Module 3

Question 1

One way to think about, and perhaps simplify, the field of (neuro)anatomy is to divide it into sub-sections, such as: Gross (Neuro)Anatomy and Cellular (Neuro)Anatomy.

Define each of these terms.

Answer 1

Gross (Neuro)Anatomy: The gross, overall structure of the nervous system; its main parts, their arrangement and connections.

Cellular Neuro(Anatomy): The detailed, microscopic structure of the cellular (neuron, glia) and intracellular components that form the nervous system.

Question 2

Describing the appearance and localization of the gyri of the human brain is part of

a) gross neuroanatomy

b) functional neuroanatomy

c) cellular neuroanatomy

d) all of the above

Answer 2

a) gross neuroanatomy

Question 3

The field of neuroanatomy started with the anatomical studies conducted by…

a) Camillo Golgi

b) Hans Dringenberg

c) Zacharias Janssen

d) George Humphrey

e) none of the above

Answer 3

e) none of the above

Question 4

Which of the following inventions revolutionized the field of neuroanatomy?

a) the microscope

b) the Golgi stain

c) electron microscopy

d) all of the above

Answer 4

d) all of the above

Question 5

Ramón y Cajal was…

a) a proponent of the neuron doctrine

b) a supporter of the reticular theory

c) the inventor of the “black reaction”

d) the inventor of electron microscopy

Answer 5

a) a proponent of the neuron doctrine

Question 6

What are Pyramidal cells?

Answer 6

Pyramidal cells are one of the major cell types found throughout the cerebral cortex.

Question 7

What are dendritic spines?

Answer 7

The tiny black protrusions that cover the dendrite and that are the sites of synaptic inputs to the neuron.

Question 8

One of the major cells types in the cortex are:

a) interform cells

b)fusiform cells

c) circular cells

d) pyramidal cells

Answer 8

d) pyramidal cells

Question 9

Environmental enrichment increases:

a) cortex weight

b) corpus callosum thickness

c) dendritic length and branching

d) spine density

e) all of the above

Answer 9

e) all of the above

Question 10

Enrichment can involve:

a) increased social interactions

b) increased physical activity

c) increased exploration

d) increased sensory stimulation

e) all of the above

Answer 10

e) all of the above

Question 11

Enrichment improves cognitive performance

a) only in in young animals

b) only in old animals

c) most dramatically in young animals

d) most dramatically in old animals

Answer 11

d) most dramatically in old animals

Question 12

True or False?

High levels of chronic stress actively impair the brain.

Answer 12

True.

e.g., by causing neuronal atrophy or, in extreme cases, neuronal death.

Question 13

Some characteristics of enriched environments include…

a) high levels of chronic stress

b) carrying out routines

c) cognitive demands

d) comfort and reduced physical activity

Answer 13

c) cognitive demands

Question 14

Stress and impoverished environments have…

a) Similar effects on brain anatomy

b) opposing effects on brain anatomy

c) no effects on brain anatomy

d) positive effects on brain anatomy

Answer 14

a) Similar effects on brain anatomy

Question 15

Which of the following have been associated with living in a residential school?

a) eating disorders

b) insomnia

c) emotional abuse

d) drug abuse

e) all of the above

Answer 15

e) all of the above

Question 16

Who is credited with the invention of the microscope in the 16th century?

Answer 16

Zacharias Janssen

(but there seems to be some debate about this claim)

Question 17

The vertebrate nervous system is composed of what two divisions?

Answer 17

The central nervous system and the peripheral nervous system.

Question 18

Roughly speaking, the central nervous system (CNS) is the division of the nervous system located _______ the skull and spine, and the peripheral nervous system (PNS) is the division located ________ the skull and spine.

Answer 18

within, outside

Question 19

The central nervous system is composed of what two divisions?

Answer 19

The brain and the spinal cord.

Question 20

The peripheral nervous system is composed of what two divisions?

Answer 20

The somatic nervous system and the autonomic nervous system.

Question 21

What is the somatic nervous system (SNS)?

Answer 21

The part of the PNS that interacts with the external environment. It is composed of afferent nerves that carry sensory signals from the skin, skeletal muscles, joints, eyes, ears, and so on, to the central nervous system and efferent nerves that carry motor signals from the central nervous system to the skeletal muscles.

Question 22

What is the autonomic nervous system (ANS?) i

Answer 22

The part of the peripheral nervous system that regulates the body’s internal environment. It is composed of afferent nerves that carry sensory signals from internal organs to the CNS and efferent nerves that carry motor signals from the CNS to internal organs.

