neuro midterm 2

photons

particles of light that are captured by the eye. frequency at which a photon oscillates = color we perceive

cornea

anterior, front-most part of the eye. cornea refracts/bends incoming rays of light to converge at retina

pupil

the adjustable opening in the center of the eye through which light enters. less light = pupil dilates, more light = pupil constricts

lens

• the transparent structure behind the pupil that changes shape to help focus images on the retina.

• shaped like a camera lense -> convex on both sides (biconvex)

accommodation

the process by which the eye's lens changes shape to focus near or far objects on the retina. due to ciliary muscle surrounding the lens

visual field

area of the world that an individual can see withou moving your eyes (ex. left half of vision = left visual field)

extraocular muscles

7 muscles around that enable us to move our eyes very rapidly and accurately and keep the eyes always pointed in the same direction

retina

Light sensitive layer in the back of the eye; contains rods and cones

fovea

the pit in the retina with highest acuity/clearest vision; around which the eye's cones cluster and rods are scarce

optic disk

A hole in the retina where the optic nerve fibers exit the eye. no photoreceptors = blind spot

optic nerve

• the nerve that carries neural impulses from the eye to the brain

• "paired" = one on each half of the body

• also known as cranial nerve II

phototransduction

conversion of light energy into neural impulses that the brain can understand through the use of photoreceptor cells

photopigments

chemicals in the outer segment of photoreceptors that respond to light and assist in converting light into neural activity

rods

• retinal receptors that detect black, white, and gray --> scotopic vision

• necessary for peripheral and twilight vision

• high synaptic convergence

• contain rhodopsin proteins

synpatic convergence

several rod cells feed into a single downstream route of communication. able to add many signals together to create a seemingly larger signal -> helpful at night

cones

• allow for high-acuity vision aka clear vision

• most densely packed at fovea

• low synpatic convergence = less cone cells in retina

• process our sensation of color (short wavelength = violet, medium wavelength = green, long wavelength = red)

duplicity theory of vision

a theory which holds that the retina contains two types of specialized photoreceptors: rods and cones. they are used simultaneously and complement each other

opsin

a class of protein that, together with retinal, constitutes the photopigments; opsin = structure of transmembrane protein

retinal

a chemical synthesized from vitamin A; joins with an opsin to form a photopigment/ light sensitive gate in rods

Amacrine cells

Specialized retinal cells that contact both the bipolar cells and the ganglion cells, and are especially significant in inhibitory interactions within the retina.

retinal ganglion cells

the third layer of retinal neurons whose axons leave the eyeball and form the optic nerve.

Optic chiasm

the point at which the optic nerves from the inside half of each eye cross over and then project to the opposite half of the brain.

• visual info from the temporal side of the eye stays ipsilateral in brain

Primary Visual Cortex (V1)

the region of the occipital cortex where most visual information first arrives. has a distincitive stripe caused by myelinated axons arriving from the thalamus

Dorsal stream of vision

"where pathway"; processing the object's spatial location relative to the viewer

Ventral stream of vision

"what pathway"; object recognition and form representation

Fusiform Face Area (FFA)

an area in the temporal lobe that contains many neurons that respond selectively to faces; in ventral stream of vision

Intraveous Injection (IV)

• fastest route of administration, effects delivered within seconds

• delivers drug directly into blood stream

• important for acting fast (ex. narcan)

• no dilution aka the dosage delivered = dosage experienced

Inhalation of drugs

• rapid route of administration; effects delivered in seconds

  • inhalation = going into lungs like smoking, vaping, etc

  • can cause hypoxia (low blood levels of oxygen causing permanent brain damage)

insufflation

drug enters blood stream through snorting up the nostrils; common with cocaine -> rapid drug effects

Transdermal drugs

• Medicated patch that is placed in skin to deliver specific dose of medicine on through skin to bloodstream

• avoids processing by digestive tract

• slowest route of administration (hours)

ventral tegmental area (VTA)

midbrain structure where dopamine is produced: associated with mood, reward, and addiction

mesolimbic pathway

reward pathway where VTA dopamine -> nucleus accumbens, amygdala, prefrontal cortex, hippocampus

Nucleus Accumbens (NAc)

a nucleus of the basal forebrain; receives dopamine-secreting axons from the ventral tegmental area and is thought to be involved in reinforcement and attention

mesocortical pathway

VTA to prefrontal cortex

Prefrontal Cortex (PFC)

• involved in conscious decision making and inhibitation of actions

• in frontal lobe

• changes in dopamine projections into PFC explains poor decision making/loss of inhibition when on drugs

dose-response curve

a graph of the magnitude of an effect of a drug as a function of the amount of drug administered

agonists

• drugs which mimic the activity of neurotransmitters -> either activating ionotropic or metabotropic receptors

