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Organizing the Brain: From Brainstem to Basal Ganglia

Explore the structure and function of the brain, from the brainstem to the basal ganglia. Learn about key structures, such as the midbrain, thalamus, hypothalamus, and more.

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Organizing the Brain: From Brainstem to Basal Ganglia

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  1. We have considered the spinal cord and the PNS…so

  2. …to the brain! Many ways to organize the brain Here’s a good one!

  3. How about this one?

  4. Let’s start with this one. Brainstem Midbrain Basal Forebrain Thalamus, hypothalamus, Basal ganglia, limbic system Cerebral Cortex

  5. BRAINSTEM/ HINDBRAIN A “Mid-sagital view” MAJOR STRUCTURES- Medulla Oblongata Cerebellum and Pons “The Reticular Formation” (sometimes called the reticular activating system)

  6. functions of the Medulla Oblongata- focus on the Vagus nerve.. • All parasympathetic tone • HR • Temp • BP • Etc

  7. Brainstem:The “Reticular activating system” Many tiny brain nuclei collectively involved in modulation of arousal brain nuclei- refers to organized groupings of neuron cell bodies

  8. Representative Nuclei of The RAS- the Locus Coereleus The LC Projects to cerebral cortex- critical in cognitive orienting Projects – a term referring to the connection path of axons from one nuclei to other brain nuclei

  9. RAS- the Raphe Nucleus Raphe Nucleus – High in Serotonin (5HT) involved in Modulation of mood, sleep states, dreaming…SSRIs primary site of action.

  10. BRAINSTEM-Pons and Cerebellum • In general the cerebellum acts to produce automatic coordination of behavior and behavioral sequences.

  11. Midbrain Major structures of interest: Substantia nigra- high Dopamine (DA) content- critical in voluntary movement Peri-aqueductal grey (PAG) - high in endorphin content- modulation of pain Ventral tegmental area (VTA)- high in DA content- critical in “wanting/cravings” components of behavior

  12. Midbrain- The ventral tegmental area (VTA)

  13. VTA to Nucleus Accumbens: The Mesolimbic Dopamine pathway-Wanting or “reward?”

  14. Basal Forebrain Structures Thalamus and Hypothalamus (Diencephalon)

  15. The Thalamus The thalamus relays sensory information from sense organs to the cerebral cortex

  16. The Hypothalamus Rostral and slightly inferior to the thalamus. - Involved in modulation of the 4 F’s Fighting Fleeing (flight) Feeding Mating

  17. BASAL FOREBRAIN • Basal Ganglia- important for initiation and control of stereotyped/automatic behaviors like walking , arm movements etc… • Neostriatum • Globus Pallidus ( GLOB-us PAL-i-dos) • Substantia nigra • …? Isn’t this part of the midbrain? • Yes, but is functionally part of the basal • ganglia

  18. Nigro-striatal Dopamine system The substantia nigra projects to the striatum

  19. Damage to the Nigro-striatal DA system? • Parkinsons’- progress cell death/loss in the substantia nigra Slowness of movement (bradykinesia) Shuffling gait Stiffness (rigidity) Tremor Loss of balance (postural instability) Speech and facial expression

  20. Typical Parkinsons’ MOST DIFFICULT SYMPTOM- Difficulty in initiation and/or changing of behavior For this reason we can think of the nigro-striatal DA pathway to NORMALLY be critical for….. Behavior initiation, the green light system, the behavioral “grease.”

  21. **of interest?? TREMORS AT REST • <object style="height: 344px; width: 425px"><param name="movie" value="http://www.youtube.com/v/gboQaXv9CuM"><param name="allowFullScreen" value="true"><param name="allowScriptAccess" value="always"><embed src="http://www.youtube.com/v/gboQaXv9CuM" type="application/x-shockwave-flash" allowfullscreen="true" allowScriptAccess="always" width="425" height="344"></object>

  22. Basal Ganglia- The Globus Pallidus When things go wrong in the Globus pallidus ?? Critical for inhibiting stray/unauthorized behaviors • Huntington's Chorea- uncontrollable continuous snake-like, dance-like writhing movements, involving the entire body

  23. Huntington's Chorea is principally characterized by hyperkinesias - abnormal, purposeless, involuntary motor movements that can occur spontaneously or only when the patient is trying to do something. These movements may be repetitive or non-repetitive.

