wrist / endocrine / renal / balance Flashcards by Ronny Varghese

WRIST BONE

1- radius
8- carpals
5- metacarpals
14- phalanx 
28 total wrist bones

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Radius – The most proximal (to the midline of the body) part of the wrist is distal end of the radius. It articulates with all but one of the bones in a proximal row of bones called the carpals. A distal feature of the radius that is important is its widening and thickening towards the distal end, thus providing a larger surface for muscular attachments. At the distal end the radius is at least double the size as the ulna. Both the radius and ulna have defined pointy distal ends. The points are the radial and ulnar styloid processes

There are eight carpal bones, or carpi, arranged in two curved asymmetrical rows; a

(1) proximal row = scaphoid / lunate / triquetrum / pisiform,
(2) distal row = trapezium / trapezoid / capitate/ hamate

The proximal carpal row forms a sort of an arch that articulates with the radius, forming the wrist joint. The distal row forms the transition from wrist to hand.

Scaphoid – The scaphoid bone is the largest and most lateral (thumb side) of the carpals in the proximal row. It articulates with the radius proximally and with the trapezium and trapezoid bones in the distal row of carpals. The scaphoid can be palpated fairly easily. It is the bone on the lateral side of the wrist immediately distal to the end of the radius. It is flanked, to the anterior and posterior, by two tendons at the base of the thumb. Spread the fingers and lift the thumb to make the tendons prominent, then relax them in order to palpate the lateral surface of the bone. As an aside here, when the two tendons at the base of the thumb were tense and prominent, there was a small depression in between them. This little fossa is historically known as the anatomical snuff box.

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Pisiform – The pisiform is the fourth and most medial bone of the proximal row of carpals. It is a very small bone that articulates only with the triquetrum. In fact, it is classified as a sesamoid bone, situated in the ligament of the truiquetrum. The most proximal prominence is the triquetrum, the most distal and anterior (in front of the triquetrum) is the pisiform.

Trapezium – The first bone in the second (distal) row of carpals is the trapezium. It sits between the scaphoid and the base of the first metacarpal (base of the thumb). It articulates with the first and second metacarpals, scaphoid, and trapezoid bones. The anterior surface of the trapezium presents the tubercle of the trapezium, which can be palpated on the palmar side of the wrist, just proximal to the base of the thumb.

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Trapezoid – On a skeleton the trapezoid is an easy bone to identify. It is the smallest in the distal row of carpals. While easy on a skeleton, its size and location make in unpalpable on a living human. It articulates with four bones; the scaphoid and the second metacarpal along the longitudinal axis and the flanking trapezium and capitate bone.

Capitate – The capitate is the largest of all the carpal bones and physically occupies the center space of the wrist. With firm pressure applied just proximal to the posterior base of the third metacarpal (middle one), a portion of the capitate can be palpated. Aside from it being the largest, it has more articulations than all of the other carpals, having seven articulations with the surrounding bones; the scaphoid, lunate, trapezoid, hamate, and the second, third, and fourth metacarpals.

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Metacarpals – The metacarpals are the long bones of the hand running between the distal carpals and the phalanges. They form the palm and what we call the back of the hand. Their distal ends are the knuckles when we make a fist. There is a general characteristic shape to a metacarpal; concave proximal end, arched anterior surface, fairly straight posterior surface, and convex distal end (the head). The metacarpals are numbered, lateral to medial (thumb side to pinky side), from one to five. All five can be palpated from the posterior aspect

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Wrist – The wrist is the articulation of the radius, scaphoid, lunate, and triquetrum bones into a joint complex. It can also be called the radiocarpal joint. The wrist is capable of moving in two anatomical axes, the sagittal and frontal – a biaxial joint. If you consider the kinetic chain of the wrist, the wrist is an intermediary that transfers force from the hand to the radius when lifting (pulling) an object OR transfers force from the radius to the hand when pushing objects. It is important to note that those forces are also transferred, by physical necessity, to the ulna through engagement of ligamentous tissues.

