fibres in that unit (all or none)
- More motor units fire = more fibres contract = more power
43
What is a Motor Pool
- All lower motor neurons that innervate a single muscle
- Contains both alpha + gamma motor neurons
- Often arranged in a rod like shape
44
What does a good control system (CNS) need to know to provide movement
1. How much tension is in the muscle (Golgi Tendon Organs sense tension)
- Sends ascening sensory information about force in the brain to brain via spinal cord
- Info sent back about muscle movement
2. What is the length (stretch) of the muscle (Muscle Spindles sense stretch)
- These sense stretch and form key part of reflex circuits
45
Explain descending projections from cortical motor areas
Coordinating motor commands
- Motor command originates in motor cortex pyramidal cells (layer 5-6 motor neurons)
- Pyramidal cell axon can project directly / indirectly to spinal cord + onto lower brainstem motor neurons
- Most cortical projections innervate contralateral motor units
46
Give a brief overview of Motor Control
- The motor cortex issues commands to lower motor neurons + interneurons
- Copies also sent to Cerebellum + Basal Ganglia
- This is then fed back into motor cortex
- Cerebellum feeds back Excitatory info / Basal Ganglia feeds back Inhibitory info
47
Explain descending projecting from Motor Cortex
Either through:
Dorsolateral Tracts
- Travel via red nucleus
- Project to distal muscles (fingers)
Ventromedial Tracts
- Travel via tectum, vestibular nuclei
- Project to proximal muscles of trunk/limbs
48
Explain the functions of the Basal Ganglia
- Basal Ganglia are group of nuclei deep in the cerebral hemisphere
- Dysfunction implicated in many disorders (Parkinson's) characterised by involuntary repetitive tremors/movement
- Inhibits the Thalamus (relays info to Cortex)
- Receives excitatory info from areas of cortex
- Output goes back to Cortex via thalamus
49
Explain the role of Basal Ganglia in Disinhibitory gating of motor cortex output
- When no input goes to Globus Pallidus (inhibitory structure), it remains tonically active - no output to motor neurons
- When Dopaminergic Input from Substantia Nigra sent - Globus Pallidus transiently inhibited - allows excitation in motor cortex + output to motor neurons
50
Explain Cerebellum function + what happens when the Cerebellum is damaged
- Cerebellum contains half of CNS neurons but only 10% of brain weight (packed)
- Computes motor error and adjusts cortical motor commands accordingly
- When damaged, movement becomes jerky, errativ, poorly coordinated
- Dysarthia (disruption to fine speech control) can occur
51
Explain the inputs/outputs to Cerebellum
Inputs
- Spinal Cord (proprioceptive information)
- Cerebral Cortex (Pons) - (copies of motor commands
- Vestibular System (head movements)
Outputs
- Thalamus - leading to the Motor Cortex
52
Briefly explain Parkinson's disease and some symptoms
Brain disorder resulting from deficiency in single neurotransmitter (Dopamine)
Affects 0.5% population, 2.5x more common in men
Symptoms
- Paucity of spontaneous movement (insufficiency of movement)
- Bradykinesia (very slow movements)
- Akinesia (no movements)
- Increased muscle tone (rigidity)
- Resting tremor (pill rolling)
53
What is the role of the Motor Cortex
Planning, initiating and directing voluntary actions
54
What are some treatments for Parkinson's
Deep Brain Stimulation
- Tiny electrodes (over)stimulate the Globus Pallidus, inhibiting it which controls tremors and chronic movement disorders
Replacing lost Dopamine
Surgical intervential
- Lesions
- Electrical stimulation of basal ganglia
55
Explain the role of the Basal Ganglia
- Receives excitatory input from many areas of the Cortex
- Outputs mainly inhibitory signals back to the Cortex via the Thalamus
- Sometimes receives Dopaminergic input from Substantia Nigra, which inhibits the Globus Pallidus, allowing excitation in Motor Cortex (control of motor commands)
56
What are some symptoms experienced by people with depression
Cognitive - Difficulty with concentration/making decisions
Behavioural - Social withdrawal
Somatic (physical) - insomnia, hypersomnia
Affective (mood) - depressed mood/feelings of worthlessness/guilt
57
What are 4 subtypes of depression
Reactive depression - triggered by negative life event
Endogenous depression - no specific life event trigger
Unipolar affective depression - depression (6% incidence)
Bipolar affective depression - depression with manic episodes (1% incidence)
58
What are the concordance rates of depression in twins
Monozygotic (1 egg) - 60% concordance
Dizygotic (2 eggs) - 15% concordance
