Biology

Question 1

Ventricular repolarization in the human heart:

A. begins in the atria and travels in the same direction as the depolarization wave.

B. results from phase 2 of the fast action potential.

C. is represented by the T wave on the electrocardiogram (ECG).

D. is represented by the QRS complex on the electrocardiogram (ECG)

Answer 1

C. is represented by the T wave on the electrocardiogram (ECG).

Question 2

Nervous

1. The portion of the skeletal muscle fiber plasma membrane that synapses with the motor neuron axon is called the ..?..?..?

Answer 2

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.

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 3

Heart

1. What is preload?
2. and how is it increased?

Answer 3

PRELOAD is the degree of stretch of the myocardium before contraction.

An increase in venous return (filling) will increase preload and thus increase the force of contraction.

Consider the P-V loop depicted in Figure 63. An increase in preload (filling) will move the EDV to the right along the X axis and increase the pressure generated (Y axis). The heart (depicted as ABCD) when filled to an EDV of 140 ml, generates a systolic pressure of 180 mmHg. The “red curved” line in Figure 63 depicts the force generated for each increase in EDV for this particular heart.

Question 4

Cell types in bone

1. What are the four cell types in bone?
2. What is their function?

Answer 4

Osteocyte - maintains bone tissue

Osteoblasts - forms bone matrix

Osteogenic cells - stem cell

Osteoclasts - resorbs bone _{(remove (cells, or a tissue or structure) by gradual breakdown into its component materials and dispersal in the circulation)}

image LINK

_{Osteogenic cells are the only bone cells that divide.<br></br>Osteogenic cells differentiate and develop into osteoblasts which, in turn, are responsible for forming new bone.<br></br>Osteoblasts synthesize and secrete a collagen matrix and calcium salts.<br></br>When the area surrounding an osteoblast calcifies, the osteoblast becomes trapped and transforms into an osteocyte, the most common and mature type of bone cell.<br></br>Osteoclasts, the cells that break down and reabsorb bone, stem from monocytes and macrophages rather than osteogenic cells..<br></br>There is a continual balance between osteoblasts generating new bone and osteoclasts breaking down bone.}

Question 5

Tonicity and cell volume

1. Define tonicity
2. Compare tonicity with osmolarity
3. Put a red blood cell in 300 mOsM solution _{(the body normal state)}

what is the solution called?

what happens to the cell?

4. Now a 200 mOsM solution
5. Now a 400 mOsM solution

Answer 5

1. # non-penetrating molecules/L
2. Osmolarity considers ALL particles,

whether they can cross the cell membrane or not

3. Isotonic, nothing
4. hypotonic, water diffuses into the cell causing it to expand
5. hypertonic, water diffuses out of the cell causing it to shrink

Question 6

Neuron

1. What is the magnitude of the charge difference between the inside and outside of the cell is referred to as?
2. What determines the charge difference between the inside and outside of a cell?

Answer 6

Equilibrium potentials

Due to the concentration gradient of ions across the plasma membrane of cells, the intracellular fluid has a small excess of negative charge compared to the extracellular fluid.

The separation of charge has the potential to do work. As a result, the magnitude of the charge difference between the inside and outside of the cell is referred to as the membrane potential and measured in millivolts.

If there is an excess of negative charges on the inside of the cell, the membrane potential is negative. If the excess charge on the inside of the cell is positive, the membrane potential is positive.

The membrane potential of a cell under specific conditions is determined by the concentration of ions inside and outside of the cell and by the permeability of the membrane for those ions

Question 7

A human cell has how many chromosomes?

Answer 7

24 pairs

Question 8

Spinal cord structure

1. Draw the Spinal cord structure

(from pin to muscle)

Answer 8

Question 9

1. Where does blood enter and leave the heart?
2. What implications are there for contraction?

Answer 9

1. Note that blood enters and leaves the ventricles at the base (A-V junction).
2. That means that the ventricles must contract from the bottom (apex) upward to expel the blood from the base

Question 10

Two types of lower motor neurons

1. Which muscle fibers of a skeletal muscle control posture and movement?
2. What type of motor neuron innervates this muscle fibre?

Answer 10

Two types of lower motor neurons

The portion of a skeletal muscle that controls posture and movement, the extrafusal muscle fibers, are innervated by alpha motor neurons.

_{A specialized type of skeletal muscle fiber, the <strong>intrafusal </strong>muscle cell, resides in the muscle <strong>spindle </strong>in the interior of the muscle (Figure 38). The intrafusal muscle fibers are innervated by <strong>gamma </strong>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 11

ake is floating on the surface of a lake and breathing through a snorkel. Does he need to increase his tidal volume to keep his alveolar ventilation normal?

Yes.

No

Answer 11

Yes

Question 12

1. Name the three general types of hormones
2. Where they come from
3. Their solubility in blood

Answer 12

There are three general types of hormone molecules: peptides, steroids, and amines. They differ in their relative solubility in plasma.

Peptide hormones consist of three or more amino acids and are soluble in blood.

Steroid hormones are derived from cholesterol and are insoluble in blood.

Amine hormones are derivatives of amino acids and some are soluble in blood

Question 13

Which of the following determines the speed of contraction in smooth muscle?

number of cross bridges formed

kinetics of the myosin ATPase

activation of the voltage gated sodium channel

unmasking of the thin filament

Answer 13

kinetics of the myosin ATPase

MYOSIN ATPase has a slow rate of hydrolysis. It hydrolyzes ATP at about 10% of the rate observed in skeletal muscle. Consequently smooth muscle produces slow, sustained contractions using only 10% of the ATP that skeletal muscle would require for the same work

Question 14

How many genes does it take to make a human bieng.

