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Human Physiology > Nervous System > Flashcards

Nervous System Flashcards

1
Q

What is the function of the nervous system

A

A communication system that coordinates body function using electrical and chemical signals

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2
Q

What is the organization of the nervous system

A

Central nervous system (brain and spinal cord, interneurons), peripheral nervous system (sensory neurons and motor neurons), and enteric nervous system (digestive)

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3
Q

What types of neurons flow into the CNS vs out

A

Sensory (afferent) in, motor (efferent) out

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4
Q

What kinds of motor neurons are there

A

Somatic (skeletal muscles) and autonomic (smooth muscle, cardiac muscle, endocrine and exocrine glands, and adipose tissue)

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5
Q

What two cells primarily make up the nervous system

A

Neurons and glial cells (support cells)

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6
Q

What is the function of the myelin sheath

A

To speed up communication between neurons by insulating

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7
Q

What is the makeup of a neuron

A

Dendrite (input where signals are received), cell body/soma (nucleus), trigger zone (integration and spike initiation), axon (long distance conduction), and presynaptic axon terminal (signal output)

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8
Q

What are the nodes of Ranvier

A

The space between Schwann cells in the myelin sheath where the AP must be regenerated

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9
Q

What two glial cells can form a myelin sheath

A

Oligodendrocytes (in CNS, can wrap up to 15 axons), and Schwann cells (in PNS, wrap 1 axon)

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10
Q

Define presynaptic and postsynaptic cells

A

Presynaptic delivers the signal at a synapse and postsynaptic receives that signal

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11
Q

What are the two kinds of electrical signals in neurons

A

Graded potentials (local, from input region to trigger zone), and action potentials (long distance, from trigger zone to presynaptic axon terminal)

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12
Q

At the trigger zone what kind of electrical signals are present

A

Both graded potentials and action potentials

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13
Q

What are the 4 characteristics of graded potentials

A

Originate in input region because of opening of gated channels, decrease in amplitude with distance, amplitude and duration matches that of the stimulus, can be excitatory or inhibitory

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14
Q

What does it mean for graded potentials to be excitatory or inhibitory

A

Depending on ion flow, they can depolarize the cell and make it easier to produce AP (excitatory), or hyper polarize the cell and make it harder to produce AP (inhibitory)

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15
Q

What are the two kinds of graded potentials

A

Receptor potential (starts in sensory neuron, ligand/mechanical/voltage gated) and synaptic potential (EPSP or IPSP in interneurons and motor neurons, ligand gated)

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16
Q

What is a subtype of synaptic graded potentials

A

End-plate potential in skeletal muscle (can only excite, ligand gated)

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17
Q

How does a graded potential trigger an action potential

A

The summation of different graded potentials depolarize the cell, via opening of gated channels, past a certain threshold

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18
Q

What happens depending on where a graded threshold adds up to in relation to the threshold

A

Subthreshold = no AP, suprathreshold = AP, at threshold = 50/50 chance of AP

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19
Q

Which electrical signal is faster

A

Action potentials

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20
Q

What are the characteristics of action potentials

A

Don’t decrease in amplitude as the propagate, all-or-none (don’t summate, must reset)

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21
Q

How does action potential relate to the stimulus

A

Amplitude of the stimulus relates to AP frequency, stimulus duration is proportional to the amount of time that the AP is being produced

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22
Q

What types of channels are used in action potential in neurons and skeletal muscle

A

Voltage-gated channels (H-H Na+ and H-H K+)

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23
Q

What are the characteristics of the H-H Na+ channel

A

2 gates, closed when resting or depolarized, opens to let Na+ into the cell (depolarizes cell), time dependent inactivation, positive feedback loop

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24
Q

What are the characteristics of the H-H K+ channel

A

1 gate, closed when resting or repolarized, opens to allow K+ to flow out (hyperpolarizes), delayed compared to sodium

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25
Q

About how much depolarization is needed to activate H-H Na+ and H-H K+

A

~15-20 mV

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26
Q

What stops the H-H Na+ positive feedback loop

A

Time dependent inactivation of the H-H Na+ and the delayed opening of voltage-gated K+ channels

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27
Q

What is afterhyperpolarization

A

Period of time below the resting membrane potential (caused because voltage-gated K+ channels don’t open until Vrest is reached, then take time to close)

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28
Q

What are the refractory periods

A

During and following an AP, absolute = no excitability/can’t produce AP, relative = little bit later, can produce some AP (stronger over time)

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29
Q

What state are channels in during each refractory period

A

Absolute = Na+ opens, then inactivates and K+ opens, relative = both channels are resetting

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30
Q

What causes AP to propagate/regenerate

A

Local depolarization (can’t go backwards because of refractory period)

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31
Q

What is another term for the speed of propagation of an AP

A

Conduction velocity

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32
Q

What 2 mechanisms increase conduction velocity

A

Diameter of the axon (larger = faster, bc/ small diameter creates resistance) and myelination of an axon (more myelin = more insulation = faster)

