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anatomy > nerve tissue > Flashcards

nerve tissue Flashcards

Describe the organization of the nervous system. Describe the neuroglia of the CNS and PNS. Describe the parts and classifications of neurons. Describe the generation and propagation of electrical signals in neurons.

1
Q

what is the nervous system divided into?

A

CNS and PNS

central nervous system and peripheral nervous system

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2
Q

what does the CNS consist of?

A

The brain and spinal cord

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3
Q

what does the PNS consist of?

A

Nerves that branch off the brain and spinal cord.

Cranial and Spinal nerves

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4
Q

what is a nerve?

A

is a bundle of hundreds to thousands of axons plus associated connective tissue and blood vessels that lies outside the brain and spinal cord.

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5
Q

what can the PNS be further divided into?

A

SNS, ANS, and ENS

somatic nervous system
autonomic nervous system
enteric nervous system

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6
Q

Somatic nervous system (SNS)

A

Transmits sensory signals generally related to external stimuli, from receptors in the skin, muscles, joints, and special sense organs. Sends motor signals to skeletal muscles.

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7
Q

Autonomic nervous system (ANS)

A

transmits sensory signals related to internal stimuli from receptors in visceral organs and tissue, and motor signals to the cardiac muscle, smooth muscle and glands that are located within the viscera of the body.

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8
Q

Enteric nervous system (ENS)

A

a collection of sensory and motor nerves and are contained entirely within the gastrointestinal tract.

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9
Q

what is the sympathetic division?

A

a division of the autonomic nervous system, descending from the peripheral nervous system.

The sympathetic division helps support exercise or emergency actions—the so-called “fight-or-flight” responses.

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10
Q

what is the parasympathetic division?

A

a division of the autonomic nervous system, descending from the peripheral nervous system.

parasympathetic part takes care of “rest-and-digest” activities. Neurons of this division assist in slowing down the heart rate.

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11
Q

what are the two types of cells in which nervous tissue consists of?

A

Neuroglia, Neurons

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12
Q

what are neuroglia?

A

Neuroglia are the support cells that provide structure to the nervous system and nourish and protect neurons.

Smaller, but much more abundant than neurons

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13
Q

what are neurons?

A

Neurons are functional unit cells which transmit electrical signals around the body related to various sensory, motor and integrative functions.

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14
Q

What does the sensory function of the nervous system involve?

A

Detecting internal and external stimuli through sensory receptors, then transmitting this information to the brain and spinal cord via cranial and spinal nerves.

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15
Q

What is the integrative function of the nervous system?

A

Processing sensory information by analyzing it and making decisions for appropriate responses, also known as integration.

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16
Q

Describe the motor function of the nervous system.

A

Activating effectors (muscles and glands) through cranial and spinal nerves to elicit appropriate motor responses, such as muscle contraction or gland secretion.

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17
Q

fill in the blank:
The CNS and PNS have different types of _______

A

neuroglia

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18
Q

what are the different types of neuroglia within the CNS?

A

Astrocytes
Oligodendrocytes
Ependymal cells
Microglia

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19
Q

what are the different types of neuroglia within the PNS?

A

Satellite cells
Schwann cells

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20
Q

what are astrocytes?

A

Star shaped. Main support cell in the CNS as they create a supportive framework for neurons and guide their development and help to maintain the blood brain barrier.

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21
Q

what are Oligodendrocytes?

A

located in the CNS and produce myelin, a protective covering around nerve fibers. This sheath helps electrical impulses travel efficiently along the nerve cells.

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22
Q

what are microglia?

A

migrate around the CNS and act as the main immune defense. They help protect the brain and spinal cord by detecting and removing harmful substances, such as damaged cells and pathogens. Additionally, microglia play a role in regulating inflammation and supporting the health of neurons.

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23
Q

what are ependymal cells?

A

specialized cells that line the ventricles of the brain and the central canal of the spinal cord. They are involved in producing cerebrospinal fluid (CSF), a clear liquid that cushions the brain and spinal cord, provides nutrients, and removes waste products. Additionally, ependymal cells help circulate CSF throughout the central nervous system.

