[Biology] Ch.4: The Nervous System

Question 1

What are neurons

Answer 1

Specialized cells capable of transmitting electrical impulses and then translating those electrical impulses to chemical signals

Question 2

What is the difference between the functions of dendrites and the axon hillock

Answer 2

Dendrites receive messages from other cells while the axon hillock integrates incoming messages from other cells

Question 3

Signals arriving from dendrites can be either [ 1 ] or [ 2 ]; the axon hillock [ 3 ] these signals

Answer 3

1) excitatory 2) inhibitory 3) sums

Question 4

What determines whether or not the axon hillock will initiate an action potential

Answer 4

If the signals summed from the dendrites are excitatory enough

Question 5

Why are most mammalian nerve fibers insulated by myelin

Answer 5

To prevent signal loss or crossing of signals

Question 6

What is the relationship between myelin and the speed of conduction in the axon

Answer 6

It increases the speed of conduction

Question 7

Compare and contrast oligodendrocytes and Schwann cells

Answer 7

Both are cells that produce myelin but oligodendrocytes in the central nervous system and Schwann cells in the peripheral

Question 8

What do neurons use neurotransmitters for

Answer 8

To transmit information between neurons

Question 9

What are the three different kinds of neurons

Answer 9

Sensory, motor, or mixed

Question 10

The cell bodies of neurons of the same type are clustered together into [ 1 ]

Answer 10

Ganglia

Question 11

Glial cells play both [ 1 ] and [ 2 ] roles

Answer 11

1) structural 2) supportive

Question 12

What’s the difference between astrocytes and ependymal cells

Answer 12

Astrocytes nourish neurons and form the blood-brain barrier while ependymal cells line the ventricles of the brain and produce cerebrospinal fluid

Question 13

What are microglia

Answer 13

Phagocytic cells that ingest and break down pathogens in the central nervous system

Question 14

True or False: actin potentials are all-or-nothing messages

Answer 14

True

Question 15

What is membrane potential

Answer 15

An electrical potential difference (voltage) between the inside of the neuron and the extracellular space

Question 16

Resting potential is about [ 1 ] mV and the inside of the neuron is [ 2 ] relative to the outside

Answer 16

1) -70 2) negative

Question 17

At rest concentration of [ 1 ] is high and [ 2 ] is low inside the neuron

Answer 17

1) K+ 2) Na+

Question 18

At rest the concentration [ 1 ] is high and [ 2 ] is low outside the neuron

Answer 18

1) Na+ 2) K+

Question 19

What does Na+/K+ ATPase important for in the neuron

Answer 19

Restoring the K+ and Na+ gradient after action potentials have been fired

Question 20

Excitatory input causes [ 1 ] and thus makes the neuron [ 2 ] likely to fire an action potential

Answer 20

1) depolarization (raises the membrane potential from its resting potential) 2) more

Question 21

Inhibitory input causes [ 1 ] and thus makes the neuron [ 2 ] likely to fire an action potential

Answer 21

1) hyperpolarization (lowering the membrane potential from its resting potential) 2) less

Question 22

What is the threshold value

Answer 22

The range where an action potential will be triggered (-55 to -40 mV)

Question 23

What is the difference between temporal and spatial summation

Answer 23

• Temporal = multiple signals are integrated during a relatively short period of time
• Spatial = additive effects based on the number and location of incoming signals

Question 24

Compare the effect of inhibitory signals firing directly on the soma vs. excitatory signals firing on the dendrites of neurons

Answer 24

Inhibitory signals firing directly on the soma will cause more profound hyperpolarization of the axon hillock than the depolarization caused by a few excitatory signals firing on the dendrites of a neuron

Question 25

Describe the events on the membrane potential vs. time graph

Answer 25

• Influx of Na+ causing an increase in in membrane potential
• Membrane crosses threshold and action potential is initiated
• Efflux of K+ causing a decrease in membrane potential below threshold
• Hyperpolarization of the membrane
• Na+/K+ pump returns membrane potential to resting

Question 26

When the cell is brought back to threshold voltage-gated [ 1 ] channels open in response to [ 2 ] and permit the passage of [ 3 ] ions

Answer 26

1) sodium 2) depolarization of the membrane 3) sodium

Question 27

When and what are the three states of sodium channels

Answer 27

• Closed (before the cell reaches threshold and after inactivation has been reversed)
• Open (from threshold to approximately +35 mV)
• Inactive (from approximately +35mV to the resting potential)

