Biology 4

Question 1

Nervous system

1. Draw the organisation of the nervous system

_{(and what things connect to)}

Answer 1

Somatic motor neurons excite only skeletal muscle and are responsible for most of our voluntary movements.

The enteric neurons connect to neurons in the wall of the intestinal tract that control many processes there.

The sympathetic and parasympathetic divisions are important for controlling many processes for body homeostasis

The somatic nervous system and autonomic nervous system also differ in their anatomy. In the somatic nervous system, neurons with cell bodies in the central nervous system send axons to the skeletal muscle they innervate. In the autonomic nervous system, a neuron with a cell body in the central nervous system synapses with a second neuron whose cell body is in a ganglion, or cluster of neuronal cell bodies in the periphery. The second neuron sends an axon to the target organ

Question 2

Balance

1. What are the portions of the inner ear that sense movement of the head called?

Answer 2

The portions of the inner ear that sense movement of the head are called the vestibular system.

The semicircular canals detect rotation of the head while the otolith organs detect linear movement of the head

Question 3

What is the electrical event on the ECG that precedes ventricular diastole?

Answer 3

T wave

Question 4

Channelopathies are diseases related to mutations in ion conducting channels in skeletal muscle.

A mutation in the acetylcholine receptor (AChR) leads to prolonged AChR channel activation in response to a single nerve stimulus.

This will lengthen the time interval for:

A. depolarization of the muscle plasma membrane.

B. the refractory period.

C. the action potential.

D. A, B, and C

Answer 4

D. A, B, and C

Question 5

Neurons

1. How are neurotransmitters released from the pre-synaptic neuron?

Answer 5

Most synapses in the mammalian nervous system transmit between the presynaptic and postsynaptic neurons using chemicals called neurotransmitters.

As the action potential from the presynaptic neuron travels to the end of the axon, calcium is released from voltage-gated calcium channels and causes vesicles full of neurotransmitters to fuse with the plasma membrane and dump their contents into the space between the two neurons called the synaptic cleft.

The neurotransmitters diffuse across the synaptic cleft and either directly or indirectly activate ion channels on the postsynaptic neuron to cause a graded potential.

In an excitatory synapse, ion channels are opened that let positive ions into the cell causing a graded potential that depolarizes the membrane and may or may not be sufficient to reach threshold (excitatory postsynaptic potential).

In an inhibitory synapse, chloride enters the cell or potassium leaves the cell causing a graded potential that hyperpolarizes the membrane and moves the membrane potential farther from threshold (inhibitory postsynaptic potential).

Question 6

The response of the otoliths of the utricle during deceleration is similar to leaning the head in which direction?

forward
backward
to the right
to the left

Answer 6

forward

Question 7

In an electrocardiogram (ECG) , the atrio-ventricular (AV) conduction time is reflected in the:

P-wave duration

T-wave duration

QT interval

PR interval

Answer 7

PR interval

Question 8

11. Each of the following conditions would increase the heart rate EXCEPT:

D. increased permeability of the myocardial membrane to sodium ion

B. increased parasympathetic stimulation of nodal fibers

C. increased levels of epinephrine in the interstitial fluid surrounding the myocardium

A. increased sympathetic stimulation of nodal fibers

Answer 8

B. increased parasympathetic stimulation of nodal fibers
Well done!

Question 9

Neuron

1. Terms for changes in membrane potential - draw diagram

Answer 9

Question 10

Mendelian inheritance is inheritance of biological features that follows the laws proposed by Gregor Johann Mendel in 1865

State the three laws (and explain them)

Draw a 2x2 Punnett square

Answer 10

Law of Segregation - B & b are independently contributed by parents. we have pairs _{as shown in diagram}

Law of Independent Assortment - selection of a particular gene in the gene pair for one trait to be passed to the offspring has nothing to do with the selection of the gene for any other trait.

