bio-psych midterm 2

What does "dorsal" mean?

Toward the back/top of the brain

What does "ventral" mean?

Toward the belly/bottom

Ipsilateral vs contralateral?

Ipsilateral = same side, contralateral = opposite side

What are the 3 planes of section

Horizontal (top-down), sagittal (left-right split), coronal (front-back split)

Dorsal roots carry what?

Sensory/afferent info into spinal cord

Ventral roots carry what?

Motor/efferent info out of spinal cord

Grey vs white matter?

cell bodies/dendrites/synapses, white = myelinated axon tracts

Sympathetic NS function?

Fight or flight, increases HR, dilates pupils, inhibits digestion

Parasympathetic NS function?

Rest and digest, slows HR, constricts pupils, stimulates digestion

Somatic NS?

Voluntary skeletal muscle control

What divides the PNS?

Somatic (voluntary) and autonomic (sympathetic + parasympathetic)

Anterior vs posterior?

Anterior = toward the front, posterior = toward the back

Medial vs lateral?

Medial = toward midline, lateral = away from midline

Superior vs inferior?

Superior = above, inferior = below

What is the Mu rhythm?

An "idling" brain rhythm prevalent during low sensory attention

What is the difference between electrical and chemical transmission?

Electrical = fast and fixed (gap junctions), chemical = slower but modifiable (synaptic cleft)

What are the phases of an action potential?

Depolarization, peak (absolute refractory), repolarization (relative refractory), hyperpolarization

What happens during absolute refractory period?

No new AP can fire regardless of stimulus strength

What happens during relative refractory period?

A stronger than normal stimulus CAN trigger a new AP

What is a local field potential (LFP)?

Aggregate electrical activity from a population of neurons, larger scale than single-unit recording

Frontal lobe functions?

Executive function, planning, motor control (M1), personality, decision making

Parietal lobe functions?

Somatosensory integration, spatial awareness, attention

Temporal lobe functions?

Auditory processing, visual object recognition, language comprehension

Occipital lobe functions?

Primary visual processing

What landmark separates frontal and parietal lobes?

Central sulcus

What landmark separates temporal from frontal/parietal?

Sylvian (lateral) fissure

What separates parietal from occipital?

Parieto-occipital sulcus

What is the limbic system?

A functionally connected (not physically separate) set of structures for emotion and memory

Key limbic structures?

Hippocampus, amygdala, cingulate cortex, hypothalamus

What does the hippocampus do?

Episodic memory formation and spatial navigation

Patient H.M.?

Bilateral hippocampus removal, lost ability to form new episodic memories but retained procedural memory

What does the thalamus do?

Relay station, routes sensory info to appropriate cortical areas (except smell)

What does the hypothalamus do?

Regulates homeostasis: hunger, thirst, temperature, hormones, circadian rhythms

What is the cerebellum?

Coordinates movement timing, balance, motor learning

What does the medulla do?

Controls vital autonomic functions: breathing, heart rate, blood pressure

What are the basal ganglia?

Subcortical nuclei involved in motor initiation, habit learning, reward

What is CSF and what does it do?

Cerebrospinal fluid, cushions brain, removes metabolic waste, circulates through ventricles

Bottom-up vs top-down processing?

Bottom-up = building perception from raw sensory details, top-down = using prior knowledge/expectations to interpret input

Cortical layer development pattern?

Inside-out, layer VI develops first, layer I last

Which cortical layers expanded in primates?

Layers II and III

What does the prefrontal cortex do?

Higher order executive function, planning, impulse control, working memory

What is the "later becomes larger" evolutionary pattern?

Brain regions that develop later in embryology tend to be proportionally larger in more complex species

Ionotropic receptors?

Ligand-gated ion channels, fast acting (ms), direct ion flow

Metabotropic receptors?

G-protein coupled receptors, slower (sec to min), modulate cell via second messengers

Examples of ionotropic?

Nicotinic ACh, GABA-A, AMPA, NMDA

Examples of metabotropic?

Muscarinic ACh, dopamine receptors, GABA-B

Why is chemical signaling advantageous over electrical?

Allows signal integration, longer lasting responses, graded responses, and diversity

What is signal integration?

Neuron summates EPSPs and IPSPs to decide whether to fire

What is an EPSP?

Excitatory post-synaptic potential, makes neuron more likely to fire

What is an IPSP?

Inhibitory post-synaptic potential, makes neuron less likely to fire

GABA's role?

A: Primary inhibitory NT in the brain

What targets GABA-A receptors?

Benzodiazepines (enhance GABA binding, sedation/anxiolytic - anxiety reduction)

ACh functions?

NMJ muscle contraction, attention, memory, arousal

What does scopolamine do?

Muscarinic ACh antagonist, blocks ACh at metabotropic receptors, causes drowsiness/memory impairment

Dopamine functions?

Motor control, motivation, reward, reinforcement

Dopamine and Parkinson's?

