Neuro - Ch 12 - Nervous Tissue

Front 1

How many pairs of cranial vs. spinal nerves do we have?

Back 1

12 pairs of cranial nerves. 31 pairs of spinal nerves.

Front 2

Bundle of axons in PNS vs. CNS

Back 2

Nerve (PNS). Tract (CNS)

Front 3

Cluster of cell bodies of neurons located in PNS vs. CNS

Back 3

Ganglia (PNS). Nucleus (CNS)

Front 4

Extensive network of neurons that regulate digestive system.

Back 4

Enteric plexuses

Front 5

Describe the 3 main functions of the nervous system.

Back 5

Sensory (PNS-->CNS), Integrative (CNS), Motor (CNS-->PNS)

Front 6

Conscious awareness of sensory stimuli is an integrative function called ___.

Back 6

Perception

Front 7

What are the 2 main divisions of the nervous system and what structures are associated?

Back 7

CNS (brain + spinal cord), PNS (cranial + spinal nerves)

Front 8

Functional unit of nervous system with capacity to produce action potentials.

Back 8

Neuron

Front 9

Change in environment strong enough to initiate action potential.

Back 9

Stimulus

Front 10

List the 3 main parts of a neuron.

Back 10

Cell body, dendrites, axon

Front 11

Clusters of rough ER in neuron.

Back 11

Nissl bodies

Front 12

Bundles of intermediate filaments in neuron cytoskeleton that give cell shape and support.

Back 12

Neurofibrils

Front 13

Part of cytoskeleton that moves materials between cell body and axon.

Back 13

Microtubules

Front 14

Pigment clumps of lysosomes in neuron.

Back 14

Lipofuscin

Front 15

General term for any neuronal process that emerges from cell body of neuron.

Back 15

Nerve fiber

Front 16

Receiving/input part of neuron that is highly branched.

Back 16

Dendrites

Front 17

A(n) ___ is a long projection that often joins the cell body at a cone-shaped elevation called the ___. Part of axon closest to it is the ___.

Back 17

Axon. Axon hillock. Initial segment.

Front 18

Where do nerve impulses arise in a neuron and between what structures is it found?

Back 18

Trigger zone, found between axon hillock and initial segment.

Front 19

Cytoplasm of an axon

Back 19

Axoplasm

Front 20

Plasma membrane of an axon

Back 20

Axolemma

Front 21

Side branches at a right angle to the neuron.

Back 21

Axon collateral

Front 22

Fine processes at the end of axon and its collaterals.

Back 22

Axon terminals

Front 23

Site of communication between 2 neurons or a neuron and effector cell.

Back 23

Synapse

Front 24

Bulb-shaped structures at the tip of axon terminals. Others have string of swollen bumps called ___.

Back 24

Synaptic end bulb. Varicosities.

Front 25

Membrane-enclosed sacs in synaptic end bulbs/varicosities containing neurotransmitters.

Back 25

Synaptic vesicles

Front 26

Describe the 2 types of axonal transport. Which way does transport go?

Back 26

Slow (transport away from cell body), Fast (transport in both directions)

Front 27

What are the 3 structural classes of neurons? What is it based on? In which division of the nervous system are they found?

Back 27

Based on the number of fibers extruding from the cell body. Multipolar (CNS), bipolar (PNS), unipolar (PNS + special sensory organs)

Front 28

What are the 3 functional classes of neurons?

Back 28

Sensory/afferent, Motor/efferent, Interneuron/association (CNS)

Front 29

Make up 50% volume of nervous tissue but smaller and more numerous. Are non-excitable and mitotic.

Back 29

Neuroglia

Front 30

Neuroglia of the CNS that provide strength, support (microfilaments), protect the CNS by forming blood-brain barrier, maintain ECF, and play role in learning/memory (guides formation of neural synapse).

Back 30

Astrocyte

Front 31

Neuroglia of the CNS that form myelin sheath (a lipid/protein covering around axons).

Back 31

Oligodendrocyte

Front 32

Neuroglia of the CNS functioning as phagocyte that engulfs bacteria, dead/worn-out cells.

Back 32

Microglia

Front 33

Neuroglia of the CNS that produces cerebrospinal fluid (CSF).

Back 33

Ependymal

Front 34

Neuroglia of the PNS that form myelin sheath and help w/ axon regeneration.

