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Biomed Phys > Exam 3 Nervous System 3 > Flashcards

Exam 3 Nervous System 3 Flashcards

1
Q

what is divergence a typical property of?

A

motor pathways

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2
Q

Divergence

A

impulse originates on one motor neuron and it passed downstream to multiple motor neurons

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3
Q

what is convergence a typical property of?

A

sensory pathways

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4
Q

Convergence

A

multiple sensory signals originating from multiple neurons are transmitted to one target neuron

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5
Q

what is divergence a form of?

A

amplification; way that initial signals can amplify as they travel down the pathway to the effector

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6
Q

divergence result

A

recruiting more neurons –> recruit more muscle fibers –> increased force of AP

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7
Q

what is the internal mechanism of control for divergence?

A

lateral inhibition

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8
Q

divergent pathway setup

A

central core of neurons which form the most direct pathway, then you have all these lateral neurons to the side of the core; as the central neurons are stimulated, they stimulate their direct downstream neurons, and they also inhibit the lateral neurons beside them causing them to fire less frequently

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9
Q

how does lateral inhibition occur?

A

the central core neuron axons synapse directly with the downstream neurons; as the central neuron is excited, it is inhibitory on the axon hillock of the lateral neurons and excitatory on the dendrites and soma of the downstream neurons

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10
Q

how does one AP have an excitatory effect on downstream neurons, but an inhibitory effect on lateral neurons?

A

the same NT can have different effects on downstream neurons vs inhibitory neurons because there is a different distribution of receptors on the two types of neurons

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11
Q

what are examples of how one AP has an excitatory effect on downstream neurons and an inhibitory effect on lateral neurons?

A
  • typical Nicotinic receptor on dendrites and soma of downstream neuron that activates sodium channel which polarizes membrane
  • typical Muscarinic receptor on axon hillock of lateral neuron that activates calcium channel which hyperpolarizes membrane making it harder to generate an AP
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12
Q

convergent (sensory) pathways

A

sensory pathways going from peripheral body to CNS (afferent pathways)

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13
Q

what do convergent pathways usually involve?

A

the sorting and integration of multiple different senses (vision, touch, pressure, hearing)

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14
Q

what are the parts of the brains usually affected in convergent pathways?

A

cerebellum, thalamus, and the cerebral cortex

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15
Q

what do convergent sensory pathways do?

A

take multiple sensory input and integrate it and send it to the brain where the brain processes it resulting in a sophisticated response to a variety of stimuli

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16
Q

T or F: is the cerebellum part of the hindbrain?

A

T

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17
Q

what does the cerebellum act as?

A

a gyroscope and accomplice for motor function of the body

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18
Q

gyroscope

A

keeps you correctly oriented in your environment

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19
Q

accomplice

A

produces a smooth motor response to keep you walking in a straight line instead of zigzagging (ex)

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20
Q

what does the cerebellum do?

A

receives sensory input from multiple inputs

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21
Q

what sensory inputs does the cerebellum receive?

A
  • vestibular (balance receptors in ears, keeps you oriented)
  • visual (how are you oriented in your environment?)
  • proprioceptive (pressure, how contracted are your muscles?)
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22
Q

how does a sensory target like the cerebellum know where each of the signals is coming from and which ones to give priority to?

A

through a form of lateral inhibition! Allows the strongest/most direct signals to come through most laterally

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23
Q

what does lateral inhibition look like in sensory pathways?

A

central neuron is located at the primary source of the stimulus; terminals branch and synapse with interneurons

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24
Q

what is different about lateral inhibition in sensory pathways vs motor pathways?

A

different arrangement; the branches of the axon of the central neuron don’t synapse with the axon hillock, but they synapse with the interneuron which then synapses with the terminals of the lateral neurons

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25
Q

what occurs during lateral inhibition in sensory pathways when the interneurons synapse with the terminals of the lateral neurons?

A

the interneurons release an inhibitory NT which binds to a receptor and activates a Cl- channel

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26
Q

what occurs during lateral inhibition in sensory pathways after the Cl- channel is activated via the release and binding of an inhibitory NT from interneurons?

A

the Cl- current hyperpolarizes the terminal membrane, preventing NT release from the lateral neuron

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27
Q

lateral inhibition in sensory pathways

A

one neuron directly stimulates downstream targets and indirectly inhibits the lateral neurons

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28
Q

pre-synaptic inhibition

A

inhibition at the terminals of the lateral neuron is done by activating Cl- ion channels; Cl- current hyperpolarizes membrane (makes more negative), making it harder for an AP to depolarize terminal and release NT

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29
Q

what does lateral inhibition in sensory pathways do?

