2024 Student Basal Ganglia and Cerebellum Exam Breakdown PDF

Exam 3 Breakdown of Contents Friday, November 15th at 10:00 AM 40 questions (80 minutes) 1. Basal ganglia and Cerebellum from me- 10 questions 2. Brainstem sensory systems from Dr. Joy- 10 questions 3. Lab images- all fill in the blank- 10 questions 4. Thalamus/ Hypothalamus from Dr. Warner- 10 ques...

Exam 3 Breakdown of Contents Friday, November 15th at 10:00 AM 40 questions (80 minutes) 1. Basal ganglia and Cerebellum from me- 10 questions 2. Brainstem sensory systems from Dr. Joy- 10 questions 3. Lab images- all fill in the blank- 10 questions 4. Thalamus/ Hypothalamus from Dr. Warner- 10 questions Basal Ganglia Vuvi H. Nguyen MS, PhD Dept of Diagnostic and Biomedical Sciences Learning Objectives- Basal Ganglia Discuss the function of the basal ganglia. Describe the anatomical components of the basal ganglia. Compare and contrast basal ganglia input vs. output. Discuss the direct and indirect pathways of the basal ganglia. What is the basal ganglia? Masses of gray matter that lies deep within the telencephalon (cerebral hemispheres) Refers to a group of subcortical nuclei (groups of neurons that lie below the cerebral cortex) responsible for coordinating/ regulating voluntary movement Function of the Basal Ganglia Primary role is to take in initial signals from the motor cortex in the frontal lobe and then modify it as it passes down to the muscles in various parts of the body. Different parts of the basal ganglia act to amplify (excite) or diminish (inhibit) this initial signal→ refine movement Motor disorders such as Parkinson’s or Huntington’s disease stem from dysfunction of neurons within the basal ganglia The basal ganglia can also communicate with non-motor regions of the cerebral cortex and play a role in other behaviors such as emotional and cognitive processing. Location inferior to the cerebral cortex but superior to the brainstem reflects its role as an intermediary between our higher thoughts, sensations, and reflexes. Functions of the Basal ganglia Compared to impulses generated in the motor cortex, we are not necessarily conscious of the changes in movement produced by the basal ganglia. For example, when we decide to pet a dog, we are likely conscious of the initial decision to begin that action as it is first generated in the motor cortex. However, we are unaware of the small minute adjustments that the basal ganglia make to ensure that the action is smooth and that we are not petting the dog too soft or too hard.  Basal ganglia components Structures include: 1. Caudate nuclei Striatum 2. Putamen 3. Globus pallidus (2 parts: externus and internus) 4. Subthalamic nucleus 5. Substantia nigra The basal ganglia influences movement INDIRECTLY. (Do not project directly to motor neurons in spinal cord or brain stem.) They influence the output of cortical neurons through a series of direct and indirect pathways. The caudate and putamen are collectively referred to as the striatum (striped). The putamen and globus pallidus are collectively referred to as the lentiform nucleus (lens shaped nuclei). All 3: caudate + putamen + globus pallidus= corpus (body) striatum (striped) These structures work together as part of 2 interconnected pathways: direct and indirect pathways which act to modify signals from the motor cortex. These pathways both end up at the thalamus before looping back to modify motor signals coming from the cortex. Therefore, the specific effects of the basal ganglia have on the motor signal is heavily reliant on sensory information.  LATERAL VIEW PUTAMEN ANTERIOR CAUDATE ANTERIOR MEDIAL VIEW GLOBUS PALLIDUS = globus pallidus + putamen  Basal ganglia structures include: 1. Caudate nuclei 2. Putamen 3. Globus pallidus 4. Subthalamic nucleus 5. Substantia nigra Thalamus The globus pallidus is divided into two segments: the internal (or medial- bottom arrow) segment and the external (or lateral- top arrow) segment. The basal ganglia are subcortical structures located at the base of the forebrain. They are comprised of the caudate and putamen, which both make up the striatum, as well as the globus pallidus, substantia nigra, and subthalamic nucleus. Basal ganglia: defining nuclei Caudate nucleus Putamen Globus pallidus Subthalamic nucleus Substantia nigra  Basal ganglia: defining the nuclei Striatum (releases GABA) Caudate nucleus: highly involved in any form of goal-directed activity. Plays an important role in other cognitive functions such as memory and sleep. (Think of caudate as the most “cau-gnitive part” of the basal ganglia). Putamen: More exclusively dedicated to motor functions. Plays a role in preparing and executing voluntary movements. (If you see putamen- “put an M” for Motor!)  