Answer 14

20 000 – 40 000

Question 15

10. Each of the following factors will increase cardiac output EXCEPT:

B. Increased parasympathetic stimulation

D. Increased heart rate

C. Increased sympathetic stimulation

A. Increased venous return

Answer 15

B. Increased parasympathetic stimulation
Well done!

Question 16

Capillaries are best described as:

E. thin walled vessels which carry blood deficient in oxygen.

C. thin walled vessels which convey blood toward the heart.

A. thin walled vessels which permit exchange of materials between blood and interstitial fluid.

B. thick walled vessels which convey blood away from the heart.

D. thick walled vessels which carry blood rich in oxygen.

Answer 16

A. thin walled vessels which permit exchange of materials between blood and interstitial fluid.
Well done!

Question 17

Muscle

1. In the creatine phosphate ATP pathway - how long do the creatine phosphate stores last?
2. What sort of activity?

Answer 17

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 18

Neurons

1. What effect does the concentration gradient of ions across the plasma membrane of cells have?

Answer 18

Equilibrium potentials

Due to the concentration gradient of ions across the plasma membrane of cells, the intracellular fluid has a small excess of negative charge compared to the extracellular fluid.

The separation of charge has the potential to do work. As a result, the magnitude of the charge difference between the inside and outside of the cell is referred to as the membrane potential and measured in millivolts.

If there is an excess of negative charges on the inside of the cell, the membrane potential is negative. If the excess charge on the inside of the cell is positive, the membrane potential is positive.

The membrane potential of a cell under specific conditions is determined by the concentration of ions inside and outside of the cell and by the permeability of the membrane for those ions

Question 19

What are the differences between

MULTI-UNIT smooth muscle fibers

and

SINGLE UNIT smooth muscle fibers

Answer 19

SINGLE VERSUS MULTI-UNIT FIBERS

Smooth muscle fibers do not have a specific neuro-muscular junction. Instead as the autonomic nerve nears a bundle of smooth muscle, it divides into many branches each containing a series of swellings (called varicosities) filled with vesicles of neurotransmitters.

MULTI-UNIT smooth muscle fibers are innervated independently. The fibers are not connected by gap junctions. Depolarization of one fiber is followed by contraction of that fiber only. These fibers are richly innervated by the autonomic nervous system. Nervous stimuli and hormones cause contraction (or relaxation) of these fibers, not stretch. The smooth muscle of the lung airways, in the walls of large arteries, and attached to the hair of the skin are multi-unit fibers.

SINGLE UNIT smooth muscle fibers are connected by gap junctions. Depolarization of one fiber triggers synchronous depolarization throughout the bundle followed by contraction of the fiber bundle. That is, many fibers act as one sheet. Single unit fibers are found in the walls of small blood vessels, the GI tract, and uterus where stretching of one fiber creates a coordinated contraction

Question 20

Neuron

1. How do action potentials work?

_{(multi-stage diagram)}

Answer 20

At the beginning of an action potential the cell which was at resting membrane potential has a graded potential that causes the membrane to be depolarized

If the depolarization from the graded potential reaches a certain voltage, called the threshold, then enough voltage-gated Na+ channels will be opened to start an action potential (stage 2).

Once enough Na+ channels are open, Na+ starts rushing into the cell due to the net negative charge inside the cell and the excess of Na+ outside the cell. This causes the membrane potential to increase (stage 2) and surpass 0 mV due to the concentration gradient of Na+.

The cell is so permeable to Na+ that the membrane potential quickly comes close to the equilibrium potential for Na+. Right before the membrane potential reaches the equilibrium potential for Na+, the Na+ channels inactivate and the slower opening voltage-gated K+ channels open.

When the K+ channels open, there is an excess of positive charge and K+ inside the cell (a positive membrane potential) so K+ leaves the cell and travels down its concentration and electrical gradients.

This lowers the membrane potential (stage 3) and it approaches the equilibrium potential for K+, which is below resting potential (stage 4).

The K+ channels start to close and the membrane returns to the resting potential (stage 5).

Question 21

Consider the following pulmonary function test data from a patient with pulmonary fibrosis in answering the question below.

Frequency (f) 18 breaths/min

Pulmonary Diffusing Capacity (ml/min per mmHg)

predicted 14.1

observed 8.6 62%

Arterial Blood Gases:

PO2 = 50 mm Hg

PCO2 = 49 mm Hg

1. a likely reason for the lower than normal diffusing capacity is which of the following?

A. increased surface area of the alveolar-capillary membrane

B. increased driving pressure gradient for diffusion of oxygen

C. increased thickness of the alveolar capillary membrane

D. decreased diffusion constant for CO2

Answer 21

C. increased thickness of the alveolar capillary membrane

Question 22

Hormone receptors specificity and biological response

1. What determines the hormone receptors location?
2. Where are peptide hormone receptors located?
3. Where are steroid hormone receptors located?
4. Where are amine hormone receptors located?

Answer 22

1. The lipid solubility of the hormone dictates the cellular location of its receptor. Plasma insoluble hormones bind to intracellular receptors; plasma soluble hormones bind to cell surface receptors
2. Peptide hormones bind to cell surface receptors which activate a second messenger (Figure 14). This results in a rapid (seconds) change in function/metabolism.

