Lecture 11

Question 1

How does the nervous system produce movement and respond to sensation?

Answer 1

• Functional anatomy of movement
• Basal ganglia and cerebellum
• Vestibular system
• Somatosensory system

Question 2

Main components of the motor system

Answer 2

• Forebrain: initiating movement
• Brain stem: species-typical movement
• Spinal cord: executing movement

Question 3

Main motor assisting brain regions

Answer 3

• Basal ganglia (forebrain): help to produce the appropriate amount of force
• Cerebellum (brainstem): regulate timing and accuracy

Question 4

3 stages of movement execution

Answer 4

Planning: prefrontal cortex
Organisation: premotor cortex
Execution: primary motor cortex

Question 5

Planning - prefrontal cortex

Answer 5

Specify goal and decide to execute a movement

Question 6

Organisation - premotor cortex

Answer 6

Specify precise complementary movements needed to execute the plan (organise motor sequences)

• Preprogrammed set of movements produced as a single unit

Question 7

Execution - primary motor cortex

Answer 7

Translate motor sequences into motor commands that produce specific movements (specialised in focal skilled movements)

Question 8

Simple movement

Answer 8

Blood flow increased in the hand area of hte primary somatosensory and primary motor cortex when subjects used a finger to push a lever.

• M1 and S1

Question 9

Movement sequence

Answer 9

Blood flow increased in the premotor cortex when subjects performed a sequence of movements

• M1 and S1
• Dorsal premotor

Question 10

Complex movement

Answer 10

Blood flow increased in the prefrontal and temporal cortex when subjects used a finger to find a route through a maze

• M1 and S1
• Dorsal premotor
• Prefrontal (goal)
• Temporal (what)
• Parietal (how)

Question 11

Hierarchical and parallel control organisation

Answer 11

H = prefrontal > premotor > primary motor
P = plan and execute multiple independent movements simultaneously

Question 12

What does it mean that motor movements are spatially coded > somatotopic arrangement?

Answer 12

Body part relative sizes are disproportionate

• More extensive areas of M1 allow precise regulation of movements

Body parts are discontinuous

• Arranged different from those of our actual body

Question 13

Corticospinal tract

Answer 13

• originates mainly in motor cortex layer V
• ends in anterior horn of spinal cord
• aka pyramidal tract, axon crossing in medulla (brain stem)

Question 14

corticospinal tract - 2 descending pathways

Answer 14

1. lateral corticospinal tract: crosses in medulla, brainstem
2. ventral (anterior) corticospinal tract: uncrossed

Question 15

lateral corticospinal tract

Answer 15

• crosses over to the contralateral side
• ends at the lateral region of the contralateral anterior horn
• distal musculature
• NB: mainly lateral interneurons and motor neurons

Question 16

ventral (anterior) corticalspinal tract

Answer 16

• remains on the ipsilateral side
• ends in the medial region of the ipsilateral anterior horn
• proximal musculature
• NB: mainly medial interneurons and motor neurons

Question 17

spinal cord

Answer 17

• neurons in the spinal cord form a butterfly structure
• in the middle is the central canal containing CSF

Question 18

neuromuscular junction

Answer 18

the connection between the motor neurons of the spinal cord and the muscle fibres is called the

• neurotransmitter: acetylochile
• limb muscles are arranged in pairs: extensor and flexor

Question 19

nuclei in the basal ganglia

Answer 19

• caudate nucleus
• putamen
• globus pallidus
• neucleus accumens
• subthalamic nucleus
• substantia nigra

Question 20

movement issues connected to basal ganglia

Answer 20

hypokenetic - too little force

• paucity of movement (rigidity)
• parkinson (substantia nigra)

hyperkinetic - too much force

• excessive involuntary movement
• huntington’s disease (caudate & putamen)

Question 21

cerebellum - movement

Answer 21

functions in the cerebellum mainly concern the timing and accuracy of movements - critical for acquiring and maintaining motor skills

Question 22

cerebellum - somatotopic arrangement

Answer 22

• base (flocculus) - eye movements and balance
• medial - face and trunk
• lateral - limbs, hands, feet and digits

Question 23

intention, action and feedback model

Answer 23

cerebellum compares intended action with actual action, calculates error and informs the cortex how to correct the movement

Question 24

the vestibular system

Answer 24

the vestibular system is involved i the motor functions that allow us to maintain balance

• it is located in the inner ear and consists of 2 groups of receptors

Question 25

2 vestibular groups

Answer 25

1. semicircular canals 2. otolith organs

Question 26

semicircular canals

Answer 26

- 3 canals, 1 for each plane of movement (3D) - contains vestibular hair cells - filled with endolymph - mead movements moves endolymph. bends the cilia and induces action potentials - function: head orientation > detect head rotations

Question 26

otolith organs

Answer 26

- utricle, saccule - contains vestibular hair cells - filled with jelly-like substance that contains small calcium carbonate crystals (otoconia) - head tilting presses gelatin and otoconia against hair cells, bends the cilia and induces action potentials - function: body orientation, detect gravity (tilt) and linear acceleration (translational movement)

Question 27

the somatosensory system

Answer 27

somatic sensation is unique since it is distributed throughout the body. - density of somatosensory receptors varies greatly throughout the body

Question 28

3 receptor systems in the somatosensory system

Answer 28

nociception (irritation) - pain, temperature, itch hapsis (pressure) - fine touch and pressure proprioception (bodyawareness) - perception of body location and movement based on stretch of muscles, tendons and join movement

Question 29

rapidly adapting receptors

Answer 29

activate neurons when stimulation begins and ends - sends information about the stimulus onset and offset

Question 30

slowly adapting receptors

Answer 30

activate neurons as long as the sensory stimulation is present - send information about whether the stimulus is still occurring

Question 31

diameter and myelination of receptors

Answer 31

hapsis & proprioception = larger, well myelinated (faster) nociception = smaller, less myelinated axons (slower)

Question 32

posterior spinothalamic tract (dorsal)

Answer 32

- hapsis - proprioception - posterior/dorsal column (spinal cord to brainstem) - crosses to contralateral side in brainstem - via medial lemniscus to ventrolateral thalamus to S1

Question 33

anterior spinothalamic tract (ventral)

Answer 33

- nociception - anterior spinal cord (grey matter) - crosses to contralateral side in spinal cord - via medial lemniscus to ventrolateral thalamus to S1

Question 34

monosynaptic reflex

Answer 34

- tapping patellar tendon stretches quadriceps - stretch-sensitive sensory receptor synapses directly to a single motor neuron in the spinal cord - motor neuron stimulates quadriceps to contract

Question 35

pain gating theory

Answer 35

- attempts to explain the phenomenon that acute sharp pain can be diminished by rubbing or massaging of the painful spot - might explain the pins and needles sensation - decreased blood flow deactivates large myelinated touch and pressure fibres, leaves small unmyelinated pain fibres unaffected

Question 36

somatosensory cortex

Answer 36

somatotopic representation in the primary somatosenosry cortex is organised in four separate homunculi that respond to - 3a, 3b - 1 - 2 - receptive cells increase from back to front 3a,3b,1,2

Question 37

unilateral spinal cord injuries

Answer 37

- ipsilateral loss of hapsis and proprioception - contralateral loss of nociception