Lecture 9

Question 1

Nervous System

Answer 1

Consists of all the nerve cells. It is the body’s speedy, electrochemical communication system

Question 2

What is the central Nervous System (CNS) comprised of

Answer 2

Composed of the brain and spinal cord.
The CNS is the processing center of the body

Question 3

Peripheral Nervous System (PNS)

Answer 3

the sensory and motor neurons that connect
the central nervous system (CNS) to the
rest of the body.

Question 4

What are the three major parts of the brain

Answer 4

*forebrain
*midbrain
*hindbrain

Question 5

The structures in the forebrain include…

Answer 5

the cerebrum, thalamus, hypothalamus, pituitary gland, limbic system, and the olfactory bulb

Question 6

The midbrain consists of…

Answer 6

various cranial nerve nuclei, tectum,
tegmentum, colliculi, and crura cerebi.

Question 7

The hindbrain, also referred to as the brainstem, is made of…

Answer 7

the medulla, pons, cranial nerves, and back part of the brain called cerebellum.

Question 8

Cerebral Cortex

Answer 8

the outermost and top layer of the
brain; divided into the frontal, parietal, temporal and occiptal lobes; the cerebral cortex is responsible for thought processes like speech and decision making; each different lobe is responsible for different cognitive and processing functions

Question 9

Grey Matter

Answer 9

The grey matter creates a hornlike structure throughout the inside of the spinal cord while the white matter makes up the surrounding sections of the spinal cord. The grey matter does extend to the spinal cord to make signaling more effective.

The tissue called “gray matter” in the brain and spinal cord is also known as substantia grisea, and is made up of cell bodies.

Question 10

White Matter

Answer 10

“White matter”, or substantia alba, is composed of nerve fibers (mostly axons)

Question 11

The three primary roles of the spinal cord…

Answer 11

1. To send motor commands from the brain to the body
2. Send sensory information from the body to the brain
3. Coordinate reflexes.

Question 12

meninges

Answer 12

Consists of three layer:
*Dura mater
*Arachnoid
*Pia mater

Protects the brain and spinal cord

Question 13

Meningitis

Answer 13

*Meningitis is an infection of the protective membranes that surround the brain and spinal cord (meninges).
* Meningitis can be confirmed by cerebrospinal fluid analysis and culture or by necropsy.
* Epsilon-toxin (ETX) produced by Clostridium perfringens types C & D is an example of a
toxin that can cause meningitis.
*5% to 10% of patients die, typically within 24 to 48 hours after the onset of symptoms.
*Bacterial meningitis may result in brain damage, hearing loss or a learning disability in 10% to 20% of survivors.

Question 14

The cranial nerves are…

Answer 14

a set of 12 paired nerves in the back of your brain. Cranial nerves send electrical signals between your brain, face, neck and torso.
Cranial nerves transmit sensory information, including touch, vision, taste, smell, and hearing. They also help you make facial expressions, blink your eyes and move your tongue.

Question 15

Spinal nerves are…

Answer 15

bundles of nerve fibers connected to the spinal cord that carry information to and away from the spinal cord. In total, there are 31 pairs of spinal nerves grouped regionally by spinal region. Spinal nerves supply all the
areas of the body except most head and neck region (cranial nerves regions) with a few exceptions such as neck muscles are supplied by the spinal nerves.

Question 16

The main difference between nerve and neuron

Answer 16

The main difference between nerve and neuron is that a nerve is a bundle of neurons along with their connective tissue sheaths, blood vessels, and lymphatics whereas a neuron is a cell of the nervous system that conducts nerve impulses.

Nerve and neuron are two structural components that make up the nervous system of vertebrates.

Question 17

What is a neuron

Answer 17

Neurons (also called nerve cells) are the
fundamental units of the nervous system.

Question 18

Sensory neuron

Answer 18

These neurons take sensory information from the environment (e.g. getting poked by a needle) and sends the signal to the brain

Question 19

Motor neuron

Answer 19

These neurons communicate information from the brain to the tissues and organs throughout the body, allowing for movement

Question 20

Interneuron

Answer 20

These neurons make up the majority of neurons in the body. They are essentially the middle man, transmitting information between sensory and motor neurons. They play a key role in learning, memory and planning.

Question 21

In terms of function, we can classify neurons into three broad types

Answer 21

*Sensory
*Motor
*Interneurons.

