NEUR200 Exam 2 Questions

What is the presynaptic neuron versus the postsynaptic neuron?

Presynaptic neuron = sends the signal (its axon terminal releases neurotransmitter). Postsynaptic neuron = receives the signal (its membrane has the receptors).

What was Sherrington's major contribution and how did he reach it?

He identified synaptic delay. By studying the reflex arc he found conduction through it was never faster than ~15 m/s, while axonal conduction is ~40 m/s, so the delay occurs where neurons communicate (the synapse). He was one of the first to use the term 'synapse' (Nobel Prize 1932).

How do graded potentials differ from action potentials?

Graded potentials vary in size and can be depolarizing (excitatory) or hyperpolarizing (inhibitory); action potentials are all-or-none.

What causes an EPSP and what does it do?

Na+ entering the cell causes a temporary graded depolarization, making the cell more likely to fire an action potential.

What causes an IPSP and what does it do?

K+ leaving the cell or Cl- entering it causes a temporary graded hyperpolarization (more negative inside), making the cell less likely to fire.

What is spatial summation?

Synaptic inputs from separate locations on a neuron combine their effects (summation over space).

What is temporal summation?

Repeated stimuli within a brief time have a cumulative effect; a second EPSP can add to the first before it decays, and if the sum exceeds threshold an action potential is produced.

What is spontaneous firing rate and how do EPSPs/IPSPs affect it?

Periodic production of action potentials even without synaptic input. EPSPs increase firing above this rate; IPSPs decrease it. Ongoing activity may influence perception of weak stimuli.

What is neural synchronization?

Brain waves from different regions synchronize (network communication between distant areas); synchronized neuron activity can produce oscillations.

What role does calcium play in neurotransmitter release?

The action potential opens Ca2+ channels in the axon terminal; Ca2+ enters and triggers proteins that cause vesicles to fuse with the membrane (exocytosis), releasing transmitter into the synaptic cleft.

Compare ionotropic and metabotropic receptors.

Ionotropic: the receptor is itself an ion channel (Na+, K+, Ca2+, Cl-); effects are fast (

Why are metabotropic receptors slower?

They don't open a channel directly; a second messenger and intracellular chain of steps must occur first (but it can affect many parts of the cell and last longer).

What are monoamines? Name them.

Modified amino acids used as neurotransmitters: dopamine, serotonin and norepinephrine (noradrenaline).

What functions are linked to dopamine, and what are its receptors?

Receptors D1-D5. Movement (Parkinsonism), reward, motivation and cognitive control (ADHD), psychosis (hallucinations). Drugs: antipsychotics, stimulants, recreational drugs.

Where is dopamine mainly synthesized in the brain?

Substantia nigra (SN) and ventral tegmental area (VTA), which lie next to each other.

Dopamine pathway 1: name and structures

Mesocortical: VTA

Dopamine pathway 2: name, structures and role

Mesolimbic (reward pathway): VTA

Dopamine pathway 3: name, structures and role

Nigrostriatal: substantia nigra

Where is norepinephrine made, which receptors does it use, and what does it do?

Locus coeruleus in the brain; adrenal gland in the PNS. Alpha and beta receptors. Energy, arousal, mood (depression, anxiety).

Where is serotonin made and what does it do?

Raphe nuclei. Sleep and wakefulness, mood (depression); highest when animals are awake. Drugs: SSRIs, TCAs, MAOIs.

What did we cover about correlation/anticorrelation of DA, NE and serotonin?

Not in the slides - fill in from your class notes.

What are glutamate's role and receptors?

Most important excitatory neurotransmitter. Receptors: AMPA and NMDA. Linked to psychosis; too much causes excitotoxicity.

What are GABA's role, receptors and drugs?

Inhibitory (IPSPs via Cl- influx). Receptors GABA-A, GABA-B, GABA-C. Drugs: benzodiazepines.

Acetylcholine: receptors, source and functions

Nicotinic and muscarinic receptors; nucleus basalis of Meynert; muscles, memory and attention.

Which population has low levels of acetylcholine?

Alzheimer's disease patients.

List the stages of maturation of the vertebrate brain.

Proliferation, migration, differentiation, myelination, synaptogenesis, synaptic pruning.

What happens with overproliferation versus reduced proliferation of cells?

Overproliferation -> megalencephaly; reduced proliferation -> microencephaly.

How is migration of neurons guided, and what if it fails?

Chemicals guide migration (until adulthood); deficits lead to decreased brain size and decreased axon growth.

In differentiation, which grows first: axons or dendrites?

Axons grow first; dendrites form after migration, when neurons reach their destination.

How long does myelination continue?

Gradually through adolescence and adulthood (e.g., isolated mice show impaired adult prefrontal myelination).