Question 28

Once [ 1 ] has depolarized the cell there is an electrochemical gradient favoring the efflux of [ 2 ] from the neuron

Answer 28

1) sodium 2) potassium

Question 29

What is repolarization

Answer 29

When positively charged potassium cations are driven out of the cell and there is a restoration of the negative membrane potential

Question 30

What is the benefit of hyperpolarization

Answer 30

It makes the neuron refractory to further action potentials

Question 31

What is the difference between absolute refractory and relative refractory periods

Answer 31

• Absolute = no amount of stimulation can cause another action potential
• Relative = there needs to be greater than normal stimulation to cause an action potential

Question 32

What is the consequence of a refractory period

Answer 32

Information can only flow in one direction

Question 33

What affects resistance in an axon potential (describe effect on conduction speed)

Answer 33

• Increased length of the axon = higher resistance and slower conduction
• Greater cross-sectional area = faster propagation and decreased resistance

Question 34

Does the increased intensity of a stimulus result in an increased potential difference of an action potential

Answer 34

No. It leads to an increased frequency of firing

Question 35

What is an effector

Answer 35

A neuron that signals to a gland or muscle rather than another neuron

Question 36

Where are neurotransmitters stored prior to release

Answer 36

In membrane-bound vesicles in the nerve terminal

Question 37

What happens at the synaptic knob when the action potential reaches the nerve terminal

Answer 37

Voltage gated calcium channels open allowing calcium to flow into the cell (after calcium flows into the cell calcium triggers fusion of membrane-bound vesicles with the cell membrane and causing exocytosis of the neurotransmitter)

Question 38

What are the three ways neurotransmitters are cleared out of synaptic cleft

Answer 38

1. Broken down by enzymatic reactions
2. Brought back into the presynaptic neuron
3. Diffusion out of the synaptic cleft

Question 39

What’s the difference between sensory (afferent), motor (efferent), and interneurons

Answer 39

• Sensory = transmit sensory information from receptors to the spinal cord and brain
• Motor = transmit motor information from the brain and spinal cord to the muscles and glands
• Interneurons = found between other neurons; often linked to reflexive behavior

Question 40

Recite the mnemonic to remember the difference between afferent and efferent neurons

Answer 40

• Afferent neurons ascend in the spinal cord towards the brain/ afferent neurons are affected by the outside world
• Efferent neurons exit the spinal cord on their way to the rest of the body/ efferent neurons have an effect on the environment

Question 41

What is the difference between white and grey matter in the brain

Answer 41

• White matter = axons encased in myelin sheaths

- Grey matter = unmyelinated cell bodies and dendrites

Question 42

What are the four divisions of the spinal cord

Answer 42

Cervical, thoracic, lumbar, and sacral

Question 43

Where are white and grey matter located in the spinal cord

Answer 43

White matter on the outside of the cord and grey matter deep within

Question 44

The somatic nervous system consists of [ 1 ] and [ 2 ] neurons throughout the skin, joints, and muscles

Answer 44

1) sensory 2) motor

Question 45

What all does the autonomic nervous system help regulate

Answer 45

Heartbeat, respiration, digestion, and glandular secretions

Question 46

What is the main role of the parasympathetic nervous system

Answer 46

To conserve energy

Question 47

Which neurotransmitter is associated with the parasympathetic responses in the body and released by pre and post ganglionic neurons

Answer 47

Acetylcholine

Question 48

What is the vagus nerve responsible for

Answer 48

Much of the parasympathetic inner action of the thoracic and abdominal cavity

Question 49

The sympathetic nervous system is activated by [ 1 ] and is closely associated with [ 2 ] and [ 3 ] reactions

Answer 49

1) stress 2) rage 3) fear

Question 50

What is the mnemonic for for the sympathetic and parasympathetic nervous system

Answer 50

• Sympathetic = fight or flight

- Parasympathetic = rest and digest

Question 51

What is the difference between a mono synaptic reflex arc and a poly synaptic reflex arc

Answer 51

• Monosynaptic = there’s a single synapse between sensory neurons that receive the stimulus and the motor neuron that responds to it
• Polysynaptic = there is at least one interneuron between the sensory and motor neurons in a reflex arc