  24. When things go wrong in the Globus pallidus ?? Tourettes Syndrome- Tics TS usually becomes apparent in children between ages 2 to 15, with approximately 50% of patients affected by age 7. The age of symptom onset is typically before the age of 18. TS is more frequent in males than females by a ratio of about 3 or 4 to 1. The disorder is thought to affect 0.1% to 1.0% of individuals in the general population.

  25. Tourettes Syndrome • TS usually becomes apparent in children between ages 2 to 15, with approximately 50% of patients affected by age 7. The age of symptom onset is typically before the age of 18. TS is more frequent in males than females by a ratio of about 3 or 4 to 1. The disorder is thought to affect 0.1% to 1.0% of individuals in the general population.

  26. Tourettes • Motor ticsInitially, patients develop sudden, rapid, recurrent, involuntary movements (motor tics), particularly of the head and facial area. At symptom onset, motor tics usually consist of abrupt, brief, isolated movements known as simple motor tics, such as repeated eye blinking or facial twitching. Simple motor tics may also include repeated neck stretching, head jerking, or shoulder shrugging. Less commonly, motor tics are more "coordinated," with distinct movements involving several muscle groups, such as repetitive squatting, skipping, or hopping. These tics, referred to as complex motor tics, may also include repetitive touching of others, deep knee bending, jumping, smelling of objects, hand gesturing, head shaking, leg kicking, or turning in a circle. In addition to affecting the head and facial area, motor tics also affect other parts of the body, such as the shoulders, torso, arms, and legs. The anatomical locations of motor tics may change over time. Rarely, motor tics evolve to include behaviors that may result in self-injury, such as excessive scratching and lip biting.

  27. Vocal tics • Vocal tics are sudden, involuntary, recurrent, often relatively loud vocalizations. Vocal tics usually begin as single, simple sounds that may eventually progress to involve more complex phrases and vocalizations. For example, patients may initially develop simple vocal tics, including grunting, throat clearing, sighing, barking, hissing, sniffing, tongue clicking, or snorting. Complex vocal tics may involve repeating certain phrases or words out of context, one's own words or sounds (palilalia), or the last words or phrases spoken by others (echolalia). Rarely, there may be involuntary, explosive cursing or compulsive utterance of obscene words or phrases (coprolalia).

  28. Other Basal Ganglia related disorders Balisms

  29. LIMBIC SYSTEM • Interconnected • Affective impulses • low consciousness • Reciprocally connected with frontal cortex • Many structures • Hippocampus • Amygdala • Nucleus accumbens

  30. View of some limbic system structures

  31. Hippocampus (seahorse?) Based on early neuroanatomical observations and studies with psychoactive drugs, the septohippocampal circuit has been proposed as a model for anxiety disorders. Note*-Memory processes can be profoundly affected by life experiences. In particular, stress has proved to be a major modulator of memory function.1–4

  32. Hippocampus and Memory: “H.M.” Henry Gustav Molaison, lost completely the ability to form new memories following a radical surgical procedure to treat his severe and intractable epilepsy. 1953; William Scoville,  a neurosurgeon removed both of H.M.'s hippocampi in their entirety, together with some of the surrounding structures. profound anterograde and retrograde amnesia H.M.'s amnesia was so severe that he never recognized Dr. Brenda Milner, despite working with her for more than 50 years.

  33. View of some limbic system structures

  34. The Amygdala receives input from many other brain areas that would logically allow evaluation of emotional significance of experiences

  35. CORTEX

  36. CEREBRAL CORTEX • Wrinkled • Thin • Layered • Interconnected • Plastic ( consider vs brainstem)

  37. Cortical hemispheres

  38. Corpus collosum

  39. Functional asymmetries?Roughly 90% of right handers, and 70% of left handers

  40. Assertions based on data Left hemisphere- analytical, rational, verbal, reading, writing ,math Right Hemisphere- Intuitive, feeling, spatial processing, nonverbal, music

  41. LOBES- gyri and sulci

  42. OCCIPITAL LOBEprimary visual processing-

  43. Temporal Lobes

  44. Parietal Lobes

  45. Parietal Lobe

  46. Primary Somatosensory CtxThe sensory homunculus The “post central gyrus”

  47. Somatosagnosias-perception of reality depends on CTX Unilateral neglect anosagnosias

  48. RX for Phantom limb- awareness arises from cortex independently of reality.

  49. FRONTAL LOBES

  50. Primary motor cortex-precentral gyrusmore later

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