Which condition is associated with too much synaptic pruning?

Schizophrenia.

How does experience fine-tune the brain?

Stimulating environments enhance sprouting of axons and dendrites; physical activity maintains intellectual vigor (aerobic exercise, BDNF); prolonged experience (especially from childhood) improves that function; blind people use occipital cortex for touch; music practice reorganizes the brain.

What is the hierarchy of function from spinal cord to cortex?

Spinal cord: reflexes. Hindbrain: postural support. Midbrain: spontaneous behavior. Diencephalon: motivation. Basal ganglia: self-maintenance. Cortex: control and intention.

Hindbrain: structures and function

Medulla (breathing, heart rate), pons ('bridge'), cerebellum ('little brain', motor coordination); also locus coeruleus and raphe nuclei. Disconnection from the rest of the brain -> vegetative state.

Midbrain: structures and function

Superior colliculus (vision) and inferior colliculus (hearing); VTA and substantia nigra. Spontaneous reactions to stimuli (e.g., attack response to moving objects), not motivated behavior.

Diencephalon: structures and function

Thalamus (switchbox for sensory info), hypothalamus (sleep, eating, sex, thermoregulation), pituitary (hormones). Motivation; behavior more energized and sustained.

Basal ganglia: structures and function

Caudate nucleus, putamen, globus pallidus (+ substantia nigra from midbrain). Looping connections with cortex; learn simple automatic sequences (grooming, copulation, feeding) without cortex.

Cortex: what does it add behaviorally?

Control and intention: pro-active behavior, skilled movements and sequences (e.g., language), extending learned behavior to new situations, solving problems and making plans.

What structures make up the limbic system?

Hippocampus, cingulate gyrus, olfactory bulb, amygdala (also fornix, septal nuclei, stria terminalis, mammillary bodies); emotion, learning and memory.

What do cortical layers do?

Layers = input and output. Layer IV: input zone (large in sensory areas). Layers V and VI: output zone (large layer V, small IV in motor areas). Layers II and III: integrate inputs from other cortical areas with layer IV input.

What are cortical columns and what did Hubel and Wiesel show?

Columns = vertical modules where most neuron interaction occurs; neurons in a column are functionally similar; most apparent in primary sensory areas (e.g., ocular dominance columns in area 17). Hubel and Wiesel (1959) found V1 cells in cats respond to specific stimulus orientations.

What energy type does each sense detect?

Vision: light. Audition: pressure changes in the air. Touch: pressure changes in the skin. Smell and taste: chemicals.

What is transduction?

Receptors transform energy into electrical energy; it occurs in the receptors.

Where are rods and cones and what do they do?

Cones: mostly in the fovea (acute, detailed vision). Rods: in the periphery (better sensitivity to dim light).

Describe the geniculostriate pathway and its function.

Retina -> lateral geniculate nucleus (thalamus) -> striate cortex (V1) -> other visual cortical areas. Pattern, color and motion recognition.

Describe the tectopulvinar pathway and its function.

Retina -> superior colliculus (tectum, midbrain) -> pulvinar nucleus (thalamus) -> parietal lobe/other areas. Spatial location of objects; unconscious.

Which areas in the visual pathway diagram are thalamic?

The lateral geniculate nucleus (LGN) and the pulvinar nucleus.

What do V1, V4 and V5/MT do?

V1 (striate cortex): first cortical analysis (orientation). V4: color. V5/MT: motion perception.

What are the ventral and dorsal streams?

Ventral = 'what' pathway toward temporal cortex (object identity; prosopagnosia). Dorsal = 'where/how' pathway toward parietal cortex (location and guiding action; neglect).

Name the ventral and dorsal stream regions beyond the occipital lobe.

Ventral: FFA (faces), EBA (bodies), STS (biological motion), PPA (scenes/places). Dorsal: parietal reach region (visually guided reaching).

What is hemianopia?

Blindness of half the visual field (right or left) due to damage in the opposite V1.

What is blindsight (cortical blindness)?

People with anopsia or hemianopia respond to stimuli they don't consciously see (features like movement can help).

What is cortical color blindness?

Loss of color vision from damage to V4; imagery and memory of color are affected too (Sacks and Wasserman, 1987; case J.I.).

Apperceptive vs. associative agnosia

Apperceptive: cannot form a percept (cannot copy an object). Associative: can perceive/copy but cannot recognize the object.

What is prosopagnosia?

Difficulty recognizing familiar faces; bilateral fusiform area damage (right hemisphere more important).

What is alexia?

Word blindness: inability to read; damage to the left fusiform area. Can read letter by letter and may trace letters (motion) to read.

What is simultagnosia?

Problems perceiving more than one object at a time; can follow dorsal stream damage (e.g., Balint's syndrome, a spatial attention problem).