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24
Q

what are satellite cells?

A

Create a supportive framework

Regulate the composition of the interstitial fluid

“Astrocyte of the PNS”

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25
Q

what are Schwann cells?

A

Produce the myelin sheaths of (some) PNS neurons

“Oligodendrocyte of the PNS”

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26
Q

what is myelin?

A

white fatty substance that is wrapped around the axons of some neurons and provides protection to the axon and increases the speed in which electrical signals are propagated down it.

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27
Q

what is white matter?

A

Regions of the brain and spinal cord that contain an abundance of myelinated axons appear white, and therefor are referred to as white matter.

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28
Q

what is grey matter?

A

Regions of the brain and spinal cord that contain an abundance of unmyelinated axons and cell bodies appear dark and referred to as grey matter.

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29
Q

What are the myelin producing neuroglia in the CNS and PNS?

A

Oligodendrocytes and Schwann cells

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30
Q

function of the myelin?

A

Protects/insulates the axon

Increases the conduction speed of the axon

31
Q

what is MULTIPLE SCLEROSIS (MS)

A

Autoimmune disease that leads to progressive destruction of the myelin sheaths of neurons in the CNS (affected areas form “plaques”)

32
Q

what does a neuron typically consist of?

A

Neurons typically have three main parts; cell body, dendrites and axon.

33
Q

what is the cell body?

A

expanded potion which contains most of the typical cellular parts. For instance, the nucleus, ribosomes and mitochondria.

34
Q

what are the dendrites?

A

branch structures that transmit graded potentials that are generated in response to specific incoming stimuli, toward the cell body.

“input”

35
Q

what is the axon?

A

The axon is a single long branch that transmits action potentials away from the cell body toward axon terminals. Which relay the signals toward another neuron or effector cell such as a muscle cell or gland cell.

“output”

36
Q

What are the three basic functions of the nervous system?

A

Sensory (input)
Integrative (process)
Motor (output)

37
Q

What is a cluster of cell bodies within the CNS referred to as?

A

the nucleus

38
Q

what is a bundle of axons within the CNS referred to as?

A

tract

39
Q

what is a cluster of cell bodies within the PNS referred to as?

A

Ganglion

40
Q

what is a bundle of axons within the PNS referred to as?

A

nerve

41
Q

What direction do action potentials typically travel along an axon, away from which part of the neuron?

A

Action potentials generally travel in one direction along an axon, away from the cell body.

42
Q

How are axons organized in the CNS regarding the transmission of action potentials?

A

In the CNS, axons are grouped into bundles that only transmit action potentials in one direction.

43
Q

In the peripheral nervous system (PNS), what is unique about the direction of signal transmission in nerves?

A

Most nerves in the PNS contain axons that transmit signals in both directions, but it’s crucial to note that each axon within the nerve only transmits signals in one direction.

44
Q

how are neurons classifed?

A

based on number of branches that extend out from the cell body.

45
Q

multipolar neuron:

A

Many dendrites and one axon

most common

46
Q

Bipolar neuron:

A

dendrites merge into a single branch that connects to the cell body along with the axon.

Found in special sense organs (retina and inner ear).

47
Q

unipolar neuron:

A

dendrites merge into a singular branch that is continuous with the axon. With the cell body sitting on the side of the axon somewhere along its length

Sensory neurons of the PNS

48
Q

Sensory (Afferent) Neurons

A

Deliver signals from peripheral receptors to the CNS

Primarily unipolar neurons whose cell bodies are located in peripheral sensory ganglia

49
Q

Interneurons

A

Transmit signals between sensory and motor neurons
(i.e., distribute sensory information and coordinate motor activity)

Primarily multipolar neurons that are contained entirely within the CNS

50
Q

Motor (Efferent) Neurons

A

Deliver signals from the CNS to effectors (e.g., muscle cells, glands) in the periphery

Primarily multipolar neurons whose cell bodies are located in spinal cord nuclei

51
Q

How are sensory signals typically transmitted within the peripheral nervous system (PNS)?

