a&P lecture exam 3
what is the resting membrane potential of a neuron
- 70 mV is avg but can vary from -40 to -90
anaerobic glycolysis (No oxygen)
- Glucose passes easily from the blood into contracting muscle fibers via facilitated diffusion, and it is also produced by the breakdown of glycogen within muscle fibers - The glycolysis quickly breaks down each glucose molecule into two molecules of pyruvic acid and produces a net gain of two molecules of ATP.
Acetylcholine (ACh)
- excitatory at iontropic receptors and opens cation channels - inhibitory at metabotropic receptors and coupled to G proteins that open K+ channels
threshold
-55 mV - threshold stimulus is a stimulus that is strong enough to depolarize membrane to threshold
resting membrane potential arises from what three major factors?
1. unequal distribution of ions in the ECF and cytosol - ECF is rich in Na+ and Cl- but in Cytosol is rich in K+ - outside cell is more positive and inside is more negative 2. inability of most anions to leave the cell because they cant follow K+ out of cell since they are attached for ATP and large proteins 3. electrogenic nature of the Na+-k+ ATPases - The small inward Na+ leak and outward K+ leak are offset by the Na+-K+ ATPases (sodium-potassium pump) - pumps help maintain the resting membrane potential by pumping out Na+ as fast as it leaks in ( every 2 K+ in then 3 NA+ out)
spatial summation
2 more multiple presynaptic neurons from 2 different places (sources) -2 signals reach postsynaptic at same time to bring neuron to threshold
what is produced by aerobic respirtation
30-32 ATP molecules - supplies enough ATP for muscles during periods of rest or light to moderate exercise provided sufficient oxygen and nutrients are available.
Myasthenia Gravis cause
75% of patients with myasthenia gravis have hyperplasia or tumors of the thymus so it is thought that thymic abnormalities cause the disorder.
Cramp
A painful spasmodic contraction - caused by inadequate blood flow to muscles, overuse of a muscle, dehydration, injury, holding a position for prolonged periods, and low blood levels of electrolytes, such as potassium
Is the ratio of fast glycolytic and slow oxidative fibers in everyone's muscle the same?
No, The relative ratio of fast glycolytic (FG) and slow oxidative (SO) fibers in each muscle is genetically determined and helps account for individual differences in physical performance.
aerobic respiration (slowest ATP process)
If sufficient oxygen is present, the pyruvic acid formed by glycolysis enters the mitochondria - undergoes Krebs cycle and electron transport chain which produces ATP, Carbon dioxide, water and heat
what is electrochemical gradient?
The separation of chemical or ion across the membrane. It's the difference between the two areas.
synapse
The site of communication between two neurons or between a neuron and an effector cell
latent period
When Action potential has been generate and calcium is released from sacroplasmic reticulum - brief delay occurs between application of stimulus and beginning of contraction - 2msec
nerve action potential
When an action potential occurs in a neuron (nerve cell)
ion channel
When ion channels are open, they allow specific ions to move across the plasma membrane, down their electrochemical gradient - they open and close due to presence of "gates"
When is anaerobic glycolysis used?
When muscle activity continues and the supply of creatine phosphate within the muscle fiber is depleted, glucose is catabolized to generate ATP.
Multiple sclerosis (MS)
autoimmune disease that causes a progressive destruction of myelin sheaths surrounding neurons in the CNS - It usually appears between the ages of 20 and 40 -affecting females twice as often as males -common in whites, less common in blacks, and rare in Asians.
twitch contraction
brief contraction of all muscle fibers in a motor unit in response to a single action potential in its motor neuron
nerve
bundle of hundreds to thousands of axons plus associated connective tissue and blood vessles that lies outside the brain and spinal cord
neurofibrils
composed of bundles of intermediate filaments that provide the cell shape and support
white matter
composed primarily of myelinated axons.
motor unit
consists of a somatic motor neuron plus all of the skeletal muscle fibers it stimulates - A single somatic motor neuron makes contact with an average of 150 skeletal muscle fibers - all of the muscle fibers in one motor unit contract in unison - Typically, the muscle fibers of a motor unit are dispersed throughout a muscle rather than clustered together.
cell body
contains a nucleus surrounded by cytoplasm that includes typical cellular organelles such as lysosomes, mitochondria, and a Golgi complex - Nissl bodies - cytoskeleton contains neurofibrils microtubules
motor neuron (efferent)
convey action potentials away from the CNS to effectors (muscles and glands) in the periphery (PNS) through cranial or spinal nerves - Motor neurons are multipolar in structure.
somatic nervous system
convey output from CNS to skeletal muscles only - voluntary
autonomic nervous system
convey output from the CNS to smooth muscle, cardiac muscle, and gland - involuntary - divided into sympathetic, parasympathetic, and enteric nervous systems
sensory division of the PNS
conveys input into the CNS from sensory receptors in the body - somatic senses (tactile, thermal, pain, and proprioceptive sensations) - special senses (smell taste, vision, hearing , equilibrium)
where does glycolysis occur?
cytosol
how does placement of effort and load affect strength and range of motion?
distance between the fulcrum and load and the point at which the effort is applied determine whether a given lever operates at a mechanical advantage or a mechanical disadvantage.
