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Block 3 Up To Quiz 1 > Reflexes > Flashcards

Reflexes Flashcards

1
Q

Reflex

A

simple relatively stereotyped action elicited by a sensory stimulus

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2
Q

Reflex arc

A

the neural pathway that underlies a reflex

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3
Q

somatic reflex examples

A

stretch, golgi tendon, withdrawal, crossed extensor

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4
Q

autonomic reflex examples

A

respiration, temperature, blood pressure

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5
Q

Sherrington suggested that complex behavior could be explained as a result of

A

chaining different reflexes together

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6
Q

5 components generally found in reflex arc

A
  • a sensor to detect stimuli
  • an afferent pathway
  • an integrative center
  • an efferent pathway
  • an effector
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7
Q

reflexes mediated by

A

neurons in nervous system

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8
Q

monosynaptic reflex

A

involves only a single sensory neuron and a motoneuron (one synapse between two neurons hence monosynaptic)

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9
Q

stretch reflex neurotransmitters

A

excitatory sensory NT: glutamate

excitatory motor NT: acetylcholine

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10
Q

effect of stretch reflex

A

once muscle stretched muscle fiber = contracted to help maintain standard stretch of that muscle; stretch reflex is for proprioception it lets you maintain posture

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11
Q

all skeletal muscle innervation is

A

excitatory

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12
Q

stretch reflex signs of afferent and efferents

A

stretch in muscle detected spindle afferent (which detects stretch) produces action potential that will terminate on motor neuron in spinal cord
spindle afferent- if activation of spindle neuron depolarizes motor neuron it has excitatory effect on motor neuron
spindle efferent- motor neuron activated by afferent synapsing on it (all skeletal muscle innervation is excitatory) -> muscle excitation -> contraction

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13
Q

inhibitory reflex arc to inhibit flexor

A

spindle afferent excitatory synapse -> inhibitory interneuron activated -> inhibitory effect on flexor motor neuron (because motor neuron synapse on muscle excitatory interneuron works by preventing firing of motor neuron)

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14
Q

interneuron can have

A

excitatory or inhibitory effects on post-synaptic cells they contact

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15
Q

withdrawal reflex (arm as example) signs

A

one reflex arc to excite flexor (bicep)
nociceptive afferent -> excitatory synapse on interneuron -> interneuron excitatory synapse on flexor motor neuron -> contraction of flexors

one reflex arc to inhibit extensor (triceps)
nociceptive afferent -> excitatory synapse on inhibitory interneuron -> inhibitory synapse interneuron on extensor motor neuron -> inhibit excitatory synapse on motor neuron

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16
Q

baroreceptor reflex function

A

helps to maintain blood pressure (homeostasis)

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17
Q

homeostasis

A

aims to provide cells in body with constant environment (O2, pH, blood supply, glucose, temperature, other critical parameters, blood pressure)

  • maintains consistancy
  • negative feedback loops’
  • redundancy
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18
Q

baroreceptor reflex sensory

A

baroreceptor: Mechanosensitive channel on aortic and carotid arches:
Baroreceptors are modified stretch receptor these are located in carotid artery and aortic arch (carotid sinus and aortic arch bot distend under pressure) bc walls of vessels stretch in response to vasodilation
- baroreceptors are myelinated sensory nerve fibers which have specialized endings which detect changes in degree of stretch

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19
Q

baroreceptor composed of

A

subunits called degenerins which are sensitive to stretch because connect to both cytoskeleton and exterior surface via variety of adaptor protiens, these function to connect inside of cell to outside with a channel between
- the 2 sides of channel get pulled apart by pressure and lets ions through

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20
Q

sympathetic and parasympathetic systems

A

always active and always on

- basal rate= tone which allows for regulation in either up or down direction

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21
Q

baroreceptor reflex afferents

A
  • afferents from aortic arch project via vagus nerve
  • afferents from carotid sinus project via glossopharyngeal nerve
  • both go to medulla?
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22
Q

baroreceptor reflex integration center

A

information from barrorreceptors is received by nucleus of solitary tract (nucleus tracts solitarius ie NTS) located in the medulla
- NTS integrate signals from sensory afferents, input from higher cortical areas and thalamic regions to generate an output

