Physiology II -- (Part 2) Limbic System

What is the complicated entire neuronal circuitry that controls emotional behavior and motivation?

Limbic System

Why is the limbic system described as the border structures?

Separate deeper regions from cortex & cortical association areas

What are 3 important functional anatomy divisions of the limbic system?

1) Hypothalamus

2) Hippocampus

3) Amygdala

What is the control headquarters for the limbic system, endocrine system, and autonomic (vegetative) control?

Hypothalamus

What is involved in 2-way communication with all other regions of the limbic system? What 3 places does this send outputs?

Hypothalamus

Outputs

- Reticular area (autonomics)

- Thalamus & cortex

- Pituitary Gland

Stimulation of the lateral hypothalamus causes what to occur? What is strong stimulation associated with?

Urge to eat/drink

-- strong stimulation associated with rage

When there is a lesion to the lateral hypothalamus, what is the affect?

No urge to eat/drink

- Loss of drive

Stimulation of the ventromedial nucleus of the hypothalamus causes what to two effects to occur?

1) Relaxation

2) Feeling of fullness

Where then is a lesion to the ventromedial nucleus of the hypothalamus, what two things are the affect?

1) Excessive eating & drinking

2) Easily agitated

Stimulation of the periventricular nuclei of the hypothalamus causes what two effects to occur?

1) Fear

2) Shame

What two areas of the hypothalamus are part of the reward center?

1) Lateral Nuclei

2) Ventromedial Nuclei

When it comes to the reward centers of the hypothalamus, a weak stimuli will give a sense of ________, while the strong stimuli will give a sense of ________.

Weak stimuli = Reward

Strong stimuli = Punishment

What two areas are part of the punishment centers?

1) Central gray area surrounding aqueduct of Sylvius (midbrain)

2) Periventricular zone of hypothalamus

Signs of displeasure, fear, terror, pain, and physical illness are signs what area has been stimulated?

Punishment centers stimulated

What affects most of the decisions we make?

Anticipated reward vs punishment

What role does reward/punishment have on memory & learning?

If reward/punishment centers not activated, experience hardly remembered at all

What part of the limbic system originated as part of the olfactory cortex and is key for receiving sensory information related to emotion & survival (food, danger, mating) and HEAVILY involved in fear responses?

Amygdala

What are the abundant connections between the amygdala and the hypothalamus?

Stria terminalis

The hypothalamus connects with what area of the brain stem for autonomic functions?

Reticular area

INCREASED arterial pressure and heart rate in cardiovascular regulation by the hypothalamus is due to stimulation of what areas? Where is this transmitted?

Stimulation of: Lateral and posterior hypothalamus

- Transmitted through vasomotor center (upper medulla)

DECREASED arterial pressure and heart rate in cardiovascular regulation by the hypothalamus is due to stimulation of what areas? Where does this signal get transmitted?

Stimulation of Preoptic area of hypothalamus

- Transmitted through vasomotor center (lower medulla)

INCREASED temperature of blood by the hypothalamus is stimulated by what? Does this increase or decrease activity?

Preoptic Area of hypothalamus

Increase temperature = increase activity

What is the mechanism by the hypothalamus to cool down (2)? Is this via parasympathetic or sympathetic regulation?

via Sympathetic

- 1) peripheral vasodilation

- 2) sweating

DECREASED temperature of blood by the hypothalamus is stimulated by what? Does this increase or decrease activity?

Preoptic area of hypothalamus

Decrease temperature = decreased activity

What is the mechanism by the hypothalamus to warm up? (3)

1) Peripheral vasoconstriction

2) Thyroid hormone

3) Shivering

Stimulation of what part of the hypothalamus stimulates the sensation to drink for body water regulation?

Lateral hypothalamus

- stimulates thirst center

Stimulation of what part of the hypothalamus stimulates the increased reabsorption of H2O in the kidneys for body water regulation? What hormone does this stimulate in turn?

Supraoptic Nucleus of Hypothalamus

-- which stimulates post. pituitary to secrete ADH (antidiuretic hormone)

Osmoreceptors sense increase concentrations in what? These receptors will project to what nucleus in hypothalamus?

Osmoreceptors sense increased Na+ concentration

- Project to supraoptic nucleus (which trigger ADH release by post pituitary)

Stimulation of what part of the hypothalamus stimulates the increase in desire to each/search for food? What is the hormone stimulating this part of the hypothalamus in this situation?

Lateral Hypothalamus

- Ghrelin (hunger hormone --> empty stomach)

Stimulation of what part of the hypothalamus decreases the desire to eat/search for food? What 3 things are stimulating this part of the hypothalamus in this situation?

Ventromedial nucleus

1 - Leptin (increase fat storage)

2 - Insulin (increase glucose levels in blood)

3 - Vagus nerve (stretch in stomach/GI)

What hormone increases hunger? What hormone decreases hunger?

Increase = Ghrelin (like a Gremlin)

Decrease = Leptin

What function of the hypothalamus is possible due to the relationship between the hypothalamus and pituitary gland?

Endocrine function

What part of the pituitary gland is controlled by HORMONES released into the blood by the hypothalamus?

Anterior Pituitary

What part of the pituitary gland is controlled NEUROLOGICALLY by the hypothalamus? What 2 neuropeptides (hormones) are released by this part of the posterior pituitary glands?

Posterior Pituitary (neurohypophysis)

1) Oxytocin

2) Anti-diuretic hormone (ADH)

What is the HPA axis?

hypothalamic-pituitary-adrenal axis

What is the master regulator of homeostasis with endocrine and autonomic control?

Hypothalamus

What is the master endocrine gland that gets direct control by the hypothalamus (CRH)?

Pituitary Gland

How many hormones does Pituitary gland release? What is an example of one that acts on the adrenal glands?

9 hormones

- ex: Adrenocorticotropin (ACTH)

What are the stress response glands that are stimulated by ACTH? What hormone does this release?

Adrenal Gland

-- releases cortisol (aka Glucocorticoids; aka stress hormone)

The adrenal cortex produces what three hormones?

1) Glucocorticoids (ex: cortisol)

2) Mineralocorticoids

3) Androgens

The medulla of the adrenal glands releases what hormones?

Catecholamines (Epinephrine & Norepinephrine)

What region of the adrenal cortex produces cortisol?

Zona fasciculata

What is required by our body during times of stress?

Energy

Cortisol upregulates alpha-1 adrenergic receptors to cause what 4 effects on the body?

1) Stimulate gluconeogenesis --> AA to glucose, decreased in muscle

2) Decreased glucose utilization --> insulin resistance & increase blood glucose

3) Mobilization of free fatty acids

4) Decreased inflammation --> immune conseaquence

Cortisol levels are ______ the normal after injury after only 4-20 minutes?

6x

What are 5 other stressors that can stimulate cortisol release?

1) infection

2) intense temperatures

3) surgery

4) restraining

5) mental stress

How are cortisol levels measured? When are they highest? Lowest?

Measured in blood or saliva

- Highest in morning (5-25 mcg/dL)

- Lowest at night (<10 mcg/dL)

Why does cortisol cause immune consequences?

Anti-inflammatory properties which will block (decrease) early signs of inflammation

(such as inflammatory signaling, capillary permeability, migration/phagocytosis of WBCs, lymphocyte proliferation, and IL-1/fever)

How is cortisol pharmacologically important?

Useful for significant reducing overactive immune system (ex: autoimmune disease/hypersensitivities)

What are some side effects of cortisol?

Increased blood clotting, AVN, osteoporosis, tendon rupture

NOTE: long list of potential side effects