The major ligaments of the wrist are the radial collateral and ulnar collateral ligaments. The radial collateral ligament lies laterally in the ligament complex and attaches to the radial styloid process and to the scaphoid bone of the proximal row of carpals. It is a ‘collateral’ ligament, so a second strand that attaches to the trapezium and base of the first metacarpal is also present. It engages to limit ulnar deviation (adduction of the hand at the wrist). The ulnar collateral ligament is medial (on the ulnar side) and the two strands attach the ulnar styloid process to the triquetrum and pisiform carpals. This particular ligament acts to limit radial deviation. Both the radial and ulnar collaterals can be palpated with firm pressure during repeated deviation/relaxation cycles. Radial deviation will reveal the ulna collateral ligament and ulnar deviation will reveal the radial collateral ligament.

Posterior aspect of the wrist there is a group of deep and unpalpable ligaments call the dorsal radiocarpal ligament. There are four defined segments of the ligament, all arising from the posterior lip of the radius just proximal to the joint. They will attach distally to the scaphoid, triquetrum, lunate, and capitate bones.

Anterior aspect of the wrist there is a group of deep and unpalpable ligaments collectively called the palmar radiocarpal ligament. There are six defined segments of the ligament, all arising from the anterior lip of the radius just proximal to the joint. They will attach distally to the scaphoid, triquetrum, lunate, and capitate bones.

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WRIST
Posterior aspect of the wrist there is a group of deep and unpalpable ligaments call the dorsal radiocarpal ligament. There are four defined segments of the ligament, all arising from the posterior lip of the radius just proximal to the joint. They will attach distally to the scaphoid, triquetrum, lunate, and capitate bones.

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Intercarpal Joints – The intercarpal joints are the articulations between the individual carpal bones. Frequently you will see the intercarpal joints referred to as one of two collections of joints within the carpus, referring to the lateral and medial attachments between adjacent carpals. Midcarpal joints would then be attachments between the proximal and distal rows of carpals. These are planar synovial joints and although capable of limited movement between the carpals, they do contribute to wrist mobility. The carpals form an arch in the tranverse plane that is concave on the palmar side through which ligaments, nerves, and blood vessels pass. The arch deepens with flexion of the wrist and flattens with extension. This is why it is important to mildly extend the wrist when palpating for a radial pulse (checking the heart rate at the wrist).

The flexor retinaculum, also known as the transverse carpal ligament crosses over the carpal bones, forming a tunnel through which tendons and nerves can pass in a protected environment. As in the similar retinaculum in the ankle, it also prevents bowstringing of the tendons during contraction. It attaches to the pisiform and the hamate (along the hamulus) on the medial side and to the scaphoid the trapezium laterally. It is contiguous with the extensor retinaculum on the dorsum of the hand.

The extensor retinaculum, also known as the dorsal carpal ligament, lies at a downward angle, lateral to medial, across the carpal bones and forms a connective tissue bridge over the extensor tendons, helping to keep the tendons in place. It has an attachment to the lateral border of the distal radius and to the triquetrum and the pisiform bones of the medial side of the wrist. You can look at the retinaculi as a guide for tendons, one that keeps them in a location that facilitates appropriate and mechanically efficient transmission of force. Combined, the flexor and extensor retinaculum form a robust band around the wrist at roughly the level of where a watch is worn.

Carpometacarpal Joints – These joints are easy to identify and describe, five of them occur where the distal row of carpals articulate with the proximal end of the metacarpals. Each such articulation is a carpometacarpal joint. A small amount of pressure on a relaxed and flexed wrist joint allows palpation on the dorsal surface of hand. There is some debate regarding the number of ligaments present and their names.

The five that seem to be most accepted are the 
1- anterior oblique 
2- ulnar collateral 
3- first intermetacarpal 
4- posterior oblique
5- dorsoradial ligaments.

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Metacarpophalangeal Joints – These are the condyloid joints or the ‘knuckles’ where the metacarpals meet the phalanges. The rounded end of the metacarpal sits in the shallow bowl of the proximal phalanx. These are biaxial joints allowing flexion, extension, abduction, and adduction of the phalanges. The exception here is the thumb which is a uniaxial joint, allowing flexion and extension. The joints are among the easiest to visualize and palpate. Simple make a fist to demonstrate the knuckles. One of the most interesting is the transverse metacarpal ligaments occurring between adjacent metacarpals (refer to Figure 16.14). These ligaments bind the heads of the metacarpals in close proximity, thus preventing excessive spreading and defining the maximum width of the distal palm. They can be palpated by gently squeezing the tissues just behind the webs between the fingers.

