chapter 2: structure and function of cells in the nervous system

Question 1

what does the central nervous system (CNS) consist of?

Answer 1

the brain and spinal cord

Question 2

what does the peripheral nervous system (PNS) consist of?

Answer 2

nerves and most of the sensory organs

Question 3

nerve

Answer 3

bundle of thousands of individual neurons wrapped in a tough protective membrane

Question 4

nerve fibers

Answer 4

transmit messages through the nerves from sensory organs to the brain or from the brain to muscles and glands

Question 5

sensory neurons

Answer 5

process sensory information gathered from the environment

Question 6

motor neurons

Answer 6

control motor behavior and muscle contractions

Question 7

interneurons

Answer 7

lie entirely within the CNS integrating sensory and motor stimuli

Question 8

local interneurons

Answer 8

communicate with nearby neurons to analyze small pieces of information

Question 9

relay interneurons

Answer 9

connect circuits of local interneurons between brain regions

Question 10

neurons

Answer 10

primary information-processing cells that transmit signals throughout the brain and body

Question 11

soma

Answer 11

cell body of a neuron which contains the nucleus

Question 12

dendrites

Answer 12

tree branches extending from the soma that receive messages transmitted across the synapse

Question 13

axon

Answer 13

a long thin tube thats outside surface carries information from the soma to the terminal buttons

Question 14

anterograde axonal transport

Answer 14

relies on kinesin to move information toward the terminal buttons

Question 15

retrograde axonal transport

Answer 15

relies on dynein to move information toward the soma at half the rate of anterograde axonal transport

Question 16

myelin sheath

Answer 16

a protective layer of fats and proteins covering the axon that allows efficient transmission of action potentials

Question 17

multiple sclerosis

Answer 17

deterioration of the myelin sheath that can lead to slower nerve transmission and axonal degeneration

Question 18

terminal buttons

Answer 18

knobs at the end of the axon terminal that secrete neurotransmitters

Question 19

synapses

Answer 19

small spaces in between the terminal buttons of one neuron and the dendrites of another

Question 20

glia

Answer 20

supporting cells of the nervous system that provide protection and nutrients, fight and remove pathogens and dead neurons, facilitate communication, and assist with the growth and repair of cells

Question 21

astrocytes

Answer 21

star-shaped glial cells that surround soma and dendritic membranes to nourish neurons and perform phagocytosis, ingesting dead cells and replacing the vacant area with scar tissue, as well as maintain the blood brain barrier

Question 22

oligodendrocytes

Answer 22

glial cells that form the myelin sheath with segments of space for faster transport along axons, and provide immune support and respond to inflammation after injury

Question 23

nodes of ranvier

Answer 23

uncoated portions of axons between segments of myelin sheath

Question 24

microglia

Answer 24

smallest of the glial cells that provides immune support by protecting the brain against invading microorganisms, responsible for neuroinflammation after injury, act as phagocytes that enable astrocytes to remove dead cells

Question 25

schwann cells

Answer 25

glial cells in the PNS that serve the same function as oligodendrocytes, while promoting regrowth by digesting dying axons after nerve damage and forming cylinders to guide axonal regrowth

Question 26

paul ehrlish

Answer 26

-discovered the blood brain barrier by injecting blue dye into the bloodstream that tinted all tissue except the brain and spinal cord -when he injected the dye into the ventricles in the brain, the CNS turned blue

Question 27

blood brain barrier

Answer 27

-a selectively permeable barrier between the blood and the fluid that surrounds the cells of the brain regulating the composition of fluid within and outside of neurons -lined with capillaries that carry blood into the CNS

Question 28

what is one reason the permeability of the blood brain barrier differs throughout the brain?

Answer 28

in the area postrema, neurons can enter and detect toxic substances in the blood that can induce vomiting

Question 29

how do cells communicate with each other?

Answer 29

through electrical signals

Question 30

what is the resting potential of an axon?

Answer 30

-70 mV

Question 31

depolarization

Answer 31

membrane potential becomes more positive increasing the likelihood of an action potential

Question 32

action potential

Answer 32

a burst of rapid depolarization that facilitates communication between neurons, followed by hyperpolarization back to resting potential

Question 33

what two forces can change the membrane potential of a neuron?

