Neurophysiology Lec8 PDF

# Basal Ganglia ## D. SARA ABDOU Lecturer of physiology Faculty of medicine Menoufia university # The Cerebellum and the Basal Ganglia - In addition to areas in the cerebral cortex that stimulate muscle contraction, two other brain structures are essential for normal motor function—the cerebellum...

# Basal Ganglia ## D. SARA ABDOU Lecturer of physiology Faculty of medicine Menoufia university # The Cerebellum and the Basal Ganglia - In addition to areas in the cerebral cortex that stimulate muscle contraction, two other brain structures are essential for normal motor function—the cerebellum and the basal ganglia. Neither of these structures can control muscle function by itself. Instead, these structures always function in association with other systems of motor control. # Basal Ganglia is the Chief Part of Extra-pyramidal System - The basal ganglia do not give direct descending tracts to the motor nuclei in the spinal cord, but it affects them indirectly through its connection to brainstem centers as reticular formation, vestibular nucleus, and olivary nucleus. - So, basal ganglia lesion doesn't cause muscle paralysis, but causes disturbances in muscle tone and abnormal involuntary movements. # Basal Ganglia - Basal ganglia are a group of interconnected nuclei deep to the cerebral cortex & lateral to the thalamus. - They include 5 structures on each side of the brain: | 3 Large Nuclei | 2 Functionally Related Nuclei | | --------------------------- | ------------------------------ | | Caudate - putamen - globus pallidus | Subthalamus - substantia nigra | - Corpus striatum = caudate + putamen. - Lenticular nucleus = putamen + globus pallidus. # Anatomical Relations of the Basal Ganglia to the Cerebral Cortex and Thalamus, Shown in Three-dimensional View A diagram is showing the anatomical locations of the basal ganglia and the thalamus # Internal Capsule - A diagram is showing the anatomical location of the internal capsule, lentiform nucleus, caudate nucleus and the thalamus. # Anatomical Relations of the Basal Ganglia - A diagram is showing the anatomical locations of the basal ganglia with horizontal, lateral and frontal sections of the brain. # Function of Basal Ganglia - The basal ganglia are important for: - **Planning sequences** of patterns of movements to achieve a complex goal. (voluntary motor action) e.g. when a person is subjected to danger, he turns away from it then begins to run. - **Modifying the timing** of these patterns of movements (rapidly or slowly). - **Modifying the spatial dimensions** (Scaling) of movements (e.g. writing very small or very large letter) - The basal ganglia help the cortex to **execute subconscious learned patterns of movement** e.g. writing the letters of the alphabet, cutting with scissors to perform a particular movement. - Program of such movements are stored in basal ganglia. - Globus pallidus may be responsible for **posture** taken by the body to perform particularly voluntary movement i.e. it locks different parts of the body to facilitate the fine hand movements (control axial and girdle movements that provide background positioning of the body and proximal limb). - **Initiation** and **regulation** of gross intentional movements that are performed subconsciously. - **Initiation** and **regulation** of automatic associated movements of the body e.g. swinging of arms while walking & facial expressions. - **Inhibitory** to muscle tone (diffuse stimulation of BG). - Caudate +++ and lentiform nucleus --- muscle tone - **Controlling saccadic eye movements**. - **Motivation** (control of behavior). # Function of Basal Ganglia (Diagram) A diagram shows the function of basal ganglia in 10 points. - Control the motor activity - Chief part of extra-pyramidal system - Posture and coordination of large groups of muscles - Control of muscle tone - Planning and programming of voluntary movement - Preventing occurrence of abnormal involuntary movements - Control subconscious gross postural movements - Posture taken by the body during performance of particular voluntary movements - Learning and memory - Cognitive function # Direct and Indirect Pathway - **Direct pathway** - **Indirect pathway** # Direct Pathway of Basal Ganglia (Diagram) - A diagram is showing the direct pathway of the basal ganglia with the following: - **Cortex** - **Thalamus** - **Stratium** - **GPI** - **Substantia nigra compacta** - **Subthalamic nuclei** # Direct Pathway - The cortex ➡️ excitatory fibers to the striatum - The striatum ➡️ inhibitory fibers (secret GABA) to the internal segment of globus pallidus (Gpe) ➡️ inhibited GPe - Removes inhibition of the thalamus - The thalamus ➡️ excitatory input to the cortex ➡️ facilitates movement # Indirect Pathway of Basal Ganglia (Diagram) - A diagram is showing the