Human Physiology Ch 11 -16 Final Review

ATP Production in Skeletal Muscle.

Skeletal muscle fibers have three ways to produce ATP: 1) Creatine Phosphate, an energy rich molecule that is found in muscle fibers. Creatine + ATP = Creatine phosphate + ADP 2) Anaerobic glycolysis is the entire process by which the breakdown of glucose gives rise to lactic acid when oxygen is absent or at low concentrations. 3) Aerobic respiration, a series of oxygen-requiring reactions of the Krebs cycle and the electrical transport chain. It is slower that anaerobic glycolysis, but it yields more ATP.

ACHE - Acetylcholinesterase

The effect of ACh binding to its receptor. It lasts only briefly because ACh is rapidly broken down.

The Heart Secretes Atrial Natriuretic Peptide

The heart produces the hormone atrial natriuretic peptide (ANP), which inhibits reabsorption of Na+ ions and water by the kidneys so more is lost into the urine. These actions increase exertion of Na+ in urine and increases urine output, which decreases blood volume and blood pressure.

Water-Soluble Hormones

1) Amine Hormones are synthesized by modifying certain amino acids. The catecholamines - epinephrine, norepinephrine, and dopamine - are amine hormones derived from the amino acid tyrosine. Melatonin is an amine hormone derived from the amino acid tryptophan. 2) Peptide/Protein Hormones are amino acid polymers. Most hormones belong in the category.

Functional Syncytium

Because cardiac muscle fibers are electrically coupled by gap junctions, when an action potential is generated in a mass of cardiac muscle fibers, it quickly spreads to all of the muscle fibers in that mass and then the muscle fibers contract together. Such a mass unit or functional syncytium. The atria and ventricles of the heart behave as two distinct functional syncytium.

Lower Motor Neuron

Because somatic motor neurons have their cell bodies in lower parts of the CNS they are known as lower motor neurons. From the brain stem, axons of lower motor neurons extend through cranial nerves to innervate skeletal muscles of the face and head. From the spinal cord, axons of lower motor neurons extend through spinal nerves to innervate skeletal muscles of the limbs and trunk. Only lower motor neurons provide output from the CNS to skeletal muscle fibers. For this reason, they are also called the final common pathway.

Hyperplasia

Increase in number of fibers. Occurs via cell division, and can occur in limited types of cell muscle.

Slow-Wave Potentials

Slow-wave potentials are cycles of alternating repolarization that do not necessarily reach threshold. Sometimes threshold is reached and an action potential is generated; on other occasions, threshold is not reached and an action potential is does not occur.

Smooth Muscle Activity

Smooth muscle activity is regulated by a variety of factors, some of which are excitatory (promotes contraction), and others that are inhibitory (promotes relaxation). All of these factors ultimately affect smooth muscle activity by modifying the concentration of Ca2+ in the sarcoplasm of the smooth muscle fiber.

Pacemaker Cells

Smooth muscle have pacemaker cells. They do not need the nervous system.

Smooth Muscle

Smooth muscle is found in the walls of hollow organs and tubes, where it contracts to move substances through the interior spaces of these structures. Of the three types of muscle, smooth muscle is the most variable because it has such a wide range of properties.

Neuromuscular Junction (NMJ)

The NMJ is the site where a somatic motor neuron communicates with a skeletal muscle fiber. At the NMJ, a terminal branch of the somatic motor neuron's axon divides into a cluster of synaptic end bulbs, which contain synaptic vesicles. Inside each synaptic vesicle are thousands of molecules of acetylcholine (ACh), the neurotransmitter released at the NMJ. ACh has an excitatory effect on the NMJ, ultimately causing the skeletal muscle fiber to contract. The region at the end bulbs is called the motor end plate. A neuromuscular junction includes all of the synaptic end bulbs on one side of the synaptic cleft, the synaptic cleft itself, plus the motor end plate of the muscle fiber on the other side. A skeletal muscle fiber has only one NMJ and it is usually located near the midpoint of the fiber.

Somatic Nervous System

The SNS innervates the skeletal muscles of the body. When a somatic motor neuron stimulates a skeletal muscle, it contracts. If somatic motor neurons cease to stimulate a skeletal muscle, the result is a paralyzed, limp muscle that has no muscle tone. The SNS usually operates under voluntary control. It isn't always though. The somatic motor neurons that innervate skeletal muscles involved in posture, balance, breathing, and somatic reflexes (such as the flexor reflex) are involuntarily controlled by integrating centers in the brain stem and spinal cord.

Glucose

The body prefers glucose as an energy source because we have the enzymes to break it down. It takes the least amount of effort. You do have the ability to break down proteins and amino acids if needed though.

Thyroid Gland

The butterfly shaped thyroid gland is located just below the larynx. Thyroid hormone contains iodine. T3 - 3 iodine, T4 - 4 iodine.