Interphalangeal Joints – The articulation of two sequential phalanx is an interphalangeal joint. There are two such joints in each phalange with the exception of the thumb which has but one interphalangeal joint between its proximal and distal phalanx. The interphalangeal joint closest to the metacarpals is termed the proximal interphalangeal joint. The one farthest away is the distal interphalangeal joint. Each joint can be easily identified by simple curling the fingers up making palpation elementary. Each interphalangeal joint has several ligaments surrounding it to include cruciate (cross the joints) and collateral (down the sides) ligaments.

There are a many many more small ligaments encasing the bones of the wrist, forming a network of interwoven connective tissue strands. This extensive system reinforces and holds the joints in close proximity while still allowing appropriate mobility.

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WRIST MUSCLES

In general, there are two levels of stratification used to lay out the muscles of the wrist and hand.
1- The first strata is the division of the muscles into those that arise outside of the wrist and hand, the extrinsic muscles, and those that arise and end within the wrist and hand, the intrinsic muscles.
2- The second strata is divided by function into flexors and extensors. Sometimes you will see further descriptions of these muscles as anterior/posterior or superficial/deep.

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WRIST MUSCLES

Extensor muscles are found on the medial aspect of the forearm.

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Flexor carpi radialis – The name of this muscle can provide all you need to know. It is a flexor and since flexors are anterior, it must be on the anterior of the arm near the radius. It attaches distally to the second and third carpi (carpi is plural). It is attached proximally to the medial epicondyle of the humerus, on the radial side of the arm.

The basic actions driven by contraction of the muscle are flexion of the hand and – as the muscle angles across the forearm medial to lateral – it assists in abduction of the hand. Palpation of the tendon is fairly simple, flex the wrist and look for the closest tendon to the thumb on the radial side. By following the tendon back up toward the proximal attachment on the medial ulna, about half way up the forearm the cable-like tendon becomes softer – this is the beginning of the muscle.

Palmaris longus – This is a small muscle that may actually be absent in ten percent or more of the population. It has been reported in the clinical literature that its absence does not affect wrist flexion and grip strength. An interesting finding, as flexion of the wrist is its primary function. The muscle attaches proximally to the medial epicondyle of the humerus and distally to the proximal center of the palmar aponeurosis, a fanned sheet of fascia lying across the palm into which many ligaments and tendons invest themselves (Figure 16.19). The tendon running between muscle and the aponeurosis is quite long. When the muscle contracts, the palmar fascia is tensed. The tendon can be palpated by placing the tips of the thumb and pinky together while flexing the wrist. The tendon, if the muscle is present, will present as a prominent tendon running longitudinally through the center of the superficial wrist. The palmaris longus lies immediately lateral to the flexor carpi radialis.

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Pronator quadratus – This is an anterior muscle that is not a flexor. It is, as the name implies, a pronator of the hand. It attaches along the distal aspect of the last few inches of both the radius and ulna (Figure 16.21). The direction of the fiber orientation is lateral, across the space between the two bones.

Flexor pollicus longus – Here is where the Latin nomenclature for the thumb comes into play. Pollux means thumb, so the flexor pollicis longus should be a flexor of the thumb. Attaching proximally to the upper half of the radius along with an attachment to the coronoid process of the ulna, the muscle attaches distally to the base of distal phalanx of the thumb (Figure 16.22). The muscle can be identified by palpating the lateral aspect of the upper forearm during repeated flexion/relaxation cycles of the thumb against the fore finger (pinching). The movement of the tendon and muscle should be visible and palpable.

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Flexor digitorum profundus – The name flexor digitorum profundus suggests a flexor of the fingers. The other word in the name, profundus, sounds a lot like profound. A profound thought is a deep thought. The muscle has a long proximal attachment along the ulna, spanning from near the olecranon down about two thirds its length. The distal attachments of the profundus are interesting and relatively unique. Instead of a single tendon emerging from the muscle and then dividing into slips for multiple attachments, there are four tendons that arise independently along the distal border of the muscle belly. The tendons then continue on to attach distally to the bases of the distal phalanx of digits two through five (Figure 16.22).