smooth muscle fiber
each fiber has a single nucleus - contains thick and thin filaments but are not arranged in orderly sacromeres like skeletal muscle - thin filament attach to dense bodies instead of z-dics in skeletal - contains intermediate filaments which allows for no regular pattern of overlap making it smooth - lack transverse tubules and have only a small amount of sarcoplasmic reticulum for storage of Ca2+ rather they have caveolae
3rd class level
effort is between fulcrum and load - ex: tweezers - body ex: flexing forearm (elbow joint is fulcrum, biceps brachii is effort and weight of forearm is load) - mechanical disadvantage
sensory neurons (afferent)
either contain sensory receptors at their distal ends or are located just after sensory receptors that are separate cells. - Once an appropriate stimulus activates a sensory receptor, the sensory neuron forms an action potential in its axon and the action potential is conveyed into the CNS through cranial or spinal nerves - Most sensory neurons are unipolar in structure.
ACh function
enables muscle action, learning, and memory - slows heart rate at inhibitory synapses made by parasympathetic neurons of the vagus (X) nerve
creatine phosphate
energy-rich molecule that is found in muscle fibers - it is 3-6x more plentiful than ATP in the sacroplasm of a relaxed muscle fiber - 1st source of energy when muscle contraction begins
What sports are people with FG better at?
excel in activities that require periods of intense activity, such as weight lifting or sprinting
what muscles fibers are in shoulder and arms
fast glycolytic
symptom of ms
feeling of heaviness or weakness in the muscles, abnormal sensations, or double vision - sometimes sumptoms will disapair then come back after ayear
sodium-potassium pump
for every 2 K+ entering cell 3 Na+ leave cell - needs ATP
slow axonal transport
from the cell body toward the axon terminals. -Slow axonal transport supplies new axoplasm to developing or regenerating axons and replenishes axoplasm in growing and mature axons.
neural circuits
functional groups of neurons that process specific types of information
nodes of Ranvier
gaps in the myelin sheath
nerve fiber
general term for any neuronal process (extension) that emerges from the cell body of a neuron.
mechanical advantage
if the load is closer to the fulcrum and the effort is further from the fulcrum - only a small effort is required to move a large load over small distance - ex: using ur back to chew
resting state of AP
inactivation gate of voltage-gated Na+ is open but the activation gate is closed so Na+ cannot move into the cell and K+ voltage gated channel is closed - Na+ and K+ leak channels are open and Na+ K+ pump is open
sympathetic nervous system
increase heart rate - exercise or emergence action (flight or fright) - smooth muscle, cardiac muscle, and gland
GABA
inhibitory neurotransmitters. - At many synapses, the binding of GABA to ionotropic receptors opens Cl− channels - found only in the CNS, where it is the most common inhibitory neurotransmitter.
ms treatment
injections of beta-interferon. This treatment lengthens the time between relapses, decreases the severity of relapses, and slows formation of new lesions in some cases.
lever
a rigid structure that can move around a fixed point - ex: bone - is acted n at 2 different points by 2 different forces
parallel after-discharge circuit
a single presynaptic cell stimulates a group of neurons, each of which synapses with a common postsynaptic cell. -last neuron exhibits multiple EPSPs or IPSPs. -used in math
creatine
a small, amino acid-like molecule that is synthesized in the liver, kidneys, and pancreas and then transported to muscle fibers.
synaptic cleft
a space of 20-50 nm* that is filled with interstitial fluid.
suprathreshold
a stimulus that is strong enough to depolarize the membrane above threshold - AP occurs
post synaptic potential
a type of graded potential determined by chemical signal received
chemical synapse
a type of synapse at which a chemical (a neurotransmitter) is released from the axon of a neuron into the synaptic cleft, where it binds to receptors on the next structure (either another neuron or an organ)
subthreshold
a weak depolarization that cannot bring the membrane potential to threshold. - AP doesnt occur
all or none principle
action potential either occurs completely or it does not occur at all.
muscle action potential
action potential in a muscle fiber
electrical synapse
action potentials (impulses) conduct directly between the plasma membranes of adjacent neurons through structures called gap junctions - ions flow from one cell to the next through the connexons (tubes in cytosol), the action potential spreads from cell to cell. - found in smooth muscle, cardiac muscle, developing embryo, and brain
axon hillock
joins cell body to axon
myelin sheath
multilayered lipid and protein covering around some axons that electrically insulates the axon of a neuron and increases the speed of nerve impulse -
depolarizing phase of AP
negative membrane potential becomes less negative, reaches zero, and then becomes positive - both the activation and inactivation gates in the channel are open and Na+ inflow begins brining membrane to 30 mV
axon
propagates nerve impulses toward another neuron, a muscle fiber, or a gland cell. - contains mitochondria, microtubules and neurofibrils
strength training
refers to the process of exercising with progressively heavier resistance for the purpose of strengthening the musculoskeletal system
Krebs cycle
second stage of cellular respiration, in which pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions
what muscles fibers are are in leg
slow oxidative and fast oxidative glycolytic
parasympathetic nervous system
slows heart rate - rest and digest activities - smooth muscle, cardiac muscle, and gland
microglial cells
small cells with slender processes that give off numerous spinelike projections -function as phagocytes (they remove cellular debris formed during normal development of the nervous system and phagocytize microbes and damaged nervous tissue)
caveolae
small pouchlike invaginations of the plasma membrane - contain extracellular Ca2+ that can be used for muscular contraction.