The Cardiovascular System

The cardiovascular system consists of the heart, blood vessels, and blood.

Raynaud Phenomenon

The digits (fingers and toes) become ischemic after exposure to cold or with emotional stress. The condition is due to excessive sympathetic stimulation of smooth muscle in the arterioles of the digits and heightened response to stimuli that causes vasoconstriction.

Ovaries and Testes

The female gonads, the ovaries, are paired oval structures located in the female pelvis cavity. They produce several steroid hormones, including two estrogens, and progesterone. These female sex hormones, along with FSH and LH from the anterior pituitary, regulate menstrual cycle and maintain pregnancy. In addition to estrogen and progesterone, the ovaries produce the hormones inhibin and relaxin. Inhibin inhibits the secretion of FSH. Relaxin inhibits contractions of the uterus, making it easier for a fertilized egg to implant in the uterine wall. The male gonads, the testes, are oval glands located in the scrotum. The main hormone produced and secreted by the testes is the androgen testosterone. Testosterone

Chromaffin Cells

The hormone producing cells, called chromaffin cells, are innervated by sympathetic preganglion neurons of the ANS. Because that ANS exerts direct control over the chromaffin cells, hormone release can happen very quickly. The chromaffin cells of the adrenal medulla secrete unever amounts of epinephrine and norepinephrine. About 80% epinephrine, and 20% norepinephrine. These two hormones greatly augment the fight or flight response of the sympathetic nervous system.

Cholecalciferol

The skin produces cholecalciferol, or vitamin D3, a substance that plays a role in the synthesis of calcitriol - the active form of vitamin D.

Each pancreatic islet contains four types of hormone secreting cells:

1) Alpha cells constitute about 17% of pancreatic islets cells and secrete glucagon. 2) Beta cells constitute about 70% of pancreatic islet cells and secrete insulin. 3) Delta cells constitute about 7% of pancreatic islet cells and secrete pancreatic polypeptide. 4) F cells constitute the remainder of pancreatic islet cells and secrete pancreatic polypeptide. The interactions of the four pancreatic hormones are complex and not completely understood. What is known is the glucagon raises the blood glucose level, and insulin lowers it. Somatostatin acts in a paracrine manner to inhibit the insulin and glucagon release from neighboring beta and alpha cells. It may also act as a circulating hormone to slow absorption of nutrients from the GI tract. In addition, pancreatic polypeptide somatostatin inhibits the secretion, gallbladder contraction and secretion of digestive enzymes by the pancreas.

An increase in Ca2+ concentration in the sarcoplasm of a smooth muscle fiber causes contraction in the following way:

1) Ca2+ binds to calmodulin, a regulatory protein in the sarcoplasm that is similar in structure to troponin. 2) The Ca2+ -calmodulin complex activates an enzyme called myosin light chain kinase (MLCK), which is also present in the sarcoplasm. 3) Activated MLCK in turn phosphorylates (adds a phosphate group to) light chains in the myosin heads. 4) The phosphorylated myosin heads bind to actin, and muscle contraction begins. Therefore, contractions in smooth muscle is triggered by calcium-induced changes in thick filaments, whereas contraction in striated muscle is triggered by calcium-induced changes in the thin filaments. Contraction of smooth muscle starts more slowly and lasts much longer than contraction of striated muscle.

Three Types of Muscle Proteins

1) Contractile Proteins, which generate force during contraction. Two contractile proteins are actin and myosin, which are the main components to thick and thin filaments. Myosin makes up the thick filament. A myosin molecule consists of a tail and two myosin heads, which bind to myosin-binding sites on actin molecules of the thin filament during muscle contraction. Actin is the main component of the thin filament. Each actin molecule has a myosin-binding site to which a myosin head of a thick filament binds during muscle contraction. 2) Regulatory Proteins, which help switch the contraction process on and off. Tropomyosin is a component of the thin filament. In a relaxed skeletal muscle fiber, tropomyosin covers the myosin-binding sites on actin molecules, preventing myosin from binding to actin. Troponin is a component of a thin filament. When Ca ions bind to troponin, troponin undergoes a conformational change that moves tropomyosin away from myosin-binding sites on actin molecules, and muscle contraction subsequently begins as myosin binds to actin. 3) Structural Proteins , which keep the thick and thin filaments in the proper alignment, give the myofibril extensibility and elasticity, and link the myofibrils to the sarcolemma and extracellular matrix. Titin connects to a Z disc to the M line of the sarcomere, helping to stabilize the position of the thick filament. Because it can stretch and then spring back unharmed, titin accounts for much of the elasticity and extensibility of myofibrils. a-Actinin is a structural protein of a Z disc that attaches to actin molecules of thin filaments and the titin molecules. Myomesin forms the M line of the sarcomere; it binds the titin molecules and connects adjacent think filaments to one another. Nebulin wraps around the entire length of each thin filament; it helps anchor the thin filaments to the Z discs and regulates the length of the thin filaments during development. Dystrophin links the thin filaments of the sarcomere to the integral membrane proteins in the sarcolemma, which are attached in turn to proteins in the connective tissue matrix that surrounds muscle fibers. It is thought that dystrophin helps reinforce the sarcolemma and helps transmit tension generated by sarcomeres to tendons.