Back 34

Schwann cell

Front 35

Neuroglia of the PNS surrounding neuronal bodies which act like astrocytes in CNS.

Back 35

Satellite cell

Front 36

Outer layer of schwann cell that encloses myelin sheath found only in PNS. Stimulates regrowth of axon.

Back 36

Neurolemma

Front 37

Gaps in myelin sheath.

Back 37

Nodes of ranvier

Front 38

Loss or destruction of myelin sheaths around axons resulting from multiple sclerosis, tay-sachs disease, or radiation/chemotherapy.

Back 38

Demyelination

Front 39

How do schwann cells and oligodendrocytes differ in number of axons they myelinate?

Back 39

Schwann cell myelinates 1 axon; oligodendrocyte myelinates multiple axons.

Front 40

What is the advantage of myelination?

Back 40

Increases the speed of nerve impulses.

Front 41

What structures are contained in white matter vs. gray matter?

Back 41

White - myelinated axons. Gray - neuron cell bodies, dendrites, unmyelinated axons, axon terminals, neuroglia.

Front 42

Division of PNS that is voluntary and innervates skeletal muscles.

Back 42

Somatic

Front 43

Division of PNS that is involuntary and innervates cardiac, smooth mm, glands.

Back 43

Autonomic

Front 44

Division of PNS that is involuntary and innervates smooth mm and visceral organs of the GI tract. Neurons function independently of ANS & CNS.

Back 44

Enteric

Front 45

Describe the 2 divisions of the autonomic nervous system (ANS).

Back 45

Sympathetic (fight or flight - increase HR). Parasympathetic (rest & digest - decrease HR).

Front 46

What other system does the nervous system work closely with?

Back 46

Endocrine

Front 47

Electrical potential difference (voltage) across cell membrane in excitable cells. What is the value (mV)?

Back 47

Resting membrane potential. -70 mV.

Front 48

Ion channel that randomly open and close. Found in nearly all cells, including dendrites, cell bodies, axons of all neurons.

Back 48

Leakage channel

Front 49

Ion channel that opens in response to binding of a ligand such as hormones, ions, gases, neurotransmitters. Found in dendrites and cell bodies.

Back 49

Ligand-gated channel

Front 50

Ion channel that opens in response to physical force such as touch, pressure, tissue stretching. Found in dendrites and cell bodies.

Back 50

Mechanically gated channel

Front 51

Ion channel that opens in response to a change in membrane potential (voltage). Found in axons of all neurons.

Back 51

Voltage-gated channel

Front 53

Small deviation from membrane potential that makes membrane either more polarized or less polarized.

Back 53

Graded potential

Front 54

Where do graded potentials occur in neurons? What ion channels are involved?

Back 54

Cell body and dendrites. Mechanical and ligand-gated channels.

Front 55

Mode of travel by which graded potentials die out as they spread along membrane due to leakage channels. Moves away from threshold.

Back 55

Decremation

Front 56

Process by which graded potentials add together. Moves towards threshold.

Back 56

Summation

Front 57

Sequence of rapidly occuring events that decrease & reverse membrane potential, then restore it to resting state.

Back 57

Action potential

Front 58

Where do action potentials occur? What ion channel is involved?

Back 58

Axon. Voltage-gated channel.

Front 59

The principle that states an action potential occurs completely or not at all is called ___.

Back 59

All-or-none principle

Front 60

An action potential occurs in axon membrane when depolarization reaches certain level called ___. What is the value (mV)?

Back 60

Threshold. -55 mV.

Front 61

At the peak of the action potential, what is the value inside the membrane (mV)?

Back 61

+30 mV

Front 63

Time during which a neuron cannot produce an action potential even with a very strong stimulus. Coincides w/ Na+ channel activation/inactivation.

Back 63

Absolute refractory period

Front 64

Period of time when a 2nd action potential can be initiated with a very strong stimulus. Coincides w/ K+ channels staying open after Na+ have returned to resting state.

Back 64

Relative refractory period

Front 65

Is the refractory period present in graded potentials or action potentials?

Back 65

Only action potentials which allows summation to occur in graded potentials.

Front 66

A strong stimulus (does/does not) increase strength of action potential but it (does/does not) increase frequency of action potential.

Back 66

A strong stimulus does not increase strength of action potential but it does increase frequency of action potential.

