BIOL2273: Anatomy and Physiology 1 Exam 3 (Ch. 9,11,13, & 12)
What is step 4 of the process of neuromuscular junction action potentials?
ACh diffuses across the synaptic cleft and binds to ligand-gated Na+ channels on the postsynaptic membrane (blue)
How do slow-twitch muscle fibers split ATP?
slowly -long distance runner -aerobic exercise develops slow-twitch
For muscle relaxation, what does the cessation of action potentials along the sarcolemma stop?
stops Ca2+ release from the sarcoplasmic reticulum and so Ca2+ is actively transported back into the sarcoplasmic reticulum (ATP is used)
What is Rigor mortis? What causes it?
Stiff muscles after death -results from inadequate amounts of ATP -build up of Ca2+ in muscle cell, inadequate ATP
What forms when myosin binds to actin?
a cross-bridge -the globular head of myosin attaches to an actin filament
Why do myofibrils appear striated? *****
because of A bands (anisotropic) and I bands (isotropic) -banded, striated appearance
Extra notes- watch animation on function of neuromuscular junction
http://highered.mheducation.com/sites/0072495855/student_view0/chapter10/animation__function_of_the_neuromuscular_junction__quiz_1_.html
What is the structure of receptor protein molecules in synapses?
membrane bound
What is the function of the protein myoglobin in skeletal muscle fibers?
oxygen transporter
Mitochondria, myofibrils, and energy-storing glycogen granules constitute the cytoplasm of the muscle, which is called what? *****
sarcoplasm -plasma membrane is called sarcolemma
How long does Anaerobic Respiration provide energy for? For what type of exercise?
short time during intense exercise
How long does Creatine Phosphate reacted with ADP provide energy for? For what type of exercise?
short time during intense exercise
What does the Power Stroke cause?
shortening of the sarcomeres
What causes Saltatory Conduction to occur, where the action potential jumps from node to node on a myelinated axon?
(V) gated Na+ channels are highly concentrated at the nodes of Ranvier--- so the local current quickly flows to a node and stimulates the (V) gated Na+ channels to open, resulting in the production of an action potential -lipids within the membranes of the myelin sheath on the cells act as a layer of insulation, forcing the local currents to flow from one node of Ranvier to the next, over the membranes
Extra notes on Neuromuscular Transmission
-Action potential arrives at axon terminal or presynaptic terminal -(V) gated Ca2+ channels open -Increased permeability to Ca2+ ion -Extracellular Ca2+ enters the axon terminal or presynaptic terminal -Vesicles release ACh into synaptic cleft via exocytosis (use ATP) -ACh binds to receptors on motor end plate or ligand-gated Na+ channels on the postsynaptic membrane -Ligand-gated Na+ channels open (increased permeability to Na+) -Once (V) gated channels take over as a cell reaches threshold, an action potential occurs in the sarcolemma -ACh is degraded by ACh estrase
How are receptors involved to a particular neurotransmitter?
-Highly specific (Adrenergenic only responds to Ne and Cholinergenic only responds to ACh) -At some sites, a neurotransmitter's receptors may be excitatory (always Cholinergenic) but at other sites they may be inhibitory (Adrenergenic can be either)
Describe smooth muscles
-Less actin and myosin -Tropomyosin present -No troponin -Myofilaments are organized into bundles (not sarcomeres)- no striations -One nucleus -No T-tubules -Involuntary -Gap junctions present -Can undergo hyperplasia (increase in # of cells)
What does a multipolar neuron consist of?
-Many dendrites -One axon -Cell body/soma
What is the difference between a neuron and a neuroglia?
-Neurons are cells of the nervous system; They transmit impulses from one part of the body to another -Neurons are amitotic, so they do NOT divide -Neurons release neurotransmitters -Neuroglia are cells that protect, insulate, and support the neurons -Neuroglia divide
What does a pseudo-unipolar neuron consist of?
-No dendrite -One axon (one extension that acts like an axon and a dendrite because it still conducts action potentials towards the neuron cell body) -Cell body/soma
What does a bipolar neuron consist of?
-One dendrite -One axon -Cell body/soma
How are neurons (nerve cells) functional, organized, and reacted?
-Receive stimuli and transmit action potentials -Organized into complex networks -Excitable (able to generate action potentials) and amitotic (do not divide) with high metabolic rates---needs voltage gated Na+ channels (ligand/chemical eventually close so has to be voltage)
A stimulus of increasing frequency increases the force of contraction, called multiple-wave summation. What does this mean?
-Relaxation is not required -Action potential is completed long before contraction -Multiple-wave summation continues until a period of sustained contraction
Describe cardiac muscles
-Striated (have sarcomeres) -Single centrally located nucleus -Intercalated discs and gap junctions present -Involuntary -Auto rhythmic
Axons terminate at highly branched extensions (have branches on the end). What are the branches called?
-Telodendria
What happens to the I Band, H Zone, and A Band during contraction?
-The I Band (only actin- on ends) and H Zones (only myosin) become narrower -The A Band (length of myosin myofilament) remains constant in length
What is required for each cycle of cross-bridge formation, movement, and release?
1 ATP molecule
What are the three components of the actin myofilament?
1. A double helix of F actin -two strands of fibrous actin 2. Tropomyosin molecules 3. Troponin molecules (TnI, TnT, and TnC)
The cell body (soma) of a neuron contains what? Why? (contains two things)
1. A single, large, centrally located nucleus with a prominent nucleolus (in the middle of the nucleus) -used to transfer DNA 2. Lots of rough ER (called Nissl bodies) -used for protein synthesis ---Nissl bodies are the primary site of protein synthesis in neurons
What are the two major protein fibers, called myofilaments, that compose myofibrils in the sarcoplasm? *****
1. Actin (thin) 2. Myosin (thick) -myofibrils extend from one end of the muscle fiber to the other
Explain the steps of the lag/latent phase of a muscle twitch.