difference between smooth muscle and other types
smooth muscle can both shorten and stretch to a greater extent than the other muscle types.
cardiac muscle tissue
specialized muscle tissue found only in the heart wall
fast glycolytic fibers
speed of development of maximum tension: fastest Rate of ATP hydrolysis by myosin ATPase: fast Diameter: largest Contraction duration: short Ca2+ -ATPase activity in SR: high Endurance: easily fatigue Metabolism: glycolytic: more anaerobic than fast-twitch oxifative glycolytic Capillary density: low Mitochondria: few Color: pale (white) order of recruitment: 3rd location where fibers are abundant: extraocular muscles primary functions of fibers: rapid intense movements of short duration
astrocytes
star shaped cells - largest and most numerous neuroglia -protoplasmic astrocytes (short branches/gray matter) -fibrous astrocytes (long unbranched/white matter)
oxygen debt
the added oxygen, over and above the resting oxygen consumption, that is taken into the body after exercise. - This extra oxygen is used to "pay back" or restore metabolic conditions to the resting level in three ways
trigger zone
the junction between the axon hillock and the initial segment
GABA function
used for antianxiety drugs ex: opioids --> hyperpolarize GABA --> dopamine release
fast axonal transport
uses proteins that function as "motors" to move materials along the surfaces of microtubules of the neuron's cytoskeleton. - Fast axonal transport moves materials in both directions—away from and toward the cell body - anterografe ( cell body-axon terminal) - retrograde (axon terminal to cell body to be recycles)
impact of epilepsy
They are initiated by abnormal, synchronous electrical discharges from millions of neurons in the brain, perhaps resulting from abnormal reverberating circuits - As a result, lights, noise, or smells may be sensed when the eyes, ears, and nose have not been stimulated.
Nissl bodies
free ribosomes and prominent clusters of rough endoplasmic reticulum - new produced proteins from nissl bodies are used to replace cellular components like material for growth of neurons and to regenerate damaged axons in the PNS
how is the brain and spinal cord connect?
foramen magnums of the occipital bone
visceral smooth muscle tissue
found in skin and in tubular arrangements that form part of small arteries and veins and of hollow organs such as the stomach intestine, uterus, and urinary bladder - like cardiac it is autorhythmic - mucles fibers are connected by gap junctions
1st class lever
fulcrum is between the effort and load - ex: scissor and seesaw - body ex: head resting on vertebral column (when head is raised it contracts the neck providing effort, fulcrum is atlantooccipital joint, and load is weight of skull) - produce mechanical advantage or disadvantage
unipolar neuron
have dendrites and one axon that are fused together to form a continuous process that emerges from the cell body - sensory receptors - trigger zone is junction of dendrities and axon - ganglia of spinal and cranial nerves
bipolar neurons
have one main dendrite and one axon - eye, inner ear, olfactory area of brain
multipolar neurons
have several dendrities and one axon - brain, spinal cord, and motor neurons
what does the strength of contraction depend on?
how many motor units are activated and the size of the motor units
presynaptic neuron
nerve cell that carries a nerve impulse toward a synapse. - converts an electrical signal (nerve impulse) into a chemical signal (released neurotransmitter).
relative refractory period
period of time during which a second action potential can be initiated, but only by a larger-than-normal stimulus - hyperpolarization
neurons
possess electrical excitability (ability to respond to a stimulus and convert it into an action potential) - very in size and shape (some cover long/short distances)
simple series circuit
presynaptic neuron stimulates a single postsynaptic neuron. The second neuron then stimulates another, and so on.
summation
process by which graded potentials add together - 2 hyperpolarizing join together the result is hyperpolarizing but if 1 hyperpolarizing and depolarizing then the signal is cancled out
how is signal intensity determined?
signal frequency: A light touch generates a low frequency of action potentials and less sensory neurons recruited
Saltatory Conduction
the special mode of action potential propagation that occurs along myelinated axons, occurs because of the uneven distribution of voltage-gated channels. - there are few voltage-gated channels in regions where myelin is present but at Nodes of Ranvier there is lots of voltage-gated channels so AP jumps node to node and occurs faster
Exercise induced muscle damage
-After intense exercise electron micrographs reveal considerable muscle damage including torn sarcolemmas in some muscle fibers, damaged myofibrils, and disrupted Z discs. -Blood levels of proteins normally confined only to muscle (including myoglobin and the enzyme creatine kinase) increase as they are released from damaged muscle
temporal summation
1 presynpatic neuron fires frequently to post and sum fast enough to reach threshold
ganglion
A collection of neuron cell bodies outside the CNS
EPSP (excitatory postsynaptic potential)
A depolarizing postsynaptic potential i
IPSP (inhibitory postsynaptic potential)
A hyperpolarizing postsynaptic potential
Treatment of Myasthenia gravis
Anticholinesterase drugs such as pyridostigmine (Mestinon) or neostigmine, the first line of treatment, act as inhibitors of acetylcholinesterase, the enzyme that breaks down ACh (raise the level of ACh that is available to bind with still‐functional receptors) - More recently, steroid drugs such as prednisone have been used with success to reduce antibody levels. - Another treatment is plasmapheresis, a procedure that removes the antibodies from the blood - Often, surgical removal of the thymus (thymectomy) is helpful.
how does smooth muscle contract?