A

increases the contrast between the direct sensory field and the surround lateral sensory field

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30
Q

how does lateral inhibition work for creating a visual field?

A
  • light hits rods and cones (photoreceptors) in the retina which are excited by the electromagnetic light stimulation and fire AP
  • when a photoreceptor fires an AP, it excites bipolar cells and excites horizontal cells
  • bipolar cell excites ganglion cell
  • ganglion cell sends signal to optic nerve which goes to brain and tells visual cortex that light is coming in
  • bipolar cell also synapses with amacrine cell
  • amacrine cells inhibit lateral bipolar cells
  • horizontal cells inhibit lateral bipolar cells
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31
Q

what two things do photoreceptors do when firing an AP?

A

they excite the bipolar cell downstream, but also horizontal cells which inhibit lateral neurons

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32
Q

what is the result of lateral inhibition in vision?

A

weak periphery signal and clear/sharp center image

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33
Q

what are the 4 ways in which you can distinguish somatic and autonomic nervous systems?

A
  1. which effectors they innervate
  2. way they function in relation to their effectors
  3. anatomy/arrangement of neurons
  4. mechanism in which the NT is delivered to the effector
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34
Q

somatic vs. autonomic NS: #1 difference: which effectors they innervate

A

somatic: skeletal muscle
autonomic: smooth muscle, cardiac muscle, and glands

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35
Q

somatic vs. autonomic NS: #2 difference:
way they function in relation to their effectors

A

somatic: initiate skeletal muscle contraction (skeletal muscle will atrophy without somatic neuron supply)
autonomic: regulate rate and strength of smooth and cardiac muscle; regulate frequency and amount of glandular secretions for glands

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36
Q

autorhythmic/myogenic

A

smooth muscle, cardiac muscle, and glands

they will contract at their own intrinsic rate and strength, independent of any neural input from the autonomic system

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37
Q

somatic vs. autonomic NS: #3 difference:
anatomy/arrangement of neurons

A

somatic: one long motor neuron that goes from the spinal cord to the skeletal muscle; long heavily myelinated axon
autonomic: two neurons; first from spinal cord to second neuron then to effector; synapse occurs outside the CNS; no second neuron for adrenal glands

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38
Q

somatic vs. autonomic NS: #4 difference: mechanism in which the NT is delivered to the effector

A

somatic: well-defined NMJ; delivery of NT is concentrated and precise (like a bullseye shot)
autonomic: no well-defined NMJ; nerve terminals wander around the effector and have swellings called varicosities (instead of terminal buttons) that release NT in a diffuse way (wide angle shot into glass)

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39
Q

what is a ganglion?

A

a cell body or group of cell bodies outside of the CNS

40
Q

what is the first neuron called in the autonomic NS?

A

pre-ganglionic neuron

41
Q

what is the second neuron called in the autonomic NS?

A

post-ganglionic neuron

42
Q

why is there not a second neuron for adrenal glands?

A

the inside/central core of the adrenal gland (adrenal medulla) is a set of neurosecretory cells that used to be post-ganglionic neurons and have evolved to be more like glandular/endocrine cells rather than neurons; therefore, they are only innervated by the pre-ganglionic neuron

43
Q

neurosecretory cells

A

neurons that have lost their ability to do APs and instead of secreting a NT, they become more like glandular cells and secrete hormones directly into the bloodstream

44
Q

varicosities

A

neurons of the autonomic NS; contain synaptic vesicles that contain the NT; release NT in a diffuse mechanism when the neuron is stimulated

45
Q

somatic vs autonomic NT delivery difference

A

autonomic = slower response by the effector because of the varicosities that release NT in a broad, diffuse mechanism

46
Q

what are the three main differences between the sympathetic and parasympathetic NS?

A
  1. points of origin in the CNS
  2. locations of ganglia, ganglionic fiber lengths, post-ganglionic branching
  3. NTs they use and the receptors that are on the surface of the effectors
47
Q

sympathetic vs. parasympathetic NS: #1 difference: points of origin in the CNS

A

sympathetic: 1st thoracic through the 3rd lumbar vertebrate
parasympathetic: 3, 7, 9, 10 cranial nerves and 2, 3, 4 sacral vertebrate

48
Q

what is the sympathetic NS also known as? why?