1. Action potential arrives at axon terminal or pre-synaptic terminal 2. (V) gated Ca2+ channels open 3. Increased permeability to Ca2+ 4. Extracellular Ca2+ enters presynaptic or axon terminal 5. Vesicles release ACh into cleft via exocytosis (use ATP) 6. ACh binds to receptors on motor end plate or sarcolemma 7. Ligand gated Na+ channels open 8. Increased permeability to Na+ 9. Once (V) gated Na+ channels take over and cell reaches threshold action potential occurs in sarcolemma 10. ACh is degraded by ACh-esterase 11. Action potential propagated across sarcolemma 12. When it reaches the T tubule it triggers the release of stored intracellular Ca2+ from the terminal cisternae of the sarcoplasmic reticulum by opening (V) gated Ca2+ channels 13. Ca2+ binds to troponin C 14. The tropomyosin-troponin complex changes shape, exposing the active sites on actin
What are the seven steps of the process of cholinergic synapse action potentials?
1. Action potential arrives at synapse (at end of axon), depolarizing the presynaptic membrane 2. (V) gated Ca2+ ions enter the presynaptic terminal- increased permeability to Ca2+ 3. ACh is released from presynaptic terminal by exocytosis 4. ACh binds to postsynaptic membrane receptors 5. Ligand-gated Na+ channels open on postsynaptic membrane, causing depolarization (possible action potential if meet threshold) 6. No more ACh released once Ca2+ ions are removed from presynaptic terminal 7. ACh at postsynaptic membrane is broken down (by synaptic cleft) by ACh-estrase into acetic acid and choline -Choline is transported back to presynaptic membrane to reform ACh -Acetic acid may also be reabsorbed by presynaptic membrane, or it may diffuse away and be used elsewhere in the body
What are the seven steps of the process of adrenergic synapse action potentials?
1. Action potential arrives at synapse, depolarizing the synaptic membrane--increased permeability to Ca2+ 2. Ca2+ ions enter, triggering release of norepinephrine (first messenger) into the synaptic cleft 3. Norepinephrine binds to receptors on the postsynaptic membrane 4. Norepinephrine binding leads to a series of events resulting in activation of adenylyl cyclase, which converts intracellular ATP to cyclic AMP (second messenger) 5. Cyclic (active- occurs in cycles) AMP activates an enzyme that opens ligand-gated Na+ channels (in an excitatory response), allowing influx of Na+ ions which depolarizes postsynaptic membrane 6. Phophodiestrase converts cyclic AMP to inactive AMP at the postsynaptic membrane 7. Norepinephrine unbinds from the receptor and may: -diffuse away from the site and get into circulation, where it may be inactivated in the bloodstream or the liver -(most) be reabsorbed through the presynaptic membrane, where it may be repackaged into synaptic vesicles for reuse OR may be inactivated by the enzyme MAO (monoamine oxidase) Two messengers: Norepinephrine (1st) and cAMP (2nd) -adenylyl cyclase enzyme turns ATP (adenosine triphosphate) into cAMP (cyclic (active) adenosine monophosphate)
What are the two major types of synapses?
1. Adrenergic 2. Cholinergic
What are the two functional subdivisions of the PNS? (opposites)
1. Afferent (sensory): sends action potentials from the sensory receptors towards the CNS -pain is good for sensory 2. Efferent (motor): sends action potentials from the CNS towards the sensory effectors (away from CNS) -motor sends towards neurons
Extra notes on summary of skeletal muscle contraction
1. An action potential travels along an axon membrane to a neuromuscular junction 2. Ca2+ channels open and Ca2+ enters the presynaptic terminal 3. ACh is released from presynaptic vesicles 4. ACh stimulates Na+ channels on the postsynaptic membrane to open 5. Na+ diffuses into the muscle fiber, initiating an action potential that travels along the sarcolemma and T tubule membranes 6. Action potentials in the T tubules cause the sarcoplasmic reticulum to release Ca2+ 7. On the actin, Ca2+ binds to troponin, which moves tropomyosin and exposes myosin head attachment sites 8. ATP molecules on myosin heads are broken down to ADP and P, which releases energy needed to move the myosin heads 9. The heads of the myosin myofilaments bend, causing the actin to slide past the myosin. As long as Ca2+ is present, the cycle repeats
What three things can nerve cells communicate with?
1. Another nerve cell 2. An effector (acts in response to stimulus) 3. A sensory receptor cell (receives chemical signals)
What are the four types of neuroglial cells in the CNS?
1. Astrocytes 2. Ependymal Cells 3. Microglia 4. Oligodendrocytes
Where is gray matter,consisting of groups of neuron cell bodies and their dendrites, located in the CNS? (two places) What about in the PNS?
1. CNS: on the brain's surface (the cortex) and deep in the brain (the nuclei) -so neuron cell bodies located deep in the brain are called nuclei 2. PNS: in clusters called ganglia (structures of neuron cell bodies) -so neuron cell bodies located in clusters in the PNS are called ganglia
What are the three parts of a neuron?
1. Cell body/ soma 2. Axons 3. Dendrites
Although humans only have one nervous system, what are the two subdivisions of the nervous system?
1. Central Nervous System (CNS) 2. Peripheral Nervous System (PNS)
What three things can cause muscle fatigue?
1. Central nervous system (psychological) 2. Depletion of ATP in muscles (muscular) 3. Depletion of ACh (synaptic) in neuromuscular junction
What are the two different types of isotonic contractions, ones that change muscle length?
1. Concentric contractions: cause muscles to shorten 2. Eccentric contractions: cause muscle length to increase/ stretch
What three things are skeletal muscle fibers associated with?
1. Connective tissue 2. Nerves 3. Blood vessels
What are the four major functional properties of muscle tissue, which is highly specialized? *****
1. Contractility 2. Excitability 3. Extensibility 4. Elasticity
Information passes from neuron to neuron through organized pathways or circuits. What are the three basic patterns?
1. Convergent: many neurons synapsing and sending info to one or a few neurons 2. Divergent: one or a few neurons sending info to many neurons and synapsing 3. Oscillating: one or two neurons communicate with each other by collateral branches of axons
What are the three sources that produce the energy required to make ATP?
