Chapter 3

Question 1

Appearance of which animals set stage for the long series of evolutionary elaborations of the central nervous system that led to the brains of advanced mammals and birds?

Answer 1

the first chordate animals — the most primitive members of

the phylum to which humans, and all vertebrates belong.

Question 2

To survive, every animal from amoeba to human being must be able to perform certain basic actions (at least during active stages of its life). Most fundamental are(Schneider’s view):

Answer 2

(1) locomotor approach and avoidance movements,
(2) orienting (turning) toward or away from something,
(3) foraging behavior patterns and exploration of places
and objects.

Question 3

What is the act of foraging?

Answer 3

to search for provisions(a supply of food and other things that are needed)

Question 4

(3) foraging behavior patterns and exploration of places

and objects. is made up of what behaviors?

Answer 4

(1) locomotor approach and avoidance movements,
(2) orienting (turning) toward or away from something
+ the impelling drives of various kinds of motivational states.

Question 5

Why is being single-celled disadvantageous?

Answer 5

Despite all the activities that single-celled organisms were capable of, their small size severely restricted the environments they could thrive in.

Question 6

Do sponges have real nervous system?

Answer 6

no, but one can find cells that resemble neurons of more advanced creatures.

Question 7

What kind of cells do sponges have an what can they do?

Answer 7

Sponges have contractile cells that can respond to stimulation without intervention by neurons. These cells can conduct electrical potential changes in a neuroid or myoid manner (i.e., resembling conduction in neuronal or muscle cells). Such cells are critical for the basic actions of the sponge that enable it to survive.

Question 8

In which animals can we find the beginnings of specializations for intercellular communication that characterize the cells of nervous system?

Answer 8

In the Ctenophora and in Cnidaria like jellyfish and hydra (previously grouped together in the phylum Coelenterata)

Question 9

Who proposed the earliest stages in the evolution of nervous systems on the basis of anatomical studies of various species within phyla Ctenophora and Cnidaria( jellyfish and hydra (previously grouped together in the phylum Coelenterata))?

Answer 9

George Parker of Harvard University, 1919. Parker’s studies were reviewed and updated by George Mackie in 1970

Question 10

Phylum Ctenophora:

Answer 10

Ctenophora (/tᵻˈnɒfərə/; singular ctenophore, /ˈtɛnəfɔːr/ or /ˈtiːnəfɔːr/; from the Greek κτείς kteis ‘comb’ and φέρω pherō ‘carry’; commonly known as comb jellies) is a phylum of animals that live in marine waters worldwide. Their most distinctive feature is the ‘combs’ – groups of cilia which they use for swimming – they are the largest animals that swim by means of cilia. Adults of various species range from a few millimeters to 1.5 m (4 ft 11 in) in size. Like cnidarians, their bodies consist of a mass of jelly, with one layer of cells on the outside and another lining the internal cavity. In ctenophores, these layers are two cells deep, while those in cnidarians are only one cell deep. Some authors combined ctenophores and cnidarians in one phylum, Coelenterata, as both groups rely on water flow through the body cavity for both digestion and respiration. Increasing awareness of the differences persuaded more recent authors to classify them as separate phyla.

Question 11

Mackie’s first stage of evolution:

Answer 11

In Mackie ’ s first stage of evolution, the surface cells not only respond to external stimulation, but they are also contractile and are connected electrically to each other by gap junctions — sites of very close membrane apposition. This situation resembles intercellular interactions seen in sponges.

Question 12

Mackie’s second stage of evolution:

Answer 12

In a second stage, some cells lose their connection to

the surface and remain contractile, still connected electrically to the surface myoepithelium.

Question 13

Mackie’s third stage of evolution:

Answer 13

In a third stage, protoneurons evolve: They are a kind of sensorimotor neuron, connected to the surface and to underlying contractile cells (myocytes). All cells are still
electrically coupled.

Question 14

During Mackie’s which stage do protoneurons evolve?

Answer 14

During Mackie’s third stage of evolution.

Question 15

What are myocytes?

Answer 15

contractile cells

Question 16

Mackie’s fourth stage of evolution:

Answer 16

In Mackie ’ s fourth stage, there appear true neurons, not only sensory neurons but also motor neurons connected to them. These motor neurons connect to the contractile cells. Furthermore, chemical synapses evolve, adding specificity to the connections, although there is still electrical coupling between many of the epithelial cells at the surface as well as among the contractile cells.

Question 17

During Mackie’s which stage do true neurons evolve?

Answer 17

Mackie’s fourth stage of evolution.

Question 18

During Mackie’s which stage do chemical synapses

evolve?

Answer 18

Mackie’s fourth stage of evolution.

Question 19

According to Nauta, what do Mackie’s stages of evolution lack?

Answer 19

In Nauta’s view, these stages do not go far enough in depicting the evolution of a central nervous system. Even in cnidarians like hydra, there is evidence for the appearance of some intermediate neurons, interposed between sensory neurons and motor neurons. It is this kind of interposed neuron that has proliferated the most in the evolution of central nervous systems. They have evolved as a great intermediate net, underlying so much of the integrative activity of the nervous system.