Law of Dominance - Some alleles are dominant while others are recessive; an organism with at least one dominant allele will display the effect of the dominant allele.

_{A gamete is a cell that fuses with another cell during fertilization (conception) in organisms that sexually reproduce}

B is dominant gene, b is recessive

Mendelian ratio is 3:1

Question 11

If Jim has a cardiac output of 3 L per min at a resting heart rate of 30 bpm.

If his heart rate increases to 90 bpm but his cardiac output remains the same what happens to his stroke volume?

A. His stroke volume increases by a factor of 3

B. His stroke volume decreases to 33 ml

C. His stroke volume remains unchanged

Answer 11

B. His stroke volume decreases to 33 ml

Question 12

Balance

1. Draw the vestibular system of the inner ear

Answer 12

Question 13

Draw a schematic of the heart showing flow, pumps and valves

Answer 13

Four valves are embedded within the cardiac skeleton between the atria and ventricles.

These valves respond passively to pressure gradients. The pulmonic and aortic valves open when the ventricles contract and close with relaxation. The pulmonic and aortic valves prevent back flow from the arteries into the relaxing ventricles.

The AV valves (mitral and tricuspid) close once the ventricles fill. These two valves are closed during contraction of the ventricles and ejection of blood and therefore experience high pressures. To prevent the mitral and tricuspid valves from prolapse (being pushed into the atria) they are tethered to the ventricle wall via tendon like cords and the papillary muscles.

The pulmonic and aortic valves do not have tendons to resist prolapse, instead they are semilunar valves (cup like in shape) which fill with blood when closed. These two valves are closed during relaxation and passive filling of the ventricles

Question 14

Nervous

_{Action potential ->}

_{motor end plate ->}

_{voltage gated calcium channels ->}

_{acetylcholine ->}

1. What does acetylcholine bind to at the motor end plate?
2. and what happens when they do?

Answer 14

_{The portion of the skeletal muscle fiber plasma membrane that synapses with the motor neuron axon is called the motor end plate.}

_{Once an action potential arrives at the axon terminal, the depolarization of the membrane opens voltage-gated calcium channels (Figure 36).}

_{An increase in intracellular calcium at the terminal causes release of acetylcholine vesicles into the neuromuscular junction.}

1. The acetylcholine binds nicotinic channels at the motor end plate which causes them to open and allow sodium to enter (Figure 36).

The sodium entry triggers voltage-gated sodium channels near the motor end plate, initiating an action potential which is propagated in all directions along the plasma membrane of the muscle fiber

Question 15

Muscle

1. In the aerobic metabolism pathway for ATP - how long do the stores last?
2. What activity?

Answer 15

Skeletal Muscle Metabolism

Muscle fibers depend on ATP to produce force.

There are three pathways a muscle fiber uses to make ATP.

1. Creatine phosphate converts ADP to ATP in a single, fast reaction. As a result, 4 moles of ATP are produced per minute from creatine phosphate. However, the stores of creatine phosphate are limited so they are used up in the first 10 seconds of intense exercise. Creatine phosphate is the primary source of ATP during a short, high intensity activity such as the 100 meter dash.
2. Anaerobic metabolism burns glucose as well as the large stores of muscle glycogen (a glucose polymer) to produce lactic acid and ATP in the absence of oxygen. Since only glycolysis is used, 2.5 moles of ATP can be produced per minute. Anaerobic metabolism is used during the first 1.5 minutes of high intensity activity and is the primary source of ATP for the 400 meter dash.
3. Aerobic metabolism uses glycogen, blood glucose, or fatty acids to produce ATP, CO2, and water in the presence of oxygen. Only 1 mole of ATP is made per minute but the available fuel sources are limited only in extreme circumstances. Aerobic metabolism is the primary source of ATP during endurance activities such as a marathon.