1. Creatine Phosphate 2. Anaerobic Respiration 3. Aerobic Respiration
Explain the steps of the contraction phase of a muscle twitch.
1. Cross-bridges form between actin and myosin 2. Myosin heads pivot towards the M-line, sliding the actin over the myosin (POWER STROKE) 3. Sarcomeres shorten 4. ATP binds to myosin heads and is broken down to ADP and P+. This energy releases the cross-bridge and myosin heads return to a resting position (RECOVERY STROKE)
What four things does the A band include?
1. Entire length of myosin myofilament 2. Zone of overlap of actin and myosin myofilaments -includes actin and myosin myofilaments 3. H-zone 4. M-line
What are the four functions of astrocytes? (CNS)
1. Form supporting frameworks for blood vessels and neurons- foot processes cover 2. Promote formation of tight junctions (a type of connection between cell membranes) between capillaries (the blood-brain barrier) -blood-brain barrier determines what substances can pass from the blood into the nervous tissue of the brain and spinal cord 3. Aid responses to injury (scar-forming) 4. Promote and regulate synapse formation (release chemicals that do so)
Axons transport substances in what two ways, provide examples?
1. From cell body to axon terminals (ex. ACh) 2. From axon to cell body (ex. acetic acid and choline) -movement of materials within axon is necessary for its normal function (good) -provides a way for infectious agents and harmful substances to be transported from the periphery to the CNS (bad)
Extra notes
1. I Band: Only Actin myofilaments- extends from sides of Z lines to ends of myosin 2. A Band: Extends length of entire Myosin myofilament- both myosin and actin at zone of overlap- contains H-zone and M-line 3. H-Zone: Only Myosin 4. M-Line: Center of H-zone- links Myosin myofilaments
What are the two types of fast-twitch fibers?
1. IIa: well-developed blood supply, more mitochondria, more myoglobin than IIb 2. IIb: lots of glycogen, less of all three others
What are the two types of tetanus?
1. Incomplete tetanus: partial relaxation between contractions 2. Complete tetanus: no relaxation between contractions
Explain the steps of the relaxation phase of a muscle twitch.
1. Intracellular Ca2+ ions are actively transported into the sarcoplasmic reticulum (ATP used) 2. The troponin-tropomyosin complex re-established its position 3. This inhibits cross-bridge formation 4. The muscle fiber lengthens passively
What is the difference between Isometric contractions and Isotonic contractions?
1. Isometric contractions: cause a change in muscle tension but no change in muscle length 2. Isotonic contractions: cause a change in muscle length but no change in muscle tension Isometric- change tension Isotonic- change length
What are the three phases of a muscle twitch? *****
1. Lag/Latent Phase: time between the application of the stimulus to the motor neuron and the beginning of contraction 2. Contraction Phase: time during which contraction occurs 3. Relaxation Phase: time during which relaxation occurs
What are the three structural classifications of neurons?
1. Multipolar 2. Bipolar 3. Pseudo-unipolar
Extra notes on General Properties of Muscle
1. Muscle exhibits -contractibility (shortens forcefully) -excitability (responds to stimuli) -extensibility (can be stretched and still contract) -elasticity (recoils to resting length) 2. Muscle tissue shortens forcefully but lengthens passively 3. There are three types of muscle tissue (skeletal, smooth, cardiac)
Cytoplasmic extensions from Oligodendrocytes in the CNS and Schwann Cells in the PNS surround axons to form what two types of axons?
1. Myelinated axons 2. Unmyelinated axons
What are myelinated axons in the CNS known as? What are myelinated axons in the PNS known as? (make up the bundles of white matter in nervous tissue)
1. Myelinated axons in the CNS are known as nerve tracts 2. Myelinated axons in the PNS are known as nerves -these make up bundles of white matter
What does the PNS consist of? (four things)
1. Nerves (axons and their sheaths- extend through-out the body) 2. Sensory receptors (endings of neurons- detect senses and other stimuli) 3. Ganglia (bunch of cell bodies outside the CNS) 4. Plexuses (extensive network of neuron cell bodies)
Many synapses have the axon of one neuron synapse with the presynaptic terminal of another neuron. One neuron can release a neuromodulator that influences the release of a neurotransmitter from the presynaptic terminal of another neuron. How many neurotransmitters are released for presynaptic inhibition and presynaptic facilitation?
1. Neurotransmitter release is lessened for presynaptic inhibition -enkaphalins and endorphins released from inhibitory neurons can reduce pain sensations by inhibiting the release of neurotransmitters from the presynaptic terminals of sensory neurons -less stimulation 2. Neurotransmitter release is increased for presynaptic facilitation -more stimulation
A muscle fiber is a single cell consisting of what? (5 components)
1. Plasma membrane (sarcolemma) 2. Cytoplasm (sarcoplasm) 3. Several nuclei 4. Myoglobin 5. Myofibrils
What three things compose a synapse?
1. Presynaptic terminal -contains ACh (a neurotransmitter) 2. Synaptic cleft -contains ACh-estrase (breaks down ACh into acetyl acid and choline) 3. Post-synaptic terminal -contains receptors for ACh -is the sarcolemma (membrane)
What are the three functions of Satellite Cells?
1. Provide support 2. Nutrition 3. Protection from poisoning by absorbing the poison and reducing their access to the neuron cell bodies
What are the five functions of the Nervous System? (Ch. 11)
1. Receiving sensory input from numerous internal (hormones) and external (environment) stimuli -unconscious level 2. Information processing (integration) and initiation of responses -making sense of the info -brain and spinal cord are major organs for this 3. Controlling muscles and glands (releasing hormones) -only contract when stimulated by the nervous system 4. Maintaining homeostasis -cells work together -nervous system can stimulate or inhibit these activities 5. Establishing and maintaining mental activity -brain is the center of all mental activity (memory, thinking, emotions, etc.)
What are the two neuroglial cells of the PNS?
1. Schwann Cells 2. Satellite Cells -PNS have the two S's, CNS has no S's
What are the three types of neurons and where do they conduct action potentials?
