Midterm

sensory system

sensory system

part of the NS that reports info about the state of the organism and environment

motor system

part of the NS that organizes and generates movement

associational system

part of the NS that provides higher order brain functions, such as perception, attention, memory, emotions, language, and thinking

central nervous system

part of NS subdivided into brain and spinal cord

peripheral nervous system

part of NS subdivided into sensory, somatic, and autonomic divisions

reticular theory

idea that all neurons form a continuously connected network

neuron doctrine

neurons communicate at synapses rather than through physical activity

neuron

NS cell which processes info, senses environmental changes, communicates changes via electrical signaling, and controls body responses

dendrite

branchy target for synaptic input from axon terminals of other neurons whose complexity increases with the number of inputs

axon

shaft responsible for signal transduction from cell body; reads out info

action potential

all or nothing changes in electrical potential made by Nodes of Ranvier, requiring Na to allow neuron to reach threshold and K to bring it back down

Node of Ranvier

gap between myelin that propagates action potentials

saltatory conduction

action potentials jumping between Nodes of Ranvier, enhancing velocity

presynaptic terminal

where molecules are secreted into synaptic cleft, immediately adjacent to dendrite of next cell

postsynaptic specialization

areas of dendrites w/ receptors for molecules to bind, immediately adjacent to axon terminal of previous cell

synaptic cleft

gap between pre- and post- synaptic terminals

glia

NS cell which supports the signaling function of, insulates, nourishes, and supports neurons; includes astrocytes, oligodendrocytes, Schwann cells, microglia, and stem cells

astrocyte

CNS glial cell maintaining appropriate chemical environment for neuronal signaling, including blood-brain barrier formation

oligodendrocyte

CNS myelin generator

Schwann cell

PNS myelin generator

microglia

scavenger cells that remove cellular debris from injury sites and cell turnover, secrete cytokines

glial stem cell

precursor to glia

afferent

carries info to CNS

efferent

carries info away from CNS

interneuron

CNS cell that participates in local aspects of circuit function, such as DRG

agonist

muscle that performs target movement (extensor in knee jerk reflex)

antagonist

muscle that opposes target movement (flexor in knee jerk reflex)

divergent circuit

neural circuit that spreads info

convergent circuit

neural circuit that integrates info

electrophysiological recording

technique to probe neural circuit function, subdivided into intracellular and extracellular recording

extracellular recording

an electrode is placed outside a neuron to detect temporal patterns of AP activity

intracellular recording

an electrode is placed inside a neuron to detect small. graded changes in electrical potential that can trigger APs and assesss communication among neurons w/in a circuit

calcium imaging

recording transient changes in [Ca] ion associated w/ AP firing to infer neural activity changes, where neurons are labeled w/ a Ca sensitive dye and then imaged

optogenetic

method introducing opsins into the NS so a neuron can artificially fire from light to assess neural circuit activity

opsin

bacterial channels transducing light energy into chemical signal activating channel proteins

basal ganglia

group of nuclei that control normal voluntary movement, w/ no direct spinal cord connections, made up of striatum (caudate & putamen), pallidum (globus pallidus & SNPR), SNPC, and subthalamic nucleus; uses center surround decision making

striatum

input nuclei of the basal ganglia made up of caudate and putamen, shrinks in Huntington’s

caudate

cortical inputs from multimodal association cortices and frontal lobe motor areas that control eye movement

putamen

cortical inputs from primary and secondary somatosensory cortices in parietal lobe, extrastriate visual, premotor, motor, and auditory association cortices

pallidum

output nuclei of the basal ganglia

globus pallidus

pallidum region responsible for MSN activity; internal relays to inhibit VA/VL thalamic nuclei, external degenerates in Huntington’s

substantia nigra pars reticula

pallidum region in midbrain that serves as inhibitory output, where axons from medium spiny neurons (MSNs) converge, sends axons to superior colliculus

substantia nigra pars compacta

basal ganglia region responsible for inhibitory output that degenerates in Parkinson’s causing dopamine output to decrease; releases dopamine to the striatum leading to direct pathway activation and indirect pathway inhibition; synapses on MSNs

medium spiny neuron

in striatum, give rise to inhibitory GABAergic projections that terminate in output basal ganglia, receive few inputs from each cortical axon

direct pathway

circuit that releases upper MNs from tonic inhibition and facilitates movement; inhibits internal globus pallidus to release inhibition on VA/VL thalamus to activate cortex, mediate focised activation; damage = trouble tying shoes

indirect pathway

circuit that increases tonic level of inhibition, inhibits movement by inhibiting VA/VL thalamus, and thus output to cortex, suppresses function units

focused selection

theory that direct and indirect pathways are organized in center surround manner

Huntington’s disease

neurodegenerative genetic trinucleotide repeat disease where external globus pallidus neurons degenerate, causing hyperkinetic movement

hemiballismus

damage to the subthalamic nucleus causing violent movements

subthalamic nucleus

region of basal ganglia; damage causes violent involuntary movements; receives input from cerebral cortex; provides inhibitory output to VA/VL complex of the thalamus; release glutamate to internal globus pallidus