Extensor carpi ulnaris – This extensor attaches proximally to the humerus at the lateral epicondyle. It then runs down the medial border of the forearm where it has a considerable attachment to the ulna, crosses the wrist, and attaches distally to the base of the fifth metacarpal. This orientation also makes it an adductor of the wrist and hand. Palpation is fairly easy by finding the two attachment sites and observing/ palpating the expected line of the muscle along the forearm while performing simultaneous wrist flexion and ulnar deviation. It should be visually apparent and palpable with repeated contraction-relaxation cycles.

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Extensor digitorum – This muscle has essentially opposite actions and attachments as the flexor digitorum profundus. It too attaches proximally to the lateral epicondyle of the humerus and distally to the first phalanx of the second through fifth phalanges, but on the posterior of the hand (Figure 16.23). The tendons of this muscle are very apparent on the back of the hand and wrist during extension of the fingers.

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Extensor digiti minimi – This is a very small extensor muscle appearing slightly medial to the extensor digitorum. It attaches proximally to the lateral epicondyle of the humerus and distally to the distal phalanx of the fifth phalange (Figure 16.23). Extension of the fifth phalange will make the distal tendon prominent for palpation.

Extensor carpi radialis longus – The extensor muscles of the forearm are on the posterior or dorsal side. As seen before, carpi indicates an attachment to one or more carpal bones, radialis indicates proximity to the radius, and longus suggests a long muscle. The extensor carpi radialis longus attaches proximally to the supracondylar ridge above the lateral epicondyle of the humerus, an attachment obscured from palpation by the overlying triceps brachii. The muscle then becomes palpable as it runs parallel and inferior to the brachioradialis then attaches distally to the base of the second metacarpal (Figure 16.23). As the muscle orientation runs along the lateral aspect, it can also act as an abductor of the wrist and hand (radial deviation).

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Extensor carpi radialis brevis – The similarity of names, indicates a muscle similar to the extensor carpi radialis longus, just a shorter muscle. The major differences between the two is that much of the brevis attaches proximally below the longus – to the lower aspect of the lateral epicondyle of the humerus – and the brevis attaches distally to the base of the third metacarpal. It shares the same functions at the longus.

Abductor pollicus longus – The abductor pollicis longus is a deep muscle that runs from its proximal attachment along the mid-dorsal aspects of the radius and ulna to a distal attachment at the base of the first metacarpal (Figure 16.24). It acts as an abductor of the thumb.

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Extensor pollicus longus – The extensor pollicus longus is a deep muscle, mostly obscured from palpation by the abductor pollicus longus. It attaches proximally along the radius near the abductor pollicus longus and attaches distally to the base of the distal phalanx of the thumb. It acts to extend the distal phalanx. Its orientation also enables it to assist in wrist abduction. The tendon of the muscle can be palpated at the anatomical snuff box. It is the medial tendon bordering the depression.

IT inserts into the base of the first metacarpal, and it abducts the first metacarpal at the carpometacarpal joint

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Extensor pollicis brevis – The brevis lies below and essentially parallel to extensor pollicus longus. Its proximal attachment is just below the longus and attaches distally just short of the longus, at the base of the first phalanx of the thumb. Its function is to extend the first phalanx of the thumb. The tendon of the muscle can be palpated at the anatomical snuff box. It is the lateral tendon bordering the depression.

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Extensor indicis – The extensor indicis as suggested by the name is a posterior forearm muscle, an extensor. Indicis refers to the index finger. The muscle proximally attaches to a small area approximately three fourths the way down the ulna and attaches distally to the distal phalanx of the second phalange. It extends the index finger. The distal tendon is easy to palpate during repeated extension and relaxation of the index finger. The tendon and the movement can be followed to the muscle which should appear as the tendon crosses the wrist above phalange three.

INSTRINSIC MUSCLES

The intrinsic muscles are the

abductor pollicis brevis,
opponens pollicis,
flexor pollicis brevis,
adductor pollicis (thenar muscle) and
opponens digiti minimi,
flexor digiti minimi brevis,
abductor digiti minimi (hypothenar muscle).

-Thenar muscle is the meat of the hand below the thumb, –Hypothenar is the meat of the hand below the pinky.