A

Sensory signals are transmitted from the periphery to the central nervous system (CNS), moving from the outside in.

52
Q

Describe the direction of sensory signal transmission within the central nervous system (CNS).

A

Within the CNS, sensory signals are transmitted from lower centers toward higher centers, following a bottom-up pathway.

53
Q

What is the direction of motor signal transmission within the central nervous system (CNS)?

A

Motor signals within the CNS are transmitted from higher centers toward lower centers, representing a top-down pathway.

54
Q

How are motor signals typically transmitted within the peripheral nervous system (PNS)?

A

Motor signals are transmitted from the CNS to the periphery within the PNS, moving from the inside out.

55
Q

What is the resting membrane potential of neuronal cell membranes?

A

a difference in electrical charge between the inside and outside of the cell membrane.

56
Q

Why does the resting membrane potential occur in neuronal cell membranes?

A

The resting membrane potential arises from a difference in the number of positive and negative ions on either side of the cell membrane, with more negative ions present within the cell.

57
Q

What does the negative value of the resting membrane potential indicate?

A

The negative value of the resting membrane potential signifies that the inside of the cell is more negatively charged compared to the outside.

58
Q

What does it mean for neurons and muscle cells to be “electrically excitable”?

A

Being “electrically excitable” means that their resting membrane potential changes in response to certain stimuli.

59
Q

What are the two forms of changes in resting membrane potential observed in neurons?

A

graded potentials, which occur in dendrites and cell bodies, and action potentials, which occur in axons.

60
Q

What causes a graded potential to occur in a neuron?

A

A graded potential arises due to the opening or closing of mechanically gated channels in the neuron’s membrane.

61
Q

what is an excitatory graded potential?

A

An excitatory graded potential makes the membrane potential more positive, bringing it closer to the threshold required to initiate an action potential

62
Q

what is an inhibitory graded potential?

A

makes the membrane potential more negative, moving it further from the threshold required to initiate an action potential.

63
Q

How does the amplitude of a graded potential vary?

A

varies depending on the strength of the stimulus that triggers it.

64
Q

Describe the concept of spatial and temporal summation in relation to graded potentials.

A

Spatial and temporal summation refers to the process by which the effects of multiple graded potentials are added together, producing a net effect. This occurs when graded potentials generated at different locations on the neuron (spatial summation) or at different times (temporal summation) are combined to reach the threshold required to trigger an action potential.

65
Q

What is an action potential?

A

An action potential is a relatively large change in the cell membrane potential, characterized by a constant magnitude as it travels along the cell membrane, like a tidal wave.

66
Q

When is an action potential activated in a neuron?

A

An action potential is activated when the membrane potential of a neuron reaches a threshold level. It is always excitatory, causing the membrane potential to become more positive.

67
Q

How do action potentials differ from graded potentials in terms of summation?

A

Unlike graded potentials, action potentials cannot undergo summation.

68
Q

What happens when an action potential reaches a synaptic terminal?

A

it is transmitted to another neuron or effector across a synapse.

69
Q

What are the two types of synapses?

A

electrical synapses and chemical synapses.

70
Q

Describe electrical synapses.

A

Electrical synapses involve direct transmission via small connecting channels that allow electrical signals to pass directly from one neuron to another.

71
Q

Explain chemical synapses.

A

Chemical synapses involve indirect transmission via the release of neurotransmitters. Neurotransmitters are released from the synaptic terminal of one neuron and bind to receptors on the membrane of the receiving neuron or effector, thereby transmitting the signal.

72
Q

Neurotransmitters have variable effects:

A

Excitatory – Produces a graded potential that brings the neuron’s cell membrane closer to threshold

Inhibitory – Produces a graded potential that brings the neuron’s cell membrane further from threshold

73
Q

Neurons constantly receive input from:

A

hundreds/thousands of other neurons

74
Q

if the cell membrane reaches ___ an ___ ___ will be generated in the neurons axon

A

If the cell membrane reaches threshold
an action potential will be generated in
the neuron’s axon

anatomy (34 decks)

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