neur200 exam 2

Charles Scott Sherrington

-Studied simplest, reflex, 2 neurons

-Synaptic delay - found there was delay in message

-observed speed of conduction thru reflex arc was never more than 15 m/s

-first to introduce the term synapse

AP along sensory or motor axons are about ___

40 m/s (10 to 100 m/s)

electrical synapses

some neurons only communicate through electrical, parts of brain important for fast and accurate over complexity, these neurons almost touch each other

graded potential

Unlike AP, graded pot can be either depolarization (excitatory) or hyperpolarization (inhibitory)

IPSP or EPSP

excitatory postsynaptic potential (EPSP)

temp graded depolarization of postsynaptic membrane

-Caused by entranced Na ions into cell

-Make cell more likely to fire AP, but not reach the threshold

inhibitory postsynaptic potential (IPSP)

temp graded hyperpolarization of postsynaptic membrane

-Exit K out of cell or chloride ions (- charges) inside, increasing - charge within neuron

-less likely to make neuron fire

spatial summation

synaptic inputs from separate locations combine their effects on a neuron

-summation over space

-Importance of timing (timing=communication)

temporal summation

Repeated stimuli within brief time have a cumulative effect

-Even though threshold in postsynaptic neuron decays over time, it can combine with a second excitation. When combination exceeds threshold, AP

*Temporal and spatial summation can occur simultaneously

spontaneous firing rate

Periodic production of AP even without synaptic input

-Ongoing activity in absence of task or stimulation

-Ongoing brain activity important for perception. Perception of weak stimulus will depend on both phase and amplitude of spontaneous activity - study

-EPSPs increase freq of AP above spontaneous rate, whereas IPSPs decrease it

-Can change within an individual due to Ca channels, genes, etc (affected by age, illness, development)

-Higher spontaneous firing rate = more conscious, more aware

neural synchronization

Brain waves from diff regions synchronize (network communication), Important for cognition

-Want our neurons to communicate, you don't wake up and work alone nocturnally

-Synchronized activity of neurons can give rise to oscillations

in response to AP, ___ channels open

Ca2+ channels open in axon terminal, Ca2+ ions enter triggering proteins (SNAREs) causing exocytosis

exocytosis

presynaptic axon terminals contain vesicles (little hollows) that contain neurotransmitters, vesicles fuse with membrane and neurotransmitters are released in synaptic cleft

Effects of neurotransmitters in postsynaptic neuron - Types of receptors

ionotropic and metabotropic

Ionotropic effects

vision and hearing - neurotransmitter binds to ionotropic receptor and opens its channels (Na, K, Ca, Cl)

-Fast effects < millisecond

Metabotropic effects

pain, attention, pain, mood, emotion - initiate metabolic reaction. Second messenger communicates to many areas within cell

-Slower effect > 30ms or more

-longer lasting (few sec) than ionotropic

dopamine

neurotransmitter influencing movement, learning, attention, and emotion

-anything addictive!

Dopaminergic

increases dopamine in brain, common denominator for drug use

Monoamines

modified amino acids

-Dopamine

-serotonin

-norepinephrine

5 dopamine receptors

D1-D5

-D1 - cortical/frontal control

-Movement - Parkinsonism

-Reward, motivation, cognitive control - ADHD

-Psychosis - hallucinations

Dopaminergic drugs

antipsychotics, stimulants, recreational drugs

antidepressants target ___

serotonin: dopamine issue means patient would feel worse

dopamine levels are higher in ___

girls than boys, girls more likely to pay attention, more susceptible to depression

pathway

a course through which electricity can flow, neurotransmitter follows path

3 dominergic pathways in the brain

mesocortical - VTA > PFC (delayed gratification)

mesolimbic - VTA > NAc (reward pathway)

nigrostriatal SN > BG-s

VTA

main synthesizers of dopamine in brain

NAc

nucleus accumbens, important for mood, drug use disorders

mesocortical vs mesolimbic examples

Mesocortical allows frontal to say no to phone, in the long run, cognitive control

-Mesolimbic would be endless scrolling, immediate reward

nigrostriatal

important for movement (in Parkinsons)

-SN neurons dying in Parkinsons

-Treatments target melanin

-Darker skin less susceptible to Parkinsons

norepinephrine =

noradrenaline

norepinephrine

(alpha and beta receptors)

