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Anatomy and physiology > Neurons > Flashcards

Neurons Flashcards

1
Q

The nervous system

A

receives information, processes information, and sends signals to the muscles and glands to deliver the appropriate response.

Intergrates and controls the other systems

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2
Q

Nervous tissue

A

is responsible for the communication between the cells of the body by forming a system of electrical impulses that communicate very rapidly.

Wiring of the body

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3
Q

What are the two main divisions of the central nervous system?

A

Central nervous system (CNS) and peripheral nervous system (CNS)

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4
Q

Central nervous system

A

includes the brain and spinal cord

The skull protects the brain and the vertebrae protect the spinal cord

Sends signals and impulses to and receives impulses from the peripheral nervous system

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5
Q

nuclei

A

collection of cell bodies inside the CNS.

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6
Q

tracts

A

collection of nerve axons in the central nervous system

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7
Q

peripheral nervous system

A

includes all nerves not in the brain or spinal cord

Includes cranial and spinal nerves

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8
Q

Brainstem

A

regions include the midbrain, pons, and medulla

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9
Q

Where do cranial nerves and peripheral nerves project from

A

CN project from the brainstem and PN project from the either side of the vertebrae.

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10
Q

What do CN and PN innervate?

A

CN- the face, head, and neck f

PN- the rest of the body including the trunk and extremities

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11
Q

Ganglia

A

collection of cell bodies inside the PNS

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12
Q

Nerves

A

collection of nerve axons in the PNS

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13
Q

Two divisions of the PNS

A

Sensory or Afferent division and Motor or Efferent division

The peripheral system connects all parts of the body to the CNS

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14
Q

Sensory organs

A

The peripheral nervous system receives impulses from the sensory organs via afferent division and then relays signals or impulses from the CNS to muscles and glands

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15
Q

Glands

A

receives information from the CNS via motor or efferent division.

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16
Q

Two divisions of the Efferent system

A

Somatic and automatic systems

somatic system nerves - under conscious (voluntary) control

controls movement if the skeletal muscles, skin, and joints

automatic system nerves- controls the glands and smooth muscles of the internal organs.

Not under voluntary/conscious control

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17
Q

Two divisions of the automatic nervous system

A

sympathetic and parasympathetic system

sympathetic - prepares body for vigorous musclular activity, stress, and emergencies

parasympathetic system generality operates during normal situations, permits digestion, and conserves energy.

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18
Q

Nuerons

A

nerve cells that conduct electrical impulses and relay information throughout the body.

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19
Q

Three parts of a neuron

A

dendrites, cell body, and axons

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20
Q

Neuron facts

A

They do not undergo mitosis/cell division

Can survive an entire person’s lifetime, which is why brain and spinal cord damage are so serious.

Any neurons that die due to brain damage can not be replaced

neurons can survive just minutes without oxygen

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21
Q

Neuron cell body

A

synthesizes all nerve cell products

consists of large nucleus with surrounding cytoplasm containing normal organelles

information is sent and received in the same direction within a neuron.

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22
Q

dendrites

A

are the receiving end of a neuron

these are numerous short extensions that emanate from the cell body, which receive information from the neurons and conduct those nerve impulses toward the cell body

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23
Q

axon

A

the single axon conducts nerve impulses away from the cell body to its axon terminals

vary in length -being very short or very long (up to 3 feet)

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24
Q

What are axons composed of?

A

cell components like the cell body but lack rough endoplasmic reticulum

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25
Q

What do axons depend on

A

the neuron’s cell body to send the necessary proteins down the length of the axon

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26
Q

What does the cell body of a neuron cell contain?

