gen physio; membrane physio, nerve and muscle Flashcards
It is also known as the internal environment of the body where all cells essentially live. It contains ions and nutrients needed by cells to maintain cell life
Extracellular fluid
How many percent of fluid does the human body have?
Fraction of intracellular and extra cellular fluid?
60% fluid
2/3 intracellular
1/3 extracellular
Difference of extracellular and intracellular fluid in terms of contents.
Extracellular has large amount of Nà, Cl, HCO3, CO2, O2, glucose, AA, NA.
Intracellular contains K, P, Mg.
Most abundant of all the end products of metabolism.
CO2
It has a special control mechanism to maintain constant oxygen concentration in extracellular fluid. It has strong affinity to oxygen that it does not release oxygen into tissue fluid if too much oxygen is already there. But if oxygen concentration is too low, sufficient oxygen is released to reestablish an adequate concentration.
Hemoglobin
Control mechanism of respiratory system to carbon dioxide.
Higher than normal CO2 concentration in the blood excites the respiratory center, causing a person to breathe rapidly and deeply. This increases expiration of CO2 and therefore removes excess CO2 from the blood and tissue fluids.
Regulation of arterial blood pressure by baroreceptor system. Where can you find baroreceptors?
Bifurcation region of carotid artery in the neck.
Arch of aorta in the thorax.
Stimulated by the stretch of arterial wall.
Regulation of arterial blood pressure by baroreceptor system. What happens if there is high arterial pressure? Low arterial pressure?
High arterial pressure: baroreceptors sends impulse to medulla to inhibit vasomotor system. Decrease or lack of impulse causes the decrease pumping of heart and dilation of blood vessels allowing increased blood flow. These effects decreases the arterial pressure.
Low arterial pressure: baroreceptors relaxes the stretch receptors causing vasoconstriction and increased pumping of heart. Thus increases the arterial pressure.
Too low concentration leads to paralysis as a result of nerves’ inability to carry signals.
Too high concentration leads to severely depressed heart.
Too low concentration leads to tetanic contraction of muscles throughout the body because of spontaneous generation of excess nerve impulses.
Too low concentration leads to extreme mental irritability and convulsion.
Too high concentration leads to vicious cycle of increasing cellular metabolism that destroys the cells.
(Glucose, potassium, calcium, temperature)
Potassium: Too low concentration leads to paralysis. Too high concentration leads to severely depressed heart.
Calcium: too low concentration leads to tetanic contraction of muscles.
Glucose: Too low concentration leads to extreme mental irritability and convulsion.
Temperature: Too high concentration leads to vicious cycle of increasing cellular metabolism that destroys the cells
Heart pumps how many liter of blood per minute?
5 L of blood/minute
Blood clotting, childbirth, generation of nerve signals are examples of what type of feedback?
Positive feedback
The different substances that makes up the cell are collectively called as? What are those substances?
Protoplasm is composed mainly of water, proteins, electrolytes, lipid and carbohydrates.
Peroxisomes and lysosomes are physically similar. But where does peroxisome and lysosomes formed? And the enzymes they have?
Peroxisome is formed from SER and contains oxidase.
Lysosome is formed from Golgi apparatus and contains hydrolase.
Very large particles enter the cell by a specialized function of the cell membrane called _____.
Endocytosis
Principal form of endocytosis which means ingestion of minute particles that form vesicles.
Pinocytosis
Principal form of endocytosis which means ingestion of large particles, such as bacteria, whole cells, or portions of degenerating tissue.
Phagocytosis
What organelle is responsible in regression of tissues?
Lysosomes
Other function of SER aside from lipid synthesis.
Glycolysis and detoxification
A movement of an entire cell in relation to its surroundings, such as movement of WBC thru tissues.
Ameboid movement
Types of cells that exhibit ameboid locomotion.
WBC, fibroblasts, sessile cells, germinal cells of the skin, germinal cells
The most important initiator of ameboid locomotion is the process called ____.
Chemotaxis
Cellular motion that has a whiplike movement of cilia on the surfaces of cells.
