We have considered the spinal cord and the PNS…so

We have considered the spinal cord and the PNS…so

…to the brain! Many ways to organize the brain

Here’s a good one!

How about this one?

Let’s start with this one.

Brainstem

Midbrain

Basal Forebrain

Thalamus, hypothalamus, Basal ganglia, limbic system

Cerebral Cortex

BRAINSTEM/ HINDBRAIN

MAJOR STRUCTURES-

Medulla Oblongata

Cerebellum and Pons

“The Reticular Formation” (sometimes called the reticular activating system)

A “Mid-sagital view”

functions of the Medulla Oblongata- focus on the Vagus nerve..

• All parasympathetic tone– HR

• Temp

• BP

• Etc

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

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

RAS- the Raphe Nucleus

Raphe Nucleus – High in Serotonin (5HT)

involved in Modulation of mood, sleep states, dreaming…SSRIs primary site of action.

BRAINSTEM-Pons and Cerebellum

In general the cerebellum acts to produce automatic coordination of behavior and behavioral sequences.

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

Midbrain-

The ventral tegmental area

(VTA)

VTA to Nucleus Accumbens: The Mesolimbic Dopamine pathway-

Wanting or “reward?”

Basal Forebrain Structures

Thalamus and Hypothalamus (Diencephalon)

The Thalamus

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

The Hypothalamus

Rostral and slightly inferior to the thalamus.

- Involved in modulation of the 4 F’s

Fighting

Fleeing (flight)

Feeding

Mating

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

Nigro-striatal Dopamine system

The substantia nigra projects to the striatum

• 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

Damage to the Nigro-striatal DA system?

Typical Parkinsons’

MOST DIFFICULT SYMPTOM-

Difficulty in initiation and/or changing of behaviorFor 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.”

**of interest?? TREMORS AT REST

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When things go wrong in the Globus pallidus ??

• Huntington's Chorea- uncontrollable continuous snake-like, dance-like writhing movements, involving the entire body

Basal Ganglia- The Globus Pallidus

Critical for inhibiting stray/unauthorized behaviors

• 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.

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.

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.

Tourettes• Motor tics

Initially, 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.

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).

Other Basal Ganglia related disorders

Balisms

LIMBIC SYSTEM

• Interconnected• Affective impulses• low consciousness• Reciprocally connected with frontal cortex

– Many structures• Hippocampus• Amygdala• Nucleus accumbens

View of some limbic system structures

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

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.

profound anterograde and retrograde amnesia

1953; William Scoville,  a neurosurgeon removed both of H.M.'s hippocampi in their entirety, together with some of the surrounding structures.

H.M.'s amnesia was so severe that he never recognized Dr. Brenda Milner, despite working with her for more than 50 years.

View of some limbic system structures

The Amygdala receives input from many other brain areas that would logically allow evaluation of

emotional significance of experiences

CORTEX

CEREBRAL CORTEX

• Wrinkled

• Thin

• Layered

• Interconnected• Plastic ( consider vs brainstem)

Cortical hemispheres

Corpus collosum

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

Assertions based on data

Left hemisphere- analytical, rational, verbal, reading, writing ,mathRight Hemisphere- Intuitive, feeling, spatial processing, nonverbal, music

LOBES- gyri and sulci

OCCIPITAL LOBEprimary visual processing-

Temporal Lobes

Primary auditory cortex

Hearing Understanding language

(receptive language) Higher visual processing

Parietal Lobes

Parietal Lobe

Primary somatosensory cortex Visuo-spatial processing

Primary Somatosensory CtxThe sensory homunculus

The “post central gyrus”

Somatosagnosias-perception of reality depends on CTX

Unilateral neglectanosagnosias

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

FRONTAL LOBES

Primary motor cortex-precentral gyrus

more later

Frontal Lobe functionsVolitional behavior

Speech

Inhibition of impulses

Self-control/temptationsSelf-initiative

Planning/anticipation

Self-monitoring

Awareness (abilities and limitations)

Attention

Mental flexibility

Problem solving

Complex Judgments/goal setting

Source monitoring

Self-identity

Copying

Working memory

Temporal memory-sequencing

Emotion

Suppression of Impulses

• Some scientists contend that the prefrontal cortex normally acts to suppress or act upon urges or impulses perhaps by communicating with other brain areas that mediate fear and aggression, such as the amygdala.