A

thoracolumbar system; because of it’s points of origin

49
Q

what is the parasympathetic NS also known as? why?

A

craniosacral system; because of its points of origin

50
Q

sympathetic vs. parasympathetic NS: #2 difference: locations of the ganglia, ganglionic fiber lengths, post-ganglionic branching

A

sympathetic: short pre-ganglionic fiber, long post-ganglionic fiber
parasympathetic: long pre-ganglionic fiber, short post-ganglionic fiber

51
Q

sympathetic NS short pre-ganglionic fiber

A

only exits the spinal cord and travels a short way before it synapses with a series of ganglia that parallel the spinal cord called the sympathetic chain

52
Q

sympathetic NS long post-ganglionic fiber

A

has a lot of branching going on; travels from sympathetic chain to the effector

53
Q

parasympathetic NS long pre-ganglionic fiber

A

goes to the surface of the effector; the synapse with the post-ganglionic fiber occurs on the surface of the effector

54
Q

parasympathetic NS short post-ganglionic fiber

A

very little branching

55
Q

myelination in sympathetic and parasympathetic ganglions

A

pre-ganglionic neurons: much less myelinated
post-ganglionic neurons: unmyelinated (type C fibers, naked axons)

56
Q

sympathetic vs. parasympathetic NS: #3 difference: NTs they use and the receptors that are on the surface of the effector

A

sympathetic: pre-ganglionic fibers secrete ACh, post-ganglionic fiber secretes norepinephrine and epinephrine
parasympathetic: pre-ganglionic fibers secrete ACh, post-ganglionic fibers secrete ACh

57
Q

what do sympathetic post-ganglionic neurons have on them?

A

nicotinic receptors (N isoform)

58
Q

what is the primary NT of sympathetic post-ganglionic neurons?

A

norepinephrine

59
Q

what did norepinephrine used to be called?

A

noradrenaline

60
Q

what did epinephrine used to be called?

A

adrenaline

61
Q

what receptors are on the surface of sympathetic NS effectors?

A

alpha and beta receptors

62
Q

excitatory alpha and beta receptors (numbers)

A

alpha 1 and beta 1

63
Q

inhibitory alpha and beta receptors (numbers)

A

alpha 2 and beta 2

64
Q

what are sympathetic receptors known as? why?

A

adrenergic receptors; they respond to norepinephrine and epinephrine

65
Q

what is sympathetic stimulation known as?

A

adrenergic stimulation

66
Q

what do the dendrites and soma of parasympathetic post-ganglionic fibers have on them?

A

nicotinic receptors (N isoform)

67
Q

what receptor is on the surface of parasympathetic effectors?

A

muscarinic receptors

68
Q

what is the parasympathetic system known as? why?

A

cholinergic system; exclusively uses ACh as its NT (has cholinergic receptors that respond to ACh aka muscarinic and nicotinic receptors)

69
Q

what is parasympathetic stimulation known as?

A

cholinergic stimulation; inhibitory or excitatory depending on which muscarinic receptor is found on the effector

70
Q

the sympathetic and parasympathetic NS are ___________ of each other

A

antagonists; they have the opposite effect on their target organisms

71
Q

sympathetic vs parasympathetic: inactivation of NT at synapse

A

sympathetic: transmitter receptor complex is engulfed/taken up on the surface and the NT is taken back up in varicosities
parasympathetic: recycles components of ACh

72
Q

function of sympathetic and parasympathetic NS: heart

A

SNS: excitatory (strength and speed); accelerates heart beat, gives ventricles stronger contraction

PSNS: inhibitory; slows down heart

73
Q

function of sympathetic and parasympathetic NS: GI system

A

OPPOSING EFFECTS ARE UNEQUAL

SNS: inhibitory; little to no effect

PSNS: excitatory; simulates gastric juices, digestion, GI smooth muscle, etc.; Vagus nerve has most control over GI system (specifically GI smooth muscle)

74
Q

function of sympathetic and parasympathetic NS: lungs

A

SNS: excitatory; dilates airways by relaxing smooth muscles (basis for why people with Asthma use epi to open up lungs)

PSNS: inhibitory; constricts smooth muscle that surrounds airways/bronchioles, making it harder to breath

75
Q

what do excitatory or inhibitory effects in the autonomic NS depend on?