Ciliary movement
Ciliary movement occurs only in two places in the human body.
1) on surface or respiratory airways (clearing passageways of mucus and particles in pharynx)
2) on inside surface of uterine tube (ostium) for slow movement of fluid and ovum to uterus
Specific code on transfer RNA that allows it to recognize a specific codon.
Anticodon
Where does ribosomal RNA processed?
Nucleolus
Two types of control of gene function and biochemical activity in cells
Gene regulation and enzyme regulation
Area of DNA strand where sequence of genes for enzyme formation is located.
Operon
In Operon, the genes responsible for forming the respective enzymes are called _____.
Structural genes
True or false:
Cell differentiation results not from loss of genes but from selective repression of different genetic operons.
True
Apoptosis is initiated by activation of a family of proteases called _______.
Caspases
True or false: heat, the greater the motion, the higher the temperature
True
Kinetic movement of molecules or ions occurs thru a membrane opening or thru intermolecular spaces without any interaction with carrier proteins in the membrane.
Simple diffusion
Diffusion that requires interaction of carrier proteins which aids passage of the molecules or ions thru the membrane by binding chemically with them and shuttling them thru the membrane in this form.
Facilitated diffusion
True or false: Oxygen, nitrogen, carbon dioxide and alcohol have high lipid solubility.
True
Two important characteristics of protein channels.
Selective permeability and can be opened or closed by gates.
If the inside of the cell becomes less negative, the Nà gates open and the Nà ions enter the cell. This is a basic mechanism of..
And if the inside of the cell becomes more positive, the K gates open and is responsible in…
Opening of Nà gates is responsible in eliciting action potential. While the K gates is responsible in terminating action potential.
This law demonstrates that the gate of the channel snaps open and then snaps closed, each open state lasting for only a fraction of a millisecond up to several milliseconds. At one voltage potential, the channels may remain closed all the time or almost all the time, whereas at another voltage level, it may remain open either all or most of the time.
All-or-none law
Method for recording ion current flow through the single channels.
Patch-clamp method
True or false: the rate of simple diffusion continues to increase proportionately, but in the case of facilitated diffusion, the rate of diffusion cannot rise greater than the Vmax level.
True
True or false: glucose and other amino acids are among the important substances that cross the cell membranes by simple diffusion.
False, it crosses membrane by facilitated diffusion
The electrical difference that will balance the a given concentration difference of univalent ions can be determines from what equation?
Ernst equation:
EMF (in mV) = (+-)61log C1/C2
Electromotive force
The pressure in capillaries is about how many mm Hg greater inside than outside?
20 mm Hg
The exact amount of pressure required to stop osmosis.
Osmotic pressure
True or false: the osmotic pressure exerted by particles in a solution, whether they are molecules or ions, is determined by the umber of particles p unit volume fluid, not by the mass of the particles.
True. Each particle in a soln, regardless of its mass, exerts, on average, the same amt of pressure against the membrane.
In active transport, the energy is derived directly from the breakdown of..
ATP
3 Specific features that are important for the functioning of the pump.
3 receptor sites for binding Nà ions
2 receptor sites for binding K ions
ATPase activity in the inside portion of protein near Nà binding sites
At two places in the body, primary active transport of H ions is very important:
1) gastric glands of parietal cells of stomach (HCl)
2) distal tubule and cortical collecting ducts of kidneys (urine)
Co-transport or counter-transport
Nà-glucose, Nà-AA, Nà-Ca, Nà-H
Co-transport : Nà-glucose and Nà-AA
Counter-transport: Nà-Ca and Nà-H
The potential difference required for K, with the negativity inside the fiber membrane
-94mV
The potential difference required for Na, positive inside the fiber membrane
61mV
What is the resting potential of large nerve fibers when not transmitting nerve signals
-90mV
Why does Na-K pump said to be electrogenic?
Because more positive charge are pumped to the outside than to the inside
Why is the emphasis of K-Na“leak” channel is on potassium leakage?
because, on average, the channels are far more permeable to potassium than to sodium, normally about 100 times as permeable.