_{Second messengers are important because they provide:}

_{Amplification: One hormone molecule can generate thousands of copies of second messenger (e.g., cAMP) and thereby affect many copies of responsive target molecules (effectors) in the cell.}

_{Memory: Once activated the second messenger stays on for several seconds to minutes.}

_{Complex regulation: Multiple pathways can be initiated by binding one hormone to a single receptor type}

3. 4. Thyroid and steroid hormones bind to intracellular receptors to activate transcription. This results in synthesis of new proteins and therefore is a slow response

Question 23

If Jane’s tidal volume is 0.6 L, the anatomic dead space is 0.14 L, and the respiratory rate is 18 breaths/ min, then estimated alveolar ventilation would be closest to:

A. 8.28 Liters/min

B. 10.8 Liters/min

C. 2.80 Liters/min

D. 5.10 Liters/min

Answer 23

A. 8.28 Liters/min

Question 24

SPINAL CORD ANATOMY

1. Excitation of motor neurons causes ???????? to be released at the neuromuscular junction causing ??????? of the muscle.

The muscle ????? when the motor neuron is no longer excited

Answer 24

SPINAL CORD ANATOMY

_{The cell bodies of the neurons that innervate skeletal muscle of the body are found in the ventral horn of the spinal cord (Figure 37, blue).}

_{The neurons that innervate the skeletal muscle of the head are in the brainstem.}

_{In the body, sensory signals come into the spinal cord from the dorsal root ganglia, which contain the cell bodies of sensory neurons (Figure 37, red). These neurons can excite motor neurons in the spinal cord.}

_{Motor neuron axons travel through tissues as nerves and synapse on skeletal muscle cells.}

Excitation of motor neurons causes acetylcholine to be released at the neuromuscular junction causing contraction of the muscle. The muscle relaxes when the motor neuron is no longer excited

Question 25

Which of the following conditions leads to decreased lung compliance?

A Decreased production of surfactant

B Increased fibrosis

C Increased fluid in the interstitial space surrounding the alveoli (edema)

A, B and C

Answer 25

A, B and C

Question 26

Eye

1. How does the eye lens work?

Answer 26

When light hits the cornea, it is bent, or refracted as it passes from air into the tissue. This is the largest source of refraction and focusing by the eye

The light continues through the aqueous humor and is refracted as it travels through the lens, which can adjust to focus on objects a certain distance away.

Ciliary muscles encircle the perimeter of the lens and flatten the lens when the muscles relax or make the lens more round when the muscles contract.

A lens that is more round allows the eye to focus on closer objects.

Question 27

Sketch skeletal muscle structure

Answer 27

image LINK

Question 28

Fast action potential of cardiac contractile cell has four phases (0-4)

1. Describe each phase in terms of gates and ions

Answer 28

Myocardial contractile cells have a resting membrane potential of approximately -85 millivolts (mV). Depolarization occurs when the permeability to sodium increases, and sodium flows into the cell (Phase 0, Figure 57).

As the membrane potential reaches about +20 mV, the voltage gated sodium channels inactivate. The muscle cell begins to repolarize as K+ leaves the cell through open voltage gated K+ channels (Phase 1).

At this membrane potential, voltage gated Ca++ channels open causing the action potential to flatten as the K+ efflux balances the Ca++ influx. The plateau (Phase 2) ends when Ca ++ channels close and K+ efflux exceeds Ca++ influx.

In Phase 3, K+ efflux repolarizes the muscle cell.

The resting membrane potential is maintained by the activity of the Na-K ATPase (Phase 4)

Question 29

Jane was holding a tray of dirty glasses when John added an extra 5 pounds of plates.

To prevent dropping the tray, Jane’s muscles increased their force of contraction through an increase in the:

A. length of the muscle.

B. number of motor units activated and the frequency of their activation.

C. peak intracellular calcium concentration in the muscle.

D. strength of each cross bridge interaction with myosin.

Answer 29

B. number of motor units activated and the frequency of their activation.

Question 30

Smell

1. What happens when an odorant binds to a receptor?

Answer 30

SMELL

Odors in the air are detected by chemoreceptors of olfactory neurons.

The olfactory neuron serves as the receptor cell as well as the afferent neuron.

1. Binding of an odorant receptor leads to activation of signal transduction pathways that open cation channels and lead to graded potentials.

Each odorant binds a combination of odorant receptors that are specific for different parts of the molecule.

It is the combination of activated receptors that leads to our perception of a smell of a particular substance

Question 31

Spinal cord

1. What does a motor unit consist of?

Answer 31

_{The axons of motor neurons are myelinated and have large diameters for fast conduction of action potentials.}

_{As the axon approaches a skeletal muscle fiber (muscle cell) it usually branches to form synapses with anywhere from three to one thousand muscle fibers.}

_{However, each muscle fiber is usually innervated by only a single neuron.}

1. A motor unit consists of a neuron and all of the muscle fibers it innervates.

A single neuron innervates fibers from only one muscle and the innervated muscle fibers are usually spread throughout the muscle

Question 32

Alveoli are less compliant at:

Low lung volume

High lung volume

Functional residual capacity (FRC)

Answer 32

High lung volume

Question 33

Tissue

1. Define tissues
2. Name the main tissue types in the human body

Answer 33

1. Groups of cells with related function
2. Muscle, nervous, connective & epithelium

Question 34

Muscle

1. What does muscle fibre depend on to produce force?

Answer 34

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 35

9. The volume of blood ejected from each ventricle during a contraction is called the:

A. end-diastolic volume

E. cardiac reserve

C. stroke volume

B. end-systolic volume

D. cardiac output

Answer 35

C. stroke volume
Well done!

Question 36

Two types of muscle sensory receptors

1. Golgi tendon organs are encapsulated sensory receptors situated in tendons near the junction with the muscle (Figure 38).