1. Sensory (afferent) neurons: conduct action potentials toward the CNS (from the sensory receptors) 2. Motor (efferent) neurons: conduct action potentials from the CNS (to the sensory effectors) 3. Interneurons: conduct action potentials within the CNS (from one neuron to another) -neurons are functionally classified based on their direction of information transmission
What are the three types of muscle tissue and which is the most abundant? (Ch.9)
1. Skeletal (Most abundant and most studied) 2. Smooth 3. Cardiac
What are the two types of muscle fibers?
1. Slow-Twitch 2. Fast-Twitch (IIa and IIb)
What are the two subdivisions of the Efferent (motor) system of the PNS?
1. Somatic: Voluntary -to skeletal muscles 2. Autonomic: Involuntary -to glands (automatically does it)
What are the two ways a stimulus results in graded contractions, meaning the strength of muscle contractions vary from weak to strong?
1. Summation: Involves increasing the force of contraction of the muscle fibers within the muscle 2. Recruitment: Involves increasing the number of muscle fibers contracting recruitment- increasing number
What are the three types of troponin, a component of the actin myofilament, and what do they bind to?
1. TnI: Binds to Actin 2. TnT: Binds to Tropomyosin 3. TnC: Binds to Calcium
What are the two components of the myosin myofilament?
1. Two globular heads -four light myosin chains are attached to the heads of each myosin molecule 2. Rod-like portion -two myosin heavy chains that wound together to form rod portion -looks like a golf club
What are the three important properties of the myosin heads?
1. heads can bind to active sites on actin molecules to form cross-bridges 2. heads are attached to the rod portion by a hinge region that can bend and straighten during contraction 3. the heads are ATPase enzymes, which break down ATP, releasing energy -part of the energy is used to bend the hinge region of the myosin molecule during contraction
What is the maximum number of cells for a motor unit?
5 cells per axon
What is a synapse?
A structure that permits a neuron to pass an electrical or chemical signal to another neuron
What is step 9, the last step, of the process of neuromuscular junction action potentials?
ACh is reformed within the presynaptic terminal using acetic acid generated from metabolism and from choline recycles from the synaptic cleft. ACh is then taken up by synaptic vesicles.
What is step 3 of the process of neuromuscular junction action potentials?
ACh is released into the synaptic cleft by exocytosis (uses ATP)
What is step 6 of the process of neuromuscular junction action potentials?
ACh unbinds from the ligand-gated Na+ channels, which then close
Where does energy for muscle contraction come from?
ATP -immediate source of energy for muscle contraction -as long as adequate amounts of ATP are present, muscles can contract repeatedly for a long time
What happens after the Power Stroke, the movement of the myosin molecule while the cross-bridge is attached?
ATP binds to myosin heads, which releases the cross-bridge. Then ATP is broken down to ADP and P (phosphate), releasing energy that returns the myosin head to its pre-powerstroke position (RECOVERY STROKE) -recovery stroke is the return of the myosin head to its original position after cross-bridge release
How is ATP produced by Aerobic Respiration?
ATP is produced more efficiently but slowly
ATP is also required for what during cross-bridge formation?
ATP is required to transport Ca2+ into the sarcoplasmic reticulum and to maintain normal concentration gradients across the plasma membrane
How long does Aerobic Respiration provide energy for? For what type of exercise?
ATP synthesized by aerobic respiration produces energy for muscle contractions under resting conditions or during exercises such as long distance running
How is ATP produced by Creatine Phosphate?
ATP synthesized when ADP reacts with creatine phosphate
What do the two globular heads of the myosin myofilament contain?
ATPase -breaks down ATP, releasing energy
What is contractility, one of the major functional properties of muscle tissue?
Ability of a muscle to shorten with force (shortens forcefully)
What is elasticity, one of the major functional properties of muscle tissue?
Ability of muscle to recoil to original resting length after being stretched (recoils to resting length)
What is ACh and what does it do, a molecule in synaptic vesicles of the presynaptic terminal?
Acetylcholine is a neurotransmitter -an inorganic molecule composed of acetic acid and choline -it is a substance that is released from a presynaptic membrane that diffuses across the synaptic cleft and alters the activity of the postsynaptic cell -neurotransmitters can stimulate (or inhibit) the production of an action potential in the postsynaptic membrane (the sarcolemma) by binding to ligand-gated ion channels (ligand-gated ion channels open when a ligand (a chemical signal) binds to a receptor that is part of the ion channel)
What is ACh estrase and what does it do, an enzyme in the synaptic cleft?
Acetylcholinesterase -rapidly breaks down acetylcholine to acetic acid and choline
What do I bands contain?
Actin myofilaments only -included the Z line- in the middle of the band -extends from either side of the Z lines to the ends of the myosin myofilaments
What does insufficient oxygen consumption relative to an oxygen deficit cause (as during exercise conditions)?
Aerobic respiration is elevated after anaerobic respiration until the imbalances of homeostasis that occurred during exercise become rectified
What are neuromodulators? Give examples.
All substances released from neurons that influence the likelihood of occurrence of an action potential (close to the threshold while neurotransmitter brings you to threshold) -nicotine, caffeine
What is step 1 of the process of neuromuscular junction action potentials? *****
An action potential (orange arrow) arrives at the presynaptic terminal and causes voltage-gated Ca2+ channels in the presynaptic membrane to open
What is step 1 of the process of Excitation- Contraction Coupling?
An action potential that was produced at the neuromuscular junction is propagated along the sarcolemma of the skeletal muscle. The depolarization also spreads along the membrane of the T tubules -starts when action potential is propagated across the sarcolemma of the skeletal muscle
How is ATP produced by Anaerobic Respiration?
Anaerobic respiration produces ATP less efficiently but more rapidly than aerobic respiration -Lactic acid levels increase because of anaerobic respiration
What is the function of ependymal cells? What do they secrete? (CNS)
Associate with certain blood vessels to form choroid plexuses -choroid plexuses secrete cerebrospinal fluid (what the brain is sitting inside) -choroid plexus is a network of blood vessels in ventricles of the brain (ependymal cells line ventricles of brain and spinal cord)
What type of contractions of motor units produce smooth, steady muscle contractions?