The Heart has Four Chambers

2 Upper Chambers: Atria 2 Lower Chambers: Ventricles The left side of the heart is responsible for systematic circulation (higher pressure = 100) The right side of the heart is responsible for pulmonary circulation and always pumps under low pressure. The two sides of the heart are always in sync.

Somatic Motor Neuron

A motor unit is comprised of a somatic motor neuron and its muscle fibers. A single somatic motor neuron innervates several muscle fibers, but each muscle fiber is innervated by only one somatic motor neuron. A motor unit consists of a somatic motor neuron plus all the muscle fibers it innervates.

Pacemaker Potential

A spontaneous depolarization that always reaches threshold and therefore triggers the production of an action potential. After repolarization, the pacemaker potential starts to develop again and the cycle repeats.

Tetanic Contraction

A sustained muscle contraction evoked when the motor nerve that innervates a skeletal muscle emits a high action potentials at a very high rate.

Twitch

A twitch is a brief period contraction of a group of muscle fibers within a muscle in response to a single action potential. Twitches can last anywhere from 20 to 200 msec. This is very long compared to the brief 1-2 msec. that a muscle action potential lasts. It consists of three sequential phases: 1) The Latent period lasts about 2 msec. It is a brief delay that occurs between application of the stimulus and the beginning of the contraction. 2) The Contraction Period lasts 10-100 msec. Ca binds to troponin, myosin-binding sites on actin are exposed, and myosin crossbridges form. As a result, peak tension develops in the muscle fiber. 3)The Relaxation Period also lasts 10-100 msec. Ca is actively transported back into the sarcoplasmic reticulum, myosin-binding sites are covered by tropomyosin, myosin heads detach from actin, and tension in the muscle fiber decreases. The actual duration of these periods depends on the type of skeletal muscle fiber.

The Stress Response

Also know as General Adaptation Syndrome (GAS). This is how the body adapts to stress and is controlled mainly by the hypothalamus. The stress response occurs in 3 stages: 1) Initial Fight-or-flight response is initiated by action potentials from the hypothalamus to the sympathetic division of the autonomic nervous system (ANS), including the adrenal medulla. 2) a slower resistance reaction is initiated by action potentials from the hypothalamus, the resistance reaction is a longer-lasting response initiated in large part by hypothalamic releasing hormones. 3) Exhaustion happens when the bodies resources have become depleted.

Metabolism

Also known as Basal metabolic rate. It is the rate of energy expenditure under standard or basal conditions. When BMR increases, so does cellular metabolism of carbohydrates, lipids, and proteins.

Synaptic Cleft

Although the synaptic end bulbs and motor end plate are close to each other, they do not actually touch; instead, they are separated by a small space called the synaptic cleft.

Plateau Potential

Calcium gives a plateau potential in cardiac muscles. During this time, they cannot be overstimulated.

Cardiac Muscle

Cardiac muscle is found only in the heart, where it forms the bulk of the heart wall. They are branched and usually have only one centrally located nucleus. Like skeletal muscle fibers, they are striated due to the presence pf repeating sarcomeres consisting of thick and thin filaments that have regular pattern of overlap. Cardiac muscle fibers rely almost exclusively on aerobic respiration to generate the ATP they need for muscle contraction. As a result, these fibers contain large numbers of mitochondria.

Direct Motor Pathways

Direct motor pathways conduct action potentials for voluntary control of skeletal muscles of the body.

Endocrine Glands / System

Endocrine glands are ductless glands that secrete hormones that are carried by the blood to distant target cells. All endocrine glands and hormone secreting cells constitute the endocrine system. The endocrine system is hard to measure, only produces hormones as needed, and consists of all glands, organs, and tissues that contain hormone-secreting cells.

Eustress and Destress

Eustress prepares us to meet certain challenges and thus is helpful. Distress is a harmful stress. Any stimulus that produces a stress response is a stressor.

Central Fatigue

Even before actual muscle fatigue occurs, a person may have feelings of tiredness and the desire to cease activity. It is caused by changes to the central nervous system. Although the exact mechanism is unknown, fatigue may be a protective mechanism to stop a person from exercising before muscles become damaged. When you work skeletal muscles, you damage them, this is why you need recovery time.

Multiunit Fibers

Fibers that act independently of each other as multiple units. Gap junctions are rare in multi-unit smooth muscle. As a result, fibers have to be stimulated individually by nerves to contract. Multi-unit smooth muscle is found in the airways to the lungs, the iris and ciliary body of the eye, the arrector pili muscles of the skin, and some blood vessels. Compared to single unit smooth muscle, multi-unit smooth muscle has a richer supply of ANS nerve endings.