Question 23

What is a good way to remember the difference between afferent and efferent?

Answer 23

Many words that involve the idea of going toward something—in this case, going toward the CNS—begin with an a (e.g., advance, approach, arrive)

Many words that involve the idea of going away from something begin with an e (e.g., exit, embark, escape).

Question 24

The autonomic nervous system has two kinds of efferent nerves. What are they and what do they do? :

Answer 24

1) Sympathetic nerves - autonomic motor nerves that project from the CNS in the lumbar (small of the back) and thoracic (chest area) regions of the spinal cord.

2) Parasympathetic nerves - autonomic motor nerves that project from the brain and sacral (lower back) region of the spinal cord.

Question 25

All sympathetic and parasympathetic nerves are two-stage neural paths: The sympathetic and parasympathetic neurons project from the CNS and go only part of the way to the target organs before they synapse on other neurons (second-stage neurons) that carry the signals the rest of the way.

But how do sympathetic and parasympathetic systems differ at this stage?

Answer 25

The sympathetic neurons project from the CNS synapse on second-stage neurons at a substantial distance from their target organs,

whereas the parasympathetic neurons project from the CNS synapse near their target organs on very short second-stage neurons.

Question 26

The conventional view of the respective functions of the sympathetic and parasympathetic systems stresses what three important principles?

Answer 26

(1) sympathetic nerves stimulate, organize, and mobilize energy resources in threatening situations, whereas parasympathetic nerves act to conserve energy;

(2) each autonomic target organ receives opposing sympathetic and parasympathetic input, and its activity is thus controlled by relative levels of sympathetic and parasympathetic activity; and

(3) sympathetic changes are indicative of psychological arousal, whereas parasympathetic changes are indicative of psychological relaxation.

Question 27

Most of the nerves of the peripheral nervous system project from the spinal cord, but there are 12 pairs of exceptions: the 12 pairs of _______ nerves, which project from the brain.

Answer 27

cranial

(They are numbered in sequence from front to back. The cranial nerves include purely sensory nerves such as the olfactory nerves (I) and the optic nerves (II), but most contain both sensory and motor fibers. The longest cranial nerves are the vagus nerves (X), which contain motor and sensory fibers traveling to and from the gut.)

Question 28

The autonomic motor fibers of the cranial nerves are:

a) parasympathetic

b) sympathetic

Answer 28

a) parasympathetic

(See page 74 for further explanation)

Question 29

Because the functions and locations of the cranial nerves are _________, disruptions of particular cranial nerve functions provide excellent clues about the location and extent of tumors and other kinds of brain pathology.

Answer 29

specific

(Thus the functions of the various cranial nerves are commonly assessed by neurologists as a basis for diagnosis.)

Question 30

What are the 2 most protected organs in the body?

Answer 30

The brain and spinal cord (the CNS).

(They are encased in bone and covered by three protective membranes, the three meninges.)

Question 31

What are the 3 meninges and their functional roles?

Answer 31

1) Dura mater - The outer meninx is a tough membrane called the dura mater (tough mother). (Contains blood vessels and nerves, attaches to the cranial cavity, surrounds spinal cord.)

2) Arachnoid membrane - Immediately inside the dura mater is the fine arachnoid membrane (spider-web-like membrane). Thin, no blood vessels, below dura.

3) Pia Mater - The innermost meninx, the delicate pia mater (pious mother), which adheres to the surface of the CNS. (Contains nerves and blood vessels, attaches to brain and spinal cord.)

Question 32

What is the subarachnoid space?

Answer 32

Beneath the arachnoid membrane is a space called the subarachnoid space, which contains many large blood vessels and cerebrospinal fluid.

Question 33

Also protecting the CNS is the _________ fluid (CSF), which fills the subarachnoid space, the central canal of the spinal cord, and the cerebral ventricles of the brain.

Answer 33

cerebrospinal

(The cerebrospinal fluid supports and cushions the brain. Patients who have had some of their cerebrospinal fluid drained away often suffer raging headaches and experience stabbing pain each time they jerk their heads.)

Question 34

What is the term for the small central channel that runs the length of the spinal cord?

Answer 34

The central canal.

Question 35

What are the cerebral ventricles?

Answer 35

They are the four large internal chambers of the brain: the two lateral ventricles, the third ventricle, and the fourth ventricle.

Question 36

True or False?

The subarachnoid space, central canal, and cerebral ventricles are interconnected by a series of openings and thus form a single reservoir.

Answer 36

True.

Question 37

What produces cerebrospinal fluid?

Answer 37

Choroid plexuses (networks of capillaries, or small blood vessels that protrude into the ventricles from the pia mater.)