Asynchronous contractions
At what point is maximum tension produced?
At the optimal length -At the normal resting length of a muscle, the sarcomeres are also at an optimal length. The muscle produces maximum tension in response to a maximal stimulus at this length
Where do axons arise from the neuron's cell body/ soma?
Axon hillock -the most sensitive region of the neuron -where the most (V) gated Na+ channels occur
Motor neurons extend together with arteries and veins through the connective tissue of skeletal muscles. At the level of the perimysium, what part of the motor neurons branch?
Axons
What part of motor neurons carry action potentials to skeletal muscle fibers?
Axons -Axons of motor neurons carry action potentials at a high velocity from the brain and spinal cord to skeletal muscle fibers. The axons branch repeatedly, and each branch projects towards one muscle fiber to innervate (supply with nerves) it. Thus, each muscle fiber receives a branch of an axon, and each axon innervates more than one muscle fiber.
What is the cytoplasm and plasma membrane of the axon called?
Axoplasm Axolemma
Why does the force of contraction of a whole muscle increase with increased frequency of stimulation?
Because of an increasing concentration of Ca2+ around the myofibrils and because of complete stretching of muscle elastic elements
What is the function of microglia? When does this happen?
Become mobile and phagocytic in response to inflammation -Phagocytize necrotic tissue, micro-organisms, and foreign substances that invade the CNS (protect cell against bacteria and viruses- has lots of lysosomes)
What does the CNS consist of? (two things)
Brain and spinal cord -continuous with each other in the body
How are Schwann Cells structured? (PNS)
Broad cell that wraps many times around a portion of an axon -forms a myelin sheath around an axon in the PNS like an oligodendrocyte does so in the CNS -unlike oligodendrocytes, schwann cells only wrap around a portion of only one axon for myelinated but can surround a series of axons in unmyelinated
What is step 3 of the process of Excitation- Contraction Coupling?
Ca2+ ions released from the sarcoplasmic reticulum bind to troponin molecules. The troponin molecules bound to G actin molecules are released, causing tropomyosin to move, and to expose the active sites on G actin -ATP is required for transportation of Ca2+ -Ca2+ binds to TnC (binding sites on the troponin molecules of the actin myofilaments) -the tropomyosin-troponin complex changes shape, exposing active sites on F actin molecules on actin myofilaments
What is step 2 of the process of neuromuscular junction action potentials?
Calcium ions enter the presynaptic terminal and initiate the release of the neurotransmitter ACh from inside the synaptic vesicles
What is excitability, one of the major functional properties of muscle tissue?
Capacity of a muscle to respond to stimulus from our nerves (action potential) (responds to stimuli)
What do multipolar neurons do? What is an example of a multipolar neuron?
Carry motor info -Motor neurons and neurons within the CNS
What is step 8 of the process of neuromuscular junction action potentials?
Choline is symported (movement of more than one molecule across a membrane) with Na+ into the presynaptic terminal, where it can be recycled to make ACh. Acetic acid diffuses away from the synaptic cleft
What are the side branches of an axon (if have any) called?
Collateral axons
In what way is the muscular system functional for contraction of the heart?
Contraction of cardiac muscle causes the heart to beat, propelling blood to all parts of the body
What is step 2 of the process of cross-bridge movement during muscle contraction?
Cross-bridge formation -the myosin heads bind to the exposed active sites on the actin myofilaments to form cross-bridges, and phosphates are released from the myosin heads
What is step 4 of the process of cross-bridge movement during muscle contraction?
Cross-bridge release -an ATP molecule binds to each of the myosin heads, causing them to detach from the actin
What does the the reestablishment of the troponin-tropomyosin complex cause?
Cross-bridges cannot reform once they have been released so the muscle relaxes -inhibition of cross-bridge formation -muscle fiber lengthens passively***
What does the M-Line help with?
Holding the myosin myofilaments in place, similar to the way the Z line holds actin myofilaments in place
Each muscle fibers is surrounded by _________.
Endomysium
Extra notes
Energy is needed not only to make muscle fibers contract but also to make muscle fibers relax***
The entire muscle is surrounded by what, which in turn is surrounded by fascia? *****
Epimysium
What does it mean if a skeletal muscle attachment is indirect? (more common)
Epimysium extends beyond bone as a: 1. Tendon- rope-like -connects skeletal muscle to periosteum of bone 2. Aponeurosis- flat/ layers of tendons that form a sheet connective tissue wrappings extends beyond the muscle as a rope-like tendon or sheet-like aponeurosis (fibrous membrane binding muscle to bone)
What does it mean if a skeletal muscle attachment is direct?
Epimysium fused to periosteum of bone -epimysium surrounds the entire muscle
Extra notes
Epimysium- surrounds entire muscle Perimysium- surrounds muscle fascicles Endomysium- surrounds each muscle fibers
Action potentials produced in the sarcolemma of a skeletal muscle fiber can lead to contraction of the fiber. What is the mechanism called by which an action potential causes contraction of a muscle fiber?
Excitation-Contraction Coupling -involves the sarcolemma, T tubules, sarcoplasmic reticulum, Ca2+, and troponin -begins at the neuromuscular junction with the production of an action potential in the sarcolemma
The combination of neurotransmitters with their specific receptors causes either depolarization or hyperpolarization of the postsynaptic membrane. What kind of potential causes depolarization?
Excitatory Postsynaptic Potential (EPSP) -causes a stimulatory response due to increased membrane permeability to Na+ (goes into cell) -can create action potential because depolarization may meet threshold and cause a response to the cell
What is step 1 of the process of cross-bridge movement during muscle contraction?
Exposure of active sites -before cross-bridges cycle, Ca2+ binds to the troponins and the tropomyosins move, exposing active sites on actin myofilaments
What is the function of an oligodendrocyte?
Extensions form insulating material -insulating material is called a myelin sheath -responsible for myelin production in the CNS (increase speed of impulse conduction) -a single oligodendrocyte may be associated with several axons (covers them)---a single oligodendrocyte can form myelin sheaths around portions of several axons within the CNS -responsible for brain tumors
What is the function of Schwann Cells?