They detect changes in muscle ….??…. instead of changes in muscle length.

Answer 36

Two types of muscle sensory receptors

_{In order for the body to be able to control muscle contraction properly, there must be feedback about the contractile status of individual muscles.}

_{The muscle spindle is an important muscle sensory receptor that provides information about muscle length and the rate of change of muscle length.}

In addition, Golgi tendon organs are encapsulated sensory receptors situated in tendons near the junction with the muscle (Figure 38). They detect changes in muscle tension instead of changes in muscle length.

_{Both types of sensory receptors send information to the spinal cord and the brain that is usually subconscious.}

Question 37

Senses

1. What does an afferent neuron’s specialized ending produce in response to a stimulus?

Answer 37

1. An afferent neuron has a specialized ending that produces graded potentials that can lead to action potentials in response to a stimulus.

Question 38

Withdrawal Reflexes.

_{A withdrawal reflex occurs when a part of the body such as a portion of a limb is subjected to a painful stimulus.}

_{The flexor reflex causes contraction of one muscle and relaxation of the opposing muscle to move that portion of the body away from the insult.}

1. A short time after the flexor reflex initiates, the …?…..?…..?.. initiates on the …?.. side of the body.

Answer 38

Withdrawal Reflexes.

_{A withdrawal reflex occurs when a part of the body such as a portion of a limb is subjected to a painful stimulus.}

_{The flexor reflex causes contraction of one muscle and relaxation of the opposing muscle to move that portion of the body away from the insult.}

A short time after the flexor reflex initiates, the crossed extensor reflex initiates on the opposite side of the body.

This reflex allows for the opposite side of the body to support the body’s weight or to push the body out of the way of the painful stimulus.

Question 39

Neurons

1. Transport proteins important for establishing resting membrane potential - draw diagram

Answer 39

Question 40

Hormone receptors specificity and biological response

1. Why are cell responses specific to a hormone?

Answer 40

1. The receptor contains a recognition site that binds its hormone with high affinity and selectivity. A cell may express thousands to tens of thousands of receptors for a single hormone

Question 41

An increase in tissue PCO2 will cause vasoconstriction in:

A arterioles that perfuse the lung alveoli

B arterioles that perfuse skeletal muscle

C arterioles perfuse lung alveoli and skeletal muscle

D veins only

Answer 41

A arterioles that perfuse the lung alveoli

Question 42

1. Draw membrane potential vs time for pacemaker cells
2. Describe the flow of ions at each stage

Answer 42

Pacemaker cells

have the unique property of being able to generate action potentials spontaneously (i.e. without input from the nervous system). They can generate an action potential because their resting membrane potential (- 60mV) is unstable.

This potential exists because the pacemaker cells have unusual channels that are permeable to both Na + and K+. These channels are called If channels. _{The “f” is derived from the fact that they were originally called “funny” channels because the If channels are Na+ channels with unusual properties}. When the If channels opens, the influx of Na+ exceeds the efflux of K + and the net influx of positive charges slowly depolarizes the cell.

As the membrane potential becomes more positive, the If channels close and the Ca++ channels open transiently, which further depolarize the cell.

When the threshold potential is reached, a burst of Ca++ channels open, more Ca++ rushes in, and a steep phase of depolarization (Phase2) occurs (Figure 56). At the peak of the action potential, K+ channels open, K+ rushes out of the cell and the cell repolarizes

Question 43

Nervous

1. The efferent portion of the peripheral nervous system consists of

(the …………….nervous system and the ……………..nervous system)

Answer 43

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 44

Muscle Stretch Reflex.

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

Answer 44

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.}

_{In 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 45

Nervous

_{Action potential ->}

_{motor end plate ->}

1. What happens when an action potential arrives at the axon terminal?

Answer 45

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

1. 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.}

_{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 46

Facilitated diffusion in cells

1. Define facilitated diffusion
2. Draw the flux vs solute concentration graph for simple and facilitated diffusion
3. Why might the graphs be different

Answer 46

1. Facilitated diffusion – membrane impermeable molecules can either enter or leave cells using transport proteins.

Transport proteins are classified as either transporters or channels.

2. See graph
3. There are only so many transport proteins on the cell surface.

So at some concentration they are all being used.

So increasing concentration does not increase the flow rate across the cell membrane

Question 47

Smell

1. How do smell receptors differ from other receptors?

Answer 47

SMELL

Odors in the air are detected by chemoreceptors of olfactory neurons.

1. The olfactory neuron serves as the receptor cell as well as the afferent neuron.

Binding of an odorant receptor leads to activation of signal transduction pathways that open cation channels and lead to graded potentials.

Each odorant binds a combination of odorant receptors that are specific for different parts of the molecule.

It is the combination of activated receptors that leads to our perception of a smell of a particular substance

Question 48

Fibrosis patients often have a functional residual capacity that is smaller than normal because:

A. The diameter of their airways is greater than normal

B. The compliance of the lung is decreased

C. The compliance of the chest wall is decreased

D. The total lung capacity is greater than normal

E. The elastic recoil of the lungs is decreased

Answer 48

B. The compliance of the lung is decreased

Question 49

The Circulatory System

3. If advanced atherosclerosis, calcified plaques cause the normally muscular arteries to become narrow.

If cardiac output remains unchanged, what happens to MAP?