A

nucleus and other organelles typically found in other cells, except for centrioles, which are not capable of mitosis

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27
Q

Main function of the cell body

A

to manufacture neurotransmitters

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28
Q

Neurotransmitters

A

are chemicals stored inside secretory vesicles (axon terminal vesicles) at the end of axon terminals

when neurotransmitters are released by the axon vesicles, they carry the transmission of the nerve impulse from one neuron to another

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29
Q

synapse

A

neurotransmitters are emitted across a synapse to the dendrite of another neuron

a synapse is a gap between two neurons as neurons do not physically touch one another

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30
Q

presynaptic neuron

A

means before the synapse

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31
Q

postsynaptic neuron

A

a neuron found after the synapse

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32
Q

How are neurotransmitters sent?

A

from the presynaptic neuron through the synapse to the postsynaptic neuron.

the message continues in the same manner from one neuron to the next

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33
Q

How are neurons classified?

A

according to the number of extension from their cell body as multipolar, bipolar and unipolar

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34
Q

Multipolar neurons

A

have three or more extensions from their cell body

they have one axon and many dendrites

can be called motor neurons

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35
Q

bipolar neurons

A

have a central body with two extensions

these are found within in the body, as special receptor cells in the visual and olfactory systems.

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36
Q

unipolar neurons (pseudounipolar)

A

have one extension off the cell body that branches into two: one central process running to the CNS.and another peripheral process running to the sensory receptor

these neurons are sensory neurons in the peripheral nervous system

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37
Q

How are neurons classified functionally?

A

sensory, motor, and interneurons

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38
Q

sensory neurons

A

afferent

unipolar

function to carry information from the peripheral to the central nervous system

most sensory neurons carry impulses from the skin or internal organs to the CNS

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39
Q

Interneurons

A

called association neurons are found only in the CNS

typically multipolar neurons

transmit impulses within different parts of the CNS

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40
Q

Motor neurons

A

efferent

multipolar neurons which send messages form the CNS to the peripheral

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41
Q

nerve

A

consists of hundreds of thousands of axons wrapped together in connective tissue.

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42
Q

ganglia

A

in the PNS the cell bodies of neurons are grouped together in masses called ganglia, which is part of a single nerve

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43
Q

neuroglial cells

A

highly important for neuron function

support cells for neurons

neurons require a highly specific environment to survive and conduct electrical impulses efficiently

help to support neurons to enable them to thrive in their needed environment

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44
Q

Schwann cells

A

the peripheral nerve axon is coated in short sections called schwann cells

a special type of neuroglial cell found in the PNS and composed of a white fatty layer called myelin sheath

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45
Q

myelin sheath

A

rolled around the axon, insulating the nerve fiber from others and increasing the speed of nerve impulses

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46
Q

unmyelinated fibers

A

common in gray matter of the brain and spinal cord in which schwann cells do not wrap around the axon but are loosely associated with the axon

the schwann cells insulating sections are not continuous, having gaps between them called nodes of ranvier

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47
Q

Nodes of ranveir

A

The Schwann cells insulating sections are not continuous having gaps between them called nodes of ranveir

at these exposed nodes, the nerve impulse is forced to jump to the next node in a manor called saltatory conduction.

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48
Q

satellite cells

A

surround the cell bodies of peripheral neurons helping to regulate the cell body environment

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48
Q

saltatory condunction

A

at exposed nodes (nodes of ranveir), the nerve impulse is forced to jump to the next node in a manor called saltatory conduction - greatly increasing the nerve impulse transmission along the axon

49
Q

axonal regeneration

A

Neurons can not regrow, but axons in the PNS can under certain circumstances.

If peripheral nerves are servered in an injury, the schwann cells grow ahead of the axon creating a path for the axon to follow

it is possible for axons to regrow after injury to peripheral nerve, although growth is very slow

50
Q

Neuroglial cells of the CNS

A

ependymal cells, oligodendrocytes, astrocytes, microglial cells

51
Q

ependymal cells

A

circulate cerebrospinal fluid

allow fluid exchange between brain and spinal cord and cerebrtospinal fluid.