Forms the myelin sheath for the portion of the axon it wraps (insulation)
What are the monomers called that compose F actin on the actin myofilament?
G actin monomers (globular actin) -each G actin monomer has an active site where myosin molecules can bind during muscle contraction -each F actin strand is a polymer for G actin monomers
What do myelinated axons have that unmyelinated axons do not?
Gaps in myelin called Nodes of Ranvier -myelin sheath is not continuous -although the axon at the node of ranvier is not covered with myelin, Schwann cells or Oligodendrocytes extend across the node and connect to eachother
What are dendrites a part of in nervous tissue?
Gray matter -gray matter is lots of cell bodies (somas) and dendrites
What is the cell body (soma) a part of in nervous tissue?
Gray matter -gray matter is lots of cell bodies (somas) and dendrites
What are axons a part of in nervous tissue?
Gray matter (unmyelinated) or white matter (myelinated)
How are oligodendrocytes structured? (CNS)
Have broad cytoplasmic extensions that wrap many times around axons Oligo=huge dendro= branched cyte= cell
How are ependymal cells structured? Where are they located?
Have cilia at their top surfaces and long processes at basal surfaces -line the ventricles of the brain and central canal of the spinal cord
What is step 5 of the process of cross-bridge movement during muscle contraction?
Hydrolysis of ATP -the myosin ATPase portion of the myosin heads split ATP into ADP and phosphate (P), which remain attached to the myosin heads
Extra notes on fully contracted sarcomere
In a contracted muscle, the A bands, which are equal to the length of the myosin myofilaments, do not narrow because the length of the myosin myofilaments does not change, nor does the length of the actin myofilaments. In addition, the ends of the actin myofilaments are pulled and overlap in the center of the sarcomere, shortening it and the H zone disappears.
Extra notes on relaxed sarcomere
In a relaxed muscle, the actin and myosin myofilaments overlap slightly, and the H zone is visible. The sarcomere length is at its normal resting length. As a muscle contraction is initiated, actin myofilaments slide past the myosin myofilaments, the Z disks are brought closer together, and the sarcomere begins to shorten. -sarcomeres lengthen during relaxation
Action potentials carried by motor neurons stimulate action potentials in muscle fibers because of events that occur where?
In the neuromuscular junction (also known as synapse)
What kind of potential causes hyperpolarization?
Inhibitory Postsynaptic Potential (IPSP) -causes an inhibitory response -caused by increased membrane permeability to K+ ions (goes out of cell) or Cl- ions (goes into the cell)
How is nervous tissue organized?
Into bundles of: 1. White matter, consisting of myelinated axons 2. Gray matter, consisting of neuron cell bodies and their dendrites
What is step 5 of the process of neuromuscular junction action potentials?
Ligand-gated Na+ channels open and Na+ enters the postsynaptic cell, causing the postsynaptic membrane to depolarize (get less negative). If depolarization passes threshold, an action potential is generated along the postsynaptic membrane.
What is the H-Zone or band, where is it located? *****
Located in the center of the A-band where only myosin myofilaments are present
What is the M-Line, where is it located?
Located in the center of the H-zone -Links the myosin myofilaments
Describe the layers in the wrappings of a myelinated axon; what color are they?
Many layers of tightly wrapped membranes rich in phospholipids -white in color due to high lipid concentration
What is the muscle plasma membrane in the area of the neuromuscular junction called? What does it contain?
Motor End Plate or Postsynaptic Membrane -contains receptors for ACh -is the sarcolemma (muscle cell membrane) around a neuromuscular junction
As the frequency of contractions increases, the increased tension produced is called what?
Multiple-wave summation
What occurs when ACh is no longer released at the neuromuscular junction?
Muscle Relaxation
What is extensibility, one of the major functional properties of muscle tissue?
Muscle can be stretched to its normal resting length and beyond to a limited degree (can be stretched and still contract)
What happens to the contraction if a muscle's initial length is shorter or longer than optimum?
Muscle contracts with less than maximum force -as the length of a muscle increases, its active tension also increases, to a point. -if muscle length stretches farther than its optimum length, the tension it produces begins to decline
A muscle is divided into compartments or bundles of muscle fibers called what?
Muscle fascicles -skeletal muscles are complete organs consisting of cells called skeletal muscle fibers
What controls the contraction of skeletal muscles?
Muscle fibers are electrically excitable. Axons of neurons extend from the brain and spinal cord to skeletal muscle fibers. The nervous system controls the contraction of skeletal muscles through these axons. Electrical signals, called action potentials, travel from the brain or spinal cord along the axons to the muscle fibers and cause them to contract.
Why is there no relaxation between contractions during complete tetanus?
Muscle fibers produce action potentials so rapidly that no relaxation occurs between them
Relating to contractility and extensibility, muscle tissue shortens and stretches/lengthens in what ways?
Muscle tissue shortens forcefully and lengthens passively
What is the constant tension produced by muscles for long periods of time called?
Muscle tone -causes back straight and head upright
What is the contraction of a single muscle fiber or a whole muscle in response to a stimulus?
Muscle twitch -a single, brief contraction and relaxation cycle in a muscle fiber -does not perform any work
What are the effects of exercise on muscles?
Muscles increase (hypertrophy) or decrease (atrophy) in size because of a change in the size of muscle fibers -so can perform more efficiently -not easy to change
Which axons conduct action potentials faster?
Myelinated
What cells fuse to form one skeletal muscle cell (muscle fiber)?
Myoblasts -less mature that develop into muscle fibers
Once the active sites on actin myofilaments are exposed, what happens to the myosin myofilament? What is this called?
Myosin heads pivot towards the M-line, sliding the actin over the myosin (POWER STROKE) -power stroke is movement of the myosin molecule while the cross-bridge is attached
Axons of motor neurons branch, and each branch projects to a muscle fiber to form what?
Neuromuscular junction
Near the muscle fiber it innervates, each axon branch forms a cluster of enlarged axon terminals called what? Where are these clusters located on the muscle fiber?
