Lesson 9 - Descending Pathways Flashcards
Descending systems modify all the activity of ————– systems, and are prominent in controlling conscious and reflex responses to stimuli
ascending
Motor areas:
- ————- ———- of frontal lobe
- Primary ——– ——- directs voluntary movements
Precentral gyrus
motor cortex
Sensory Areas:
- Postcentral gyrus of ———- lobe
- Primary sensory cortex:
receives somatic sensory information (touch, pressure, pain, vibration, taste, and temperature)
parietal
Functional Organisation
of the CNS:
(Primary Motor Cortex)
Functionally the ——— —— is known as the primary motor cortex.
precentral gyrus
Functional Organisation
of the CNS:
(Primary Motor Cortex)
Stimulation of the primary motor cortex elicits contraction of discrete muscle groups on the ———– side of the body.
The function of this region is the control of voluntary, skilled movements sometimes referred to as ———— movements.
opposite
fractionated
Functional Organisation
of the CNS:
(Primary Motor Cortex)
30% of ———– and ———- fibres arise from neurons of the primary motor cortex while 3% originate from giant ————— cells
corticospinal and corticobulbar
pyramidal cells
Functional Organisation
of the CNS:
(Primary Motor Cortex)
The principal subcortical afferents to the primary motor cortex originate from the ventral lateral nucleus of the thalamus which in turn receives input mainly from the ——- ———– of the cerebellum and from the ——– ——— of the basal ganglia.
dentate nucleus
globus pallidus
The ————- ———— represents either the motor or the sensory distributionalong the cerebral cortex of the brain.
cortical homunculus
The ———– ———is a topographic representation of the body parts and its correspondents along the precentral gyrus of the frontal lobe.
motor homunculus
The ———— homunculus is a topographic representation of the body parts along the postcentral gyrus of the parietal lobe.
sensory
Within the cortex of the precentral gyrus the contralateral half of the body is represented in a precise ———– fashion.
somatotopic
The Cortical Homunculus:
The representation of the body is inverted with the head area located in the most inferior part of the precentral gyrus just above the ———– fissure. Progressing superiorly successive areas of cortex represent the digits hand arm shoulder and trunk.
lateral
The Cortical Homunculus
The lower limb is represented on the medial surface of the hemisphere above the ——— ——-
corpus callosum.
The Cortical Homunculus
The area of cortex devoted to a particular body part is ————- not to its size but to the degree of precision with which movements can be executed therefore the larynx, tongue, face and digits of the hand are represented by relatively large regions period
proportional
Functional Organisation of the CNS (Premotor Cortex):
The region immediately anterior to the ——— ——– cortex is known as the premotor cortex.
primary motor
Functional Organisation of the CNS (Premotor Cortex):
On the ———- surface of the hemisphere, this includes the posterior portions of the superior, middle and inferior frontal gyri.
lateral
Functional Organisation of the CNS (Premotor Cortex):
On the ——— surface of the hemisphere, the premotor cortex includes a region referred to as the supplementary motor cortex.
medial
Functional Organisation of the CNS (Premotor Cortex):
Stimulation of premotor cortical areas induces movements that are less focused than those elicited from the ———- ———– cortex and that involves groups of functionally related muscles.
primary motor
Functional Organisation of the CNS (Premotor Cortex):
Movements evoked from the supplementary motor cortex tend to be postural in nature involving ———– and ———– musculature.
axial and proximal
Functional Organisation of the CNS (Premotor Cortex):
Premotor cortical areas are thought to function in the programming of and preparation for movement and in the control of ———
posture
Functional Organisation of the CNS (Premotor Cortex):
The premotor cortex exerts its actions partly via the primary motor cortex with which it is connected by short ———— fibres and partly via corticospinal and corticobulbar fibres.
~ 30% of the corticospinal and corticobulbar fibres originate in the premotor cortex.
association
Functional Organisation of the CNS (Premotor Cortex):
The principal subcortical input to premotor cortical regions is the ventral anterior nucleus of the thalamus. This in turn receives fibres from the ——- ———- and ——– ———
globus pallidus and substantia nigra
Functional Organisation of the CNS (Frontal eye field, motor speech area and prefrontal cortex):
Immediately in front of the premotor cortex on the lateral surface of the hemisphere are located two other important regions;
1) In the middle frontal gyrus lies the ——– —- ——. This region controls voluntary conjugate deviation of the eyes as occurs when scanning the visual field.
2) In the inferior frontal gyrus of the dominant hemisphere (usually the left) lies the motor speech area also known as ——–s area. ———-s area has important interconnections with parts of the ipsilateral temporal, parietal and occipital lobes that are involved in language function.
3) The extensive regions of the cortex of the frontal lobe that lie anterior to premotor areas are referred to as prefrontal cortex. The prefrontal cortex has rich connections with parietal, temporal and occipital cortex through long association fibers running in the subcortical white matter. Subcortical afferents arise mainly in the medial ——— dorsal and ——– nuclei of the thalamus. The prefrontal cortex has cognitive functions of a high order e.g. intellect, judgment, predictive faculties and the planning of behavior.
frontal eye field
broca
medial dorsal and anterior nuclei
Gross Anatomy of Motor Pathways
- ———- fibres: connect cortices of cerebral hemispheres.
The largest bundle forms the c——– ————.
Commissural
Corpus callosum
