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Motor control, relexes, & senses Flashcards

1
Q

Efferent Nervous System
Motor control

A

NS uses many sensory inputs to plan motor actions
Processed consciously in the cerebral cortex
Processed unconsciously in other parts of CNS
A few senses are especially important for unconscious processing

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2
Q

Somatic senses

A

Efferent senses of the body
1. Proprioception: sense of position of limbs
2. Vestibular sense: sense of balance

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3
Q

Proprioception

A

sense of position of limbs
- Muscle spindles - in skeletal muscle organs detect stretch = length of muscle
- Gogi tendon organs - in tendons right next to muscle detect tension = force on muscle

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4
Q

Vestibular sense

A

Sense of balance
- In inner ear
- Detects position and motion of head

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5
Q

Premotor Complex

A
  • Plans complex motions involving multiple muscle groups
  • Receives signals from sensory cortices + association areas
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6
Q

Primary motor complex

A
  • Directly controls somatic motor neurons
  • Has a homunculus = map of the body
  • Receives signals from premotor cortex
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7
Q

Cerebellum

A

Helps generate smooth + coordinated motions
- Compares motor complex plan to what is actually going on
- Gets signals from the motor cortex
– Somatic senses - especially proprioception + vestibular sense)
- Sends signals back to the motor cortex

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8
Q

Basal ganglia

A

Helps coordinate motor actions by receiving signals from all parts of the cortex, then sends signals back to the premotor complex.
At default, it suppresses cortex from generating motions
Most release suppression to move.

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9
Q

Giant Pyramidal Neurons

A
  • Cells bodies are in the primary motor complex
  • Axons goe down the spinal cord
  • Synapse on somatic motor neurons in the spinal cord
  • Contains Pyramidal Tracts
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10
Q

Pyramidal Tracts

A

White matter tracks that pyramidal axons travel down
Ventral
Direct = go directly from cortext to motor neurons

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11
Q

Structures of Motor Control
in the Efferent Nervous System

A
  • Premotor cortex
  • Primay motor cortex
  • Cerebellum
  • Basal Ganglia
  • Giant Pyramidal Neurons
  • Pyramidal tracks
  • Motor neurons that leave CNS & make muscles contract
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12
Q

Reflex

Definition + Types

A

= An automatic (unconscious) response to a stimuli
- Faster than conscious thought
- Conscious thought can overcome reflexes
Reflex Types:
- Autonomic
- Somatic
- Pollysynaptic
- Monosynaptic
- Short
- Long

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13
Q

Reflex Arc

A

Series of neurons that a reflex passes through
Receptor = detects the stimulus
1. Signals the Afferent neuron = carries the signal from receptor to integration center
2. Integrating center = processes information about the stimulus + makes decisions
3. An efferent neuron = carries the signal from integrating center to effector
4. Effector gets signal from efferent neuron + does something (ex: muscle contraction)

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14
Q

Autonomic Reflex

A

= efferent neurons are autonomic + effector for smooth muscle, cardiac muscle, glands or adipose

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15
Q

Somatic Reflex

A

= efferent neurons are somatic motor neurons + the effector is always skeletal muscle

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16
Q

Short Reflex

A

Initiated by the integrating center in PNS
Only autonomic or visceral

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17
Q

Long Reflex

A

Integrating center in CNS
- Autonomic or somatic
- Somatic have to be long because the cell bodies are in the CNS

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18
Q

Monosynaptic Reflex

A

= reflex with only 1 synapse
- Afferent neuron synapses directly on an efferent neuron
- The integration center is synapse + decision by efferent neuron to have AP

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19
Q

Polysynaptic Reflex

A

= reflex with more than 1 synapse, have at least 1 interneuron between the afferent + efferent neuron - that creates multiple synapses

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20
Q

What reflexes do the brain stem control?

A

Complex somatic reflexes:
- Breathing
- Maintaining balance + posture
- Responding to visual + auditory stimuli
- All polysynaptic

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21
Q

Indirect pathways

A

= white matter tracts in the spinal cord
- Neurons with cell bodies in the brain stem
- Axons travel down the spinal cord in indirect pathways
- Neurons synapse on interneurons in the grey matter of the spinal cord
- Interneurons synapse on somatic motor neurons

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22
Q

Spinal Reflexes

Definition + Types

A
  • Somatic reflexed
  • Integration center in the spinal cord
  • Monosynaptic or polysynaptic
  • Synapses in the gray matter of the spinal cord
    Types of spinal reflexes:
  • Stretch reflex
  • Tendon reflex
  • Flexor reflex
  • Crossed-extensor reflex
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23
Q