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33
Q

What is saltatory conduction

A

AP propagation through myelinated axons

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34
Q

What are the 2 types of synapses

A

Electrical and chemical

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35
Q

What is a characteristic of electrical synapses

A

Gap junctions (channels btwn. cells) that allow for synchronized activity and rapid signal conduction in both directions

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36
Q

What are the 4 characteristics of chemical synapses

A

Paracrine signaling, majority of synapses, most NTs are stored in vesicles and exocytosed in response to AP, slower but more flexible with opportunities for amplification

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37
Q

What do neurotransmitters diffuse across

A

The synaptic cleft

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38
Q

What is the purpose of action potential

A

To open voltage-gated Ca2+ channels for exocytosis of synaptic vesicle contents

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39
Q

What characteristics of APs does the release of neurotransmitters/neurocrines depend on

A

The frequency of AP (determines how much NT will be secreted) and the duration of the spike train (time releasing NT)

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40
Q

What are the major neurocrines of the PNS

A

Acetylcholine (ACh), norepinephrine (NE), and epinephrine (E)

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41
Q

What are the postsynaptic receptor types

A

ACh receptors (nicotinic and muscarinic) and adrenergic (alpha 1,2; beta 1, 2, 3)

42
Q

What are the 2 basic receptor groups

A

Ionotropic (directly-gated, ligand-gated, channel protein) and metabotropic (indirectly-gated, GPCR/RE)

43
Q

What terminates neurotransmitter activity

A

Inactivation (breakdown of ACh in synaptic cleft using enzymes), reuptake (NE and E transported out of the synaptic cleft), and diffusing away into the blood (not major)

44
Q

What does the afferent division of the PNS do

A

Detects, encodes, and transmits signals about the internal and external environment to CNS

45
Q

What is a phasic receptor

A

Rapidly adapting (only relay information about when the stimulus starts and stops)

46
Q

What is a tonic receptor

A

Slowly adapting (continuously responds throughout stimulus duration)

47
Q

What are the special sense receptors

A

Have specialized organs devoted to them: tase, vision, hearing, equilibrium, and smell (olfaction)

48
Q

What are somatosensory receptors

A

Collect information from cutaneous sensations (surface): touch, pain, skin temperature, and proprioceptive sensations (muscles and joints): muscle length and force, joint position

49
Q

What are interoceptors

A

For visceral senses, detect stimuli within internal organs (e.g. chemoreceptors, baroreceptors, osmoreceptors) –> Monitor internal environment

50
Q

What is somatotopy

A

The spinal cord is organized based on where the information/signal is going to

51
Q

What are the sensory parts of the spinal cord

A

Dorsal root (cell bodies stored in dorsal root ganglion apart from spinal cord) and dorsal horn (somatic and visceral)

52
Q

Where are decussations (crossing over)

A

Medulla and dorsal column-medial lemniscus tract (fine touch, proprioception, vibration) and spinal cord in anterolateral tract (nociception, temperature, coarse touch

53
Q

What are the characteristics of the thalamus

A

Relay station (not for olfaction) with many nuclei (one for each type of sensory information)

54
Q

What are the autonomic control centers of the brain

A

Forebrain (diencephalon - hypothalamus) and brain stem (medulla oblongata and pons)

55
Q

What types of things are under autonomic control

A

Temperature control, water balance (release of vasopressin), eating behavior and appetite, urinary bladder, blood pressure control, and respiratory center

56
Q

Where is sensory information processed

A

In the cerebral cortex (in charge of perception/brain’s interpretation of sensory stimuli and planning of movements)

57
Q

What does the motor cortex control and where do they travel?

A

Somatic motor neurons (descends through corticospinal tracts in spinal cord that cross at medulla)

58
Q

What does the somatic motor division control

A

Skeletal muscle via somatic (alpha) motor neurons

59
Q

What are 3 characteristics of alpha motor neurons

A

Control skeletal muscle contractions (mostly volunatry), under tonic control, neuron starts in ventral horn and leaves via ventral root

60
Q

What are the characteristics of the neuromuscular junction

A

Somatic motor neurons (always excitatory) release ACh onto sarcolemma

61
Q

What type of receptors does the sarcolemma contain

A

Nicotinic acetylcholine receptors (nAChR): ionotropic (ligand-gated that cause depolarization) in motor end-plate

62
Q

How does a nAChR cause function

A

Binding of ACh opens an ion channel that lets in 2Na+ and out 1K+ (causes depolarization) that creates a graded/end-plate potential

63
Q

What does the end-plate potential do

A

Causes voltage-gated Na+ channels to open in muscle membrane leading to sarcolemmal action potential that propagates down a T-tubule and causes muscle contraction (always supra-threshold)

64
Q

How long does ACh have effects for

A

As long as it’s around

65
Q

What does acetyltransferase do

A

Makes acetylcholine from acetyl CoA (comes from Krebs cycle) and choline (from diet)

