Rotator Cuff

The four muscles that make up the rotator cuff are supraspinatus, infraspinatus, teres minor, and subscapularis. Subscapularis inserts on the lesser tubercle of the humerus while the other three muscles insert onto the greater tubercle.

It is believed that swimmer's shoulder is caused by the impingement of the tendon of the supraspinatus muscle as it passes through the subacromial space. This also makes the supraspinatus more suspectible to tear.

Thanks to Honglin!

Acetylcholine

Unlike dopamine, there is an increase in acetylcholine in Parkinson's disease. This neurotransmitter is synthesized in the basal nucleus of Meynert (basal forebrain). In the autonomic nervous system, it serves as the neurotransmitter for sweat glands and adrenal medulla. In the peripheral nervous system, acetylcholine plays a role in skeletal muscle activation, specifically between the motor nerve and skeletal muscle. In the central nervous system it is involved in alertness, attention, and learning. Acetylcholine receptors are classified as either nicotinic or muscarinic.

Other disorders involving acetylcholine include Myasthenia gravis and Alzheimer's disease.

1. Myasthenia gravis
In Myasthenia gravis, the body produces antibodies against acetylcholine nicotinic receptors, inhibiting proper acetylcholine signal transduction. As a result, the patient suffers from weakness and fatigue.

2. Alzheimer's disease
In Alzheimer's disease, plaques are formed in the brain. The plaque lead to cell death and decreased levels of the acetylcholine in the cerebral cortex and caudate nucleus. Treatment of Alzheimer's include acetylcholinesterase inhibitors, which prevent the breakdown of acetylcholine to make up for the lack of neurotransmitter.

Dopamine

Parkinson's Disease is a neurological disorder marked by tremors, stiffness and decreased movement. The main pathological characteristic is cell death in the substantia nigra (specficially the pars compacta), where dopamine is produced. Dopamine is a neurotransmitter that is responsible for movement and emotional responses. It also acts in regulating the rewards and pleasure centers of the brain. Therefore decrease in dopamine would result in less movement. A lack of dopamine also affects the basal ganglia, a group of nuclei at the base of the forebrain. The basal ganglia are involved in voluntary motor control, habit learning, eye movements, and cognitive and emotional functions.

Decreased levels of dopamine are also seen in depression, while increased levels are seen in schizophrenia (difficulty distinguishing reality from imagination) and Huntington Disease (chorea and dystonia).

Thiamine Deficiency

Thiamine (Vitamin B1), like all vitamin B molecules, are water soluble. So our bodies need to be constantly resupplied with Vitamin B. A deficiency can lead to health problems such as Beriberi and Korsakoff's syndrome.

1. Beriberi
Vitamin B1 acts as a coenzyme in carbohydrate metabolism and in pentose phosphate pathway. Without it, the body cannot properly extract energy from food. Pyruvic acid builds up and causes loss of mental awareness, difficulty breathing, and heart problems.

2. Korsakoff's Syndrome
Korsakoff's syndrome is more common among alcoholics. Like with Beriberi, the brain needs to be able to extract energy from carbohydrates. Without enough energy, the brain cannot properly function. This can lead to degeneration of mammillary bodies or disruptions in signal pathways. As a result, a patient may experience memory loss and confabulation.

Anemia

Anemia is when you have a lack of red blood cells or hemoglobin. A patient can be diagnosed with anemia based on their CBC. We would look specifically at the hematocrit (concentration of red blood cells and concentration of hemoglobin).

We cannot depend on O2 saturation (SpO2) because that reading could still be high in an anemic patient. SpO2 is only an indication of how much of the patient's hemoglobin is carrying oxygen. Even though the patient may have less hemoglobin, the hemoglobin can still be working at full capacity. A low SpO2 (lower than 90%) is called hypoxemia.

Thanks to Jose!

Cataracts

A cataract is a condition in which the lens of the eye become cloudy.

Why is diabetes a risk factor for cataract formation?

The eye contains an anterior and posterior chamber filled with aqueous humor. Aqueous humor contains glucose. If there is a high level of glucose, a lot of it gets converted into sorbitol. The sorbitol collects in the lens and leads to cataract formation.


How do steriod medications lead to cataracts?

Steriods are used as inflammatory medication for conditions like asthma. However they can cause osmotic movement of water into the lens, leading to swelling and opacity. Steriods can also denature the proteins within the eye, leading to opacification.

Thanks to Danny!

DiGeorge Syndrome

For DiGeorge's Syndrome, remember CATCH22!

C - Cardiac defects
A - Abnormal facies
T - Thymic hypoplasia
C - Cleft palate
H - Hypocalcemia
22 - Chromosome 22 mutation

Now why would a mutation on chromosome 22 lead to thymic hypoplasia? Well chromosome 22 is responsible for the development of the thymus from the third and fourth pharyngeal pouches. No thymus, no T-cell formation. No T cells, immunodeficiency.

Thanks to my friends: Tomasz, Danny, and Joy!