Midterm Flashcards

Question

Mechanically Gated Membrane Channels

Answer 1

- Ion channel that opens in response to mechanical movement -> need to make contact to open -> mechanoreceptors detect this Ex: mechanical stretch modifies mechanosensitive channels

Answer 2

- is employed to generate a gradient or to maintain it - The transport direction is “uphill”, or against the chemical, or electrical gradient -> low to high conc. - Energy is required. - The transporters, called “pumps” use ATP directly as a source of energy for the transport -> They are integral membrane proteins which bind to one or more ions at one side of the membrane and release them at the opposite side - it is saturable Ex: Na+, K+, ATPase Pump

Answer 3

- transports (extrudes) 3 Na+ from the cytoplasm/ICF to the extracellular fluid (ECF) against its electrochemical gradient (BOTH electrical and concentration gradient) - Simultaneously, takes 2 K+ into the cell against its concentration gradient only - This generates a high Na+ concentration at the extracellular side and a high K+ concentration at the intracellular side - > electrogenic pump - The exchanges ratio is 3 Na+ for 2 K+ - This ratio creates differences in their concentration inside(ICF) and outside (ECF) - some K+ leaks back out of the cell driven by its chemical gradient

Answer 4

- secondary active transport mechanism - Both the carrier and substrate are transported in the same direction - Energy is used to generate a concentration gradient of a carrier - > this gradient is the driving force for the transport of two molecules

Answer 5

- secondary active transport mechanism - carrier and substrate are transported in opposite directions - Energy is used to generate a concentration gradient of a carrier - > this gradient is the driving force for the transport of two molecules

Answer 6

- kidney and the digestive tract | - the heart

Answer 7

- Volume flow of water carries dissolved substances - Bulk flow of fluid and electrolytes occurs through "pores" and intercellular clefts - This mechanism of exchange is particularly important in renal glomerular capillaries however, it occurs to variable extent in nearly all tissues

Answer 8

- paracellular water flow "drags" dissolved substances: sodium and water - osmosis explains this type of transport

Answer 9

- Cells take in large particles by surrounding the particle with projections of its membrane (pseudopods) - The completely covered particle is then incorporated as a vesicle and broken down (digested) by lysosomes

Answer 10

- tiny droplets of extracellular fluid are surrounded by pseudopods and incorporated as vesicles

Answer 11

- Incorporated vesicles (by phagocytosis or pinocytosis) fuse with the cell membrane and release their content to the extracellular fluid

Answer 12

- The total number of positive and negative charges in the extracellular and the intracellular fluid is equal - There is only an accumulation of positive charges at the outside (ECF) and of negative charges at the inside (ICF) in the immediate vicinity of the cell membrane

Answer 13

- The ion concentration gradient favors the efflux of potassium and the influx of sodium - The presence of potassium leak channels in a very high proportion of excitable cells contribute to the creation of the resting membrane potential - > K+ goes from the ICF to the ECF - K+ diffuses through leak channels more easily than Na+ does - The Na+ and K+ pump invests energy to put the K+ back inside the cell - Every time K+ leaks it creates a difference in charge because we have less positive charges in the ICF (more negative) and more positive charges in the ECF - > Causes the ICF (cytosol) to lose more positive charges than it gains, thus leading to the negative resting membrane potential

Answer 14

1. Sodium Potassium Pump 2. The Potassium leak channels 3. The non diffusible ions as described by the Gibbs-Donnan Effect

Answer 15

- The presence of non diffusible ions (charged negative proteins) at the internal side of the cellular membrane influences the distribution of other ions - > Negative ions (anions), such as phosphate and Cl-, and some proteins from the intracellular fluid are attracted and move close to the membrane - > Most transmembrane proteins are embedded in the lipid bilayer in the intracellular domain and have a negative charge - Because the positive Na+ and the positive K+ ions repel each other, K+ is driven away from the membrane

Answer 16

- the most important ion in the ECF - Chloride is attracted by the positive charges of the extracellular gradient which promotes Cl- to diffuse to the ECF - BUT there is a concentration gradient for Cl- that promotes the influx into the cell - The chloride channels of the majority of cell types have NO gates! - Therefore, the diffusion is driven by the electro-chemical gradient - When the electrical and chemical gradients are equal, the net diffusion stops - Because chloride carries a negative charge, any movement of chloride into or out of the cell influences the membrane potential, but these movements are rather a consequence of the membrane potential than an active contribution to its generation in axons!!! - This might be different in the smooth muscle of the gut.

Answer 17

- Calculation of the electrical potential generated by a SINGLE kind of ion - Diffusion of ions based on chemical gradient will continue until the counteracting electrical gradient equals the chemical gradient - The electrical potential of this balanced state for one univalent ion can be determined from the following formula - Resting membrane potential is usually around -90, or -70

Answer 18

- The resulting membrane potential after equilibrium for K+ is -93 mV - > Very close to the resting membrane potential (-70/-90), therefore K+ is the main ion contributing to the resting membrane potential - The resulting membrane potential after equilibrium for Na+ is +61 mV - > Sodium is very far away from the resting membrane potential, therefore it contributes very little to it

Answer 19

- allows you to calculate the electrical potential generated by ALL diffusible ion

Answer 20

- The influx of sodium depolarizes the membrane from -70 toward 0 - DECREASE in membrane potential relative to resting (-70), becomes more positive - The Na+ gates become inactive when the membrane potential becomes positive - The K+ channels open too slowly and causes an "overshoot" - > goes above the positive value - Driving force is the electrochemical gradient

Answer 21

- K+ channels open when the potential membrane becomes positive, but open slowly - Efflux of K+ into ECF makes the membrane more negative, or less positive - The driving force is the chemical gradient. - The K+ channel gate closes too slowly after this and causes hyperpolarization - > when the membrane potential is more negative than the resting membrane potential

Answer 22

- INCREASE in membrane potential relative to resting (-70), becomes more negative - Caused by either the efflux of K+ towards ECF, or the influx of Cl- into ICF Ex: GABA causes an influx of Cl- and therefore hyperpolarization

Answer 23

- all or none principle - > any depolarization of the membrane of an excitable cell either has no effect, or results in a full action potential - Cell is at Resting membrane potential (-70, or -90) and then we apply a stimulus, if the threshold potential is reached depolarization occurs - Depolarization signals over LONG distances - If depolarization does not reach the threshold it is a graded potential - > stimuli, not reaching the threshold potential has no effect aka NONE - At resting state all gated ion channels are closed - Depolarization occurs when Na+ channels open (influx) and K+ channels close - > Once the threshold potential is reached, the sequence of depolarization and repolarization starts and continues automatically - Repolarization occurs when Na+ channels are inactivated and K+ channels open - K+ channels are slower to open than sodium channels - Hyperpolarization is when Na+ channels close, but the K+ channels remain open - Action potentials occur down the entire length of the axon as the action potential propagates down the axon like a wave

Answer 24

- This type of membrane potential starts above the threshold, however if the stimulus is not strong enough to reach the trigger zone (axon hillock) above the threshold then no action potential is generated - An action potential (AP) is initiated when the membrane gets depolarized to the threshold - > If the depolarization does not reach the threshold then it is a graded potential - If we increase the stimulus intensity we can release more neurotransmitters and reach the threshold to conduct an action potential in the axon - > Depolarization signals over SHORT distances

Answer 25

- Activation gate is regulated by the concentration of calcium in the ECF - The activation gate is bound to some Ca ions, so if we lose some Ca ions the activation gate will open in an easier manner - If we apply an electrical stimulus the voltage gate will open, influx of sodium occurs and it promotes depolarization of the cell as long as it reaches the threshold

Answer 26

- When a positive value of the membrane potential is reached the inactivation gate is activated, so the channel closes and the transport of sodium stops - potential is reversed to positive for a short time (overshoot) - The efflux of K+ repolarizes de membrane toward -70 mV - Driving force is the chemical gradient - The electrical gradient opposes the diffusion - The K+ channel gate closes too late, and the repolarization goes beyond -70 mV - > hyperpolarization

Answer 27

- is the period of an on-going action potential during which no stimulus, not even an extremely strong one, can initiate another action potential - the time when the sodium channels are open until they reset - > The onset of this point is when the voltage reaches the threshold and ends at a point during the depolarization phase

Answer 28

- is the period of time following the absolute refractory period during which a strong suprathreshold stimulus can initiate another action potential - signal strength required to initiate a superseeded AP is highest in the beginning of the relative refractory period and decreases to a normal strength towards the end of the relative refractory period - When most of the sodium channels have reset, but some Potassium channels are still open - > Onset of this period is at the end of the absolute refractory period and ends at the point where the membrane potential returns to the resting potential

Answer 29

- eclampsia/puerperal hypocalcemia in small animals - Decreased capacity to mobilize calcium from the bones - Increases sodium voltage channels conductivity and the resting membrane potential will be closer to the threshold - Cells do not respond well to a stimuli - Panting and restlessness are early signs. Mild tremors, twitching, muscle spasms and gait changes result from increased neuromuscular excitability

Answer 30

- hyperkalemic periodic paralysis in horses/uroabdomen secondary to obstructive urolithiasis and bladder rupture - Is an inherited disease of the skeletal muscle which is caused by a genetic defect that limits the inactivation of the sodium voltage channels - Transit hyperkalemia might depolarize the cell membrane and take the resting membrane potential closer to the threshold - Then if the sodium voltage channels are activated, the inactivation gate will fail due to the mutation - Characterized by sporadic attacks of muscle tremors, shaking or trembling, weakness, and/or collapse

Answer 31

- imbalance between the intake/excretion ratio - Lose more potassium in the gastrointestinal tract or renal system - Decreases the resting membrane potential, goes more negative which means hyperpolarization will occur and the distance from the new resting membrane potential is very far - So those excitable cells will be very hard to excite - Cat with ventroflexion of the neck (can not raise their head) - Skeletal muscle will be too relaxed and results in muscle weakness

Answer 32

- or nerve cells - have the property of electrical excitability to generate, propagate, and respond to action potentials - have dendrites for incoming messages and axons for outgoing messages

Answer 33

- propagate APs afferently - for incoming messages - toward the center, or signal input

Answer 34

- propagate APs efferently - for outgoing messages - away from the center, or signal output

