NSCI 1001: Exam 1

neuron

fundamental building blocks of nervous system

glial cells

also comprise nervous system, 1:10 ratio with neurons

brain circut

nuclei communicating with each other

brain nucleus

collection of neurons

grey matter

cell bodies ie cerebrum

white matter

axons traveling to different regions

importance of stains

the brain is opaque, so stains are needed to identify anatomy

goals of neuroanatomy

1. region specificity

2. connectivity

3. function in human and animal studies

4. comparative neuroanatomy

region specificity

distinctions between and within regions

connectivity

• anterograde: tracing IN direction of info flow (body to axon term.)

• retrograde: tracing in REVERSE of info flow (axon term. to cell body)

function: human studies

led to the identification of Broca and Wernicke’s area while studying stroke patients

function: animal models

stimulation studies in rats are the basis of deep brain stimulation

comparative neuroanatomy

differences between species

Neurons

building blocks of the nervous system

Parts of a neuron and their functions

dendrites: receive info

cell body/soma: process info

axon: transmit info

With neuroanatomy, we look to understand...

1. Regional specificity: distinctions between regions of the brain, and within regions of the brain

2. Connectivity: how one brain region is connected to another

3. Function: what are the roles of these brain connections, and how do they play into our actions

Standard MRI Imaging

- Allows you to look at brain STRUCTURE

- MRI scanners, best resolution = about 1 mm

- Provides snapshot of what brain anatomy looks like

-Easy to examine changes over time (ex: see how much atrophy has occurred over 12 months)ike

FMRI (Functional MRI)

- Allows you to see changes in ACTIVITY in brain based on changes in blood flow

- Shows which part of brain is stimulated the most

- FMRI scanner, best resolution = about 2 mm

dMRI (Diffusion MRI)

- analyzes water movement within axons

- if water is pushed easily, then it is going with the direction of the axon

- if not able to be pushed, it is hitting the barrier of the axon

- goal is to map CONNECTIONS within the human brain

- uses water molecules and neurons filled with salt solution

Human Connectome Project

a large-scale, multi-university effort to map all connections in the human brain within all brain regions (Harvard, USC, UMN, Washington U)

Different neuronal structure =

different neuronal function

objective of neurons

transmit information from dendrites to the end of the axon through electricity

4 key elements for electrical communication in neurons:

- sodium, chloride, potassium, calcium

- become charged when dissolved (NA+, K+, Cl-, Ca^2+)

role of neuronal membrane

charge separation (separates intracellular fluid from extracellular space, and they contain different ion solutions)

Electrical signaling is due to

-Sodium and Potassium separation

- Na is restricted to OUTSIDE neuron

- K restricted to INSIDE neuron

- Ion pumps create this

neuron resting conditions

inside of neuron is more negative than outside, rests at -80 mv

action potential

-fundamental electrical signal in brain, brief change in charge

- happens once inside of neuron has more POSITIVE charge than outside

- ALL OR NONE: they either fire or they don't

- spike = NA+ IN (more positive)

- drop = K+ OUT (more negative)

neural code

neurons communicate through timing and number of action potentials

myelin sheath

made out of glial cells, covers axon terminal, allows action potentials to travel faster down the axon

ion pumps in neuronal membrane

maintain/restore charge separation, CONTINUOUSLY ACTIVE! (channels are only active during the action potential)

Where does an action potential start?

at "decision point" between cell body and axon

presynaptic side

axon terminal

synapse

space between two neurons

postsynaptic side

dendrite of another neuron

how do action potentials start?

- when multiple excitatory (positive) graded potentials happen at in rapid progression, threshold voltage level (-50) is exceeded and sodium channels open, which starts the action potential.

- potassium rushes out = hyperpolarization = more negative = drop

how are graded potentials and action potentials different?

graded potentials can have different levels of inhibition/excitation, action potentials have all or none responses

how are graded potentials formed?

when a neurotransmitter binds to its receptor, a certain type of channel will open in the membrane. depending on the type of channel, membrane will become more positive (excitation/depolarization) or more negative (inhibition/hyperpolarization)

neurotransmitters

chemical signals of the nervous system

neurotransmitters act to either:

- induce graded potentials that excite (depolarize) post-synaptic neurons

- inhibit (hyperpolarize) the post-synaptic neuron

Dopamine imbalances linked to:

Schizophrenia (too much dope), Parkinson's Disease (too little)

Serotonin imbalances linked to:

depression, OCD

Acetylcholine imbalances linked to:

Alzheimer's Disease

GABA imbalances linked to:

anxiety

Glutamate imbalances linked to:

epilepsy, Schizophrenia

Is dopamine excitatory or inhibitory?

both

Is serotonin excitatory or inhibitory?

both

Is acetylcholine excitatory or inhibitory?

both

Is GABA excitatory or inhibitory?

inhibitory: produces hyperpolarization

Is glutamate excitatory or inhibitory?

excitatory: produces depolarization

synaptic vesicle

spherical sac containing neurotransmitters

steps of synaptic transmission

1. synthesis

2. storage

3. release

4. receptor activation

5. inactivation

1. synthesis:

neurotransmitter manufactured in cell

2. storage:

neurotransmitter stored in vesicles for protection

3. release

action potential arriving at axon terminal will cause vesicles to move to membrane and release neurotransmitter into the synapse

4. receptor activation

neurotransmitters in the synapse can freely move about it. if they interact with a receptor (bind to it), they can activate the receptor to stimulate electrical charges in the postsynaptic neuron. receptor will hyperpolarize or depolarize

5. inactivation

neurotransmitters in the synapse (that didn't bind to receptors) are either A. altered into active substances or B. recycled (reuptake) back into presynaptic vesicles (vesicles in the axon)

what causes the release of a neurotransmitter?

calcium triggers vesicles to migrate to the end of axon and fuse with the membrane. more action potentials = more entry of calcium = more vesicles fusing with membrane = more neurotransmitters released