Chapter 43

Question 1

Nervous system parts

Answer 1

Peripheral nervous system

Central nervous system

Question 2

Peripheral nervous system

Answer 2

Part of nervous system that has a network of wires connects brain and spinal cord to rest of body

In the PNS sensors send sensory input down sensory neurons to the CNS, the CNS then sends motor outputs via motor neurons to effectors

Question 3

Central nervous system

Answer 3

Consists of brain and is responsible for the processing of all sensory information

Recieves sensory input and sends motor output

Question 4

Anatomy of neuron

Answer 4

1. Dendrite- receives electrical signals from axons
   of adjacent cells
2. Cell body (soma)- includes nucleus, integrates incoming
   signals & generates outgoing signal
3. Axon- sends signal to dendrites of other neurons

Question 5

Neurotransmitters

Answer 5

Chemical messengers that transmit signal across the synapses

Question 6

Synapses

Answer 6

Area where axons transmit signals to dendrites

Consists of a pre and postsynpatic terminal

Presynaptic is at the end of the axon and where the action potential (electrical signal) is converted to a chemical signal called neurotransmitter

Question 7

Resting potential

Answer 7

The voltage of a neuron’s membrane when not in communication with other neurons is called the resting potential

Typically the interior of cell is negatively charged relative to outside it

Question 8

Action potential

Answer 8

rapid, temporary change in membrane potential

Three parts
1. Depolarization
2. Repolarization
3. Hyperpolarization

Question 8

Neurons intracellular concentration

Answer 8

High intracellular concentration of K+ and A- (negatively charged proteins)

Low intracellular concentration of Na+ and Ch-

Question 9

Sodium potassium pump (Na+/K+-ATPase)

Answer 9

Generally imports or takes in K+ ions and releases Na+ ions

1. Three Na+ ions enter pump, the ATP provides energy for a shape change that makes it be released outside cell
2. Two K+ ions enter pump and is released inside cell

Question 10

What are resting ions most permeable too?

Answer 10

K+ ions and crosses membrane easily across concentration gradient through K+ leak channels

Question 11

What happens as K moves out the cell?

Answer 11

Inside becomes more negatively charged compared to the outside

Question 12

Hyperpolarization

Answer 12

When the membrane potential becomes more negative at a particular spot on the neuron’s membrane

Occurs when ion channels open that let positive ions out, or ion channels that let negative ions in

Question 13

Threshold potential

Answer 13

negative charge that will not allow
action potential to proceed

Question 14

Depolarization

Answer 14

When the membrane potential becomes less negative (more positive).

The opening of channels that let positive ions flow into the cell can cause depolarization

Question 14

What can trigger a membrane voltage change

Answer 14

A stimulus can cause the membrane to open more voltage Na+ ion channels that depolarizes the cell

Movement of Na+ into cells cause even more Na+ channels to open

Question 14

How is an action potential created

Answer 14

When a large stimulus results in multiple depolarizing inputs that depolarizes the membrane above the potential threshold

Question 15

Refractory period

Answer 15

Inactivated Na+ channels behind depolarization zones prevents action potential from traveling backwards

Question 16

What effects speed of action potential

Answer 16

Axon diameter and myelination

Larger axons have a faster action potential because there are less less current leaks and more space for the ions to travel so it won’t bump into other ions

Question 17

How Myelination effects speed of action potential

Answer 17

membranes of specialized accessory cells (called Schwann cells in PNS & oligodendrocytes in
CNS) are wrapped around axons and form a myelin sheath

The myelin sheath acts as electrical insulation, preventing neurons from leaking, making transmission faster

Question 18

Glia

Answer 18

Specialized accessory organs that include Schwann cells in PNS and Oligodendrocytes in CNS that wrap around axons and form a myelin sheath

Question 19

Node of Ranvier

Answer 19

Gaps in the myelin sheath across axon that allow action potential to jump across node to node

Question 20

Synaptic transmission

Answer 20

1. When the action potential that arrives at the end of the axon triggers entry of calcium ions into presynaptic cell through voltage gate calcium ion channels
2. Synaptic vesicles fuse with the presynaptic membrane and releases neurotransmitters
3. The neurotransmitters bind to receptors on postsynaptic membrane initiating action potential if threshold potential is reached
4. Ion channels close and neurotransmitters are broken down or taken back up by presynaptic cell

Question 21

Threshold potential

Answer 21

critical level to which a membrane potential must be depolarized to initiate an action potential.

Question 22

Repolarization

Answer 22

Happens after action potential is generated the voltage reaches its highest point

Sodium gates begin to close, and potassium gates open and returns neuron to its resting state

Question 23

Hyperpolarization

Answer 23

Occurs when potassium channels remain open longer than necessary, making the inside of the neuron more negative than its resting potential

Question 24

Will net flow of K+ out of the cell occur indefinitely?

Answer 24

No, it will stop once the membrane reaches the equilibrium potential for K+.

Question 25

What would occur if sodium channels remained open once membrane depolarization was complete?

Answer 25

Repolarization would occur, but much more slowly since potassium moving out would counteract it

Question 26

Which neurons function to integrate information that reaches the central nervous system

Answer 26

Interneuron

Question 27

Interneuron

Answer 27

neurons that are found in the CNS and integrate sensory information by connecting sensory input to motor output.

Question 28

What ion channels are open during the resting potential

Answer 28

Voltage Na+ and K+ channels are closed

Question 29

What ion channels are open or closed during the rising phase

Answer 29

Na+ channels open
K+ channels closed

Question 30

What ion channels are open or closed during the falling phase

Answer 30

Na+ channels close
K+ channels open

Question 31

What happens during refractory period and what determines when it ends

Answer 31

During the refractory period, an action potential cannot be triggered even if the membrane potential reaches threshold because the voltage-gated Na+ channels are inactive.

how long it takes for the voltage-gated Na+ channels to reactivate at the end of an action potential determines when it ends

Question 32

A nerve impulse moves toward a neuron’s cell body along

Answer 32

dendrites

Question 33

Which of these causes the release of neurotransmitter molecules?

Answer 33

an action potential reaching the end of the axon as, vesicles fuse with the plasma membrane and release neurotransmitter into the synaptic cleft.

Question 34

The space between an axon of one neuron and the dendrite of another neuron is called what?

Answer 34

synaptic cleft

Question 35

Where are neurotransmitter molecules in vesicles located

Answer 35

synaptic terminals

Question 36

What hyperpolarizes the membrane

Answer 36

Inhibitory signals hyperpolarize the membrane and make the membrane potential even more negative than normal.

Question 37

Where in the neuron do action potentials begin?

Answer 37

Axon hillock which is the region where voltage-gated channels begin in a neuron

Question 38

Functions of presynaptic membrane

Answer 38

1. It propagates action potentials from the synaptic terminal.
2. it helps trigger the release of neurotransmitter in response to an action potential.

Voltage gated Ca^2+ channels are found here and reggulates release of neurotransmitter from presynaptic neuron

Question 39

Synaptic terminal

Answer 39

Membrane that propogate action potential

Question 40

Ligand-gated ion channels

Answer 40

Open in response to neurotransmitter in the synaptic cliff