Basal ganglia: defining the nuclei Globus pallidus (releases GABA) Controls conscious and proprioceptive movement. So if damaged, it can cause movement disorders (e.g. tremors) Divided into internal (GPi) and external (GPe) segments. GPi- major output nuclei of the basal ganglia projecting to the thalamus. (Involved in both the direct and indirect pathway) GPe- involved in the indirect pathway only. Basal ganglia input Refers to bringing information FROM the cortex TO the basal ganglia. Majority of info. processed enters through the striatum (caudate + putamen) Principal source of input to the striatum is glutamatergic→ excitatory! Substantia nigra is the main source of dopaminergic input. Dopamine plays an important role in basal ganglia function. Dopamine projections can have either excitatory or inhibitory effects in the striatum, depending on the type of dopamine receptor the striatal neuron expresses. (Dopamine action at a Inputs to the basal ganglia enter through the striatum (the caudate and putamen). neuron that expresses D1 receptor is excitatory Cortical projections (shown in green) release glutamate and are excitatory. Substantia and D2 receptor is inhibitory). nigra projections (shown in blue) release dopamine and can be either excitatory or inhibitory.  Basal ganglia output Structures that send information FROM the basal ganglia TO the thalamus (and then back to the cortex). Primary output region is the internal segment of the globus pallidus (GPi). This region sends inhibitory GABAergic projections to nuclei in the thalamus. Output from the basal ganglia leaves through the internal segment of the globus This inhibitory output has a tonic, constant firing pallidus. Inhibitory projections (shown in red) release GABA onto the thalamus. rate, which allows the basal ganglia output to Excitatory thalamic projections (shown in green) communicate with the cerebral increase and decrease depending on the cortex. situation. The thalamus then projects out to the cerebral cortex via glutamate, primarily to motor areas. The internal segment of the globus pallidus sends GABA projections to the thalamus. The thalamus sends glutamate projections to the cortex. The Direct and Indirect Pathways- Let’s simplify this circuit. BASAL GANGLIA INPUT BASAL GANGLIA OUTPUT The Direct and Indirect Pathways ▪ GABA ▪ Glutamate Cortex ▪ Dopamine Direct pathway→ Stimulation of motor cortex Indirect pathway→ Inhibition of motor cortex Striatum GPe Big picture: Remember, these pathway help to REFINE movement. GPi SN STN GPi Thalamus  ▪ GABA Basal ganglia: Direct Pathway Remember, this pathway sends signals back to the cortex for further refining. ▪ Glutamate ▪ Dopamine Travels from the cortex (pre-motor) into the striatum into the globus pallidus internal (GPi) and finally to the thalamus which sends the signal back to the cortex for further refining (to increase motor activity). Comes Straight Into Thalamus: Cortex Striatum Internal (globus pallidus) The substantia nigra pars compacta (SNc) is thought to modulate the Thalamus activity of the direct pathway. Neurons from the substantia nigra pars compacta travel to the striatum and release dopamine in the striatum. One effect of this seems to be the facilitation of activity in the direct pathway.  ▪ GABA ▪ Glutamate Basal ganglia: Direct Pathway ▪ Dopamine Neurotransmitters involved: GABA- inhibitory Glutamate- excitatory Logic here follows the rules of math when multiplying positives and negatives. The striatum and the internal globus Excitatory pallidus (Gpi) both have an inhibitory projections that effect. But the inhibitory effect cancel stimulate each other by multiplying 2 negatives giving the direct pathway an overall movement. excitatory affect→ movement is facilitated! When input from either the cortex or substantia nigra (SN) increases in intensity, the direct pathway is activated. The neurons in the striatum involved in the direct pathway express the D1 metabotropic dopamine receptor, and the activation of this receptor is excitatory.  ▪ GABA Basal ganglia: Indirect Pathway ▪ Glutamate ▪ Dopamine Takes a longer route through the basal ganglia and generally insert a diminishing or inhibitory effect on the initial motor signal. Signal is generated in the cortex and travels to the striatum. However, it then exits the direct pathway via the globus pallidus externus (GPe), before traveling to the subthalamic nucleus (STN), the internal globus pallidus (GPi), and finally the thalamus. Comes Straight, Exits, then Sidesteps Into Thalamus: Cortex Striatum External globus pallidus Subthalamic nucleus Internal globus pallidus Thalamus  ▪ GABA Basal ganglia: ▪ Glutamate ▪ Dopamine Indirect pathway Neurotransmitters GABA- inhibitory Glutamate- excitatory There are 3 inhibitory neurotransmitters and 1 excitatory neurotransmitter in this pathway. So following rules of math: X X X = Indirect pathway is activated by excitatory cortical input, activating inhibitory striatal neurons. Indirect pathway is inhibited by dopamine Thus, the indirect pathway when activated inhibits release from the substantia nigra (SN). The neurons in the striatum movement. involved in the indirect pathway express the D2 receptor. The activation of this receptor is inhibitory→ will inhibit the inhibitory striatal neurons. Basal ganglia: defining nuclei Caudate nucleus Putamen Globus pallidus Subthalamic nucleus Substantia nigra Basal ganglia: defining the nuclei Subthalamic nucleus (STN) (releases glutamate) Lies below the thalamus at its junction with the midbrain Found only in the indirect pathway Acts on the internal globus pallidus to produce inhibition of movement STN inhibitory effects are found in a movement disorder known as hemiballismus Hemiballismus Movement disorder that involves flailing movement of the limbs- like someone is involuntarily swinging a golf club or throwing a football Occurs after the STN becomes damaged as the inhibitory pathway has been removed resulting in excessive movements Subthalamic Nucleus Sunday Night Football Memory Trick: Think of someone swinging their arm while throwing a football during Sunday Night football: Subthalamic Nucleus to remember hemiballismus in the subthalamic nucleus.  Basal ganglia: defining the nuclei Substantia nigra (SN)- Latin for “black substance” located in the midbrain of brainstem Not immediately involved in the direct and indirect pathway. Plays a role in modifying the movement acting on the striatum directly. Uses the neurotransmitter dopamine to influence the basal ganglia. Dopamine does not cause movements but rather facilitates them; makes movements fast, fluid, and smooth Someone with reduced dopamine on the substantia nigra (person with Parkinson’s disease) will be less likely to initiate movements leading to muscle stiffness, rigidity, and slowness.  Basal ganglia: defining the nuclei The substantia nigra can be divided into two parts: the substantia nigra pars compacta (SNpc) and the substantia nigra pars reticulata (SNpr). ▪ The SNpc receives input from the caudate and putamen and sends information right back. ▪ The SNpr also receives input from the caudate and putamen but sends it outside the basal ganglia to control head and eye movements. The SNpc is the more famous of the two, as it produces dopamine, which is critical for normal movement. The SNpc degenerates in Parkinson's disease. Parkinson’s Disease Substantia nigra cells slowly die- impacts Motor Symptoms input to striatum (caudate, putamen) Dopamine depletion Tremor at rest Rigidity Bradykinesia (slow movement) Postural instability Fenestrated gait (being stuck in place, when taking a step or turning) Slower blink rate Basal Ganglia Key Takeaways The subcortical basal ganglia nuclei receive information from the cortex and sends output to the thalamus Motor control through the basal ganglia occurs through both the direct and indirect pathways. Remember that it’s generally involved in refining motor signals! Therefore, abnormalities involving the basal ganglia often produce motor disorders. Dysfunction of the basal ganglia leads to uneven, uncoordinated and or rough movements that are either excessive or insufficient depending on which part is damaged. (Note: You wouldn’t expect full on weakness or paralysis of muscles resulting from a lesion of the basal ganglia for the most part because they are NOT involved in producing motor signals directly.) Basal ganglia is also critical for emotion and behavioral inhibition. Anatomy of the Cerebellum Vuvi H. Nguyen MS, PhD Dept. of Diagnostic and Biomedical Sciences Learning Objectives- Cerebellum Identify the lobes of the cerebellum and what they are functionally referred to. Explain the function of each lobe of the cerebellum. Explain the fibers in which each cerebellar peduncles carry. Describe the deep cerebellar nuclei and the functional regions associated with it. Discuss the layers of the cerebellar cortex and the cells that are found in them. Big Picture Reminders Movement is produced by complex interactions of the cerebral cortex, the basal ganglia, and the cerebellum. The cerebral cortex is involved in planning and execution of voluntary movement. The basal ganglia initiate motor activity and modulate cortical output related to motor function. The cerebellum functions in the coordination of movements. Cerebellum- Function Translates to “little brain” Assists with coordinating and adjusting voluntary movement- posture, balance, maintenance of muscle tone, and coordinated skilled motor activities. Learning and memory of motor tasks.  