Menstrual Cycle explanation

This animation video explains the biological processes of Menstruation and the physiology of Menstrual Cycle

Wound Healing Phases

A video showing the phases of normal wound healing

Skeletal System Structures and Functions

An overview of the functions and structures of the skeletal system.

Neural transmission in the nodes of Ranvier

The nodes of Ranvier increase the efficiency of neural transmission by means of which of the following?

• a.Decelerating the closing of Na -gated channels
• b.Enhancing myelination of the internodal segment
• c.Sequestration of Na entry into the axon
• d.Multiple firings due to local ionic currents around the node
• e.Decreasing threshold for the action potential

 The answer is  (c ).

The nodes of Ranvier increase the efficiency of nodal conduction because of restriction (sequestration) of energy–dependent Na influx to the node. The nodes of Ranvier represent
the space between adjacent units of myelination.
This area is bare in the CNS, whereas in the PNS the axons in the nodes are partially covered by the cytoplasmic tongues of adjacent Schwann cells. Most of the Na -gated channels are located in the bare areas. Therefore, spread of depolarization from the nodal region along the axon occurs until it reaches the next node.
This is often described as a series of jumps from node to node, or saltatory conduction.

Bilirubin metabolism made simple

A medical student teaching video on heme catabolism, bilirubin metabolism in the liver. Particularly useful in understanding the difference between direct and indirect bilirubin and why they differ in hemolytic anemias

The Physiology of Stress

The Stress Response:
In stress (as in threatening situations that we are unable to cope with) messages are carried along neurones from the cerebral cortex (where the thought processes occur) and the limbic system to the Hypothalamus.

The Anterior Hypothalamus produces sympathetic arousal of the Autonomic Nervous System (ANS). The ANS is an automatic system that controls the heart, lungs, stomach, blood vessels and glands. Due to its action we do not need to make any conscious effort to regulate our breathing or heart beat. The ANS consists of : the sympathetic nervous system and the parasympathetic nervous system. Essentially, the parasympathetic nervous system conserves energy levels. It increases bodily secretions such as tears, gastric acids, mucus and saliva which help to defend the body and help digestion. Chemically, the parasympathetic system sends its messages by a neurotransmitter acetylcholine which is stored at nerve endings.

Unlike the parasympathetic nervous system which aids relaxation, the sympathetic nervous system prepares the body for action. In a stressful situation, it quickly does the following:

* Increases strength of skeletal muscles
* Decreases blood clotting time
* Increases heart rate
* Increases sugar and fat levels
* Reduces intestinal movement
* Inhibits tears, digestive secretions.
* Relaxes the bladder
* Dilates pupils
* Increases perspiration
* Increases mental activity
* Inhibits erection/vaginal lubrication
* Constricts most blood vessels but dilates those in heart/leg/arm muscles

The main sympathetic neurotransmitter is noradrenaline which is released a the nerve endings. The stress response also includes the activity of the adrenal, pituitary and thyroid glands.

The two adrenal glands are located one on top of each kidney. the adrenal medulla is connected to the sympathetic nervous system by nerves. Once the latter system is in action it instructs the adrenal medulla to produce adrenaline and noradrenaline (catecholamines) which are released into the blood supply. The adrenaline prepares the body for flight and the noradrenaline prepares the body for fight. They increase both the heart rate, and the pressure at which the blood leaves the heart; they dilate bronchial passages and dilate coronary arteries; skin blood vessels constrict and there is an increase in metabolic rate. Also gastrointestinal system activity reduces which leads to a sensation of butterflies in the stomach.

Lying close to the hypothalamus in the brain the pituitary gland. In a stressful situation, the anterior hypothalamus activates the pituitary. The pituitary releases adrenocorticotrophic hormone (ACTH) into the blood which then activates the outer part of the adrenal gland, the adrenal cortex. This then synthesises cortisol which increases arterial blood pressure, mobilises fats and glucose from the adipose (fat) tissues, reduces allergic reactions, reduces inflammation and can decrease lymphocytes that are involved in dealing with invading particles or bacteria. Consequently, increased cortisol levels over a prolonged period of time lowers the efficiency of the immune system. The adrenal cortex releases aldosterone which increases blood volume and subsequently blood pressure. Unfortunately, prolonged arousal over a period of time due to stress can lead to essential hypertension.

The pituitary also releases thyroid stimulating hormone which stimulates the thyroid gland, to secrete thyroxin. Thyroxin increases the metabolic rate, raises blood sugar levels, increases respiration/heart rate/blood pressure/and intestinal motility. Increased intestinal motility can lead to diarrhoea. (It is worth noting that an over-active thyroid gland under normal circumstances can be a major contributory factor in anxiety attacks. This would normally require medication.)

The pituitary also releases oxytocin and vasopressin which contract smooth muscles such as the blood vessels. Oxytocin causes contraction of the uterus. Vasopressin increases the permeability of the vessels to water therefore increasing blood pressure. It can lead to contraction of the intestinal musculature.

However, for many people they perceive everyday of their life as stressful. Unfortunately, the prolonged effect of the stress response is that the body's immune system is lowered and blood pressure is raised which may lead to essential hypertension and headaches. The adrenal gland may malfunction which can result in tiredness with the muscles feeling weak; digestive difficulties with a craving for sweet, starchy food; dizziness; and disturbances of sleep.

ABO Blood Types

Oxygen Transport

Fantastic Video about Auditory Transduction

This 7-minute video by Brandon Pletsch takes viewers on a step-by-step voyage through the inside of the ear, to the acoustic accompaniment of classical music.

Beta2 Adrenergic Receptor Mnemonic

Beta2 Adrenergic Autonomic Receptor of the Sympathetic Nervous System presented in a pictorial mnemonic format . Key Point: Beta2 expands. For Medical learning.

Good video explains Action Potentials

This video explains the process by which a nerve cell receives, conducts, and transmits signals.

This video is from:
Essential Cell Biology, 3rd Edition

Palato-Pharyngeal Function

Surgical patients with parts of their faces surgically removed show palato-pharyngeal functions.

SLUG BAM: Muscarinic effects of Acetylcholine

Acetylcholine acts on two vastly different classes of receptors - nicotinic receptors (with two subtypes, one at the neuromuscular junction of skeletal muscle, the other within ganglia and the CNS), and muscarinic receptors (widely distributed within both peripheral and central nervous systems).

**Muscarinic effects SLUG BAM:

• Salivation/ Secretions/ Sweating
• Lacrimation
• Urination
• Gastrointestinal upset
• Bradycardia/ Bronchoconstriction/ Bowel movement
• Abdominal cramps/ Anorexia
• Miosis

Oxygen Saturation

USMLE Catecholamine synthesis

Brainstem and Pons

The structures of the midbrain, including the medulla oblongata, the pons and associated structures and their functions.

Basic Structure of the Nephron

Complete neuron cell diagram

Neurons can respond to stimuli and conduct impulses because a membrane potential is established across the cell membrane. In other words, there is an unequal distribution of ions (charged atoms) on the two sides of a nerve cell membrane. This can be illustrated with a voltmeter:

With one electrode placed inside a neuron and the other outside, the voltmeter is 'measuring' the difference in the distribution of ions on the inside versus the outside. And, in this example, the voltmeter reads -70 mV (mV = millivolts).
In other words, the inside of the neuron is slightly negative relative to the outside. This difference is referred to as the Resting Membrane Potential

Cardiac Cycle - Systole & Diastole

Migraine Pathophysiology