Behavioral Neuro Exam 1

behavioral neuroscience

how behavior relates to bodily processes to understand behavior in terms of its biological substrates

conservation

continuity of certain behavioral & biological characteristics across various species

ex. nerve impulse same from jellyfish to humans

species-species behaviors

specially evolved characteristics that help a particular species survive in a given environment

reductionism

to understand a whole concept, break it down into smaller pieces

Levels of Analysis (in reductionism)

1. social level - individuals behaving in social interactions

2. organ level - brain, SC, peripheral nerves, and eyes

3. Neural systems level - eyes and visual brain regions

4. Brain region level - visual cortex

5. Circuit level - local neural circuit

6. Cellular level - single neuron

7. synaptic level - releasing NT

8. Molecular level - membrane receptors

neuron doctrine

Established by Santiago Ramon y Cajal

1. brain is composed of separate neurons & other cells that are independent structurally, metabolically, and functionally

2. information is transmitter from cell to cell across tiny gaps called synapses

soma

• cell body

• houses nucleus (genetic material)

dendrites

input zone of neuron

axon

allows electrical signal to travel down neuron

axon hillock

• between soma & axon

• place of AP generation

myelin sheath

fatty covering that wraps axons & protects them

axon terminals

• synaptic button

• where NTs are stores and where they communicate with other neurons

synapse

junction between axon terminal and membrane of other neuron

somatic NS division of the PNS

controls voluntary movement of muscles

autonomic NS of the PNS

unconscious control & vegetative functions

sympathetic NS division of the ANS

fight or flight

parasympathetic NS division of the ANS

relaxes the NS to restore lost E from triggered sympathetic NS

glial cells

• AKA neuroglia

• supporting cells of the CNS

astrocyte

• provide support to neurons of the CNS

• nutrients, regulating chemical composition, cleanup, injury repair

• middle point between local blood cells and neuron

oligodendrocytes

form myelin sheath in the CNS

microglia

• smallest glial cells

• act as phagocytes and protect the brain fro invading microorganisms

Schwann cells

• in PNS

• wrapped around myelinated axons providing one segment of its myelin sheath

blood brain barrier

• semipermeable barrier between the blood and the brain produced by cells in the walls of the brain’s capillaries

• help CNS maintain proper composition in/out of neurons

brain blood supply

• basilar artery

• carotid artery

• verterbral arteries

basilar arteries

formed where the right and left vertebral arteries join thgether at the lower border of the pons

carotid artery

• left & right side of the neck

• branch into external and internal

• internal branch enters skull and forms the main anterior and middle cerebral arteries

vertebral arteries

• ascend the vertebrae and enters the base of the skull

• fuse to form the vertebral artery

• supply blood to brain stem and posterior cerebral hemispheres

Circle of WIllis

joining of the basilar and carotid arteries at the base of the brain

ventricles

• “little bellies”

• 4 hollow spaces located in the brain that produce CSF

lateral ventricles

• 2 ventricles located in center of telencephalon

• surround thalamus

third ventricle

located in the center of the diencephalon

cerebral aqueduct

narrow tube interconnecting 3rd & 4th ventricles of the brain

fourth ventricle

between cerebellum & dorsal pons in the center of the mentencephalon

choroid plexus

highly vascular tissue that protrudes into ventricles & produces CSF

frontal lobe

executive functions:

• decision making

• planning

• impulse control

parietal lobe

attention & sensory integration

occipital lobe

vision

temporal lobe

cognitive functions:

• object-recognition

• facial recognition

• language

central sulcus

deep groove in cerebral cortex that separates frontal & parietal lobe

corpus callosum

connects hemispheres

pons

• attentional awareness & arousal systems

• have NT that modulate brain activity

ex. dopamine & serotonin

medulla

• responsible for vegitative states/things that keep us alive

• damage: causes vegitative state where vital survival functions need external support to survive

cerebellum

• “small brain”

• learning motor skills, cognitive skills, coordination, balance & posture

cingulate gyrus (limbic cortex)

• governs limbic system

• physiological states (ex. hunger, emotions, etc.)

