Chapter 2: Structure and function of the nervous system

Question 1

What is an action potential?

Answer 1

The active or regenerative electrical signal that is required for synaptic communication. Action potentials are propagated along the axon and result in the release of neurotransmitters.

Question 2

What is the amygdala and in what is it involved?

Answer 2

A collection of neurons anterior to the hippocampus in the medial temporal lobe that is involved in emotional processing.

Question 3

What is the association cortex?

Answer 3

The volume of the neocortex that is not strictly sensory or motor, but receives inputs from multiple sensorimotor modalities.

Question 4

How is the autonomic nervous system also called?

Answer 4

Also autonomic motor system or visceral motor system.

Question 5

What is the autonomic nervous system, what does it regulate, and when may it become activated?

Answer 5

The body system that regulates heart rate, breathing, and glandular secretions and may become activated during emotional arousal, initiating a fight-or-flight behavioral response to a stimulus.

Question 6

What are the subdivisions of the autonomic nervous system?

Answer 6

It has two subdivisions, the sympathetic and parasympathetic branches.

Question 7

What are axon collaterals?

Answer 7

Branches off an axon that can transmit signals to more than one cell.

Question 8

What is an axon?

Answer 8

The process extending away from a neuron down which action potentials travel. The terminals of axons contact other neurons at synapses.

Question 9

What are the basal ganlia and of which 5 subcortical nuclei does it exists?

Answer 9

A collection of five subcortical nuclei:
1. The caudate
2. The putamen
3. The globus pallidus
4. The subthalamic nucleus
5. The substantia nigra

Question 10

What is the axon hillock?

Answer 10

A part of the cell body of a neuron where the membrane potentials are summed before being transmitted down the axon.

Question 11

In which processes are the basal ganglia involved?

Answer 11

The basal ganglia are involved in motor control and learning.

Question 12

Where do the neuronal loops in the basal ganglia project from/to?

Answer 12

The reciprocal neuronal loops project from cortical areas to the basal ganglia and back to the cortex.

Question 13

What are the two prominent diseases that are caused by disorders of the basal ganglia?

Answer 13

Two prominent basal ganglia disorders are Parkinson’s disease and Huntington’s disease.

Question 14

What is the blood-brain-barrier (BBB)?

Answer 14

A physical barrier formed by the end feet of astrocytes between the blood vessels in the brain and the tissues of the brain.

Question 15

What is the function of the blood-brain-barrier (BBB)?

Answer 15

The BBB limits which materials in the blood can gain access to neurons in the nervous system. Protecting it against viruses and other harmful substances.

Question 16

What is the brainstem?

Answer 16

The region of the nervous system that contains groups of motor and sensory nuclei, nuclei of widespread modulatory neurotransmitter systems, and white matter tracts of ascending sensory information and descending motor signals.

Question 17

Of which two things does the central nervous system (CNS) exist?

Answer 17

The brain and spinal cord.

Question 18

What is the central sulcus?

Answer 18

The deep fold or fissure between the frontal and parietal lobes that separates the primary motor cortex from the primary somatosensory cortex.

Question 19

What is the cerebellum?

Answer 19

Literally, “small cerebrum” or “little brain”. A large, highly convoluted (infolded) structure located dorsal to the brainstem at the level of the pons.

Question 20

What is the cerebellum’s function and in which processes is it involved?

Answer 20

The cerebellum maintains (directly or indirectly) interconnectivity with widespread cortical, subcortical, brainstem, and spinal cord structures, and plays a role in various aspects of coordination ranging from locomotion to skilled, volitional movement.

Question 21

What is the cerebral cortex?

Answer 21

The layered sheet of neurons that overlies the forebrain. The cerebral cortex consists of neuronal subdivisions (area) interconnected with other cortical areas, subcortical structures, and the cerebellum and spinal cortex.

Question 22

What are commissures and what is the largest commissure in the brain?

Answer 22

White matter tracts that cross from the left to the right side, or vice versa, of the central nervous system.