Answer 35

- surround the axon in most mammalian neurons - myelinated axons display a faster conduction of the electrical impulse - produce myelin in the periphery (PNS) - between two Schwann cells there is a gap called the Node of Ranvier - > crucial for saltatory conduction of AP

Answer 36

- is around the axon hillock and conducts electrical activity - Amount of sodium voltage channels in the axon hillock is higher than in the rest of the neuron - where APs are created

Answer 37

- afferent neurons - carry information from the PNS towards the CNS (brain and spinal cord) - There are specialized sensory neurons that respond to external stimuli and generate and propagate APs - The soma of the neuron is located in the sensory ganglion

Answer 38

- they connect two or more neurons and transmit information from the first to the second - These are the vast majority of neurons

Answer 39

- Efferent Neurons - carry information out of the CNS (brain or spinal cord) and to the effector cells/target cells, or effectors - > effectors are muscle cells and gland cells

Answer 40

- are the source of information - They transform a mechanical, physical, or chemical stimulus into a corresponding rate of action potentials - All receptors are selective, that is they respond mainly to one particular stimulus, adequate stimulus - > But do not response at all or only weakly to other kinds of stimuli - The action potentials generated are conducted afferently towards to the central nervous system - If the intensity of the stimuli is very high you are going to have a lot of action potential, if it is weaker you will have fewer action potential

Answer 41

- first order sensory neuron with free nerve endings - free nerve endings are bare dendrites and can detect a signal - Many layers of cell membranes, or structures (like an onion) increase the sensitivity for pressure in the free dendrites - > pressure changes increase or decrease ionic conductivity of these layers

Answer 42

- sensory receptor synapses with first order sensory neuron - The taste receptor consists of two cells, a specialized chemo-sensory cell and a first-order sensory neuron - The chemo-sensory cell is stimulated by a particular substance such as glucose, and responds with a change of its membrane potential which in turn causes the release of a neurotransmitter into the synaptic cleft - > neurotransmitter activates the sensory neuron

Answer 43

- produces myelin sheaths in the CNS

Answer 44

- are surrounded by a thin coat of neuroglial cell membrane which provides some electrical insulation - There is no segmentation - > do not have Schwann cells and no node of ranvier in the axon

Answer 45

- are covered by many layers of neuroglial cell membrane - > creates an extraordinary level of insulation that will promote a very fast conduction - They are segmented due to the nodes of Ranvier embedded

Answer 46

- the conduction is slow and requires more energy because the electric current spreads over a wider area of the ECF

Answer 47

- localizes the electric current to the space between the axon and the insulation, thus saving energy but the conduction is still slow

Answer 48

- forces the electric current to flow around the insulation, thus avoiding at the length of the insulation a slow continuous depolarization and energy consumption - > no spreading to the ECF - The conduction is faster and more efficient

Answer 49

- The refractory period does not allow it to go backwards - The repolarizing membrane is very difficult to get the AP backwards - AP can not propagate in reverse because the preseeding channels are still in an absolute refractory period

Answer 50

- characteristic for unmyelinated axons - requires the depolarization of the entire axon - The AP causes a depolarization of the near axonal membrane in front - In close distance this effect is strong enough to achieve the threshold potential, thus initiating a full depolarization in this area. - As a result the AP travels along the axon, but the currents tend to decay along the axon - > this is because there is no insulation - APs travel along an axon as a sequence of depolarization and repolarization - > based on the automatic sequence of depolarization and repolarization an AP, once initiated, travels down the whole length of a nerve cell - tends to be slower than saltatory conduction because the entire axon must be depolarized and repolarized which depends on the ionic flow of Na+ and K+ across the cell membrane

Answer 51

- Characteristic of myelinated axons - The AP at one node of Ranvier depolarizes the neighboring node to the threshold, thus causing an AP there. - By this phenomenon, the current jumps over the Schwann cells from node to node - Action potentials “jump” from node to node, resulting in a high velocity of conduction - Schwann cells insulate the axon from the ECF by synthesizing myelin sheaths - between two Schwann cells is a gap with no insulation called the Node of Ranvier - Nodes of Ranvier “connects” the axon to the ECF and have higher proportions of sodium voltage channels in these sections than in the insulated section - Faster and metabolically more efficient than continuous conduction because the cell membrane underneath the Schwann cells remains unaffected in the resting membrane state - > Only the Nodes of Ranvier get depolarized and repolarized - Stays near the resting membrane state because of the insulation being very tight and the interaction with the ECF is very limited - Reduce the length we need to depolarize which makes it faster and metabolically efficient

Answer 52

- The left node of Ranvier is depolarized by an action potential - The right node is still in the resting state - Since the exposed areas of the axon membrane (right and left) have a different polarity, an electric current of electrons flows around the Schwann cell - This current depolarizes the right node to the threshold potential and an AP is triggered. - The membrane underneath the Schwann Cells remains almost untouched, at potential, due to the tight insulation of the axon - In fact, no extracellular space exists between the axon and the extracellular fluid

Answer 53

1. Presence of Myelin - Saltatory Conduction is Faster than Continuous Conduction - The electric current in the axon determines how fast the threshold in the next Node of Ranvier is achieved and thus the AP is initiated 2. Diameter of the Axon - the greater the diameter the higher the rate of conduction - The electric current depends on the electrical resistance of the axon, which in turn depends on the diameter of the axon - The greater the axon diameter is, then the lower the electric current resistance will be - The higher the current is, then the faster the depolarization and conduction will be

Answer 54

1. Fastest Nerve Fibers - The afferent neurons conducting from the muscle spindles, the tendons, and the organs are going to conduct very fast because they conduct protoception - The Efferent nerve fibers that are the motor components which regulates the skeletal muscle contractions also have the same type of fibers 2. Slowest Nerve Fibers - Sympathetic in the ANS - > The post ganglionic, or the slow fibers of pain conduct the electrical impulse very slowly - > very small diameter - > The resistance to the conduction of the electrical currents is higher - > Some are unmyelinated therefore they conduct impulses slower

Answer 55

- open fluid channels that conduct electricity from one cell to the next - > typical in cardiac and smooth muscles, there are a few in the CNS - There is a gap junction and the cells share the same stimulus and change in the polarity of the cell - If we apply an electrical stimulus in one cell it is called the “presynaptic” cell and then the current is conducted through the electrical synapses which is represented by the gap junctions and cell 2 can be seen as the “post-synaptic” component - > Then the electrical activity of this cell membrane is transmitted to the next - > Crucial in the heart - there is no neurotransmitter - Have connexons, which are similar to ion channels, that are triggered by depolarization of the cell membrane and allow ionic flow to the neighboring cell, thus causing depolarization again - > conduct ions, ATP, cAMP, amino acids, etc

Answer 56

- Conduct the signal only in one direction - “Translate” the electrical signal into a chemical signal and back into an electrical signal - Modulates the degree of the electrical signals in the Nervous system. - > Prevents collapse… - In the skeletal muscle and almost all synapses in mammals are chemical - use a neurotransmitter and require calcium

Answer 57

1. Arriving APs depolarize the presynaptic membrane 2. Change in polarity opens the calcium voltage gated channels 3. Ca2+ dependent exocytosis - Vesicles fuse with the membrane and release the neurotransmitter into the synaptic cleft 4. Diffusion. 5. Released neurotransmitter binds to its postsynaptic receptor 6. Postsynaptic Na+ channels open and influx to depolarize the cell 7. The neurotransmitter is removed from the synaptic cleft and the channel closes

Answer 58

1. Neurotransmitters can be returned to axon terminals for reuse, or transported into glial cells 2. Enzymes inactive neurotransmitters 3. Neurotransmitters can diffuse out of the synaptic cleft

Answer 59

- The AP will promote the exocytosis of a neurotransmitter and the neurotransmitter is going to bind to a ligand gated sodium channel and activates/open it - The influx of Na+ will occur and promotes depolarization through the post-synaptic membrane - > Will have excitatory postsynaptic potential - The neuron conduction from cell to cell has a timing - > Synaptic delay results from slow liberation and diffusion of the neurotransmitter - A single depolarization is usually insufficient to generate a postsynaptic AP - The postsynaptic potentials are graded and they may vary in amplitude, duration and shape - Two ways of accelerating the generation of APs at the postsynaptic side - > temporal summation and spatial summation

Answer 60

1. Temporal summation - a series of depolarizations from one synapse depolarize stepwise - > if the frequency of firing is increased aka you have one on top of the other can reach the threshold for an AP to occur 2. Spatial summation - more than one synapses depolarize the cell simultaneously

Answer 61

- K+ or Cl- currents hyperpolarize the membrane - If we release an inhibitory neurotransmitter and that molecule activates the receptor and promote the efflux of K+ we hyperpolarize the cell - This channel could also be a Cl- channel and we open the channel - The channel will go from the ECF to the ICF (influx) and will hyperpolarize Ex: GABA receptors do this

Answer 62

- Synapses can facilitate or inhibit the generation of postsynaptic APs - The net result is that we are not going to have a postsynaptic potential because they cancel each other - Can have depolarization from the first one and hyperpolarization in the second one - > The signal promoted by the excitatory pathway was cancelled by the inhibitory signal, so no change in cell membrane potential - > summation is cancelled

Answer 63

1. K+ - Promotes the efflux of K+ from the ICF to the ECF, so the internal side of the membrane is less positive, or more negative - The resting membrane potential goes more negative like -90 - Hyperpolarized makes it very difficult to respond to any kind of stimulus 2. Cl- - If we promote Cl- currents they are going to go from the ECF to the ICF - Influx of Cl- causes the ICF membrane to become more negative, or less positive - Cell will be hyperpolarized

Answer 64

- More than a 100 substances are either known or suspected neurotransmitter but there are only two groups - > Small molecules and neuropeptides. - Neurotransmitters can either open or block ion channels, causing changes in the membrane potential - Other neurotransmitters are also hormone produced and released to the blood stream by endocrine cells

Answer 65

1. Acetylcholine - central and peripheral nervous system. 2. Amino Acids - central nervous system (CNS) - Main excitatory transmitter is glutamate - Main inhibitory transmitter is GABA 3. Biogenic Amines - catecholamines - > dopamine, norepinephrine, and epinephrine - serotonin. 4. Gases - nitric oxide.