As a smooth muscle fiber contracts, it rotates as a corkscrew turns. The fiber twists in a helix as it contracts, and rotates in the opposite direction as it relaxes.
duration of smooth muscle contract
Contraction in a smooth muscle fiber starts more slowly and lasts much longer than skeletal muscle fiber contraction
contraction period
During this time, Ca2+ binds to troponin, myosin‐binding sites on actin are exposed, and cross‐bridges form - peak tension develops in muscle fiber - 10-100 msec
NO and Viagra
In 1990s a medication was devopled to treat angina but when taking nitric oxide it actually treated eretile disfunction Vigara inhibates PDE-5 so CMP cyclic stays active longer to keep eretriction
impact of aerobic exercise
Leads to increased Muscle capillaries, Number of mitochondria, and Myoglobin synthesis -Results in greater endurance, strength, and resistance to fatigue - May convert fast glycolytic fibers into fast oxidative fibers
what happens to lactic acid produced by anaerobic glycolysis?
Most of the lactic acid produced by this process diffuses out of the skeletal muscle fiber into the blood. -Liver cells can take up some of the lactic acid molecules from the bloodstream and convert them back to glucose. - In addition to providing new glucose molecules, this conversion reduces the acidity of the blood. - When produced at a rapid rate, lactic acid can accumulate in active skeletal muscle fibers and in the bloodstream. This buildup is thought to be responsible for the muscle soreness that is felt during strenuous exercise.
refractory period
Muscle cant be stimulated when a muscle fiber receives enough stimulation to contract it loses excitability and cant be stimulated -In skeletal muscles its short (1msec) in cardiac muscle its longer (250 msec)
strength training benefits
Psychological benefits include reductions in feelings of stress and fatigue - helps to increase bone strength by increasing the deposition of bone minerals in young adults and helping to prevent, or at least slow, their loss in later life. -By increasing muscle mass, strength training raises resting metabolic rate, the amount of energy expended at rest, so a person can eat more food without gaining weight
sensory function
Sensory receptors detect internal stimuli, such as an increase in blood pressure, or external stimuli (for example, a raindrop landing on your arm). - This sensory information is then carried into the brain and spinal cord through cranial and spinal nerves.
what muscles fibers are in back and neck?
Slow oxidative fibers
fulcrum
The fixed point around which a lever pivots - ex: joint
muscle fatigue
The inability of a muscle to maintain force of contraction after prolonged activity - caused by changes within within muscle fibers
refractory period
The period of time after an action potential begins during which an excitable cell cannot generate another action potential in response to a normal threshold stimulus - only for AP not graded potential
satellite cells
These flat cells surround the cell bodies of neurons of PNS ganglia - provide structural support and regulate the exchanges of material between neuronal cell bodies and interstitial fluid
Epilepsy
characterized by short, recurrent attacks of motor, sensory, or psychological malfunction, although it almost never affects intelligence. - skeletal muscles of a person contract involuntarily
myogram
a chart of the timing and strength of a muscle's contraction
Why you breathe heavily after stopping exercise?
to payback oxygen debt (1) to convert lactic acid back into glycogen stores in the liver (2) to resynthesize creatine phosphate and ATP in muscle fibers (3) to replace the oxygen removed from myoglobin. - recovery oxygen uptake is a better term than oxygen debt for the elevated use of oxygen after exercise.
muscular tissue sources of oxygen
(1) oxygen that diffuses into muscle fibers from the blood (2) oxygen released by myoglobin within muscle fibers.
impact of anaerobic results in
- Muscle hypertrophy is growth and increase of the size of muscle cells (Due primarily to increase in fiber size) - Increased mitochondria, myofilaments, glycogen stores, and connective tissue - Increased muscle strength and size
treatment of epilepsy
- eliminated or alleviated by antiepileptic drugs, such as phenytoin, carbamazepine, and valproate sodium. - An implantable device that stimulates the vagus (X) nerve has produced dramatic results in reducing seizures in some patients whose epilepsy was not well controlled by drugs. - In very severe cases, surgical intervention may be an option.
cardiac muscle fibers vs skeletal muscle
-Have the same arrangement of actin and myosin and the same bands, zones, and Z discs as skeletal muscle fibers - however they have intercalated discs unlike skeletal muscle - in response to AP cardaic muscle tissue remains contracted 10 -15x longer than skeletal muscle (due to prolonged delivery of CA2+ into the sarcoplasm - skeletal muscle is contracted when stimulated by acetylcholine released by nerve impulse in motor neruon but cardiac muscle contracys when stimulated by its own autorhythmic muscle fibers - mitochondria in cardiac muscle fibers are larger and more numerous than skeletal muscle - cardiac muscles depends on aerobic respiration but sometimes use lacric acid produced by skeletal muscles for ATP
when is single unit vs multi-unit used?