-Autonomic responses (heart rate)

-Main synthesizer in brain: locus coeruleus

-PNS: adrenal cortex

-Energy, arousal, mood (depression and anxiety)

-works at level of brain and body

adrenaline

hormone released into the bloodstream in response to physical or mental stress

hormones reach ___

diff areas of body, not only brain

Chemicals that send messages within brain

those messages read short distances within brain

glutamate as a neurotransmitter

simple, yes or no message

dopamine as a neurotransmitter

metabolic tropic, 1st messenger - neurotransmitter, 2nd messenger - another neurotransmitter brings message to diff parts of neuron

-Nicotine releases dopamine, one of most addictive

-norepinephrine/noradrenaline increases follow similar pattern to dopamine

Wellbutrin

antidepressant that increases dopamine

serotonin

neurotransmitter affecting arousal, hunger

-Main synthesizer: raphe nuclei

-Sleep and wakefulness

-Mood (depression)

-Serotonin is highest when animals are awake

-~13 receptors, many functions

drugs affecting serotonin

SSRIs (serotonin reuptake inhibitors ex: prozac)

-TCAs

-MAOI

Neurotransmitters recycled in postsynaptic neuron, broken down or taken back by presynaptic neuron

-Manipulate social behaviors of monkeys by injecting prozac, lower became alpha male

Brain uses serotonin to create ___

melatonin

-aggression, satisfaction, contentment, stop caring about things and lack of empathy

-Very aggressive mice with MAO gene, more serotonin

-Blocked serotonin, less effect = nice sniff mice

glutamate

most important excitatory neurotransmitter. Receptors are AMPA and NMDA. psychosis. Excitotoxicity (Na)

GABA (receptors: GABAa b and c)

Inhibitory postsynaptic potentials. Influx of chloride Cl- (similar to alcohol)

Drugs: benzodiazepines

Acetylcholine

decreases with age

-Nicotinic and muscarinic receptors - neuromuscular junction, memory/attention

-Nucleus basalis of Meynert - close to hippocampus and amygdala

-Muscles

-Memory and attention (Alzheimer's disease)

Maturation of vertebrate brain - Processes in the development of neurons

proliferation, migration, differentiation, myelination, synaptogenesis

proliferation

production of new cells. 28 weeks of gestation (beginning of life, before birth) if baby born before 28 weeks, proliferation stops, only in womb

Overproliferation

megalencephaly

Reduced proliferation

microencephaly

migration

chemicals guide neuron migration until adulthood

-Deficit in chemicals lead to decreased brain size, decreased axon growth

-Environmental factors during pregnancy can contribute to infection, low maternal BMI

differentiation

cell changes into specialized type of neuron. Axon and dendrites formed. Axons grow first, dendrites form after migration, when neurons reach their destination

myelination

continues gradually through adolescence and adulthood

-Impaired adult myelination in prefrontal cortex of socially isolated mice

synaptogenesis

neurons form new synapses and discard old ones. Process slows in older people

synaptic pruning

brain removes unnecessary synapses and strengthens the remaining ones

-Too little pruning in autistic patients, always overwhelmed

-Alzheimer's and schizo too much pruning = cog decline

-Hyperconnectivity: too many connections, as a baby

-The more a pathway is used, the more it is strengthened

___ is one of the best ways to maintain intellectual vigor in old age

physical activity - aerobic exercise - enhances both cognitive processes and brain anatomy

-Stimulating environment enhances sprouting axons and dendrites in many species

Prolonged experience of a particular type enhances brain's ability to perform same function again, specifically if it starts in childhood

-Blind ppl use occipital cortex to help identify what they feel

-Practicing music reorganized brain to maximize performance and skill

spinal cord: reflexes

-Communicates with sense organs and muscles

-Each segment of the spinal cord sends sensory information to the brain and receives motor commands from the brain

Hindbrain: postural support

Disconnection of hindbrain from rest of brain: vegetative state

-Consciousness affected

Midbrain: spontaneous movement

Important for operant movements (attack, get food) reaction to a stimulus (not motivated behavior)

*Superior (vision) and inferior colliculus (hearing): animal can perceive events and respond to them (attack response to moving objects) spontaneous movement