Single Unit Fibers

Fibers that contract together as one. It is also referred to as visceral smooth muscle because it is found in the walls of viscera (internal organs) such as the stomach, intestines, uterus, urinary bladder, and many blood vessels. Like cardiac muscle, single-unit smooth muscle is autorhythmic and behaves as a functional syncytium,

Glycogen

Glycogen performs functions that oppose that actions of insulin. Hence, most of these functions promote catabolism, the breakdown of larger molecules into smaller molecules. Glucagon has functions that are antagonistic to those of insulin: 1) Breakdown of glycogen 2) Formation of glucose from noncarbohydrate sources. 3) Breakdown of lipids. 4) Inhibition of protein synthesis. Gluconeogenesis- to make new glucose.

Graded Contraction

Graded contractions can occur in skeletal muscle. Graded contractions are contractions that very in strength depending on how much force is needed by the muscle to support a particular object.

Receptors

Hormones influence their target cells by influencing a specific protein. The binding of hormones to their receptors cause the target cells to produce cellular response, such as cell growth, protein synthesis, secretion, muscle contraction, or transport of substances across the cell membrane.

Tension

How we can measure the maximum work a muscle can do.

Down Regulation

If a hormone is present in excess, the number of target-cell receptors may decrease.

Dehydroepiandrosterone (DHEA)

In both males and females, the adrenal cortex secretes small amounts of weak androgens. The major androgens secreted by the adrenal gland is DHEA.

Dense Bodies

In smooth muscle fibers, the thin filaments attach to structures called dense bodies, which are functionally similar to Z discs in the striated muscle fibers. Some dense bodies are dispersed throughout the sarcoplasm; others are attached to the sarcolemma.

In both the pulmonary and systematic circuits, blood is carried away from and then returned the heart in the flowing way:

Large vessels called arteries carry blood away from the heart. Arteries branch to form smaller vessels called arterioles. Arterioles give rise to even smaller vessels called capillaries. From capillaries, blood enters larger vessels called venules. Venules give rise to even larger vessels called veins, which carry blood back to the heart. Capillaries are the smallest blood vessels of the body; they serve as the sites of gas exchange between blood and surrounding tissues.

Central Pattern Generators (CPGs)

Local circuit neurons also play a major role in locomotion (walking and running). The spinal cord contains networks of local circuit neurons called central pattern generators, which are responsible for the rhythmic movements (alternating flexion and extension) of the limbs that occur during locomotion. CPGs coordinate the output of the lower motor neurons that control the muscles of the limbs while the body is walking or running. Once locomotion begins, the CPGs sustain limb movements on their own without any additional input from higher centers in the brain.

Muscle Tone

Muscle tone is established by different motor units that are alternatively active and inactive. Even at rest, a skeletal muscle exhibits muscle tone, a small amount of tautness or tension in the muscle due to weak, involuntary contractions of its motor units. When the motor neurons serving a skeletal muscle are damaged or cut, the muscle becomes flaccid, a state of limpness in which muscle tone is lost.

Oxygen Debt

Oxygen consumption increases for a while after exercise. Oxygen debt refers to the added oxygen, over and above the resting oxygen consumption that is taken after exercise. This extra oxygen is used to "pay back" or restore metabolic conditions to the resting level in three ways: 1) to convert lactic acid back into glycogen stores in the liver. 2) to synthesize creatine phosphate and ATP in muscle fibers, and 3) to replace the oxygen removed from myoglobin.

Pro-opiomelanocorton (POMC) is cleaved to form a-MSH (melanocyte-stimulating hormone) wh

POMC is cleaved to form a-MSH (melanocyte-stimulating hormone) which helps promote skin color. It can also reduce food intake.

Autorhythmicity

Pacemaker cells create autorhythmicity, which is electrical potentials that are created within cardiac cells. This does not require nervous stimulation.

Calcitonin

Parafollicular cells (C cells) produce calcitonin (CT), which helps regulate calcium homeostasis. This hormone gets rid of calcium.

Hormone-Hormone Interactions

Permissive: some hormones need an exposure to second hormone to cause greater response in their target cells. Synergistic: 2 hormones acting together is greater than the sum of the individual effects. Antagonistic: one hormone opposes the actions of another hormone.

Isotonic Contraction

The tension developed by the muscle remains almost constant while the muscle changes in length. They are used for body movements and moving objects. Concentric Isotonic contraction is when the tension generated is great enough to exceed the load and the muscle shortens, pulling on another structure to produce a movement. Eccentric Isotonic Contraction is when the length of a muscle increases during a contraction. During an eccentric contraction, the tension exerted by the myosin crossbridges resist movement of a load and slows the lengthening process.

