Notes 19

Question 1

What are neurons?

Answer 1

Neurons are nerve cells that transfer information within the body

Question 2

What are the 2 types of signals neurons use to communicate?

Answer 2

electrical signals (long-distance) and chemical signals (short-distance)

Question 3

Interpreting signals in the nervous system involves sorting a complex set of ____ and _____.

Answer 3

paths and connections

Question 4

Where does processing information take place?

Answer 4

Processing of information takes place either in
– simple clusters of neurons called ganglia
– a more complex organization of neurons called a brain

Question 5

Neurons are cell types of the nervous system that
exemplify the close relationship between ____ and ____ that arises during ____.

Answer 5

Form, function, and evolution

Question 6

Most of a neuron’s organelles are in the ___ ____. Most neurons have ____ (highly branched extensions that receive signals from other neurons). The ____ is typically a much longer extensions that transmits signals to other cells at _____. The cone-shaped base of an axon is called the ____ ____.

Answer 6

Most of a neuron’s organelles are in the cell body. Most neurons have dendrites, highly branched extensions that receive signals from other neurons. The axon is typically a much longer extensions that
transmits signals to other cells at synapses. The cone-shaped base of an axon is called the axon hillock

Question 7

The _____ _____ of one axon passes information
across the synapse as chemical messengers called
_____. A _____ is a junction between an axon and another cell. Information is transmitted from a _____ cell (neuron) to a ___ cell (neuron, muscle, or gland cell).

Answer 7

The synaptic terminal of one axon passes information
across the synapse as chemical messengers called
neurotransmitters. A synapse is a junction between an axon and another cell. Information is transmitted from a presynaptic cell (neuron) to a postsynaptic cell (neuron, muscle, or gland cell).

Question 8

Most neurons are nourished or insulated by cells called what?

Answer 8

Glia

Question 9

Nervous systems process information in what three stages?

Answer 9

sensory input, integration, and motor output

Question 10

Sensors detect external stimuli and internal conditions and transmit information along ____ ____. Sensory information is sent to the brain or ganglia, where ____ integrate the information. Motor output leaves the brain or ganglia via ___ ___, which trigger muscle or gland activity.

Answer 10

Sensors detect external stimuli and internal conditions and transmit information along sensory neurons. Sensory information is sent to the brain or ganglia, where interneurons integrate the information. Motor output leaves the brain or ganglia via motor neurons, which trigger muscle or gland activity.

Question 11

Many animals have a complex nervous system that
consists of what 3 things?

Answer 11

-A central nervous system (CNS) where integration
takes place; this includes the brain and a nerve cord
– A peripheral nervous system (PNS), which carries
information into and out of the CNS
– The neurons of the PNS, when bundled together, form nerves

Question 12

Why do membrane potential changes occur?

Answer 12

because neurons contain gated ion channels that open or close in response to stimuli.

Question 13

What do electrophysiologists do?

Answer 13

Electrophysiologists use intracellular recording to measure membrane potential

Question 14

What does the resting membrane potential of a neuron depend on?

Answer 14

The resting membrane potential of a neuron depends on the net movement of ions in and out of the cell.
When positive ions move into the cell (or negative ions
move out), the membrane becomes less polarized, or
depolarized. For example, depolarization occurs if Na+ channels open and Na+ diffuses into the cell. When positive ions move out of the cell (or negative ions
move into the cell), the membrane becomes more
polarized, or hyperpolarized. For example, hyperpolarization occurs if K+ channels in the neurons open.

Question 15

What are graded potentials?

Answer 15

Graded potentials are changes in polarization where the magnitude of the change varies with the strength of the stimulus. These are not nerve signals that travel along axons, but they do have an effect on generation of nerve signals.

Question 16

What is an action potential?

Answer 16

If a depolarization shifts the membrane potential
sufficiently, it results in a massive change in membrane voltage called an action potential. Action potentials have a constant magnitude, are all-or- none, and transmit signals over long distances.

Question 17

Why do action potentials occur?

Answer 17

They arise because some ion channels are voltage-gated, opening or closing when the membrane potential passes a certain level

Question 18

What are the series of stages in an action potential?

Answer 18

At resting potential
1. Most voltage-gated sodium (Na+) and potassium (K+)
channels are closed
When an action potential is generated
2. Voltage-gated Na+ channels open first and Na+ flows
into the cell
3. During the rising phase, the threshold is crossed, and
membrane potential increases
4. During the falling phase, voltage-gated Na+ channels
become inactivated; voltage-gated K+ channels open,
and K+ flows out of the cell
5.During the undershoot, membrane permeability to K+ is at first higher than at rest, then voltage-gated K+
channels close and resting potential is restored

Question 19

What is a refractory period?

Answer 19

The refractory period is a result of a temporary inactivation of the Na+ channels

Question 20

T or F:During the refractory period after action potential, a second action potential cannot be initiated.

Answer 20

True

Question 21

Where an action potential is generated, usually the ___ ___, an electrical current depolarizes the neighboring region of the ___ ____. Action potentials travel in only one direction: toward the ____ ____.

Answer 21

Where an action potential is generated, usually the axon hillock, an electrical current depolarizes the neighboring region of the axon membrane. Action potentials travel in only one direction: toward the
synaptic terminals

Question 22

Inactivated Na+ channels behind the zone of _____ prevent the action potential from travelling _____.

Answer 22

Inactivated Na+ channels behind the zone of depolarization prevent the action potential from
travelling backwards.

Question 23

The speed of an action potential increases with the axon’s ____. In vertebrates, axons are insulated by a ___ ____, which causes an action potential’s speed to increase.

Answer 23

The speed of an action potential increases with the axon’s diameter. In vertebrates, axons are insulated by a myelin sheath, which causes an action potential’s speed to increase.

Question 24

What are mylein sheets made of?

Answer 24

Myelin sheaths are made by glia— oligodendrocytes in the CNS and Schwann cells in the PNS.

Question 25

Action potentials are formed only at ___ ___ ____, gaps in the myelin sheath where voltage-gated Na+ channels are found. Action potentials in myelinated axons jump between nodes of Ranvier in a process called _____ ______.

Answer 25

Action potentials are formed only at nodes of Ranvier, gaps in the myelin sheath where voltage-gated Na+ channels are found. Action potentials in myelinated axons jump between nodes of Ranvier in a process called saltatory conduction.

Question 26

At electrical synapses, the electrical current flows from one neuron to another through ___ ____. At chemical synapses, a chemical ________ carries information between neurons. Most synapses are _____ synapses.

Answer 26

At electrical synapses, the electrical current flows from one neuron to another through gap junctions. At chemical synapses, a chemical neurotransmitter carries information between neurons. Most synapses are chemical synapses

Question 27

The presynaptic neuron synthesizes and packages the
neurotransmitter in ____ ____ located in the synaptic terminal. The action potential causes the release of the _____. The neurotransmitter diffuses across the ___ ___ and is received by the postsynaptic cell.

Answer 27

The presynaptic neuron synthesizes and packages the
neurotransmitter in synaptic vesicles located in the
synaptic terminal. The action potential causes the release of the neurotransmitter. The neurotransmitter diffuses across the synaptic cleft and is received by the postsynaptic cells.