Question 16

6. As blood vessel length increases:

A. resistance increases

B. flow decreases

C. friction decreases

D. A and B

E. A, B and C

Answer 16

D. A and B
Well done!

Question 17

Cell membrane transport

How do hydrophillic and hydrophobic molecules move across the cell membrane?

Answer 17

Non-polar molecules (hydrophobic) move across the cell membrane by simple diffusion

Polar molecules (hydrophillic, charged) cannot move across the cell membrane by simple diffusion.

Facilitated diffusion - They use a transporter protein embedded in the cell membrane that is open to either the ECF or the ICF. Solute enters the opening, the transporter protein changes configuration and allows the solute to the other side.

Question 18

Efferent peripheral nervous system

1. What is the neurotransmitter at the first efferent junction from the central nervous system?
2. What is the corresponding neuroreceptor?

Answer 18

Question 19

Nervous system

1. Draw and name the parts of a neuron

Answer 19

Question 20

Action potentials can be generated in smooth muscle cells by activating which of the following?

A. voltage gated Na+ channels

B. ligand gated Ca++ channels

C. mechano gated Ca++ channels

D. B and C

E. A, B and C

Answer 20

D. B and C

B. ligand gated Ca++ channels

C. mechano gated Ca++ channels

Question 21

Nervous

_{Action potential ->}

_{motor end plate ->}

_{voltage gated calcium channels ->}

1. What happens _{after an action potential has reached an axon terminal} and the voltage gated calcium channels have opened?

Answer 21

_{The portion of the skeletal muscle fiber plasma membrane that synapses with the motor neuron axon is called the motor end plate.}

_{Once an action potential arrives at the axon terminal, the depolarization of the membrane opens voltage-gated calcium channels (Figure 36).}

1. An increase in intracellular calcium at the terminal causes release of acetylcholine vesicles into the neuromuscular junction.

The acetylcholine binds nicotinic channels at the motor end plate which causes them to open and allow sodium to enter (Figure 36).

The sodium entry triggers voltage-gated sodium channels near the motor end plate, initiating an action potential which is propagated in all directions along the plasma membrane of the muscle fiber

Question 22

1. What is the stoichiometric formula for carbohydrates?

Answer 22

Carbohydrates can be represented by the stoichiometric formula (CH₂O)n, where n is the number of carbons in the molecule.

Therefore, the ratio of carbon to hydrogen to oxygen is 1:2:1 in carbohydrate molecules. The origin of the term “carbohydrate” is based on its components: carbon (“carbo”) and water (“hydrate”). Carbohydrates are classified into three subtypes: monosaccharides, disaccharides, and polysaccharides.

Question 23

Neurons

1. What is an exitatory synapse?
2. How does it work?

Answer 23

Most synapses in the mammalian nervous system transmit between the presynaptic and postsynaptic neurons using chemicals called neurotransmitters.

As the action potential from the presynaptic neuron travels to the end of the axon, calcium is released from voltage-gated calcium channels and causes vesicles full of neurotransmitters to fuse with the plasma membrane and dump their contents into the space between the two neurons called the synaptic cleft.

The neurotransmitters diffuse across the synaptic cleft and either directly or indirectly activate ion channels on the postsynaptic neuron to cause a graded potential.

1. An excitatory synapse is a synapse in which an action potential in a presynaptic neuron increases the probability of an action potential occurring in a postsynaptic cell.

2. In an excitatory synapse, ion channels are opened that let positive ions into the cell causing a graded potential that depolarizes the membrane and may or may not be sufficient to reach threshold (excitatory postsynaptic potential).

In an inhibitory synapse, chloride enters the cell or potassium leaves the cell causing a graded potential that hyperpolarizes the membrane and moves the membrane potential farther from threshold (inhibitory postsynaptic potential).

Question 24

Balance

1. How do the semicircular canals in the vestibular system analzye rotation and head position?

Answer 24

Semicircular canals

There are three semicircular canals in the inner ear that allow detection of head rotation along three perpendicular axes – nodding the head, shaking the head, and tipping the ear towards the shoulder (Figure 35).