A

the distribution of receptors

76
Q

SNS vs PSNS: receptors on the heart

A

SNS: stimulates mainly by beta 1 receptors on ventricles

PSNS: inhibits by M2 muscarinic inhibitory receptors

77
Q

SNS vs PSNS: receptors on vascular smooth muscle

A

SNS: stimulated primarily by alpha 1 receptors (maintains vascular tone)

PSNS: almost no effect of the PSNS

78
Q

what receptors are the dominant receptors in most major blood vessels and major arteries (except skeletal muscle)?

A

alpha 1

79
Q

what receptors are in abundance on skeletal muscle?

A

blood vessels that go to skeletal muscle have an abundance of beta 2 receptors (inhibitory); when stimulated they relax the blood vessels and allow more blood flow to skeletal muscle

80
Q

SNS vs PSNS: receptors on smooth muscle in GI tract

A

SNS: little to no effect (alpha 1, alpha 2, beta 2 receptors)

PSNS: muscarinic 3 receptors; increases motility of smooth muscle and aids with digestion

81
Q

SNS vs PSNS: receptors on bronchioles

A

SNS: excites beta 2 receptors in smooth muscle that surround the bronchioles; dilates, making it easier to breathe

PSNS: action on M3 muscarinic receptors; tightens down/constricts smooth muscle surrounding bronchioles

82
Q

Mass discharge

A

a result of specific adaptations of the SNS that allows it to fire as a coordinated unit

83
Q

what does the complete firing of all units of the SNS prime the body for?

A

periods of intense bursts of speed, strength, and endurance

84
Q

what are the three features/adaptations of the SNS that allow mass discharge?

A
  1. organization
  2. very highly divergent system
  3. stimulates adrenal medulla
85
Q

first feature/adaptation of the SNS: organization

A
  • has control centers in the brain (specifically medulla oblongata) and spinal cord
  • all the neurons that go along the spinal cord act as a master switch of the SNS
86
Q

what causes massive stimulation to all the effectors in the SNS during mass discharge?

A

intense, potentially life-threatening stimuli (rage, fear, anger, extreme cold, blood loss, extreme pain)

87
Q

what are the intense, potentially life-threatening stimuli in the SNS during mass discharge received by?

A

hypothalamus (part of midbrain); control center for all of these strong emotions

88
Q

where does the hypothalamus send the intense, life-threatening stimuli signals during mass discharge in the SNS?

A

sends signals to medulla and spinal cord; that is what lights up the SNS

89
Q

second feature/adaptation of the SNS: highly divergent system

A

as the control center fires and recruits more neurons, it hits the sympathetic chain and branches even further resulting in a huge amplification of neural signals in the SNS which gives a very strong final signal to all the effectors

90
Q

divergence

A

property of motor pathways that is used to amplify neural signals and the strength of neural signals

91
Q

third feature/adaptation of the SNS: stimulates the adrenal medulla

A

the SNS stimulates the adrenal medulla, then these modified post-ganglionic neurons that are now endocrine glands excrete epinephrine and norepinephrine into the blood at a ratio of 80:20

92
Q

how does the SNS stimulating the adrenal medulla contribute to mass discharge?

A

effector organs get hit two ways:
1. direct stimulation by sympathetic neurons (stimulated neurally)
2. stimulated by circulating epinephrine and norepinephrine which primes the body

93
Q

what are the 3 main physiological effects/results of mass discharge?

A
  1. increased HR and strength of contraction
  2. increased BP
  3. increased blood glucose
94
Q

physiological result of mass discharge #1: increased HR and strength of contraction

A

epi/norepi affects the beta 1 receptors on the ventricles; ventricles pump blood harder and faster

95
Q

physiological result of mass discharge #2: increased BP

A

result of peripheral vasoconstriction (and partly increased HR)

alpha 1 receptors on arteries that lead to peripheral parts of body: clamp down on smooth muscle and arteries, shutting off blood flow to peripheral parts of body…. this begins to redistribute blood flow —> decreased blood flow to peripheral parts of body and increased blood flow to skeletal muscle

beta 2 receptors on blood vessels that feed skeletal muscles: activated by epi/norepi; blood vessels dilate resulting in more blood flow to skeletal muscle (primes muscle by delivering O2 and glucose)

96
Q

physiological result of mass discharge #3: increased blood glucose

A
  1. norepinephrine primarily on the liver mobilizes stored glycogen into glucose
  2. glucose = dumped into bloodstream and circulates to the muscles, priming the muscles for work

you’re splitting a lot of ATP during mass discharge (chemical to mechanical work), so your body heats up!
this causes your cooling mechanisms to increase via sweating and panting

Biomed Phys (7 decks)

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