Cerebellum- Function In constant communication with the cerebral cortex and spinal cord Sends and receives signals to many structures in the CNS and PNS Processes information about current movement and position to help refine, correct, and improve motion. Based on all of that input, the cerebellum comes up the motor plan for the timing and initiation of the movement and the speed and the direction and the precision and then figures out what muscle group needs to work together. It’s like the ultimate event planner. Cerebellum Located at the posterior cranial fossa in the cranial cavity Cerebellum Anatomy Consists of 2 lateral hemispheres separated by a narrow ridge in the middle called the vermis. Divided into 3 lobes: anterior lobe, posterior lobe, and flocculonodular lobe Cerebellum Anatomy The anterior lobe is separated by the posterior lobe via the primary fissure. Functionally, the anterior lobe is referred to the spinocerebellum Responsible for the regulation of muscle tone and adjusting movements through proprioception input (signals of muscle stretch receptors) Posterior lobe Cerebellum Anatomy Posterior lobe is functionally referred to as the cerebrocerebellum, or pontocerebellum (largest part of the cerebellum) Primary fissure Anterior lobe Contains the horizonal fissure- separates the superior and inferior surface of the cerebellum Responsible for assisting in planning and programming of skilled or fine motor movements. = Cerebrocerebellum Cerebellum Anatomy The posterior lobe is bounded by the posterolateral fissure- separates the Flocculonodular lobe= posterior lobe from the vestibulocerebellum flocculonodular lobe. Anterior lobe Flocculonodular lobe is named because it contains a central part of the vermis called the nodule and two lateral flocculi This lobe is functionally called the Posterior vestibulocerebellum which is lobe responsible for maintenance of posture and balance. Cerebellum Anatomy Flocculonodular lobe- narrow strip of tissue (flocculus + nodule). Involved in the control of posture and coordinating eye movements and spatial orientation using info from the vestibular system in the inner ear. The posterolateral fissure separates the posterior lobe from the flocculonodular lobe. Cerebellum Anatomy Cerebellar Tonsils are hemispheric structures of the posterior lobe; lie along the vermis Responsible for coordinating voluntary movements of distal parts of the limbs. Cerebellum Anatomy *Bundles of white matter that attach the cerebellum to the brainstem. Cerebellum Anatomy Superior cerebellar peduncle- connects cerebellum with midbrain. Consists of predominantly of efferent pathways arising from the cerebellar cortex, and the deep cerebellar nuclei. Middle cerebellar peduncle (cut)- connects cerebellum with pons carrying majority afferent signals. Inferior cerebellar peduncle- connects cerebellum with medulla. Contains mostly afferent pathways from the spinal cord and brainstem to the cerebellum. External gray matter= cerebellar cortex Subcortical white matter= tree- like arrangement → Arbor vitae Cerebellar nuclei On transverse section of the cerebellum, there are 4 clusters of deep gray matter nuclei (clusters of neuronal cell bodies) buried deep within the subcortical white matter. Multipolar neurons that receive signals from the cerebellar cortex and other parts of the nervous system. Axons contribute to the formation of the three cerebellar peduncles. How to remember names of the nuclei? From lateral to medial: Don’t= Dentate; Eat= Emboliform nucleus; Greasy= Globose; Foods= Fastigial  Cerebellar nuclei The deep cerebellar nuclei are the main source of cerebellar output (from cerebellum to the cerebral cortex). Therefore, a lesion to the cerebellar nuceli has the same effect as complete lesion of the cerebellum. Four deep cerebellar nuclei receive input from cerebellar cortex and send projection to thalamus.  