What contributes to the resting potential of a membrane?
Diffusion potential of Nà and K: -86 mV (Goldman equation)
Na-K pump: -4 mV
Total of -90mV
True or false: In nerve action potential, the resting stage is said to be polarized.
True
In what stage of nerve action potential where the membrane suddenly becomes very permeable to Nà ions, allowing tremendous numbers of (+) charged Nà ions to diffuse to the interior of the axon.
Depolarization stage
In what stage of nerve action potential where the Nà channels begin to close and the K channels open more than normal. Then, rapid diffusion of K ions to the exterior re-establishes the normal negative resting membrane potential.
Repolarization stage
True of false: in the sodium channel inactivation process, the inactivation gate will not reopen until the membrane potential returns to or near the original resting membrane potential level.
True
What does the calcium pump do?.
Ca pump pumps Ca ions from the interior to the exterior of the CM (or into the ER).
There are voltage-gated calcium channels. These channels are slightly permeable to Nà ions as well as to Ca ions; when they open, both Ca and Nà ions flow to the interior of the fiber. Therefore, these channels are also called Ca-Na channels.
Where are Ca channels abundant?
Cardiac and smooth muscle
What happens to the Nà permeability if there is calcium deficit?
When there is a deficit of Ca ions, the Nà channels become activated (opened) by very little increase of the membrane poten- tial from its normal, very negative level. Therefore, the nerve fiber becomes highly excitable, sometimes discharging repetitively without provocation rather than remaining in the resting state. Which causes muscle tetany.
True or false: as long as the membrane of the nerve fiber remains undisturbed, no action potential occurs in the normal nerve.
True. However, if any event causes enough initial rise in the membrane potential from –90mV toward the zero level, the rising voltage itself causes many voltage-gated Nà channels to begin opening.
What is the threshold level for stimulation of action potential?
-65mV
What are the two types of channel that enters the depolarization stage?
The usual fast channel which is the Nà channel and the slow channel that is the Ca channel.
Nerve action potential that occurs only at nodes (of Ranvier)
Saltatory conduction
Give significance of Saltatory conduction.
Increases velocity of nerve signal transmission.
Conserve energy for axon because only the nodes depolarize.
3 excitation or processes that elicits action potential
1) mechanical disturbance of the membrane [mechanical pressure to excite sensory nerve endings in the skin]
2) chemical effects on the membrane [chemical neurotransmitters to transmit signals from one neuron to the next in the brain]
3) passage of electricity through the membrane [electrical current to transmit signals between successive muscle cells in the heart and intestine]
The period during which a second action potential cannot be elicited, even with a strong stimulus, is called ____.
Absolute refractory period. This period for large myelinated nerve fibers is about 1/2500 second. Therefore, one can readily calculate that such a fiber can transmit a maximum of about 2500 impulses per second.
a high extracellular fluid calcium ion concentration decreases membrane permeability to sodium ions and simultaneously reduces excitability. Therefore, calcium ions are said to be a ______.
Stabilizer
What is the cell membrane of a muscle fiber
Sarcolemma
These are light bands contain only actin filaments and are isotropic to polarized light.
I band
The dark bands contain myosin filaments, as well as the ends of the actin filaments
where they overlap the myosin, and are anisotropic to polarized light.
A band
Ends of actin filaments are attached to a..
Z disc
What do you call the portion of the myofibril (or of the whole muscle fiber) that lies between
two successive Z discs?
Sarcomere
Length of sarcomere
2micrometer
What keeps myosin and actin filaments in place?
Titin filamentous molecules.
These springy titin molecules act as a framework that holds the myosin and actin filaments in
place so that the contractile machinery of the sarcomere will work.
General mechanism of muscle contraction
1) AP travels along motor nerve to its ending.
2) At endings, the nerve secretes small amount of acetylcholine.
3) ACH acts on fibers which opens ACH-gated voltage channels which allows Nà ions to diffuse into muscle fiber membrane. AP starts at the membrane.
4) AP depolarizes the membrane causing the SR to release Ca.