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23
Q

baroreceptor afferents are generally

A

glutamatergic

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24
Q

receptors we know are present in NTS

A

AMPA and NMDA don’t know too much else

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25
Q

autonomic regulation involves modulating

A

the basal rate of continuously active parasympathetic and sympathetic systems known as tone

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26
Q

if blood pressure is up we want to

A

lower it so want to reduce blood flow so inhibit blood flow by increasing parasympathetic signals to heart and blood vessels and decrease sympathetic signals to heart and blood vessels

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27
Q

how does baroreceptor reflex modulate ANS tone

A

NTS integrates info from baroreceptors output -> medullary nuclei:

excitatory output -> CVLM -> inhibitory neurons in CVLM -> RVLM -> controls sympathetic vascular tone and heart rate

NTS also projects to -> NA and DMNX -> control parasympathetic outflow to heart

28
Q

CVLM
RVLM
NA
DMNX

A

Caudal ventrolateral medulla
Rostral ventrolateral medulla
Nucleus ambiguous
Dorsal motor nucleus aka parasympathetic nucleus of CN X

29
Q

baroreceptor efferents

A

sympathetic and parasympathetic branches of nervous system

30
Q

baroreceptor effetors/ outpts

A

change in sympathetic and parasympathetic outflow purpose of reflex is to maintain homeostasis

31
Q

what happens when there is rapid rise in arterial pressure

A
  • carotid and aortic vessel walls stretch -> activate baroreceptors -> excitatory stimulation neurons in NTS -> excite inhibitory internueons in CVLM -> inhibit vasomotor neurons in RVLM and inhibit sympathetic outflow to heart from RVLM -> vasodilation and reduction in heart rate
    also:
  • carotid and aortic vessel walls stretch -> activate baroreceptors -> excitatory stimulation neurons in NTS -> excitatory connections to NA and DMNX -> promotion parasympathetic outflow to heart -> bradycardia and vasodilation -> drop in arterial pressure
32
Q

RVLM

A

unless inhibited by NTS neurons neurons in RVLM produce tonic output that promotes vasoconstriction (symp tone)
- inihibiting RVLM promotes vasodilation

33
Q

NA and DMNX affect

A

these areas are cardioinhibitory excitation of these areas promotes parasympathetic outflow to heart resulting bradycardia and vasodilation leads to drop in arterial pressure

34
Q

baroreceptors ideal should be able to sense

A

stretch and also quality of that stretch to integrating center

35
Q

strong stimulus evokes

A

stronger reflexive response

36
Q

how does baroreceptor reflex produce quantitative stretch information

A
  • firing rate of baroreceptor neuron changes exponentially with small increase or decrease in pressure within given range pressure differences; small change in pressure can cause baroreceptor to fire more frequently or less frequently
  • baroreceptors tuned to monitor small changes away from given set point (maintain arterial pressure v close to given setpoint)
37
Q

small increase in arterial pressure

A

results in dramatically increase baroreceptor firing leading eventually to drop in pressure by increased parasympathetic outflow and decreased sympathetic outflow which in turn -> lowering firing frequency of baroreceptor to match drop in pressure

38
Q

small decrease in arterial pressure

A

baroreceptor fires are dramatically lower rate producing associated increase in sympathetic outflow to boost pressure

39
Q

sympathetic affect on blood pressure

A

increases blood pressure

40
Q

parasympathetic affect on blood pressure

A

decreases blood pressure

41
Q

baroreceptor reflex during exercise

A

activation of baroreceptor reflex will occur at higher arterial pressure because baroreceptor reflex is reset to be activated at different pressure

42
Q

baroreceptor reset get input from

A
  • central command

- presser reflex

43
Q

baroreceptor reflex setpoint change

A
  • occurs at level or baroreceptor itself as well as at level of integrating center in medulla
  • NTS receives input from higher cortical areas including hypothalamus so central command from other areas of brain can modulate input to NTS and its subsequent output -> rapid alterations in effectiveness and range of reflex this is why brain can modulate and modify reflexes
44
Q

startle reflex

A

leads to higher heart rate and blood pressure bc brain anticipates need to appropriate action and raises tone of symp nervous system and resets in process baroreceptor reflex