Question 38

Excess cerebrospinal fluid is continuously absorbed from the subarachnoid space into large blood-filled spaces, or _________, which run through the dura mater and drain into the large jugular veins of the neck.

Answer 38

dural sinuses

Question 39

True or False?

Hydrocephalus is often congenital (present from birth).

Answer 39

True.

Question 40

How does the condition called hydrocephalus (water head) develop?

Answer 40

Occasionally, the flow of cerebrospinal fluid is blocked by a tumor near one of the narrow channels that link the ventricles—for example, near the cerebral aqueduct, which connects the third and fourth ventricles. The resulting buildup of fluid in the ventricles causes the walls of the ventricles, and thus the entire brain, to expand.

Question 41

What is the blood–brain barrier?

Answer 41

A mechanism that impedes the passage of many toxic substances from the blood into the brain. This barrier is a consequence of the special structure of cerebral blood vessels.

In the rest of the body, the cells that compose the walls of blood vessels are loosely packed (most molecules pass readily through them into surrounding tissue). In the brain, however, the cells of the blood vessel walls are tightly packed, thus forming a barrier to the passage of many molecules—particularly proteins and other large molecules.

Question 42

True or False?

The blood–brain barrier impedes the passage of all large molecules.

Answer 42

False.

The blood–brain barrier DOES NOT impede the passage of all large molecules. Some large molecules that are critical for normal brain function (e.g., glucose) are actively transported through cerebral blood vessel walls. Also, the blood vessel walls in some areas of the brain allow certain large molecules to pass through them unimpeded. Many CNS disorders are associated with impairment of the blood–brain barrier.

Question 43

The somatic nervous system includes _______ nerves that carry motor signals from the central nervous system to the muscles.

Answer 43

efferent

Question 44

The _______ is the part of the peripheral nervous system that regulates the body’s internal environment.

Answer 44

ANS

Question 45

The brain and the spinal cord are the only organs that are protected with three layers of protective membranes called _______.

Answer 45

meninges

Question 46

_______ or “tough mother” is the outer meninx.

Answer 46

Dura mater.

Question 47

The _______ nervous system is activated when you encounter a threatening information such as a bear
attacking you. This system is essential for the initiation of fight-or-flight responses.

Answer 47

sympathetic

Question 48

Motor nerves that project from the brain and
the lower region of the spine are called _______ nerves.

Answer 48

parasympathetic

Question 49

The _______ nerve is a purely sensory nerve that transfers visual information from the retina of the eye to the brain.

Answer 49

optic

Question 50

The _______ nerve is the nerve cell that extends directly from the brain to the gut.

Answer 50

vagus

Question 51

The _______ is a channel that connects the third and fourth ventricles in the brain.

Answer 51

cerebral aqueduct

Question 52

The ventricles of patients with a congenital condition called _______ build up fluid as a result of blocked channels in the brain.

Answer 52

hydrocephalus

Question 53

Many toxic substances that are present in the bloodstream are prohibited from entering the brain by a mechanism called the _______ where cells of blood vessel walls are tightly packed, forming a barrier to the passage of large proteins.

Answer 53

blood–brain barrier

Question 54

Unlike large toxic molecules, _______, which is critical for the function of the brain, is actively transported through the vessel walls.

Answer 54

glucose

Question 55

__________ are cells that are specialized for the reception, conduction, and transmission of electrochemical signals.

Answer 55

Neurons

Question 56

The neuron cell membrane is composed of a lipid bilayer, or two layers of fat molecules. Embedded in the lipid bilayer are numerous protein molecules that are the basis of many of the cell membrane’s functional properties. What are 2 types of membrane proteins?

Answer 56

channel proteins - through which certain molecules can pass; others are

signal proteins - which transfer a signal to the inside of the neuron when particular molecules bind to them on the outside of the membrane.

Question 57

What are the 4 classes of neurons?

Answer 57

Multipolar - A neuron with more than two processes extending from its cell body. (Most neurons are multipolar.)

Unipolar - A neuron with one process extending from its cell body.

Bipolar - A neuron with two processes extending from its cell body.

Interneurons - Neurons with a short axon or no axon at all. (Their function is to integrate neural activity within a single brain structure, not to conduct signals from one structure to another.)

Question 58

There are two kinds of gross neural structures in the nervous system: those composed primarily of _________ and those composed primarily of _________.

Answer 58

cell bodies, axons

Question 59

In the central nervous system, clusters of cell bodies are called ________ (singular nucleus); in the peripheral nervous system, they are called _______ (singular ganglion).

