Last weekly Test Flashcards
(99 cards)
1
Q
Aa fiber
A
Fast conduction
100 m/s
2
Q
Aa nerve fiber innervates…
A
Extrafusal fibers
(multiple muscle fibers)
3
Q
Motor Unit
A
A single motor neuron plus all the muscle fibers it innervates
4
Q
Ocular muscle fibers per neuron
A
3-4 fibers / motor neuron
5
Q
Hand muscle fibers per neuron
A
~ 10 fibers / motor neuron
6
Q
Back muscle fibers
A
~ 3000 fibers / motor neuron
7
Q
Motor Neuron pool
A
Summary of all the motor neurons that innervate 1 muscle
8
Q
Type I muscle fibers
A
- Red
- High oxidative capacity
- Maximal force developed SLOW
- Fatigue-resistant
9
Q
Type IIa muscle fibers
A
- Red/White intermediate
- Fatigue-resistant but FASTER than Type I
- Oxidative
10
Q
Type IIb muscle fibers
A
- White
- Glycolytic fiber
- Maximal force reached QUICK
- Quickly fatigued
11
Q
How to increase contraction force
A
- Increasing AP frequency
- Recruitment of skeletal muscle fibers
- Size-principal used
12
Q
Contraction Size-principal
A
First small motor units recruited, then larger & larger ones so force is increased in smaller steps cause smaller units are more easily excited
- Small motor units: Slow twitch fibers (I)
- Large motor units: Fast twitch fibers (II)
13
Q
Fractionation
A
Alternating contraction & relaxation of motor units during the contraction of a muscle
14
Q
Localization of spinal motor neurons
A
Anterior horn
- Lateral: Manipulation
- Medial: Posture
- Anterior: Extensor
- Dorsal: Flexor
15
Q
Monosynaptic central delay
A
0.5 - 0.8 ms
16
Q
Bisynaptic central delay
A
1 - 1.6 ms
17
Q
Polysynaptic central delay
A
~ 2 ms
18
Q
Proprioceptive reflex arc receptor
A
Receptor is found inside effector organ (e.g muscle fiber)
19
Q
Exteroceptive reflex arc receptor
A
Receptors usually nociceptive
20
Q
Vegetative reflex arc receptor
A
Receptors usually found in visceral organs
21
Q
Proprioceptive sensory fibers
A
Aa
- Ia: from muscle spindle fibers
- Ib: from golgi tendon organs
80 - 120 m/s
22
Q
Skin Mechanoceptors sensory fibers
A
AB
II
35 - 75 m/s
23
Q
Pain & Temp sensory fibers
A
Aδ
III
5 - 30 m/s
24
Q
Pain / Temp / Itch sensory fibers
A
C
IV
0.5 - 2.5 ms
25
Muscle spindle length
10 mm
26
What determines precision of muscle
Number of muscle spindles in a muscle
27
Muscle spindle function
Sensory organ in the muscle to Monitor the lengthening of muscle fibers
28
Muscle spindle structure
- Surrounded by CT capsule
- 2x Nuclear bag fibers
- 5-8x nuclear chain fibers
29
Nuclear bag receptor
- Dynamic receptor
- 1 primary annulospiral nerve ending (Ia)
30
Nuclear chain receptor
- Static receptor
- 1 Primary (Ia) & 1 Secondary (II) annulospiral nerve ending
- Innervate peripheral parts of receptor with contractile feature
- Reports absolute length of muscle fiber
31
What nerve fibers innervate efferent part of receptor?
Ay fibers from y-motor neurons
32
What innervates intra & extrafusal muscle fibers
- Intrafusal: Ay
- Extrafusal: Aa
33
Golgi tendon organ size
1 mm
34
Frequency of GTO vs Muscle spindles
1/5 of the frequency
(so less)
35
Golgi tendon organ summ.