Each canal contains hair cells that move with the head as it rotates around a certain axis.

Because the fluid remains stationary, it bends the steriocilia of the hair cells which causes release of neurotransmitter similar to hair cells of the auditory system.

Question 25

mutation

Answer 25

a random change in a gene

Question 26

What is the electrical event on the ECG that precedes contraction of the atria?

Answer 26

P wave

Question 27

Two types of lower motor neurons

1. Which specialized type of skeletal muscle fibre resides in the muscle spindle in the interior of the muscle?
2. What type of motor neuron innervates this muscle fibre?

Answer 27

Two types of lower motor neurons

_{The portion of a skeletal muscle that controls <strong>posture </strong>and <strong>movement</strong>, the <strong>extrafusal </strong>muscle fibers, are innervated by <strong>alpha </strong>motor neurons.}

A specialized type of skeletal muscle fiber, the intrafusal muscle cell, resides in the muscle spindle in the interior of the muscle (Figure 38). The intrafusal muscle fibers are innervated by gamma motor neurons.

_{During muscle contraction, alpha and gamma motor neurons are coactivated.}

_{Stretching of the intrafusal fibers in the muscle spindle is sensed by stretch receptors and sent via afferent sensory neurons to the spinal cord. This allows for monitoring of the length of the muscle which helps control muscle tone.}

Question 28

Contraction of smooth muscle relies on ___?____ for modulating actin-myosin interaction (cross bridge formation).

C. Na+ dependent myosin phosphorylation

A. Na+ dependent actin phosphorylation

B. Ca++ dependent actin phosphorylation

D. Ca++ dependent myosin phosphorylation

Answer 28

D. Ca++ dependent myosin phosphorylation

In smooth muscle, coupling between the membrane action potentials and contraction is mediated by calcium ions (Ca++).

Calcium regulates the thick filament (myosin) to enable cross bridge formation and contraction.

Question 29

At the end of a maximal inspiration with the glottis open:

A. alveolar pressure will be greater than 0.

B. intrapleural pressure will be greater than atmospheric pressure.

C. alveolar pressure will be equal to atmospheric pressure.

D. intrapleural pressure will be equal to atmospheric pressure.

E. intrapleural pressure will be greater than alveolar pressure

Answer 29

C. alveolar pressure will be equal to atmospheric pressure.

Question 30

Draw cardiac muscle cell(s )

Answer 30

cardiac muscle cell

Question 31

Cell transporters

What types of cell transporters are there?

_{(in terms of how many solutes they can transport and in what directions)}

Answer 31

1. Single transporter - one type of solute
2. Symporter (a co-transporter) - several solutes together. Both must be present and both move in the same direction
3. Antiporter ( a co-transporter) - several solutes together. Both must be present and move in opposite directions.

Question 32

Hearing

1. What happens in the organ of corti in response to sound?

_{(physical and chemical description)}

Answer 32

Organ of Corti

Within the cochlear duct, sitting on the basilar membrane is the organ of Corti, which contains the hair cells that serve as the receptor cells for sound.

Stereocilia of the hair cells are embedded in a tectorial membrane.

As the basilar membrane bounces up and down, the stereocilia bend (Figure 34). Bending the stereocilia on the hair cells opens stretch-sensitive K+ channels and K+ enters the cells due to the composition of the surrounding fluid.

K+ entry depolarizes the hair cell and neurotransmitter is released.

Bending in the other direction hyperpolarizes the cell and inhibits neurotransmitter release.

After a hair cell activates the afferent neuron, axons from these neurons join to form the cochlear nerve.

The region of the basilar membrane along the length of the cochlea that vibrates the most correlates with the frequency of the sound.

As a result, the sensation of pitch is determined by which portion of the basilar membrane is activated. The louder the sound, the more vibration and the greater frequency of action potentials produced in the afferent neurons.