Answer 59

nuclei, ganglia

Question 60

True or False?

The word nucleus has two different neuroanatomical meanings.

Answer 60

True.

It is a structure in the neuron cell body and a cluster of cell bodies in the CNS.

Question 61

In the central nervous system, bundles of axons are called _______; in the peripheral nervous system, they are called __________.

Answer 61

tracts, nerves

Question 62

Neurons are not the only cells in the nervous system; there are about as many ______ cells.

Answer 62

glial cells (or glia).

Question 63

True or False?

There are 10 times as many glia as neurons in the human brain.

Answer 63

False.

There are roughly two glia for every three neurons in your brain.

Question 64

What are the 4 classes of glia and their functions?

Answer 64

1) Oligodendrocytes - glial cells with extensions that wrap around the axons of some neurons of the central nervous system. These extensions are rich in myelin, a fatty insulating substance, and the myelin sheaths they form increase the speed of axonal conduction.

2) Schwann cells - they perform a similar function to oligodendrocytes in the peripheral nervous system. But each Schwann cell constitutes one myelin segment, whereas each oligodendrocyte provides several myelin segments, often on more than one axon.

3) Microglia - are smaller than other glial cells. They respond to injury or disease by multiplying, engulfing cellular debris or even entire cells and triggering inflammatory responses.

4) Astrocytes - the largest glial cells (they’re star shaped). The extensions of some astrocytes cover the outer surfaces of blood vessels that course through the brain; they also make contact with neurons. These particular astrocytes appear to play a role in allowing the passage of some chemicals from the blood into CNS neurons and in blocking other chemicals, and they have the ability to contract or relax blood vessels based on the blood flow demands of particular brain regions.

Question 65

What are 2 differences between Schwann cells and oligodendrocytes?

Answer 65

1) Each Schwann cell constitutes one myelin segment, whereas each oligodendrocyte provides several myelin segments, often on more than one axon.

2) Only Schwann cells can guide axonal regeneration (regrowth) after damage. That is why effective axonal regeneration in the mammalian nervous system is restricted to the PNS.

Question 65

For decades, it was assumed that the function of glia was mainly to provide support for neurons—provide them with nutrition, clear waste, and form a physical matrix to hold neural circuits together (glia means “glue”). But why has this limited view of the role of glial cells changed?

Answer 65

Due to a series of remarkable findings. For example”

1) Astrocytes have been shown to exchange chemical signals with neurons and other astrocytes, to control the establishment and maintenance of synapses between neurons, to modulate neural activity, to form functional networks with neurons and other astrocytes, to control the blood–brain barrier, to respond to brain injury, and to play a role in certain forms of cognition.

2) Microglia have been shown to play a role in the regulation of cell death, synapse formation, and synapse elimination.

3) Some researchers have suggested that glial net- works may be the dwelling places of thoughts. One final important discovery about glial cells is that they are much more varied than implied by the four types that we have just described: oligodendrocytes, Schwann cells, microglia, and astrocytes. For example, a new type of glial cell was recently discovered; and at least fifteen different kinds of astrocytes have been identified, each with its own structure, physiology, and specific locations in the brain .

Question 65

What are the most studied class of glial cells?

Answer 65

Astrocytes.

Question 66

What is the major problem in visualizing neurons?

Answer 66

Neurons are so tightly packed and their axons and dendrites so intricately intertwined that looking through a microscope at unprepared neural tissue reveals almost nothing about them.

Question 67

The key to the study of neuroanatomy lies in preparing neural tissue in a variety of ways to permit a clear view of a different aspect of neuronal structure. What are the most widely used neuroanatomical techniques to do this?

Answer 67

1) Golgi Stain - Golgi was trying to stain the meninges, by exposing a block of neural tissue to potassium dichromate and silver nitrate, when he noticed the silver chromate created by the chemical reaction of the two substances invaded a few neurons in each slice of tissue and stained each invaded neuron entirely black. This discovery made it possible to see individual neurons for the first time, although only in silhouette. Golgi stains are commonly used to discover the overall shape of neurons.

2) Nissl Stain - Unlike the Golgi stain, this method provides indication of the number of neurons in an area, using cresyl violet or other dyes that penetrate all cells on a slide, but they bind to molecules (i.e., DNA and RNA) that are most prevalent in neuron cell bodies. they often are used to estimate the number of cell bodies in an area, by counting the number of Nissl-stained dots.