• wraps corpus callosum

hippocampus

• spatial recognition (“internal map”)

• memory (short term —> long term; facts places, autobiographical)

• encodes new information

amygdala

• “almond-shaped”

• regulates emotions & stress response

• sexual arousal

mamillary bodies

• memory & emotion (relay station)

• relay station in reflexes related to sense of smell

• protrusion at bottom of brain/posterior end of hypothalamus

olfactory bulb

• transmits smell information directly to the cingulate cortex and straight into the brain

• tightly associated to amygdala & hippocampus (memory)

thalamus

• densely packed group of nuclei

• relays information: sensory information into a synapse then part of the brain

• directs motor function

Parts of Basal Ganglia

• caudate nucleus

• globulus pallidus

• putamen

• substantia nigra

basal ganglia

• gatekeeper of movement

• checks & balances of emotions & cognition (decides whether emotion should be expressed or not)

substantia nigra

• “black substance”

• dopamine nucleus that projects dopamine up into the basal ganglia

Cranial Nerves

I - olfactory

II - optic

(III,IV, VI) - oculomotor, trochlear, abducens

VII - facial

VIII - vestibulocochlear

X - vagus

Ionic Basis of Resting Potential

1. Na+/K+ pump uses ATP to move 3 Na+ out / 2 K+ in

• High Na+ concentration outside, high K+ concentration inside

2. K+ wants to leave the cell (diffusion)

• K+ leak channels want to go where K+ is lower concentration

• inside of the cell becomes negative as K+ leaves

3. Negative electrical force inside pulls K+ back in

• electrical gradient - opposites attract (cell is negative inside, K+ is positive, they are attracted to each other)

4. Electrical force and concentration force balance each other out to resting potential

Ionic Basis of Action Potentials

1. Stimulus received

2. Some Na+ come in & excite gated voltage channels (depolarization)

• opens Na+ ion channels

3. K+ leak channel always open, K+ leaves the cell

4. Na+ channels become refractory at the peak

5. K+ continues to leave (reaches resting periodically —> repolarization)

6. K+ channels close, Na+ voltage-gated channels reset

7. Extra K+ diffuses out (hyperpolarization)

depolarization

Na+ channels open, inside of the cell becomes more positive

hyperpolarization

voltage gated K+ channels do not close instantly, so too much K+ leaves and the membrane potential passes RMP (-90 mV)

inhibitory postsynaptic potential (IPSP)

makes neuron less likely to fire an action potential

• NT released from presynaptic neuron

• NT binds to receptor on postsynaptic membrane

• opens ion channels

- Cl- enters OR K+ leaves (to make inside of cell more negative)

• inside becomes more negative (hyperpolarization)

• neuron is farther from threshold

excitatory postsynaptic potential (EPSP)

makes neuron more likely to fire action potential

• action potential reaches presynaptic terminal

• Ca2+ enters presynaptic terminal

• NT released into synaptic cleft

• NT binds to receptors on postsynaptic membrane

- opens ion channels and allows Na+ to enter

• membrane becomes less negative (depolarization)

• neuron is closer to threshold of excitation (-55 mV)

ionotropic receptor

• binds to ligand-gated channels to let Na+ in

• faster than metabotropic but short lived; direct

• receptor is itself an ion channel

• NT —> receptor —> channel opens —> ions move

metabotropic receptor

• changes chemistry of protein & therefore changes function; slower, last longer; indirect

• attracts 2nd messengers (G-protein) - utilized as signaling molecule to open channels

• Receptor —> G-protein —> signaling pathway —> effect

3 subunits of G protein

alpha, beta, gamma

alpha subunit

• associated with GDP/GTP

• when activated, GDP is replaced by GTP

• separates from beta & gamma subunits

• can affect ion channels or other signaling proteins

beta + gamma subunits

• stay together as beta gamma complex

• NT —> metabotropic receptor —> G-protein activated —> GDP —> GPT —> alpha separates from beta + gamma —> signaling —> cellular response