Answer 66

1. Enkephalins - CNS - Very potent analgesic effect 2. Endorphins and Dynorphins - In CNS - Control body temperature and reproduction - Involved in pain as well 3. Substance P - In the CNS and PNS - Transmission of peripheral pain signals

Answer 67

- Norepinephrine (NE) is synthesized from the amino acid Tyrosine - It is stored in vesicles and degraded by mitochondrial monoamine oxidase (MAO) and intracellular catechol-O-methyltransferase (COMT) - Works on alpha and beta adrenoceptors located in the postsynaptic element, but also on some alpha adrenoceptors (adrenergic receptors) in the presynaptic element

Answer 68

A. Acetylcholine 1. ACh is released into the synaptic cleft and attaches to the ACh receptors, then quickly detaches 2. Acetylcholineesterase (AChE) breaks down ACh in the synaptic cleft into choline and acetate 3. Choline is actively transported back into the presynaptic terminal for synthesis of new ACh B. Glutamate 1. Glutamate is released into the synaptic cleft and is transported back into the presynaptic terminal, or into astrocytes 2. In the presynaptic terminal, glutamate is repackaged into synaptic vesicles 3. Astrocytes convert glutamate into glutamine, which is used to synthesize glutamate in neurons

Answer 69

- Derived from acetyl coenzyme A and this molecule is synthesized from glucose in the mitochondria - If we add choline to this molecule we can synthesize acetylcholine which accumulates in the vesicles and we can release them through cholinergic neurons - ACh will work on receptors in the postsynaptic element - Ligand gated ion channel with a nicotinic receptor - ACh will work in this receptor to promote depolarization and you establish the communication between the 2 cells - Acetylcholinesterase (AChE) enzyme can break ACh down and you will have choline and acetate again - Choline will be reuptaken to the terminal axon - The nicotinic receptor is a cholinergic receptor located in the skeletal muscle - The nicotinic receptors are sodium channels and ACh works on the nicotinic receptor (sodium ligand gated channel) to promote the depolarization and contraction of the skeletal muscle - Acetylcholine is released from motor axons and will promote the activation of nicotinic receptors in the skeletal muscle which will promote contraction of the skeletal muscle - AChE is responsible for breaking down and metabolizing ACh, therefore if this enzyme is inhibited hyperexcitation in the skeletal muscle will occur - The muscles will be contracting a lot such as a tremor in the skeletal muscle - If we block AChE, we enhance the function of ACh - ACh is also modulating the smooth muscle - In the smooth muscle ACh also promotes contraction through a different receptor - Promotes the gastrointestinal tract, so it is contracting a lot when ACh is working - In our heart, ACh tends to inhibit the function of the heart so it reduces the heart rate and promotes bradycardia (slow heart rate) - Activates skeletal muscle contraction, reduces the activity of the heart in particular the frequency, and promotes the contraction of the GI tract - All functions are regulated but the same neurotransmitter according to the site where they are - Summary: If you inhibit the enzyme that breaks down the neurotransmitter (ACh) than you enhance all of these functions

Answer 70

- An amino acid synthesized from glutamine - Works in different types of receptors - Usually glutamate is an excitatory neurotransmitter works on a specific ligand gated ion channel that promotes depolarization to activate the neurons - Glutamate can be reuptaken in the glial cells, astrocytes are a good example - Convert glutamate into glutamine which is used to synthesize glutamate in neurons - Glutamate is converted to glutamine which can be reuptaken in the presynaptic element - If the glutamate receptor is blocked (an antagonist of the receptor) you are inhibiting the excitatory pathway, therefore you are promoting inhibition of the neural activity - The presynaptic element can not be activated - Ketamine blocks the glutamate receptor

Answer 71

1. CNS - brain and spinal cord 2. PNS A. Sensory Pathways B. Motor Pathways - Somatic Pathway - Autonomic Pathway -> Very close on one side of the spinal cord there is a Sympathetic trunc --> There are ganglions around there ---> Ganglions are structures where neurons can reach them and they can have a synapses and there is another neuron going out

Answer 72

1. Spinal Ganglion - bodies of the sensory neurons - Around the dorsal route of the spinal cord we have a sensory ganglion - In this ganglion we have a soma of the sensory neurons - in the peripheral NS we can have spinal ganglion and they are related with the sensory pathway

Answer 73

- first synapse of the sympathetic branch - > motor - Three anatomical arrangements/different ways to start a synapses in the sympathetic ganglion 1. Can release the second neuron at the same level where it was originated aka synapse in the trunk ganglion at the same level 2. Can have another fiber that goes up or down in the chain to establish another synapse aka synapse in the trunk ganglion is at a higher or lower level 3. Can have a neuron coming from the spinal cord past the first sympathetic ganglion and can establish a synapsis in another sympathetic ganglion

Answer 74

- Sensory nerve fibers from sensory cells - We detect the signals from the external environment and the internal environment - > Both can take the sensory pathway and reach the CNS

Answer 75

- Motor nerve fibers to skeletal - Signals can be detected at the spinal cord and can go up to the brain through motor neurons and come back again. - When we regulate the somatic motor system we are regulating the function of the skeletal muscle - Conscious control, can control it via the cortex of the brain

Answer 76

- motor nerve fibers to glands, the heart and smooth musculature 1. Sympathetic Nervous System - Activated during critical situations - Fight or flight - Activates resources - Stimulation of several functions in the body 2. Parasympathetic Nervous System - Activated at rest - Rest and digest - Regeneration to restore energy - It is a very important component in ex: the digestive tract function - Vegetative aspects of daily life

Answer 77

- Many organs are innervated by both the sympathetic and the parasympathetic nerve, each of them with a reciprocal effect to achieve homeostasis - They “counteract each other” but they are not antagonists instead they are complimentary -> Sympatheticus “speeds up” and Parasympatheticus “slows down”. Ex: If you increase the sympathetic division outflow you will increase the heart rate, but if you need to regulate the heart rate you can inhibit the sympathetic outflow by increasing the parasympathetic outflow and the heart rate will decrease until you reach homeostasis

Answer 78

- Mainly regulates functions of the internal organs and adapts them to the need of the moment 1. The ANS controls the “ Internal Environment” of the body - Regulation of temperature 2. Can detect different stimuli such as chemical parameters - Such as blood pH, partial pressure of Oxygen and CO2 3. Can detect physical parameters that can be detected and regulated - Blood pressure and temperature 4. The majority of the activities are not subject to voluntary control - But there are some humans/animals that can regulate certain ANS functions like their heart rate

Answer 79

- In the periphery, the ANS and the Somatic nervous system (SNS: voluntarily controlled) are almost entirely separated - In the CNS, the ANS and the SNS are intimately connected -> Share the majority of the neurons Ex: If the blood pressure decreases, autonomic reflexes cause the heart to beat faster and more forcefully, and special blood vessels to constrict and the blood pressure is restored

Answer 80

- Sympathetic region is in the thoracic region and lumbar (thoracolumbar) 1. Eye (+) - Promotes the pupil to dilate and get more light - If cat is chasing a mouse it needs more light to see better when escaping Ex: if it is very dark when you are driving and hard to see because little light the sympathetic NS will be activated and your pupils will dilate so you can see better. 2. Salivary Glands (-) - Production or amount is limited - Reduced and very thick not that much water - If cat chasing mouse energy is not used for this because not a priority 3. Lungs (+) - Bronchioles are going to be dilated (bronchodilation) - If cat is chasing mouse, the mouse needs more air to run 4. Heart (+) - Beats in higher frequency and the strength of the contraction increases to pump more blood to the skeletal muscle to guarantee the function - tachycardia - Mouse running from the cat needs skeletal muscle strength 5. Digestive Tract (-) - In general, the stomach, pancreas, etc is going to be reduced during sympathetic activation 6. Bladder (-) - Urinary bladder is going to be filled 7. Adrenal Gland (+) - Going to be stimulated - Epinephrine is stimulated here and it is a component of the sympathetic division

Answer 81

- The preganglionic neuron is located mainly in the brain stem/cranial and in the sacral region of the spinal cord - Usually the preganglionic neuron is pretty long because the autonomic ganglion is located closer to the target cells, or even embedded in the organ - The second neuron aka the postganglionic neuron is shorter because the ganglion is very close to the target cell

Answer 82

1. Eyes (+) - Promotes the contraction of a different group of cells and the diameter of the pupil is less - Not enough light - Constricts the pupil Ex: If there is too much light when you are driving, the parasympathetic NS will activate and constrict the pupil so that you do not get blinded by the light and can see the road. 2. Heart (-) - Decreases the heart rate, sympathetic division is inhibited - bradycardia

Answer 83

- The neurons that regulate the function of the skeletal muscle - The Soma of the neuron is located in the ventral horn of the spinal cord - > Motor neuron leaves the CNS and reaches the skeletal muscle for contraction to occur - only one neuron, no synapses or ganglion in the middle - > This neuron reaches the target cell and the neurotransmitter Acetylcholine and the receptor located in the skeletal muscle is called nicotinic

Answer 84

1. First neuron comes from the CNS and then we have a sympathetic ganglion - > In the sympathetic ganglion, the first neuron will release ACh and then the ACh will act on the nicotinic receptors that are located in the second neuron 2. The second neuron is called the postganglionic neuron and is a adrenergic neuron that will release norepinephrine which will work the target cells/effector organ - > Norepinephrine will work in two subtypes of receptors either in alpha adrenoceptors or beta adrenoceptors 3. Sympathetic division component of the adrenal gland - First neuron comes from the spinal cord and releases ACh - We have chromatin cells in the adrenal medulla and these cells express nicotinic receptors in their cell membrane - So, ACh will work on nicotinic receptors and the chromatin cells will release epinephrine and a tiny amount of norepinephrine - Will travel the general circulation of the blood stream and can reach the alpha and beta adrenoreceptors in the target cells 4. Exception: There is just one group of cholinergic fibers in the sympathetic division and it is an exception to the rule. They regulate mainly the vasculature and sweat glands in the dorsal region of the skin in humans

