Neuroscience 101

Exam 1

What’s the task of neuro?

 to understand how the brain develops, functions, and allows us to see, learn, and think!

Brain structure and actions

produce mind and behavior experiences

mind and behavior experiences modify

brain structure and actions

Somatic intervention

alter Structure or \n function of the brain

behavioral intervention

the consequence

Manipulating the body can affect behavior

Somatic Intervention (IV) -Behaviors affected (DV)

Experience affects the body & brain

Behavioral Intervention (IV) - Somatic effects (DV)

No Intervention, just observation and measurement

Correlation: Somatic Variables

Neuroplasticity

Behavior and experiences lead to somatic changes

\*Capacity for change both in development AND adulthood

Somatic Intervention

Administer a hormone (SI)- to determine strength of mating behavior (BE)

Other ex of SI: stimulate brain region, cut connections between parts, etc

Behavioral Intervention

Put male in presence of female (BI) - Changes in hormone levels (SE)

Other ex of BI: present a visual stimulus, give training

Correlation

Brain size (SV) correlates with Learning scores (BV)

Hormone Levels (SV) correlates with strength of mating behavior (BV)

Enlarged Cerebral Ventricles (SV) correlates with Schizophrenic symptoms (BV)

\*Nothing is being altered in any way its just being measured

\

Although the development of the brain is hardwired…

The brain is a constantly changing PLASTIC organ

EX- rats whose nerve cells were more elaborate in an enriched cage as apposed to a plain one, musical instruments effect on the brain

Hard wiring

Cell connection, function, \n and communication. \n Organism’s inborn functions

Levels of analysis of the brain

social, organ, molecular, synaptic, cellular, circuit, brain regions, systems

Reductionism

Breaking down scientific explanations into simpler parts as a way of understanding them

EX waterfall illusion

Consciousness

Personal, private awareness of our thoughts, feelings, and emotions, and of the sensations that impinge upon us

The functional organization of the brain can be characterized BOTH by

localization of function and the integrative function of multiple brain areas and systems

Behavioral Neuroscience Viewpoints

1\.) Describe Behavior (structure, function)

2\.) Observe Development of behavior (ontogeny)

3\.) Study biological mechanisms (machine)

4\.) Study applications

5\.) Study evolution of behavior

what are the two types of cells?

neurons (nerve cells) and glial cells

neurons

80-90 billion; 100s of different types

neuron doctrine

proposed that 1) the cells of the brain are independent from one another structurally, metabolically, and physically and 2) that info is transmitted from one neuron to the next across tiny gaps (synapses)

Cajal’s findings

Independent (discrete) elementary signaling units

(cajal used Golgi’s staining method)

Golgi stains

Label a small minority of neurons in sample but reveals finer details

1st arrow

Input zone

Input zone

where neurons **collect and process info**, either from the environment or from other cells (dendrites)

2nd arrow

Integration zone

Integration zone

where the **decision** to produce a neuron signal is made (cell body/axon hillock)

3rd arrow

Conduction zone

conduction zone

(axon) where info can be electrically **transmitted** over great distances

4th arrow

output zone

output zone

where the neuron **transfers** info to other cells (axon terminals; presynaptic neuron)

name each part of the neuron

neurons vary in…

size, shape (multipolar, bipolar, unipolar) , and function (sensory, motor, interneuron)

Nucleus (chromosomes)

contain genes encoded in dna

mitocondria

\`produces energy

Ribosomes

Builds protein

Dendrites

Receives info

Dendritic spines increase in surface area and experience changes them (neural plasticity

axon hillock

gathers and integrates info from all the synapses on the dendrites and cell body and converts the info into a code of electrical impulses that carries the neuron’s message down the axon and toward its targets

axon

transmits info

myelin (only vertebrate axons)

fatty insulating substance (makes the axon look like beans)

protects and supports the axon

nodes of ranvier

space between the beads, small uninsulated patches of axon membrane are exposed

axon collaterals

synaptic vesicles

tiny hollow spheres in the presynaptic axon termonal

neurotransmitter

each vesicle contains one which is a specialized chemical substance which the neuron uses to communicate with the postsynaptic neuron

synaptic cleft

transfers info

Post Synaptic Dendrite/Dendritic Spine

receives info (5k-10k contacts)

Receptors

Specialized protein molecules that capture and react to molecules of the neurotransmitter

synapse=

presynaptic terminal membrane + synaptic cleft + postsynaptic neuron membrane

Cell membrane

Lipid Bilayer

Intra and extra cellular fluid

Selectively permeable

Multipolar neurons

many dendrites and a single axon, they are the most common type

Bipolar

Have a single dendrite at one end of the cell and a single axon at the other end. Especially common in sensory systems (EX: vision)

Unipolar / monopolar

single axon that branches in two directions after leaving the cell body. One end input and other end output. Transmits touch info from body to the spinal cord