52
Q

cerebrospinal fluid CSF)

A

a clear fluid that only circulates in the brain and spinal cord

53
Q

Oligodendrocytes

A

act as insulation of the CNS axons

54
Q

Astrocytes

A

control the chemical environment of neurons by wrapping around blood capillaries

this physical barrier is called the blood brain barrier

55
Q

Blood brain barrier

A

a physical barrier made by astrocytes

allows the passage of only certain substances into the CNS

56
Q

microglial cells

A

protect the CNS by scavenging dead cells and infectious microorganisms

57
Q

polarized

A

at rest, the plasma membrane is said to be polarized

one side has a different charge than the other

58
Q

resting potential

A

when an axon is not conducting an impulse this difference in electrical charge is called resting potential or resting state of neuron

equal to -70 mV (milivolts)

charge is negative because the inside of the axon’s cell membrane is 70mV less than the outside of the membrane

59
Q

sodium potassium pump

A

uses active transport to carry ions across the plasma membrane.

the pump uses an integral carrier protein that for ever 3 sodium ions (Na+) pumped out, two potassium ions (K+) are pumped in.

pump must be in constant operation because Na+ and K+ will naturally diffuse back to where they originated

60
Q

Why is there a positive change on the outside of the cell membrane?

A

The plasma membrane is more permeable to K+ diffusing outward and because more Na+ ions are being pumped outward than K+ pumped inward, a relative positive charge develops and is maintained on the outside of the membrane

61
Q

action potential

A

if the axon is stimulated to conduct a nerve impulse, there is a rapid change in the polarity called an action potential

the resting potential becomes an action potential if the membrane becomes depolarized

once an action potential occurs it travels it continues it continues through the entire length of the axon

62
Q

depolarization

A

first the membrane potential becomes more positive (depolarization)

indicating that the inside of the membrane is now more positive than the outside

then it returns to normal (re-polarization)

63
Q

re-polarization

A

the potential returns to normal after being depolarized, indicating that the inside of the axon is negative again.

64
Q

sodium gates and potassium gates

A

the action potential is due to special protein lined channels in the membrane, which can open to allow either sodium or potassium ions to pass through

these channels and their gated are voltage activated

as proteins respond to changes in voltage with changes in shapes

65
Q

resting potential

A

during resting phase, both sodium and potassium gates are closed

66
Q

depolarization

A

the sodium gates are open

sodium rushes into the axon during the depolarization phase of action potential.

voltage travels to zero and then on up to +40mV

67
Q

after polarization

A

also called hyper polarization.

Poatssium gates are slow to close and there is an undershoot of the action potential

the voltage drops below -70mV and then returns to -70 mV as the resting state begins

67
Q

repolarization

A

the sodium gates close, and potassium gated open allowing potassium to rush out of the axon

this returns a negative voltage to the inside of the axon

68
Q

self propagating

A

because the ion channels are prompted to open whenever the membrane potential decreases (depolarizes) in an adjacent area

The action potential travels along the axon like a wave

69
Q

all-or-nothing

A

an action potential is an all or nothing response, either occurring or not.

No variation exists in the strength of a single impulse

70
Q

How can intensity of a sensation vary if there is only a single strength in an action potential?

A

intensity of a sensation (minor or major pain) is distinquished
by the numbers of neurons stimulated and the frequency with which the neurons are stimulated

71
Q

synapse

A

a minute fluid-filled space between an axon terminal of the sending (presynaptic) neuron and the dendrite of the receiving (postsynaptic) neuron

72
Q

electrochemical

A

a transmission of nerve impulses are electricalchemical in nature as chemicals called neurotransmitters allow to the signal to jump the synaptic gap.

signal moves from electrical (through the neuron) to chemical (in the synapse) to electrical again once the signal reaches the next neuron.

73
Q

Depolarization

A

when a nerve impulse reaches the end of an axon, voltage gated calcium ions open.

