Mammalian Chapter 9

Flatworms have a rudimentary brain consisting of what?

A cluster of nerve cell bodies concentrated in the head, or cephalic region. Two large nerves called nerve cords come off the primitive brain and lead to a nerve network that innervates distal regions of the flatworm body.

Concept check: What is a ganglion? What is the equivalent structure in the CNS?

A cluster of nerve cell bodies outside the CNS. a nucleus.

The cerebrospinal fluid flows

Around the neural tissue and is finally absorbed back into the blood by special villi on the arachnoid membrane in the cranium.

Concept Checks: Name the four kinds of glial cells found in the CNS, and describe the function(s) of each:

Astrocytes, oligodendrocytes, microglia, and ependyma.

What three divisions are obvious at a week 4 human?

Forebrain, midbrain, and a hindbrain. The tube posterior to the hind brain will become the spinal cord. At this stage, the portion of the forebrain that will become the cerebrum is not much larger than the other regions of the brain.

Some ascending tracts...

From the spinal cord pass through the brain stem, while others ascending traces synapse there. Descending tracts from higher brain centers also travel through the brain stem on their way to the spinal cord.

Under normal circumstances what is the only energy source for neurons?

Glucose. Glucose is transported from the plasma across the blood-brain barrier and into the CSF by membrane transporters. It is used directly by neurons for aerobic metabolism. Glucose is also taken up by astrocytes and converted to lactate that neurons can use for ATP production.

The CNS are divided into what?

Gray and white matter.

In vertebrate brain evolution, where is the most dramatic change seen?

In the forebrain region, which includes the cerebrum.

T/F Every single-cell organisms like paramecium are able to carry out the basic tasks of life: finding food, avoiding becoming food, finding a mate?

True.

T/F In all vertebrates the CNS consists of layers of neural tissue surrounding a fluid-filled central cavity lined with epithelium?

True.

What seven major division's are present at birth around week 6?

(1) The cerebrum. (2) The diencephalon. (3) The midbrain. (4) Cerebellum. (5) The pons. (6) The medulla oblongata. (7) Spinal cord.

Concept check: Match each of the following terms with the appropriate neuron type(s). (a) afferent neuron (b) efferent signal (c) integrating center (d) input signal (e) output signal 1. interneuron 2. motor neuron 3. sensory neuron

(a) 3 (b) 2 (c) 1 (d) 3 (e) 2

The three layers of the membrane:

1. The dura matter. 2. The arachnoid membrane. 3. The pia matter.

The cranium has an internal volume of what?

1.4L (1L is occupied by cells while the remaining volume is divided into two distinct extracellular compartments: the blood and the cerebrospinal fluid and the interstitial fluid.

Cranial nerves

12 pairs of nerves that carry messages to and from the brain.

Artificial intelligence

A computer program that attempts to mimic the thought processes of humans.

L-dopa

A drug for Parkinson's disease that contains the precursors to dopamine so that once it is in the brain, it will be converted to dopamine. Is transported across the cells of the blood-brain barrier on an amino acid transporter.

Parkinson disease

A neurological disorder in which brain levels of the neurotransmitter dopamine are too low because dopaminergic neurons are either damaged or dead.

Cerebellum

A region of the hindbrain devoted to coordinating movement and balance. Both birds and humans have great developed cerebellum

What is presumed to be an indicator of the chemical environment in the brain?

A sample of cerebrospinal fluid known as the spinal tap or lumbar puncture is generally done by withdrawing fluid from the subarachnoid space between vertebrae at the lower end of the spinal cord. The presence of proteins or blood cells in cerebrospinal fluid suggests an infection..

Subarachnoid space

A space in the meninges beneath the arachnoid membrane and above the pia mater that contains the cerebrospinal fluid.

Aplysia

A type of shell-less mollusk, to study neural networks and synapse formation because the neurons in these species are 10 times larger than human brain neurons.

Mass of the adult human brain?

About 1400g and contains 85 billion neurons.

The brain is responsible for how much glucose consumption?

About half. The body uses several homeostatic pathways to ensure that glucose concentrations the blood always remain adequate to meet the brains demand.

Why is dopamine administered in a pill or injection considered ineffective?

Because it is unable to cross the blood-brain barrier. (pg. 280)

Why does antihistamines make you sleepy but others do not?

Because the blood-brain barrier excluded many water-soluble substances, but smaller lipid-soluble molecules can diffuse through the cell membrane.

Disruption of blood flow or low levels of oxygen or glucose in the blood can have devastating effects on brain function why?

Because the brain has such a high demand for oxygen that at any moment it is using about one-fifth of the body's oxygen supply.

Concept check: Why is rupturing a blood vessel running between the meninges potentially a surgical emergency?

Blood will collect in the space between the membranes, pushing on the soft brain tissue under the skull. (This is called a subdural hematoma.)

To achieve the protection above most of the 400 miles of blood capillaries create a functional what?

Blood-brain barrier.

What is BRAIN?