Answer 85

- Has a first neuron and will reach the parasympathetic ganglia that are very close to the target/effector cells - ACh will be the neurotransmitter and nicotinic receptors will be the receptors in the second neuron - Then this second neuron will release ACh in the target cells and Ach will work on muscarinic receptors (M) Long Steps - Start at the CNS and then we have the first preganglionic neuron called cholinergic because it releases ACh - ACh will work on the second postganglionic neuron and the postganglionic neuron after it is depolarized and the AP are created. - Then, ACh will be released in the target synapses, or around the target cells. - So ACh will work in the effector organs and on muscarinic receptors

Answer 86

- Nicotine is a plant alkaloid derived from tobacco plants - Cholinergic agonists - Is going to make the functions of Acetylcholine - Located in both the sympathetic and parasympathetic divisions (the entire ANS), but mainly in the ganglion synapses (post ganglionary neuron) - Are also expressed in the skeletal muscle(motor endplates) that is part of the somatic nervous system

Answer 87

- Muscarine is a plant alkaloid derived from mushrooms - Cholinergic agonist - That alkaloid is able to work just on cholinergic receptors that express muscarinic receptors - Located mainly in all of the target cells, or effector organs - > Such as in the smooth muscle of the digestive tract, the smooth muscle of the urinary, reproductive tract, cardiac muscle cells and some glands

Answer 88

- mimics the effects of the parasympathetic division - Nicotine and muscarine have no therapeutic interest - Pilocarpine is an agonist of muscarinic receptors - > is used topically in ophthalmology for the treatment of glaucoma (increase intraocular pressure) and as a miotic agent to cause a reduction of the pupil diameter

Answer 89

- Kills the effect of the parasympathetic division - Atropine and glycopyrrolate are antagonists of muscarinic receptors, it blocks them - > are traditionally used during the preanesthesia - Causes tachycardia, bronchodilation, reduction of the gastrointestinal motility - > parasympathetic division does the opposite of this

Answer 90

- Blocks Sodium voltage channels which decreases, or abolishes the speed of conduction of action potentials in peripheral nerves - Regional nerve blocks Ex: Lidocaine - When used, the conduction of painful sensations in the animal is blocked

Answer 91

- Acetylcholine through muscarinic receptors can promote a reduction in the heart rate (bradycardia), so if we enhance the effect of acetylcholine because the enzyme is blocked we get bradycardia - Parasympathomimetic effect copies the effect of the parasympathetic division - Increases the skeletal muscle strength, or neuromuscular end plate synapses - > Activity of skeletal muscles are enhanced because acetylcholine works on nicotinic receptors in the somatic nervous system - Increases the gastrointestinal functions, entire tract is enhanced if we more acetylcholine synapses in the body - Promotes miosis which is a decrease in the pupil diameter (parasympathetic division reduces it) - Drugs that can therapeutically inhibit acetylcholinesterase is Edrophonium IV - Myasthenia Gravis is a disease of the skeletal muscle and Edrophonium IV will be used to test for this

Answer 92

- If glutamate is an excitatory amino acid, then the balance between excitatory and inhibitory pathways might change when you use a blocker in favor of the inhibitory pathway - When we block a glutamate receptor we enhance the inhibitory pathways in the Central Nervous System because the excitatory pathway is blocked - If you block the excitatory pathway, the inhibitory pathway is enhanced and vice versa - Anesthesia - Ketamine is an anesthetic in equines

Answer 93

- In the sympathetic division, the origin is the motor component and the neuron that creates the motor component comes from the spinal cord in the grey matter (center) - It originates from the thorax and lumbar range - Possibility of having a ganglion in the middle, an autonomic ganglion in the sympathetic trunc and then we have the effector organs usually smooth muscle, gland cells and the heart - The preganglionic neuron is cholinergic and has cholinergic receptors - The postganglionic neuron is adrenergic and has adrenergic receptors

Answer 94

- Bind both, norepinephrine and epinephrine. - They are classified into alpha and beta receptors 1. α-adrenoceptors - > α1-AR smooth muscle of the arteriole tissue - > α2-AR in the presynaptic membrane 2. β-adrenoceptors - > β1-AR in the heart - > β2-AR in the smooth muscles of the bronchioles in the respiratory system - > β3-AR - Norepinephrine binds better with a higher affinity to α-adrenoceptors - Epinephrine binds better with a higher affinity to β-adrenoceptors

Answer 95

- Norepinephrine binds better with a higher affinity to α-adrenoceptors - The constriction of blood vessels is mediated mainly by alpha adrenoreceptors - > vasoconstriction - The constriction of the bronchi is due to alpha adrenoreceptors - > bronchoconstriction - Heart has a very limited expression of a-adrenoreceptors

Answer 96

- Epinephrine binds better with a higher affinity to β-adrenoceptors - Epinephrine through mainly b-1 adrenoreceptors, is going to promote all of the functions of the heart - > Heart has a very limited expression of a-adrenoreceptors - Blood vessels have beta adrenoceptors so epinephrine promotes dilation instead of constriction - > vasodilation - Epinephrine in the Bronchi will relax the smooth muscle through beta-2 adrenoreceptors - > bronchodilation

Answer 97

- Drugs that can mimic and promote the functions of the sympathetic division 1. Clembuterol is a B-2 adrenoceptor selective agonist - brochodilation 2. Xylazine, detomidine, romifedine are α2-adrenoceptor selective agonists - Located in the presynaptic membrane and reduces the release of norepinephrine causing sedation and analgesia. - Postsynaptic reduces gastrointestinal motility

Answer 98

1. Acepromazine (ACP) is a a-adrenoceptor nonselective antagonist - Used as a tranquilizer, or preanesthetic drug - Reduces most of the sympathetic division functions 2. Atenolol is a B1-adrenoceptor selective antagonist - Mediate the increase in the strength of contraction and frequency in the heart - Heart arrhythmias

Answer 99

- The pupil diameter is regulated by two groups of muscles a circular and radial muscle - The sympathetic division promotes contraction of the radial musculature it is a smooth muscle - > This effect is mediated by alpha-adrenoreceptors - > When we contract the radial we open the internal diameter of the pupil during the sympathetic activation - When the parasympathetic division is activated the division regulates the circular muscle which promotes contraction through muscarinic receptors - > But this circular muscle reduces the diameter of the pupil which promotes miosis - Both divisions promote contraction, but of different muscles which changes the function

Answer 100

- Norepinephrine released from sympathetic nerves and epinephrine from the adrenal medulla modulate the heart contractility through ß1-adrenoceptors - Norepinephrine promotes arousal of heart activity when it is acting on the postsynaptic α1-adrenoceptors, but inhibits its own release when is acting on presynaptic α2-adrenoceptors - You can inject an animal with an a-2 adrenoreceptor agonist and inhibit the release of norepinephrine. -> Therefore, if norepinephrine is promoting a state of arousal and alertness and it is inhibited the animal is going to fall asleep. - If you block the alpha-1 adrenoreceptor you can also reduce the state of arousal, or alertness and the animal can be tranquilized - > Acepromazine (ACP) can work as an alpha-1 adrenoceptor antagonist

Answer 101

- is an involuntary sequential process as the result of an adequate stimulus to an effector organ - is marked as a fast, predictable, automatic response to changes in the environment, internal or external

Answer 102

1. Monosynaptic Reflex - the simplest reflex - The reflex arc consists of only two neurons - > sensory and motor neuron - This is just a theoretical concept - Source organ is identical with target organ. - Muscle is the source/target organ. - Initiated by stretch receptors - > Muscle has neuromuscular spindles to detect stretch - > Tendon has sensory fibers called Golgi’s corpuscles.

Answer 103

1. Stretching of the muscle stimulates a sensory receptor such as a muscle spindle of the sensory nerve 2. Reflex arc action potentials are conducted afferently by the sensory nerve to the integrating center of the spinal cord, transmitted directly by the α-motoneuron, and efferently to the effector at the location of its origin, the muscle. 3) The muscle contracts and thus, counteracts the initial stretching

Answer 104

- hitting the tendon of the quadriceps muscle causes straightening of the knee-joint - > Need to contract the quadriceps to do this

Answer 105

- Source of stimulus and target organ may differ. | - Reflex arc includes more than one synapse

Answer 106

1. Pupillary reflex - light exposure causes contraction of the pupil 2. Corneal reflex - touch of the cornea causes closure of the eye lid 3. Anal reflex - stroke of the perineal areas causes contraction of the external anal sphincter muscle

Answer 107

- If we hold a weight in our hand, the biceps will be extended, or stretched - If the skeletal muscle is stretched that will activate the muscle spindles which will trigger a sensory signal In the spinal cord there will be a synapses that will release a neurotransmitter and depolarize a motor neuron - The motor neuron will leave spinal cord through the ventral horn and then it will go back to the nerves and go to innervate the biceps - The response of the biceps is to contract, once it is contracted you can get the flexion of the elbow - This can not happen if we do not relax the triceps - Therefore, in the spinal cord there is an interneuron that is an inhibitory neuron - The same sensory pathway that was activating the motor neuron to contract the bicep is also activating another interneuron that is inhibitory and inhibits the motor neurons that activates the extensors - Therefore, the tricep will relax - Usually interneurons in the CNS are inhibitory neurons aka they will release a neurotransmitter that will promote hyperpolarization in the postsynaptic element -> Can do this by releasing GABA, or glycine --> Both promote hyperpolarization of the postsynaptic neuron

Answer 108

- In the urinary bladder have an external urethral sphincter formed by skeletal muscle (voluntary can control it) -> Can control it because it’s nicotinic, can contract it and nothing will happen activate the cholinergic fiber --> Somatic component - There is an internal urethral sphincter made out of smooth muscle that can not be regulated ANS does that - Ureters bring urine into the urinary bladder during that time the sympathetic division is promoting the filling of the urinary bladder -> That is because we have B-2 adrenoreceptors of the wall in the urinary bladder and the activation of these receptors relaxes the smooth muscles so there is no resistance to receive the fluid and can start filling the urinary bladder -> At the same time the internal sphincter by the same sympathetic activation is contracted (a-1 adrenoreceptors) - The pressure inside the structure starts to increase when bladder fills - We have stretch, sensory and mechanic receptors inside the bladder so they can detect the stretch on the wall of the urinary bladder - Reflex arc occurs when we activate the sensory pathway and we have the sensory ganglion and will reach the spinal cord. -> The section is in the sacral region which activates the parasympathetic division. - parasympathetic division is involved in the emptying process - The sensory impulses promote an interneuron which activates the parasympathetic fibers. - Activates the first neuron with parasympathetic ganglion and then the second neuron the postganglionic neuron and releases ACh from the parasympathetic division at the effector level - The receptor in the smooth muscle of the urinary bladder is muscarinic - The wall of the urinary bladder will contract and at the same time the pressure increases and the force of the internal sphincter is not as high, so the pressure will overcome the function of the internal sphincter - The somatic component is inhibited by an interneuron which causes the external sphincter to relax and if the cue is too long the urine will be released Summary: has autonomic components and somatic components that work together