Question 22

The Sympathetic Nervous System

Answer 22

• Mobilizes the body’s resources for emergencies and creates the fight-or-flight response.
  *Dilates pupils
  *Accelerates heart beat
  *Inhibits digestion
  *Relaxes bladder
  *Stimulates glucose release by the liver
  *Stimulates secretion of epinephrine and norepinephrines

Question 23

The Parasympathetic Nervous System

Answer 23

• Activates processes that conserve bodily
  resources… slowing heart rate, reducing blood pressure, etc.
  *Stimulates gall bladder
  *Contacts bladder
  *Contracts pupils
  *Stimulates digestion

Question 24

Signal transmission – action potential

Answer 24

Dendrites
* Stimulus triggers a change in the internal charge

Axon
* If positive, flow of positive ions travel the length of the axon

Axon terminal
* Stimulates release of neurotransmitters

Question 25

Glial cells

Answer 25

Glial cells are the key element for supporting the messages neurons send and receive all over the body. Much like the insulation around the wires in electrical systems, glial
cells form a membraneous sheath surrounding axons called myelin, thereby insulating the axon

Question 26

Myelination effect on signal transfer

Answer 26

Myelination greatly alters the electrical properties of the axon. The wrappings of membrane around the axon increase the effective membrane resistance which means that less of the conducted signal is lost through the membrane and the amplitude of a conducted signal decreases less with distance along the axon. Conduction velocity is greatly increased by myelination, and the current generated at one node of Ranvier is conducted at great speed to the next. In myelinated axons, far fewer ions traverse a unit length of fiber membrane, and much less ion pumping-and energy expenditure-is required to maintain the gradients.

Question 27

Synapses

Answer 27

Synapses or “gap” refer to the points of contact between neurons, where information is passed from one neuron to the next cell.

Synapses usually form between axon terminals and dendritic spines, but this is not universally true. There are also axon-to-axon, dendrite- to-dendrite, and axon-to-cell body synapses (another neuron or a different type of cell). It consist of a presynaptic neuron, synaptic cleft, and a postsynaptic cell.

When the presynaptic membrane is depolarized, voltage-gated Ca2+ channels open and allow Ca2+ to enter the cell. The calcium entry causes synaptic vesicles to fuse with the membrane and release neurotransmitter molecules into the synaptic cleft. The neurotransmitter diffuses across the synaptic cleft and binds to ligand-gated ion channels in the postsynaptic membrane, resulting in a localized depolarization or hyperpolarization of the postsynaptic
neuron.

The binding of a specific neurotransmitter causes particular ion channels, in this case (picture), ligand-gated channels, on the postsynaptic membrane to open.

Neurotransmitters can either have excitatory or inhibitory effects on the postsynaptic membrane. Na+ channels to open. Na+ enters the postsynaptic cell and causes the
postsynaptic membrane to depolarize.

Question 28

Excitatory neurotransmitters

Answer 28

Excitatory neurotransmitters “excite” the neuron and cause it to “fire off the message,” meaning, the message continues to be passed along to the next cell. Examples of excitatory neurotransmitters include glutamate, and norepinephrine.

Question 29

Inhibitory neurotransmitters

Answer 29

Inhibitory neurotransmitters block or prevent the chemical message from being passed along any farther. Gamma-aminobutyric acid (GABA), glycine, endorphins (“endogenous morphine”), acetylcholine (ACh; on most visceral muscles of the body and heart) and serotonin are examples of inhibitory neurotransmitters.

Question 30

Modulatory neurotransmitters

Answer 30

Modulatory neurotransmitters influence the effects of other chemical messengers. They “tweak” or adjust how cells communicate at the synapse. They also affect a larger number of neurons at the same time.

Question 31

Classical neuro transmitters

Answer 31

Amino acids:
*Glutamate
*y-aminobutyric acid (GABA)
*Glycine

Monoamines
*Dopamine (DA)
*Norepinephrine (NE)
*Serotonin (5-HT)

Acetylcholine

Question 32

Nonclassical neurotransmitters

Answer 32

Neuropeptides:
*Endorphins and enkephalins
*Coticotropin-releasing factor (CRF)
*Brain-derived neurotrophic factor (BDNF)

Lipids
*Anandamide

Gases
*Nitric oxie (NO)

Question 33

After neurotransmitters deliver their message, the molecules must be cleared from the synaptic cleft (the space between the nerve cell and the next target cell). They do this in one of three ways…

Answer 33

Neurotransmitters:

1. Fade away (a process called
   diffusion).
2. Are reabsorbed and reused by the
   nerve cell that released it (a process called reuptake).
3. Are broken down by enzymes within the synapse so it can’t be recognized or bind to the receptor cell (a process called degradation).

