Chapter 11 A&P

Neuropathy

Any disease of nervous tissue, but particularly degenerative disease of nerves.

Motor

Which of the following types of types of glial cells produces the myelin sheaths that insulate axons, or nerve fibers, in the central nervous system (CNS)?

a nerve is a long axon, an extension of the cell. in connective tissue, fibers are extracellular proteins that provide support. in muscle tissue, a muscle fibers is a muscle cell.

Which part of the neurons it is fiber? how do nerve fibers differ from the fibers of connective tissue and the fibers in muscle?

oligodendrocytesand schwann cells form myelin sheaths in the CNS and PNS respectively.

Which two types of neuroglia form insulating coverings called myelin sheaths?

conduction of action potential is faster in myelinated axons because myelin allows the axon membrane between myelin sheaths gaps to change its voltage rapidly, and allows current to flow only at the widely spaced gaps.

Why does a myelinated axon conduct action potentials faster than a nonmyalinated axon?

Axon

Which of the following is the conducting region of the neuron?

Shingles

(Herpes zoster) Inflammation of virally infected sensory neurons serving the skin. caused by varicella-zoster virus is transported from the skin lesions tot the sensory neuron cell bodies in the sensory ganglia. Topically the immune system is weakened, often by stress. then viral particles multiply, causing nerve pain (neuralgia), and travel back to the skin, producing characteristic scaly blisters. this rash is usually confined to one side of the body trunk. attacks last several weeks, alternating between periods of healing and relapse. seen mostly in those over 50 years old. Vaccination can prevent occurrence and minimize pain.

Neuroblastoma

A malignant tumor in children; arises from that reain a neuroblast- like structure. these tumors sometimes arise in the brain, but most occur in the peripheral nervous system.

Oligodendrocyte

A type of CNS supporting cell that composes myelin sheaths.

Astrocyte

A type of CNS supporting cell; assists in exchanges between blood capillaries and neurons.

Microglial cell

A type of CNS supporting cell; can transform into phagocytes in areas of neural damage or inflammation.

Ependymal cell

A type of CNS supporting cell; lines the central cavities of the brain and spinal cord.

Schwann Cell

A type of supporting cell in the PNS; forms myelin sheaths and is vital to peripheral nerve fiber regeneration

Rabies

A viral infection of the nervous system transmitted by the bite of an infected mammal (such as a dog, bat, or skunk) After entry, the virus travels via axonal transport in peripheral nerve axons to the CNS; where it causes brain inflammation, delirium, and death. A vaccine and antibody based treatment is effective if given before symptoms appear. Rabies in humans is very rare in the United States.

Multiple sclerosis

Demyelinating disorder of the CNS; causes hardened patches in the brain and spinal cord.

Norepinephrine

Excitatory or inhibitory depending on receptor type bound. CNS:brain stem, particularly in the locus coeruleus of the mainbran; limbic system; some areas of he cerebral cortex. a "feel good" neurotransmitter. release enhanced by amphetamines; removal from synapse blocked by tricyclic antidepressants and cocaine. Brain levels reduced by reserpine (an antihypertensive drug) leading to depression.

ATP

Excitatory or inhibitory depending on receptor type bound. Direct and indirect actions via second messenger. CNS: basal nuclei induces Ca2+ wave propagation in astrocytes. PNS: Dorsal root ganglion neurons. ATP released by sensory neurons (as well as that released by injured cells) provokes pain sensation.

Dopamine

Excitatory or inhibitory depending on the receptor type bound. indirect action via second messengers. CNS: substanitia nigra of midbrain; hypothalamus; the principal neurotransmitter of indirect motor pathways. A " feel good" neurotransmitter. release enhanced by L-dopa and amphetamines; reuptake blocked by cocaine. deficient in Parkinson's disease; dopamine neurotransmission increases in schizophrenia.

Nitric Oxide (NO)

Excitatory or inhibitory. Indirect action via second messenger. CNS:brain, spinal cord. PNS: adrenal gland, nerves to penis. its release potentiates stroke damage. some types of male impotence treated by enhancing NO action (e.g. with sildenafil (Viagra))

Substance P (Tachykinins, Neurokinin A (NKA))

Excitatory. indirect action via second messenger. CNS: basal nuclei, midbrain, hypothalamus, cerebral cortex. PNS: certain sensory neurons of dorsal root ganglia (pain afferents), entering neurons. Mediates pain transmission in the PNS. in the CNS tachykinins are involved in respiratory and cardiovascular control and in mood.

there are more leakage channels in the K+ than for any other cation.

For which cation are there the biggest number of leakage channels in the plasma membrane?

Endophins

General inhibitory. Indirect action via second messengers. CNS: widely distributed in brain (hypothalamus, limbic system, pituitary) and Spinal cord. Natural opiates: inhibition pain by inhibiting substance P. effects mimicked by morphine, heroin, and methadone.