Stretch reflex

A

When muscle is stretched, it contracts in response (as a reflex)
Initiate the reflex by hitting a tendon:
1. Muscle spindle in muscle detects stretch
2. Sends signal to spinal cord on an afferent motor neuron
3. In spinal cord afferent neurons synapse on the monosynaptic motor neuron for the same muscle
4. Efferent motor neuron carries signals to muscle that was stretched + signals the muscle
5. Muscle contracts

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24
Q

Reciprocal Inhibition

A

The antagonist to the stretch reflex that makes the other muscles relax for the flex to occur.
Polly synaptic
Afferent neuron synapses on an interneuron
The interneuron inhibits the motor neuron + on the antagonistic muscle

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25
Tendon Reflex
When the body detects increased tension on muscle and makes the muscle relax - So muscles don't have too much force (they’ll damage) - Golgi tendon organ detects tension - Polysynaptic Spinal reflex - Reciprocal activation occurs at the same time ## Footnote ex: patellar test
26
Reciprocal Activation
Make the antagonists contract during a tendon reflex.
27
Flexor Reflex
= withdrawal reflex Limb pulls away from painful stimulus Can consciously overcome Nociceptors detect pain → send signal to the spinal cord → Flexors in the limb contract + makes the extensors in the limb relax → makes you pull the limb away
28
Crossed-extensor reflex
Similar to a flexor reflex but you're prevening falling over when you withdraw the other leg. This only occurs in the legs. Have flexor reflex in one leg - opposite leg has extensor reflex: extensions contract + flexors relax
29
What autonomic reflexes does the brain stem control?
- Cardiovascular center - Respiratory centers Neurons in the brain stem synapse on presynaptic neurons in the brain stem + spinal cord
30
Sensory receptor
cell that responds to a stimulus + turns it into a signal in the nervous system
31
Afferent neuron types
- with free nerve endings - with accessory structures
32
Specialized receptor cell
Cell that detects stimulus but isn’t a neuron Membrane depolarizes No AP, just graded potential Signals a neuron with neurotransmitter Sight, hearing, balance, taste, 1 touch receptor
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Neuron with free nerve ending
Dendrites that detect stimulus and don’t have anything around them ex: Temperature, pain, smell
34
Neuron with accessory structures
Tissues are around dendrites that aid in the detection of stimulus ex: Mostly touch + proprioception
35
Special Senses
Senses with their own specialized organ: Smell, sight, hearing, balance, taste - Have specialized receptor cells *(except smell)* - Afferent neurons are bipolar *(except taste)* - Travel to the brain on special cranial nerves *(except taste)* - Each one had their own dedicated sensory area of the cortex ## Footnote Only senses with bipolar neurons Everything else is pseudounipolar
36
Somatic Senses
Senses of the skin, muscles, and joints: Temperature, pain, proprioception, touch - Receptors are afferent neurons (except 1 touch receptor) - Afferent neurons are pseudounipolar, cell bodies are in the dorsal root ganglion - Travel on all spinal nerves + most cranial nerves - Perceived all in the somatic sensory cortex
37
Visceral Senses
Senses of internal organs + fluids in the body: pH or O2 or CO2 in blood, illness, fullness, visceral pain (not totally consciously aware) -Afferent neurons are pseudounipolar - Enter the CNS on spinal nerves: glossopharyngeal (IX), vegas nerve (X)
38
Chemoreceptors
Detect chemicals in and out of the body Smell, taste, CO2 or O2 in blood, sugar in blood, what’s in the digestive tract Almost all have protein receptors in the plasma membrane
39
Mechanoreceptors
Detect physical pressure Mechanically gated ion channels open when there is pressure on the cell Touch, proprioception, hearing, balance, blood pressure
40
Thermoreceptors
Respond to temperature Have specialized ion channels that open up at certain temperatures Different channels open at different temperatures Responds to chemicals (spicy) In skin, muscle, viscera, hypothalamus
41
Photoreceptors
Respond to light Only in the retina of the eye
42
Sensory Transduction
How a neuron turns a signal from a stimulus to a signal in the nervous system.
43
Receptor potential
Membrane potential in a sensory receptor - Stimulus changes the receptor potential - Change in potential proportional to the strength of stimulus - Ion channels open + close in response to stimulus (except salt)
44
Receptive field
Place where receptor detects stimulus Each receptor has its own field: Touch receptor - location on skin Photoreceptor in eye - light that reaches certain part of the retina Nervous system knows where stimulus comes from by which receptor was activated Size vs precision of receptive field Large receptive field needs fewer receptors - less precise Small receptive field needs more receptors - more percise
45
Sensory Modality
A type of stimuli you detect Light, sound, pressure on skin, smell
46