Brain research through advancing innovative neurotechnologies.

How does the cerebrospinal protect physically?

By creating a fluid padding that when the brain shakes the fluid will slow it down.

Neural plate

Flat group of cells present in prenatal development that becomes the brain and spinal cord.

What does neural tissue rely on external support?

For protection from trauma. This support comes in the form of an outer casing of bone, three layers of connective tissue membrane, and fluid between the membranes.

How do unicellular organisms coordinate their daily activities?

By using their resting membrane potential that exists in living cells and many of the same ion channels as more complex animals.

Concept check: Is cerebrospinal fluid more like plasma or more like interstitial fluid?

Cerebrospinal fluid is more like interstitial fluid because both these fluids contain little protein and no blood cells.

What do neurons in the nervous system form once linked together?

Circuits that have specific functions.

Ganglia

Clusters of cell bodies in the PNS.

Gray matter...

Consists of unmyelinated nerve cell bodies, dendrites, and axons. The cell bodies are assembled in an organized fashion in both the brain and the spinal cord.

What has artificial intelligence created?

ELIZA which is a "psychiatrist" programmed to respond to typed complaints with comments and suggestions.

Concept check: In the late 1800s, the scientist Paul Ehrlich injected blue dye into the bloodstream of animals. He noticed that all tissues except the brain stained blue. He was not aware of the blood- brain barrier, so what conclusion do you think he drew from his results?

Ehrlich concluded that some property of brain tissue made it resistant to staining by the dye.

T/F The interstitial fluid lie inside the dura matter.

False. It lies in the pia matter.

In vertebrates how is the brain encased?

In a bony skull, or cranium, and the spinal cord runs through a canal in the vertebral column.

Why are brain capillaries so much less permeable than other capillaries?

In most capillaries, leaky cell-cell junctions and pores allow free exchange of solutes between the plasma and interstitial fluid. In brain capillaries, however, the endothelial cells form tight junctions with one another, junctions that prevent solute movement between the cells.

Where is the cerebrospinal fluid found?

In the ventricles and in the space between the pia mater and the arachnoid membrane.

Cerebrospinal fluid (CSF)

Is a salty solution that is continuously secreted but the choroid plexus, a specialized region on the walls of the ventricles.

Arachnoid membrane

Is loosely tied to the inner membrane, leaving a subarachnoid space between the two layers.

White matter...

Is mostly myelinated axons and contains very few neuronal cell bodies. Its pale color comes from the myelin sheaths that surround the axons. Bundles of axons that connect different regions of the CNS are known as tracts. Tracts in the central nervous system are equivalent to nerves in the peripheral nervous system.

The choroid plexus

Is remarkably similar to the kidney tissue and consists of capillaries and a transporting epithelium derived from the ependyma. It selectively pumps sodium and other solutes from plasma into the ventricles.

Dura matter

Is the thickest layer of the membrane and its associated with veins that drain blood from the brain through vessels or cavities called sinuses.

How does the cerebrospinal protect chemically?

It creates a closely regulated extracellular environment for the neurons.

In fish what is the forebrain?

It is a small budge that processes olfactory information about orders in its environment.

How is the forebrain in birds and rodents?

It is enlarged into a cerebrum with a smooth surface.

What is the final layer of protection for the brain?

It's a functional barrier between the interstitial fluid and the blood. This barrier is necessary to isolate the body's main control center from potentially harmful substances in the blood and from blood-borne pathogens such as bacteria.

Cognitive behaviors

Linked to thinking.

Nerve net

Loosely organized network of nerve cells that together allow cnidarians to detect stimuli. They're composed of sensory neurons, connective interneurons, and motor neurons that innervate muscles and glands.

Hypoglycemia

Low blood glucose levels. This can lead to confusion, unconsciousness, and eventually death.

Dopaminergic neurons

Nerve cells that produce the neurotransmitter dopamine.

The CNS like the peripheral nervous system is composed of?

Neurons and supportive girl cells.

Nerves of the peripheral nervous system can enter and leave the spinal cord by passing what?

Notches between the stacked vertebrae.

What are clusters of cell bodies in the brain and spinal cord known as?

Nuclei.

What happens when there is an interruption of blood flow to the brain?

Oxygen will pass freely across the blood-brain barrier to reach neurons and glial cells but if its interrupted, a person loses consciousness in seconds, and the brain damage occurs only a few minutes without oxygen.

Tight junction formation is induced by?

Paracrine signals from adjacent contractile cells called pericytes and from astrocytes whose door processes surround the capillary. As a result, it is the brain tissue itself that create the blood-brain barrier.

What are the toe purpose of the cerebrospinal fluid?

Physical protection and chemical protection. The brain and spinal cord float in the thin layer of fluid between the membranes. The buoyancy of cerebrospinal fluid reduces the weight of the brain nearly fold. Lighter weight translates into less pressure on blood vessels and nerves attached to the CNS.

Spinal reflexes

Reflexes that do not require integration in the brain.

Affective behaviors

Related to feeling and emotion.

