The chemical control of the brain

Dr.Francois Kouya

Function of the hypothalamus

• The hypothalamus integrates somatic and visceral responses in accordance with the need of the brain.

• The hypothalamus regulates the homeostasis (exemple: body temperature and blood composition in response to changes in the external environment)

The secretory hypothalamus

• The hypothalamus controls almost all secretions of the pituitary.

• The posterior lobe is controlled by nerve fibers that originate in hypothalamic neurons

• The anterior is controlled lobe by substances that are transported from the hypothalamus by tiny blood vessels.

Hormones

• Hormones are chemicals released by cells that affect cells in other parts of the body.

• Only a small amount of hormone is required to alter cell metabolism.

• It is essentially a chemical messenger that transports a signal from one cell to another

Endocrine and exocrine hormones

• Endocrine hormone molecules are secreted directly into the bloodstream

• Exocrine hormones (or ectohormones) are secreted directly into a duct, and from the duct they either flow into the bloodstream or they flow from cell to cell by diffusion in a process known as paracrine signalling

Hypothalamic Potentiation of Someof the Major Pituitary Hormonesand the Organs They Affect in the

Endocrine System

Hypothalamus and the pituitary gland

Anterior Pituitary Hormones Parvocellular Neurosecretory cells

• Adrenocorticotrophic Hormone (ACTH)

• Thyroid-Stimulating Hormone (TSH)

or thyrotropin

• Luteinising Hormone (LH) • Follicle-Stimulating Hormone (FSH)

• Prolactin (PRL)

• Growth Hormone (GH)

• Melanocyte-Stimulating Hormone (MSH

Parvocellular neurosecretory cells

Magnocellular neurosecretory cellsOxytocin

Affects uterine contractions in pregnancy and birth and subsequent release of breast milk

Vasopressin (ADH)

Controls the blood fluid and mineral levels in the body by affecting water retention by the kidneys. This hormone is also known as arginine vasopressin (AVP)

Vasopressin and Renin

Hormones under control of piututary

• Cortisol:Adrenals

• Thyroxine: Thyroid

• Estrogen: Ovaries

• Progesterone: Ovaries

• Testosterone:Testes

Cortisol:Adrenals

• Promotes normal metabolism

• Maintains blood sugar levels and blood pressure

• Provides resistance to stress and acts as an anti-inflammatory agent.

• Regulates fluid balance in the body.

Thyroxine: Thyroid

• Controls many body functions, including:

• Heart rate

• Temperature and metabolism.

• It also plays a role in the metabolism of calcium in the body

Estrogen: Ovaries

• Facilitates growth of the tissues of the sex organs and other tissues related to reproduction.

• Estrogen also acts to strengthen bones and has a protective effect on the heart.

Progesterone: Ovaries

• Promotes the changes in the uterus that occur in preparation for the implantation of a fertilized ovum.

• Prepares the breasts for milk production

Testosterone:Testes

• Testosterone is responsible for the characteristics of the masculine body

• Hair growth on the face and body and muscle development.

• Testosterone is essential for the production or sperm and also acts to strengthen bones

Stress response: The hypothalamus pituitary and adrenals axis)

External stress triggers CRH secretion by the hypothalamus.

In turn, this signals to the pituitary to release ACTH which stimulates the adrenal gland to release cortisol.

Cortisol binds to the glucocorticoid receptor ® in the pituitary and has a negative feedback effect on the release of CRH and ACTH.

In addition, the cortisol-receptor complex has a positive feedback effect, promoting further receptor synthesis.

Psychoactive drugs

Effects of psychoactive drugs

LSD = Lysergic acid diethylamide

Psychoactive drugs are chemical substances that affect the brain functioning, causing changes in behavior, mood and consciousness

Stimulants

• Stimulants are a class of psychoactive drug that tend to increase activity in the brain.

• These drugs can temporarily elevate alertness, mood and awareness.

• While some stimulant drugs are legal and widely used, all can be addicting.

• Drugs that are classed as stimulants include caffeine, nicotine, cocaine, amphetamines and some prescription drugs.

Depressants

• Depressants are drugs that inhibit the function of the central nervous system and are among the most widely used drugs in the world: alcohol, barbiturates and benzodiazepines

Psychedelics • Psychedelic drugs, or hallucinogens, are psychoactive drugs

that affect thinking, alter moods and distort perceptions.

• Drugs that are classed as psychedelics include marijuana, LSD, psilocybin (derived from a type of mushroom) and mescaline (found in the peyote cactus)

Facts:Peyote is a small, spineless cactus, Lophophora williamsii,whose principal active ingredient is the hallucinogenmescaline. From earliest recorded time, peyote has been usedby natives in northern Mexico and the southwestern UnitedStates as a part of traditional religious rites. Mescaline can beextracted from peyote or produced synthetically

Psychoactive drugs use by school-age adolescents, Brazil