59
What did Brown (1993) find in his study on depression and the environment (stress in past year)
84% depressed individuals experienced severe stress in the past year
32% control group experienced severe stress in the past year
60
What is the monoamine theory of depression
- Anti-depressants act on monoamines (dopamine, noradrenaline, serotonin) since its theorised that depression is caused by a deficit of monoamine neurotransmission
- There is some evidence of elevated receptors in depressed patients (to compensate for low levels of transmission)
61
Explain how Tricyclic Antidepressants work
Chemical structure includes a three-ring chain
- Block reuptake of transmitter, leaving more of the transmitter at the synapse)
Some tricyclic drugs only work on serotonin (SSRI) (prozac)
62
What is an example of a common SSRI drug + what does it do
Selective Serotonin Re-uptake Inhibitor
PROZAC also known as Fluoxetine
Blocks reuptake of serotonin, leaving more at the synapse
MDMA also blocks reuptake up serotonin & reverses reuptake transporter, leaving a lot of serotonin in the synapse
63
What are dichotomous traits (Mendel)
Mendel studied the pea plant, where there are either green pods [GG] or yellow pods [yy] (dichotomous traits)
64
# Define these key terms in relation to Mendel's work
Phenotype
Genotype
Allele
Heterozygous
Homozygous
Dominant/Recessive gene
Autosomal
- Phenotype - trait/characteristic (yellow vs green)
- Genotype - genetic material (yy / GG)
- Allele - different forms of the gene that control the same trait
- Heterozygous - Gy
Homozygous - GG/yy
G is dominant to y
y is recessive to G
Autosomal - referring to chromosome that is not a sex chromosome (22 autosomal chromosomes)
65
What is a punit square used for
It's a 3x3 square used to plot genes
66
If a recessive gene is found on the X chromosome, will its effects be found more in males or females?
It's effects with be found more in males (xy) because they don't have another x chromosome which could counteract it
Females have 2 x chromosomes, and so they would need double the amount of chromosomes carrying the trait
67
What does DNA stand for?
DNA = Deoxyribose Nucleic Acid (made up for C G AT)
68
How does DNA become a protein
DNA is transcribed into mRNA, which is translated into a protein
69
What is RNA and mRNA?
RNA is a complimentary copy of one strand of a DNA molecule
mRNA = messenger RNA
70
Why is having 3 chromosomes a problem?
Can lead to problems like Down Syndrome
There are three times the amount of proteins
In terms of chromosome 21 (gene involved with Alzheimer's), there would be more development of plaque in the brain
71
What happens when you have a mutation in an enzyme
The enzyme might stop working which could lead to an accumilation
As happens with PKU
72
What is heritability (behavioural genetics) and how is it calculated?
An estimate of how much variance in a characteristic within a population is due to heredity/genetics (measured from 0 - 1)
Calculated by comparing the correlation coefficients of indentical/non-identical twins for particular trait
73
If a group of individuals share a highly similar environment, what effect does this have on heritability estimate of a characteristic?
The heritability estimate will be high
74
What is the Multiplier effect?
If a genetic/prenatal influence produces a small increase in an activity, the early tendency will change the environment in some way that magnifies the tendency
e.g. child good at football from a young age more likely to practice more, resulting in increased ability later in development
75
What's the Weinberger approach to genes
Genes - Neurophysiology - Cognition
76
Explain the study that looked into a mutant form of Tryptophan Hydroxylase (Zhang et al., 2005)
In Vitro (grown in dish) cells with this gene produce 80% less serotonin
Study - In depressed group, 9 ps had mutant form, and only 3 in control group had mutant form
- Those three that had mutant form also the only 3 to have psychiatric problems/family history of problems
77
Explain the link between the gene for serotonin transporter (5-HTT) and depression/anxiety
+ Caspi et al. (2003) study
The gene has 2 forms: short (s) and long (l)
Short form leads to increased risk of anxiety/depression (higher brain activation to negative emotions)
Caspi et al. (2003)
- Measured stressful life events, divided into groups based on forms of 5-HTT (ll, ls, ss)
Results
- No diff between live events and genetic groups
- Significant interaction between genes + environment on depressive symptoms (those with ss genes have more depressive symptoms with more stressful life events)
