Section 5a: Motor System and Action

Question 1

what is the top half of brain and brainstem called?

Answer 1

dorsal

Question 2

what is bottom half of brain and brainstem called?

Answer 2

ventral

Question 3

what is the top of head called?

Answer 3

superior

Question 4

what is front of head called (face)

Answer 4

anterior

Question 5

what is the back of the head called?

Answer 5

posterior

Question 6

what is bottom of head called?

Answer 6

inferior

Question 7

what is front of brain called?

Answer 7

rostral

Question 8

what is back of brain called?

Answer 8

caudal

Question 9

what are the 5 major divisions of the CNS?

Answer 9

• spinal cord
• cerebrum (aka telencephalon)
• dice-halon
• brainstem
• cerebellum

Question 10

structure of the cerebrum

Answer 10

wrinkled grey matter 3-5 mm thick
Gyrus - is the ridge of wrinkle
Sulcus - the groove of 2 gyri

Question 11

components of the cerebrum

Answer 11

• hippocampus: memory and navigation
• amygdala: memory and emotions
• parts of the basal ganglia

Question 12

what is contained in the diencephalon?

Answer 12

• thalamus- all senses (except smell) go through this
• subthalmaus
• hypothalamus

Question 13

what is contained in the brainstem

Answer 13

• hindbrain (pons and medulla)
• midbrain (tectum and tegmentum)
• reticular foramen

Question 14

explain the parts of the hindbrain

Answer 14

pons: main connection to the cerebrum
medulla: keeps you alive

Question 15

explain the parts of tectum in the midbrain

Answer 15

superior colliculi: relates to movement of the eyes
inferior colliculi: relates to auditory system

Question 16

what are the parts of the spinal cord?

Answer 16

coccygeal (1)
sacral (5)
lumbar( 5)
thoracic (12)
cervical (8)

Question 17

what does each section of the spinal cord control?

Answer 17

cerivical - arms (upper limb muscles)
thoracic - trunk, chest and abdominal muscles
lumbar - legs and lower back
sacral - bowels and bladder

Question 18

what does the white matter and gray matter contain?

Answer 18

gray matter: made of cell bodies
white matter: axons forming the ascending and descending tracts

Question 19

what comes through the Doral roots in the grey matter?

Answer 19

sensory neurons (afferent)

Question 20

what comes through in the ventral roots of the grey matter?

Answer 20

motor neurons (efferents)

Question 21

how are spinal motor neurons organized in spinal cord?

Answer 21

aka alpha motoneurons
- the cell bodies like in longitudinal column called motor nuclei
- motor neurons for proximal muscles are medial
- motor neurons for distal muscles are lateral

Question 22

what informations does the ascending and descending tracts carry?

Answer 22

ascending tract: mostly sensory
descending tract: motor

Question 23

define what a motor unit represents and how they are organized?

Answer 23

it is the motor neuron and the muscle fibre its connected to
all the muscle fibres connected to one neuron are the same fibre type (fast or slow twitch)

Question 24

which type of motor unit is activate first and why?

Answer 24

slow twitch is activate first as they fatigue later, this saves energy of the muscle

Question 25

how does the connection of motor neuron to muscle fibre work?

Answer 25

each muscle fibre is connected to one neuron but one neuron can be connected to many muscle fibres

Question 26

what is a synaptic bouton?

Answer 26

it multiple bundles that come off the axon at the end plate

Question 27

what're the 3 ways different ways the nervous system can increase muscle force

Answer 27

- recruiting different size motor units - activating more motor units - increasing frequency of action potentials in the muscle fibre

Question 28

How does activating more motor units increase muscle force? (what is the relationship between contractile force and motor unit size)

Answer 28

large motor units have more muscle fibres so large muscles have many motor units MU Y: 7 fibers MU X: (5 fibers) tension is increased by recruiting more motor units

Question 29

How can recruiting different size motor units increase muscle force?

Answer 29

low frequency of stimulation from CNS activates smaller motor units as they have a smaller threshold of activation As the stimulation increases, it activates the large motor units as they have a higher threshold. Large motor units increase muscle force

Question 30

how does increasing frequency of action potentials in the muscle fibre increase muscle force

Answer 30

as the frequency increases the it eventually reaches maximum force generation, The slower the movement, the more stimulation which means higher frequency and larger motor units are recruited.

Question 31

Why do neurons form simple and complex neural pathways?

Answer 31

they have the ability to change other neurons ability to transmit information

Question 32

explain a why a monosynaptic stretch reflex happens and how?

Answer 32

it is used to maintain muscle length or position - when muscle is stretched 1a afferent neuron directly signals the alpha motoneuron (monosynaptic) to contracts the muscle - at the same time the 1a afferent neuron signals the 1a inhibitory interneuron to inhibit the alpha motorneuron for the antagonist muscle from firing (a disynaptic pathway)

Question 33

explain a why withdrawal (flexion) reflex happen and how?

Answer 33

used to remove limb from painful stimulus - the painful stimulus is detected by the free nerve ending and sent through a sensor neuron - pain and postural stimulus is sent to the brain through an ascending pathway - at the same time, withdrawal stimulus is sent through a polysynaptic pathway to the muscles

Question 34

explain a crossed extension reflex and why happen

Answer 34

used to increase support when withdrawal flexion throws body of balance - when a postural stimulus is received to the brain, motor neurons are on opposite limb are sent a stimulus to maintain balance

Question 35

explain sensory feedback control

Answer 35

descending commands can override the reflexes when needed to maintain task

Question 36

explain supraspinal modulation

Answer 36

supraspinal modulation can desensitize/sensitize an area to a stimulus to decrease/increase frequency needed for action to occur

Question 37

explain the components postal reflex

Answer 37

when balance perturbed - SLR (short latency reflex): monosynaptic reflex - MLR (medium latency reflex): integration of information from brainst;em - LLR (long latency response) cortex information integrated as well (not really a reflex)

Question 38

explain how reflexes are adaptable

Answer 38

task dependant reflexes will stop movement of a muscle that is needed to maintain task

Question 39

what is a CPG?

Answer 39

central pattern generator, it is a neural network that has the ability to perform a rhythmic pattern of motor activity (usually continuous task) after being triggered sensory input (doesn't need sensory to maintain it)

Question 40

how does a CPG work and where are they found?

Answer 40

found in the cerivla and lumbar sections or the spinal cord, the flexor and extensor circuits will mutually inhibit each other alternation the activation of each example walking: so that a swing and stance phase occur