Functional Organization of Nervous Tissue

voltage

generated due to the distribution of negative and positive charges lining the inner membrane and lining the outer membrane of cells

measured based on inner charges relative to outer charges

unit of measure is millivolts (mV)

resting membrane potential

Vm of a cell when it is not being stimulated or inhibited

distribution of potassium plays the biggest role

potassium intercellular concentration

135

potassium extracellular concentration

5

permeability of potassium (reason K plays the biggest role in Vm)

1.0

sodium intracellular concentration

15

sodium extracellular concentration

140

sodium permeability

0.05

chloride intracellular concentration

10

chloride extracellular concentration

100

chloride permeability

0.45

by the sodium potassium pump

how are Na and K gradients maintained

false

True/false: the Na/K pump is responsible for resting Vm

dictators of Vm

size of concentration gradients

size of permeability

passive transport of ions

establishes resting Vm

change concentration gradient or change permeability

how does ion transport change

depolarize

Vm becomes more positive

inner membrane becomes more positive

outer membrane becomes more negative

hyperpolarize

Vm becomes more negative

inner membrane becomes more negative

outer membrane becomes more positive

repolarize

Vm returns towards resting Vm after a change in Vm

depolarize

increase extracellular Na

depolarize

increase extracellular K+

hyperpolarize

increase extracellular Cl-

hyperpolarize

decrease extracellular Na

hyperpolarize

decrease extracellular K

depolarize

decrease extracllular Cl

hyperpolarize

increase intracellular Na

hyperpolarize

increase intracellular K

depolarize

increase intracellular Cl

depolarize

decrease intracellular Na

depolarizw

decrease intracellular K

hyperpolarize

decrease intracellular Cl

depolarize

increase permeability Na

hyperpolarize

decrease the permeability of Na

hyperpolarize

increase the permeability of K

depolarize

decrease the permeability of K

hyperpolarize

increase the permeability of Cl

depolarize

decrease the permeability of Cl

action potential

local, large, and rapid depolarization followed by a repolarization; only a handful of cells generate these

threshold

depolarized Vm that must be reached to generate an action potential

all-or-none response

action potential will not occur if a threshold is not met

action potential frequency

directly proportional to the stimulus strength

sub-threshold stimulus

very small stimulus that does not cause a cell to reach threshold ; no action potential generated

threshold stimulus

stimulus that causes a cell to just reach threshold; one action potential generated; would not feel pain

submaximal stimulus

greater than threshold stimulus but less than maximal; greater than one action potential generated; would feel minimal pain

maximal stimulus

stimulus that causes the maximum number of action potentials; would feel a lot of pain

supra-maximal stimulus

action potential frequency does not increase despite large stimulus; cannot go beyond a maximum action potential frequency; lot of pain but much more damage than maximal stimulus

action potential conduction

spread of action potentials along a membrane; APs don’t move, but cause the generation of another in an adjacent region

velocity of conduction

depends on axon diameter and myelin; larger axons conduct APs faster because greater surface area means more voltage-gated ion channels

continuous conduction

occurs in unmyelinated axons and membranes of excitable cells; conduct velocity in less than 2 meters/sec; AP in one region stimulates another in an adjacent region

saltatory conduction

occurs solely in myelinated axons; APs generated at the nodes of ranvier; velocity ranges from 3 to 120 meters/sec; high concentration of Na/K channels at the nodes

synapse

junction between two cells that allows communication between those two cells

electrical synapse

communication between two cells via gap junctions; allows for rapid passage of info between adjoining cells; allows for coordination between electrically coupled cells

chemical synapse

communication between two cells via release of neurotransmitters

presynaptic membrane

membrane at the synapse that is carrying the info

presynaptic membrane

membrane at the synapse that is carrying the info

synaptic cleft

small space between presynaptic and postsynaptic membranes

neurotransmitters

chemicals released from presynaptic cell to postsynaptic cell; produced by presynaptic cell and most stored in synaptic vesicles

gaseous neurotransmitters

produced and released when needs; not stores

fate of neurotransmitters

reuptake of chemical neurotransmitters by presynaptic membrane

gaseuous neurotransmitters are metabolized by postsynaptic cell

reuptake inhibitor

drug that inhibits the reuptake of neurotransmitters; neurotransmitter remains in synaptic cleft longer; effect of neurotransmitter is enhanced; administered when natural neurotransmitter level is low

transient Vm change of postsynaptic membrane

due to neurotransmitter release on postsynaptic membrane

excitatory postsynaptic potential (EPSP)

depolarization followed by repolarization; influx of cations

inhibitory postsynaptic potential (IPSP)

hyperpolarization followed by repolarization; influx of anions or efflux of cations

summation

integrated sum of EPSPs and IPSPs; determines Vm change (if any)

spacial summation

when multiple postsynaptic potentials from different synapses occur at the same time

temporal summation

when multiple postsynaptic potentials from the same synapse occur at the same time

synaptic plasticity

ability of some structure of a synapse to change, formation of synapses or loss of synapses; large event must take place to cause plasticity