-In small intestine cells work as multi-unit fibers to have more force to break down food -Whereas, eyes work as single unit fibers because they do not need as much force also allows for more percise movement to adjust gaze and focus eyes
lipofuscin
-a pigment that occurs as clumps of yellowish brown granules in the cytoplasm. - Lipofuscin is a product of neuronal lysosomes that accumulates as the neuron ages, but does not seem to harm the neuron.
aging and muscular tissue
-ages of 30 and 50, humans undergo a slow, progressive loss of skeletal muscle mass that is replaced largely by fibrous connective tissue and adipose tissue. - 10% muscle mass is lost due to decreased levels of physical activity - decrease in maximal strength - number of slow oxidative fiber increases due to the atrophy of other fibers or their conversion into slow oxidative fibers - 40% of muscle is lost between 50-80 - muscles in lower limbs weaken before upper limbs around age 60
how is muscle tone established
-neurons in the brain and spinal cord that excite the muscle's motor neurons - then alternating, involuntary activation of small groups of motor units in a muscle occur
removal of NT
1. Diffusion: Some of the released neurotransmitter molecules diffuse away from the synaptic cleft. 2.Enzymatic degradation: Certain neurotransmitters are inactivated through enzymatic degradation. For example, the enzyme acetylcholinesterase breaks down acetylcholine in the synaptic cleft. 3.Uptake by cells: Many neurotransmitters are actively transported back into the neuron that released them (reuptake). Others are transported into neighboring neuroglia (uptake).
peripheral fatigue
1. Inadequate release of Ca2+ from sarcoplasmic reticulum (Cross bridge wont form between actin and myosin so no contraction) 2. Depletion of creatine phosphate, oxygen, and nutrients (run out of ATP and cant power muscle contraction and cant keep doing action) - ex: Training for marathon allows body to prepare without training body will give up 3. insufficient oxygen 4. depletion of glycogen and other nutrients, buildup of lactic acid and ADP 5. failure of action potentials in the motor neuron to release enough acetylcholine.
How do these signals move through the body and connect?
1. a graded potential develops in a sensory receptor in the skin of the fingers. 2. the graded potential triggers the axon of the sensory neuron to form a nerve action potential, which travels along the axon into the CNS and ultimately causes the release of neurotransmitter at a synapse with an interneuron. 3. The neurotransmitter stimulates the interneuron to form a graded potential in its dendrites and cell body. 4. In response to the graded potential, the axon of the interneuron forms a nerve action potential. The nerve action potential travels along the axon, which results in neurotransmitter release at the next synapse with another interneuron. 5. this process occurs over and over as interneurons in higher parts of the brain (such as the thalamus and cerebral cortex) are activated. Once interneurons in the cerebral cortex, the outer part of the brain, are activated, perception occurs and you are able to feel the smooth surface of the pen touch your fingers 6.A stimulus in the brain causes a graded potential to form in the dendrites and cell body of an upper motor neuron, a type of motor neuron that synapses with a lower motor neuron farther down in the CNS in order to contract a skeletal muscle. The graded potential subsequently causes a nerve action potential to occur in the axon of the upper motor neuron, followed by neurotransmitter release. 7. The neurotransmitter generates a graded potential in a lower motor neuron, a type of motor neuron that directly supplies skeletal muscle fibers. The graded potential triggers the formation of a nerve action potential and then release of the neurotransmitter at neuromuscular junctions formed with skeletal muscle fibers that control movements of the fingers. 8. The neurotransmitter stimulates the muscle fibers that control finger movements to form muscle action potentials. The muscle action potentials cause these muscle fibers to contract, which allows you to write with the pen.
cause of epilepsy
1. brain damage at birth (the most common cause) 2. metabolic disturbances (hypoglycemia, hypocalcemia, uremia, hypoxia) 3. infections (encephalitis or meningitis); 4. toxins (alcohol, tranquilizers, hallucinogens) 5. vascular disturbances (hemorrhage, hypotension); 6.head injuries; 7. tumors and abscesses of the brain.
function of astrocyte
1. contain microfilaments that give them considerable strength, which enables them to support neurons. 2. wrapped around blood capillaries isolate neurons of the CNS from various potentially harmful substances in blood by secreting chemicals that maintain the unique selective permeability characteristics of the endothelial cells of the capillaries. - the endothelial cells create a blood-brain barrier, which restricts the movement of substances between the blood and interstitial fluid of the CNS. 3.In the embryo, astrocytes secrete chemicals that appear to regulate the growth, migration, and interconnection among neurons in the brain. 4 help to maintain the appropriate chemical environment for the generation of nerve impulses. 5. play a role in learning and memory by influencing the formation of neural synapses
what are the 3 ways muscle fibers produce atp?
1. from creatine phosphate (unique to muscle fibers as all body cells can make atp through anaerobic or aerobic) 2. anaerobic glycolysis 3. aerobic respiration
what affects speed of conduction?
1. temperature: Axons propagate action potentials at lower speeds when cooled. 2. diameter: Larger diameter axons propagate action potentials faster than smaller ones due to their larger surface areas. 3. myelination: action potentials propagate more rapidly along myelinated axons than along unmyelinated axons.
what does anaerobic glycolysis produce?
2 molecules of lactic acid and 2 molcules of ATP - gives enough energy for 2 minutes of muscle activity
what happens with ATP and creatine phosphate when contraction begins?
