Chapter 11 - Nervous System

Question 1

What is the Nervous system?

Answer 1

The nervous system is the human organ system that coordinates all of the body’s voluntary and involuntary actions by transmitting signals to and from different parts of the body.

Question 2

Two divisions of nervous system?

Answer 2

The nervous system has two major divisions, called the central nervous system (CNS) and the peripheral nervous system (PNS). The CNSincludesthe brain and spinal cord, and the PNS consists mainly of nerves that connect the CNS with the rest of the body.

Question 3

Divisions of the PNS

Answer 3

The PNS also has two major divisions: the somatic nervous system and the autonomic nervous system. The somatic system controls activities that are under voluntary control. The autonomic system controls activities that are not under voluntary control. The autonomic nervous system is further divided into the sympathetic division, which controls the fight-or-flight response; the parasympathetic division, which controls most routine involuntary responses; and the enteric division, which provides local control for digestive processes.

Question 4

Nerve Impulses

Answer 4

Signals sent by the nervous system are electrical signals called nerve impulses. They are transmitted by special cells called neurons. Nerve impulses can travel to specific target cells very rapidly.

Question 5

Divisions of Autonomic Nervous System:

Answer 5

The autonomic nervous system has three divisions: the sympathetic division, which controls the fight-or-flight response during emergencies; the parasympathetic division, which controls the routine “housekeeping” functions of the body at other times; and the enteric division, which provides local control of the digestive system.

Question 6

Neurons

Answer 6

Neurons are one of two major types of nervous system cells. They are electrically excitable cells that transmit nerve impulses.

Question 7

Glial Cells

Answer 7

Glial cells are the other major type of nervous system cells. There are many types of glial cells, and they have many specific functions. In general, glial cells function to support, protect, and nourish neurons.

Question 8

Parts of a Neuron:

Answer 8

The main parts of a neuron include the cell body, dendrites, and axon. The cell body contains the nucleus. Dendrites receive nerve impulses from other cells, and the axon transmits nerve impulses to other cells at axon terminals. A synapse is a complex membrane junction at the end of an axon terminal that transmits signals to another cell.

Question 9

Axons

Answer 9

Axons are often wrapped in an electrically-insulating myelin sheath, which is produced by glial cells. Electricalsignalsoccur at gaps in the myelin sheath, called nodes of Ranvier, which speeds the conduction of nerve impulses down the axon.

Question 10

Neurogenesis

Answer 10

Neurogenesis, or the formation of new neurons by cell division, may occur in a mature human brain but only to a limited extent.

Question 11

Tissues in the Brain and Nerves

Answer 11

The nervous tissue in the brain and spinal cord consists of gray matter, which contains mainly the cell bodies of neurons; and white matter, which contains mainly myelinated axons of neurons. Nerves of the peripheral nervous system consist of long bundles of myelinated axons that extend throughout the body.

Question 12

Types of Neurons

Answer 12

There are hundreds of types of neurons in the human nervous system, but manycan be classified on the basis of the direction in which they carry nerve impulses. Sensory neurons carry nerve impulses away from the body and toward the central nervous system, motor neurons carry them away from the central nervous system and toward the body, and interneurons often carry them between sensory and motor neurons.

Question 13

Interneurons

Answer 13

Interneuronscarry nerve impulses back and forth often between sensory and motor neurons within the spinal cord or brain.

Question 14

The word glial comes from a Greek word meaning “____.”

Answer 14

glue

Question 15

Types of Glial Cells

Answer 15

Different types of glial cells (neuroglia) are found in the central nervous system and peripheral nervous system. Ependymal cells, oligodendrocytes, astrocytes, and microglia are found in the CNS. Satellite cells and Schwann cells are found in the PNS.

Question 16

Neurons, Glial cells, and intelligence

Answer 16

In the human brain, there are generally about equal numbers of neurons and glial cells. If you think intelligence depends on how many neurons you have, think again. Having a relatively large number of glial cells is actually associated with higher intelligence. When Einstein’s brain was analyzed, researchers discovered a significantly higher-than-normal ratio of glial cells to neurons in areas of the brain associated with mathematical processing and language. On an evolutionary scale as well, an increase in the ratio of glial cells to neurons is associated with greater intelligence in species.

Question 17

What is a nerve impulse?

Answer 17

A nerve impulse is an electrical phenomenon that occurs because of a difference in electrical charge across the plasma membrane of a neuron.

Question 18

What is the function of the Sodium Potassium Pump?
What is the gradient called?

Answer 18

The sodium-potassium pump maintains an electrical gradient across the plasma membrane of a neuron when it is not actively transmitting a nerve impulse. This gradient is called the resting potential of the neuron.