5) Ca initiates attractive forces between actin and myosin filaments, initiating the contraction
6) before contraction begins, the heads of cross bridges binds with ATP.
7) myosin head attaches to the active site of actin filament. It causes the head to tilt towards the arm,dragging the actin along with it. immediately after tilting, head breaks away.
8) after a fraction of sec, the Ca are pumped back until a new muscle AP comes along.
Length of myosin filament
1.6 micrometer
ATPase activity of myosin head.
allows the head to cleave ATP and to use the energy derived from the ATP’s high-energy phosphate bond to energize the contraction process.
Length of actin filament
1 micrometer
True or false: A pure actin filament without the presence of the troponin-tropomyosin complex (but in the presence of magnesium ions and ATP) binds instantly and strongly with the heads of the myosin molecules.
True
Troponin I, T and C has high affinity to ..
Troponin I: actin
Troponin T: tropomyosin
Troponin C: Ca ions
active sites on the normal actin filament of the relaxed muscle are inhibited or physically covered by the troponin- tropomyosin complex. Consequently, the sites cannot attach to the heads of the myosin filaments to cause contraction. Before contraction can take place, the inhibitory effect of the troponin-tropomyosin complex must itself be inhibited. What is the role of Ca?
This brings us to the role of the calcium ions. In the presence of large amounts of calcium ions, the inhibitory effect of the troponin-tropomyosin on the actin filaments is itself inhibited.
The greater the amount of work performed by the muscle, the greater the ATP is cleaved.
Fenn effect
Sources of energy for rephosphorylation of ADP
1) phosphocreatine (higher amt of energy than ATP)
2) glycolysis (breakdown of glycogen)
3) oxidative metabolism
More than 95 per cent of all energy used by the muscles for sustained, long-term contraction is derived from this source.
Oxidative metabolism
Isotonic or isometric contraction
- when the muscle does not shorten during contraction
- when it does shorten but the tension on the muscle remains constant throughout the contraction.
- Isometric
2. Isotonic
Smallest muscle
Stapedius muscle
Largest muscle
Quadriceps muscle
White or red muscle? Slow or fast muscle?
1) reacts rapidly
2) responds slowly
3) large fibers
4) small fibers
5) extensive SR
6) innervated by smaller nerve fibers
7) many glycolytic enzymes for rapid release of energy
8) many myoglobin
9) few blood supply, few mitochondria
10) many blood supply, many mitochondria
1) reacts rapidly - white
2) responds slowly. Red
3) large fibers. White
4) small fibers. Red
5) extensive SR. White
6) innervated by smaller nerve fibers. Red
7) many glycolytic enzymes for rapid release of energy. White
8) many myoglobin. Red
9) few blood supply, few mitochondria. White
10) many blood supply, many mitochondria. Red
Summation means the adding together of individual twitch contractions to increase the intensity
of overall muscle contraction. Summation occurs in two ways:
(1) by increasing the number of motor units contracting simultaneously (multiple fiber summation)
(2) by increasing the frequency of contraction (frequency summation) and can lead to tetanization
successive contractions that eventually become so rapid that they fuse together, and the whole
muscle contraction appears to be completely smooth and continuous
Tetanization
maximum strength of tetanic contraction of a muscle operating at a normal muscle length
3-4 kg/cm3
50 lbs/in2
Facts: Virtually all muscle hypertrophy results from an increase in the number of actin and myosin filaments in each muscle fiber
Facts: muscles are stretched to greater than normal length which causes new sarcomeres to be added at the ends of the muscle fibers, where they attach to the tendons
In the final stage of denervation atrophy, most of the muscle fibers are destroyed and replaced by
fibrous and fatty tissue
The fibrous tissue that replaces the muscle fibers during denervation atrophy also has a
tendency to continue shortening for many months, which is called..
Contracture
Several hours after death, all the muscles of the body go into a state of contracture called “rigor mortis”; that is, the muscles contract and become rigid, even without action potentials. This rigidity results from loss of all the ATP, which is required to cause separation of the cross- bridges from the actin filaments during the relaxation process. The muscles remain in rigor until the muscle proteins deteriorate for about how many hours?? which presumably results from autolysis caused by enzymes released from lysosomes.