Although these muscles provide fine motor control primarily, they can be developed for improved strength or endurance through appropriate exercise.

Locating the superficial flexors is a matter of finding the proximal attachment and either the distal attachment or the region through which their tendons pass. Then extending the fingers and wrist should reveal them. Even some of the underlying muscles can be localized by doing the same movement and feeling for movement or tension in their tendons.

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EXTRINSIC FLEXORS

Flexor Carpi Radialis
Palmaris longus
Flexor carpi ulnaris
Flexor digitorum superficialis
Pronator quadratus
Flexor pollicus longus
Flexor digitorum profundus

EXTRINSIC EXTENSORS

Extensor carpi ulnaris
Extensor digitorum
Extensor digiti minimi
Extensor carpi radialis longus
Extensor carpi radialis brevis
Abductor pollicus longus
Extensor pollicus longus
Extensor pollicis brevis
Extensor indicis

The joints and muscles of the hand produce the same movements as other joints, flexion, extension, abduction, adduction, rotation, and circumduction. But the sheer volume of joints working provides for exquisite control of the orientation of the hand and fingers in space.

At the wrist the movements possible are flexion, extension, adduction (ulnar deviation), abduction (radial deviation) and circumduction

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At the fingers there can be flexion at one or more joints, extension at one or more joints, adduction at the metacarpophalangeal joint, abduction at the metacarpophalangeal joint, and circumduction at the metacarpophalangeal joint.

At the thumb, a unique movement besides flexion, extension, adduction, abduction, and circumduction is possible, opposition (Figure 16.28). Opposition of the thumb is a unique ability of humans, discriminating us from other vertebrates. In opposition, the thumb is moved toward the palm to ‘oppose’ the remaining fingers. This movement allows us to pinch, grasp, and hold (wrap the hand around an object). Reposition is the opposite of opposition and is simply the return of the thumb to anatomical position. In the course of human development it has been the human ability to hold and manipulate tools that moved the human race forward.

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The newest anthropological data suggests that the human thumb arose about six million years ago, more than three million years before the earliest evidence of man-made tools. That is leading to an emerging hypothesis that intellectual development rather than physical ability drove the development of tools. This is supported by the use of a tool (a thin stick) to harvest termites from their mounds as a food source by some modern primates. An ability to use an existing tool is present in some primates, however they lack the intellectual capacity to create new tools for specific purposes.

Endocrine system produces hormones

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Endocrine glands (endo means inside) secrete or release substances that are used inside the body. These glands lack ducts, releasing their secretions directly into the surrounding tissues and blood. Those secretions, hormones, then are dissolved in the blood and are carried in the cardiovascular system to various points throughout the body.

The term ‘hormone’ was first used in 1902 by Bayliss and Starling who identified the first hormone (secretin) and its function. Hormones control or coordinate the activities of other tissues, organs, and organ systems in the body. Most hormones are composed of amino acids, the structural elements of proteins. Some hormones such as steroids have other interesting structural elements. Steroids like estrogen and testosterone are created from molecules of cholesterol produced by the liver (yes, cholesterol is a very good thing in most situations).