The corpus callosum is the largest commissure in the brain.

Question 23

What is the corpus callosum?

Answer 23

A fiber system composed of axons that connect the cortex of the two cerebral hemispheres.

It is the largest white matter structure in the brain.

Question 24

What is cytoarchitectonics?

Answer 24

Also called cellular architecture. The study of the cellular composition of structures in the body.

Question 25

What are dendrites?

Answer 25

Large treelike processes of neurons that receive inputs from other neurons at locations called synapses.

Question 26

What does depolarization mean and is it, in respect to the resting potential, closer or farther away from the firing threshold?

Answer 26

A change in the membrane potential in which the electrical current inside the cell becomes less negative.

With respect to the resting potential, a depolarized membrane potential is closer to the firing threshold.

Question 27

What is an electrical gradient?

Answer 27

A force that develops when a charge distribution across the neuronal membrane develops such that the charge inside is more positive or negative that the one outside.

Question 28

Of what is an electrical gradient the result?

Answer 28

Electrical gradients result from asymmetrical distributions of ions across the membrane.

Question 29

What does electrotonic conduction mean?

Answer 29

Also called decremental conduction.

Ionic current that flows passively through the cytoplasm and across the membrane of an activated neuron that diminishes with distance from the site of generation.

Question 30

What is the equilibrium potential?

Answer 30

The membrane potential at which a given ion has no net flux across the membrane – that is, the point where the numbers of ions moving outward and inward across the membrane are the same.

Question 31

Of the frontal lobe, name its location, function and its two principal regions

Answer 31

The mass of cortex anterior to the central sulcus and dorsal to the Sylvian fissure.

The frontal lobe contains two principal regions, each of which can be further subdivided into specific areas both architectonically and functionally.

The two principal regions of the frontal lobe are:
1. The motor cortex.
2. The prefrontal cortex.

Question 32

What are glial cells?

Answer 32

One of two cell types (the other one are neurons) in the nervous system.

Glial cells are more numerous than neurons, by perhaps a factor of 10, and may account for more than half of the brain’s volume.

They typically do not conduct signals themselves; but without them, the functionality of neurons would be severely diminished.

Tissue made of glial cells is termed glia.

Question 33

Name the 4 types of glial cells and in which nervous system they belong

Answer 33

There are 3 types of glial cells in the central nervous system:
1. Astrocytes
2. Oligodendrocytes
3. Microglial cells

In the peripheral nervous system, there is 1 type of glial cell:
1. Schwann cells

Question 34

What is grey matter en which structures does it include?

Answer 34

Regions of the nervous system that contain primarily neuronal cell bodies.

Gray matter includes the cerebral cortex, basal ganglia, and the nuclei of the thalamus.

Gray matter is so called because, in preservative solution, these structures look gray in comparison to the white matter where myelinated axons are found (which look whiter).

Question 35

What is a gyrus?

Answer 35

A protruding rounded surface of the cerebral cortex that one can see upon gross anatomical viewing of the intact brain.

Question 36

What is the hippocampus and in which processes is it involved?

Answer 36

A layered structure in the medial temporal lobe that receives inputs from wide regions of the cortex via inputs from the surrounding regions of the temporal lobe and sends projections out to subcortical targets.

The hippocampus is involved in learning and memory, particularly memory for spatial locations in mammals and episodic memory in humans.

Question 37

What does hyperpolarization mean and, in respect to the resting potential, is it closer or farther away from the firing threshold?

Answer 37

A change in the membrane potential in which the electrical current inside of the cell becomes more negative.

With respect to the resting potential, a hyperpolarized membrane potential is farther from the firing threshold

Question 38

What is the hypothalamus and in what does it play an important role?

Answer 38

A small collection of nuclei that form the floor of the third ventricle.

The hypothalamus is important for the autonomic nervous system and the endocrine system, and it controls functions necessary for the maintenance of homeostasis.

Question 39

What is the insula and with which areas does the insula have extensive reciprocal connections?