As Ca+ rushes in, it causes vesicles containing the neurotransmitters to fuse with the plasma membrane and release the neurotransmitter in the synapse

When neurotransmitter released binds with a receptor on the next neuron, sodium ion (Na+) channels in the receiving dendrites open.

Depolarization occurs in the next neuron, and the impulse is propagated forward to another neuron or to a target organ **ALWAYS in one direction.

74
Q

acetylcholinesterase (cholinesterase)

A

breaks down the neurotransmitter acytelcholine

75
Q

What happens once a neurotransmitter is released into the synapse?

A

it only has a short time to act.

some synapses contain enzymes that rapidly inactivate the neurotransmitter

ex. acetylcholinesterase

in others the synaptic ending rapidly reabsorbs the neurotransmitters.

some neurons repackage the neurotransmitters into synaptic vesicles while others chemically breakdown the neurotransmitters

76
Q

Why do neurontransmitters have a short existence?

A

the short existence of neurotransmitters in the synapse is to prevent continuous stimulation of postsynaptic membranes.

77
Q

Inhibition

A

Neurotransmitters are short lived in the synapse to prevent continuous stimulation of postsynaptic membranes.

Prevention of continuous stimulation is called inhibition

78
Q

Norepinephrine and epinephrine

A

neurotranmitters produced by the adrenal glands

79
Q

dopamine

A

is a specialized brain neurotransmitter that regulate emotional responses and muscle tone

80
Q

acetylcholine

A

Neurotransmitter found at neuromuscular junctions (NMJ) in the peripheral nervous system.

The NMJ is located where a motor neuron ends on a muscle instead of another neuron.

81
Q

What happens for a muscle to contract

A

The nervous system must work together with the muscular system.

82
Q

NMJ (neuromuscular junction)

A

the nervous system interacts with the muscular system at NMJ to enable a muscular contraction.

nerve impulse must be sent to muscle by presynaptic motor neuron.

NMJ is a special type of synapse formed between a motor neuron and motor tissue

83
Q

What happens when a nerve impulse reaches the muscle fiber?

A

acetylcholine is released into the synapse.

acetylcholine binds to receptors on the muscle fiber that cause sodium channels to open.

sodium rushes into the muscle cell, triggering an action potential which releases into the sacroplasmic reticulum (special type of smooth ER found in striated muscle tissue.

Calcium is then released from the sarcoplasmic reticulum that causes the muscle to contract.

84
Q

reflexes

A

nearly instantaneous, automatic, and involuntary responses within the nervous system.

start from stimulus inside or outside the body.

come in a variety of forms

85
Q

Subconscious reflexes

A

occur within the body such as regulation of blood sugar by hormones

86
Q

Different reflexes

A

some include shivering in response to body temperature dropping.

when touching a hot surface, the reflux to remove your hand

87
Q

reflexes that involve the brainstem

A

blinking the eye

88
Q

brainstem

A

midbrain, pons, and medulla

89
Q

reflex arc

A

some reflexes only require spinal nerves and spinal cord in an action know as reflex arc

this refers to a neural pathway that nerve impulses travel.

90
Q

how can some reflexes be tested?

A

some reflexes can be tested to examine the function of the nervous system because the arc system passes through the CNS

91
Q

dorsal root

A

sensory informations travels into the spinal cord via the dorsal root

92
Q

ventral root

A

motor information travels out the ventral root of the spinal cord

93
Q

gray matter

A

the gray matter of the spinal cord contains cell bodies of neurons

also where neurons synapse with other neurons (such as interneurons)

94
Q

white matter

A

the white matter of the spinal cord contains the axons and neurons

95
Q

how are the white and gray matter arranged?

A

The spinal cord is located centrally with the white matter surrounding the gray matter.

