brain and behavior ch1: cellular foundations of behavior

biological psychology

the study of the physiological, evolutionary, and developmental mechanisms or behavior and experience

dualism

belief that mind and body are different kinds of substance that exist independently

evolutionary explanation

understanding in terms of the evolutionary history of a structure or behavior

functional explanation

understanding why a structure or behavior evolved as it did

monism

belief that the universe consists of only one kind of substance

ontogenetic explanation

understanding in terms of how a structure or behavior develops

physiological explanation

understanding in terms of the activity of the brain and other organs

active transport

a protein-mediated process that expends energy to enable a molecule to cross a membrane

• glucose, amino acids, omega-3 fatty acids and several vitamins

afferent axon

axon that brings information into a structure

astrocytes

pass chemicals back and forth between neurons and blood among neighboring neurons star-shaped glia that synchronize the activity of the axons

dendrites

branching fibers from a neuron that receive information from other neurons

dendritic spines

short outgrowths that increase the surface area available for synapses

efferent axon

neuron that carries information away from a structure

endoplasmic reticulum

network of thin tubes that transport newly synthesized proteins to other locations

glia

type of cell in that nervous system that in contrast to neurons, does not conduct impulses over long distances

glucose

a simple sugar

interneuron

neuron whose axons and dendrites are all confined within a given structure

intrinisic neuron

neuron whose axons and dendrites are all confined within a given structure

membrane

structure that seperates the inside of the cell from the outside environment

microglia

cells that remove waste material and other microorganisms from the nervous system

mitochondrion

structure that performs metabolic activities

motor neuron

neuron that recieves excitation from other neurons and conducts impulses to a muscle; soma in the spinal cord

myelin sheath

insulting material that covers vertebrate axon

neurons

cells that receive information and transmit it to other cells

nodes of ranvier

interruptions in the myelin sheath of vertebrate axons

nucleus

structure that contains the chromosomes

olgiodendrocytes

glia cells that build myelin sheaths that insulate certain vertebrate axons in the central nervous system

presynaptic terminal

(end bulb or bouton) point where an axon releases chemicals

radial glia

cells that guide the migration of neurons and the growth of axons and dendrites during embryological development

ribosomes

sites for cell synthesis of new protein molecules

schwann cells

glia cells that build myelin sheaths around one axon in the peripheral nerve

sensory neuron

neuron that is highly senstive to a specific type of stimulation

thiamine

a B1 vitamin necessary to use glucose

absolute refractory period

a time when the membrane is unable to produce an action potential

all or none law

principle that the amplitude and velocity of an action potential are independent of the stimulus that initiated it

concentration gradient

difference in distribution of ions across the neurons membrane

what is depolarization

to reduce polarization toward zero across a membrane

cell body/soma

contains nucleus, ribosomes, and mitochondria

axon

thin fiber of constant diameter with branches near its end that conveys an impulse to other neurons, organs, or a muscle

hypothesis tripartite synapse

tip of an axon releases chemicals that cause the neighboring astrocyte to release its own chemicals, thus modifyinf the message to the next neuron; active partners of neurons

electrical gradient/polarization

difference in the electrical charge between the inside and out of the cell

resting potential

difference in voltage; inside of the membrane has a slight negative charge compared to the outside, mainly because of negatively charged proteins inside the cell

selectively permeable

letting some chemicals pass more freely than others; oxygen, carbon dixoide, urea and water are uncharged chemicals that cross freely through channels that are always open

sodium potassium pump

protein complex, repeatedly transports three sodium ions out of the cell while drawing two potassium ions in; sodium ions are more than 10 times more concentrated outside the membrane than inside, and potassium ions are more concentrated inside than outside

why is the sodium potassium pump effective

selective permeability of the membrane prevents the sodium ions that were pumped out from leaking back in