Answer 109

1. Skeletal striated muscle 2. Cardiac striated muscle 3. Smooth muscle

Answer 110

1. Actin. 2. Myosin. - *The organization of the myofilaments forms a repetitive pattern of dark and light bands perpendicular to the longitudinal axes of the fibers in striated muscles*

Answer 111

1. Bundle of muscle fibers 2. Myofibril 3. Myofilaments 4. Sarcomere

Answer 112

1. Capillary | 2. Mitochondrion

Answer 113

1. Cell Membrane | 2. T-tubule

Answer 114

1. Sarcoplasmic Reticulum

Answer 115

- the basic functional unit of the striated muscle - I band contains only thin (actin) filaments - A band contains thin (actin) and thick (myosin) filaments - H zone contains only thick (myosin) filaments - > cross bridges between myosin and actin

Answer 116

- Actin - Actin is the active site to bind to myosin - Tropomyosin - Troponin: 3 subunits - > C (Ca2+) - > I (inhibitory) - > A (actin)

Answer 117

- myosin - heavy chains (tail) - light chains (head)

Answer 118

1. Binding of ATP to the myosin head breaks the cross-bridge between actin-myosin. 2. Degradation of ATP via ATPase (Mg++ dependent) straightens (90°) the myosin heads 3. The myosin head binds to actin when Ca2+ concentration increases. 4. The myosin head bends - Without ATP, the binding is very strong and stable - > Rigor Mortis

Answer 119

- called excitation/contraction coupling 1. AP of skeletal muscle (and nerve) is much shorter 2. Latency period, or mechanical response to electrical stimulation of the skeletal muscle is shorter 2. Duration of contraction of the skeletal muscle is shorter

Answer 120

- In the resting state (-90mV), there is a high concentration of Ca2+ in the ECF and the L system (sarcoplasmic reticulum) - Depolarization of the cell membrane, including the T-System, triggers the influx of Ca2+ from the ECF and the release of Ca2+ from the L-System (sarcoplasmic reticulum) - The resulting contraction is delayed and it lasts if the calcium concentration in the ICF is high - Repolarization occurs when Ca2+ is transported back to the ECF and is pumped into the L-System

Answer 121

- Ca2+ is the mediator of BOTH, the electrical stimulation and the mechanical contraction in cardiomyocytes (Heart) - calcium is responsible for the long duration of the cardiac APs - It is the Mediator between electrical stimulation and contraction - Ca++ is released from: - > Sarcoplasmic reticulum (L-system: intracellular) - > Extracellular Transverse tubule - plays a MAJOR PART - > Without extracellular Ca2+, depolarization occurs without contraction - > Ca2+ concentration increases 100 folds in less than 100 msec - Ca2+ is responsible for the strength of contraction. - Ca2+ blood level vital for normal contraction

Answer 122

- depolarization of the cell membrane in the T system is sensed by voltage-sensitive dihydropyridine receptors (DHPR) - Then, a conformational change occurs in the DHPR - Since they are arranged in rows with the ryanodine receptor (RRY-1) in the sarcoplasmic reticulum (L system), the RRY-1 opens and calcium is released to the cytoplasm

Answer 123

- the dihydropyridine receptors (DHPR) in the myocardium is part of a voltage-gated calcium channel (L-Type) in the sarcolemma that opens in response to action potential. - Then, calcium influx from the extracellular liquid occurs and these increase in cytoplasmatic calcium concentration causes, trough ryanodine receptor (RRY-2), the release of more calcium from the sarcoplasmic reticulum (L system). - > This process is call calcium induced calcium release

Answer 124

1. Discharge of motor neuron 2. Release of transmitter (Acetylcholine) at motor endplate. 3. Binding of ACh to Nicotinic receptors. 4. Inc. Na+ and K+ conductance in endplate membrane. 5. Generation of endplate potential (AP) 6. Generation of AP in muscle fibers. 7. Inward spread of depolarization along T tubules

Answer 125

1. Release of Ca2+ from terminal cisterns of sarcoplasmic reticulum and diffusion to thick and thin filaments. 2. Binding of Ca2+ to toponin C, uncovering myosin-binding sites of actin. 3. Formation of cross-linkages between actin and myosin and sliding of thin on thick filaments (contraction) producing movement

Answer 126

1. Ca2+ pumped back into sarcoplasmic reticulum 2. Release of Ca2+ from troponin 3. Cessation of interaction between actin and myosin

Answer 127

- The synapse connecting a motor neuron and the skeletal muscle fiber is called the Motor End Plate - Acetylcholine is the neurotransmitter and the receptor is nicotinic

Answer 128

- consists of one motor neuron | and the muscle fibers that it innervates

Answer 129

- consists in many motor units of different sizes: 1. Low number of fibers per motor nerve. - Precise movements requiring little force. 2. High number of fibers per motor nerve. - Great force but not precise movement.

Answer 130

- electrical synapse - In the heart, all muscle cells are electrically connected to their neighboring muscle cells - > This arrangements is called a functional syncytium. - The syncytium acts as a single unit that is always all cells depolarize and thereafter repolarize together - intercalated disks connect the ends of neighboring muscle fiber branches - gap junctions are open pores connecting the cytosol of neighboring cells - via gap junctions, or joint channels, the APs jump from cell to cell - RESULT: One AP depolarizes the entire synctium!

Answer 131

- Smooth muscle fibers also perform contraction with actin and myosin filaments. - > However, they are not arranged in sarcomeres. - Contraction is stimulated by neurons signal, depolarization, hormones, stretch, and in several other ways. - Contraction is triggered by influx of Ca++ from the ECF. - There is no tubular system. - Calmodulin, a protein, plays a similar regulatory role as the troponin in the striated muscle does.

Answer 132

1. Actin and myosin are loosely arranged around the periphery of the cell, held in place by protein dense bodies 2. The arrangement of the fibers causes the cell to become globular when it contracts 3. Myosin can slide along actin for long distances without encountering the end of a sarcomere 4. Smooth muscle myosin has hinged heads all along its length

Answer 133

- The complex calcium-calmodulin activates the myosin light chain kinase that phosphorylates myosin and causes contraction 1. intracellular calcium concentrations increase when calcium enters the cell and is released from the sarcoplasmic reticulum 2. Caclium binds to calmodulin (CaM) 3. Calcium-calmodulin complex activates the myosin light chain kinase (MLCK) 4. MLCK phosphorylates light chains in myosin heads and increases myosin ATPase activity 5. Active myosin crossbridges slide along actin and create muscle tension

Answer 134

- The efflux of calcium to the extracellular fluid/sarcoplasmic reticulum and the dephosphorylation of myosin by the myosin phosphatase, contribute to decrease smooth muscle tension 1. free calcium in cytosol decreases when calcium is pumped out of the cell and back into the sarcoplasmic reticulum 2. Calcium unbinds from calmodulin (CaM) 3. Myosin phosphatase removes phosphate from myosin which decreases myosin ATPase activity 4. Less myosin ATPase results in decreased muscle tension

Answer 135

- Smooth muscle cells can develop a slow wave potential - These potentials will initiate an action potential if they reach the threshold - The possibility does exist to increase/decrease tension without changing the membrane potential, when the smooth muscle is activated/inhibited by a chemical signal 1. Slow Wave Potentials - fire action potentials when they reach the threshold 2. Pacemaker Potentials - always depolarize to the threshold 3. Pharmacomechanical Coupling - occurs when chemical signals change muscle tension without a change in the membrane potential

Answer 136

1. Isotonic - length changes - tension is constant 2. Isometric - length is constant - tension changes 3. Auxotonic - both the length and tension changes

Answer 137

- Maximum tension is achieved when all myosin heads are involved in the contraction - Overlap of actin filaments or free myosin heads decrease the tension - Within its physiological working range, the force of a skeletal muscle remains almost constant

Answer 138

1. Active tension - is determined by the number of actin-myosin cross-bridges 2. Passive Tension - is developed when the muscle is stretched in the resting state - It is determined by the elastic component. 3. Total Tension - the sum of the active and passive tension

Answer 139

1. Skeletal Muscle - plateau range 2. Cardiac Muscle - ascending limb without plateau

Answer 140

- each action potential causes the release of a certain quantum of Calcium which in turn, causes a single twitch of a certain force - As the released quantum is always the same, the resulting force is also always the same

Answer 141

- the total force of contraction of a whole skeletal muscle is determined by: 1. The number of motor units activated: - the more motor units are recruited the stronger is the resulting contraction. 2. Frequency of action potentials: - if two APs arrives in a short sequence (the first contraction has not been fully relaxed), the second contraction overlays the first one, and the resulting force increases. - The higher the frequency is the higher the muscular force (within working range of the muscle).

