nervous system

Question 1

neuroscience

Answer 1

dealing with the structure or function of the nervous system and brain

Question 2

nervous system

Answer 2

circuits of neurons that integrate internal and external information

Question 3

neurons

Answer 3

cells that send and receive electrical or chemical signals

Question 4

How do neurons and nervous systems differ in association with species complexity?

Answer 4

more complex organisms have more complex nervous systems and more neurons

Question 5

CNS

Answer 5

central nervous system
brain and spinal cord

Question 6

PNS

Answer 6

peripheral nervous system
nerve cells outside the CNS

Question 7

What are the parts of a neuron? What do they do? List them in order of the direction in
which an electrical signal would typically travel down a neuron

Answer 7

dendrites: receive signals
cell body: contains cell machinery
axon hillock: integrates signal; “decider”
axon: sends signals to synaptic terminals
myelin sheath: covers axon
synaptic terminals: send signals to other cells (neurons, muscles, glands)

dendrites- cell body- axon hillock- axon- myelin sheath- synaptic terminals

Question 8

What are glial cells? name three and describe what they do

Answer 8

glial cells: help neurons but do not transmit nerve impulses

microglia: digests parts of dead neurons, forms scar tissue and reduce damage to other neurons in CNS and PNS
oligodendroglia: increase signaling speed (CNS)
Schwann cells: increase signaling speed (PNS)

Question 9

disease associated with myelin degeneration

Answer 9

multiple sclerosis

Question 10

What signals travel down neurons? what type of signals typically travel between neurons?

Answer 10

electrical signals travel down neurons
chemical signals travel between neurons

Question 11

three types of neurons found in the CNS and the PNS and how they work together to regulate behavior

Answer 11

1. sensory neurons: receive sensory input PNS->CNS
2. interneurons: transmits impulses between sensory and motor neurons
3. motor neurons: deliver sensory output CNS->PNS

Question 12

Which type of neuron is affected by Lou Gehrig’s disease?

Answer 12

motor neuron

Question 13

What does the squid have to do with neuroscience? Are neurons similar in squid and other animals?

Answer 13

squids have giant axons that are easy to study

similarities between squids and other animals: the electrical properties of neurons are similar across species

Question 14

membrane potential

Answer 14

every cell has a voltage (electrical charge difference) across its plasma membrane

Question 15

resting potential

Answer 15

the membrane potential of neuron that is not transmitted signals (inside of cell more negative than the outside)

Question 16

How are K+ and Na+ ions distributed within and outside a neuron that is at its resting membrane potential? What is meant by selective permeability?

Answer 16

at resting potential: Sodium (Na+) is mostly outside the neuron and potassium (k+) is mostly inside the neuron

selective permeability:
channels are selectively permeable to potassium or sodium
when neuron is at rest these channels are closed
potassium channels are “leaky”

Question 17

Define the resting membrane potential in terms of millivolts (mV), K+, Na+, and the
sodium-potassium pump.

Answer 17

-at rest membrane potential: fewer potassium (k+) inside than number of sodium (Na+) outside= slightly negative interior (-70mv)
-sodium-potassium pump: pumps 3 Na+ ions out for every 2 K+ it brings into the cell

Question 18

Explain the concentration and electrical gradients and the pressure they place on K+ and Na+ ions. Which pressure is more powerful for K+ in a neuron at rest?

Answer 18

when a neuron is at rest, the ions are under 2 pressures:

1) concentration gradients (stronger): passive transport of ions from high to low concentrations

application: K+ wants to leave the neuron and Na+ wants to enter to the neuron

2) electrical gradients: passive transport caused by an ion’s attraction to the opposite charge

application: both Na+ and K+ want to enter the neuron (because its interior is slightly negative)

Question 19

Under what circumstances are ions actively transported across the membrane? Under what conditions are they passively transported?

Answer 19

Active transport of ions helps maintain resting potential–sodium potassium pump (K+ ions are leaky so additional K+ leaves the neuron)–ions in a neuron at rest are under pressure

Passive transport (not at resting potential) occurs across concentration gradients from high to low concentration and across electrical gradients because ions are attracted to opposite charges

Question 20

What is a voltage-gated ion channel?

Answer 20

a specialized ion channel that opens/closes in response to changes in membrane potential (voltage)

Question 21

Explain depolarization in terms of the membrane potential and
ion channels involved (and what the ions are doing). Be able to represent them in a
figure (as on the lecture slides)

Answer 21

Depolarization
what: when magnitude of MP decreases, neuron’s interior becomes more positive

reasoning: movement of (+) ions in and/or (-) ions out increases likelihood of neuron firing an action potential

figure: upward tick toward the threshold line

ION CHANNELS
voltage-gated K+ channels: open (K+ ions enter the neuron & MP increases)

ligand-gated Cl- channels: closed (Cl- ions cannot enter the neuron to decrease MP

Question 22

Explain hyperpolarization in terms of the membrane potential and
ion channels involved (and what the ions are doing). Be able to represent them in a
figure (as on the lecture slides)

Answer 22

Hyperpolarization
what: when magnitude of membrane potential increases, neuron’s interior becomes more negative
reasoning: movement of + ions out and or - ions in decreases likelihood of neuron firing an action potential
figure: downward dip away from the threshold line

Ion channels
voltage-gated K+ channels: closed (no K+ ions can enter the neuron to increase membrane potential)
ligand-gated Cl-channels: open (Cl-ion enter the neuron and membrane potential decreases

Question 23

What is meant by graded potentials?