Isometric Contraction

The tension generated is not enough to exceed the load, and the muscle does not change its length. Isometric contractions occur when you try to lift an object that is too heavy for you to move. Muscles also contract isometrically in order to maintain posture and for supporting objects in a fixed position. Example: Iron cross in men's gymnastics.

Thymus

The thymus is located just above the heart. Two major hormones are produced by the thymus: thymosin and thymopoietin. These thymic hormones promote the maturation of T cells (a type of leukocyte that destroys microbes and other foreign substances.) Thymic hormones may also play a role in slowing down the aging process.

Adrenal Glands

There are two adrenal glands, one lying on top of each kidney. Each adrenal gland consists of two regions: an outer adrenal cortex, which makes up about 85% of the gland, and an inner adrenal medulla. The adrenal cortex produces three catecholamine hormones - epinephrine, norepinephrine, and a trace amount of dopamine.

Autonomic Control Centers

They are present in the brain and spinal cord. There are many control centers: cardiovascular, respiratory, deglutition (swallowing), salivation, vomiting, pupillary reflex center (in brain stem), erection, defecation, and micturition (urination). The hypothalamus is the major control and integration center for the ANS. It receives sensory input related to visceral functions, olfaction, gustation, changes in temperature, osmolality, and levels of various substances in the blood. It also receives input relating to emotions from the limbic system. Output from the hypothalamus influences autonomic centers in both the brain stem and spinal cord.

Stress-Relaxation Response

This phenomenon allows smooth muscle to undergo great changes in length while retaining the ability to contract effectively. Thus, even though smooth muscle in the walls of blood vessels and hollow organs such as the stomach, intestines, and urinary bladder can stretch, the pressure on the contents within them changes very little.

Tropic Hormones

Tropic hormones, or tropins, are hormones that act on other endocrine glands to tissues to regulate the secretion of another hormone.

Treppe

Warming up of the muscle. This only lasts for a few seconds.

Up Regulation

When a hormone is deficient, the number of receptors may increase. This phenomenon, know as up-regulation, makes a target cell more sensitive to a hormone.

Acetylcholine Receptors

Within the motor end plate are 30 to 40 million acetylcholine receptors (of the nicotinic type) that bind specifically to ACh. These receptors are abundant in junctional folds, deep grooves in the motor end plate that provide a large surface area for ACh.

Oxygen

You rarely give up more than 20% if the O2 that you have. Giving up even that little is enough to change the color of the blood.

Filaments within a sarcomere.

Z disc: narrow, plate-shaped regions of dense material that separate one sarcomere from the next. A Band: The dark, middle part of the sarcomere that extends the entire length of the thick filaments and also includes those parts of the thin filaments that overlap with the thick filaments. I band: The lighter, less dense area of the sarcomere that contains the rest of the thin filaments but no thick filaments. A Z disc passes through the center of each I band. H zone: A narrow region in the center of each A band that contains thick filaments but no thin filaments. M line: A region in the center of the H zone that contains proteins that hold the thick filaments together at the center of the sarcomere.

Premotor Cortex

The idea or desire to move is generated in one or more cortical association areas, such as the prefrontal cortex, somatosensory association area, auditory association area, or visual association area. This information is sent to the basal nuclei, which process the information and then send it to the thalamus and then to the premotor cortex, where motor plan is developed. This plan identifies which muscles should contract, how much they need to contract, and in what order. From the premotor cortex the plan is transmitted to the primary motor cortex for execution. The premotor cortex also stores information about learned motor activities.

Muscle Fatigue

The inability of a muscle to maintain force of contraction after prolonged activity. Fatigue results mainly from changes within muscle fibers.

Contraction Cycle

The repeating sequence of events that causes filaments to slide. It consists of four steps: 1) ATP hydrolysis. Myosin head hydrolyzes ATP and becomes energized and oriented. 2) Attachment of myosin to actin. Myosin head binds to actin, forming a crossbridge (the myosin head), 3) Power stroke. Myosin crossbridge pivots, pulling the thin filament past the thick filament toward the center of the sarcomere. 4) Detachment of myosin to actin. As myosin head binds ATP, the crossbridge detaches from actin .

Cretinism

that absence of thyroid hormone in an infant.

Follicles

the site of thyroid hormone synthesis

Capacity for Regeneration of Muscle

Skeletal Muscle: limited, via satellite cells Cardiac Muscle: limited, under certain conditions Smooth Muscle: Considerable, via pericytes (compared with other muscle tissues, but limited compared to epithelium.)

Three Types of Muscle

Skeletal: striated, voluntary, and has it's own input from an axon. It is attached to bones and moves parts of the skeleton. Cardiac: also striated, but involuntary. It's contractions are not under conscious control. Instead, it has a pacemaker that initiates each contraction. This built-in rhythm is termed autorhythmicity. Smooth: nonstriated, and involuntary. It is located in the walls of hollow internal structures such as blood vessels, airways, stomach, intestines, and uterus.