Acetylcholine (ACh)

excitatory or inhibitory

important arousal, sleep, attention, memory

neurotransmitter of the somatic and autonomic nervous system

treatment is ACh reuptake inhibitor

monoamines

serotonin, dopamine, and norepinephrine

serotonin

excitatory or inhibitory

important in temperature regulation, sleep, mood, nausea, vomiting

stimulates the gut

low level in the brain is thought to be linked to depression, anxiety, OCD, and PTSD

serotonin reuptake inhibitors (SSRIs)

prozac, paxil, zoloft, celexa, and lexapro

alternatives to SSRIs

psychotherapy, talk therapy, cognitive behavioral therapy, exposure therapy, exercise, meditation, and mindfulness

dopamine

excitatory or inhibitory

important in movement, attention, motivation, pleasure, and reward

high levels linked to tourette’s and psychosis

treat with dopamine receptor antagnonist

low dopamine

linked to depression, add, and addiction

treat with dopamine reuptake inhibitors (wellbutrin, ritalin, chantix)

treat with psychotherapy, exercise, mindfulness, and mindfulness

parkinson’s disease

loss of dopamine-producing neurons

norepinephrine

excitatory or inhibitory

important in decision making, attention, and mood

neurotransmitter of the sympathetic nervous system

low noreprinephrine

thought to be linked to depression and ADD

treat with noreprinephrine reuptake inhibitors (wellbutrin, ritalin, and effexor), psychotherapy, exercise, meditation, and mindfulness

amino acids

glutamate, GABA, and glycine

glutamate

major excitatory neurotransmitter in the CNS

plays a role in signaling in the CNS

has many functions including learning and memory

high level in the brain cause seizures and neural degeneration

treat with drugs that block glutamate release and receptors

neural degeneration

over exciting neurons and killing them (ALS)

ALS

caused by increased levels of glutamate which leads to neural degeneration

GABA

major inhibitory neurotransmitter in the CNS

plays a major role in signaling in the CNS

drugs that stimulate GABA receptors used to treat seizures (GABAergic drugs)

glycine

inhibitory neurotransmitter

plays a major role with signaling in the CNS

neuropeptides

endorphine and enkaphalins abnd substance P

endorphins and enkephalins

opioid compounds

inhibitory

important in regulation of pain and stress and gut mobility

morphine, oxycontin, and heroin are agonists to opioid receptors

narcan is an antagonist to opioid receptors, therefore, narcan blocks the effects of heroin

substance P

excitatory

important in the regulation of pain, anxiety, nausea, and breathing

inhibiting these receptors reduces pain and prevents nausea

gaseous neurotransmitters

cannot be stored

produced as they are needed

nitrous oxide and carbon monoxide

nitric oxide

excitatory or inhibitory

involved in many processes (erection, blood vessel tone, and memory)

carbon monoxide

excitatory or inhibitory

in many instances is a co-neurotransmitter with nitric oxide, so it has many similar functions

sensory memory

very, short-term retention of sensory input from the external environment

plays a protective role and we do not realize that it is happening

lasts up to three seconds and electrical in nature (solely a change in Vm)

if perceived, it is stored in short-term memory

short-term memory

lasts seconds to approximately one minute

electrical in nature (solely a change in Vm)

forgotten if an effort is not made to retain it or if an impression is not made

long-term memory

lasts minutes to hours and as long as a lifetime

information stored when an effort is made or an impression is made

synaptic in nature leads to synaptic plasticity

-older memories are typically stronger

Declarative/explicit (LTM)

retention of events, people, places, and facts

procedural/implicit

development of skills and conditioned reflexes

development of skills

walking, eating with a spoon, and driving a car

conditioned reflexes

associating an event/person with a smell

areas of the brain involved in memory

hippocampus, prefrontal cortex, amygdala, striatum, and mammillary bodies