• bind on active/orthosteric site

dirty drugs

Drugs that can bind to a multitude of receptors and thus have unperceived and potentially detrimental side-effects.

full agonist

Ability of a drug to produce 100% of the maximum response regardless of the potency

partial agonist

substances that can activate the receptor by binding to the orthosteric site, but are unable to fully activate the receptor, even at higher dosages (commonly used by anxiety, psychosis, and chronic pain)

antagonists

Chemical substances that block or reduce a cell's response to the action of other chemicals or neurotransmitters.

competitive antagonists

bind to orthosteric site, compete with agonists (ex. narcan)

allosteric modulators

• bind reversibly to a protein at a regulatory site away from the binding site, and by doing so change the shape of the binding site

• can increase action of agonist (positive) or decrease action (negative)

• ex. barbituated and benzodiazepines

psychoactive substances

chemicals that act on the nervous system to induce a change in behavior or mindstate (ex. alcohol, cocaine, etc.)

alcohol

• most widely used drug

• made of ethanol - byproduct of yeast

• easy to diffuse through cell membranes = quick drug effects

• depressant effect on neurons

Nicotine

• made of tobacco plant

• agonist at nicotine acetylcholine receptors (nAChRs) -> exictatory ionotropic receptors

• stimulant -> induces release of norepinephrine & activates sympathetic NS

Cannabis

• derived from cannabis plant

• effects within minutes when smoking/inhaling

• can cause sense of euphoria, relaxation, distortion of perception, etc.

Opioids

• includes opium, heroin, morphine, fentanyl

• derived from poppy plant

• increases endorphins which dampens the sensation of pain

Cocaine

• dervied from coca plant

• stimulant by inhibiting reuptake transporter proteins from clearing dopamine, norepinephrine, and seratonin out of synapse

• common routes of admin. = insufflation, inhalation, injection

• powerful sympathomimetic -> substance activates the sympathetic NS aka fight or flight

Psychedelics

• cause visual distortions, synesthesia, altered sense of self, etc.

• chemically similar to serotonin -> activates seratonin receptors

Tolerance

a decrease in the effectiveness of a drug that is administered repeatedly; rightward shift in dose response curve

metabolic tolerance

decrease in the amount of the drug that gets to the site of action bc the body becomes more efficient at eliminating the substance. increase in # of enxymes = decrease in substance capable of acting

functional tolerance

decrease in receptor expression after chronic exposure to an agonist

conditional tolerance

Tolerance only expressed in environment associated with drug

sensitization

"reverse tolerance"; chronic exposure leads to an increase in drug effect. common in nicotine, cocaine, amphetamine, etc.

withdrawal

the discomfort and distress that follow discontinuing the use of an addictive drug

drug dependence

when a person needs a drug in order to function either physically or by craving the drug so bad

self-administration experiment

subject with a surgical implantation of a pump is left to pump more drugs into their brain. subject will continue to give itself drugs even with adverse reactions.

hedonia hypothesis

• dependent on dopamine being the "pleasure neurotransmitter"

incentive sensitization model

• instead of "liking" the drug, the user fixates on "Wanting" the drug

polysomnogram

the recording of different physiological changes during sleep (a.k.a. sleep study) like HR, BP, oxygen levles, eye movement, brain activity (use of EEG), etc.

Rapid Eye Movement (REM)

stage of sleep in which the eyes move rapidly under the eyelids and the person is typically experiencing a dream; "paradoxical sleep" -> brain activity similar to being awake

NREM1

light sleep/relaxed wakefulness, slowing heart rate, beta waves (awake) -> alpha waves (drowsy) -> theta waves (NREM1 light sleep)

NREM2

Relax more deeply; theta waves with sleep spindles and K-complexes, rhythmic brain wave activity; 50% of sleep spent here

Sleep spindle

rapid burst of high frequency brain waves during stage 2 sleep that may be important for learning and memory

K-complexes

periods of very large wave amplitude (can be response to sound); during Stage 2 sleep

NREM3

deep sleep, delta waves (low frequency), physiological activty drogs to lowest point (HR, respiration, BP reach minimum).

hypnogram

A graphic depiction of a person's progress through the stages of sleep over the course of a night

Recuperation Theory

• Sleep is needed to restore homeostasis

• supporting argument: sleep deprivation effects (ex. Peter Tripp)

• enhanced metabolic cleaning during sleep thru gylmphatic system

• immune system function improved with sleep

• increased production of growth hormone during deep sleep

evolutionary adaptation theory

animals have adapted to benefit the animal's survival (ex. dolphins sleeping only half their brain or cows sleeping standing up)