Answer 39

Also called insular cortex. A part of cortex hidden in the Sylvian fissure.

The insula also has extensive reciprocal connections with areas associated with emotion, such as the amygdala, medial prefrontal cortex, and anterior cingulate gyrus; as well as with frontal, parietal, and temporal cortical areas involved with attention, memory and cognition.

Question 40

What is an ion channel?

Answer 40

A passageway in the cell membrane, formed by a transmembrane protein that creates a pore, through which ions of a particular size and/or charge are allowed to pass.

Question 41

What is an ion pump?

Answer 41

A protein in the cell membrane of a neuron that is capable of transporting ions against their concentration gradient.

Question 42

What transports the sodium-potassium pump in and out the neuron?

Answer 42

The sodium-potassium pump transports sodium ions (Na+) out of the neuron and potassium ions (K+) into the neuron.

Question 43

What is a layer?

Answer 43

A common organizational cluster of neurons in the central nervous system.

Question 44

What is the limbic system, and which structures does it include?

Answer 44

Several structures that form a border (limbus in Latin) around the brainstem, named the grand love limbique by Paul Broca, which now include the amygdala, orbitofrontal cortex, and portions of the basal ganglia.

Question 45

Of the medulla, give the location, functions and of what processes nuclei are found within the medulla

Answer 45

The brainstem’s most caudal (lowest) portion.

The medulla in continuous with the spinal cord and contains the prominent, dorsally positioned nuclear groups known as the gracile and cuneate nuclei (which relay somatosensory information from the spinal cord to the brain) and the ventral pyramidal tracts (which contain descending projection axons from the brain to the spinal cord).

Various sensory and motor nuclei are found in the medulla.

Question 46

What is a microcircuit?

Answer 46

A small network of localized interconnected neurons that together process specific kinds of information-processing tasks such as sensation, action, and thought.

Question 47

Of the midbrain, name the structures what does it consist of, the processes the neurons in the midbrain participate in, and the location

Answer 47

Also called the mesencephalon; the part of the brain consisting of the tectum (meaning ‘roof’, and representing the dorsal portion), tegmentum (the main portion), and ventral regions occupied by large fiber tracts (crus cerebri) from the forebrain to the spinal cord (corticospinal tract), cerebellum, and brainstem (corticobulbar tract).

The midbrain contains neurons that participate is visuomotor functions, visual reflexes, auditory relays, and the mesencephalic tegmental nuclei involved in motor coordination (red nucleus).

It is bordered anteriorly by the diencephalon, and caudally by the pons.

Question 48

What is myelin?

Answer 48

A fatty substance that surrounds the axons of many neurons and increases the effective membrane resistance, helping to speed the conductions of action potentials.

Question 49

What is the neocortex and which areas are part of the neocortex?

Answer 49

The portion of the cortex that typically contains six main cortical layers (with sublayers) and has a high degree of specialization of neuronal organization.

The neocortex is composed of areas like the primary sensory and motor cortex and association cortex an, as its name suggests is the most modern (evolved) type of cortex.

Question 50

What are neural networks?

Answer 50

A complex network made up of long-distance connections between various brain regions.

Neural networks are macrocircuits composed of multiple embedded microcircuits, and they support more complex analyses, integrating information processing from many microcircuits.

Question 51

Of what are neurons responsible?

Answer 51

One of two cell types (the other one is the glial cell) in the nervous system.

Neurons are responsible for processing sensory, motor, cognitive, and affective information.

Question 52

What is a neurotransmitter?

Answer 52

A chemical substance that transmits the signal between neurons at chemical synapses.

Question 53

What are the nodes of Ranvier?

Answer 53

A location at which myelin is interrupted between successive patches of axon, and where an action potential can be generated.

Question 54

What are the two definitions of nuclei?

Answer 54

1. In neuroanatomy, a collection of cell bodies in the central nervous system.
2. In biology, a cellular organelle where DNA is stored.

Question 55

What is the location of the occipital lobe and in what are the neurons in this lobe primarily involved?