- Serially coupled to collagen fibers
- Activated when tendon (collagen) stretches
- No contraction = No AP
36
Golgi tendon organ fiber type
Ib fiber
(thinner than Ia but still fast)
37
Myotactic (stretch) reflex
- Monosynaptic
- Proprioceptive
- Fast 0.5 - 0.8 m/s
- Segmental (1 s.c segment)
- Reciprocal inn of antagonist by Ia inhib. interneuron
(e.g patellar)
38
Inverse Myotactic (stretch) reflex
- Bisynaptic
- Triggered by GTO stim.
- Proprioceptive
- Segmental
- Fast (Ib)
- Causes muscle contraction when it is under too much tension using Ib inhib. interneuron
39
Exteroceptive reflex
- Flexor-withdrawal reflex
- Usually free nerve endings on body surface
- Nociceptive (Aδ / C)
- Polysynaptic
40
Crossed flexor-extensor reflex
If nociceptive stimulus is painful enough, we get an opposite action in the other limb to stabilize
41
Intersegmental Reflex
If stimulation is higher/very painful more and more spinal segments are activated creating a dominant reflex that overrides others
42
Spinal shock / Spinalization
Loss of muscle tone and spinal reflexes after SC injury, so no motor or sensory or autonomic sensation
43
Recovery after Spinalization
1) Flexor-reflex
2) Stretch reflex
3) Autonomic reflexes
4) Positive/Negative support reflexes
5) Fictive locomotion (e.g. walking)
44
Positive / Negative supporting reflex
Activation of anti-gravity muscles
45
Fictive locomotion
Rhythmic flexor & extensor contraction in movements like walking
46
Bablinski reflex
Stroking the sole of the foot causes toes to fan out
(in adults they curl)
47
Interneuron frequency
30x higher number than Motor neurons
48
Ia inhibitory Interneuron
- Reciprocal innervation
- Inhibits antagonistic muscles
(CNS can inhibit them)
49
Ib inhibitory interneuron
- Inverse myotactic reflex
- Golgi tendon organ reflex
50
Renshaw Cells
Modulate strength & firing rate of a-motor neurons
51
Pathways for conscious and unconscious movements
- Conscious = Lateral pathways
- Unconscious = Medial pathways
52
Tracts in Lateral Pathways
- Corticospinal tract (90%)
- Rubrospinal tract
- Lateral corticobulbar tract
53
Lateral Corticospinal Tract
1) Primary Motor Cortex
2) Passes Internal capsule
3) Crosses pyramidal decussation
4) Terminates directly on a-motor neurons
54
Rubrospinal Tract
- From Red Nucleus
- Innervates some large arm muscles
- Involved in flexor reflexes of upper limb
55
Lateral Corticobulbar pathway
- Innervates lower face & tongue
- Responsible for speech
56
Tracts in Medial pathway
- Medial corticospinal tract
- Anterior corticobulbar tract
- Vestibulospinal tract
- Pontine reticulospinal tract
- Medullary reticulospinal tract
- Tectospinal pathways
57
Medial Corticospinal tract
1) Primary Motor cortex
2) Passes Internal capsule (post. limb)
3) NO CROSS at pyramidal decussation
4) Innervated medial muscles (bilaterally)
58
Vestibulospinal tract origin
Semicircular & Visual organs
(mostly excitatory)
59
Pontine reticulospinal tract origin
Reticular formation of Pons
(mostly excitatory)
60
Medullary retuculospinal tract origin
Reticular formation of Medulla
(mostly inhibitory)
61
Tectospinal pathways
- From tectal area sup. colliculus to SC
- Visual & Sound stimuli
62
Realization & execution of movement steps
1) Association areas (ppa): 800ms before
2) Supplementary motor area: 500ms before
3) Premotor area: 5ms prior
4) Primary motor cortex: 0ms
63
What brain areas control what pathways
- Primary motor cortex = Lateral pathways (conscious)
- Premotor area = Medial pathways (unconscious)
64
Postural reflexes
- Tonic Neck reflex
- Eye movements
- Righting reflex
65
Basal Ganglia main components
- Striatum (putamen & caudate)
- Pallidum (int & ext globus palidus)
- Subthalamic nuclei
- Substantia nigra
66
Cortico-Cortical loop
1) Cortex
2) Basal ganglia
3) Thalamus
5) Back to Cortex
67
Basal ganglia pathways
- Direct: excitatory loop for movement
- Indirect: inhibitory loop to suppress movements
68
Major Dopamine producer
Substantia nigra
(pars compacta)
69
Dopamine receptors
- D1: Gs, Excitatory effect
- D2: Gi, Inhibitory effect
(always positive effect on movement)
70
Cerebellum main functions
- Regulates movement
- Maintains postural background
- Control of small movements
- Regulation of autonomic movement
- Ensures fluid/smooth movements
71
Cerebellar functional Divisions
- Vestibulocerebellum (archi-)
- Spinocerebellum (palleo-)
- Cerebrocerebellum
72
Vestibulocerebellum
(archicerebellum)
- Input from Vestibular system & relay nuclei of visual
- Output posture & eye movements
- Equilibrium, balance, eye movement reg.
