Ok…to the brain! Gross Anatomy of the brain: Many ways to organize the CNS

Ok…to the brain! Gross Anatomy of the brain:

Many ways to organize the CNS

Here’s a good one!

BRAINSTEM/ HINDBRAIN

Bainstem (Medulla) critical functions

• Ascending and Descending Fiber Tracts

• All parasympathetic tone– HR

• Temp• BP• Etc

Brainstem:The “Reticular activating system”

Many tiny brain nuclei collectively involved in modulation of arousal; The reticular formation is a comprehensive network of nerves that is found in the central area of the brainstem. The functions of the formation involve many of the essential functions of the body, such as the ability to obtain recuperative sleep, sexual arousal, and the ability to focus on tasks without being easily distracted. All in all, reticular formation function is believed by some researchers to be involved with at least 25 behaviors and functions that are considered essential for the health and continued existence of each individual.

The RAS- Locus Coereleus

RAS- the Raphe Nucleus

Raphe Nucleus – High in Serotonin (5HT)Modulation of mood, sleep states, dreaming

BRAINSTEM-Pons and Cerebellum

Behavioral Functions of the Cerebellum

• Direction

• Amplitude

• Force

• Timing– Posture– Motor learning/speech

Midbrain

Major structures of interest:Substantia nigra- projects to striatum (high Dopamine (DA) content)

Peri-aqueductal grey- modulation of pain

Ventral tegmental area- projects to nucleus accumbens ( high in DA content)

Midbrain-

The ventral tegmental area

(VTA)

VTA to Nucleus Accumbens: The Mesolimbic Dopamine pathway

Diencephalon

Thalamus, Hypothalamus and Pituitary gland

The Thalamus

Relays sensory information to the cortex

The Hypothalamus

-rostral and slightly inferior to the thalamus.

- Involved in modulation of the 4 F’s

Forebrain

• (Telencephalon)– Cortex

• Basal ganglia• Limbic System

Basal Ganglia

• Neostriatum– Caudate nucleus and putamen

• Globus Pallidus

• Substantia nigra

Nigro-striatal system

The substantia nigra sends DA axons to the striatum

Nigro-striatal CCT Functions

• Parkinsons’ Slowness of movement (bradykinesia)

Stiffness (rigidity)

Tremor

Loss of balance (postural instability)

Speech and facial expression

**Difficulty in initiating Movement

GLOBUS PALLIDUS

Striatal-Pallidal CCT functions?

• Huntingtons

• Tourettes’ -

Tourettes• Tourette syndrome (TS) is a neurological disorder characterized by

repetitive, stereotyped, involuntary movements and vocalizations called tics. The early symptoms of TS are almost always noticed first in childhood, with the average onset between the ages of 7 and 10 years. TS occurs in people from all ethnic groups; males are affected about three to four times more often than females. It is estimated that 200,000 Americans have the most severe form of TS, and as many as one in 100 exhibit milder and less complex symptoms such as chronic motor or vocal tics or transient tics of childhood. Although TS can be a chronic condition with symptoms lasting a lifetime, most people with the condition experience their worst symptoms in their early teens, with improvement occurring in the late teens and continuing into adulthood.

• Tics are classified as either simple or complex. Simple motor tics are sudden, brief, repetitive movements that involve a limited number of muscle groups. Some of the more common simple tics include eye blinking and other vision irregularities, facial grimacing, shoulder shrugging, and head or shoulder jerking. Simple vocalizations might include repetitive throat-clearing, sniffing, or grunting sounds. Complex tics are distinct, coordinated patterns of movements involving several muscle groups. Complex motor tics might include facial grimacing combined with a head twist and a shoulder shrug. Other complex motor tics may actually appear purposeful, including sniffing or touching objects, hopping, jumping, bending, or twisting. Simple vocal tics may include throat-clearing, sniffing/snorting, grunting, or barking. More complex vocal tics include words or phrases. Perhaps the most dramatic and disabling tics include motor movements that result in self-harm such as punching oneself in the face or vocal tics including coprolalia (uttering swear words) or echolalia (repeating the words or phrases of others). Most patients experience peak tic severity before the mid-teen years with improvement for the majority of patients in the late teen years and early adulthood. Approximately 10 percent of those affected have a progressive or disabling course that lasts into adulthood.

• Tics are involuntary. They are brief, repetitive movements, which are either motor such as blinking or head jerking, or vocal such as

throat clearing.

LIMBIC SYSTEM

• Basal forebrain• Affective responses• Impulsive…low consciousness

– Many structures• Amygdala• Hippocampus• Septum/ nucleus accumbens- will be discussed later

Amygdala: general emotional significance of environmental stimuli

– evaluate the significance of stimuli and generate emotional responses

– generate hormonal secretions and autonomic reactions that accompany strong emotions

CEREBRAL CORTEX

• Wrinkled

• Thin

• Layered

• Interconnected

• Plastic

Major regions of CTX

Corpus collosum

Hemispheres

Almost all of Right handers and about 70% of left handers show these kinds of

functional asymmetries

LOBES

OCCIPITAL LOBE

The primary Visual Cortex

-functional blindness

-Visual agnosias

TEMPORAL LOBES

Temporal lobe damage may result in any number of problems

including any of these syndromes

Functional deafness-Anomias

-Aprosodia-Werniches’ syndrome

Parietal Lobes

Primary somatosensory cortex

The sensory homunculus and somatotopic organization

Primary somatosensory cortex damage may produce

-somatasagnosias-neglect

-anosagnosia

FRONTAL LOBES

1st -Frontal lobes and speech

Broca’s aphasiaWerniche’s aphasia (temporal lobe to

frontal lobe circuits)

What about the rest of the frontal lobe?-Phineas Gage

rod

Brain-Based Theory of Emotions• Frontal lobes

– influence people’s conscious emotional feelings and ability to act in planned ways based on feelings (e.g., effects of prefrontal lobotomy)

– Some scientists contend that the prefrontal cortex normally acts as a brake that can suppress urges or impulses by communicating with other brain areas that mediate fear and aggression, such as the amygdala.

ParietalFrontal

Occipital

Temporal

General frontal Lobe functionsAwareness

Judgment , planning and anticipation

Personality

Conscious emotions

Organization and mental flexibility

Attention and concentration

Initiation and inhibition of behavior