Answer 55

A cortical lobe located at the posterior of the cerebral cortex that primarily contains neurons involved in visual information processing.

Question 56

What is the location of the parietal lobe and in what are the neurons in this lobe primarily involved?

Answer 56

The parietal lobe is a cortical lobe located posterior to the central sulcus, anterior to the occipital lobe, and superior to the posterior temporal cortex.

This cortical region contains a variety of neurons, including the somatosensory cortex, gustatory cortex and parietal association cortex, which includes regions involved in visuomotor orienting, attention, and representation of space.

Question 57

What is the peripheral nervous system (PNS)?

Answer 57

A courier network that delivers sensory information to the CNS and then conducts the motor command of the CNS to control muscles of the body; the parts of the nervous system outside the brain and spinal cord.

Question 58

What does permeability mean?

Answer 58

The extent to which ions can cross a neuronal membrane.

Question 59

What is the pituitary gland and which structure controls the pituitary gland?

Answer 59

An endocrine gland that synthesizes and secretes hormones that aid in the regulation of multiple processes to maintain the normal state of the body (homeostasis).

It’s under control of the hypothalamus.

Question 60

What is the pons and what can be found in the pons?

Answer 60

A region in the brain that includes the pontine tegmental regions on the floor of the fourth ventricle, and the pons itself, a vast system of fiber tracts interspersed with pontine nuclei.

The fibers are continuations of the cortical projections to the spinal cord, brain stem, and cerebellar regions.

The pons also includes the primary sensory nuclear groups for auditory and vestibular inputs, and somatosensory inputs from, and motor nuclei projecting to, the face and mouth.

Neurons of the reticular formation can also be found in the anterior regions of the pons.

Question 61

What does postsynaptic mean?

Answer 61

Referring to the neuron located after the synapse with respect to information flow.

Question 62

What is the prefrontal cortex (PFC)?

Answer 62

A region of the cortex that takes part in the higher aspects of motor control and the planning and execution of behavior, perhaps especially tasks that require the integration of information over time and thus mandate the involvement of working memory mechanisms.

Question 63

What are the main regions of the prefrontal cortex?

Answer 63

The prefrontal cortex has three or more main areas that are commonly referred to in descriptions of the gross anatomy of the frontal lobe: the dorsolateral prefrontal cortex, the anterior cingulate and medial frontal regions, and the orbitofrontal cortex.

Question 64

What does presynaptic mean?

Answer 64

Referring to the neuron located before the synapse with respect to information flow.

Question 65

What is the refractory period?

Answer 65

The short period of time following an action potential during which the neuron may not be able to generate action potentials or may be able to do so only with larger-than-normal depolarizing currents.

Question 66

What is the absolute refractory period?

Answer 66

During the transient hyperpolarization state, the voltage-gated Na+ channels are unable to open, and no other action potential can be generated.

Question 67

What is the relative refractory period?

Answer 67

The absolute refractory period is followed by the relative refractory period, during which the neuron can generate action potentials, but only with larger-than-normal depolarizing currents.

Question 68

What does the resting membrane potential mean and what is the voltage of the resting membrane potential of an average neuron?

Answer 68

The resting membrane potential is the difference in voltage across the neuronal membrane at rest, when the neuron is not signaling.

The resting membrane potential of an average neuron is around -70mV

Question 69

What does saltatory conduction mean?

Answer 69

The mode of conduction in myelinated neurons, in which action potentials are generated down the axon only at nodes of Ranvier.

Measurement of the propagation of the action potential gives it the appearance of jumping from node to node – hence the term saltatory, which comes from the Latin saltare, meaning ‘to jump’.

Question 70

What is a soma?

Answer 70

The cell body of a neuron.

Question 71

What does somatotopy mean and how is it presented in the somatosensory cortex?

Answer 71

A point-for-point representation of the body surface in the nervous system.

In the somatosensory cortex, regions of the body near one another are represented by neurons located near one another. Regions that are farther apart on the body surface are coded by neurons located farther apart in the somatosensory cortex.

