unit 1 quiz

ethology

study of animals in their natural setting

hawthorne effect

being observed may change the behavior of an individual

tinbergen quote

“gap between man and animal cannot possibly be bridged”

mind-brain problem

the brain exists as a physical object and is thus tangible, but the mind is an intangible experience

so how can you have a physical brain that produces non-physical thoughts?

• materialist approach: activity in the brain is the same as consciousness

• idealist approach: only the mind exists, and all of our experiences happen in the brain

physiological explanation of behavior

what is happening: describes behaviors as consequences of interactions of body parts

ontogenetic explanation of behavior

when does it happen: describes behaviors as a consequence of organism development (lifetime oriented)

ex. schizophrenia only shows up at a certain age

evolutionary explanation of behavior

how long has this been happening: describes behavior as a consequence of species development (generation oriented)

functional explanation of behavior

why is this happening: describes the evolution of a behavior as a consequence of the environment it was found in

benefits of animal research

human life expectancy increased by about 21 years because of research done on animals

• deadly viruses: spread of virus among animals

• addiction: cannot let people get addicted

• TBI (Traumatic Brain Injury): administration of TBI to mice with hammer thing

3 R’s of animal research

reduction: using the fewest number of animals possible or justify why you need more animals

replace: if the testing can be done in a cell culture or in some bug, don’t do it on an animal

refine protocols so no animal experiences pain

• unless pain is required for research, in which case animal is discharged humanely

• poorly treated animals mess up data

dendrites

form postsynaptic area that contains postsynaptic receptors and receives information from other neurons

soma

cell body → find all common cell parts and organelles necessary for functioning

axon hillock

where the action potential / saltatory conduction begins when a cell reaches threshold

axon

most specialized part of the neuron - distal projection that can be anywhere from 1 micron to 1 meter in length

myelin sheath

lipid insulator on axon that improves efficiency of conduction

node of ranvier

gaps or breaks in the sheath that help refresh a message

where saltatory conduction takes place

presynaptic terminals

electric aspect of message ends and chemical aspect of message begins

forms synapse with neighboring cell’s dendrite

astrocyte

• provides physical structure to neuron

• facilitates nutrient decay

• synchronizes neuronal firing of local clusters

can release neuropeptides like neurons, though rare

oligodendrocytes (CNS) and schwann’s cells (PNS)

both…

• make myelin sheath

• facilitate nutrition for axon

oligodendrocytes: form multiple sections of myelin simultaneously, possibly because of physical distance

schwann’s cells: form individual sections of myelin, possibly because of size of myelinated sections

radial glia

• neuronal migration during prenatal development

• assist post damage and serve as neuronal stem cells

• replacement of neurons

micro glia

neuronal immune system helping to remove harmful agents and helps clean up after damage

• removes harmful pathogens from the brain instead of the immune system killing bad cells from brain

  • if immune system removed pathogens, we’d get dumber every time we’d get sick

blood-brain barrier

many chemicals cannot cross from the blood to the brain

gut bacteria

bacteria in our gut is product of diet, environment, and other factors

• having more gut microbiome diversity allows for better mental health because of communication between gut and brain

• lower diversity makes it more likely to develop anxiety or depression

neuronal communication

electro-chemical process

• messages are voltage-based within the neuron and chemically between the cells

• unidirectional: axon to presynaptic to synapse to postsynaptic (dendrite)

• on and off: either fire or they don’t

action potential (neuronal firing): beginning at rest

2-5 ms long event depending on the type of neuron

• neuronal membrane is semi-permeable with specific channels and gaps within it

  • concentration gradient: things want to move from higher concentration to lower concentration

  • electrical gradient: charged ions will be drawn to opposite charges (opposites attract)

what ion is more concentrated outside the cell at rest?

sodium

what cell is more concentrated inside the cell at rest?

potassium

why are chloride ions difficult to move in and out of the membrane?

large and very negatively charged

negatively charged proteins

too large to move out of the cell, but are responsible to maintain the negative resting state of the neuron so the positive ions can enter

sodium potassium pump

active transport pump (takes energy to move stuff)

• brings 2 K+ ions and 3 NA+ ions out of the cell each cycle to help reset and maintain resting potential

voltage-gated ion channels

passive transport channel (responds to movement)

• open and close in response to specific voltage (local electrical charge)

  • shaped to only allow their specific ion to pass through

at rest, the neuron is negatively charged around

70 millivolts

neuron at rest

neuronal membrane keeps sodium out and potassium in, but some potassium sneaks out

• concentration gradient and electrical gradient pulls sodium inside cell

• electrical gradient keeps potassium in cell, but concentration gradient causes some potassium to be pushed out

all or none

when a neuron is stimulated by another cell, small depolarization

• if depolarization reaches the threshold (-55 mv), then all local sodium channels open and sodium enters the cell

• neuron doesn’t fire if threshold isn’t reached

• always fires with the same potency

neuronal firing

the influx of sodium turns the inter-neuronal charge positive, changing function of electrical gradient

• sodium channels close (preventing more sodium influx) and potassium channels open (allowing potassium to escape)

  • both opened by same depolarization

depolarization is caused by

K+ ions moving out rapidly during neuronal firing

hyperpolarization

for 1-2 ms the sodium channels are inactive and potassium flows out of the cell

• sodium-potassium pump is working to restore balance, but brief stage of hyperpolarization or refractory period

  • active refractory: it’s impossible for the neuron to fire at this state

  • relative refractory: requires stronger stimulation for neuron to fire

potential propagation

electrical signals travel down the axon in waves because of concentration gradient

• as sodium enters the cell, it diffuses down the membrane in both directions

  • vgsc are depolarized and begin the process again, while the vgsc towards the soma are prevented from reactivating by the refractory period

myelin sheath

lipid insulator that wraps around the axon with no sodium channels under it

• so sodium goes through unmyelinated sections of nodes of ranvier where active and passive transports are present

conduction is better under the sheath because

for sodium, movement in one direction is easier because there are fewer competing forces, allowing the ion to easily pass to the next myelinated section

synapse

identified by ramon y cajal

found to be non-electrical by charles sherrington

• time between squeezing dog’s paw and withdrawing paw was fast but not electrically fast

law of temporal summation

multiple weak stimulations given in rapid succession cause a reflex / action potential

law of spatial summation

multiple weak stimulations given at random points caused a reflex / action potential

excitatory postsynaptic potential

caused by ionic movement → sodium channels open and sodium rushes into the cell

moving neuron closer to firing threshold → “fire!”

inhibitory postsynaptic potential

allows potassium to rush into the cell

moving neuron farther from firing threshold → “stop!”

graded potential

temporary local change in the electrical charge of the neuron’s membrane