Muscle Properties

1) Electrical excitability, a property of both neurons and muscles cells, is the ability to respond to certain stimuli by producing action potentials. For muscle cells, two main types of stimuli trigger action potentials. One is chemical stimuli, such as neurotransmitters released by neurons and hormones distributed by the blood. The other is autorhythmic electrical signals arising in the muscle tissue itself, as in the hearts pacemaker. 2) Contractility is the ability of muscle to contract forcefully when adequately stimulated. When a muscle contracts, it generates tension while pulling on its attachment points. It the tension generated is enough to overcome the resistance of the object to be moved, the muscle shortens and movement occurs. 3) Extensibility is the ability of muscle to stretch without being damaged. Extensibility allows a muscle to contract forcefully even if it is already stretched. Normally, smooth muscle is subject to the greatest amount of stretching. For example, each time your stomach fills with food, the muscle in its wall is stretched. Cardiac muscle is also stretched each time the heart fills with blood. 4) Elasticity is the ability of muscle to return to its original length and shape after contraction or extension.

Factors Determining Muscle Tension

1) Frequency of stimulation. If two stimuli are applied to a skeletal muscle fiber, one immediately after the other, the muscle fiber will respond to the first stimulus but not to the second. When a muscle fiber receives enough stimulation to contract, it temporarily loses its excitability and cannot respond for a period of time. The period of lost excitability, called the refractory period, is a characteristic of all muscle and nerve cells. Wave summation -stimuli that occurs at different times cause contractions with greater tension. Unfused (incomplete) tetanus - a sustained but wavering contraction. Fused (complete) tetanus - a smooth, sustained contraction in which individual twitches cannot be detected and maximum tension is reached. 2) Muscle Fiber Length. The length-tension relationship for a skeletal muscle fiber indicates how the forcefulness of muscle contractions depends on the length of the sarcomeres within a muscle fiber before contraction begins. 3) Muscle Fiber Diameter. Muscle fibers that have a thicker diameter have more myofibrils and can generate more tension compared to muscle fibers that have a thinner diameter. 4) Motor Unit Size. The size of the motor units that are activated in a muscle affects the amount of tension that muscle can generate. Muscles that control precise movements, which involve only small amounts of force, contain small motor units. By contrast, muscles responsible for large-scale movements have large motor units. 5) Motor Unit Recruitment. When a muscle needs to generate more force during a contraction, more of its motor units are activated. The process of increasing the number of active motor units is called motor unit recruitment. Recruitment is one factor responsible for producing smooth movements rather than a series of jerks. Typically, the different motor units of an entire muscles are not stimulated to contract in unison. While some motor units are contracting, other are relaxed, a phenomenon known as asynchronous recruitment of motor units.

Hypothalamic Control of the Anterior Pituitary

1) Growth hormone-releasing hormone (GHRH), also known as somatocrinin, stimulates the secretion of growth hormone. 2) Thyrotropin-releasing hormone (TRH) stimulates secretion of thyroid-stimulating hormone. 3) Corticotropin-releasing hormone (CRH) stimulates secretion of adrenocorticotropic hormone. 4) Prolactin-releasing hormone (PRH) stimulates secretion of prolactin. 5) Gonadotropin-releasing hormone (GnRH) stimulates secretion of FSH and LH. The hypothalamus also releases two inhibiting hormones, which suppress secretion of anterior pituitary hormones: 1) Growth hormone-inhibiting hormone (GHIH), also known as somatostatin, suppresses secretion of growth hormone. 2) Prolactin-inhibiting hormone (PIH), which is dopamine, suppresses secretion of prolactin.

There are four types of input to Lower Motor Neurons

1) Local circuit neurons. Input arrives at lower motor neurons from nearby interneurons called local circuit neurons. These neurons are located close to the lower motor neuron cell bodies in the brain stem and spinal cord. Local circuit neurons coordinate many types of somatic reflexes and play a major role in locomotion (walking and running). 2)Upper motor neurons. Both local circuit neurons and lower motor neurons receive input from upper motor neurons, (an interneuron, not a true neuron.) neurons that have their cell bodies in motor processing centers of the upper parts of the CNS. Most upper motor neurons synapse with local circuit neurons, which in turn synapse with lower motor neurons. A few upper motor neurons synapse directly with lower motor neurons. Upper motor neurons from the cerebral cortex are essential for the planning and execution of voluntary movements of the body. Other upper motor neurons originate in motor centers of the brain stem: the vestibular nuclei, reticular formation, superior colliculus, and red nucleus. Upper motor neurons from the brain stem help regulate posture, balance, muscle tone, and reflexive movements of the head and trunk. 3) Basal Nuclei. Neurons of the basal nuclei assist movement by providing input to upper motor neurons. Neural circuits interconnect the basal nuclei with motor areas of the cerebral cortex and the brain stem. These circuits help initiate movements, suppress unwanted movements, and establish a normal level of muscle tone. 4) Cerebellum. Neurons of the cerebellum also aid movement by controlling the activity of upper motor neurons. Neural circuits interconnect the cerebellum with motor areas of the cerebral cortex and the brain stem. A prime function of the cerebellum is to monitor differences between intended movements and movements actually performed. Then, it's issues commands to upper motor neurons to reduce errors in movement. The cerebellum thus coordinates movements and helps maintain normal posture and balance.