96
Q

interneurons

A

located within the CNS and connect neurons to each other

97
Q

dorsal root ganglion

A

contains cell bodies of sensory neurons

98
Q

what does the dorsal root contain

A

axons and sensory neurons

99
Q

posterior horn

A

sensory nuerons synapse on cells within the posterior horn of the spinal cord in the gray matter

sensory neurons synapse on interneurons within the gray matter of the spinal cord

interneurons than synapse on motor neurons.

100
Q

anterior horn

A

Motor neuron cell bodies are located in the anterior horn of the gray matter

motor neurons (axons) leave the spinal cord via ventral root

101
Q

spinal nerve

A

contains both sensory and motor neurons from ventral and dorsal roots

102
Q

spinal reflexes

A

this are faster than a conscious decision to move coming from the brain.

they are faster because they involve fewer neurons, but because the electrical signal does not have to travel to the brain and back

spinal reflexes only travel to the spinal cord and back ** which is a much shorter distance

103
Q

examples of stretch reflexes

A

flexor reflex -withdraw your hand from a hot object

stretch reflex- on an opposing muscle to prevent overstretching of its antagonist.

104
Q

How does the reflex arc prevent harm to an organism.

A

a reflex arc provides immediate withdrawal from dangerous stimuli

while all sensory information reaches the brain the advantage of of the reflex arc is production of a response by way of the spinal cord without the need for waiting for the processing by the brain.

in this way, a response occurs in the body even before it is consciously perceived by the brain

105
Q

5 components of a reflex arc

A

the neural pathway that a nerve travels:

  1. the receptor at the end of a sensory neuron reacts to a stimulus.

2.The sensory (afferent) neuron conducts nerve impulses along the afferent pathway towards the CNS

  1. The integration center consists of one or more synapses in the CNS
  2. a motor (efferent) neuron conducts a nerve impulse along the efferent pathway from the integration center to the effector
  3. An effector repsonds to the efferent impulses by contracting (a muscle) or secreting a product (a gland)
106
Q

stretch reflexes

A

are a special type of muscle that protect a muscle against increases in length that may tear or damage the muscle fibers

these are very important in maintaining upright posture

107
Q

muscle spindles

A

are specialized muscle cells that are constantly monitoring the amount of stretch in a muscle

if a muscle becomes overstretched, it triggers a reflex to occur, which contracts the muscle back to its appropriate length

108
Q

patellar reflex

A

one example of a stretch reflex

the patellar reflex is also called a knee jerk reflex used in the physicians office

the patellar reflex tests the stretch reflex of the quadriceps femoris muscle in the thigh.

the primary purpose of this reflex is to prevent the overstretcching of the quadriceps

109
Q

patellar tendon

A

attaches the quadricep muscle to the tibia bone of the lower leg.

quadricep muscle is an extensor muscle of the knee

it raises the lower leg as it contracts, thereby extending the angle of the knee joint.

tapping the patellar tendon when the leg is lower is suspended off a table stretches the tendon which also stretches the quadricep muscle.

110
Q

flexor withdrawal reflex

A

if a very hot object is touched, a pain receptor in the skin generates nerve impulses, which move along the dendrite of a sensory neuron toward the cell body and the CNS.

From the cell body, impulses travel along the axon of a sensory nerve and synapse on many interneurons with the gray matter of the spinal cord

111
Q

excitatory interneurons

A

send excitatory signals to motor neurons, causing muscular contraction.

112
Q

inhibitory interneurons

A

send inhibitory signals to prevent muscle contraction

113
Q

why do cell bodies in neurons lack centrioles?

A

because they do not undergo mitosis so they do not need them

114
Q

why do axons lack rough ER?

A

because they are relying on the cell body to send the proteins they need

115
Q

sensory neurons

A

carry information from PNS to CNS

many found in skin or internal organs to the CNS

116
Q

Interneurons

A

found only in the CNS

typically multipolar

transmit info within a different part of CNS

117
Q

Motor neurons

A

multipolar

send messages from CNS to PNS

118
Q
A

Anatomy and physiology (19 decks)

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