Question 34

Synthesis takes place in the…

Answer 34

• Synthesis takes place in the
  pre-synaptic neuron.
• Once neuropeptides are synthesized, they are stored in vesicles within the axon
  terminal until an action potential arrives and they are released.

Question 35

Neurotoxicity

Answer 35

An adverse change in the chemistry,
structure or function of the nervous system during development or at maturity, following exposure to a chemical or physical agent

Question 36

Neuronopathy

Answer 36

• Injury or death to neurons
• Irreversible loss

It is a form of polyneuropathy and occurs as a
result of neuron degeneration. It is a subgroup of disorders of the peripheral nervous system (PNS)

There are several types of neuronopathy,
including sensory neuronopathy, also known as ganglionopathy (immune system mistakenly attacks autonomic nervous system), motor neuronopathy, and autonomic neuronopathy.

Question 37

Methylmercury

Answer 37

• Necrosis → Apoptosis
• Methylmercury covalently binds to
  cysteine, as mentioned above, to form cysteine-methylmercury, a structural analogue of an essential amino acid methionine, which can effectively pass through not only the placenta but the blood-brain barrier via an amino acid transporter.

Question 38

Reactive Oxygen Species (ROS) causes…

Answer 38

: lipid peroxidation & Damage DNA strands & Modify proteins

Question 39

Reactive Oxygen Species (ROS)

Answer 39

Reactive oxygen species (ROS) such as superoxide anion, hydrogen peroxide, and hydroxyl radicals are believed to be initiators of peroxidative cell damage.

Question 40

Antioxidants

Answer 40

Antioxidants are molecules that can donate an electron to a free radical without making
themselves unstable. This causes the free
radical to stabilize and become less reactive.

Oxidative stress is considered as an imbalance between pro- and antioxidant species, which results in molecular and cellular damage.

Question 41

Mercury Cycle

Answer 41

Mercury persists in the environment for
long periods by cycling back and forth
between the air, water and soil, all the
while changing chemical forms.

In the form of methylmercury, it is a
potent neurotoxin that affects human
and wildlife development and health.

The ultimate sink of mercury is burial to the deep-ocean sediments, which occurs very slowly. Overall lifetime of mercury in the combined atmosphere-ocean-terrestrial
system against transfer to the sediments is 3000 years.

This organic form of mercury (i.e. methylmercury) is absorbed by the tissues of fish through their gills as they swim, and also through their digestive tracts as they feed.
Nearly all fish and shellfish might contain traces of methylmercury. However, larger fish that have lived longer have the highest levels of methylmercury because they’ve had more time to accumulate it.

Question 42

Carbon monoxide (CO)

Answer 42

*Reduces oxygen supply
* Induces the production of ROS

Question 43

Cyanide

Answer 43

Molecular Weight, 26.02g/mol

Cyanides:
* Sodium cyanide
* Potassium cyanide
* Hydrogen cyanide

Cyanide sometimes is described as having a “bitter almond” smell, but it does not always
give off an odor, and between 20 and 40 percent of the population does not carry the gene needed to detect the odor of cyanide.

Question 44

Amygdalin

Answer 44

is a plant substance found in raw nuts, bitter almonds, as well as apricot and cherry seeds.
Plants like lima beans, clover and sorghum also contain amygdalin.
When it is processed by the body, it changes to cyanide. Cyanide is thought to kill cancer
cells. However, there is not enough reliable scientific evidence to say it can treat cancer.

Question 45

Axonopathy

Answer 45

Axonopathy broadly defined as functional or structural defects in the axon or its terminal

Question 46

The cytoskeleton of nerve cells

Answer 46

• The cytoskeleton is a structure that helps cells maintain their shape and internal organization, and it also provides mechanical support that enables cells to carry out essential functions like division and movement.
• The cytoskeleton of neurons and other
  eukaryotic cells comprises three distinct,
  interacting structural complexes that have very different properties: microtubules (MTs),
  neurofilaments (NFs) and microfilaments (MFs).

*A growth cone is a large actin-supported extension of a developing or regenerating neurite seeking its synaptic target.