The XII Cranial Nerves

The 12 Good Old Cranial Nerves That Every Pre-Med Has To Memorize

On Old Olympus Towering Top, A Fin A German Viewed A Hop

• I: Olfactory
• II: Optic
• III: Oculomotor
• IV: Trochlear
• V: Trigemina
• VI: Abducens
• VII: Facial
• VIII: Auditory (Vestibulocochlear)
• IX: Glossopharyngeal
• X: Vagus
• XI: Accessory 
• XII: Hypoglossal  

Some of you may have trouble remembering the order of the cranial nerves even with the help of this mnemonic, this is how I customize mine.

The first one is Olfactory because your nose at the front of your face, and then the eyes is behind (Optic), and then the nerves to control eye ball movement is behind the eye (Oculomotor), and another one (Trochlear).

Functions of the Hypothalamus

The Specific functions of the regions in the Hypothalamus

The Hypothalamus is located under the thalamus (thus the name), and is probably one of the most important region in the brain that helps maintain homeostasis in the body. It can be divided into 3 different regions:

Lateral Hypothalamus --- the hunger centre, it has special receptors thought to detect when the body needs more food or fluids. Stimulation in this region and trigger eating and drinking response. Lab mice with lesion in this region will starve to death if not force fed, because they cannot sense hunger.

Ventromedial Hypothalamus --- the "satiety centre". It is the region that senses fullness and stops you from eating. Lab mice with lesion in this region will become very obese, because they don't know when to stop eating.

Anterior Hypothalamus --- the sex centre. When this region is stimulated in the lab animals they will have sex with just anything they encounter

Last but not least, the Hypothalamus can also be stimulated in a danger or stress situation and initiate a "fight-or-flight" response by releasing corticotropin releasing hormone (CRF) to the anterior pituitary gland, which will release Adrenalcorticotropic hormone (ACTH) to the adrenal medulla to release epinephrine and norepinephrine to further stimulate the sympathetic nervous system)

Mnemonics:

Function 4Fs

• Feed
• Fight
• Flight
• Fuck

Region specific functions:

• Destruction of the Lateral Hypothalamus (LH), one will Lack Hunger
• Destruction of the VentroMedial Hypothalamus (VMH), one will be Very Much Hungry
• Destruction of the Anterior Hypothalamus, one will be Asexual 

Functions of the Three Corticosteroids

What are the functions of the 3 corticosteroids?

The Adrenal Cortex produces three different kinds of corticosteroids:

Mineralocorticoids --- responsible for salt and water homeostasis. Aldosterone is a mineralocorticoid that can increase sodium reabsorption in the nephron, and can lead to increase in blood pressure. Aldosterone can also increase Potassium excretion through kidney.

Glucocorticoids --- regulates glucose levels, they also affect protein metabolism. The glucocorticoid most likely to appear on the MCAT is Cortisol which can raise blood glucose level by increasing gluconeogenesis and decreasing protein synthesis.

Cortical sex hormones ---Just as it sounds, cortical sex hormones (androgen and estrogen) affects the maturation of sex organs. A female fetus born with ambiguous or masculinized genital can be due to the presence of excess androgen.

Mnemonics:

3S's

• Salt (mineralocorticoids)
• Sugar (glucocorticoids)
• Sex (cortical sex hormones)

Hormones of the Anterior Pituitary Gland

What are the hormones of the Anterior Pituitary Gland? And which are tropic hormones and which are direct hormones?

FLAT PEG

• Follicle Stimulating Hormone (FSH) --- Gonads
• Luteinizing hormone (LH) --- Gonads
• Adrenocorticotropic hormone (ACTH) --- Adrenal Cortex
• Thyroid-stimulating hormone (TSH) --- Thyroid

• Prolactin --- Breast
• Endorphine --- Brain       
• Growth Hormone (GH) --- Bones and Muscles

The first four are tropic hormones that act on another endocrine gland to control release of hormones that will stimulate the target tissues. The last three acts directly on target tissues and are direct hormones.

The Three Primary Germ Layers

What do the primary germ layers give rise to?

Germ layer is a primary layer of cells that form during embryogenesis, each layer will eventually give rise to systems, tissues and organs as the embryo grows.

Ectoderm is the outer most layer and gives rise to the integument including hair, nails and epidermis, and the epithelial of the nose, mouth and the sense of the eye, the nervous system and inner ear)

Mesoderm is the middle layer and it forms the musculoskeletal, circulatory and most of the excretory systems. Mesoderm also develops into  gonads and the muscular and connective tissue in the digestive and respiratory system

Endoderm is the inner layer, which will eventually develop into the epithelia linings of the digestive and respiratory tracts including the lungs. It also forms the pancreas, thyroid, bladder and distal urinary tracts. Finally it will also form parts of the liver as well.

Mnemonics:

• Ectoderm - "attracto" derm (things that attract us to others, such as cosmetic features and "intelligence")
• Mesoderm - "means" oderm (the means of getting around as an organism, such as bones and muscle; the means of getting around in the body, such as the circulatory system; the means of really getting around, such as the gonads)
• Endoderm - linings of "endernal" organs (the digestive and respiratory tract, and accessory organs attached to these systems)

Pathway of sperm in male reproductive system

SEVE(N) UP

• Seminiferous tubules
• Epididymis
• Vas deferens
• Ejaculatory duct
• (Nothing)
• Urethra
• Penis