Answer 33

diffusion and electrostatic pressure

Question 34

what ions are present in the intracellular and extracellular fluid of a neuron and what are their charges?

Answer 34

sodium (Na+) potassium (K+) chloride (Cl-) organic anions (A-)

Question 35

which of the ions present in a neuron cannot leave the neuron and contributes to its negative internal charge?

Answer 35

organic anions (A-)

Question 36

what is the role of sodium in depolarization?

Answer 36

sodium from the extracellular fluid enters the cell through diffusion and remains there due to electrostatic pressure

Question 37

what is the role of potassium in depolarization?

Answer 37

potassium from the intracellular fluid exits the cell through diffusion but is pushed back in due to electrostatic pressure

Question 38

what is the role of chloride in depolarization?

Answer 38

chloride from the extracellular fluid enters the cell through diffusion but is pushed back out due to electrostatic pressure

Question 39

what is the purpose of the sodium-potassium pump?

Answer 39

it keeps the intracellular concentration of sodium low

Question 40

how does the sodium-potassium pump work?

Answer 40

for every two potassium ions pushed in, three sodium ions are pushed out of the cell

Question 41

all-or-none law

Answer 41

an action potential either occurs or doesn't, the size is always constant

Question 42

rate law

Answer 42

an axon's firing rate represents varying information

Question 43

saltatory conduction

Answer 43

messages get smaller as they pass down the axon but are still large enough to trigger action potentials at the next node

Question 44

what are the six steps of an action potential?

Answer 44

1. membrane potential reaches the threshold of excitation, where the sodium channels open and sodium rushes into the cell 2. potassium channels open and potassium rushes out of the cell 3. sodium channels become refractory 4. potassium continues to leave the cell until the membrane returns to resting potential 5. potassium channels close and sodium channels reset 6. membrane becomes briefly more negative than resting potential while the sodium potassium pump gathers potassium

Question 45

what are the two advantages of saltatory conduction?

Answer 45

less energy is required and action potentials are conducted faster

Question 46

how do neurons communicate with each other?

Answer 46

neurotransmitters are released from the terminal buttons of the presynaptic neuron and attach to the binding sites of the postsynaptic neuron

Question 47

ligand

Answer 47

a chemical that binds to a receptor site

Question 48

what can binding to a receptor trigger?

Answer 48

opening of ion channels that all ions can use to enter and exit the cell

Question 49

synaptic vesicle

Answer 49

small, round structures that are packaged by transport proteins with several neurotransmitters, peptides, or other ligands to be taken across the synaptic cleft by trafficking proteins

Question 50

what are the four types of synapses?

Answer 50

axo-dentritic, axo-somatic, axo-axonic, and dendro-dendritic

Question 51

exocytosis

Answer 51

mechanism of active transport by which molecules are released from the cell through calcium channels that are opened by depolarization during action potentials

Question 52

ionotropic (direct) receptor

Answer 52

ligands bind to receptor site and ion channel opens

Question 53

metabotropic (indirect) receptor

Answer 53

ligands bind to receptor site which activates a g-protein to activate second messengers to induce ion release

Question 54

excitatory postsynaptic potential

Answer 54

sodium and calcium channels are opened to increase the likelihood action potentials by depolarizing the postsynaptic cell

Question 55

inhibitory postsynaptic potential

Answer 55

potassium and chloride channels are opened to hyperpolarize the postsynaptic cell and decrease the likelihood of action potentials

Question 56

reuptake

Answer 56

the rapid removal of neurotransmitters from the synaptic cleft back into the terminal buttons of the presynaptic neuron by transporter molecules

Question 57

enzymatic degradation

Answer 57

enzymes break apart neurotransmitters released from terminal buttons to prevent the overstimulation of postsynaptic cells and excessive firing

Question 58

autoreceptor

Answer 58

located on the terminal button of the presynaptic cell and regulates the amount of neurotransmitters released

Question 59

neuromodulators

Answer 59

chemicals released that alter the transmission of signals between neurons, helping or inhibiting receptors

Question 60

hormones

Answer 60

neuromodulators secreted into extracellular fluid by endocrine glands or cells in various organs and bound to target cells

Question 61

peptide hormones

Answer 61

bind to metabotropic receptors and alter the physiology of a cell

Question 62

steroid hormones

Answer 62

alter protein production of cell because they are smaller and more fat soluble than peptide hormones