Answer 142

1. Summation: - if there is not enough time for the muscle fiber to relax, because the other AP arrives already during the twitch, the resulting superposition of the twitches cause a further shortening of the muscle fiber (mechanical summation) 2. Tetanus - if the frequency of APs increases that high that the intervals between APs becomes less than 1/3 of the time required for a single twitch, the twitches fuse and cause a maximum contraction known as TETANUS - > myotoxin a gram positive bacteria causes this

Answer 143

1. Cardiac Muscle - all or none response - if we increase the frequency of the stimulus there is no change - tetanus is not possible in the heart 2. Skeletal Muscle - a graded response - proportional to the intensity of the stimulus applied - if we increase the AP frequency to very high tetanus can occur

Answer 144

- prevention of tetanus in the cardiac muscle - in the absolute refractory period no superseeded excitation is possible - in the relative refractory period only very strong stimuli can trigger an AP - At the beginning of the relative refractory period the intensity needs to be very high to get a response - When it gets closer to resting membrane potential, the magnitude of the stimulus can be lower

Answer 145

- begins a few milliseconds after the AP begins and ends a few milliseconds after the AP ends - The duration of the contraction is mainly a function of the duration of the AP - > Atria: ~200 msec. - > Ventricle: ~300 msec. - There is a delay after the electrical activity in order to develop tension and contraction happens always after the electrical activity - > electrical activity in the cardiac muscle (200 ms) is wider (longer duration) than in skeletal muscle (10 ms) or the nerve (1 ms)

Answer 146

- it is a closed system containing blood within the heart and blood vessels, including arteries, veins and lymphatics (lymph instead of blood) - heart acts as a pump - > Contains two chambers (atria) that receive the blood from the body and two well-developed muscle walls chambers (ventricles) that propel the blood towards the body - blood vessels are a series of tubes with different grades of diameters and elasticity that either conduct or drain the blood to/from the body

Answer 147

1. Systemic - distribute blood to the whole body - oxygenated blood flows in the aorta 2. Pulmonary - distribute blood to the lungs - deoxygenated blood flows in the pulmonary artery

Answer 148

- the presence of valves ensure that the blood flow has only one direction - the driving force is a pressure gradient - > high to low pressure

Answer 149

- Exchange of molecules and ions take place here by diffusion

Answer 150

1. veins - drain blood towards the heart 2. Arteries - conduct blood towards the body

Answer 151

1. The most important function is the transport of blood! 2. Nutrients from the digestive tract to the tissues - To and from organs that transform and store nutrients 3. Waste products from tissues where they are produced to the organs where they are excreted. 4. Oxygen from lungs to tissue 5. Carbon dioxide from tissues to lungs. 6. Heat from the tissues to skin and respiratory organs where it is dissipated. 7. Hormones from the endocrine glans to target cells 8. White blood cells and antibodies for protection against infection.

Answer 152

- It is located in the thoracic cavity - It is cone-shaped with the base at the top and the apex downwards and to the left - The large blood vessels enter and exit the heart at its base - Two different circuits with two different pressure, to guarantee a lower perfusion pressure in the lung, avoiding the development of pulmonary edema. - > pulmonary (the right side) is under lower pressure and systemic (left side) is under more pressure - The heart valves are pressure-operated

Answer 153

1. Horse - the heart is vertical 2. Cattle - the heart is almost vertical 3. Pig, dog and cat - their hearts are progressively more obliquely located

Answer 154

- The pericardium covers the heart - It has two layers: 1. Visceral - attached to the epicardium 2. Parietal - fibrous layer, “attached” to the thorax wall - The pericardium restrict the size of the heart, thus preventing acute and excessive stretching (length/tension relationship) of the myocardium - If enlargement occurs gradually, the pericardium also stretches - The pericardial cavity contains fluid to reduce friction

Answer 155

1. AVC: anterior (cranial) vena cava. 2. PVC: posterior (caudal) vena cava 3. RA: right atrium. LA: left atrium. 4. RV: right ventricle. 5. LV: left ventricle. 6. A: aorta. 7. PA: pulmonary artery

Answer 156

- the valves act as inlet and outlet valves for the ventricles 1. In the Right Ventricle - In valve is the tricuspid, or atrioventricular valve - out valve is the pulmonary, or semilunar valve 2. In the left ventricle - In valve is the bicuspid, or atrioventricular valve - out valve is the aortic, or semilunar valve

Answer 157

1. The attachment of the valves to the fibrous rings. 2. The chordae tendineae (tough fibrous cords) and the papillary muscle, attached to the edge of atrioventricular valves. 3. The passive and active components of the valves structure

Answer 158

1. Passively direct the blood flow according to the pressure gradient. - They are unidirectional valves 2. Electrical insulation. - contribute to the sequential, electrical events followed by mechanical events

Answer 159

1. Semilunar - guides the blood from the ventricle into the large arteries (aorta and pulmonary artery) during the systole 2. Atrioventricular valve - guides the blood from the atrium into the ventricle during the diastole

Answer 160

- Diastole means relaxation of the ventricles (filling with blood) - > Ventricle walls are relaxed, blood coming in, they are filling - > Pressure gradient from the atria toward the ventricles - Systole = contraction - > Goes to the left - > higher pressure inside the ventricle and goes toward the atria - > Blood flow goes from ventricles to the atria - Diastole and systole in the ventricles*

Answer 161

- Striated muscle. - Well developed T-tubule that connects to the extracellular liquid - Composed by individual myocytes with branches. - Has a functional syncytium - > Gap junctions in the intercalated disks, allow action potentials to be propagated from cell to cell. - The fibrous structure between atria and ventricles restrict the conduction to a specialized conduction system - Ventricles display a thicker wall (particularly the left) than atria - > atria has a smaller force of contraction in comparison to ventricles

Answer 162

1. Contractile - they represent 99% of the cardiomyocytes - Display a stable resting membrane potential and must be stimulated in order to activate the contractile machinery 2. Autorhythmic cells, or Non-contractile cardiomyocytes - they are concentrated in certain regions of the heart - they generate action potentials spontaneously by undergoing slow depolarization (unstable membrane resting potential) and conduct the signal through the heart

Answer 163

1. Phase 4 - unstable membrane potential. - Prepotentials - > When the membrane potential reaches -65 mV after repolarization, ion channels that are permeable to Na+ and K+ opens - > These channels (h: hyperpolarization, or f: unusual or “funny”) open at negative potentials and close at positive - > This funny current starts a slow prepotential - --> the slow depolarization between two action potentials that corresponds with the diastole are called pacemaker potentials, or prepotentials - > Transient (T) Ca2+ channels open, finishing the prepotential and reaching the threshold 2. Phase 0: depolarization. - Slow Ca2+ current (inc Ca2+) - long lasting Ca2+ channels 3. Phase 3 - repolarization - K+ voltage channels open (inc K+)

Answer 164

1. Phase 0 - Depolarization. - Strong but brief Na+ current - high permeability to sodium 2. Phase 1 - Partial repolarization. - Na+ voltage channels inactivation - reach positive currents 3. Phase 2 - Plateau phase Influx of Ca2+ and efflux of K+ - the influx and efflux of positive charges are in balance 4. Phase 3 - Repolarization - K+ voltage channels open 5. Phase 4 - resting membrane potential. - The high K+ permeability and the Na+/K+ pump contributes to maintain the resting membrane potential.

Answer 165

- The heart can beat regularly without nervous impute - However, the heart frequency is under the autonomic nervous system regulation: 1. Sympathetic stimulation - epinephrine and norepinephrine causes more rapid depolarization and tachycardia - steeper pacemaker potential slope - higher heart rate 2. Parasympathetic, or vagal stimulation - acetylcholine causes hyperpolarization and bradycardia - less steep, or more shallow pacemaker potential slope - lower heart rate

Answer 166

- Epinephrine interacts with β-adrenoceptors (β1-AR) - Then, a series of G-protein-mediated changes leads to activation of adenylyl cyclase and the formation of cyclic adenosine monophosphate (cAMP) - The latter acts via protein kinase A to stimulate metabolism (left) and phosphorylate the Ca++ channels proteins (right) - The cell signals enhance: - > The opening of Ca++ channels and the inward movement of Ca++ ions from both, the extracellular compartment and the intracellular compartment - > Thus, the pacemaker potential slope is steeper and the contraction is enhanced - > The myosin ATPase activity - > The relaxation, or lusitropic effect by phosphorylating phospholamban (PL) in the sarcoplasmic reticulum (SR) - > Phosphorylating Phospholamban promotes the function of the Ca++ pump in the Sarcoplasmic reticulym

Answer 167

- ACh activates the muscarinic receptors (M2) in the pacemaker cells - This causes the efflux of K+ through G protein-coupled inwardly rectifying potassium channels and hyperpolarization of the cell membrane - > the cells are less sensitive to stimuli - Therefore, the pacemaker potential slope is less steep and the rate of cell firing is reduced causing bradycardia - cAMP signals can create, or enhance currents in the cell

Answer 168

1. Sinoatrial node - pacemaker - right atrium between both cava venous 2. Atrioventricular node - has a delay - Slow conduction - atrium septrum 3. Bundle of His - penetrates the fibrous tissue that isolates (electrically) the atria and ventricles. - Two branches: left and right side of the interventriculer septum - base of the heart 4. Purkinje fibers - has a large diameter, therefore they conduct action potential faster - ventricular wall

Answer 169

- the sinoatrial node normally determines the heart rate by generating a higher rate of action potentials (APs) - > depolarizes at the highest rate

Answer 170

- If the sinoatrial node fails to generate APs then the atrioventricular node, the bundle of His and its main branches or Purkinje fibers take over and generate “Auxiliary” Pacemakers generating APs that substitute the missing sinoatrial APs

Answer 171

1. The sinoatrial node (70) - normally determines the heart rate by generating the highest rate of Aps - The SA node dominates all other pacemakers because of its speed - when it fires, an AP runs through the entire heart and resets all other pacemakers 2. The rate of the atrioventricular node is lower (40-50) - the AV node only takes over if the SA node fails 3. The Bundle Of His, Bundle Brances and Purkinje fibers generate the lowest rates (25-40) - they take over if the AV node fails

Answer 172

- When the SA node generates an action potential (AP), the AV node and the others auxiliary pacemakers, are still slowly depolarizing (phase 4). - The SA node AP reaches the AV nodes and accelerates the AP reaching the threshold and generates an AP due to the stimulation of the SA node - “The faster pacemakers dominates the slower one” - > SA nodes create APs very fast and do not allow the rest to create APs - > as long as the SA node dominates, it leads APs and electrical activity

Answer 173

- The action potentials from the SA node only pass to the ventricles through the Bundle of His, after the AV node has delayed the conduction - Thus, the sequential contraction of first the atria and then the ventricles, allows the atria to pump blood into the ventricle - Promote the depolarization and the mechanical activity from the sinoatrial node - Depolarization second in the ventricular cells causes a contraction in the ventricle - > Needs to go in that order or else can not get enough blood out - the electrical and the conductivity of the atria is followed by the electrical and the contractile conductivity of the ventricle - electrical activity is followed by mechanical activity (contraction)

Answer 174

- purkinje fibers are part of the genesis and conduction system - penetration level determines the pattern of the electrocardiogram, or the depolarization of the ventricle wall 1. Primates and carnivores, or Group I - The Purkinje fibers do not penetrate the entire thickness of the myocardium 2. Pigs and other mammals (ungulates, whales), or Group II - the Purkinje fibers penetrate the entire thickness of the myocardium