Glutamate

Generally excitatory. direct action. CNS: spinal widespread in brain where it represents the major excitatory neurotransmitter. important in learning and memory. The stroke "neurotransmitter" excessive release produces excitotoxicity- neurons literally stimulated to death; most commonly caused by ischemia (oxygen deprivation, usually due to a blocked blood vessels.)

GABA

Generally inhibitory. direct and indirect actions via second messengers. CNS: cerebral cortex, hypothalamus. Purkinje cells of cerebellum, spinal cord, granule cells of olfactory bulb, retina. Principal inhibitory neurotransmitter in the brain; important in presypnatic inhibition at axoaxonal synapses. inhibitory effects augmented by alcohol, antianxiety drugs of the benzodiazepine class, and barbiturates. substances that block its synthesis, release, or action induce convulsions.

Adenosine

Generally inhibitory. indirect action via second messengers. throughout CNS and PNS. Caffeine stimulates by blocking brain adenosine receptors. may be involved in sleep-wake cycle and terminating seizures. dilates arterioles, increasing blood flow to heat and other tissues as needed.

if a second stimulus occurs before the end of the absolute refraction period, no AP can occur because sodium channels are still inactivated.

If an axon receives two stimuli close together in time, only one AP occurs, why?

Endocannabinoids

Inhibitory. indirect action via second messengers. secreted throughout CNS. Involved in memory (as a retrograde messenger) appetite control, nausea and vomiting, neuronal development, receptors activated by THC, the principal active ingredient of cannabis.

Seratonin (5-HT)

Mainly inhibitory. indirect action via second messengers; direct action at 5-HT, receptors. CNS: brain stem, especially mainbrain; hypothalamus; limbic system; cerebellum; pineal gland; spinal cord. plays a role in sleep, appetite, nausea, migrane headaches; and regulating mood. Drugs that block it uptake relieve anxiety and depression. activity blocked by LSD and enhanced by ecstasy.

Neurotoxin

Substance that is poisonous or destructive to nervous tissue, e.g, botullinum and tetanus toxins.

Satellite cells

Surround neuron cell bodies located in the peripheral nervous system and are thought to have many of the same functions in the PNS as astrocytes do in the CNS, their name comes from a fancied resemblance to the moons around a planet.

Microglia

Which of the following types of glial cells monitors the health of neurons, and can transform into a special type of macrophage to protect endangered neurons?

Astrocytes control the extracellular environment around neuron cell bodies in the CNS, whereas satellite cells perform this function in the PNS.

What type of neuroglia contains the extracellular fluid environment around neuron cell bodies in the CNS? in the PNS?

the direction in which the nerve impulse travels relative to the central nervous system

Which criterion is used to functionally classify neurons?

the somatic nervous system

Which of the following allows us to consciously control our skeletal muscles?

Nodes of Ranvier

Which of the following are gaps found along a myelin sheaths?

spatial summations is used to increase the amplitude of a graded potential; temporal summations is used to increase the amplitude of an action potential.

Which of the following is NOT a difference between graded potentials and action potentials?

Pre-discharge circuits

Which of the following is NOT a type of circuit?

chlorides

Which of the following is NOT one of the chemical classes onto which neurotransmitters fall?

They are specialized for release and reception of chemical neurotransmitters.

Which of the following is NOT true of an electrical synapse?

Most association neurons are confined within the peripheral nervous system (PNS).

Which of the following is NOT true of association neurons?

Degree of myelination of the axon

Which of the following is a factor that determines the rate of impulse propagation, or conduction velocity, along an axon?

A neuron can have only one axon, but the axon may have occasional branches along its length.

Which of the following is true of axons?

Schwann cells

Which of the following peripheral nervous system (PNS) neuroglia form the myelin sheaths around larger nerve fibers in the PNS?

Cyclic AMP (cAMP) is called a second messenger because it relays the messenger (the original chemical messenger) outside of the cell and efferent molecules that will ultimately bring about the desired response within the cell.

Why is cyclic AMP called a second messenger?

the size of a graded potential is determined by strength of a stimulus

what determines the size of a graded potentials?

Neurofibrils

which of the following are bundles of neurofilaments that are important in maintaining the shape and integrity of neurons?

multipolar

which of the following is NOT a functional classification of neurons?

Regulation of neurogenesis

which of the following is NOT one of the basic functions of the nervous system?

burning your finger will first activate unipolar (pseudounipolar) neurons that are sensory (affrent) neurons. the impulse to move your finger away from the source of heat will be carried by multipolar neurons that are motor (efferent) neurons.

which structural and functional type of neuron is activated first when you burn your finger? which type is activated last to move your finger away from the source of heat?