indirect pathway of the basal ganglia with the following: - **Cortex** - **Thalamus** - **Stratium** - **GPE** - **Substantia nigra compacta** - **Subthalamic nuclei** # Indirect Pathway - The cortex excitatory fibers to the striatum. The striatum ➡️ inhibitory fibers (secret GABA) to the external segment (ES) of globus pallidus (GPE) ➡️ inhibited (GPE) removes inhibition of the subthalamus. - The subthalamus ➡️ excitatory input to the (GPI) of globus pallidus ➡️ inhibits VA & VL nuclei of the thalamus ➡️ indirectly inhibits the motor cortex ➡️ inhibits movement. # Indirect Pathway - Inhibition of the high activities of both motor and pre-motor areas preventing the occurrence of abnormal involuntary movements. # Consequences of Degeneration of the Pathway from the Compact Part of the Substantia Nigra (SNpc) to the Striatum (S) in Parkinson Disease (Diagram) - A diagram is showing the consequences of degeneration of pathway from the compact part of substantia nigra in Parkinson disease. # Basal Ganglia Pathways (Diagram) - A diagram is showing the pathway of the basal ganglia with the following: - **Cortex** - **Striatum** - **Globus pallidus (external)** - **Globus pallidus (internal)** - **Subthalamic nuclei** - **Substantia nigra (pars reticulata)** - **Substantia nigra (pars compacta)** - **Thalamus** # Caudate Circuit Through the Basal Ganglia for Cognitive Planning of Sequential and Parallel Motor Patterns to Achieve Specific Conscious Goals (Diagram) - A diagram is showing the caudate circuit through basal ganglia for cognitive planning. # Putamen Circuit Through the Basal Ganglia for Subconscious Execution of Learned Patterns of Movement (Diagram) - A diagram is showing the putamen circuit through the basal ganglia for subconscious execution of learned patterns of movement. # Basal Ganglia (Diagram) - A schematic organization of the basal ganglia with the following labels: - **Thalamocortical pathway** - **Cerebral cortex** - **Corticostriatal pathway** - **Striatum** - **Direct pathway** - **SNpc** - **Nigrostriatal pathway** - **Subthalamus** - **GPi/SNpr** - **Indirect pathway** - **GPe** - Differential modulation of direct (thick black arrow) and indirect (red) pathways by dopaminergic neurons from the compact part of the substantia nigra (blue). - **Excitatory connections** + - **Inhibitory connections** - - **GPi** - globus pallidus (internal part) - **GPe** - global pallidus (external part) - **SNpc** - substantia nigra (compact part) - **SNpr** - substantia nigra (reticular part) # Disorders of Basal Ganglia - Diseases of basal ganglia characterized by: - **Involuntary movements during rest** (inhibited during sleep) and voluntary movements and exaggerated by emotion and stress. - **Hypertonia** (except chorea). - Appear in the **opposite side of the body**. # Disorders of Basal Ganglia - **Chorea (dancing)** - **Hemiballismus** - **Athetosis** - **Parkinson's disease** # Disorders of Basal Ganglia - A lesion in the **subthalamus** often leads to sudden, rapid, violent, involuntary flailing movements of an entire limb, a condition called **hemiballismus**. - Multiple small lesions in the striatum lead to flicking movements in the hands, face, and other parts of the body, called **chorea (dancing movement)**. - Lesions of the **substantia nigra compacta** lead to the common and extremely severe disease of rigidity, akinesia, and tremors known as **Parkinson's Disease**. - Lesions in the **globus pallidus** frequently led to spontaneous and often continuous writhing movements of a hand, an arm, the neck, or the face (twisting snake-like movements). These movements are called **athetosis.** # Parkinson Disease (PD) (Paralysis Agitans) - The three cardinal clinical features of PD are **bradykinesis, rigidity and tremor**. - **Bradykinesis** (slowness of movement) includes delay in initiation of and poverty of movement (hypokinesis), and difficulty stopping one motor action and starting another. Rigidity is an increase in muscle tone. - The tremor of PD is maximal at rest and reduced by voluntary movement. # Parkinson's Disease Symptoms - **Stooped posture** - **Masked Face** - **Back rigidity** - **Forward tilt of trunk** - **Flexed elbows and wrists** - **Reduced arm swing** - **Hand tremor** - **Tremors in the legs** - **Slightly flexed hip and knees** - **Shuffling, short stepped gait** # Consequences of Degeneration of the Pathway from the Compact Part of the Substantia Nigra (SNpc) to the Striatum (S) in Parkinson Disease (Diagram) - A diagram is showing the consequences of degeneration of the pathway from the compact part of the substantia nigra in Parkinson's disease. # D. SARA ABDOU - A pink background with a white gift box sitting on the bottom of it. There are 10 white balloons with white and pink stripes floating above the gift box.