66
Q

What does acetylcholinesterase (AChE) do

A

Enzyme on postsynaptic cell membrane that breaks down ACh into acetate (waste product) and choline (transported and recycled)

67
Q

What are cholinergic neurons and receptors

A

Neuron makes and releases ACh as a signal while the receptor (nicotinic, muscarinic) binds and responds to it

68
Q

What are adrenergic neurons and receptors

A

Neuron makes and releases E/NE as a signal and receptor (alpha and beta) binds and responds

69
Q

What are different names for types of neurocrines

A

Cholinergic (relates to ACh), adrenergic (NE/E), dopaminergic, serotonergic, GAB, histaminergic, glutamatergic

70
Q

What sorts of things does the autonomic division of the PNS control

A

Cardiac and smooth muscle, exocrine and endocrine glands, lymphoid and some adipose tissue), mostly involuntary

71
Q

What are the two branches of the autonomic division of the PNS

A

Parasympathetic and sympathetic (most effectors are connected to both, can be excitatory and inhibitory)

72
Q

What is autonomic tone

A

Background activity that allows for a balance between the parasympathetic and sympathetic divisions)

73
Q

What responses does the autonomic nervous system create and what influences them

A

Creates autonomic, endocrine, and behavioral responses, influenced by the cerebral cortex and limbic system

74
Q

What sorts of autonomic neurons are only innervated by one branch

A

Sweat glands and smooth muscle of most blood vessels are only innervated by the sympathetic nervous system

75
Q

How many neurons are in an autonomic pathway

A

At least 2 in series (meet in an autonomic ganglion)

76
Q

What are the characteristics of the sympathetic pathway

A

Short preganglionic neurons (in thoracic and lumbar segments), ong postganglionic neurons

77
Q

What are the 4 characteristics of the parasympathetic pathway

A

Vagus nerve contains most of the fibers, ganglia located primarily on or near target organs, long preganglionic neurons (brain stem and sacral region), and short postganglionic neurons

78
Q

What are the receptors for ACh

A

Cholinergic (nicotinic or muscarinic)

79
Q

What are the receptors for NE/E

A

Adrenergic (alpha or beta)

80
Q

What has nicotinic receptors

A

Skeletal muscle, post-ganglionic neurons in parasympathetic, sympathetic, and adrenal sympathetic pathways

81
Q

What has muscarinic receptors

A

Target tissues for parasympathetic pathways

82
Q

What has adrenergic receptors

A

Target tissues for sympathetic and adrenal sympathetic pathways

83
Q

What kinds of receptors are metabotropic

A

Muscarinic and adrenergic

84
Q

What do autonomic postganglionic neurons synapse at

A

Varicosities

85
Q

Which neurotransmitter lingers longer

A

NE (must be broken down by MAO)

86
Q

Which receptor type is utilized for vasoconstriction

A

Alpha

87
Q

What type of pathway is activated to vasoconstrict

A

PLC

88
Q

What type of receptors cause vasodilation

A

Beta-2

89
Q

What type of pathway is activated for vasodilation

A

cAMP

90
Q

How does NE inactivate at a NMJ

A

NE diffuses away from the synapse or is removed, it can be taken back into synaptic vesicles for re-release, or it can be metabolized by MAO

91
Q

What are the autonomic reflex control centers

A

Pons, medulla, and hypothalamus

92
Q

What sensory neurons mediate spinal reflexes

A

Proprioceptors

93
Q

What is the effector for spinal reflexes

A

Skeletal (extramural) muscle fibers

94
Q

What are the efferent neurons in spinal reflexes

A

Somatic alpha motor neurons

95
Q

What does the golgi tendon organ do

A

In line with muscle fibers, monitors muscle force and mediates the tendon reflex to regulate that muscle force

96
Q

What does the muscle spindle organ do

A

In line with the tendon, it monitors muscle strength (usually unexpected) to mediate the stretch/patellar/knee reflex and regulate muscle length

97
Q

What is the pathway in the golgi tendon reflex

A

Polysynaptic tonic control: Ib afferent tells the Ib inhibitory interneuron that force increased, that interneuron excites the muscle less to relax the muscle

98
Q

What type of channels does the Ib afferent neuron have

A

Mechanically-gated channels that react to graded (receptor) potentials

99
Q

What type of channels does the Ia afferent neuron have

A

Mechanically-gated channels that react to graded (receptor) potentials

100
Q

What are the muscle spindle reflex pathways

A

Stretch-sensitive afferent that monitors muscle length and 2 efferent pathways (1 contracts agonist, 1 relaxes antagonist)

101
Q

What happens when muscle length increases (tendon tapped)

A

Monosynaptic pathway contracts quadriceps, polysynaptic pathway activates Ia inhibitory interneuron and relaxes the hamstring

Human Physiology (12 decks)

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