Brain Anatomy And Physiology

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Brain Anatomy and physiology

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Frontal Cortex

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- Also known as the frontal lobe of the brain

- Especially important for planning appropriate behavioral responses to external and internal stimuli

- Integrates complex perceptual information from sensory and motor cortices as well as from the parietal and temporal association cortices to perform cognitive tasks

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Frontal Cortex injury

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Impairment in planning (executive function)
Altered initiative
“Personality" change
Reduced creativity

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Frontal Cortex psychiatric diagnoses

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• Schizophrenia
• Depression
• Obsessive-compulsivedisorder (OCD)

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Midbrain

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- Rostral part of the brain stem

- Smallest part of the brain
- Connects the thalamus and cerebral cortex with the pons and cerebellum
- Mainly comprised of:
• Tectum
• Tegmentum
• Ventral Tegmentum
• Cerebral Peduncles

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Brain Stem

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- Includes the medulla oblongata, pons and the midbrain

- Spinal cord - continuation of the brain stem
- Controls most of the functions necessary to maintain life, e.g. heart rate, blood pressure,
respiration rate etc.
- Pivotal in maintaining consciousness and regulating the sleep cycle

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Brain Stem Diagram

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Midbrain Functions

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- Conduction of nerve impulse
- Involves in functions such as vision, hearing, eye movement and body movement
- Controls balance and animal awareness

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Midbrain Structures

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- Red nucleus – origin of rubrospinal tract

- Deals with automatic associated reflexes
- Substantia nigra (a.k.a. “Black Matter”)
– associated with Parkinson’s disease in
human and yellow star thistle in horses
- Cerebral peduncles – rope-liked stalks
that appear at the base of telencephalon
- The only part of the brain that carries
melanin pigment

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Clinical cases associated with mid-brain damage

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Yellow star thistle poisoning

Symptoms

- Inabilityto swallow, eat and drink
- Drowsiness
- Makingchewing motions with nothing in the mouth
- Frequent yawning
- Unusual behavior, including standing in unusual positions
- Acting as though something is caught in his throat
- Chewing food and spitting it out

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The limbic system

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is a complex set of structures that lies on
both sides of the thalamus, just under the cerebrum

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Limbic system components

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- hypothalamus,

- the hippocampus,
- the amygdala,

And several related areas like:
- cingulate gyrus
- ventral tegmental area
- basal ganglia

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Limbic system Functions

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The limbic system supports a variety of functions including adrenaline flow, emotion, behavior, motivation, long-term memory, and olfaction. Emotional life is largely housed in the limbic system, and it has a great deal to do with the formation of memories

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Limbic system Diagram

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Hypothalamus

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- Mainly concerned with homeostasis.

- Responsible for regulating hunger, thirst, response to pain, levels of pleasure, anger and aggressive behavior, and more.
- It also regulates pulse, blood pressure, breathing, and arousal in response to emotional
circumstances.

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Hippocampus

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- The hippocampus consists of two “horns” that curve back from theamygdala.

- Very important in converting things that are “in your mind” at the moment (in short-term memory) into things that you will remember for the long run (long-term memory)

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Hippocampus diagram

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Hippocampus damaged

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If the hippocampus is damaged, a person cannot build new memories, and lives instead in a strange world where everything he/she experiences just fades away-while older memories from the time before the damage are untouched

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Amygdala

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- The amygdala, deep in the temporal lobe, is a very important link in the limbic system.

- The amygdala connects with the hippocampus. These connections enable it to play an important role in the mediation and control of major activities like friendship, love, fear and affection and on the expression of mood.

- Damage to amygdala disrupts emotional reactions (as reported in monkeys), these and makes them social outcasts.

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Amygdala in Animals

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- When it is stimulated electrically,

animals respond with aggression.
- If the amygdala is removed, animals
get very tame and no longer respond
to things that would have caused rage
before.
- Also when removed, animals also
become indifferent to stimuli that
would have otherwise have caused
fear and even sexual responses.

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Amygdala diagram

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Other components of the limbic system

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The cingulate gyrus: is responsible for focusing
attention on emotionally significant events, and
for associating memories to smells and to pain

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Other components of the limbic system

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The ventral tegmental area

People with damage here tend to have difficulty getting pleasure in life, and often turn to alcohol, drugs, sweets, and gambling.

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ventral tegmental area diagram

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Other components of the limbic system

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The basal ganglia. They are responsible for
repetitive behaviors, reward experiences, and
focusing attention.

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Other components of the limbic system

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Though, the prefrontal cortex is involved in
thinking about the future, making plans, and
taking action, it also appears to be involved in the same dopamine pathways as the ventral tegmental area, and plays a part in pleasure and addiction.

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additional facts about the limbic system

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- Sometimes referred to as the “emotional brain

- The same structures found in the human limbic system can also be found in the brains of evolutionary ancient animals such as the alligator.
- In the alligator, the limbic system is heavily
involved in smell and plays an important role in defending territory, hunting and eating prey.

- In humans, the limbic system is more involved in motivation and emotional behaviors.
- Stimulation of the lateral hypothalamus in cat leads to hissing, spitting and claw extension.
• Lesions of the lateral hypothalamus leads to placidity/tranquility.
• Lesions of the medial hypothalamus makes the cat highly excitable and easily triggered into aggression.

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autonomic nervous system

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The (ANS), also known as the visceral nervous system and involuntary nervous system — is a division of the peripheral nervous system that functions as a control system (largely below the level of consciousness) over the function of internal organs. These functions include influencing heart rate, digestion, respiratory rate, salivation, perspiration, pupillary dilation, urination, sexual arousal, breathing and swallowing.

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The autonomic nervous system has two branches

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the parasympathetic nervous system (PSNS), and the sympathetic nervous system (SNS). The sympathetic nervous system is often considered the "fight or flight" system, while the parasympathetic nervous system is often considered the "rest and digest" or "feed and breed" system. In many cases, PSNS and SNS have "opposite" actions where one system activates a physiological response and the other inhibits it

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Autonomic Nervous System diagram

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