ADP level starts to rise - enzyme creatine kinase (CK) catalyzes the transfer of a high‐energy phosphate group from creatine phosphate back to ADP. - This direct phosphorylation reaction quickly generates new ATP molecules. - together creatine phosphate and ATP provide enough energy for muscles to contract for 15 seconds
myoglobin
An oxygen-storing, pigmented protein in muscle cells that binds to oxygen and realses it when needed
what type of communication is graded potential good more
Because they die out within a few millimeters of their point of origin, graded potentials are useful for short-distance communication only (decremental conduction)
relaxation period
Ca2+ 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. - 10-100 msec (depends on type of skeletal muscle fiber; eyes are faster than legs)
NO function
Endothelial cells in blood vessel walls release NO, which diffuses into neighboring smooth muscle cells and causes relaxation. -The result is vasodilation, an increase in blood vessel diameter. - The effects of such vasodilation range from a lowering of blood pressure to erection of the penis in males. Sildenafil (Viagra®) alleviates erectile dysfunction (impotence) by enhancing the effect of NO.
How can fibers in skeletal muscles change for endurance exercises?
Endurance‐type (aerobic) exercises, such as running or swimming, cause a gradual transformation of some FG fibers into fast oxidative-glycolytic (FOG) fibers. -The transformed muscle fibers show slight increases in diameter, number of mitochondria, blood supply, and strength. - Endurance exercises also result in cardiovascular and respiratory changes that cause skeletal muscles to receive better supplies of oxygen and
symptoms of myasthenia gravis
Initial symptoms include weakness of the eye muscles, which may produce double vision, and weakness of the throat muscles that may produce difficulty in swallowing. -Later, the person has difficulty chewing and talking. Eventually the muscles of the limbs may become involved. - Death may result from paralysis of the respiratory muscles, but often the disorder does not progress to that stage.
reverberating circuit
Some circuits are organized so that stimulation of the presynaptic cell causes the postsynaptic cell to transmit a series of nerve impulses. -incoming impulse stimulates the first neuron, which stimulates the second, which stimulates the third, and so on. - Branches from later neurons synapse with earlier ones. This arrangement sends impulses back through the circuit again and again.
axon terminal
The endpoint of a neuron where neurotransmitters are stored
integrative function
The nervous system processes sensory information by analyzing it and making decisions for appropriate responses—an activity known as integration
muscle tone
a small amount of tautness or tension in the muscle due to weak, involuntary contractions of its motor units. (seen at rest) - keeps skeletal muscles firm, but it does not result in a force strong enough to produce movement - ex: muscles in the back of the neck are in normal tonic contraction; they keep the head upright and prevent it from slumping forward on the chest
Spasm
abnormal muscular contraction -a sudden involuntary contraction of a single muscle in a large group of muscles
smooth muscle tissue
activated involuntarily - 2 types (visceral and multi-unit) - allows for food to be broken down and nutrients observed through contractions -Thick in the middle, tapered on the ends -Not striated - Autonomic neurons release multiple neurotransmittters into smooth muscle
What sports are people with more SO better at?
activities that require endurance, such as long‐distance running
peripheral nervous system
all nervous tissue out the CNS (nerves and sensory receptors) -
action potential
allow communication over long distances within the body.
stress-relaxation response
allows smooth muscle to undergo great changes in length while retaining the ability to contract effectively - When smooth muscle fibers are stretched, they initially contract, developing increased tension. Within a minute or so, the tension decreases. - this allows for content in smooth muscles like intestines not to get altered as the shape of the muscle can change to fit the content
asynchronous
alternating muscle recruitment of motor units helps avoid fatigue -Different motor units take turns maintaining tension
what do graded electrical signals vary in?
amplitude (size) depending on strength of stimulus - larger or smaller depends on how many ligand-gated or mechanically gated channels opened or closed and for how long
Nitric Oxide
an important excitatory neurotransmitter secreted in the brain, spinal cord, adrenal glands, and nerves to the penis and has widespread effects throughout the body. - contains a single nitrogen atom
ependymal cells
are cuboidal to columnar cells arranged in a single layer that possess microvilli and cilia - line the ventricles of the brain and central canal of the spinal cord
dendrites
are the receiving or input portions of a neuron. -The plasma membranes of dendrites (and cell bodies) contain numerous receptor sites for binding chemical messengers from other cells. - Dendrites usually are short, tapering, and highly branched. - their cytoplasm contains Nissl bodies, mitochondria and other organelles
graded potental
are used for short-distance communication only
microtubules
assist in moving materials between the cell body and axon
Myasthenia Gravis
autoimmune disease that causes chronic, progressive damage of the neuromuscular junction. - The immune system inappropriately produces antibodies that bind to and block some ACh receptors, thereby decreasing the number of functional ACh receptors at the motor end plates of skeletal muscles - As the disease progresses, more ACh receptors are lost. Thus, muscles become increasingly weaker, fatigue more easily, and may eventually cease to function. - more common in women (onset from 20-40 vs men is 50-60) - muscles of face and neck are most effected
central nervous system
brain and spinal cord - processes many different kinds of incoming sensory information - source of thoughts, emotions, and memories - signals for muscles to contract and glands to secrete
cause of ms
cause of MS is unclear, both genetic susceptibility and exposure to some environmental factor (perhaps a herpes virus) appear to contribute.