Question 19

What is the action potential?

Answer 19

An action potential is a sudden reversal of the electrical gradient across the plasma membrane of a resting neuron. It begins when the neuron receives a chemical signal from another cell or some other type of stimulus. The action potential travels rapidly down the neuron’s axon as an electric current.

Question 20

What is an action potential?

Answer 20

An action potential is a sudden reversal of the electrical gradient across the plasma membrane of a resting neuron. It begins when the neuron receives a chemical signal from another cell or some other type of stimulus. The action potential travels rapidly down the neuron’s axon as an electric current.

Question 21

Neurotransmitters:

Answer 21

There are many different types of neurotransmitters. Their effects on the postsynaptic cell generally depend on the type of receptor they bind to. The effects may be excitatory, inhibitory, or modulatory in more complex ways. Both physical and mental disorders may occur if there are problems with neurotransmitters or their receptors.

Question 22

Types of receptors:

Answer 22

Receptors, in turn, can be divided into two general groups: chemically gated ion channels and second messenger systems.

When a chemically gated ion channel is activated, it forms a passage that allows specific types of ions to flow across the cell membrane. Depending on the type of ion, the effect on the target cell may be excitatory or inhibitory.

When a second messenger system is activated, it starts a cascade of molecular interactions inside the target cell. This may ultimately produce a wide variety of complex effects, such as increasing or decreasing the sensitivity of the cell to stimuli or even altering gene transcription.

Question 23

What are the two most widely used neurotransmitters?

Answer 23

Glutamate and GABA (Gamma-aminobutyric acid)

Question 24

Neurotransmitters and neurological disorders:

Answer 24

Problems with neurotransmitters or their receptors can cause neurological disorders. For example, the disease myasthenia gravis is caused by antibodies from the immune system blocking receptors for the neurotransmitter acetylcholine in postsynaptic muscle cells. This inhibits the effects of acetylcholine on muscle contractions, producing symptoms such as muscle weakness and excessive fatigue during simple activities. Some mental illnesses including depression are caused, at least in part, by imbalances of certain neurotransmitters in the brain. One of the neurotransmitters involved in depression is thought to be serotonin, which normally helps regulate mood among many other functions. Some antidepressant drugs are thought to help alleviate depression in many patients by normalizing the activity of serotonin in the brain.

Question 25

What is the CNS?

Answer 25

The central nervous system is the part of the nervous system that includes the brain and spinal cord. It is physically protected by bones, meninges, and cerebrospinal fluid. It is chemically protected by the blood-brain barrier.

Question 26

What i the Brain?

Answer 26

The brain is the control center of the nervous system and of the entire organism. The brain uses a relatively large proportion of the body’s energy, primarily in the form of glucose.

Question 27

What are the 3 major portions of the brain?

Answer 27

The brain is divided into three major parts, each with different functions: brain stem, cerebellum, and cerebrum. The cerebrum is further divided into left and right hemispheres. Each hemisphere has four lobes: frontal, parietal, temporal, and occipital. Each lobe is associated with specific senses or other functions.

Question 28

What is the cerebral cortex?

Answer 28

The cerebrumhas athin outer layer called the cerebral cortex. Its many folds give it a large surface area. This is where most information processing takes place.

Question 29

What are the inner structures of the brain?

Answer 29

Inner structures of the brain include the hypothalamus, which controls the endocrine system via the pituitary gland; and the thalamus, which has several involuntary functions.

Question 30

What connects the brain to the PNS?

Answer 30

The spinal cord is a tubular bundle of nervous tissues that extends from the head down the middle of the back to the pelvis. It functions mainly to connect the brain with the peripheral nervous system. It also controls certain rapid responses called reflexes without any input from the brain.

Question 31

What happens when the spina cord is damaged?

Answer 31

A spinal cord injury may lead to paralysis (loss of sensation and movement) of the body below the level of the injury because nerve impulses can no longer travel up and down the spinal cord beyond that point.

Question 32

STROKE

Answer 32

Stroke,also known as cerebrovascular accident, occurs when poor blood flow to the brain results in the death of brain cells. There are two main types of strokes:

Ischemic strokes occur due to lack of blood flow because of a blood clot in an artery going to the brain.

Hemorrhagic strokes occur due to bleeding from a broken blood vessel in the brain.

Either type of stroke may result in paralysis, loss of the ability to speak or comprehend speech, loss of bladder control, personality changes, and many other potential effects, depending on the part of the brain that is injured. The effects of a stroke may be mild and transient or more severe and permanent. A stroke may even be fatal. It generally depends on the type of stroke and how extensive it is.