45
Q

recelfex response due to

A

sensory activation but also in case of baroreceptor modified by feedback form muscles
- feedback and feedforward mechanisms operate to control and modify baroreceptor reflex

46
Q

baroreceptor reflex in diseased animals

A
  • baroreceptor reflex can adapt to long-term changes in physiology of animal
  • in hypertensive patients baroreceptor reflex setpoint shifted right reflecting higher, longterm blood pressure in these animals (reflecting baroreceptor role in regulating short-term, moment to moment changes)
  • baroreceptor response also flattens so it is not as sensitive and need greater differences in pressure to trigger the reflex
  • exercise can imporve sensitivty of reflex in hypertensive patient showing impact of physiology on reflex
47
Q

crossed extensor response

A

in leg that steps on noxious stimuli
excitatory interneuron activated -> flexor contraction
inhibitory interneuron activated -> inhibition extensor
Opposite leg
extensor excited and flexor inhibited by interneurons crossing midline off body

48
Q

locomotion decrebreate animals

A

animals can walk when placed on treadmill (these animals are not getting forebrain input for locomotion)
if treadmill increases in speed animal can adjust from walk to trot to gallop ect.
- this indicates that complex behavior such as locomotion can be explained by series of reflexes interconnected with one another

49
Q

decerebrate animals

A

transection in mid-brain separating input from cortex to the limbs

50
Q

how are rhythmic motor behaviors observed or produced in absence of sensory stimuli

A

in part these are controlled by central pattern generators

51
Q

examples of rhythmic motor behavior

A
  • walking
  • running
  • swimming
  • respiration
  • vomitting
  • shivering
52
Q

goal of each CPG

A

generate rhythmic pattern of firing that -> motor response

53
Q

CPGs for locomotion

A

located in spinal cord not within brain; there is at least one for each limb; locomotory CPGs interconnected with one antoher

54
Q

how does CPG function 2 theoretic ways

A
  1. Pacemaker neurons can drive interneuron that drives motor output
  2. interneurons reciprocally inhibit one another
55
Q

pacemaker neurons driving interneurons that drive motor output

A

pacemaker neuron (one that oscillates its firing patterns) could drive interneuron that drives motor output; motor circuitry would not be activated without pacemaker activation

56
Q

interneurons reciprocally inhibit one another

A
  • excitatory interneuron activates contraction of extensor motoneuron also excites inhibitory interneuron
  • activation inhibitory interneuron inhibitors excitatory interneuron that activates flexor motor neuron preventing flexor contraction
  • must have way to release excitatory interneuron controlling flexor from inhibition (do with wide variety of mechanisms)
57
Q

excitatory interneuron controlling flexor released from inhibition

A

it excites flexor motoneuron and excited inhibitory interneuron which inhibits excitatory interneuron that activates extensor resulting in opposite response (flexor activation and extensor inhibition_
- eventually the excitatory interneuron will escape inhibition and cycle will repeat

58
Q

CPGs can be

A
  • triggered (locomotion) or constitutive (respiration)

- their functions can be modified (can hold breath, can stop walking to avoid obstacle)

59
Q

CPG function affected by both

A

sensory input and central command

60
Q

respiratory CPG sensory inputs

A
  • sensors that measure partial pressure of oxygen in blood
  • sensors that measure partial pressure of Co2 (plays greater role than partial pressure O2 sensors)
  • mechanosensors in lung, nose, gut, heart, elsewhere
  • firing can also be affected by central command
61
Q

central command CPG respiratory

A
  • hypothalamus (during pain)

- cortex (when you want to sing ect.)

62
Q

output of CPG respiratory

A

to appropriate muscle groups, also interacts with other CPGs like those for V+ and swallowing

63
Q

locomotion CPGs involves what sensory inputs

A

vision proprioception ect.

64
Q

CPGs have large number of

A

modulatory inputs

65
Q

oscillating rhythmic behavior can be accomplished in absence of

A

sensory stimuli but integration of sensory stimuli and cortical control with motor circuits of CPG are necessary for normal rhythmic activity

66
Q

what demonstrates complexity that can underlie control of spinal reflexes

A

existence of CPGs and integration of external information by cortex

Block 3 Up To Quiz 1 (24 decks)

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