Pyramidal motor system

Question 1

Give an overview of the motor system

Answer 1

Somatic nervous system
Voluntary control over movement
Broadmann’s area 4- primary motor cortex at frontal lobe, pre central gyrus
Cortex sends UMNs to spinal cord(corticospinal) and brainstem(cortibulbar) and LMNs to skeletal muscle.

Question 2

What sort of fibres are upper motor neurones?

Answer 2

Projection fibres- carry info from cortex to other regions of brain and sc

Question 3

What are commisural fibres

List them

Answer 3

Exchange info between hemispheres
Corpus callosum- between cortices
Fornix- hip to mam bodies
Anterior commissure- connect amygdalas
Posterior commissure- thalamus to superior colliculus

Question 4

What are association fibres?

List them

Answer 4

Exchange info within one hemisphere
superior and inf longitudinal fasciculus
Uncinate fasciculus, cingulate fasciciulus
occipito-temporalis, occipito-frontalis
fasciculus arcuatus

Question 5

Name the three parts of the corpus callosum

Answer 5

Genu
Isthmus
Splenium

Question 6

Describe the corona radiata

Answer 6

Afferent and efferent projection fibres

Question 7

Describe Betz cell

Answer 7

UMN
originate in layer 5 (IP) of cortex
Rapid conductance, low threshold for action
Large cell bodies

Question 8

Describe the internal capsule

List the three parts

Answer 8

Convergence of the corona radiata. White matter tract
anterior limb
genu- UMNs- head and face movement
posterior limb- UMNs from primary motor cortex- arm, trunk, leg movement
Corticospinal tract
Sensory fibres from thalamus to the primary somatosensory cortex

Question 9

Summarise the pyramidal tracts

Answer 9

UMNs from pmc–CR–IC–cerebral peduncles–brainstem–sc
2 tracts
corticobulbar- cranial nerves, ends at brain stem
corticospinal- 1m nerve fibres
60m/s
Anterior-same side- decussates at required level, innervates trunk
Lateral- decussates at medulla, synapse with interneurones and lmns, innervates limbs and digits

Question 10

What is the function of the corpus callosum?

Answer 10

Connects all cortices

Question 11

What is the function of the fornix?

Answer 11

Connects hypothalamus to hippocampus– mamillary bodies and third ventricle
MEMORY

Question 12

What is the function of the anterior commissure?

Answer 12

Connects temporal lobes (amygdala)

EMOTION

Question 13

What is the function of the posterior commissure?

Answer 13

Connects superior colliculus to the thalamus

VISION