Three things that determine growth, repair, healing, and regeneration:

1) Nutrition 2) Circulation 3) Aging

Muscle Functions

1) Producing body movements. Movements of the whole body such as walking and running, and localized movements such as grasping a pencil or nodding the head, rely on the integrated functioning of skeletal muscles, bones, and joints. 2) Stabilizing body positions. Skeletal muscle contractions stabilize joints and help maintain body positions, such as standing or sitting. Postural muscles contract continuously when you are awake; for example, sustained contractions for you neck muscles hold your head upright. 3) Storing and moving substances within the body. Storage is accomplished by sustained contractions of ringlike bands of smooth muscle called sphincters, which prevent outflow of the contents of a hollow organ. Temporary storage of food in the stomach or urine in the urinary bladder is possible because smooth muscle sphincters close off the outlets of these organs. Cardiac muscle contractions of the heartpump blood through the blood vessels of the body. Contraction ad relaxation of smooth muscle in the walls of blood vessels help adjust blood vessel diameter and thus regulate the rate of blood flow. Smooth muscle contractions also move food and substances such as bile and enzymes through the GI tract, push gametes through the passageways of the reproductive systems, and propel urine through the urinary system. Skeletal muscle contractions promote the flow of lymph and aid the return of blood to the heart. 4) Generating Heat. As muscle contracts, it produces heat, a process known as thermogenesis. Much of the heat is generated by muscle is used to maintain normal body temperature. Involuntary contractions of skeletal muscles, known as shivering, can increase the rate of heat production.

Types of Skeletal Muscle Fibers

1) Slow Oxidative Fibers are the smallest in diameter and thus are the least powerful type of muscle fibers. They appear dark red because the contain large amounts of myoglobin and many blood capillaries. Because they have many large mitochondria, SO fibers generate ATP mainly by aerobic respiration, which is why they are called oxidative fibers. These fibers are said to be "slow" because the ATPase in the myosin heads hydrolysis ATP relatively slowly and the contraction cycle proceeds at a slower pace than the "fast" fibers. As a result, SO fibers have a slow speed of contraction. Slow fibers are resistant to fatigue and are capable of prolonged, sustained contractions for many hours. These slow-twitch, fatigue-resistant fibers are adapted for maintaining posture and for aerobic, endurance type activity. 2) Fast Oxidative Fibers are intermediate in diameter between the other two types of fibers. Lie slow oxidative fibers, they contain large amounts of myoglobin and many blood capillaries. Thus, they also have a dark red appearance. FOG fibers can generate considerable ATP by aerobic respiration, which gives them moderate resistance to fatigue. Because their intercellular glycogen level is high, they also generate ATP by anaerobic glycolysis. FOG fibers are fast because the ATPase in their myosin heads hydrolyzes ATP three to five times faster than myosin ATPase in SO fibers, which makes their speed of contraction faster. Thus twitches of FOG fibers reach peak tension more quickly than those of SO fibers but are briefer in duration- less than 100 msec. FOG fibers contribute to activities such as walking and sprinting. 3) Fast oxidative-glycolytic fibers are the largest in diameter and contain the most myofibrils. Hence, they can generate the most powerful contractions. FG fibers have low myoglobin content, relatively few blood capillaries, few mitochondria, and appear white in color. They contain large amounts of glycogen and generate ATP mainly by anaerobic glycolysis. Due to their large size and their ability to hydrolyze ATP rapidly, FG fibers contract strongly and quickly. These fast-twitch fibers are adapted for intense anaerobic movements in short duration, such as weight lifting or throwing a ball, but they fatigue quickly.

Types of Anterior Pituitary Cells

1) Somatotrophs secrete growth hormone (GH), also known as somatotropin. Growth hormone stimulates general body growth and regulates aspects of metabolism. 2) Thyrotrophs secrete thyroid-stimulating hormone (TSH), also called thyrotropin. TSH controls the secretion and other activities of the thyroid gland. 3) Corticotrophs secrete adrenocorticotropic hormone (ACTH), also referred to as corticotropin, which stimulates the adrenal cortex to secrete glucocorticoids such as cortisol. 4) Lactotrophs secrete prolactin (PRL), which initiates milk production in the mammary glands. 5) Gonadotrophs secrete two gonadotropins: follicle stimulating hormone (FSH) and luteinizing hormone (LH). FSH and LH both act on the gonads. In men, they stimulate the testes to produce sperm and to secrete testosterone. In women, they stimulate the ovaries to produce eggs and to secrete estrogens and progesterone.