What is the consistency of the brain and spinal cord?

Soft and jelly-like.

Hypothalamic-hypophyseal portal system

System that allows releasing hormones from hypothalamus to immediately reach anterior pituitary; blood from capillary bed in hypothalamus flows through a portal vein into the anterior pituitary where it goes into a second capillary network.

Plasticity

The ability to change circuit connections and function in response to sensors input and past experience.

Bony vertebrate

The body segmentation that is characteristic of many invertebrates that can still be seen

What does the vertebrate CNS consist of?

The brain and the spinal cord.

Concept check: In a subsequent experiment, a student of Ehrlich's injected the dye into the cerebrospinal fluid of the same animals. What do you think he observed about staining in the brain and in other body tissues?

The brain stained blue this time, but none of the other body tissues were stained because the dye was unable to cross the blood-brain barrier and enter the bloodstream.

The selective permeability of the blood brain barrier is attributed to its transport properties like what?

The capillary endothelium uses selected membrane carriers and channels to move nutrients and other useful materials from the blood into the brain inter- stitial fluid. Other transporters move wastes from the interstitial fluid into the plasma. Any water-soluble molecule that is not transported on one of these carriers cannot cross the blood-brain barrier.

By week 6...

The central cavity (lumen) of the neural tube has begun to enlarge into the hollow ventricles of the brain. There are two lateral ventricles (the first and second) and two descending ventricles (the third and fourth). The central cavity of the neural tube also becomes the central canal of the spinal cord.

By week 11

The cerebrum is noticeably enlarged, and at birth, the cerebrum is the largest and most obvious structure we see when looking at a human brain. The fully developed cerebrum surrounds the diencephalon, midbrain, and pons, leaving only the cerebellum and medulla oblongata visible below it. Because of the flexion (bending) of the neural tube early in development ,some directional terms have different meanings when applied to the brain

What makes us human?

The cerebrum which is the largest and the most distinctive part of the brain with deep grooves and folds. It allows reasoning and cognition.

What is the final component of the CNS?

The extracellular fluid, which helps fusion the delicate neural tissue,

What does the cerebrum and diencephalon develop from?

The forebrain.

What happens in the areas where the brain lacks a functional blood-brain barrier?

The function of adjacent neurons depends in some way on direct contact with the blood.

Pia matter

The inner membrane which is a thin membrane that adheres to the surface of the brain and spinal cord. Arteries that supply blood to the brain are associated to this layer.

What out of the six divisions of the brain is viewed in profile?

The medulla, cerebellum, and cerebrum. The remaining three divisions (diencephalon, midbrain, and pons) are covered by the cerebrum.

Concept check: Oxidative phosphorylation takes place in which organelle?

The mitochondria.

A 23 day human development means what?

The neural plate cells have fused with each other, creating a neural tube. Neural crest cells from the lateral edges of the neural plate now lie dorsal to the neural tube. The lumen of the neural tube will remain hollow and become the central cavity of the CNS. The cells lining the neural tube will either differentiate into the epithelial ependyma or remain as undifferentiated neural stem cells.

The brain stem

The oldest and most primitive region of the brain and consists of structures that derive from the embryonic midbrain and hindbrain. The brain stem can be divided into white matter and gray matter, and in some ways, its anatomy is similar to that of the spinal cord.

What is the major pathway for information flowing back and fourth between the brain, skin, joints, and the muscles of the body?

The spinal cord.

Concept check: Name the two metabolic pathways for aerobic metabolism of glucose. What happens to NADH produced in these pathways?

The two pathways are glycolysis and the citric acid cycle. Glucose is metabolized to pyruvate through glycolysis and then enters the citric acid cycle. NADH2 passes high-energy electrons to the electron transport system for ATP synthesis.

What happens if the spinal cord is severed?

There is loss of sensation from the skin and muscles as well as paralysis, loss of the ability to voluntarily control muscles.

Vomiting center in the medulla oblongata

These neurons monitor the blood for possibly toxic foreign substances, such as drugs. If they sense something harmful, they initiate a vomiting reflex. Vomiting removes the contents of the digestive system and helps eliminate ingested toxins.

How do neurons supply a constant supply of oxygen and glucose to make ATP for active transport?

These substrates, about 15% of the blood pumped by the heart goes to the brain and is distributed through the extensive cerebellum vascular system.

Once neurons have access to l-dopa in the interstitial fluid what happens?

They metabolize it to dopamine, thereby allowing the deficiency to be treated.

Meninges

Three protective membranes that surround the brain and spinal cord. They help stabilize the neural tissue and protect from bruising against the bones of the skeleton.

Peripheral nerves are equivalent to what organizational structure in the CNS?

Tracts.

T/F Annelids and higher invertebrates have complex reflexes controlled through neural networks.

True.

Concept check: When H+ concentration increases, pH decreases, which means CSF pH must be lower than blood pH (more acidic).

When H+ concentration increases, pH decreases, which means CSF pH must be lower than blood pH (more acidic)