Biology: Ch. 4: The Nervous System

Question 1

Describe this neuron feature: axon

Answer 1

The axon transmits an electrical signal (the action potential) from the soma to the synaptic knob

Question 2

Describe this neuron feature: axon hillock

Answer 2

The axon hillock integrates excitatory and inhibitory signals from the dendrites and fires an AP if the excitatory signals are strong enough to reach threshold

Question 3

Describe this neuron feature: dendrite

Answer 3

Dendrites receive incoming signals and carry them to the soma

Question 4

Describe this neuron feature: myelin sheath

Answer 4

The myelin sheaths act as insulation around the axon and speed conduction

Question 5

Describe this neuron feature: soma

Answer 5

The soma is the cell body and contains the nucleus, the endoplasmic reticulum and ribosomes

Question 6

Describe this neuron feature: synaptic bouton

Answer 6

The synaptic bouton lies at the end of the axon and releases the neurotransmitter

Question 7

What is the collection of cells in the CNS called?

Answer 7

A collection of cell bodies in the central nervous system is called a nucleus

Question 8

What is the collection of cells in the PNS called?

Answer 8

A collection of cell bodies in the peripheral nervous system is called a ganglion

Question 9

Describe each of the following glial cells: astrocyte

Answer 9

Astrocytes nourish neurons and form the blood brain barrier

Question 10

Describe each of the following glial cells: ependymal cell

Answer 10

Ependymal cells produce cerebral spinal fluid

Question 11

Describe each of the following glial cells: microglia

Answer 11

Microglia ingest and break down waste products and pathogens

Question 12

Describe each of the following glial cells: oligodendrocyte

Answer 12

Oligodendrocytes produce myelin in the CNS

Question 13

Describe each of the following glial cells: schwann cell

Answer 13

Schwann cells produce myelin in the PNS

Question 14

what neural structure initiates an action potential

Answer 14

An AP is initiated in the axon hillock

Question 15

What entity maintains the resting membrane potential? What is the approximate voltage of the resting membrane potential?

Answer 15

The Na+/K+ ATPase maintains resting membrane potential at approximately -70mV

Question 16

What is temporal summation?

Answer 16

temporal summation is the integration of multiple signals close to each other in time

Question 17

What is spatial summation?

Answer 17

Spatial summation is the integration of multiple signals close to each other in space

Question 18

During the action potential, which ion channel opens first?

Answer 18

Sodium channel opens first at threshold (-50mV)

Question 19

How is the ion channel that opens first during an action potential (Na channel) regulated?

Answer 19

It is regulated by inactivation, which occurs around +35 mV. Inactivation can only be reversed by repolarization of the cell

Question 20

What effect does the opening of the first ion channel in an action potential (Na channel) have on the polarization of the cell?

Answer 20

Opening of the sodium channel causes depolarization

Question 21

During an action potential, which ion channel opens second?

Answer 21

Potassium channel opens around +35 mV

Question 22

How is the second ion channel that opens in an AP (K channel) regulated?

Answer 22

The potassium channel is regulated by closing at low potentials (slightly below -70 mV)

Question 23

What effects does the opening of the second channel in an AP have on the polarization of the cell?

Answer 23

The opening of the potassium channel causes repolarization and -eventually- hyperpolarization

Question 24

What is an absolute refractory period?

Answer 24

In the absolute refractory period, the cell is unable to fire an action potential regardless of the intensity of the stimulus

Question 25

What is a relative refractory period?

Answer 25

In the relative refractory period, the cell can fire an AP only with a stimulus that is stronger than normal

Question 26

What ion is primarily responsible for the fusion of neurotransmitter-containing vesicles with the nerve terminal membrane?

Answer 26

Calcium is responsible for the fusion of neurotransmitter vesicles with the nerve terminal membrane

Question 27

What are the three main methods by which a neurotransmitter’s action can be stopped?

Answer 27

A neurotransmitter’s action can be stopped by enzymatic degradation, reuptake, or diffusion

Question 28

Which parts of the nervous system are in the CNS?

Answer 28

The CNS includes the brain and spinal cord

Question 29

Which parts of the nervous system are in the PNS?

Answer 29

The PNS includes the cranial and spinal nerves and sensors

Question 30

What do afferent neurons do?

Answer 30

Afferent (sensory) neurons bring signals from a sensor to the CNS

Question 31

What do efferent neurons do?

Answer 31

Efferent (motor) neurons bring signals from the CNS to the effector

Question 32

What functions are accomplished by the sympathetic nervous system?

Answer 32

The sympathetic nervous system provides the “fight or flight” response, with increased heart rate and bronchial dilation, redistribution of blood to locomotor muscles, dilation of pupils, and slowing of digestive and urinary functions

Question 33

What functions are accomplished by the parasympathetic nervous system?

Answer 33

The parasympathetic nervous system promotes “rest and digest” functions, slowing heart rate and constricting bronchi, redistributing blood to the gut, promoting exocrine secretions, constricting the pupils and promoting peristalsis

Question 34

What functions are accomplished by the somatic nervous system?

Answer 34

The somatic nervous system is responsible for voluntary actions- most notably, moving muscles

Question 35

What functions are accomplished by the autonomic nervous system?

Answer 35

The autonomic nervous system is responsible for involuntary actions, like heart rate, bronchial dilation, dilation of the pupils, exocrine gland function and peristalsis

Question 36

What is the pathway of neural impulses in a monosynaptic reflex?

Answer 36

In a monosynaptic reflex, a sensory (afferent, presynaptic) neuron fires directly onto a motor (efferent, postsynaptic) neuron

Question 37

What is the pathway of neural impulses in a polysynaptic reflex?

Answer 37

In a polysynaptic reflex, a sensory neuron may fire directly onto a motor neuron, but interneurons are used as well. These interneurons fire onto other motor neurons