Question 33

2. Valves are found:

A. in the heart

B. in the veins

C. in the arteries

D. A and B

E. A, B and C

Answer 33

D. A and B
Well done!

Question 34

Neurons

1. How does lateral inhibition of sensory neurons work?

_{(Text + diagram of pencil pushing skin)}

2. Why is it used?

Answer 34

_{One example of neurons integrating information is during lateral inhibition of sensory neurons.}

In order to discern the exact point of contact of a stimulus such as a pencil, neighboring neurons must be inhibited.

For instance in Figure 27, the pencil is depressing the skin so that three sensory neurons are firing.

However, the neuron in the middle, neuron 2, is firing more frequently because the pencil is in the middle of its receptive field.

Branches from the axons of all three neurons converge on neighboring neurons. However, since neuron 2 is firing action potentials most frequently, its firing is affected the least by the inhibition.

Lateral inhibition leads to reduction of the firing of neurons 1 and 3 and the sensation that the pencil is depressing only the field of neuron 2 (Figure 27).

This allows for more precise determination of the stimulus site and type.

Question 35

Hormones

1. What are typical concentrations of hormones in the blood stream?

Answer 35

Hormones are secreted into the blood stream and circulate throughout the body at very low concentrations (pMolar to nMolar).

Therefore, their rate of production, delivery, and turnover are important control sites

Question 36

Eye

1. Differentiate between rods and cones
2. Describe the role of each in vision

Answer 36

Rods

Photoreceptor rod cells express rhodopsin photopigment protein and are very sensitive to light. As a result, they are used in night vision.

Many rod photoreceptor cells bind a single bipolar cell. This convergence of signals translates into low resolution vision during conditions of low illumination

Cones

Photoreceptor cone cells express one of three different photopigment proteins called opsins. Cones are less sensitive to light and so are used in conditions of high levels of illumination.

Bipolar cells bind only one cone cell so there is high resolution vision with cones. _{The three different opsins that are expressed by the three types of cones bind retinal in unique ways which leads to absorption of light at different wavelengths. The three opsins are sensitive to red, blue or green wavelengths of light. For instance, red light from a red object primarily hyperpolarizes cones expressing red-sensitive opsin. This activates red bipolar cells and ganglion cells. Colors other than red, blue, or green are perceived when combinations of different cones are stimulated. For instance, we perceive yellow when the red and green cones are both stimulated}

Question 37

20. Stretching a myocardial cell:

A. decreases the force of a contraction

B. allows more K+ to enter

C. increases the force of contraction

D. A and B

E. B and C

Answer 37

C. increases the force of contraction
Well done!

Question 38

Predict how a mutation in the Sacroplasmic Reticulum Ca-release-Ca channel (ryanodine channel) affects skeletal muscle activity if the mutation caused a prolonged increase in free cytoplasmic Ca++.

A. results in sustained contractions.

B. results in shortened contractions

C. results in faster relaxation.

D. has no effect on the duration of either contraction or relaxation.

Answer 38

A. results in sustained contractions

Question 39

In smooth muscle does Ca++ regulate the thick filament or the thin filament?

Answer 39

In smooth muscle, coupling between the membrane action potentials and contraction is mediated by calcium ions (Ca++).

Calcium regulates the thick filament (myosin) to enable cross bridge formation and contraction.

Question 40

AV valves of the heart open and close because of:

nervous impulses to papillary muscles.

passive recoil of valves.

changes in pressure in adjacent chambers.

mechanical stretching of the fibers attached to the valves as the myocardium contracts and relaxes.

Answer 40

changes in pressure in adjacent chambers

Question 41

1. What is the difference between heat capacity and specific heat?
2. What are their units?

Answer 41

padlet

Question 42

John began lifting weights at the gym to improve his total lack of fitness. After strength training for 9 months, his biceps were bigger and he could lift 100 lbs. more than when he started. His training:

increased the number of muscle fibers in his biceps.
increased the number of myofibrils in his biceps.
increased the number of motor units in his biceps

Answer 42

increased the number of myofibrils in his biceps.