A. MAP increases

B. MAP decreases

C. MAP remains unchanged

Answer 49

Answer 3: A. MAP increases

Question 50

Some smooth muscle exhibits spontaneous contractile activity in the absence of either nerve or hormonal stimuli.

1. Where in the body for example?

Answer 50

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 51

What sort of muscle fibres are the contractile cardiac muscle cells?

Answer 51

CONTRACTILE cardiac muscle cells are slow oxidative muscle fibers.

These fibers form the walls of the heart, shorten and produce tension. They use glucose and fatty acids as substrates.

Question 52

1. Describe the flow of blood through the heart
2. And the required thickness of the walls of the various parts

Answer 52

The right side of the heart has a thin muscular wall and works at low pressures. Contraction of the right ventricle (RV) pumps blood into the pulmonary circulation (lungs) where oxygen is taken up and carbon dioxide is eliminated.

The left side of the heart has a thicker muscular wall and works at higher pressures. Contraction of the left ventricle (LV) pumps blood into the systemic circulation for delivery to the limbs and to all of the organs.

The right atrium (RA) receives blood returning from the systemic circulation;

the left atrium (LA) receives blood from the lungs (Figure 59).

Total amount of blood circulating is ~5 liters/ minute

Question 53

Nervous

1. Action potential ->

motor end plate ->

voltage gated calcium channels ->

acetylcholine ->

nicotinic channels open ->

sodium enters ->

What happens next?

Answer 53

_{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.}

_{The acetylcholine binds nicotinic channels at the motor end plate which causes them to open and allow sodium<strong> </strong>to enter (Figure 36).}

1. 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 54

Draw a Left Ventricle Pressure Volume loop for a heartbeat - indicate what is happening at each stage

Answer 54

Pressure-volume loop ABCD depicts changes in left ventricle in one beat.

The ventricle fills between A-B.

Interval B-C depicts isovolumic contraction.

Interval C-D depicts ejection.

Interval D-A depicts isovolumic relaxation

Question 55

1. The valves of the heart open and close in response to:

A. active contraction of the papillary muscles

B. pressure differences between the heart chambers

C. shortening of the tendons within the ventricle

D. autonomic nervous stimulation

Answer 55

1. B pressure differences between the heart chambers

Question 56

Describe the phases of ACTION POTENTIAL OF CONTRACTILE CARDIAC CELLS

(0-4)

Answer 56

ACTION POTENTIAL OF CONTRACTILE CARDIAC CELLS

The action potential of the contractile cardiac muscle fiber (Figure 52) is longer in duration (200-220 msec) than that seen in skeletal muscle (2 msec). In cardiac cells there are four phases to the action potential.

Phase 0, voltage gated Na+ channels open.

Phase 1, voltage gated Na+ channels inactivate and voltage gated K+ channels open.

Phase 2 (plateau), voltage gated Ca++ channels open and voltage gated K+ channels remain open.

Phase 3, only voltage gated K+ channels are open and cells repolarize.

Phase 4, all of the voltage gated channels are closed and the resting membrane potential is restored by the Na/K ATPase.

Note that the entry of Ca++ in phase 2 is essential for initiating contraction and triggering the opening of the Ca++ gated Ca++ release channel (ryanodine receptor).

One other point, each action potential results in one contraction. One contraction (twitch) is ~250 msec, almost the same duration as the action potential (200 msec). This is due to the prolonged plateau phase 2.

Question 57

Cell membranes - water transport

1. Which is higher concentration?

[pure water] [water with Na+ ions]

Answer 57

1. Pure water has the highest concentration of water

Question 58

In the heart, electrical activity (depolarization and repolarization) proceeds in a sequential manner.

1. Starts in ?
2. Moves through? Name of wave? Physical result?
3. Where next? Something happens to it? Physical result?
4. Where next?

Answer 58

1. Normally each heart beat starts in the pacemaker cells of the sinoatrial (SA) node located in the right atria.
2. From the SA node, the wave of depolarization moves through both atria (P wave), resulting in atrial contraction.
3. The impulse then passes through the intranodal pathways connecting the SA node with the atrioventricular node (AV node). At the AV node the impulse slows allowing the atria to contract before the ventricles depolarize.
4. The impulse then passes from the AV node through specialized conducing tissue known as the Bundle of His. The Bundle of His branches (left and right) within the septum that separates the ventricles and then into the Purkinje fiber system, which carry the impulse through the ventricular walls (QRS complex).

This specialized conduction system ensures that the ventricles contract in a synchronized fashion and results in a contraction that begins at the apex (tip) of the heart. This is important because blood is ejected through the valves (pulmonic and aorta) that are located at the base of the heart (at the A-V junction).

Question 59

Predict what would happen in a skeletal muscle if the voltage gated K+ channel is inactivated.

A. longer action potential due to slower repolarization

B. shorter action potential due to faster repolarization

C. has no effect on action potential duration

Answer 59

A. longer action potential due to slower repolarization

Voltage-gated K+ channels (Kv channels), present in all animal cells, open and close upon changes in the transmembrane potential.

Kv channels are one of the key components in generation and propagation of electrical impulses in nervous system.

Upon changes in transmembrane potential, these channels open and allow passive flow of K+ ions from the cell to restore the membrane potential.

Question 60

John is almost finished with his 5 mile bike race. Relative to his baseline condition at the start of the race, the amount of O2 delivered to his leg muscles is:

A. increased due to the rise in temperature and fall in pH.

B. increased due to the rise in temperature and rise in pH.

C. decreased due to the shortened time for equilibration across the alveolar membrane.

D. decreased due to the rise in blood CO2 which displaces O2 on Hb.

Answer 60

A. increased due to the rise in temperature and fall in pH

Question 61

In normal hearts which of the several pacemakers available sets the pace?