effort
causes movement - ex: tension generated by muscle contraction
postsynaptic neuron
cell that receives a signal. - receives the chemical signal and in turn generates an electrical signal (postsynaptic potential
multi-unit smooth muscle tissue
consists of individual fibers, each with its own motor neuron terminals and with few gap junctions between neighboring fibers -Stimulation of one visceral muscle fiber causes contraction of many adjacent fibers, but stimulation of one multi‐unit fiber causes contraction of that fiber only. -Multi‐unit smooth muscle tissue is found in the walls of large arteries, in airways to the lungs, in the arrector pili muscles that attach to hair follicles, in the muscles of the iris that adjust pupil diameter, and in the ciliary body that adjusts focus of the lens in the eye.
gray matter
contains neuronal cell bodies, dendrities, unmyelinated axons, axon terminals and neuroglia - nissl bodies impart a gray color and there is little or no myelin
Continuous Conduction
continuous conduction involves step-by-step depolarization and repolarization of each adjacent segment of the plasma membrane - occurs in unmyelinated axons and muscle fibers
why are motor units not contracted in unison, rather some are relaxed while others are contracted?
delays muscle fatigue and allows contraction of a whole muscle to be sustained for long periods
electron transport chain
electrons NADH and FADH2 (from glucose oxidation) move through a series of proteins called electron transport chain (ETC) - The energy released in this chain of redox reactions is used to create a proton gradient across a memebrane; the ensuing flow of protons back across the memebrane is used to make ATP □ Oxidative phosphorylation- ATP products links the phosphorylation of ADP with oxidation of NADH and FADH2
absolute refractory period
even a very strong stimulus cannot initiate a second action potential - during depolarization and repolarization
How can fibers in skeletal muscles change for short term energy like sprints?
exercises that require great strength for short periods produce an increase in the size and strength of FG fibers. - The increase in size is due to increased synthesis of thick and thin filaments. - The overall result is muscle enlargement (hypertrophy), as evidenced by the bulging muscles of body builders.
enteric nervous system
extensive network of over 100 million neurons confined to the wall of the GI tract - helps regulate the acivitiy of smooth muscle and glands of GI tract - can function independently but communicates with and regulated by other branches of ANS
central fatigue
feelings of tiredness and the desire to cease activity - occurs before muscle fatigue in order to stop a person from exercising before muscle becomes damaged - caused by changes to he central nervous system (brain and spinal cord)
action potential
is an electrical signal that propagates (travels) along the surface of the membrane of a neuron - It begins and travels due to the movement of ions (such as sodium and potassium) between interstitial fluid and the inside of a neuron through specific ion channels in its plasma membrane.
eccentric isotonic contraction
length of a muscle increases during a contraction - tension exerted by the myosin cross-bridge resists movement of a load and slows lengthening process - more eccentric contraction causes muscle damage and more delayed onset muscle soreness
ionotropic receptors
ligand-gated channel - open ion channels and either depolarize or hyperpolarize - In the absence of neurotransmitter (the ligand), the ion channel component of the ionotropic receptor is closed - EPSPs result from opening these cation channels (Na+, K+ and Ca+enter) - IPSP (Cl- enter)
2nd class lever
load is between fulcrum and effort - ex: wheelbarrow - body ex: standing one toes, fulcrum is ball of foot and load it weight of body and effort is contraction of calf muscle - mechanical advantage
mechanical disadvantage
load is further from the fulcrum so a large effort is required to move a small load but at a greater speed - lots of speed and range of motion but cant hold a lot of load and little strength - ex: using front teeth to chew
interneuron (association)
mainly located within the CNS between sensory and motor neurons -Interneurons integrate (process) incoming sensory information from sensory neurons and then elicit a motor response by activating the appropriate motor neurons. -Most interneurons are multipolar in structure.
schwann cell
many cells with 1 axon - form the myelin sheath around a single axons - partake in axon regeneration - begin to form myelin sheaths around axons during fetal development.
synaptic vesicles
membrane includes sacs that contain neurotransmitters which either excite or inhibit another neuron muscle fiber or gland cell
repolarizing phase of AP
membrane potential is restored to the resting state of −70 mV - inactivation gate of voltage gated Na+ channel closes and voltage gated K+ channels open and K+ leaves the cell
hyperpolarizing phase of AP
membrane potential temporarily becomes more negative than the resting level. - voltage-gated K+ channels are open, outflow of K+ - inactivation Na+ voltage gate is open but activation gate is closed
intercalated discs
microscopic structures are irregular transverse thickenings of the sarcolemma that connect the ends of cardiac muscle fibers to one another. - The discs contain desmosomes (which hold the fibers together) and gap junctions (which allow muscle action potentials to spread from one cardiac muscle fiber to another)
impact of MS
multiple regions the myelin sheaths deteriorate to scleroses, which are hardened scars or plaques - The destruction of myelin sheaths slows and then short-circuits propagation of nerve impulses.
concentric isotonic contraction
muscle shortens and pulls on another structure (tendon) to produce movement and reduce the angle at a joint
divergent circuit
nerve impulse from a single presynaptic neuron causes the stimulation of increasing numbers of cells along the circuit - permits one presynaptic neuron to influence several postsynaptic neurons
motor function
once sensory information is integrated, the nervous system may elicit an appropriate motor response by activating effectors (muscles and glands) through cranial and spinal nerves - Stimulation of the effectors causes muscles to contract and glands to secrete.