Front 67

Spread of action potential is known as ___.

Back 67

Propogation

Front 68

Type of conduction that occurs in unmyelinated axons & muscle fibers.

Back 68

Continuous conduction

Front 69

Type of faster conduction that occurs in myelinated axons where action potential leaps from node to node (of ranvier).

Back 69

Saltatory conduction

Front 70

What 3 factors would increase the speed of propogation of an action potential?

Back 70

Increase in myelination, axon diameter (more surface area), temperature.

Front 71

List the 3 classes of nerve fibers from largest to smallest and whether they are myelinated.

Back 71

A fiber (fastest, myelinated - touch, pain, motor neurons), B fiber (myelinated - viscera, autonomic motor neurons), C fiber (slowest, unmyelinated - heart, smooth mm, glands)

Front 72

How do we detect stimuli of different intensities if all nerve impulses are the same size?

Back 72

Frequency of action potentials

Front 73

At a synapse b/w neurons, neuron sending signal is called ___.

Back 73

Presynaptic neuron

Front 74

At a synapse b/w neurons, neuron receiving message is called ___.

Back 74

Postsynaptic neuron

Front 75

Type of synapse using ions and gap junctions. Faster, 2-way communication & synchronization of neurons - coordinated contraction ie. Heart, GI tract.

Back 75

Electrical synapse

Front 76

Type of synapse - 1 way info from presynaptic to postsynaptic neuron. Can be axodendritic, axosomatic, axoaxonic.

Back 76

Chemical synapse

Front 77

Space filled with interstitial fluid separating presynaptic/postsynaptic cell membranes.

Back 77

Synaptic cleft

Front 78

Is a postsynaptic potential classified as graded or action potential?

Back 78

Graded potential

Front 79

A depolarizing postsynaptic potential is called (excitatory/inhibitory) postsynaptic potential. Results from opening of ligand-gated Na+ channels.

Back 79

Excitatory postsynaptic potential (EPSP) b/c it brings it closer to threshold.

Front 80

A hyperpolarizing postsynaptic potential is called (excitatory/inhibitory) postsynaptic potential. Results from opening of ligand-gated K+ or Cl- channels.

Back 80

Inhibitory postsynaptic potential (IPSP) b/c it brings it farther to threshold.

Front 81

Type of neurotransmitter receptor that contains neurotransmitter binding site & ion channel.

Back 81

Ionotropic receptor

Front 82

Type of neurotransmitter receptor that contains neurotransmitter binding site only (ion channel is separate).

Back 82

Metabotropic receptor

Front 83

What are the 3 ways neurotransmitters are removed from synaptic cleft?

Back 83

1) Diffusion 2) Enzymatic degradation ie. Ache 3) Cell uptake & reuptake

Front 84

Type of summation resulting from buildup of neurotransmitters released simultaneously by several end bulbs.

Back 84

Spatial summation

Front 85

Type of summation resulting from buildup of neurotransmitters released by a single end bulb 2 or more times in rapid succession.

Back 85

Temporal summation

Front 86

Chemical substance that neurons use to communicate with other neurons, muscle fibers, glands.

Back 86

Neurotransmitters

Front 87

Best studied neurotransmitter released mostly by PNS and some CNS.

Back 87

Acetylcholine

Front 88

Name 2 amino acid neurotransmitters in CNS that produce powerful excitatory effects. Which is released by nearly all excitatory neurons in the brain?

Back 88

Glutamate, aspartate

Front 89

2 important inhibitory transmitters. Which one is only found in CNS and is most common inhibitory NT?

Back 89

Gamma aminobutyric acid is found in CNS. Glycine.

Front 90

Caused by a high level of glutamate in interstitial fluid of CNS.

Back 90

Excitotoxicity

Front 91

Neurotransmitter that plays roles in arousal from sleep, dreaming, regulating mood. This NT along with ___ (used in brain) also serve as hormones.

Back 91

Norepinephrine, epinephrine

Front 92

Brain neurotransmitter active during emotional responses, addictive behaviours, pleasurable experiences. Regulate skeletal muscle tone and contraction. Involved in Parkinson disease, schizophrenia.

Back 92

Dopamine

Front 93

Brain neurotransmitter involved in sensory perception, temperature regulation, mood control, appetite, induction of sleep.