Answer 61

The pacemaker cells set the rate of the heartbeat. They are anatomically distinct from the contractile cells because they have no organized sarcomeres and therefore do not contribute to the contractile force of the heart.

There are several different pacemakers in the heart but the sinoatrial node (SA) is the fastest. In normal hearts, the SA node is the pacemaker.

The other conduction tissue (AV), Bundle of His and Purkinje Fibers will take over in disease states according to their speed of depolarization (AV > bundle of His >Purkinje).

Question 62

Which of the following determines the strength of contraction in all three muscle types (skeletal, smooth, cardiac)?

number of cross bridges formed
kinetics of the myosin ATPase
activation of the voltage gated sodium channel
unmasking of the thin filament

Answer 62

number of cross bridges formed

Question 63

Hearing

1. Draw the organ of corti

Answer 63

Question 64

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.}

1. In addition, the sensory neuron activates an …???… neuron which …???... 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).
2. The muscle spindle reflex is important in allowing maintenance of the ...???... of a certain muscle. e.g. holding ……???……???…

Answer 64

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.}

1. In 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).
2. The muscle spindle reflex is important in allowing maintenance of the length of a certain muscle. e.g holding a drink

Question 65

What is the function of the sarcoplasmic reticulum (SR)?

A. intracellular organelle that generates ATP

B. intracellular organelle that stores calcium ions

C. cell surface transporter for calcium efflux

D. T tubule channel for calcium influx

Answer 65

B. intracellular organelle that stores calcium ions

Question 66

The Circulatory System

2. In advanced atherosclerosis, calcified plaques cause the normally muscular arteries to become narrow. What happens to resistance in these vessels?

A. Resistance increases

B. Resistance decreases

C. Resistance remains unchanged

Answer 66

Answer 2: A. Resistance increases

Question 67

Taste

1. Name the five types of taste receptor
2. How many flavours can a taste bud respond to and under what conditions?

Answer 67

TASTE

_{Taste ligands dissolved in saliva bind to chemoreceptors on taste buds.}

_{Receptor binding raises intracellular Ca++ causing the release of neurotransmitters and producing graded potentials.}

_{This leads to the initiation of action potentials in the postsynaptic neuron.}

1. Taste buds can detect chemicals that can be categorized into five different flavors: sweet, sour, salty, bitter, and umami.

Each type of chemical is detected by different receptors.

2. Each taste bud responds primarily to one flavor at low concentrations and

two or three at higher concentrations.

Question 68

Total lung capacity is:

A. measured with a spirometer.

B. approximately 500 ml in an adult.

C. the sum of residual volume and vital capacity.

D. the sum of FRC plus tidal volume.

Answer 68

C. the sum of residual volume and vital capacity.

Question 69

A bundle of muscle contracts rhythmically and in unison even when the nerve supply is cut. The cells have poorly developed T tubules. What type of muscle is this?

B. fast twitch skeletal muscle

C. multiunit smooth muscle

A. single unit smooth muscle

Answer 69

A. single unit smooth muscle

MULTI-UNIT smooth muscle fibers are innervated independently. The fibers are not connected by gap junctions. Depolarization of one fiber is followed by contraction of that fiber only. These fibers are richly innervated by the autonomic nervous system. Nervous stimuli and hormones cause contraction (or relaxation) of these fibers, not stretch. The smooth muscle of the lung airways, in the walls of large arteries, and attached to the hair of the skin are multi-unit fibers.

SINGLE UNIT smooth muscle fibers are connected by gap junctions. Depolarization of one fiber triggers synchronous depolarization throughout the bundle followed by contraction of the fiber bundle. That is, many fibers act as one sheet. Single unit fibers are found in the walls of small blood vessels, the GI tract, and uterus where stretching of one fiber creates a coordinated contraction

Question 70

If a person is stabbed with a knife and air enters the intrapleural space (pneumothorax), the most likely response would be for the:

A. lung to expand outward and the chest wall to spring inward

B. lung to expand outward and the chest wall to spring outward

C. lung to collapse inward and the chest wall to collapse inward

D. lung to collapse inward and the chest wall to spring outward

Answer 70

D. lung to collapse inward and the chest wall to spring outward

Question 71

Joan rose quickly from her bed to answer the front doorbell. In response to rising, her baroreceptors:

decreased firing

had no change in their firing rate

increased firing

Answer 71

decreased firing

Question 72

Heart

1. What is Ejection Fraction =

Answer 72

EJECTION FRACTION (EF) describes the efficiency of the heart. It is Stroke volume(SV) divided by end diastolic volume (EDV) times 100.

EF (%) = SV/ EDV x 100

During strenuous exercise, CO can increase to 30-35 L/min.

What parameter (stroke volume or heart rate) limits this increase in CO? [Answer: heart rate.]

As heart rate increases, the time for contraction and relaxation of the cardiac muscle shorten; the filling time limits CO.

Question 73

Contrast the following:

(i) velocity of blood flow in capillaries
(ii) velocity of blood flow in aorta
(ii) > (i)
(i) = or nearly = (ii)
(i) > (ii)

Answer 73

(ii) > (i)

Question 74

Heart Electrical Activity

Tom, an 80 yr old male, presents to his physician with a resting heart rate of 35 bpm.