Although we generally associate endocrine function with glands, it doesn’t have to be a gland to be endocrine, the muscle cells of the heart produce the hormones Atrial-natriuretic peptide and brain natriuretic peptide for example.

``` Endocrine Glands • Hypothalamus – in the brain • Kidney – in the abdomen • Pituitary Gland – in the brain • Liver – in the abdomen • Pineal Body – in the brain • Stomach – in the abdomen • Thyroid – in the neck • Pancreas – in the abdomen • Parathyroid Gland – in the neck • Ovaries – female reproductive • Heart – in thoracic cavity • Testes – male reproductive • Adrenal Gland – on the kidneys • Skin ```

Hormone types; Testosterone- Promotes muscle growth (anabolic) and development of male sex characteristics; increases metabolic rate. Cortisol- Catabolic effects; increases in times of stress; associated with decreased performance. Growth hormone- Develops and enlarges all tissue types; increases protein synthesis. Insulin- Drives glucose transport into cells; anabolic. Glucagon- Drives movement of glucose into blood; catabolic. Insulin-like Growth Factor I- Mediates growth factor action; anabolic. Epinephrine - Mobilizes glycogen; increases muscle blood flow; increases cardiac contractility.

Hormones affect the functions occurring in the body in two basic ways: - Change the rate of synthesis of specific substances, such as increases in contractile protein synthesis or increased metabolic enzyme production. - Change the permeability of cell membranes. Membranes are selective barriers, allowing specific molecules to move into the cell while preventing other molecules to move out. These changes in permeability affect cell function in many important ways, since substances outside the cell are usually necessary for the modification of the environment inside the cell.

When we consider fitness and the endocrine system, training program composition affects hormone production in the body: - Frequency of workouts – Days per week - Duration of workouts – Minutes or hours of training in a session, mileage, sets, repetitions, and rest periods - Intensity of workouts – How hard the training is compared to maximal speed, weight, work output, distance or time - Exercises included – strength based, endurance based, mobility based, or multi-element

TESTOSTERONE - 50% or less intensity = no drop off in circulating testosterone, - 75% had little drop off - 100%ish = substantial drop in Test, about 10%. Changes in circulating testosterone after training are predictable and intensity dependent. It is likely that resting testosterone levels also adapt predictably to long-term training, and that these adaptations are both intensity and volume dependent. It is also apparent that the recovery of hormonal status after a workout or series of workouts is strongly associated with improved performance. Understanding that both short-term responses and long-term adaptations in testosterone levels relate to Selye’s theory – since they are an essential component of recovery processes – can help us design effective training programs without the specter of anabolic steroid use.

CORTISOL Cortisol response is trainable (see this paper supporting this assertion). After a bout of maximal exercise a novice may experience a much greater than 100% increase in blood cortisol levels, whereas maximal exercise in an elite trainee may induce as little as a 20% increase. As we progress through the training stages, novice to elite, this is one of the ways it becomes incrementally more difficult to disrupt homeostasis. Proper programming, progressive or periodized, is organized so that it disrupts homeostasis and increases cortisol levels but then facilitates a reduction in resting cortisol levels. This requires that adequate recovery be incorporated as an integral part of the program.

GROWTH HORMONE Growth hormone has numerous physiologic effects: - it increases bone growth, cartilage growth, and protein deposition in the cell and drives metabolism toward fat utilization. Studies have demonstrated that weight training induces an increase in circulating growth hormone. These changes in concentrations, and subsequent growth, can occur independent of testosterone (documented here). Concentrations change little during the first few sets of a whole-body workout composed of large-scale multi-joint exercises but increase about twelve sets into the workout. Concentrations peak about 30 minutes after the workout then return to normal approximately an hour and a half later. This data comes from an experiment using a forty-minute workout, and it is possible that longer workouts may elicit a larger or more prolonged growth hormone response. Isolation exercises targeting only one segment of the body are likely ineffective in altering growth hormone levels. Nutritional status after endurance training can affect how much growth hormone is produced during a four hour post exercise period meaning that fasting after a training session is not wise (see the data supporting this statement). Insulin

A highly anabolic hormone, insulin regulates the permeability of cell membranes and facilitates the transport of glucose and other substances into the cell. This would be an important aspect of endurance training responses and adaptation. Insulin also aids in regulation of the cell cycle (cell genesis and division) and adaptive metabolism (read this for more information). These functions are crucial for recovery from training, since depleted glucose and amino acids must be replaced and metabolic process must accommodate demand so that comprehensive recovery processes can occur. In respect to muscle mass, animal research has demonstrated that hypertrophy can proceed in the absence of insulin, so other mechanisms are also at work, but insulin remains one of the most potent, abundant, and easily manipulated anabolic hormones.