3) Electron microscopy - A neuroanatomical technique that provides information about the details of neuronal structure. The limit of magnification in light microscopy is about 1,500 times, which doesn’t reveal fine anatomical details of neurons. Greater detail can be obtained by first coating thin slices of neural tissue with an electron-absorbing substance that is taken up by different parts of neurons to different degrees, then passing a beam of electrons through the tissue onto a photographic film. The result is an electron micrograph, which captures neuronal structure in exquisite detail. Because the images are so detailed, they can make it difficult to visualize general aspects of neuroanatomical structure.

4) Neuroanatomical tracing techniques - 2 types:

Anterograde (forward) - used when an investigator wants to trace the paths of axons projecting away from cell bodies located in a particular area. They inject one of several chemicals into the cell body. It is then taken up by cell bodies and transported forward along their axons to their terminal buttons. Then, after a few days, the investigator removes the brain and slices it. Those slices are then treated to reveal the locations of the injected chemical.

Retrograde (backward) - used when an investigator wants to trace the paths of axons projecting into a particular area. They inject one of several chemicals into an area of the brain. These chemicals are taken up by terminal buttons and then transported backward along their axons to their cell bodies. After a few days, the investigator removes the brain and slices it. Those slices are then treated to reveal the locations of the injected chemical.

Question 68

Directions in the vertebrate nervous system are described in relation to the orientation of the __________.

Answer 68

spinal cord.

Question 69

Describe the following neuroanatomical
directions:

1) anterior

2) posterior

Answer 69

anterior = toward the nose end (the anterior end), and

posterior = toward the tail end (the posterior end);

(these same directions are sometimes referred to as rostral and caudal, respectively.)

Question 70

Describe the following neuroanatomical
directions:

1) dorsal

2) ventral

Answer 70

dorsal = toward the surface of the back or the top of the head (the dorsal surface).

ventral = toward the surface of the chest or the bottom of the head (the ventral surface).

Question 71

Describe the following neuroanatomical
directions:

1) medial

2) lateral

Answer 71

medial = toward the midline of the body.

lateral = away from the midline toward the body’s lateral surfaces.

Question 72

Humans complicate the simple three-axis (anterior– posterior, ventral–dorsal, medial–lateral) system of neuroanatomical directions by insisting on walking around on our hind legs. This changes the orientation of our cerebral hemispheres in relation to our spines and brain stems. What is a good way to envision this to make it less confusing?

Answer 72

Remember that the system of vertebrate neuroanatomical directions was adapted for use in humans in such a way that the terms used to describe the positions of various body surfaces are the same in humans as they are in more typical, non-upright vertebrates. (So almost picture the human down on 4 legs, like a cat or dog). Specifically, notice that the top of the human head and the back of the human body are both referred to as dorsal even though they are in different directions, and the bottom of the human head and the front of the human body are both referred to as ventral even though they are in different directions . To circumvent this complication, the terms superior and inferior are often used to refer to the top and bottom of the primate head, respectively.

See Figure 3.15 on page 84 for a good diagram/way to visualize this.

Question 73

What do proximal and distal mean?

Answer 73

Close & Far.

Ie: Regarding the peripheral nervous system, proximal means closer to the CNS, and distal means farther from the CNS. Your shoulders are proximal to your elbows, and your elbows are proximal to your fingers.

Question 74

Sections (slices) of the brain are usually cut in one of what three different planes?

Answer 74

1) horizontal sections

2) frontal sections (also termed coronal sections), and

3) sagittal sections.

(A section cut down the center of the brain, between the two hemispheres, is called a midsagittal section. A section cut at a right angle to any long, narrow structure, such as the spinal cord or a nerve, is called a cross section.)

Question 75

Note to self: come back here and add the “scan your brain” matching activity on page 85.

Question 76

The spinal cord comprises what two areas?

Answer 76

1) A inner H-shaped core of gray matter (gray matter is composed largely of cell bodies and unmyelinated interneurons)

2) A surrounding area of white matter (white matter is composed largely of myelinated axons. (It is the myelin that gives the white matter its glossy white sheen.)

Question 77

The two dorsal arms of the spinal gray matter are called the _________, and the two ventral arms are called the __________.

Answer 77

dorsal horns

ventral horns

Question 78

Pairs of spinal nerves are attached to the spinal cord— one on the left and one on the right—at 31 different levels of the spine. Each of these 62 spinal nerves divides as it nears the cord, and its axons are joined to the cord via one of two roots: the ______ root or the ______ root.

Answer 78

dorsal , ventral

Question 79

All dorsal root axons, whether somatic or autonomic, are ___________ (afferent) unipolar neurons with their cell bodies grouped together just outside the cord to form the dorsal root ganglia.