2nd messengers

molecules inside cell that carry/continue the signal after a receptor is activated

ex. cAMP, Ca2+, IP3, DAG

saltatory conduction

• myelinated axon

• AP jumps between myelin to Nodes of Ranvier

- myelin insulates the axon

- voltage-gated Na+ channels concentrated at Nodes of Ranvier

- AP occurs at one node

- current travels rapidly underneath myelin & reaches next node

- threshold of excitation happens, new AP formed

- process repeats

continuous conduction

• unmyelinated axon

• AP occurs in 1 section

• slow conduction, no jumping

axon hillock

• where neuron generates AP

• high concentration of voltage-gated Na+ channels

• EPSPs & IPSPs arrive at neuron —> signals are integrated —> axon hillock —> if threshold is reached —> AP

summation

• neuron can receive EPSPs & IPSPs at the same time; neurons add them together

• 2 types: temporal & spatial

temporal summation

1 presynaptic neuron fires repeatedly in a short period

spatial summation

multiple presynaptic neurons fire at the same time

Process of Synaptic Neurotransmission

1. AP travels down axon —> axon terminal

2. depolarization causes voltage-gated Ca2+ channels to open

3. Ca2+ moves into presynaptic terminal

4. Ca2+ triggers synaptic vesicles with neurotransmitters to move forward & fuse with presynaptic membrane

5. NT released into synaptic cleft through exocytosis

6. NT crosses cleft and binds to receptors on postsynaptic membrane

7. Postsynaptic response: Ionotropic or Metabotropic

• IPSPs: influx of Cl- or efflux of K+

• EPSPs: influx of Na+

3 Removals of NTs from synaptic cleft

• re uptake - transported back into presynaptic neuron

• degredation - enzymes break down NTs

• diffusion - diffuse away from the synaptic cleft

acetylcholine

• primary NT secreted by efferent axons of the CNS

• controls muscular movement, regulates REM sleep, cognition, perceptual learning, memory

• Disease: Alzheimer’s

Monoamines

catecholamines & indolamines

catecholamine 3 types

dopamine, norepinephrine, epinephrine

dopaminergic pathway

• nigrostriatal system

• mesolimbic system

nigrostriatal system

• system of neurons originating in substantia nigra and terminating in the neostriatum (caudate nucleus + putamen of basal ganglia)

• role in movement

mesolimbic system

• starts in the ventral tegmental area in the midbrain that provides dopamine to the rest of the brain

- ventral tegmental area - mesolimbic + mesocortical = mesolimbocortical on pons

- pons - housing of NT systems that regulate brain functions

dopamine

regulates pleasure, movement, motivation

norepinephrine

• AKA noradrenaline

• NT found in brain and sympathetic NS

epinephrine

• AKA adrenaline

• hormone secreted by adrenal medulla; serves as NT in the brain

serotonin

• indolamine

• role in mood, eating, sleep, dreaming, arousal, pain

• works alongside norepi, dopamine & acetylcholine

tryptophan

amino acid that is the precursor of serotonin

Raphe nuclei

• synonymous with serotonin

• several subnuclei in the pons of the midbrain

• medulla broadcasts serotonin around the brain

cortex —> mesencephallic

Serotonin Drugs

• Fluoxetine (Prozac) - for anxiety, depression, OCD

• Fenfluramine - stimulates the release of serotonin & suppresses appetite

• LSD - acts on 5-HT2A distort visual perception

• MDMA - ecstacy; noradrenergic and serotonergic agonist

amino acid NTs 2 types

glutamate & GABA

glutamate

• most important excitatory NT in the brain

• heavily involved in synapses

• 2 receptors: NDMA & AMPA

NMDA

specialized ionotropic glutamate receptor that controls calcium channel that is blocked by Mg2+ ions

AMPA

• ionotropic glutamate receptor that controls sodium channel

• most common receptor

GABA

• major inhibitory NT

• made directly from glutamate

• multiple binding sites

- benzodiasepine site - binding here keeps Cl- channel open longer

GABA Drugs

• benzodiazepines - indirect agonist for GABA receptor

• barbituate

• strychnine - direct agonist for glycine receptor causes convulsions & death in small doses

locus coeruleus

• located in the pons

• projects widely throughout the brain

• associated with vigilance & attention

affinity

how readily 2 molecules bind together

dose response curve

plots magnitude of effect with amount of drug administered

saturating dose

• produces toxic effect

• TD50 = dose that produces toxic effect in 50% of population

effective doses

• ED50

• good starting point for prescribing a drug (50% of desired response is produced

• has to be fairly low, means drug is safer

agonist

• drug that facilitates/increases effects of NTs

• 2 types: direct & indirect

direct agonist

binds to receptor and activates it

indirect agonist

facilitates receptor/NTs action