Neuromuscular junction (also known as synapse) -rest in an invagination of the sarcolemma -neuromuscular junction consists of the axon terminal and the area of the muscle fiber sarcolemma they innervate
What happens to the shape of actin and myosin myofilaments during contraction?
Nothing -Actin and myosin myofilaments do not change in shape during contraction
What happens to the number of skeletal muscle fibers with age?
Number of skeletal muscle fibers remains the same. Enlargement (hypertrophy) of muscles results from an increase in the SIZE of each muscle fiber, not from the increase in number of muscle fibers.
Where is the greatest concentration of receptor molecules?
On the post-synaptic membrane, but they may also be found on some presynaptic membranes
What is step 4, the last step, of the process of Excitation- Contraction Coupling?
Once active sites on G actin molecules are exposed, the heads of the myosin myofilaments bind to them to form cross-bridges -cross-bridges form between actin and myosin
What is a motor unit? *****
One single motor neuron and all the muscle fibers it controls or its branches innervate -on the figure, the muscle fibers shown in dark pink are part of one motor unit, and the muscle fibers shown in light pink are part of a different motor unit-- in this figure the motor neuron is innervating the dark pink muscle fibers
Where do dendrites receive input from?
Other neuron's axons and from the environment
How are astrocytes structured?
Star-shaped with many cytoplasmic extensions from the cell body, each with broad "foot processes" -foot processes cover capillaries astrocytes are star shaped= astro= star= space
Each fascicle is surrounded by _______.
Perimysium
What happens as a result of extreme muscular fatigue?
Physiological contracture -inability of muscles to contract or relax
What is step 3 of the process of cross-bridge movement during muscle contraction?
Power Stroke -energy stored in the myosin heads is used to move the myosin heads, causing the actin myofilaments to slide past the myosin myofilaments, and ADP molecules are released from the myosin heads
What are the variations in terms of the number of muscle fibers in a motor unit?
Precise movements use small motor units. Gross movements use large motor units
What is the outer tip of the nerve terminal called? What does it contain?
Presynaptic Terminal -contains synaptic vesicles (small, spherical sacs) with ACh (acetylcholine, a neurotransmitter) -synapse is another name for neuromuscular junction
What are the enlarged ends of the telodendria (branches) of the axon called? What do the ends contain?
Presynaptic Terminals -Contain vesicles that contain chemical neurotransmitters -Action potentials conducted along the axon to the presynaptic terminal stimulate exocytosis (use ATP) of the neurotransmitters from their vesicles to the synapse (neuromuscular junction). Then neurotransmitters cross the synaptic cleft to stimulate or inhibit the postsynaptic cell
What is the purpose of myelin?
Protects and electrically insulates axons from one another
What is step 6, the last step, of the process of cross-bridge movement during muscle contraction?
Recovery Stroke -the heads of the myosin molecules return to their resting position and energy is stored in the heads of the myosin molecules. If Ca2+ is still attached to troponin, cross-bridge formation and movement are repeated. This cycle occurs many times during a muscle contraction. Not all cross-bridges form and release simultaneously
Myofilaments are organized in repeating functional units. What are these units called; what actin and myosin together form?
Sarcomeres -joined end to end to form the myofibrils -basic structural and functional unit of skeletal muscle because it is the smallest portion of skeletal muscle capable of contracting
What is the highly organized smooth endoplasmic reticulum of muscle fibers called? What does it regulate?
Sarcoplasmic Reticulum -regulates intracellular Ca+ levels
What do pseudo-unipolar neurons do? What is an example of a pseudo-polar neuron?
Sensory -most sensory neurons are pseudo-unipolar
Extra notes on divisions of PNS
Sensory division of the PNS detects stimuli and conducts action potentials towards the CNS. The CNS interprets the incoming action potentials and initiates action potentials that are conducted through the motor division to produce a response. The motor division is divided into somatic nervous system (voluntary- to muscles) and autonomic nervous system (involuntary- to glands). receptor- sensory NS- CNS- motor NS- effector
What do bipolar neurons do? What is an example of a bipolar neuron?
Sensory for sight -In retina of eyes
What are dendrites of the neuron?
Short, highly branched cytoplasmic extensions
How many actin myofilaments and myosin myofilaments form a sarcomere?
Six actin myofilaments (thin) surround one myosin myofilament (thick)
Each skeletal muscle is a complete organ consisting of cells, called what? How are cells structured?
Skeletal muscle fibers multi-nucleated and appear striated
In what way is the muscular system functional for movement?
Skeletal muscles are attached to bones and are responsible for the majority of body movements (walking, running, chewing, manipulating objects with the hands)
In what way is the muscular system functional for posture?
Skeletal muscles are constantly maintaining tone, which keeps us sitting or standing erect.
In what way is the muscular system functional for support/ respiration?
Skeletal muscles of the thorax carry out the movements necessary for respiration (breathing in)
What do the actin and myosin myofilaments do that causes sarcomeres to shorten, or contract?
Slide past one another -In a sarcomere, the actin and myosin myofilaments slide past one another but remain the same length as when the muscle is at rest
The primary function of skeletal muscle cells is to generate force by contracting, or shortening. A parallel arrangement of myofilaments in a sarcomere allows them to interact, which causes muscle contraction. What is this interaction called?
Sliding Filament Model -theory of all or nothing- all contract or rest- not in the middle
How are microglia structured? (CNS)
Small glial cells with many extensions
How are Satellite Cells structured (what do they surround)? (PNS)
Surround/associate neuron cell bodies in the PNS -in sensory and autonomic (involuntary) ganglia (structure of neuron cell bodies)
What is the space called between the Presynaptic Terminal and the Motor End Plate/ Postsynaptic Membrane ? What does it contain?
Synaptic Cleft -contains ACh estrase (degrades ACh into acetic acid and choline-- choline is reabsorbed into the presynaptic terminal to re-form acetylcholine)
In between two adjacent terminal cisternae the sarcolemma invaginates to form what?