73
Spinocerebellum
(palleocerebellum)
- Input motor cortex & spinal cord
- Output Red nucleus or motor cortical areas (via thalamus)
- To correct movements
74
Cerebrocerebellum
- Input motor cortical areas
- Output pre-programmed automatic movements
- For learning certain skills
75
Cerebellum Neural connections
- Mossy fibers & Climbing fibers
- Modulate activity of Purkinje cells & deep cerebellar nuclei
76
Cerebellar damage symptoms
Similar to being drunk, ethanol influences cerebellar function
77
What can take over cerebellum in case of Chronic damage?
Neocortex over time
78
Core temperature
37°C
79
Skin temperature
28 - 36°C
80
Range where core temp can stay constant
10 - 55°C
- Genetically determined
81
Core temp deviation toleration
+/- 0.5 °C
82
Survivable core body temp
30 - 42°C
83
Tcore too low
Below 30°C Heart is affected
- Channels function abnormally
- Heart function decreases
- Arrhythmias
84
Tcore too high
Above 42°C Brain is affected
- Brain function decrease
- Reflexes compromised
85
Comfort zone Tcore
Temp range where thermoregulation is not needed
- Naked: 27 - 30°C
- Clothed: 21 - 23°C
86
How to measure energy requirement of Thermoregulation
By O2 consumption, increases both <10°C and also >55°C
87
Organs in Non-shivering heat production
- Liver
- Brain
- Kidneys
- Heart
- Brown Adipose
88
Types of heat loss Evaporation
- Perspiration Insensibilis (skin/lung fluids) ~ 1L /day
- Perspiration Sensibilis (sweating)
89
Acral Skin
- Non-hairy skin
- Arteriovenous anastomosis
- Sympathetic adrenergic inn.
90
Non-Acral skin
- Hairy skin
- Sweat glands present
- Glands & Circulation work together
91
Sympathetic Cholinergic Regulation
Causes active vasodilation & heat loss
92
Thermoregulation Main methods
- Sympathetic Adrenergic
- Sympathetic Cholinergic
- Emotions
93
Maximal sweating
2L / hour
(hyposmotic / dilute)
94
Sweating mechanism
1) Primary secretion by acinar cells similar to plasma
2) Secondary reabsorption of ions making it hyposmotic by ductal cells & impermeabel to water (aldosterone dependent)
95
Central regulator of thermoregulation?
Hypothalamus
- Ventral: Vasodilation
- Dorsal: Vasoconstriction
- Lateral: Higher level behavior (seek shade, but on clothes, ...)
96
Central Thermoreceptors
- Hypothalamus, SC, Liver
- Changes in Core Temp.
- Most important!
97
Peripheral Thermoreceptors
- Skin
- Changes in Skin temp.
- Can signal modification of set-point value (hypothalamus)
98
Sudomotor Activity
Sweating
99
Narcosis
Decreased BMR so less chemical heat production