-Includes substantia nigra - dopamine synthesizer

thalamus

relay station for sensory information, before cortex

-Hearing the projector in the background, even tho unconscious of it

Diencephalon: motivation

Hypothalamus: motivated behaviors (sleep, eating, sex, thermoregulation)

Pituitary gland: hormones

Basal ganglia: self-maintenance

Learn simple sequences of movements (grooming, copulation, drive car, ride bike) muscle memory

-Animals learn to feed themselves

-Behaviors are biologically adaptive

***Animals can learn without cortex (conditioning)

Cortex: intention

Animal is more proactive

-Skilled movements and sequences (language)

-Cortex allows us to extend usefulness of learned behaviors to new situations

Solve new problems and make plans

cortical organization

Layers: input and output

Cortical columns: interaction (function)

columns/modules

most interactions bet neurons take place vertically. Less interaction takes place with cells more than a couple of mm on either side

-Neurons WITHIN column interact more vertically than horizontally

-Ocular dominance columns are arranged alternately across visual cortex

-FUNCTIONALLY similar within column (excited by a particular tactile stimulus in a particular part of the body)

-Modules are apparent in primary sensory regions and less apparent in association or motor areas of the cortex

-Can see without microscope at times

-Columns in primary auditory cortex - process sounds - activate diff columns in cortex (some for re, some activate mi)

cortical layers

Middle cortical layers: input zone of sensory analysis (sensory areas have larger layer IV)

Layers V and VI: output zone: send axons to other cortical and brain areas. Motor areas has large layer V and small layer IV

Superficial layers II III: receive inputs from other cortical areas and integrate them with inputs from layer IV

-Layers V and VI bigger in primary motor cortex bc output neurons

-IV smaller in motor bc contain neurons for input (almost disappears)

*Frontal is output, other lobes input

which layer is bigger in parietal lobes?

IV or V ... IV bc sensory

*Frontal is output, other lobes input

Nobel Prize Hubel and Wiesel

noticed columns in occipital lobe

-Ex: ocular dominance columns in area 17 of visual cortex

-Every angle activates diff columns

-Vertical vs horizontal vs any other lines

-Kitten only exposed to horizontal

Sensory system: vision

Types of energy and transduction

-Each type of receptor is specialized on a specific type of energy

Vision: light

Audition: pressure changes in air

Touch: pressure changes in skin

Smell and taste: chemicals

transduction

receptors transform energy on a diff type of energy (electrical energy) transduction occurs in the receptors

visual receptors

Retina: neural tissue that receives light

-Fovea (cone receptors): small area specialized for acute, detailed vision

-Periphery (rod receptors): better sensitivity to dim light than fovea (stars)

each eye has 2 pathways

Diff colors indicate diff pathways

-Ipsilateral - same side

-Contralateral - opposite side

visual pathways

-Geniculostriate pathway: pattern, color, motion recognition (Primary visual cortex/striate cortex/V1)

-Tectopulvinar pathway (tectum in midbrain: superior colliculus, thalamus pulvinar nucleus and parietal lobe)

Spatial location of objects. Unconscious (automatic)

*vision in other lobes other than occipital (temporal, etc)

occipital lobe

V1 striate cortex and V2: functionally heterogeneous areas

More specific functions of areas in occipital cortex

-V4: important for color vision. Damage to this area results in loss of color cognition

-V5 (MT - middle temporal): important to perceive objects in motion. Damage to this area objects at rest are perceived, but when objects begin to move, they vanish

*if only in one, then the other can compensate

occipital - Signals from striate cortex (V1) travel to a # of other places in the cortex for further processing

-Ventral stream (what pathway): toward temporal cortex (inferior temporal gyrus). Determine an object's identity

-Dorsal stream (where/how pathway): toward parietal cortex. Determine an object's location. Info about how to direct action with regard to a stimulus. Ex: neglect

agnosia

issues recognizing objects

Ex: prosopagnosia - impairment of facial recognition

ventral stream areas

Fusiform face area (FFA): face analysis

Extrastriate body area (EBA): body analysis (just parts)

Superior temporal sulcus (STS): biological motion (body movement analysis)

Parahippocampal place area (PPA): scenes: indoor/outdoor/landmarks

serial processing

computes info step-by-step in a methodical and linear matter, areas work on one after another

parallel processing

processing of many aspects of a problem simultaneously, areas work at same time

dorsal stream regions

Parietal reach region: visually guided reach