15-25 hrs
When a nerve impulse reaches the neuromuscular junction, how many vesicles of ACTH are
released from the terminals into the synaptic space?
125 vesicles of ACTH
the effective stimulus for causing ACTH release from the vesicles is entry of _____ and that ACTH from the vesicles is then emptied through the neural membrane
Calcium ions
The ACTH, once released into the synaptic space, continues to activate the ACTH receptors
as long as the ACTH persists in the space. However, it is removed rapidly by two means:
(1) Mostly by the enzyme acetylcholinesterase, which is attached mainly to the spongy layer
of fine ct that fills the synaptic space
(2) A small amount of ACTH diffuses out of the synaptic space and is then no longer available
to act on the muscle fiber membrane.
When will the ACTH channel be opened?
After ACTH has become attached and a conformational change has opened the channel,
allowing Nà ions to enter the muscle fiber and excite contraction.
What are the drugs that stimulate the nerve transmission at neuromuscular junction?
Nicotine
Methacholine
Carbachol
What are the drugs that stimulate the nerve transmission at neuromuscular junction by
inactivating acetylcholinesterase
Neostigmine
Physostigmine
Diisopropyl fluorophosphate (nerve gas poison)
A group of drugs that is known to prevent passage of impulses from the nerve ending into
the muscle
Curariform drugs
This disease causes muscle paralysis because of inability of the neuromuscular junctions to transmit enough signals from the nerve fibers to the muscle fibers.
Myasthenia gravis.
Pathologically, ab that attack the ACTH-gated na ion transport proteins have been demonstrated in the blood of most patients with myasthenia gravis. Therefore, it is believed that it is an autoimmune disease in which the patients have developed immunity against their own ACTH-activated ion channels.
Resting membrane potential in skeletal muscle
-80 to -90 mV
Resting membrane potential in smooth muscle
-50 to -60 mV
Spread of action potential is made possible by..
Transverse tubules, that penetrate all the way through the muscle fiber from one side of the fiber to the other
This occurs after contraction wherein calcium ions are removed from the myofibrillar fluid
Calcium pump.
In addition, inside the reticulum is a protein called calsequestrin that can bind up to 40x more Ca.
Type of smooth muscle composed of discrete, separate sm muscle fiber. Each fiber can contract independently of others, and their control is exerted mainly of nerve signals.
Multi-unit smooth muscle
Type of smooth muscle wherein each fiber contracts together as a single unit, and their control is exerted by non-nervous stimuli.
Unitary smooth muscle
Smooth uncle contracts as much as ____% of their length, while skeletal muscle contracts ___%.
Smooth muscle: 80%
Skeletal muscle: 30%
Reasons behind prolong tonic contraction in smooth muscle
Increased fraction of time that the cross bridges remain attached to the actin filament.
Slowness of attachment and detachment of cross bridges to actin filaments.
Less ATPase activity of cross bridges heads, so that Thea degradation of ATP is reduced (slow cycling).
Slower initiation of contraction in response to calcium ions.
This regulatory protein, (to replace Troponin) initiates contraction by binding with Calcium ions and activating the myosin kinase.
Calmodulin
When the calcium ion concentration falls below the critical level, the aforementioned process is automatically reversed, except for the phosphorylation of myosin head. Reversal of action requires what enzyme?
Myosin phosphatase
True or false: When ACTH excites a muscle fiber, norepinephrine ordinarily inhibits it. Conversely, when ACTH inhibits a fiber, norepinephrine usually excites it.
True
The action potential of visceral smooth muscle occurs in one of two forms
1) spike potential
2) action potential with plateau
Visceral smooth muscle has a _____, where in if strong enough (from -60 to -35mV) can
initiate AP.
Slow wave potential
Control factors that causes vasodilation
1) lack of oxygen
2) excess carbon dioxide
3) increased hydrogen ions
Calcium ions that are released from sarcoplasm comes from what part of sarcoplasmic reticulum?
Cisternae