Question 33

Two other diseases of the PNS are:

Answer 33

Guillain-Barre syndrome is a rare disease in which the immune system attacks nerves of the PNS, leading to muscle weakness and even paralysis. The exact cause of Guillain-Barre syndrome is unknown, but it often occurs after a viral or bacterial infection. There is no known cure for the syndrome, but most people eventually make a full recovery. Recovery can be slow, however, lasting anywhere from several weeks to several years.

Charcot-Marie-Tooth disease is a hereditary disorder of the nerves and one of the most common inherited neurological disorders. It affects predominantly the nerves in the feet and legs but often also in the hands and arms. The disease is characterized by loss of muscle tissue and sense of touch. It is presently incurable.

Question 34

The PNS is subject to ___ damagae than the CNS because _____ ____ ___ ___

Answer 34

more, it is not protected

Question 35

PNS

Answer 35

The peripheral nervous system (PNS) consists of all the nervous tissue that lies outside of the central nervous system (CNS). Its main function is to connect the CNS to the rest of the organism.

Question 36

TISSUES of PNS

Answer 36

The tissues that make up the PNS are nerves and ganglia. Ganglia act as relay points for messages that are transmitted through nerves. Nerves are classified as sensory, motor, ora mix of the two.

Question 37

2 main Divisions of PNS

Answer 37

The PNS is divided into the somatic and autonomic nervous systems. The somatic system controls voluntary activities, whereas the autonomic system controls involuntary activities.

Question 38

Divisions of Autonomic Nervous System

Answer 38

The autonomic nervous system is further divided into sympathetic, parasympathetic, and enteric divisions. The sympathetic division controls fight-or-flight responses during emergencies, the parasympathetic system controls routine body functions the rest of the time, and the enteric division provides local control over the digestive system.

Question 39

What are the two major types of senses?

Answer 39

The human body has two major types of senses, special senses and general senses. Special senses have specialized sense organs and include vision (eyes), hearing (ears), balance (ears), taste (tongue), and smell (nasal passages). General senses are all associated with touch and lack special sense organs. Touch receptors are found throughout the body but particularly in the skin.

Question 40

What do senses depend on to detect sensory stimuli?

Answer 40

All senses depend on sensory receptor cells to detect sensory stimuli and transform them into nerve impulses. Types of sensory receptors include mechanoreceptors (mechanical forces), thermoreceptors (temperature), nociceptors (pain), photoreceptors (light), and chemoreceptors (chemicals).

Question 41

What does touch include?

Answer 41

Touch includes the ability to sense pressure, vibration, temperature, pain, and other tactile stimuli. The skin includes several different types of touch receptor cells.

Question 42

What is vision?

Answer 42

Vision is the ability to sense light and see. The eye is the special sensory organ that collects and focuses light, forms images, and changes them to nerve impulses. Optic nerves send information from the eyes to the brain, which processes the visual information and “tells” us what we are seeing.

Question 43

What are some common vision problems?

Answer 43

Common vision problems include myopia (nearsightedness), hyperopia (farsightedness), and presbyopia (age-related decline in close vision). Vision problems can be corrected with lenses (eyeglasses or contacts) or, in many cases, with laser surgery.

Question 44

What does the ear do?

Answer 44

The ear is also the organ that is responsible for the sense of balance, which is the ability to sense and maintain an appropriate body position. The ears send impulses on head position to the brain, which sends messages to skeletal muscle via the peripheral nervous system. The muscles respond by contracting to maintain balance.

Question 45

What abilities are involved in sensing chemicals?

Answer 45

Taste and smell are both abilities to sense chemicals. Taste receptors in taste buds on the tongue sense chemicals in food, and olfactory receptors in the nasal passages sense chemicals in the air. The sense of smell contributes significantly to the sense of taste.

Question 46

Types of receptors:

Answer 46

There are several different types of sensory receptors that respond to different kinds of stimuli:

Mechanoreceptorsrespond to mechanical forces such as pressure, roughness, vibration, and stretching. Most mechanoreceptors are found in the skin and are needed for the sense of touch. Mechanoreceptors are also found in the inner ear where they are needed for the senses of hearing and balance.

Thermoreceptorsrespond to variations in temperature. They are found mostly in the skin and detect temperatures that are above or below body temperature.

Nociceptorsrespond to potentially damaging stimuli, which are generally perceived as pain. They are found in internal organs as well as on the surface of the body. Different nociceptors are activated depending on the particular stimulus. For example, some detect damaging heat or cold, others detect excessive pressure, and still others detect painful chemicals such as very hot spices in food.

Photoreceptorsdetect and respond to light. Most photoreceptors are found in the eyes and are needed for the sense of vision.