Parkinson’s

major degeneration of NS w/ tremor at rest, rigidity, and bradykinesia; can be treated by Levodopa and deep brain stimulation

dyskinesia

difficulty moving

deep brain stimulation

Parkinson’s treatment where electrodes trigger blood flow and neurotransmitter release; parameters determined by trial and error

levodopa

primary pharmacological treatment to get brain to produce dopamine for Parkinson’s

Plato

early scientist (400 BCE) that believed that the eye sent out rays, which seized objects (extramission)

Theophrastus

300 BCE scientist who thought eye has internal fire from which the rays emanate (extramission)

Galen

200 CE scientist who thought optical pneuma was emitted from the eye, considered lens to be origin of vision, since cataracts obstruct vision (extramission)

extramission theory

our eyes shooting out energy causes us to see; 50% of Americans believe it & Plato, Theophrastus, and Galen

intromission theory

our eyes absorbing energy causes us to see, supported by al-Razi, Ibn al-Haytham, and Ibn Sina

al-Razi

900 CE scientist that noticed light levels controlled pupils, supported intromission theory

cornea

clear tissue at front of eye, provides 2/3 of eye’s optical power due to refraction

pupil

opening in the iris which expands (for more light in dim situations) and contracts to control the amount of light entering

lens

tissue that focuses incoming light on retina whose refractive power is affected by ciliary muscles; issues cause most vision issues (eg. myopia, hyperopia); thin for distant objects, thick for near

ciliary muscles

eye muscles that adjust the thickness of the lens

retina

light sensing neural tissue at the back of the eye, which signals via graded potentials, regulated by cGMP gated channels

fovea

centre of retina responsible for HD vision, w/ high [cones] and visual acuity

optic nerve

bundle from retinal ganglion cell axons; pathway where retinal signals get sent to rest of the brain

optic disk

blind spot in retina where it meets the optic nerve, no photoreceptors

myopia

images are focused in front of the retina, far images are blurry, affecting ~50% of people, treated w/ concave lenses

hyperopia

images are focused behind retina, close images are blurry, treated w/ convex lenses, includes presbyopia

presbyopia

age related hyperopia

astigmatism

condition arising from spherical aberrations of the eye, leading to different focal points for different parts of the visual field

retinal

molecule in photopigments which converts between cis and trans to active transducin and begin vision pathwat

transducin

g protein activated by conversion of 11-cis to 11-trans retinal, which activates PDE

phosphoesterdiase

compound activated by transducin, which hydrolyzes cGMP into GMP, which closes gGMP gated ion channels

achromatopsia

true color blindness due to a lack of cones affecting 1/30k people

off bipolar cell

ionotropic cell active in the dark, which is activated by photoreceptors and activates ganglion cells; stratify in deeper layers of IPL and connect to ON ganglion cells

on bipolar cell

cell w/ metabotropic glutamate receptors on dendrites, depolarized by photoreceptors in light, hyperpolarized in dark, activates ganglion cells indirectly through A2 amacrine cells

inner nuclear layer

location of bipolar cell soma

inner plexiform layer

location of bipolar cell axons

amacrine cell

retinal cell that connects on bipolar cells to retinal ganglion cells; can provide lateral inhibition to bipolar and ganglion cells

on center ganglion cell

retinal cell activated by off bipolar cells which are excited by light in the center, inhibited by light in the surround

off center ganglion cell

retinal cell inhibited by light in the center, excited by light in the surround

horizontal cell

retinal cell that provides negative feedback to photoreceptors through lateral inhibition

luminance

physical measurement of light intensity

brightness

sensation elicited by light intensity

color oppency

creating ganglia that prefer different colors, includes parasol (magnocellular), midget (parvocellular) and bistratified (koniocellular)

parasol

center surround retinal ganglion cells responsible for detecting luminance & motion w/ its large receptive field

midget

red/green retinal ganglion cell, w/ small receptive field and high acuity due to small receptive field

bistratified

blue/yellow retinal ganglion cell

optic chiasm

where ~60% of retinal ganglion cell axons cross brain hemisphere

nasal

portion of visual field closest to nose that crosses at the optic chiasm

temporal

portion of visual field closest to ear whose retinal ganglion axons stay ipsilateral

melanopsin

photopigment crucial for circadian rhythms, why circadian rhythm is sensitive to blue light

superior colliculus

brain region that coordinates head and eye movements to visual target; also axial musculature in the neck

pupillary light reflex

both pupils respond to monocular visual stimulation; retinal ganglion cells → pretectum → EWN (midbrain) → oculomotor nerve → ciliary ganglion → constrictor muscles of the iris

saccadic eye movement

ballistic eye movement occuring when focusing

smooth pursuit eye movement

following stimuli w/ eye

optokinetic reflex

gaze stabilization reflex combining both saccadic and smooth pursuit eye movements

primary visual pathway

retinal ganglion → LGN (of thalamus) → V1