Back 93

Serotonin

Front 94

What are the different ways a neurotransmitter effect can be modified with regards to synthesis, release, removal, receptor site?

Back 94

Synthesis - stimulated/inhibited. Release - blocked/enhanced. Removal - stimulated/blocked. Receptor site - blocked/activated.

Front 95

Anything that enhances a transmitter's effects.

Back 95

Agonist

Front 96

Anything that blocks the action of a neurotransmitter.

Back 96

Antagonist

Front 97

Functional groups of neurons that process specific info.

Back 97

Neural circuit

Front 98

Name the 5 types of neural circuits.

Back 98

Simple, diverging (sensory), converging (neuromuscular junction), reverberating (breathing, waking up), parallel (precise activities)

Front 99

Throughout life, nervous system exhibits ___, the capability to change based on experience. Include sprouting of new dendrites, synthesis of new proteins, changes in synaptic contacts with other neurons.

Back 99

Plasticity

Front 100

Is repair of neurons possible in the CNS/PNS and to what extent?

Back 100

CNS - no repairs possible. PNS - can repair damaged dendrites & axons.

Front 101

What are the 4 conditions that need to be met for neuron repair to occur?

Back 101

Cell body alive, schwann cell alive, no scar tissue, distance is reasonable.

Front 102

What are the 4 stages in chronological order of PNS repair?

Back 102

Chromatolysis, wallerian degeneration, retrograde, regeneration

Front 103

Stage in PNS repair 1-2 days after injury where Nissl bodies dissolve and cell body swells.

Back 103

Chromatolysis

Front 104

Stage in PNS repair 3-5 days after injury involving degeneration of distal portion of axon and myelin sheath.

Back 104

Wallerian degeneration

Front 105

Stage in PNS repair (months after injury) where macrophages phagocytize debris

Back 105

Retrograde

Front 106

Stage in PNS repair (months after injury) where schwann cells guide repair in the right direction by forming regeneration tube across injured area.

Back 106

Regeneration

Front 107

Disorder that causes destruction of myelin sheaths in CNS.

Back 107

Multiple sclerosis

Front 108

Disorder characterized by short, recurrent attacks of motor, sensory or psychological malfunction. May be caused by abnormal reverberating circuits.

Back 108

Epilepsy

Front 109

What 4 factors prevent neurogenesis in CNS?

Back 109

Inhibition of neuroglial cells, absence of growth stimulating factors, lack of neurolemmas, rapid formation of scar tissue.

Front 110

Stage in action potential - recovery of resting membrane potential

Back 110

Repolarization

Front 111

Stage in action potential - polarization that is more negative than resting level.

Back 111

After-hyperpolarizing phase

Front 112

What are the 3 major factors that cause the resting membrane potential?

Back 112

1) Concentration of ions different in ECF and cytosol. K+ tends to leak more quickly than Na+ entering so inside of membrane becomes increasingly negative and outside more positive. 2) Inability of most anions to leave cell (are usually attached to nondiffusable molecules). 3) Electrogenic nature of Na+/K+ ATPases (removes Na+ continuously to maintain resting membrane potential).

Front 113

Describe the 4 phases of the action potential.

Back 113

1) Depolarization - graded potential causes membrane to depolarize to threshold. Voltage-gated Na+ channels open, enter & inside membrane becomes more positive (+30 mV). 2) Repolarization - K+ channels open & leave cell to make inside membrane more negative. 3) Hyperpolarization - K+ channels stay open. 4) Refractory period - time when cell cannot generate another action potential in response to normal threshold stimulus.

Front 114

Describe the steps in signal from presynaptic end bulb to post synaptic neuron.

Back 114

Action potential reaches end bulb & opens voltage-gated Ca+2 channels. Ca+2 flows inward and causes exocytosis of neurotransmitter (NT). NT crosses synaptic cleft and binds to ligand-gated receptors on postsynaptic membrane. Causes Na+ or K+ gates to open, resulting in depolarization or hyperpolarization. If potential reaches threshold it triggers action potential in axon.

Front 115

Why may electrical synapses work in 2 directions but chemical synapse only in 1 direction?

Back 115

In electrical synapse (gap junctions), ions may flow equally in both directions so either can be presynaptic. At chemical synapse, one neuron releases neurotransmitter and other has receptors for the NT, so action potential can only move in 1 direction.