Chemoreceptorsrespond to certain chemicals. They are found mainly in taste buds on the tongue, where they are needed for the sense of taste; and in nasal passages, where they are needed for the sense of smell.

Question 47

What are the different types of Tactile receptors in the skin?

Answer 47

Tactile receptors in the skin include free nerve endings, Merkel cells, Meissner’s corpuscles, Pacinian corpuscles, root hair plexuses, and Ruffini corpuscles. Each type of sensory receptor responds to a different kind of tactile stimulus. For example, free nerve endings generally respond to pain and temperature variations, whereas Merkel cells are associated with the sense of light touch and the discrimination of shapes and textures.

Question 48

How does the eye work?

Answer 48

How the eye performs these functions is summarized in the following steps.

Light passes first through the cornea, which is a clear outer layer that protects the eye and helps to focus the light by refracting, or bending, it.

Light next enters the interior of the eye through an opening called the pupil. The size of this opening is controlled by the colored part of the eye, called the iris, which adjusts the size based on the brightness of the light. The iris causes the pupil to narrow in bright light and widen in dim light.

The light then passes through the lens, which refracts the light even more and focuses it on the retina at the back of the eye as an inverted image.

Theretinacontains photoreceptor cells of two types, called rods and cones. Rods, which are found mainly in all areas of the retina other than the very center, are particularly sensitive to low levels of light. Cones, which are found mainly in the center of the retina, are sensitive to light of different colors and allow color vision. The rods and cones convert the light that strikes them to nerve impulses.

The nerve impulses from the rods and cones travel to the optic nerve via the optic disc, which is a circular area at the back of the eye where the optic nerve connects to the retina.

Question 49

What are Psychoactive Drugs?

Answer 49

Psychoactive drugs are substances that change the function of the brain and result in alterations of mood, thinking, perception, and/or behavior. They include prescription medications such as opioid painkillers, legal substances such as nicotine and alcohol, and illegal drugs such as LSD and heroin.

Question 50

Classes of Psychoactive drugs?

Answer 50

Psychoactive drugs are divided into different classes according to their pharmacological effects. They include stimulants, depressants, anxiolytics, euphoriants, hallucinogens, and empathogens. Many psychoactive drugs have multiple effects so they may be placed in more than one class.

Question 51

How do Psychoactive drugs produce their effects?

Answer 51

Psychoactive drugs generally produce their effects by affecting brain chemistry. Generally, they act either as agonists, which enhance the activity of particular neurotransmitters; or as antagonists, which decrease the activity of particular neurotransmitters.

Question 52

Misuses of psychoactive drugs?

Answer 52

Misuse of psychoactive drugs may lead to addiction, which is compulsive use of a drug despite negative consequences such use may entail. Sustained use of an addictive drug may produce physical or psychological dependence on the drug. Rehabilitation typically involves psychotherapy and sometimes the temporary use of other psychoactive drugs.

Question 53

Psychoactive drugs and rituals

Answer 53

Certain psychoactive drugs, particularly hallucinogens, have been used for ritual purposes since prehistoric times. For example, Native Americans have used the mescaline-containing peyote cactus (picturedbelow) for religious ceremonies for as long as 5,700 years. In prehistoric Europe, the mushroomAmanita muscaria, which contains a hallucinogenic drug called muscimol, was used for similar purposes. Various other psychoactive drugs — including jimsonweed, psilocybin mushrooms, and cannabis—have also been used by various peoples for ritual purposes for millennia.

Question 54

6 main classes of Psychoactive drugs:

Answer 54

Stimulants are drugs that stimulate the brain and increase alertness and wakefulness. Examples of stimulants include caffeine, nicotine, cocaine, and amphetamines such as Adderall.

Depressants are drugs that calm the brain, reduce anxious feelings, and induce sleepiness. Examples of depressants include ethanol (in alcoholic beverages) and opioids such as codeine and heroin.

Anxiolytics are drugs that have a tranquilizing effect and inhibit anxiety. Examples of anxiolytic drugs include benzodiazepines such as diazepam (Valium), barbiturates such as phenobarbital, opioids, and antidepressant drugs such as sertraline (Zoloft).

Euphoriants are drugs that bring about a state of euphoria, or intense feelings of well-being and happiness. Examples of euphoriants include the so-called club drug MDMA (ecstasy), amphetamines, ethanol, and opioids such as morphine.

Hallucinogens are drugs that can cause hallucinations and other perceptual anomalies. They also cause subjective changes in thoughts, emotions, and consciousness. Examples of hallucinogens include LSD, mescaline, nitrous oxide, and psilocybin.

Empathogens are drugs that produce feelings of empathy, or sympathy with other people. Examples of empathogens include amphetamines and MDMA.