effective stretching
one should do a warm up (walking, jogging, easy swimming or easy aerobics) - Tissues stretch best when slow, gentle force is applied at elevated tissue temperatures. -An external source of heat, such as hot packs or ultrasound, may be used, but 10 or more minutes of muscular contraction is also a good way to raise muscle temperature - one shouldnt strength cold muscle bc this can cause damage
ligand-gated channel
opens and closes in response to the binding of a ligand (chemical) stimulus (NT or hormones) - located in the dendrites of some sensory neurons, such as pain receptors, and in dendrites and cell bodies of interneurons and motor neurons
voltage gated channel
opens in response to a change in membrane potential (voltage) - participate in the generation and conduction of action potentials in the axons of all types of neurons. - found in all neuron axons
mechanically-gated channel
opens or closes in response to mechanical stimulation in the form of vibration (such as sound waves), touch, pressure, or tissue stretching - The force distorts the channel from its resting position, opening the gate. - found in dendrites of auditory receptors in the ears, in receptors that monitor stretching of internal organs, and in touch receptors and pressure receptors in the skin.
motor division of PNS
output from CNS to effectors (muscles/glands) - divided into somatic and autonomic nervous system
leak channels
randomly alternate between open and closed positions - plasma membranes have many more potassium ion (K+) leak channels than sodium ion (Na+) leak channels (the membrane's permeability to K+ is much higher than its permeability to Na+) - found in all cells
load
resistance that opposes movement - ex: weight of object
depolarizing graded potential
response makes the membrane less polarized (inside less negative) - excitatory
hyperpolarizing graded potential
response makes the membrane more polarized (inside more negative) -inhibitory
resting membrane potential
small buildup of negative ions in the cytosol along the inside of the membrane, and an equal buildup of positive ions in the extracellular fluid (ECF) along the outside surface of the membrane - greater the difference in charge across membrane larger the membrane potential (voltage)
graded membrane potential
small deviation from the resting membrane potential that makes the membrane either more polarized (inside more negative) or less polarized (inside less negative). - occurs when a stimulus causes mechanically-gated or ligand-gated channels to open or close in an excitable cell's plasma membrane - takes place in dendrites and cell body of neuron
oligodendrocytes
smaller than astrocytes -responsible for forming and maintaining myelin sheath around CNS axons - A single oligodendrocyte myelinates several axons,
neuroglia
smaller than neurons, and they are 5 to 25 times more numerous. - can be multiplied and divided - do not form AP -CNS (atrocytes, oligodendrocytes, microlgial cell, ependymal cells) -PNS (Schawnn and satellite cell)
fast oxidative glycolytic fibers
speed of development of maximum tension: intermediate Rate of ATP hydrolysis by myosin ATPase: fast Diameter: medium Contraction duration: short Ca2+ -ATPase activity in SR: high Endurance: fatigue resistance Metabolism: glycolytic but becomes more oxidative with endurance training Capillary density: medium Mitochondria: moderate Color: dark red (light pink) order of recruitment: second location where fibers are abundant: lower limbs primary functions of fibers: walking/sprinting
slow oxidative fibers
speed of development of maximum tension: slowest Rate of ATP hydrolysis by myosin ATPase: slow Diameter: small Contraction duration: longest Ca2+ -ATPase activity in SR: moderate Endurance: fatigue resistance Metabolism: oxidative; aerobic Capillary density: high Mitochondria: numerous Color: dark red (myoglobin) order of recruitment: first location where fibers are abundant: postural muscles (neck) primary functions of fibers: maintianing posture and aerobic endurance activities
converging circuit
the postsynaptic neuron receives nerve impulses from several different sources.
wave summation
stimuli arriving at different times cause larger contractions, - when action potential is doubled in short amount of time (must be sent before refractory period) - 2nd stimulus is stronger than 1st
sensory receptor
structure of the nervous system that monitors changes in the external or internal environment - touch receptors in the skin, photoreceptors in the eye, olfactory receptors in the nose - divides into sensory and motor division
unfused (incomplete) tetanus
sustained but wavering contraction as muscle only partically relaxes - lots of ap is sent - Allows for strong force to carry heavy thing - 20- 30 times per second muscle is stimulated
what is excess ATP from a relaxed muscle used for?
synthesize creatine phosphate
isotonic contraction
tension (force of contraction) of muscle remains constant while muscle changes its length - used for body movements and moving objects - concentric and eccentric
isometric contraction
tension generated is not enough to exceed the resistance of the object to be moved and muscle does not change length - ex: holding book steady or yoga pose
Metabotropic receptors
type of neurotransmitter receptor that contains a neurotransmitter binding site but lacks an ion channel as part of its structure. - is coupled to a separate ion channel by a type of membrane protein called a G protein. -When a neurotransmitter binds to a metabotropic receptor, the G protein either directly opens (or closes) the ion channel or it may act indirectly by activating another molecule, a "second messenger," in the cytosol, which in turn opens (or closes) the ion channel - K+ flows out
motor unit recruitment
weakest motor units are 1st, then stronger motor units are added if the task requires more force - recruitmnet is responisble for producing smooth movments - when precise movemnts are needed smaller muscles and motor units are used whereas large units are activated when a large amount is tension is needed
fused (complete) tetanus
when muscle fiber does not relax at all - sustained contraction in which individual twitches cannot be detected - muscle fiber is stimulated at rate of 80-100 times per second - happens rarely like lifting a car - prolonged= muscle fatigue
what causes motion?
when the effort applied to the bone at the insertion exceeds the load.