Answer 23

hyperpolarization and depolarization are both called graded potentials because the magnitude of the change in membrane potential varies with the strength of the stimulus

Question 24

What happens when a depolarization crosses the “threshold potential”?

Answer 24

causes action potential and the neuron “fires”

Question 25

How are action potentials different from graded potentials?

Answer 25

Graded potentials can be depolarizing or hyperpolarizing Action potentials always lead to depolarization of membrane and reversal of the membrane potential

Question 26

Define action potential.

Answer 26

action potential: a brief all-or-none depolarization of a neuron's plasma membrane, it is the type of signal that carries information

Question 27

Explain each step of the action potential (i.e., at each step what is happening with the membrane potential? What is happening with ions and ion channels?).

Answer 27

1. Resting stage: where Na+ and K+ channels are closed 2. Depolarization: Na+ channels open and Na+ diffuses into the cell 3. Rising phase: many Na+ channels open and many Na+ rushes into the cell--An action potential is triggers when the threshold potential is reached--Na+ channels open at -50mV and Na+ rushes into the cell and depolarizes the membrane POSITIVE FEEDBACK 4. Falling phase: K+ rushes out of the cell--Na+ channels are inactivated at 40mV and K+ channels open at 40mV--potassium ions exit the cell and hyperpolarize the membrane slightly below the resting potential 5. Undershoot: K+ slowly closing, Na+ inactivated--K+ channels close and Na+ channels change from inactivated to close state and the resting membrane potential is stored (during the refractory period Na+ channels are inactivated)

Question 28

When during the action potential does positive feedback come into play?

Answer 28

positive feedback comes into play during the depolarization stage of action potential 1) when membrane potential increases to reach threshold potential, voltage-gated Na+ channels open & sodium ions rush into the cell 2) influx of (+) charge further depolarizes the cell, causing more Na+ channels to open & more sodium ions to enter the cell

Question 29

When during the action potential is a neuron refractory and why?

Answer 29

what: the period in which neuron is completely incapable to generating another action potential (regardless of the strength of the stimulus) when: after the “undershoot” period why: voltage-gated Na+ channels responsible for depolarization are inactivated & cannot open (this prevents the influx of Na+ ions necessary to depolarize the membrane)

Question 30

How do different toxins affect ion channels? How are these toxins used?

Answer 30

tetrodotoxin: - purpose: defense - effect: blocks Na+ channels (can't initiate rising phase of action potential) - animal: puffer fish apamin: - purpose: defense - effect: blocks K+ channels (can't initiate hyperpolarization) - animal: honey bee alpha & beta toxins: - purpose: capturing prey - effect: shifts timing of Na+ channel opening/closing - animal: scorpion

Question 31

How does the action potential move down the axon? Why does it move only in one direction?

Answer 31

-depolarization of one region of axon stimulates depolarization of next region -action potential doesn't move backwards because Na+ channels become inactivated

Question 32

What determines the speed of an action potential? Why are some axons so large in squid? How can axons send rapid signals in humans even though axons are small?

Answer 32

Axon diameter (the larger the diameter the faster the action potential and the less leakage of ions there is) and myelin sheath (acts as an electrical insulator)

Question 33

What is saltatory conduction? What are nodes of Ranvier? How does an action potential travel down a myelinated axon?

Answer 33

-The transmission of motion of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials. -nodes of Ranvier: the gap in the myelin sheath of a nerve between adjacent glial cells

Question 34

What is a synapse

Answer 34

The site of communication between the synaptic terminal and another cell

Question 35

What is a presynaptic cell

Answer 35

the cell that releases the neurotransmitter that will stimulate the postsynaptic cell

Question 36

What is a postsynaptic cell

Answer 36

the cell that receives signal from the presynaptic cell and responds via depolarization or hyperpolarization

Question 37

What are the 2 types of synapses?

Answer 37

chemical synapse: a chemical acts as a signal between cells electrical synapses: electrical current flows from cell to cell

Question 38

What happens when an action potential reaches the axon terminal of a chemical synapse? What is the role of Calcium (Ca2+) channels? What is exocytosis? What is a vesicle? What is a neurotransmitter? What is a synaptic cleft?

Answer 38

1. Action potential opens calcium (Ca+) channels (calcium binds to vesicles) 2. Vesicles fuse to membrane, exocytosis of neurotransmitter 3. Neurotransmitter binds to receptors, exocytosis 4. Two types of receptors -Ca2+ channels allow calcium to come in and bind to the vesicle -exocytosis: the release of neurotransmitters into the synaptic cleft -vesicle: a packer of neurotransmitter -neurotransmitter: a chemical messenger between neurons -synaptic cleft: A tiny opening between neurons When the electrical signal reaches the presynaptic ending, it is translated into a chemical message that then diffuses across the synaptic cleft to the postsynaptic cell

Question 39

What do you call ion channels that are opened by chemical signals? What is meant by ligand gated? Do they have slow or rapid effects?