Insulin-lLike Growth Factor Little is known about this hormone, but there is a small body of evidence showing that Insulin-Like Growth Factor-1 has a strong anabolic effect. Release of this hormone has been linked to weight training in a few studies, but this finding has not been consistently demonstrated. One study has shown that bathing isolated muscle cells with IGF-1 in a Petri dish induces hypertrophy, but there is no good data showing that IGF-1 can be easily and favorably manipulated with training. It has been observed that IGF-1 is found in milk, possibly contributing to milk’s reputation as a growth food for heavy training.

Epinephrine This hormone causes an increase in the amount of blood the heart pumps each minute and promotes the breakdown of glycogen. During intense bouts of training, epinephrine concentrations can increase a dozen times over. This may help the body cope with the rapid onset of exercise both by quickly increasing blood supply to the working muscle and by helping provide a rapid energy source (glycogen → glucose → ATP). This response is transient, with exercise-induced increases returning to normal within six minutes of the cessation of exercise. The response and subsequent adaptations to exercise is also variable as genetic profile affects the magnitude of secretion at rest and during exercise (see the evidence here). Hormones do not work in isolation. With external stress such as exercise, the body will secrete epinephrine from the adrenal medulla and cortisol from the adrenal cortex, both can be considered hormones of the autonomic nervous system. Epinephrine raises our blood pressure, elevates heart rate, stimulates energy substrate delivery to the cells and induces vasoconstriction in the blood vessels in our digestive system (called “shunting”, a redirection of blood from the gut to the working muscle). Elevations in cortisol, while catabolic, indirectly helps stimulate replenishment energy stores, a benefit for long term metabolic recovery. Hormones that increase the activity of the autonomic nervous system can elevate blood glucose levels (augment delivery) and induce transient hypertension (increase ability to pump blood against resistance). Other important hormones acting in a coordinated manner during exercise are testosterone, growth hormone, triiodothyronine (T3), thyroxine (T4), epinephrine, cortisol, insulin, aldosterone and erythropoietin (aka, EPO). These all play a role in maintaining energy production and delivery to muscles during endurance exercise through mediating the metabolism of free fatty acids and carbohydrates. They also function in maintaining fluid balance and adjusting the internal environment of cells and tissues to sustain homeostasis.

In the average person this all means that the kidneys will process and filter about 50 gallons of blood a day (about 190 liters) and remove about ½ a gallon (1.9 liters) in the form of urine.

Kidneys – The kidneys are two bean shaped organs (ever heard of kidney beans?) that act as filters of blood and produce urine. They lie to the right and left of the vertebral column in the abdominal cavity approximately just below the 12th thoracic vertebra and under the diaphragm. The kidney itself is divided into two layers; the outer renal cortex and the inner renal medulla. The cortex contains the beginnings of the tiny tubular and vascular units of filtration, the glomerulus. There are about a half million glomeruli in the human kidney. The glomeruli penetrate deep into the medulla. The function of the medulla is crudely to collect the filtrate into the collecting duct which exits the kidney to the ureters.

Ureters – These are about 10–12 inch long and thin tubes leading from the kidneys down along and flanking the vertebral column to the urinary bladder. The ureter walls are lined with smooth muscle and the action of the smooth muscle actively conducts urine produced in the kidneys to its temporary storage in the urinary bladder.

Urinary Bladder – The urinary bladder the point of urinary collection before urine is disposed of by urination. The bladder is a hollow muscular sac. It is quite distensible and can hold up to approximately 350–500 ml (12–16 ounces) of urine. The bladder sits on the pelvic floor, generally lying between the rectum and the pubic symphysis. As the bladder fills, a muscle, the detrusor muscle is stretched and stimulates a reflex to cause contraction of the detrusor muscle, the first step of urination (Think about how this might contribute to the sensation of discomfort when you have to “hold it”). Before urine can be expelled, two sphincter muscles, the involuntarily controlled internal sphincter and the voluntarily controlled external sphincter, must be relaxed. Once the sphincters have relaxed urine exits the bladder to the urethra.

Urethra – The urethra is a tube that conducts urine from the urinary bladder to the external environment. It is approximately 2 inches (5 cm) in length in females and approximately 8 inches (20 cm) in length in males. There is a urethral sphincter that allows further voluntary control over urination.

The kidneys serve several essential regulatory functions in humans. - Elimination of nitrogenous wastes (nitrogen containing molecules like ammonia and urea) and other toxic materials from the body. - Reabsorption of glucose and amino acids for re-use within the body. - Production of hormones (erythropoietin – red blood cell production, renin – blood pressure regulation, calcitrol – vitamin D metabolism). - Maintenance of the water, electrolyte and acids/base balance.

wrist / endocrine / renal / balance Flashcards

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