1. You classify his heart rate as:

A. Normal

B. Bradycardia

C. Tachycardia

2. His pacemaker is most likely located at the:

A. Sinoatrial node

B. Atrial-ventricular node

C. His Bundle-Purkinje

Answer 74

Answer 1: B. Bradycardia

Answer 2: C. His Bundle-Purkinje

Question 75

John is a 27 year old marathon runner. He theorizes that breathing 100% O2 should increase the amount of O2 in his blood about 5-fold because room air is 21% O2. Which of the following statements is the most accurate answer to his hypothesis?

A. The amount of O2 carried by Hb will increase markedly but the amount of soluble O2 in his blood will remain the same.

B. The amount of O2 carried by Hb in the blood will not rise appreciably.

C. The amount of O2 carried by Hb in the blood will rise 5-fold.

Answer 75

B. The amount of O2 carried by Hb in the blood will not rise appreciably

Question 76

The volume of a sound is conveyed to the brain through:

the portion of the basilar membrane which vibrates
the amount of fluid that leaves the cochlea
the frequency of action potential production

Answer 76

the frequency of action potential production

Question 77

Neurons

1. Neurons signal to one another through a specialized junction called a ?

Answer 77

Neurons signal to one another through a specialized junction called a synapse.

_{The synapse is where the electrical signal from one neuron (presynaptic neuron) is transmitted to another neuron (postsynaptic neuron).}

Depending on the role of a particular neuron, it can receive signals from many presynaptic neurons (convergence) or it can send signals to many postsynaptic neurons (divergence).

The presynaptic neuron causes a graded potential to occur in the postsynaptic neuron. The graded potential can depolarize the postsynaptic membrane, which makes the potential closer to threshold, and is called an excitatory postsynaptic potential (Figure 26, synapses 1 and 2).

Alternatively, the graded potential can hyperpolarize the postsynaptic membrane, which makes the membrane potential farther from threshold, and is called an inhibitory postsynaptic potential (Figure 26, synapse 3). Since presynaptic neurons cause graded potentials in postsynaptic neurons, spatial and temporal summation of signals from multiple synapses can occur so the postsynaptic neuron can integrate information

Question 78

Heart rate is increased by the sympathetic nervous system and decreased by the parasympathetic nervous system. Which of the following changes will increase heart rate?

A increased sympathetic nervous system tone
B decreased sympathetic nervous system tone
C increased parasympathetic nervous system tone
D decreased parasympathetic nervous system tone
both A and D

Answer 78

both A and D

Question 79

Neurons

1. How do neurotransmitters effect the post-synaptic neuron?

Answer 79

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 80

Muscle

1. How is the maximal amount of force a muscle can generate determined?
2. Draw graph

Variation in active tension with muscle fiber

Answer 80

Length-Tension Relationship.

The maximal amount of force (tension) a muscle can generate is determined by the degree of overlap of the thick and thin filaments (Figure 46). The basal state and slightly stretched state provide optimal force generation (Figure 46). Because the muscle is anchored to bone within the body, conditions of excess stretch or non-overlap and excess contraction are avoided. However, with injury, irreversible damage to the actin and myosin filaments can occur.

Question 81

Colligative

1. How does the boiling point of a solution compare to that of the pure solvent?
2. ΔT_b =

Answer 81

1. The boiling point of a solution is

higher(nonvolatile solute) /

lower (volatile solute) than that of the pure solvent.

2. The boilingpoint depression is given as
   ΔTf = iK_bm
   where Kf is the molal boiling point depression constant,

m is the molality of the solution, and

i is the van’t Hoff factor equal to the number of particles the solute
dissociates into. For nonelectrolytes, i = 1. For electrolytes, i = number of ions per
formula.

Question 82

1. What unusual ion channels do pacemaker cells in the heart have?
2. What are they called?

Answer 82

Pacemaker cells

have the unique property of being able to generate action potentials spontaneously (i.e. without input from the nervous system). They can generate an action potential because their resting membrane potential (- 60mV) is unstable.

This potential exists because the pacemaker cells have unusual channels that are permeable to both Na + and K+. These channels are called If channels. _{The “f” is derived from the fact that they were originally called “<strong>funny</strong>” channels because the If channels are Na+ channels with unusual properties}. When the If channels opens, the influx of Na+ exceeds the efflux of K + and the net influx of positive charges slowly depolarizes the cell.

As the membrane potential becomes more positive, the If channels close and the Ca++ channels open transiently, which further depolarize the cell.

When the threshold potential is reached, a burst of Ca++ channels open, more Ca++ rushes in, and a steep phase of depolarization (Phase2) occurs (Figure 56). At the peak of the action potential, K+ channels open, K+ rushes out of the cell and the cell repolarizes

Question 83

Do the sarcomeres change in length with contraction?

A. Yes. Sarcomeres shorten due to sliding of the thin and thick filaments past each other.

B. No. Sarcomeres are attached to the Z lines and do not shorten with contraction.

Answer 83

A. Yes. Sarcomeres shorten due to sliding of the thin and thick filaments past each other.

Question 84

In the disease, Duchenne muscular dystrophy, a large molecule called dystrophin is not synthesized properly. This protein is critical for linking the sarcomere to the plasma membrane and in turn to extracellular connective tissue elements. In the absence of a functional dystrophin, contractile activity causes the affected muscle cells to rupture. Why does the sarcomere have to be attached to the plasma membrane?

A. Attachment permits the filament to pull against the cell surface during contraction thereby shortening the entire cell.

