NeuroAnatomy - Lecture Seven Objectives Thalamus & Basal Ganglia Flashcards
Where is the Thalamus located?
the lateral regions of the diencephalon // “sit on top of the brainstem”
Where is the Thalamus in relation to the Internal Capsule?
Thalamus is located medial to the IC
What is the blood supply of the thalamus?
deep branches of the posterior cerebral atery (PCA) and posterior communicating arteries
What is the function of the thalamus?
relays and regulates all sensory information going to cortex EXCEPT olfactory
The thalamus acts as the blank…
gateway to consciousness
What is the pathway for the visual function of the thalamus?
eye → thalamus → primary (1°) visual cortex (area 17) → secondary/associative visual cortices
What is the pathway for the auditory function of the thalamus?
ear → thalamus → primary (1°) auditory cortex (area 41) → secondary/associative auditory cortices
What is the pathway for the somatosensory function of the thalamus?
body → thalamus → primary (1°) somatosensory cortex (area 3,1,2) → secondary/associative somatosensory cortices
What are the 5 Thalamic Nuclei?
Medial Geniculate (MGN), Lateral Geniculate (LGN), Ventral Posterior Medial (VPM), Ventral Posterior Lateral (VPL), and Ventral Lateral (VL)
Where does the MGN get it’s information from?
the brainstem
Where does the MGN send it’s information to?
primary auditory cortex (Brodmann’s 41)
Where is the MGN located on the Thalamus?
posterior small bump, medially
What type of information does the MGN carry?
Auditory
Where does the LGN get it’s information from?
the eye
Where does the LGN send it’s information to?
primary visual cortex (brodmann’s 17)
Where is the LGN located on the Thalamus?
posterior small bump, laterally
What type of information does the LGN carry?
visual
Where does the VPM get it’s information from?
cranial nerves
Where does the VPM send it’s information to?
primary somatosensory cortex (Brodmann’s 3,1,2)
Where is the VPM located on the Thalamus?
posterior-medial
What type of information does the VPM carry?
somatosensory information of head/face
Where does the VPL get it’s information from?
spinal cord
Where does the VPL send it’s information to?
primary somatosensory cortex (Brodmann’s 3,1,2)
Where is the VPL located on the Thalamus?
posterior-lateral thalamus
What type of information does the VPL carry?
somatosensory information of body
Where does the VL get it’s information from?
basal ganglia and cerebellum
Where does the VL send it’s information to?
primary and premotor cortex (brodmann’s 4 and 6)
Where is the VL located on the Thalamus?
mid thalamus, laterally
What type of information does the VL carry?
motor information
What is the clinical name of Thalamic Pain Syndrome?
Dejerine-Roussy Syndrome
How is Dejerine-Roussy Syndrome caused?
Lacunar/Small vessel stroke that occurs in posterior thalamus and damages somatosensory pathways to cortex
What are the symptoms of Dejerine-Roussy Syndrome?
contralateral loss of sensation, neuropathic pain (burning, shooting, stabbing, throbbing, etc)
Where is the basal ganglia located?
in the diencephalon and midbrain
What is the basal ganglia pathway?
anterior association area → premotor cortices/motor cortex → basal ganglia → thalamus → premotor/primary motor cortices
What happens if there is a lesion in the basal ganglia/cerebellum?
there will be impaired motor function
What does impaired basal ganglia movement look like?
hypokinesia or hyperkinesia
What does impaired cerebellum movement look like?
motor tone, balance/posture, and coordination are all impaired
What are the structures within the basal ganglia?
caudate nucleus, nucleus accumbems, putamen, globus pallidus external/internal, subthalamic nuclei, substantia nigra
What is the “striatum” in the basal ganglia?
caudate and putamen
What is the “lenticular nucleus” in the basal ganglia?
globus pallidus and putamen
What is the blood supply of the basal ganglia?
Lenticulostriate arteries // smaller portion of basal ganglia supplied by small penetrating branches of ACA
What is the function of the basal ganglia?
initiating and executing movement
What are the 3 pathways of the basal ganglia?
motor loop, association (cognitive) loop, and limbic loop
What is the function of the motor loop of the basal ganglia?
modifies the motor plan to initiate and execute movement
What is the association (cognitive) loop of the basal ganglia?
learning/choosing the best ways to initiate and execute movement
What is the limbic loop of the basal ganglia?
supplies emotional input to the motor plan and influences how movement is initiated and executed
What is the motor loop pathway?
Premotor/motor cortex sends motor plan → putamen → globus pallidus internus → thalamus
What does Dopamine/Ach do in the motor loop DIRECT pathway?
Dopamine stimulates the direct pathway/promotes movement and Ach inhibits the direct pathway/supresses movement
What does Dopamine/Ach do in the motor loop INDIRECT pathway?
Dopamine inhibits the indirect pathway and promotes movement / Ach stimulates the indirect pathway and supresses movement
What produces Dopamine in the basal ganglia?
Substantia nigra
What produces Ach in the basal ganglia?
Putamen
What is a hypokinetic disorder?
loss of dopamine / excess Ach and supresses movement. Pt has difficulty initiating / executing tasks
What is a hyperkinetic disorder?
loss of Ach / excess dopamine and promotes too much movement. Pt experiences constant initiation and execution of abnormal movements
what is the order of movement disorders listed from slowest to fastest?
bradykinesia, rigidity, dystonia, athetosis, chorea, ballismus, tic, myoclonus, and clonus
What is bradykinesia?
slowed movement
what is rigidity?
increased resistance to PROM // bi-directional
what is lead-pipe rigidity?
resistance persists throughout entire ROM
what is cogwheel rigidity?
periodic resistance at different points throughout ROM
what is dystonia?
involuntary, sustained, or intermittent muscle contractions that cause twisting/repetitive movements, abnormal postures, or both
what is athetosis?
slow, continuous, involuntary writhing movement that prevents maintenance of a stable posture]
which is slower: dystonia or athetosis?
dystonia
what is chorea?
ongoing random-appearing sequence of one or more discrete involuntary movements // “dance-like involuntary movements”
what is hemi-ballismus?
flailing, flinging, or rotary movements of proximal limbs
where would a lesion be that causes hemi-ballismus?
a lesion in the subthalamic nuclei // indirect pathway
what are tics?
repeated, individually recognizable, intermittent movements
what are the two tics?
motor tics and vocal tics
what are tremors?
Rhythmic back-and-forth or oscillating involuntary movement about a joint axis
what is a resting tremor?
oscillating movement occurs at rest in a postural position, but once movement starts the tremor stops
what is an intention tremor?
oscillating movement occurs as arm approches “intended target” and tremor increases as target gets closer. Stops when arm is resting in postural position
what is myoclonus?
Sequence of repeated, often non-rhythmic, brief shock-like jerks due to sudden involuntary contraction or relaxation of one or more muscles
what is clonus?
Muscular spasm involving repeated, often rhythmic, rapid contraction/relaxation