Question 43

At the first half mile of a marathon run you would expect which of the following?

A PaCO2 to decrease but no change in PaO2.

B PaCO2 and PaO2 to show little or no change from resting values.

C PaCO2 to increase and PaO2 to decrease.

D PaCO2 and PaO2 to decrease markedly.

Answer 43

B PaCO2 and PaO2 to show little or no change from resting values.

Question 44

Hearing
1. Draw the anatomy of the cochlea

Answer 44

Question 45

A decrease in blood pH will _________ the rate of breathing.

increase

decrease

not change

Answer 45

increase

Question 46

How does spontaneous pacemaker potentials work in some smooth muscle cells?

Draw the graph

Answer 46

Some smooth muscle exhibits spontaneous contractile activityin the absence of either nerve or hormonal stimuli. The plasma membranes of these fibers do not maintain a stable resting membrane potential. Instead the resting membrane potential gradually drifts towards threshold where it triggers an action potential (Figure 49). Following repolarization the membrane again begins to depolarize. This is property is called pacemaker activity. Pacemakers are found within the GI tract.

Question 47

Neuron

1. What is an inhibitory synapse?
2. How does it work?

Answer 47

Most synapses in the mammalian nervous system transmit between the presynaptic and postsynaptic neurons using chemicals called neurotransmitters.

As the action potential from the presynaptic neuron travels to the end of the axon, calcium is released from voltage-gated calcium channels and causes vesicles full of neurotransmitters to fuse with the plasma membrane and dump their contents into the space between the two neurons called the synaptic cleft.

The neurotransmitters diffuse across the synaptic cleft and either directly or indirectly activate ion channels on the postsynaptic neuron to cause a graded potential.

An excitatory synapse is a synapse in which an action potential in a presynaptic neuron increases the probability of an action potential occurring in a postsynaptic cell. In an excitatory synapse, ion channels are opened that let positive ions into the cell causing a graded potential that depolarizes the membrane and may or may not be sufficient to reach threshold (excitatory postsynaptic potential).

1. Inhibitory synapse -A synapse in which an action potential in the presynaptic cell reduces the probability of an action potential occurring in the postsynaptic cell.

2. In an inhibitory synapse, chloride enters the cell or potassium leaves the cell causing a graded potential that hyperpolarizes the membrane and moves the membrane potential farther from threshold (inhibitory postsynaptic potential).

Question 48

How many of the cardiac muscle cells are conducting (the intrinsic pacemakers)?

Answer 48

CONDUCTING cardiac muscle cells are ~ 1% of the cardiac muscle cells.

These are large diameter cells that do not produce tension, instead they are specialized for excitation.

They constitute a network in the heart known as a conduction system.

They are connected to the contractile cells by gap junctions.

The conducting fibers are filled mostly with glycogen and have few myofilaments. These cells are the intrinsic pacemakers. We will deal with their action potentials in the next lecture.

Question 49

Nervous

1. What does the autonomic nervous system control (4)?

Answer 49

The efferent portion of the peripheral nervous system consists of the somatic nervous system and the autonomic nervous system.

The autonomic nervous system controls the function of glands, smooth muscle, cardiac muscle, and the neurons of the GI tract.

It is composed of two neurons in series that can either excite or inhibit the target organ.

In contrast, the somatic nervous system contains single neurons that excite skeletal muscles.

The movements controlled by the somatic nervous system can be voluntary or involuntary (reflexes)

Question 50

The hormone and its regulated substance do not change independently. By monitoring both the hormone and its regulated substance, one can readily deduce the nature of the dysfunction.

1. What are the three types of pathology - name and describe

Answer 50

The hormone and its regulated substance do not change independently. By monitoring both the hormone and its regulated substance, one can readily deduce the nature of the dysfunction.