Brain plasticity theory

• sleep allows for children/adults to learn and perform tasks

• brain activity during sleep helps move memories into long-term storage

• ex. newborns sleep 17 hrs a day bc a bunch of learning

circadian rhythm

the biological clock; regular bodily rhythms (for example, temperature and wakefulness) that occur on a 24-hour cycle

entrainable

circadian rhythm responds to environmental cues like sunlight (Zeitgebers) or social cues like people being around you to stay synchronized with the environment

Adenosine

as body uses cellular energy throughout the day, there is an increase in adenosine -> causes sleepiness. Caffeine is adenosine receptor antagonist

Melatonin

A hormone manufactured by the pineal gland that produces sleepiness. Production is heavily dependent on exposure to sunlight/blue light

Suprachiasmatic nucleus (SCN)

a pair of cell clusters in the hypothalamus that controls circadian rhythm. In response to light, the SCN causes the pineal gland to adjust melatonin production, thus modifying our feelings of sleepiness (more light = less melatonin = less sleepy)

Histamine

neurotransmitter that acts as a pro-wakefulness signal (ex. ANTIhistamines make you drowsy)

hypothalamus

• histmaine is produced by hypothalamus (tuberomammillary nucleus)

• SCN found in hypothalamus

• anterior hypothalamus = promotes sleep

• posterior hypothalamus = promotes wakefulness

Reticular formation

• structure within brainstem

• Controls several functions related to sleep: Consciousness, REM sleep, Muscle relaxation, Cardiorespiratory changes

Insomnia

Difficulty in falling asleep or staying asleep; causes change in daytime behavior (ex. mood/personality)

• can be due to anxiety, stress, age, lifestyle, etc.

Onset insomnia

difficulty with initially falling asleep

maintenance insomnia

insomnia in which the individual cannot stay asleep during the night

Fatal Familial Insomnia (FFI)

• incurable and deadly insomnia

• genetic component that leads to damage to thalamus and mishaped proteins called prions

Sleep apnea

a disorder in which the person stops breathing for brief periods while asleep and causes them to wake; usually due to obesity and/or age; treated with CPAP machine

Narcolepsy

A sleep disorder characterized by uncontrollable sleep attacks. The sufferer may lapse directly into REM sleep, often at inopportune times. Due to dysregulation of orexin production by lateral hypothalamus

Cataplexy (narcolepsy)

A sudden loss of voluntary muscle strength and control with a sleep attack that is usually triggered by an intense emotion.

Frequency

• the number of complete wavelengths that pass a point in a given time

• higher frequency = higher pitch

Amplitude

• Height of a wave

• larger amplitude = louder the sound

• prolonged exposure to high amplitude (loud) sounds can lead to permenant damage to auditory systems

Timbre

• the complexity of the wave form

• different instruments cause different wave forms even in the same note

• overtones: high frequency components that overlap a normal wave

Ear Drum/Tympanic Membrane

a thin membrane in the middle ear that vibrates as the sound wave hits it at the same frequency

bony ossicles

three bones in middle ear that deliver sound waves and controls movement of eardrum; helps to amplify the sound

cochlea

a coiled, bony, fluid-filled tube in the inner ear; sound waves traveling through the cochlear fluid trigger nerve impulses

Endolymph

fluid within the labyrinth of the inner ear; high in K+, low Na+ solution similar to CSF

hair cells in ear

• primary sensory neurons that interpret physical movement

• contain cilia that moves in response to movement of lymph -> causes K+ channels to open -> causes depolarization -> neurotransmitter release

tonotopical organization

adjacent physical areas are responsible for conveying information from adjacent frequencies. ex. hair cells that respond most to 440 Hz vibrations are right next to to cells that respond maximally to 441 Hz

saccule and utricle

Fluid-filled sacs of the vestibular organ that inform the brain about the body's orientation.

otoliths

small calcium carbonate crystals in the fluid-filled vestibular sacs of the inner ear that, when shifted by gravity, stimulate cilia -> stimulate nerve cells that inform the brain of the position of the head

semicircular canals

• three fluid-filled canals in the inner ear responsible for our sense of balance in all directions

• hair cells in the end of the canals (cupula) move in response to movement of fluid caused by change in head position

• opposite movement of cilia = de- vs hyperpolarization

olfaction

sense of smell

olfactory receptor neurons

• sensory receptor (bipolar) cells that convert chemical signals from odorants into neural impulses that travel to the brain.

• dendrities project into epithelium of nasal cavity (on nerves exposed to environment) -> neurogenesis occurs