Loss of dopaminergic neurons in substantia nigra causes motor symptoms

Dopamine and ADHD?

Adderall increases DA availability, improves focus

What do antipsychotics do?

Block dopamine receptors (D2 antagonists), treat psychosis/schizophrenia

What is a PSTH?

Peri-stimulus time histogram, plots spikes/sec over time relative to stimulus onset

Spontaneous vs evoked firing?

Spontaneous = baseline rate without stimulus, evoked = change in rate due to stimulus

EEG vs single-unit?

EEG = scalp recording of aggregate cortical activity, single-unit = electrode recording one neuron's APs

What is an agonist?

Drug that activates a receptor (mimics the NT)

What is an antagonist?

Drug that blocks a receptor (prevents NT from binding)

What is haloperidol?

D2 dopamine antagonist, antipsychotic

Pacinian corpuscles?

Deep pressure and vibration, rapidly adapting, large receptive field

Meissner corpuscles?

Light touch and texture, rapidly adapting, small receptive field, concentrated in fingertips

Merkel discs?

Sustained pressure and form, slowly adapting, small receptive field

Ruffini endings?

Skin stretch, slowly adapting, large receptive field

Free nerve endings?

Nociceptors for pain, also temperature

Rapidly vs slowly adapting receptors?

Rapidly adapting respond to changes (onset/offset), slowly adapting respond continuously to sustained stimulation

What is a receptive field?

The area of skin where stimulation activates a particular neuron

Full somatosensory (touch) pathway?

Receptor -> peripheral nerve -> dorsal root ganglion -> dorsal column of spinal cord -> medulla (decussation/crossing) -> ventral posterior thalamus -> S1 (parietal cortex)

What is the dorsal column-medial lemniscus pathway?

The main touch pathway, carries fine touch/proprioception, crosses at the medulla

Full pain (nociception) pathway?

Free nerve ending -> A-delta or C fibers -> dorsal horn of spinal cord (crosses here) -> spinothalamic tract -> thalamus -> S1 and anterior cingulate cortex

A-delta fibers vs C fibers?

A-delta = myelinated, fast, sharp pain. C fibers = unmyelinated, slow, dull/burning pain

Key difference between touch and pain pathways?

Touch crosses at medulla, pain crosses at spinal cord level. Pain also targets emotional areas (ACC)

What is somatotopy?

Organized mapping of body surface onto cortical areas

What is the homunculus?

Distorted body map in S1 where size reflects sensitivity (hands and lips are huge)

What is phantom limb?

Sensation in a missing limb caused by cortical reorganization, neighboring cortical areas invade the deprived territory

What is musician's dystonia?

Cortical reorganization from repetitive finger use, areas merge and lose distinct representation

What is the Gate Theory of Pain?

Non-painful input (touch) can close the "gate" to pain signals in the spinal cord dorsal horn, blocking them from reaching the brain

What opens the pain gate?

C fiber activity (slow pain), emotional stress, anxiety

What closes the pain gate?

A-beta fiber activity (touch), endorphins from periaqueductal grey and medulla

What is the periaqueductal grey (PAG)?

Brainstem structure that releases endorphins to modulate/suppress pain signals

Why does rubbing an injury help?

Activates A-beta mechanoreceptors which close the pain gate via lateral inhibition in the dorsal horn

What is the spinothalamic tract?

Ascending pathway for pain and temperature, crosses at spinal cord, projects to thalamus

Why does pain activate the anterior cingulate cortex?

ACC processes the emotional/affective component of pain (the "unpleasantness")

What is transduction for touch?

Physical pressure deforms receptor -> mechanically gated ion channels open -> depolarization -> AP

What is the placebo effect in pain?

Belief in treatment triggers real endorphin release, actually reduces pain perception via descending inhibition

Anatomy of the eye path of light?

Cornea -> aqueous humor -> pupil -> lens -> vitreous humor -> retina

What does the cornea do?

Primary light refraction/focusing

What does the lens do?

Fine-tunes focus via accommodation (changes shape for near/far)

What controls pupil size?

Iris muscles, constricts in bright light, dilates in dim

Rods?

~120 million, peripheral retina, low light sensitivity, no color, high convergence onto ganglion cells

Cones?

~6 million, concentrated in fovea, color vision, high acuity, low convergence

What is the fovea?

Center of retina, highest cone density, sharpest vision, no rods

Why is peripheral vision blurry?

High rod convergence = many rods feeding one ganglion cell = less spatial precision

Why is foveal vision sharp?

Low cone convergence = nearly 1:1 cone to ganglion cell ratio

Blind spot?

Where optic nerve exits retina, zero photoreceptors

Full phototransduction cascade?

Light hits rhodopsin (in rods) or photopsin (in cones) -> conformational change -> activates transducin (G-protein) -> activates PDE -> breaks down cGMP -> Na+ channels close -> hyperpolarization