When the target endocrine gland itself is misbehaving, then it is referred to as a primary pathology.

If the problem occurs in the proximal regulating gland (pituitary), then it is a secondary pathology,

and those due to the more distal regulator (hypothalamus) are tertiary pathologies.

Question 51

Neurons

1. How is the electrical gradient established across the plasma membrane?

Answer 51

1. The gradient is primarily established by affecting the concentration of three ions in the cell, Na+, Cl- and K+

Question 52

The convergence of rod cells on bipolar cells explains which of the following?

the low resolution of color vision
the low resolution of night vision
the high resolution of color vision
the ability to see color

Answer 52

the low resolution of night vision

Question 53

Draw the physiology of skeletal muscle contraction at the molecular level

Answer 53

image LINK

Question 54

Myasthenia gravis is an autoimmune disease in which antibodies block the acetylcholine receptor at the neuromuscular junction. Why does an acetylcholinesterase inhibitor help these patients?

A. Acetylcholinesterase inhibitor slows the removal of acetylcholine thereby increasing receptor occupancy and end plate potentials.

B. Acetylcholinesterase inhibitor increases uptake of acetylcholine into the synapse thereby “reloading” the synaptic vesicles.

C. Acetylcholinesterase inhibitor increases the removal of antibodies from the synapse.

D. Acetylcholinesterase inhibitor slows the degradation of the acetylcholine receptor at the synapse thereby increasing its activity.

Answer 54

A. Acetylcholinesterase inhibitor slows the removal of acetylcholine thereby increasing receptor occupancy and end plate potentials.

Question 55

Muscle Stretch Reflex.

1. What type of neuron relays the stretch signal from the muscle spindle to its cell body.

Answer 55

Muscle Stretch Reflex.

_{If a muscle spindle within a muscle is quickly stretched, the muscle stretch reflex causes contraction of the muscle as well as nearby muscles. This is what occurs when the patellar tendon is struck during a physical exam (Figure 39).}

The afferent sensory neuron relays the stretch signal from the muscle spindle to its cell body in the dorsal root of the spinal cord. The sensory neuron synapses with the motor neuron in the spinal cord that controls that muscle.

I_{n addition, the sensory neuron activates an inhibitory neuron which inhibits the motor neuron (reducing its likelihood of firing an action potential) leading to the muscle on the opposite side of the limb, causing it to relax (Figure 39).}

_{The muscle spindle reflex is important in allowing maintenance of the length of a certain muscle.}

Question 56

4. Does MAP (increase, decrease or remain unchanged) during anaerobic exercise such as weight lifting?

A. Increases

B. Decreases

C. Remains unchanged

Answer 56

Answer 4: A. Increases

Question 57

The Circulatory System

4. If MAP increases in an eighty year old male, what happens to afterload?

A. Afterload is increased

B. After load is decreased

C. After load is unchanged?

Answer 57

Answer 4: A. Afterload is increased

Afterload is the pressure against which the heart must work to eject blood during systole (systolic pressure). The lower the afterload, the more blood the heart will eject with each contraction.

Like contractility, changes in afterload will raise or lower the Starling curve relating stroke volume index to LAP.

The effect of afterload on stroke colume is due to the fact that the maximum pressure that the heart can develop is smaller at lower ventricular volumes.

Therefore, if the systolic pressure is lower, the heart will be able to contract to a smaller volume at the end of systole. This will result in an improved stroke volume.

Conversely, if the systolic pressure is higher, the heart will be unable to contract to as small a vollume at the end of systole and the stroke volume index will be decreased.

Question 58

12. Ventricular contraction begins just after ___ begins.

B. QRS complex

A. P wave

E. ST segment

C. T Wave

D. PR segment

Answer 58

B. QRS complex
Well done!

Question 59

On which myofilament is troponin located?