Question 20

Which neurons proliferated the most in the evolution of central nervous system?

Answer 20

Intermediate neurons, they have evolved as great intermediate net.

Question 21

Even in which animal can we find intermediate neurons?

Answer 21

Even in cnidarians like hydra

Question 22

Hydra(genus)

Answer 22

Hydra /ˈhaɪdrə/ is a genus of small, fresh-water animals of the phylum Cnidaria and class Hydrozoa, native to the temperate and tropical regions. [2][3] Biologists are especially interested in Hydra because of their regenerative ability – they appear not to age or die of old age.

Question 23

What kind of neurons constitute “the final common path” for the nervous system control of actions?

Answer 23

motor neurons

Question 24

What kind of neurons’ axons are the only routes out of The CNS?

Answer 24

Motor neurons - output cells

Question 25

When motor neuron activation results from inputs at the same level of the central nervous system, we call the responsible circuit…

Answer 25

a local reflex pathway

Question 26

Primary sensory neuron:

Answer 26

This is the first neuron in a sensory pathway. The cell body is located outside the CNS, in the peripheral nervous system (PNS). Axons of these neurons enter the central nervous system.

Question 27

Secondary sensory neuron:

Answer 27

This is the type of neuron within the CNS that receives

synaptic inputs directly from primary sensory neurons.

Question 28

Interneuron:

Answer 28

A neuron of the great intermediate net of the CNS. All neurons in the CNS can be called interneurons except, by definition, the secondary sensory neurons and the motor neurons. However, many anatomists use the term in a more specific way to exclude the cells of origin of longer axon pathways. These anatomists use the term
to designate interneurons with short axons, terminating locally.

Question 29

Motor neuron:

Answer 29

Cell with an axon that leaves the CNS, travels through a peripheral nerve, and has endings on effector cells — usually muscle cells. Some axons that leave the CNS are from preganglionic motor neurons , as they terminate on ganglion cells in clumps of neurons outside the CNS; these ganglion cells have axons that terminate on
smooth muscle or gland cells.

Question 30

viscus, viscera means

Answer 30

an internal organ of the body; especially : one (as the heart, liver, or intestine) located in the great cavity of the trunk proper

Question 31

Ganglia (singular: ganglion):

Answer 31

Groups of neurons located outside the CNS. The term is

sometimes also used for a few specific cell groups within the CNS.

Question 32

Cell group, or nucleus , within the CNS

Answer 32

A group of neurons in the CNS that can be characterized as different from surrounding regions by its appearance in stained sections and/or by its functions.

Question 33

Nerve

Answer 33

A bundle of axons located outside the CNS (in the PNS).

Question 34

Tract or fasciculus (plural: fasciculi)

Answer 34

A group of axons located next to each other in the CNS; usually they have the same region of origin and they also share destinations. In the spinal cord, a group of such tracts located together are called a column (namely,
the dorsal column, lateral column, ventral column). Some smaller tracts are also called columns. These groups of axons may also be referred to as bundles.

Question 35

Neural tube

Answer 35

The entire central nervous system in animals of the phylum Chordata comes from this embryonic structure, initially a fluid-filled tube with walls that are onecell thick. The CNS remains a tube in its basic structure, but the lateral walls become thicker and thicker as cells proliferate and differentiate.

Question 36

Notochord:

Answer 36

The cartilaginous rod-like structure located near the dorsal surface of the body of all embryonic chordates. The neural tube forms just dorsal to this structure; in
vertebrates, the vertebrae of the spinal column form around it.

Question 37

The simplest living member of phylum, the Chordata?

Answer 37

Branchiostoma, or amphioxus(“sharp at both ends”)

Question 38

A cephalochordate:

Answer 38

A cephalochordate (from Greek: κεφαλή kephalé, “head” and χορδή khordé, “chord”) is an animal in the chordate subphylum, Cephalochordata, and is defined by the presence of a notochord that persists throughout life.

Question 39

The dorsal nerve cord:

Answer 39

The dorsal nerve cord is the central nervous system in the form of a neural tube, located beneath the surface epithelium along the animal ’ s back. A dorsal nerve cord is found above the cartilaginous notochord.

Question 40

How do peripheral nerves(sensory and motor) connect to the dorsal nerve cord?

Answer 40

The peripheral nerves distribute sensory fibers mostly near the body surface and motor fibers at a deeper position. These nerves enter and exit the tube of the
CNS (the dorsal nerve cord) following, in the main, the “law of roots ” (the Bell-Magendie law) that holds for all vertebrates: Sensory input fibers enter as dorsal roots and axons of motor neurons exit as ventral roots.

Question 41

The findings indicate that most of the neural tube in amphioxus corresponds to …. of vertebrates

Answer 41

the brainstem and spinal cord

Question 42

Are primary brain vesicles present in amphioxus?

Answer 42

yes (Hindbrain, Midbrain, Forebrain)

Question 43

The amphioxus forebrain mostly corresponds to … of vertebrates

Answer 43

‘tweenbrain(diencephalon). There are no cerebral hemispheres, endbrain(may have terminal(innervates nasal septum) and olfactory nerve)