Question 72

What is the spike-triggering zone?

Answer 72

The location, at the juncture of the soma and the axon of a neuron, where currents from synaptic inputs on the soma and distant dendrites are summed and where voltage-gated Na+ (sodium) channels are located that can be triggered to generate action potentials that can propagate down the axon.

Question 73

What is a spine?

Answer 73

A little knob attached by a small neck to the surface of a dendrite. Synapses are located on spines.

Question 74

What is a sulcus, and how is it also called?

Answer 74

Also named fissure. An invaginated region that appears as a cut or crease of the surface of the cerebral cortex.

Question 75

What is the Sylvian (lateral) fissure and what is its location?

Answer 75

Also called the lateral fissure. A large fissure (sulcus) on the lateral surface of the cerebral cortex first described by the anatomist Franciscus Sylvius.

The Sylvian fissure separates the frontal cortex from the temporal lobe below.

Question 76

What is a synapse?

Answer 76

The specialized site on the neural membrane were a neuron comes close to another neuron to transmit information.

Synapses include both presynaptic and postsynaptic specializations in the neurons that are involved in chemical transmission.

Electrical synapses involve special structures called gap junctions that make direct cytoplasmic connections between neurons.

Question 77

What does synaptic elimination mean and how is it also called?

Answer 77

Also called pruning. The elimination of some synaptic contacts between neurons during development, including postnatally.

Question 78

What is the synaptic cleft?

Answer 78

The gap between neurons at synapses.

Question 79

What is synaptogenesis?

Answer 79

The formation of synaptic connections between neurons in the developing nervous system.

Question 80

What is the location of the temporal lobe?

Answer 80

Lateral ventral portions of the cerebral cortex bounded superiorly by the Sylvian fissure and posteriorly by the anterior edge of the occipital lobe and ventral portion of the parietal lobe.

Question 81

What does the ventromedial portions of the temporal lobe contain?

Answer 81

The ventromedial portions contain the hippocampal complex and amygdala.

Question 82

What are the lateral neocortical regions of the temporal lobe involved in?

Answer 82

The lateral neocortical regions are involved in higher-order vision (object analysis), the representation of conceptual information about the visual world, and linguistic representations.

Question 83

What are the superior portions within the depths of the Sylvian fissure of the temporal lobe involved in?

Answer 83

The superior portions within the depths of the Sylvian fissure contain auditory cortex.

Question 84

What is the thalamus and what is its major function?

Answer 84

The thalamus is a group of nuclei, primarily major sensory relay nuclei for somatosensory, gustatory, auditory, visual, and vestibular inputs to the cerebral cortex.

The thalamus also contains nuclei involved in the basal ganglia – cortical loops., and other specialized nuclear groups.

Question 85

Of what is the thalamus a part?

Answer 85

It is a part of the diencephalon, a subcortical region, located in the center of the mass of the forebrain.

Question 86

How many thalamus are in the brain and how are they connected in most humans?

Answer 86

Each hemisphere contains one thalamus, and they are connected at the midline in most humans by the massa intermedia.

Question 87

What is the threshold and what is its value?

Answer 87

The membrane potential value to which the membrane must be depolarized for an action potential to be initiated.

The value of the threshold is around -55mV.

Question 88

What is a tract?

Answer 88

A bundle of axons in the central nervous system.

Question 89

What is a ventricle?

Answer 89

Any of four large, interconnected cavaties of the brain.

Question 90

What is a vesicle?

Answer 90

A small intracellular organelle, located in the presynaptic terminals at synapses, that contains neurotransmitter.

Question 91

What are voltage-gated ion channels?

Answer 91

A transmembrane ion channel that changes molecular conformation when the membrane potential changes, altering the conductance of the channel for specific ions such as sodium, potassium, or chloride.

Question 92

What is white matter?

Answer 92

Regions of the nervous system composed of millios of individual axons, each surrounded by myelin. The myelin is what gives the fibers colour – hence the name white matter.