Lipid Soluble Hormones

1) Steroid Hormones are derived from cholesterol. They are lipid soluble because they contain four interconnected hydrocarbon rings. Steroid hormones include aldosterone, cortisol, dehydroepiandrosterone, testosterone, estrogens, and progesterone. 2) Thyroid Hormones are synthesized by attaching iodine to the amino acid tyrosine. T3 and T4 are lipid-soluble because they contain two hydrocarbon rings.

Insulin performs a variety of functions in the body.

1) Uptake of glucose 2) Formation of glycogen 3) Inhibition of process that releases glucose. 4) Uptake of fatty acids and formation of triglycerides. 5) Uptake of amino acids and formation of proteins.

The brain stem has 4 major motor centers that helps body movements.

1) Vestibular nuclei in the medulla and pons 2) Reticular formation located throughout the brain 3) Superior colliculus in the midbrain 4) Red nucleus also in the midbrain

The Adrenal Cortex Consists of 3 Glands that Secrete Hormones:

1) Zone glomerulosa, which is the outer zone that secretes hormones called mineralocorticoids because they affect mineral homeostasis. 2) Zona fasciculate is the middle zone and the widest of the three zones. These cells secrete mainly glucocorticoids, so named because they affect glucose homeostasis. 3) Zona reticularis is the inner zone that synthesizes small amounts of weak androgens, steroid hormones that have masculinizing effects.

Hormone Secretion can be regulated by:

1) signals from the nervous system 2) chemical changes in the blood 3) distension of an organ 4) other hormones.

Adipose Tissue Secretes Leptin

Adipose tissue produces leptin, a hormone that helps decrease total body fat. As fat stores increases, more leptin is secreted by adipose tissue. Leptin in turn acts on the brain to suppress appetite, thereby reducing food intake. Leptin also increases energy expenditure, which helps breakdown body fat reserves.

Agonist and Antagonist

Agonist- makes the muscle movements Antagonist- makes opposite movement at the same joint.

Kidney Control Center

The kidneys have a separate control center for the blood - they can control their own pressure, autoregulation. Uremia is the urine buildup in the blood. It happens when the kidneys don't filter the blood. IF not treated it will kill you.

The kidneys secrete calcitriol and erythropoietin

The kidneys produce a hormone called calcitriol, which is an active form of vitamin D. Calcitriol increases the absorption of calcium and phosphate ions from food in the small intestine into the bloodstream. Recall that synthesis of calcitriol begins in the skin, continues in the liver, and ends in the kidneys. Another hormone produced by the kidneys is erythropoietin (EPO), which increases the rate of erythrocyte (RBC) production. The kidneys secrete EPO in response to low levels of oxygen in the tissues.

Primary Motor Cortex

The primary motor cortex is the major control region for the execution of voluntary movements. Electrical stimulation of any point on the primary motor cortex causes contraction of specific muscles on the opposite side of the body. The primary motor cortex controls muscles by forming descending pathways that extent to the spinal cord and brain stem.

Pancreas

The pancreas is an elongated, tapered gland located behind the stomach. It contains both exocrine portions and endocrine portions. The exocrine portion, which forms about 99% of the pancreas, secretes fluid containing digestive enzymes into ducts. The endocrine portion, which comprises the remaining 1% of the pancreas, consists of clusters of cells called pancreatic islets (islets of Langerhans) that secrete hormones.

Parathyroid Gland/Hormone

The parathyroid gland is a small, round messes of glandular tissue that's in the back pf thyroid glands. The parathyroid hormone (PTH) are major regulators for Ca, Mg, HPO4^2-. It slows the rate at which these are lost from blood into the urine.

Pineal Gland

The pineal gland is a small endocrine gland associated with the brain. It secretes melatonin, an amine hormone derived from serotonin. Melatonin has several functions, which include the following: 1) Influences circadian rhythms. These are patterns of biological activity (i.e. sleep-wake cycle, secretion of certain hormones, and slight fluctuations in body temperature.) that occur in a 24 hour cycle. 2) Induces Sleep. As more melatonin is liberated during darkness than in light, this hormone is thought to promote sleepiness. During sleep, plasma levels of melatonin increase tenfold and then decline to a low level again before a person awakens. 3) Protects against free radicals. Melatonin is a potent antioxidant that protects against oxygen-derived free radicals, such as hydroxyl and superoxide radicals. 4) Inhibits reproductive functions. In animals that breed during specific seasons, melatonin inhibits reproductive functions. Melatonin levels are higher in children and decline with age into adulthood, but there is no evidence that changes in melatonin secretion correlate with the onset of puberty and sexual maturation.