T- Tubules
Along the surface of the sarcolemma, what are the many tube-like invaginations of the sarcolemma?
T- Tubules (Transverse Tubules) -between two adjacent terminal cisternae
What are the lateral channels of sarcoplasmic reticulum known as?
Terminal Cisternae
What is the period of sustained contraction called, that follows multiple-wave summation?
Tetanus
In what way is the muscular system functional for constriction of organs and vessels?
The contraction of smooth muscles within the walls of internal organs and vessels causes them to constrict- Constriction can help propel food and water in the digestive tract, remove materials from organs (urinary bladder or sweat glands), and regulate blood flow through vessels
What is step 2 of the process of Excitation- Contraction Coupling?
The depolarization of the T tubule causes (V) gated Ca2+ channels in the sarcoplasmic reticulum to open, resulting in an increase in the permeability of the sarcoplasmic reticulum to Ca2+, especially in the terminal cisternae. Calcium ions then diffuse from the sarcoplasmic reticulum into the sarcoplasm -when the action potential reaches T tubule it triggers the release of stored intracellular Ca2+ from the terminal cisternae of the sarcoplasmic reticulum by opening (V) gated Ca2+ channels
What is step 7 of the process of neuromuscular junction action potentials?
The enzyme ACh estrase, which is attached to the postsynaptic membrane, removes ACh from the synaptic cleft by breaking it down into acetic acid and choline
As the Ca2+ concentration decreases in the sarcoplasm, the Ca2+ diffuses away from the troponin molecules. What does this cause?
The troponin-tropomyosin complex re-establishes its position, inhibiting further cross-bridge formation -blockage of the active sites on actin molecules
In what way is the muscular system functional for maintaining body temperature?
When skeletal muscles contract, heat is given off as a by-product. This heat is critical for maintaining body temperature.
What do dendrites do?
When stimulated, they conduct small electric currents, which are conducted to the neuron's cell body (soma)
What is an increase in the force of contraction during the first few contractions of a rested muscle called?
Treppe -like a staircase process -when a muscle fiber is stimulated at rapid succession -contracts with greater force with each subsequent stimulus -occurs in a muscle fiber that has rested for a prolonged period
What do one T-Tubule and two terminal cisternae form?
Triad
Where are action potentials generated in the neuron?
Trigger Zone -trigger zone consists of the axon hillock and the part of the axon nearest the cell body (called the initial segment- the beginning of the axon)
Where are unmyelinated axons located on the neuroglial cells?
Unmyelinated axons rest in invaginations (pouches) of associated Schwann Cells or Oligodendrocytes, but are NOT wrapped by them***** -cell's plasma membrane surrounds each axon but does not wrap around it many times -no gaps (no node of ranvier) -are unmyelinated because do not wrap/ provide myelin sheath
How does the Sliding Filament Model relate to the overall muscle contraction?
When the myofilaments shorten, the myofibrils also shorten because the myofibrils consist of sarcomeres joined end to end. The myofibrils extend the length of the muscle fibers, and when they shorten the muscle fibers shorten. Groups of muscle fibers make up a muscle fascicle, and several muscle fascicles make up a whole muscle. Therefore, when sarcomeres shorten, myofibrils, muscle fibers, muscle fascicles, and muscles shorten to produce muscle contraction.
When does temporal summation occur?
When two or more graded potentials are produced at a given location on the neuron's cell body or dendrites in such rapid succession that they can summate at the trigger zone -temporal- time- how fast -summation means adding things up (adding quickness) -temporal and spacial summation can occur at the same time -a single postsynaptic potential is not usually strong enough to reach threshold -many graded potentials are produced in the postsynaptic membrane at a given time -graded potentials combine at the trigger zone of the postsynaptic neuron (where the hillock and end of axon meet) -the trigger zone has a concentration of Na+ channels that is 7x greater than elsewhere in the cell body -if the combination of graded potentials reaches or exceeds threshold at the trigger zone, an action potential is produced
When does spacial summation occur?
When two or more graded potentials from different locations on the neuron's cell body or dendrites reach the trigger zone simultaneously -spacial= within space (location) -summation means adding things up (adding locations) -a single postsynaptic potential is not usually strong enough to reach threshold -many graded potentials are produced in the postsynaptic membrane at a given time -graded potentials combine at the trigger zone of the postsynaptic neuron (where the hillock and end of axon meet) -the trigger zone has a concentration of Na+ channels that is 7x greater than elsewhere in the cell body -if the combination of graded potentials reaches or exceeds threshold at the trigger zone, an action potential is produced
What is the protein that attaches actin myofilaments of adjacent sarcomeres?
Z Line -each sarcomere extends from one Z disk to an adjacent Z disk -Z line is a network of protein forming disk like structures for the attachment of actin myofilaments
What is tropomyosin, a component of the actin myofilament?
an elongated protein that winds along the groove of the F actin double helix
What is muscle fatigue?
decreased ability to do work
What is the outermost layer of dense irregular connective tissue surrounding a peripheral nerve? It usually surrounds multiple nerve fascicles as well as blood vessels which supply the nerve.
epineurium
Where is the A band located on the sarcomere?
extends the length of the myosin myofilament within a sarcomere
How do fast-twitch fibers split ATP?
rapidly -sprinter -anaerobic exercise develops type IIb -aerobic exercise turns type IIb into type IIa
What color are fast-twitch fibers?
red
What color are slow-twitch muscle fibers?
red
What is Saltatory Conduction?
the mechanism for conducting action potentials on a myelinated axon -an action potential is conducted from one node of ranvier to another -saltare means to leap (saltatory conduction) -an action potential at one node of ranvier generates local currents that flow toward the next node of ranvier
What do cholinergic synapses respond to? Are they stimulatory or inhibitory?
the neurotransmitter acetylcholine (ACh) -always stimulatory
What do adrenergic synapses respond to? Are they stimulatory or inhibitory?
the neurotransmitter norepinephrine -can be either stimulatory or inhibitory
What do slow-twitch fibers consist of?
well-developed blood supply, lots of mitochondria, and lots of myoglobin