Cerebellar nuclei Going from lateral to medial: 1. Dentate nucleus- largest of the cerebellar nuclei. Receives input from the Flocculonodular lateral hemisphere and carry info from the cerebral cortex. Responsible for lobe movement planning, timing, and initiation. 2. Interposed nuclei (emboliform nucleus + globose nucleus)- Receives input from the intermediate zone and cerebellar afferents that carry spinal, proximal somatosensory, auditory, and visual info. Responsible for control of distal muscles as movement progresses. 3. Fastigial nucleus- most medially located of the cerebellar nuclei. Receives input from the vermis and from cerebellar afferents that carry vestibular (CN VIII), proximal somatosensory, auditory, and visual info. Responsible for control of axial muscles as movement progresses. 4. Vestibular nuclei- located outside of the cerebellum, in the medulla. Receives input from the flocculonodular lobe. Responsible for control of balance and postural reflexes, head position, and clear vision with movement. Remember, information from here travels via cerebellar peduncles! Cerebellum- Anatomy & Functional Areas Three functional units: 1. Flocculonodular lobe (vestibulocerebellum) involved in the control of posture and eye (paravermis) movements 2. Vermis + intermediate part of the hemisphere or paravermis (together known as the spinocerebellum)- coordination of motor movements and maintenance of muscle tone. ▪ Vermis coordinates the movements of the central body (e.g. trunk, head, proximal limbs). ▪ Paravermis coordinates movement from the distal limbs (e.g. arms, legs, fingers, toes). 3. Lateral part of the hemisphere (cerebrocerebellum) (excludes vermis/ paravermis) involved in coordination and planning of limb movements (in conjunction with the basal ganglia) The lateral part of the hemisphere (cerebrocerebellum) involved in the coordination and planning of limb movements (in conjunction with the basal ganglia). The medial aspect known as the vermis coordinates axial muscles (trunk). 1. Vermis – body posture maintenance 2. Paravermal region – general body movement (e.g., walking) 3. Lateral hemisphere – fine limb movement  (With associated nuclei) (Cerebrocerebellum) Projects from the Cerebellular Cortex to the Deep Brain Nuclei Deep Cerebellular Projects from cerebellular Nucleus portions of 1. Fastigial Vermis 2. Globose Intermediate Zone (medial part of 3. Emboliform hemispheres) 4. Dentate Lateral Hemispheres Note: Globose and Emboliform nuclei are collectively referred to as interpositus.(from intermediate zone). Note that the floccular-nodular lobe projects upon the vestibular nuclei (in the medulla) The outer layer of the cerebellum is called the cortex and is folded into many wrinkles called folia. The cortex of cerebellum consists of 3 layers: Molecular layer- Lie just below the meninges. Mostly occupied by the dendrites of the Purkinje cells. Also houses stellate cells and basket cells (inhibitory interneurons). Purkinje layer- lies between the molecular and granular layers. Thinnest layer of the cortex. Contains the cell bodies of the Purkinje cells that are multipolar neurons and are the largest neurons of the CNS- inhibitory neurons. Axons serve as the sole efferent output from the cerebellar cortex that project through white matter to synapse on neurons in the deep cerebellar nuclei. Granular layer (deepest and thickest layer closest to white matter) contain cell bodies of the granular cells (the only excitatory neurons of the cerebellar cortex). Vestibular pathway and the cerebellum (1) Vestibular afferents (Vestibular branch of CN VIII) synapse with sensory neurons in the vestibular nuclei (2a) the major integrating center for equilibrium in the pons and medulla. The vestibular nuclei also receives input from the eyes and proprioceptors in the neck and limb muscles. Integrates information from vestibular, visual, and somatic receptors and then sends commands to the nuclei of CN III, IV, and VI- controls coupled eye movements to help maintain focus on the visual field. (2b) Remaining axons enter the cerebellum through the inferior cerebellar peduncles. The vestibulospinal tract conveys impulses down the spinal cord to maintain muscle tone in skeletal muscle to help maintain equilibrium. The vestibular nuclei sending impulses to the ventroposterior nucleus (VPN) in the thalamus. (3) From the VPN, the nerve impulses are sent to the vestibular area in the cortex- provides us with conscious awareness of the position and movements of the head and limbs. Damage to the cerebellum Any Questions?