Answer 175

1. Hormones - catecholamines 2. Electrolytes - Na+, K+ and Ca2+ 3. drugs

Answer 176

1. Parasympathetic Nerve - left and right atrium - sinoauricular node - atrioventricular node - limited innervation of ventricles - vagus nerves decrease the rate of contraction - > regulating the frequency of firing, but not the force of contraction 2. Sympathetic Nerves - left and right atrium - sinoauricular node - atrioventricular node - left and right ventricle! - nerves increase the rate and force of contraction

Answer 177

1. Sympathetic Nerves INCREASE - Heart rate = Chronotropic - speed of conduction = Dromotropic - Excitability = bathmotropic - force of contraction/contractility = inotropic - > contractility is the pumping ability of the heart 2. Parasympathetic Nerves DECREASE - Heart rate = Chronotropic - Speed of conduction = Dromotropic - Excitability (atrium) = Bathmotropic - Limited effect on the contractility/force of contraction of the ventricle = Inotropic

Answer 178

- if we activate the sympathetic division, it releases norepinephrine - this will cause a steeper depolarization aka the prepotential will be steeper which is due to: - > increases of Na+ and Ca2+ influx - > decrease of K+ efflux - > heart rate increases

Answer 179

- if we activate the parasympathetic division, it will release Acetylcholine - which causes a flatter depolarization, or prepotential due to: - > increases the K+ efflux causing hyperpolarization - > decreases Ca2+ influx - > heart rate decreases

Answer 180

- Results in larger stroke volume for any given end-diastolic volume - > Norepinephrine - > isoproterenol (B-adrenoceptor agonist) - > cardiac glycosides (digitals) - > pimobendane (inhibitor of phosphodiesterase 3)

Answer 181

- Results in smaller stroke volume for any given end-diastolic volume - > Propranolol (B-adrenoceptor antagonists) - > barbiturates and propofol (general anesthetics) - > Heart failure: cardiac hypoxia, myocarditis, valve defects, toxic reactions, electrolyte imbalance

Answer 182

- smaller animals have higher metabolic rates and therefore higher HRs - larger animals have slower metabolic rates and slower HRs - are also different in poikilothermic and exotic animals

Answer 183

- When the SA node triggers an action potential, a wave of depolarization runs around the entire heart - The number of fibers involve and the direction of the depolarization wave change continuously during the heart cycle - The strength of the electrical signal depends on the number of depolarizing cells - The maximum recorded potential cannot exceed the maximum generated potential - The recorded potential can be much lower than the generated potential and could even not be registered at all due to the direction of the depolarization in relation to the direction of the measurement

Answer 184

- Ionic differences in the extracellular fluid can be measured as electrical potential - The differences only occur during depolarization and repolarization - Once either depolarization (depolarized state) or repolarization (resting state) is completed, there is no difference in the extracellular fluid and consequently the electrical potential is 0 mV

Answer 185

1. The magnitude, or potential voltage of the de/repolarization at a particular given time. 2. The direction of the de/repolarization at a particular given time. 3. The orientation of the plane

Answer 186

1. If we have a Polarized membrane - at the baseline - under resting conditions - no difference in charge between the two electrodes - Isoelectric, or at 0 2. Depolarization - vector has positive deflexion occurs 3. Polarized membrane - no deflexion - back to the baseline 4. Repolarization - Vector has a negative deflexion 5. Polarized membrane - back to the baseline (0 mV) - no difference between the two electrodes

Answer 187

- Three electrodes are connected to the limbs forming an almost equilateral triangle with the heart in its center - Bipolar recording: 1. Lead I - negative electrode placed in the right forelimb - positive electrode placed in the left forelimb * 2. Lead II: - negative electrode placed in the right forelimb - positive electrode placed in the left hindlimb* 3. Lead III - negative electrode placed in the left forelimb - positive electrode placed in the left hindlimb 4. The Ground Electrode - A fourth electrode is connected to the right hindlimb - It is grounded to eliminate any external artificial electrical signal - Without it, the body acts as an antenna and picks up these signals that are much higher than the cardiac signal

Answer 188

- The electrode must be connected in the right order. - > If they are swapped, then the trace will be modified - For this reason, the leads have a polarity that is one negative and the other positive - If we have a positive signal caused by a depolarization vector the head will be positive and if this vector is orientated towards the positive electrode (same direction of the “telescope”) you get a positive trace, or upward deflection in the heart

Answer 189

- Unipolar leads - Each recording requires a different electrode and a negative electrode which is established by connecting two electrodes - This type of recording is called “unipolar”. - The advantage of this methods is that it generates larger signals, or an augmented signal as the negative electrodes consists of two electrodes and thus collects more currents - > detects signals at a higher voltage

Answer 190

- "telescope" from the left hindlimb up - paper speed on x axis and is about 25, or 50 mm/sec - voltage, or amplitude on the Y axis 1. Wave - a positive or negative deflection 2. P Wave - depolarization of the atria 3. QRS wave - depolarization of the ventricles -> Q is depolarization of the septum -> R is depolarization of the walls -> S is depolarization of the base. 4. T is ventricular repolarization 5. Segment - isoelectric period, or distance/time between two waves Ex: segment between S and T 6. Interval - period of time that includes one or more waves - Consists of one or more waves and segments Ex: PQ interval

Answer 191

- The unipolar (Goldberger) method of ECG recording provides stronger signals - if you compare lead I and 3 with aVr and aVf - > the unipolar leagues are stronger - Lead II and aVf are almost similar - > both seen from the left leg! - aVr and aVf are mirror images of each other - > In aVf goes from the left leg and seeing the head of the arrow so it is a positive deflexion upwards - > in aVr observe the negative tail of the arrow from the right shoulder, therefore it is a negative deflexion downwards

Answer 192

- Leads placed on the chest close to the heart - it records the electrical events in more details - This method is less common in veterinary medicine - However, precordial leads can be used as part of the clinical evaluation of chamber enlargements

Answer 193

- bipolar chest leads used in large animals - to evaluate heart rhythm - arrange the same electrodes for lead 1 and lead 2, but do not use leads - > instead create the triangle between the base of the heart and the apex 1. Lead I - the negative electrode is placed in the right forelimb - > in the caudal section of the jugular groove - the positive electrode is placed on the left *forelimb* - > on the left side of the thorax - anywhere in the left hindlimb 2. Lead II - the negative electrode is placed in the right forelimb - > in the caudal section of the jugular groove - the positive electrode is placed on the left *hindlimb* - > on the left side of the thorax - anywhere in the left forelimb

Answer 194

- depolarization of the atria | - Begins with the first upward deflection from the base line and ends with the return to base line

Answer 195

- corresponds to the depolarization of AV node and Bundle of His - The signal is too small to generate a wave - contraction of the atria corresponds here

Answer 196

- time from the beginning of the atrium depolarization (P wave) to the ventricular depolarization (Q wave) - > it is measured from the first upward deflection of the P wave at the base line to the first deflection of the QRS complex, whether negative (Q) or positive (R) - If there is no visible Q wave it is called the PR interval

Answer 197

- depolarization of the ventricle - Q wave is the depolarization of the septum - R wave is the depolarization of the left and right ventricle walls - S wave is the depolarization of the final depolarization of the ventricle - > base of the left ventricle - It is measured from the base line of the first deflection of the QRS complex, whether negative or positive to the eventual return to the base line

Answer 198

- ventricles remain depolarized and corresponds with the contraction - > contraction of the ventricle occurs in this time frame - It is measured from the end of the S wave to the beginning of the T wave

Answer 199

- repolarization of the ventricles - The atria repolarizes earlier but the signal is too small to be recorded - it can be positive, negative or even biphasic in dogs and cats - > In HUMANS it is positive only!!!

Answer 200

- two axis in an ECG -> Y is the amplification, or magnitude of the wave -> x is the time - To get comparable results, the ECG recorder must be calibrated - The amplification, or vertical deflection per millivolt must be adjusted -> A standard amplification is 10 mm per 1 mV, or 1 cm per 1 mV

Answer 201

- To get comparable results, the ECG recorder must be calibrated - A low speed offers a better general idea of rhythmic events (heart rate) and makes it easier to reveal random events such as extra systoles - > the waves are very close together - A higher speed shows more details - > the waves are further apart from eachother - Standard speeds are: - > 5 mm/sec - > 10 mm/sec - > 25 mm/sec (lower speed clinical setting) - > 50 mm/sec (higher speed clinical setting)

Answer 202

1. 6 seconds rule - there are marks on the top of the ECG paper that represent a 3 second period - You count the number of cycles in 6 seconds and multiply that by 10 to get the total HR - Particularly useful for low heart rates. 2. Paper speed - Count the number of cycles in 1 sec aka a length of 50 mm and multiply by 60 - Count the number of cycles in 2 sec aka a length of 100 mm and multiply by 30 - Count the number of cycles in 3 sec aka a length of 150 mm multiplied by 20 - > Higher numbers are more accurate - The lower the heart rate is, then the longer the trace length should be considered

Answer 203

1. Benefits: - ECG deflections correspond to specific electrical events in the heart - Timing and duration of these deflections can be calculated and be compared with standard values. - Provides valuable information to evaluate the heart rhythm 2. Limitations: - ECG provides partial information about the mechanical events in the heart

Answer 204

- The electrical heart axis is an average of all depolarizations in the heart, and thus it refers to the direction of the general depolarization wave (vector) front - > Because the left ventricle has the highest muscle mass (thickest) it generates the strongest signal - -> the physiological orientation of the heart vector points normally from the right shoulder to the left leg - Alterations in the depolarization (block, hypertrophy, etc) can change the direction - Determination of the electrical heart axis: - > Because there is only one electrical heart axis, it does not matter which ECG recording is used for its determination, either Einthoven or Goldberger. - > In the Einthoven leads, it is best to use the two largest recording of the R waves - > In the Cabrera circle, it is best to use two ECG planes which are vertical, or perpendicular to each other - --> Lead I and aVf.