Answer 39

Ionotropic receptors OR ligand gated ion channels: where neurotransmitters can bind-- binds to receptors that are a part of ion channels, open ion channels, change membrane potential, rapid and short lasting

Question 40

What is an EPSP?

Answer 40

excitatory postsynaptic potentials

Question 41

What is an IPSP?

Answer 41

inhibitory postsynaptic potentials

Question 42

If one input to a postsynaptic neuron is usually too weak to initiate an action potential, then how are action potentials elicited? Which part of a neuron integrates the inputs?

Answer 42

Postsynaptic neurons will receive many inputs because one is usually to weak Synaptic integration aka summation occurs: integrates (sums) multiple synaptic inputs to produce a single output state

Question 43

What is a metabotropic receptor? How is it different from an ionotropic receptor?

Answer 43

Metabotropic receptor: the other receptor that a neurotransmitter can bind to when the action potential reaches the terminal Binds to a receptor that is not part of an ion channel, activates a signal transduction pathway, slower and long lasting Can open an ion channel indirectly or increase # of receptors, synthesis of neurochemicals, gene transcription etc... -Ionotropic: (1) neurotransmitter binds (2) channel opens (3) ions flow across membrane Metabotropic: (1) neurotransmitter binds (2) G-protein is activated (3) G-protein subunits of intracellular messengers modulate ion channels (4) ion channels open (5) ions flow across membrane (Can open an ion channel or activate another molecule)

Question 44

In brief, what is associated with dopamine, serotonin, GABA, and opioids?

Answer 44

dopamine: "wanting" serotonin: mood GABA: opioids: reward

Question 45

How does the GABA receptor work? Is it inhibitory or excitatory?

Answer 45

A neurotransmitter that sends chemical messages through the brain and the nervous system, and is involved in regulating communication between brain cells. The role of GABA is to inhibit or reduce the activity of the neurons or nerve cells GABA regulates neuronal excitability all over the CNS--most effects are inhibitory GABA is an ionotropic receptor

Question 46

What are the effects of drugs that influence the GABA receptor ion channel? What are they used to treat?

Answer 46

Drugs that act at GABA receptors are used to treat anxiety.

Question 47

What is an “SSRI”? How does it work? Why is it difficult to stop taking SSRIs? What is reuptake? What is receptor down regulation?

Answer 47

SSRI: serotonin specific reuptake inhibitors (ex. Prozac, Zoloft or Paxil) SSRIs ease depression by increasing levels of serotonin in the brain. Serotonin is one of the neurotransmitters that carry signals between brain cells. SSRIs block the reabsorption (reuptake) of serotonin in the brain, making more serotonin available SSRIs are metabotropic It is difficult to stop taking in response to high serotonin in synapse, receptors down regulate

Question 48

Know the basic biological principles demonstrated in class using 2 drug examples

Answer 48

1) Neurotransmitters are recycled 2) Neurotransmitters can reduce receptor numbers (dynamic system) 3) Drugs can influence ionotropic or metabotropic receptors 4) Drugs mimic or influence the brain's natural neurotransmitter systems

Question 49

How have reward circuits been identifies in the brain?

Answer 49

Electrical stimulation of the brain revealed a circuit involved in pleasure/reward (reward pathway=pleasure)

Question 50

What are three brain areas involved in reward?

Answer 50

1. Prefrontal cortex 2. Nucleus accumbens 3. Ventral tegmental area (VTA)

Question 51

What is a natrual reward?

Answer 51

feeding, sexual behaviors, social behaviors

Question 52

Do reward systems only exist in humans?

Answer 52

Studies were originally done in mammals but other research is looking into other animals reward systems

Question 53

What are two neurochemicals involved in reward? What are their functions?

Answer 53

Dopamine: motivated, reward-directed, anticipatory behaviors and remembering rewards (ex. I WANT this carrot) Opioids: (ex. endogenous, endorphins) pleasure/ reward (ex. I LIKE this carrot)

Question 54

What are self-administration studies? What do they show?

Answer 54

Certain circuits and neurochemicals are targeted by drugs of abuse (ex. heroin, cocaine, or amphetamine)--nucleus accumbens is the strongest response of pleasure Self-administered studies are ways to ask animals if something is rewarding: the study with the rat is an example, if the rat is pleasured it will press the bar to get more

Question 55

What are conditioned place preference studies?

Answer 55

another way to measure reward crayfish and other animals return to the place that made them feel pleasurable

Question 56

What mechanisms underline effects of commonly used drugs?

Answer 56

1. They mimic the chemical structure of that of natural neurotransmitters (ex. heroin mimics opiods) 2. They cause abnormally large amounts of natural neurotransmitter in synapses (ex. stimulants (amphetamine, ecstasy, Adderall, meth- amphetamine, cocaine) Some block reuptake, some reverse reuptake, some stimulate neurotransmitter release)