Sensory quality
Differences between what we perceive in stimuli of same modality: Light → color Sounds → tone Smell → different smells Touch → light vs deep Temperature → hot vs. cold Different receptors detect stimuli of different modalities + qualities Nervous system knows what type of stimulus based on which receptor is detected
47
What are the 2 ways receptors can encode the size of stimulus?
1. Bigger stimulus → higher AP frequency 2. Bigger stimulus → activates more receptors
48
Adaptation
Many receptors stop responding to a stimulus the longer it goes on for
49
Tonic receptors
Fire APs repeatedly during a stimulus - Frequency of AP will decrease as stimulus goes on - Slow adaptation
50
Phasic receptors
Signal AP when stimulus starts + stops - Not while it’s going on - Fast adapting
51
Labeled line coding
Each receptor travels to the CNS on a single tract/ line - CNS knows what receptor a signal comes from because it knows what line it comes from - Tells CNS modality, quality, + location of the stimulus
52
Sensory Pathways
The route a signal takes from receptor to the brain
53
Cortical Map
54
Touch Receptors
Detect pressure on skin + other places Mechanically gated ion channels When membrane is pushed on → Pulls ion channels open →Membrane depolarizes
55
Merkel cells
Specialized cells in the stratum basale that detect light touch
56
Merkel nerve endings
Afferent neurons with free nerve endings that are signaled by merkel cells
57
Tactile corpuscles
Small neurons with accessory structures that detect light touch under the epidermis, in the dermal papillae. Common in hairless skin Dendrites are wrapped with Schwann cells
58
Lamellar corpuscles
Big + deep in the dermis to detect deep touch and vibrations. A sensory neuron with accessory structure and many layers of collagen around its dendrites.
59
Bulbous corpuscles
Neurons with accessory structures to detect deep prolonged touch + skin stretching. Elongated connective tissue capsules around dendrites
60
Thermoreceptors
Pseudounipolar afferent neurons with free nerve endings that detect temperature. Their specialized channels only open at certain temperatures + chemicals Hot + cold have different receptors and travel on separate labeled lines (Hot receptors are deeper in the dermis)
61
Nociceptors
Neurons found everywhere with free nerve endings that detect pain Responding to cell damage: - Cells release chemicals when damaged - Nociceptors detect chemicals - WBCs can trigger nociceptors when they detect damage Also respond to noxious stimuli Information goes to the CNS or bipasses to other tissues
62
Noxious Stimuli
Things that can hurt you - Really high or low temps - Strong forces - Certain chemicals (acids)
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Visceral pain
Pain that you feel in visceral organs but don’t perceive as well as other parts of the body. Could be reffered pain.
64
Referred pain
= Experience visceral pain in other places in the body than where the injury actually is Causes nociceptors from both places travel on the same neuron Ex: heart attaches - feel on the medial size of the L arm
65
Itching
Itch receptors are pseudounipolar with free nerve endings that respond to chemicals that stimulate inflammation - histamines
66
What roll do muscle spindles play in prorioception?
As a major receptor to detect stretch/ changes in length in skeletal muscle Intrafusal fibers in - Muscle is stretched, intrafusal fibers (in connective tissue capsul) stretch + pull together, that stimulates the afferent neurons - Fibers stimulated to contract at the same time as muscle - Muscle spindle gets shorter - Remains tight as the muscle contracts
67
Intrafusal fibers
Muscle cells inside the connective tissue capsule of muscle spindles with afferent neurons wrapped around. Contract at the same time as muscle when stimulated.
68
What roll do golgi tendon organs play in proprioception?
As a major receptor in tendons with neurons wrapped around its collagen fibers and surrounded by capsul. Muscle contracts → collagen fibers pull together → stimulates neuron
69
Joint Receptors
Are found around joint capsules to detect how bent a joint is Associated structures: lamellar + bolbous corpuscles, gogi organs, nociceptors
70
First Order Neurons ## Footnote Path to pain
Pseudounipolar sensory neurons that enter the spinal cord on the dorsal root or brain stem. - Branches in the spinal cord - Some branches synaps on neurons in the spinal cord for reflexes - Some branches synapse on second order neurons in the spinal cord or the axons of first order neurons that can travel up the spinal cord and synaps in the brain stem
71
Second Order Neuron
Stimulated by first order neurons then go the thalamus and stimulate third order neurons
72
Third Order Neurons
Start in the thalamus then signal cells in the somatosensory cortex Some signals go directly to the cerebellum, bypassing the thalamus
73
Somatosesory cortex
Where you perceive all your somatic senses on the post central gyrus = both homunculus

Bio 20A (21 decks)

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