what leakage increases the electrical gradient across the membrane

potassium in the neurons do so slowly, carrying a positive charge

what does resting potential do

prepares the neuron to respond rapidly

how do sodium channels open after resting potential

excitation of the neuron, sodium enters the cell rapidly

what happens when action potential reaches threshold

membrane opens its sodium channels and permits sodium ions to flow into the cell, driving the membrane potential upward, far beyond what the stimulus itself provided

action potential

stimulation beyond the threshold

what does subthreshold produce

a small response that quickly decays

what do volatge gated channels do

open or close depending on the voltage arcoss the membrane

how does the membrane get back to its original level after action potential

potassium channels remain open after the sodium channels close, enough potassium has left

when does the sodium potassium pump occur

after the membrane has returned to its resting potential

what happens after an unusually rapid series of action potential

the sodium potassium pump cannot keep up, sodium accumulates in the axon and produces potentially toxic effects

what do local anesthetic drugs do

attach to the sodium channels of the membrane, preventing sodium ions from entering, thus message of pain not sent to brain

propagation of the action potential

action potential gives birth to a new action potential at each point along the axon ; transmission of an action potential down an axon

what happens when an axon back propagates into the cell body and dendrites

cell body and dendrites passively register the electrical event that started in the nearby axon, dendrites becomes more susceptible to the structural changes responsible for learning

is action potential electrical or chemical

electrical, but created my chemical changes

absolute refractory

neuron in the middle of firing; membrane cant produce an action potential regardless of stimulation

relative refractory

neuron needs more stimuli (excitation) to fire

refractory

neuron cant refire in the middle of it ; depends on of sodium channels are closed and potassium is flowing out of the cell

myelinated axons

covered in a myelin sheath only present in vertebrates, covered with layers of fats and protein

in myelinated axons, where does the action potential start

the first node of the ranvier

saltatory conduction

the jumping of action potentials from node to node

instead of admitting sodium ions at every point along the axon and pumping them out, what does the myelinated axon do

admits sodium only at its nodes

is an axon that has losts its myeline the same as an axon that never had it and why

no, because the axon lacks sodium channels where the myelin used to be most action potentials die out between one node and the next

what happens in multiple sclerosis

the immune system attacks myelin sheaths

local neurons

have no axon and communicate only with their immediate neighbors producing inhibitory effects, no axon to produce action potential or all or none law

graded potential in a cell

when greater amounts os stimulation produce greater depolarization

when graded potential is spread over a cell, what happens over the surface of the tiny neuron

it declines in strength over distance

what are the four fundamental forces

gravity, electromagenetism, the strong nuclear force, and the weak nuclear force

what did santiago ramón y cajal discover

that the brain is made of seperate cells called neurons

what does the shape of a neuron determine

its connections with other cells and thereby determines its function

microglia

proliferate after brain damage and remove toxic materials

by surrounding a connection between neurons, what do astrocytes do

shields it from chemicals circulating in the surround

what do astrocytes do for rythyms

generate rythyms such as rhythym of breathing

what do astrocytes do for the blood vessels

dilate them to bring more nutritents into the most active brain areas

what do astrocytes do for hormones

respond to them, which influences neurons

what do astrocytes do for the visual cortex

control the critical period for modification of it in early life

what do astrocytes and microglia do together for synapses

prune ineffective synapses and adjust the effectiveness of others; too much or little pruning during early development leads to development disorders

what is the role of microglia on neuronal actvity

provide negative feedback to put a brake on it, loss of this leads to seizures

for the blood brain barrier, how does water pass through

special protein channels in the wall of the endothelial cells

for the blood brain barrier, how do sodium potassium and chloride ions pass through

active transport

what is korsakoffs syndrome

thiamine deficiency (vitamin B1), leads to death of neurons and is marked by memory impairments, common in chronic alchoholism

how does gut bacteria influence brain activity

stimulates the vagus nerve, and releases chemicals that cross the lining of the intestines and enter the blood that affect mood and motivations based on amount and type