Answer 79

sensory

(many of their synaptic terminals are in the dorsal horns of the spinal gray matter.)

Question 80

The neurons of the ventral root are _________ (efferent) multipolar neurons with their cell bodies in the ventral horns.

Answer 80

motor

(Those that are part of the somatic nervous system project to skeletal muscles; those that are part of the autonomic nervous system proj- ect to ganglia, where they synapse on neurons that in turn project to internal organs (heart, stomach, liver, etc.).

Question 81

In the vertebrate embryo, the tissue that eventually develops into the CNS is recognizable as a fluid-filled tube. The first indications of the developing brain are three swellings that occur at the anterior end of this tube. These three swellings eventually develop into the adult __________, ______________ and ________________.

Answer 81

forebrain, midbrain, and hindbrain.

Question 82

Before birth, the initial three swellings in the neural tube become five. List the five major divisions of the human brain.

Answer 82

1) Telencephalon (the left and right cerebral hemispheres)

2) Diencephalon,

3) Mesencephalon (or midbrain)

4) Metencephalon,

5) Myelencephalon (or medulla)

(Remember their order by thinking that the Telencephalon is on the Top and the other four divisions are arrayed below it in alphabetical order.)

Question 83

What does “encephalon” translate to?

Answer 83

It mean “within the head”.

Question 84

Before birth, the initial three swellings in the neural tube become five. Why does this occur?

Answer 84

This occurs because the forebrain swelling grows into two different swellings, and so does the hindbrain swelling.

Question 85

Which of the five major divisions of the human brain undergoes the greatest growth during development?

Answer 85

The telencephalon (the left and right cerebral hemispheres).

(The other four divisions of the brain are often referred to collectively as the brain stem—the stem on which the cerebral hemispheres sit.)

Question 86

List and describe the components of the myelencephalon.

Answer 86

-Composed largely of tracts carrying signals between the rest of the brain and the body.

-It has a reticular formation - a complex network of about 100 tiny nuclei that occupies the central core of the brain stem from the posterior boundary of the myelencephalon to the anterior boundary of the midbrain. These nuclei of the reticular formation are involved in a variety of functions—including sleep, attention, movement, the maintenance of muscle tone, and various cardiac, circulatory, and respiratory reflexes.

Question 87

List and describe the components of the metencephalon.

Answer 87

-Like the myelencephalon, houses many ascending and descending tracts and part of the reticular formation. These structures create a bulge, called the pons, on the brain stem’s ventral surface. The pons is one major division of the metencephalon; the other is the cerebellum (little brain).

-The cerebellum is the large, convoluted structure on the brain stem’s dorsal surface. It is an important sensorimotor structure; cerebellar damage eliminates the ability to precisely control one’s movements and to adapt them to changing conditions. However, the fact that cerebellar damage also produces a variety of cognitive deficits (e.g., deficits in decision making and in the use of language) suggests that the functions of the cerebellum are not restricted to sensorimotor control.

Question 88

List and describe the components of the mesencephalon.

Answer 88

-It has two divisions: the tectum and the tegmentum

-The tectum (roof) is the dorsal surface of the midbrain. In mammals, the tectum is composed of two pairs of bumps, the colliculi (little hills). The posterior pair, called the inferior colliculi, have an auditory function. The anterior pair, called the superior colliculi, have a visual-motor function; more specifically, to direct the body’s orientation toward or away from particular visual stimuli. In lower vertebrates, the function of the tectum is entirely visual-motor, and it is sometimes referred to as the optic tectum.

• The tegmentum is the division of the mesencephalon ventral to the tectum. In addition to the reticular formation and tracts of passage, the tegmentum contains three colorful structures: the periaqueductal gray, the substantia nigra, and the red nucleus.

(The periaqueductal gray is the gray matter situated around the cerebral aqueduct, the duct connecting the third and fourth ventricles; it is of special interest because of its role in mediating the analgesic (pain-reducing) effects of opioid drugs. The substantia nigra (black substance) and the red nucleus are both important components of the sensorimotor system.)

Question 89

List and describe the components of the diencephalon.

Answer 89

-Composed of two structures: the thalamus and the hypothalamus.

-The thalamus is the large, two-lobed structure that constitutes the top of the brain stem. One lobe sits on each side of the third ventricle, and the two lobes are joined by the massa intermedia, which runs through the ventricle. Visible on the surface of the thalamus are white lamina (layers) that are composed of myelinated axons. The thalamus comprises many different pairs of nuclei, most of which project to the cortex.