Afferent

Approach the CNS

Efferent

carry signals away from the CNS

Sensory neurons (afferent)

input: sensory organs contains receptors and adequate stimuli stimulates those receptors

output: synapse onto (communicate with) interneurons

Interneurons

input: receives info from either sensory neurons or other interneurons

output: synapse onto other interneurons or motor neurons

motor neurons (efferent)

input: receives info from other neurons

output: synapse onto muscles, organs, and glands

Glial cells

contribute to info processing (astrocytes)

removes waste, viruses, fungi from the brain (microglia)

May be involved in pain perception

Builds myelin sheath in vertebrate axons

oligodendrocytes

in CNS helps build myelin sheath

More than 75% of the brain’s glial cells are these

Schwann cells

in PNS performs myelination

neurons…

receive, conduct, and transmit info

neurophysiology

The study of chemical and electrical processes in neurons

electrochemical sequence

electrical- within the neuron

chemical- between neurons

Neuron “at rest”

not currently generating an action potential

Properties of a neuron at rest

polarized membrane potential, inside more negatively charged than outside (polarized membrane), resting potential (-50 to -80mV)

ions

electrically charged molecules

anions

negatively charged molecules

cations

positively charged molecules

Forces behind resting membrane potential

unequal distribution of ions (random movement & concentration), electrical gradient-electrostatic pressure-potential homogenizing force, selectively permeable cell membrane and leakage

what happens in a resting potential?

1) Net pressure driving K+ out, minimal resistance to K+ leaving cell the movement causes a difference in charge, counteracting electrostatic pressure is built up

2) Great pressure driving Na+ in high membrane resistance to flow

why do concentrations remain stable despite homogenizing forces?

\

sodium potassium pump

for every 3 Na+ out two K+ in - maintains concentration gradient

what maintains electrical gradient and polarized membrane?

Negatively charged proteins inside the cell, net loss of positive charge with pump, K+ can leak back out

why isn’t the neuron electrically neutral at rest?

needs to be primed and ready storing up potential energy so that when the signal comes it is ready to be released (bow and arrow)

diffusive force

electrostatic force

In resting potential the cell membrane is selectively permeable to…

potassium (K+)

In a resting potential the diffusive force is…

pushing potassium (K+) out of the cell and the electrostatic force is pushing K+ into the cell

What creates this diffusive force?

The concentration gradient.

Does the concentration gradient produce a diffusive force that outweighs the electrostatic force?

yes

^What does this mean?

The amount of K+ leaving the cell is greater than the amount coming in by the electrostatic force

Passive flow of K+ out of the cell at neuron at rest

Doesn’t require any energy and is just LEAKING out of the cell this means that there is more K+ leaving than is coming in and its leaking out

As potassium leaks out of the cell it is taking positive charges with it and making the inside more negative

Therefore there is a buildup of electrostatic force wanting to push potassium back into the cell and it pushes it back in more and more until it reaches the equilibrium potential

when is the amount of potassium leaving the cell equal to the amount entering? (no net difference)

during the equilibrium potential

Equilibrium Potential

When the diffusive force and the electrostatic force are equal to each other and will no longer change the electrical potential of that particular cell

what maintains the unequal distribution of ions? - sodium more concentrated outside the cell and potassium more concentrated inside the cell

sodium potassium pump

sodium potassium pump

an ion pump where for every 3 sodium ions pumped out 2 potassium ions are pumped in and this helps to maintain the concentration gradient

what maintains this electrical gradient and polarized membrane?

negatively charged proteins inside the cell, with that sodium potassium pump there is a net loss of positive charge every time the pump works - more positive ions leaving cell

is the neuron electrically at rest and if not why?

Its not bc its storing up electrical potential so that when the neuron is ready it can send it’s particular signal

What is an action potential?

a massive momentary reversal of the electrical potential of the membrane from about -60mV to about +40mV that arises in the initial segment of the axon (axon hillock) and is propagated at a high speed along the axon’s length

Depolarization

making the inside of the neuron more positive on the inside. Decreasing the electrical potential between the inside and the outside. Above threshold.

Hyper-polarization

making the inside of the neuron even more negative relative to the outside than at resting state. Increasing the electrical potential between the inside and the outside. Below threshold.

Threshold of excitation

When the depolarization is enough to exceed threshold which allows for an action potential to be produced.

What exactly are the sequence of events resulting in an action potential?

The neuron is at resting potential at -70mV. All of a sudden there is a change in the membrane potential that can get to +40mV! This is a massive momentary reversal of the electrical potential caused by a stimulus such as a depolarizing stimulus, that decreases the electrical potential between the inside and the outside.

what are the 2 necessary conditions for an action potential to occur?

depolarization and exceeding the threshold

what events are taking place during an action potential?

The flow of ions across the membrane through voltage gated channels