Answer 205

1. The voltage (mV) value of the R wave in lead I, II, and III is measured and then transferred into the system of coordinates on the graph - Only 2 values are required 2. Then, a line is drawn from each arrowhead vertical, or perpendicular to the lead plane. 3. Finally, the cardiac vector is drawn from the center to the intersection of the three, or could be just 2 values - The angle between lead I and the cardiac vector is the heart axis - In a dog the normal range is ~40-100° and in a Cat it is ~0-160° - The heart axis can deviate from physiologic angle due to: - > Hypertrophy of one ventricle - --> The angle is shifted towards the hypertrophic side because more muscle and longer depolarization - > Failure in the conduction system such as a Bundle block (bundle of his not conducting correctly) aka the “blocked” side depolarizes later

Answer 206

- a combination of the Einthoven and Goldberger planes - To determine the electrical heart axis, two planes that are vertical to each other are used - > aVf and lead 1 - The above ECG shows all 6 Einthoven and Goldberger recordings - The plane of lead I is horizontal and the plane of aVf is vertical, there is a 90° angle/they are perpendicular between the two planes - The maximum potentials of the R waves in lead I and aVf are measured and transferred into the Cabrera Circle diagram

Answer 207

- usually on the right hand side we can have a shift of the heart - Amplitude - > more muscle tissue generates a strong signal and as a result deep S waves are observed in Leads I, II, III and aVf - Timing - > if only one side is affected (the right ventricle) the timing of the depolarization changes as well because more muscle at the right side increases the depolarization time - Both effects results in a shift of the cardiac vector - > if the hypertrophy is at the right side, the vector shifts to the right

Answer 208

- An electrical event is followed by a mechanical one. | - The pumping function creates a pressure gradient that guaranties the blood flow.

Answer 209

- the ventricles contract and eject blood to the aorta and pulmonary arteries 1. Isovolumetric ventricular contraction 2. Ventricular Ejection - when the ventricle contracts, blood is ejected into the circulation - This active phase is called systole - During the systole both AV valves are closed, thus preventing a back-flow into the atrium - Both semilunar valves are open, allowing the blood to leave the ventricle

Answer 210

- the ventricles relax and fill with blood 1. Isovolumetric ventricular relaxation - transition from the previous systole 2. Rapid ventricular filling. 3. Atrial contraction or atrial systole - after an ejection is completed, the ventricles relax and fill again - This passive phase is called diastole - During the diastole both semilunar valves are closed in order to prevent a back-flow of the ejected blood into the ventricles - Both AV valves are open to allow blood flowing from the large veins through the atrium into the ventricle

Answer 211

- usually the terms systole and diastole stand for the ventricles. - Atria have also a systole and a diastole, but they are shorter and begin and end before the related ventricular actions

Answer 212

- because the ventricle continues filling up to the very end of the diastole, the enddiastolic volume is the maximum volume of the entire cardiac cycle.

Answer 213

- the lowest ventricular blood volume is achieved at the end of the systole, called endsystolic Volume

Answer 214

- the volume of blood ejected during the systole, called stroke volume, is the difference between enddiastolic volume and endsystolic volume

Answer 215

- number of heart beats (contractions) per unit of time

Answer 216

- the volume of blood ejected per minute= heart rate x stroke volume.

Answer 217

- are physiological noises generated by oscillation of blood (turbulent flow) and vibrations of muscle and valves - Valves are involved in the generation, but they are NOT the source of the heart sound

Answer 218

- three out of the four heart sounds are diastolic sounds 1. S1 - systole - is associated with the closure of the AV valves (lub) and is typically loudest over the mitral and tricuspid valve areas - > coincide with the closure of AV valves and ventricle contraction - Pulse occurs just after S1 2. S2 - diastole - is associated with the closure of the semilunar valves (pulmonic and aortic valves) (dub) and is typically loudest over these valve areas - > coincides with the closure of the semilunar valves and the interruption of blood flow 3. S3 - diastole - low frequency, diastolic sound associated with rapid ventricular filling - blood inflow from the atria - Pathological in small animals. 4. S4 - diastole - low frequency, diastolic sound associated with atrial contraction. - contraction of the atria - Pathological in small animals

Answer 219

- a heart murmur is defined as a prolonged series of auditory vibrations (noise) emanating from the heart or blood vessels - are abnormal heart noises, either abnormalities of S1 and S2 heart sounds or additional abnormal noises - They are generated by turbulent blood flow through: - > Altered valves. - > Abnormal openings between arteries and between heart chambers. - > External events like fibrinous pericarditis in bovines - they are graded by their intensity

Answer 220

- left 5th intercostal space, around costal-chondral junction - In the standing animal, usually located in the area opposite to the point of the elbow - S1 is the loudes

Answer 221

- left 4th intercostal space dorsal to MV, usually the level of the point of the shoulder. - S2 heard better

Answer 222

- left 3rd intercostal space at the sternal border, usually at the axilla

Answer 223

- right 3rd and 4th intercostal space, around costal-chondral junction

Answer 224

1. 1/6 Nearly imperceptible, may be heard with very careful auscultation in a quiet environment - always focal. 2. 2/6 Heard readily but very soft - always focal. 3. 3/6 Heard readily, moderate intensity - usually regional (can be heard in several auscultatory regions of the heart). 4. 4/6 Heard readily, loud, and usually radiates widely (can be heard in most or all auscultatory regions of the heart), but without a palpable thrill. 5. 5/6 Heard readily, loud, and associated with a precordial thrill, but the murmur is not heard with the stethoscope lifted off the surface of the thorax. 6. 6/6 Heard readily, loud, associated with a precordial thrill, and the murmur remains audible with the stethoscope lifted 1 cm off the surface of the thorax

Answer 225

- is the term for an acquired or congenitally undersized valve or blood vessel - Blood pushed through this narrowed diameter generates the murmur. - The murmurs related to stenosis (when the heart valves open), occur at different times of the cardiac cycle: - > Systole: in semilunar valves. - > Diastole: in atrioventricular valves

Answer 226

- is the term for a leakage of a valve during its closure - Blood squeezing through this opening between the leaflets in the reverse, or wrong direction generates the murmur - The murmurs related to insufficiency (when the heart valves close), occur at different times of the cardiac cycle: - > Systole: in atrioventricular valves. - > Diastole: in semilunar valves

Answer 227

- the mitral valve does not open as wide as it should, and blood flow from the left atrium to the left ventricle is partially restricted

Answer 228

- the mitral valve leaks when the left ventricle contracts and some blood flows backward into the left atrium

Answer 229

- Ductus arteriosus. - Foramen ovale. - Ductus venosus - > not related to heart sounds or murmurs!!!. - High resistance through collapsed lung. - > Low partial pressure of O2 > hypoxia mediated vasoconstriction. - Low resistance through placenta. - > Pressure gradient goes from the right to the left

Answer 230

- "machinery murmurs" - timing is systolic and diastolic murmur - Causes: - > Combination of stenosis and insufficiency. - > Example: PATENT (remain open) DUCTUS ARTERIOSUS (PDA).

Answer 231

- is one of the three most common congenital heart defects identified in dogs. - The ductus arteriosus is a muscular blood vessel - > Prostaglandins relax the ductus during fetal development. - At birth, lung expansion occurs and oxygen tension in the systemic vasculature increases. - > The lung expansion and the vasodilatation of pulmonary blood vessels reduce the pulmonary resistance. - However, the ductus arteriosus contracts under a higher tension of oxygen and the smooth muscle then undergoes degeneration. - PDA is most commonly hereditary in the dog and it is characterized by ductal smooth muscle hypoplasia.

Answer 232

- is a disturbance in the rate, regularity, or site of cardiac electrical impulse formation. - Consequently, any heart rhythm that does not originate from the sinus node at a normal rate and at a regular interval is classified as an arrhythmia

Answer 233

1. Sinus rhythm - normal heart rate, a regular rhythm a P wave for every QRS complex. - A QRS complex for every P wave 2. Sinus arrhythmia - normal in the dog not in the cat

Answer 234

- increased Parasympathetic - Electrolytes disturbance causing hyperkalemia - Endocrine abnormalities causing hypothyroidism. - Hypothermia. - Specific diseases such as sick sinus syndrome, heart failure (damage of ion channels structure or GAP junctions)

Answer 235

- increased Sympathetic (examination room or pain) - Electrolytes disturbance causing hypokalemia - Fever. - Endocrine abnormalities causing hyperthyroidism. - Heart failure causing mechanical stretch - Hypovolemia. - Drugs such as catecholamines, atropine, glycopyrrolate

Answer 236

1. More negative prepotential (diastolic potential) - > open K+ channels to cause hypokalemia 2. Reduction of depolarization slope - > block Na+ or Ca++ channels 3. More positive threshold potential - > shift voltage sensitivity causing hyperkalemia

Answer 237

- Less negative resting membrane potential - > this potential can be stable or spontaneously depolarize - Premature depolarizations and tachyarrhythmias - Initiation of a depolarization wave (vector) from an abnormal or ectopic site

Answer 238

- It does not initiate an action potential - The action potential is triggered by a preceding normal action potential - > Early afterdepolarization. - > Delayed afterdepolarization

Answer 239

- delayed repolarization (phase 2-3) causes abnormal depolarizations during phase 2 or 3 due to reactivation of L-type Ca++ channels - Slow heart rates

Answer 240

- abnormal depolarization during phase 4 due to activation of Na+ channels - Delayed afterdepolarizations are believed to cause ventricular tachyarrhythmia - Calcium overload

Answer 241

1. aVR - augmented voltage in the right forelimb 2. aVL - augmented voltage in the left forelimb 3. aVF - augmented voltage in the left hindlimb

Answer 242

- tetanospasmin - impairs the exocytosis of inhibitory neurotransmitters in the spinal cord - spastic paralysis

Answer 243

- impairs the exocytosis of acetylcholine in the end plate synapsis - > motor axon innervation of the skeletal muscle - flaccid paralysis

Answer 244

- is a condition resulting from a deficiency of acetylcholine receptors in the post synaptic membrane resulting in a syndrome of muscle weakness - > both congenital and acquired forms of this condition occur in dogs, cats and humans - muscle weakness - tensilon test (edrophonium test) - > anticholinesterase - Megaesophagus - > the esophagus contains skeletal muscle in canines - -> therefore, the esophagus motility will be impaired and the size of the esophagus will be larger

Midterm Flashcards

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