-The hypothalamus is located just below the anterior thalamus (hypo means “below”). It plays an important role in the regulation of several motivated behaviors (e.g., eating, sleep, and sexual behavior). It exerts its effects in part by regulating the release of hormones from the pituitary gland, which dangles from it on the ventral surface of the brain.
2 other structures appear on the inferior surface of the hypothalamus: the optic chiasm and the mammillary bodies. The optic chiasm is the point at which the optic nerves from each eye come together and then decussate (cross over to the other side of the brain). The decussating fibers are said to be contralateral (projecting from one side of the body to the other), and the nondecussating fibers are said to be ipsilateral (staying on the same side of the body). The mammillary bodies are a pair of spherical nuclei located on the inferior surface of the hypothalamus, just behind the pituitary.

Question 90

The most well-understood thalamic nuclei are the __________ relay nuclei.

Answer 90

sensory.

They receive signals from sensory receptors, process them, and then transmit them to the appropriate areas of sensory cortex. For example, the lateral geniculate nuclei, the medial geniculate nuclei, and the ventral posterior nuclei are important relay stations in the visual, auditory, and somatosensory systems, respectively.

Sensory relay nuclei are not one- way streets; they all receive feedback signals from the very areas of cortex to which they project. Although less is known about the other thalamic nuclei, the majority of them receive input from areas of the cortex and project to other areas of the cortex.

Question 91

True or False?

The pituitary gland is the main source of nasal mucus.

Answer 91

False.

The literal meaning of pituitary gland is “snot gland”; it was first discovered in a gelatinous state behind the nose of a cadaver and was incorrectly assumed to be the main source of nasal mucus.

Question 92

List and describe the components of the telencephalon.

Answer 92

-It mediates the brain’s most complex functions. It initiates voluntary movement, interprets sensory input, and mediates complex cognitive processes such as learning, speaking, and problem solving.

-The cerebral hemispheres are covered by a layer of tissue called the cerebral cortex (cerebral bark). Because the cerebral cortex is mainly composed of small, unmyelinated neurons, it is gray and is often referred to as the gray matter. In contrast, the layer beneath the cortex is mainly composed of large myelinated axons, which are white and often referred to as the white matter.

-the cerebral hemispheres are almost completely separated by the largest of the fissures: the longitudinal fissure. The cerebral hemispheres are directly connected by a few tracts spanning the longitudinal fissure; called cerebral commissures. The largest cerebral commissure, the corpus callosum.

-the two major landmarks on the lateral surface of each hemisphere are the central fissure and the lateral fissure. These fissures partially divide each hemisphere into four lobes: the frontal lobe, the parietal lobe, the temporal lobe, and the occipital lobe. Among the largest gyri are the precentral gyri, the postcentral gyri, and the superior temporal gyri in the frontal, parietal, and temporal lobes, respectively.

Question 93

True or False?

All mammals have convoluted cortexes.

Answer 93

False.

Not all mammals have convoluted cortexes; most mammals are lissencephalic (smooth-brained).
It was once believed that the number and size of cortical convolutions determined a species’ intellectual capacities; however, the number and size of cortical convolutions appear to be related more to body size. Every large mammal has an extremely convoluted cortex.

Ps: convoluted = furrowed. In humans, the the cerebral cortex is deeply convoluted. The convolutions have the effect of increasing the amount of cerebral cortex without increasing the overall volume of the brain.

Question 94

The large furrows in a convoluted cortex are called _______, and the small ones are called _______.

Answer 94

fissures, sulci

(The ridges between fissures and sulci are called gyri.)

Question 95

True or False?

The cerebral lobes are not functional units.

Answer 95

True.

It is best to think of the cerebral cortex as a flat sheet of cells that just happens to be divided into lobes because it folds in on itself at certain places during development. Thus, it is incorrect to think that a lobe is a functional unit, having one set of functions.

Question 96

What is the main function of the occipital lobes? is quite straightforward:

Answer 96

We humans rely heavily on the analysis of visual input to guide our behavior, and the occipital cortex and large areas of adjacent cortex perform this function.

Question 97

What are the two large functional areas in each parietal lobe?

Answer 97

1) The postcentral gyrus - analyzes sensations from the body (e.g., touch),

2) The remaining areas of cortex in the posterior parts of the parietal lobes play roles in perceiving the location of both objects and our own bodies and in directing our attention.

Question 98

The cortex of each temporal lobe has what three general functional areas?

Answer 98

1) The superior temporal gyrus is involved in hearing and language,

2) the inferior temporal cortex identifies complex visual patterns

3) the medial portion of temporal cortex (which is not visible from the usual side view) is important for certain kinds of memory.