A. thin filament (actin)

B. thick filament (myosin)

Answer 59

A. thin filament (actin)

Question 60

What is the electrical event on the ECG that precedes contraction of the atria?

Answer 60

P wave

Question 61

Muscle

1. What is the mechanical response of a single muscle fiber to a single action potential called?
2. What happens with repeated stimulation of a skeletal muscle?

Answer 61

Muscle Tension

The mechanical response of a single muscle fiber to a single action potential is called a twitch.

Following an action potential there is brief period before tension, the force exerted on an object, develops. This is known as the latent period. The action potential of a single impulse lasts only 2 milliseconds. The associated contraction time (twitch) lasts for 10-100 milliseconds.

This means that repeated stimulation of a skeletal muscle will cause summation of the contractions until there is no relaxation and fused tetanus is reached (Figure 45). Not all muscle fibers have the same contraction times. Some fast fibers contract in 10 milliseconds; slower fibers take 100 milliseconds or longer. The duration depends on the SR-ATPase activity.

Question 62

Fluid compartments

1. How does a physiologist view the body?
2. Name parts and proportions

Answer 62

1. As two fluid compartments

separated by a plasma membrane

2. Intercellular fluid compartment (2/3)

Extracellular fluid compartment (1/3)

_{{ECF further broken into Intervascular fluid and interstitial}}

Question 63

In smooth muscle cells, a pacemaker potential differs from a graded potential because pacemaker potentials:

activate with the efflux of Na+

vary in size

always reach threshold

activate with the influx (entry) of Cl-

Answer 63

always reach threshold

Question 64

Draw smooth muscle tissue structure with contraction

Answer 64

image LINK

Question 65

Senses

1. What are the receptors important for somatosensation?

Answer 65

The skin, muscles, and joints have receptors that can

sense touch, pressure, temperature, pain, or the position of the body.

The information gathered by these receptors leads to sensations referred to as somatosensations.

_{Each receptor type responds primarily to only one type of stimulus. Mechanoreceptors are nerve endings that are encapsulated by connective tissue that sense touch and pressure. There are different types of encapsulated nerve endings that have different morphologies which allow them to respond to a specific kind of touch. Stretching of the connective tissue fibers of the encapsulated endings activates ion channels which can produce action potentials that signal to the central nervous system.}

_{Posture and movement of body parts are sensed by muscle stretch mechanoreceptors, as well as mechanoreceptors present in skin, joints, tendons, and ligaments. Together they sense the amount of muscle stretch as well as the rate of muscle stretch. Vision and balance also play a role in the perception of where the body is in space, or proprioception.}

_{Temperature is sensed in the skin using different types of thermoreceptors. Free nerve endings, which are processes of neurons, sense temperature using ion channels that are activated only at certain temperatures. A single sensory neuron only expresses a single kind of thermoreceptor. Thermoreceptors can also detect certain chemicals. For instance, cold-sensing thermoreceptors respond to menthol, while heat-sensing thermoreceptors respond to capsaicin (from chili peppers) and ethanol.}

_{Pain is sensed by free nerve endings expressing nociceptors, which are receptors that sense extreme mechanical deformation, high temperatures, as well as chemicals released by damaged cells or immune cells.}

Question 66

13. Ventricular repolarization occurs during:

D. PR segment

A. P wave

B. QRS complex

C. T Wave

E. ST segment

Answer 66

C. T Wave
Well done!

Question 67

Cell membrane channels

1. Explain and characterise

2 Explain gating and the three types of gating mechanism

Answer 67

1. When a channel is open there is a clear hole

when closed its gone

2. Ligand - specific chemical to open

Voltage - specific gradient across the cell membrane to open

Mechanical - specific tension to open

Question 68

Would an increase in the number of open K+ channels near the initial segment of a neuron affect the size of the stimulus required to initiate an action potential?

yes, the stimulus required would be greater
yes, the stimulus required would be smaller
no

Answer 68

yes, the stimulus required would be greater