Question 99

Each frontal lobe has what two distinct functional areas?

Answer 99

1) The precentral gyrus and adjacent frontal cortex have a motor function,

2) The frontal cortex anterior to motor cortex performs complex cognitive functions, such as planning response sequences, evaluating the outcomes of potential patterns of behavior, and assess- ing the significance of the behavior of others

Question 100

About 90 percent of human cerebral cortex is _______, also known as isocortex.

Answer 100

neocortex (new cortex)

Question 101

What are 4 important characteristics of neocortical anatomy?

Answer 101

1) Many cortical neurons fall into one of two different categories: pyramidal (pyramid-shaped) cells and stellate (star-shaped) cells. Pyramidal cells are large multipolar neurons with pyramid-shaped cell bodies, a large dendrite called an apical dendrite that extends from the apex of the pyramid straight toward the cor- tex surface, and a very long axon. Stellate cells are small star-shaped interneurons (neurons with a short axon or no axon).

2) The six layers of neocortex differ from one another in terms of the size and density of their cell bodies and the relative proportion of pyramidal and stellate cell bodies that they contain.

3) Many long axons and dendrites course vertically (i.e., at right angles to the cortical layers) through the neocortex. This vertical flow of information is the basis of the neocortex’s columnar organization: Neurons in a given vertical column of neocortex often form a mini-circuit that performs a single function.

4) Although neocortex is six-layered, there are variations in the thickness of the respective layers from area to area.

Question 102

What is the hippocampus and where is it located?

Answer 102

It’s one important area of cortex that is not neocortex—it has only three major layers. The hippocampus is located at the medial edge of the cerebral cortex as it folds back on itself in the medial temporal lobe. This folding produces a shape that is, in cross section, somewhat reminiscent of a seahorse (hippocampus means “sea horse”). The hippocampus plays a major role in some kinds of memory.

Question 103

Although much of the subcortical portion of the telencephalon is taken up by axons project- ing to and from the neocortex, there are several large subcortical nuclear groups. Some of them are considered part of either the _______ system or the _________ system.

Answer 103

limbic, basal ganglia

(Don’t be misled by the word system in these contexts; it implies a level of certainty that is unwarranted. It is not entirely clear exactly what these hypothetical systems do, exactly which structures should be included in them, or even whether it is appropriate to view them as unitary systems.)

Question 104

List and describe the components
of the limbic system.

Answer 104

• a circuit of midline structures that circle the thalamus (limbic means “ring”). The limbic system is involved in the regulation of motivated behaviors—including the four F’s of motivation: fleeing, feeding, fighting, and sexual behavior.

-In addition to the structures about which you have already read (the mammillary bodies and the hippocampus), major structures of the limbic system include the amygdala, the fornix, the cingulate cortex, and the septum.

-amygdala = the almond-shaped nucleus in the anterior temporal lobe. Posterior to the amygdala is the hippocampus, which runs beneath the thalamus in the medial temporal lobe. Next in the ring are the cingulate cortex and the fornix:

-Cingulate cortex = the large strip of cortex in the cingulate gyrus on the medial surface of the cerebral hemispheres, just superior to the corpus callosum; it encircles the dorsal thalamus.

-The fornix = the major tract of the limbic system, also encircles the dorsal thalamus; it leaves the dorsal end of the hippocampus and sweeps forward in an arc coursing along the superior surface of the third ventricle and terminating in the septum and the mammillary bodies (fornix means “arc”).

-The septum = a midline nucleus located at the anterior tip of the cingulate cortex. Several tracts connect the septum and mammillary bodies with the amygdala and hippocampus, thereby completing the limbic ring.

Question 105

List and describe the components
of the basal ganglia.

Answer 105

• The long tail-like caudate and putamen receive inputs from the neocortex. Together, the caudate and putamen, which both have a striped appearance, are known as the striatum. The striatum’s major output is to a pale circular structure known as the globus pallidus. The globus pallidus is located medial to the putamen between the putamen and the thalamus.

-The basal ganglia play a role in the performance of voluntary motor responses and decision making. Of particular interest is a pathway that projects to the striatum from the substantia nigra of the midbrain: Parkinson’s disease, a disorder characterized by rigidity, tremors, and poverty of voluntary move- ment, is associated with the deterioration of this pathway.

-Another part of the basal ganglia that is of particular interest to biopsychologists is the nucleus accumbens, which is in the medial portion of the ventral striatum. The nucleus accumbens is thought to play a role in the rewarding effects of addictive drugs and other reinforcers.

Question 106

Go to page 96 in the textbook and label the brain.