B. Without this anchoring only the interior filaments would shorten and the cell would stay the same length.

C. Attachment allows for rapid removal of calcium across the cell membrane preventing excess shortening.

D. A and B

Answer 84

A. Attachment permits the filament to pull against the cell surface during contraction thereby shortening the entire cell.

Dystrophin is a protein located between the sarcolemma and the outermost layer of myofilaments in the muscle fiber (myofiber). It is a cohesive protein, linking actin filaments to another support protein that resides on the inside surface of each muscle fiber’s plasma membrane (sarcolemma). This support protein on the inside surface of the sarcolemma in turn links to two other consecutive proteins for a total of three linking proteins. The final linking protein is attached to the fibrous endomysium of the entire muscle fiber.

Dystrophin supports muscle fiber strength, and the absence of dystrophin reduces muscle stiffness, increases sarcolemmal deformability, and compromises the mechanical stability of costameres and their connections to nearby myofibrils; as shown in recent studies where biomechanical properties of the sarcolemma and its links through costameres to the contractile apparatus were measured,[5] and helps to prevent muscle fiber injury. Movement of thin filaments (actin) creates a pulling force on the extracellular connective tissue that eventually becomes the tendon of the muscle.

Question 85

Cardiac Performance

Consider the Pressure-Volume (PV) Loop below. The black PV loop (designated by ABCD) depicts the Left Ventricle of a normal heart.

2. What occurs at C and G?

A. AV valve closes

B. aortic valve opens

C. AV valve opens

D. aortic valve closes

Answer 85

Answer 2: B. aortic valve opens

Question 86

14. Atrial depolarization occurs during:

A. P wave

D. PR segment

B. QRS complex

E. ST segment

C. T Wave

Answer 86

A. P wave
Well done!

Question 87

What is the total amount of blood circulating in the body in a time interval?

Answer 87

The right side of the heart has a thin muscular wall and works at low pressures. Contraction of the right ventricle (RV) pumps blood into the pulmonary circulation (lungs) where oxygen is taken up and carbon dioxide is eliminated.

The left side of the heart has a thicker muscular wall and works at higher pressures. Contraction of the left ventricle (LV) pumps blood into the systemic circulation for delivery to the limbs and to all of the organs.

The right atrium (RA) receives blood returning from the systemic circulation;

the left atrium (LA) receives blood from the lungs (Figure 59).

Total amount of blood circulating is ~5 liters/ minute

Question 88

Locomotion

_{Walking and running require the legs to alternate between forward flexion (the swing phase) and backward extension (the stance phase).}

_{The repetition of this pattern is synchronized with the other leg so that the two legs remain in opposite phases.}

In most animals, if the spinal cord is separated from the brain the four legs can still make coordinated walking motions.

1. This is accomplished through ..?….?….?.. which are oscillatory neural circuits of lower motor neurons in the spinal cord.

Answer 88

Locomotion

_{Walking and running require the legs to alternate between forward flexion (the swing phase) and backward extension (the stance phase).}

_{The repetition of this pattern is synchronized with the other leg so that the two legs remain in opposite phases.}

In most animals, if the spinal cord is separated from the brain the four legs can still make coordinated walking motions.

This is accomplished through central pattern generators which are oscillatory neural circuits of lower motor neurons in the spinal cord.

_{Even though these circuits control the basic movements of walking, they are greatly influenced by the brain. For instance, running occurs when the brain causes the central pattern generators to shorten the stance phase.}

_{In addition, posture and goal-directed locomotion require input from the brain.}

_{However, the central pattern generators allow relatively simple modifications by the brain to control a very complicated process such as locomotion}

Question 89

Which of the following statements is correct?

A. Phasic contractions are single twitches that can summate to a fused tetanus.

B. Multiunit smooth muscle is electrically coupled by gap junctions.

C. Tonic contractions are continuous contractions exhibited by single unit smooth muscle

D. Tonic contractions are single twitches exhibited by multiunit smooth muscle

E. A and C

Answer 89

E. A and C

A. Phasic contractions are single twitches that can summate to a fused tetanus.

C. Tonic contractions are continuous contractions exhibited by single unit smooth muscle

Question 90

Predict the O2 binding curve for fetal Hb relative to adult Hb?

A right shifted indicating higher affinity for O2

B left shifted indicating higher affinity for O2

C right shifted indicating lower affinity for O2

D left shifted indicating lower affinity for O2

E identical to adult Hb

Answer 90

B left shifted indicating higher affinity for O2

Question 91

Balance

1. Explain the difference between the utricle and saccule in the vestibular system of the inner ear.

_{(anatomy and consequences)}

Answer 91

_{Otolith organs}

_{The otolith organs contain sheets of hair cells that have calcium carbonate crystals, called otoliths, embedded in gel that surrounds the stereocilia of the hair cells.}

_{Since the otoliths are heavier than the fluid around the hair cells, they remain stationary and pull on the stereocilia during linear movements.}

The utricle contains hair cells that point straight up in a standing postion and respond to horizontal linear acceleration.

The saccule contains hair cells that are oriented at a 90 degree angle compared to those of the utricle (Figure 35).

This allows them to detect up and down motions

Question 92

Neuron

1. What is a graded potential?
2. Do they have a refractory period?

Answer 92

1. A graded potential is a transient change in the membrane potential that decreases in magnitude as it spreads out along the plasma membrane of the neuron and is proportional to the intensity of the stimulus.
2. Graded potentials can stimulate or inhibit neurons and have no refractory period, or time period when the cell cannot respond to a stimulus after the first change in potential

Question 93

Hormones

1. How are peptide hormones delivered and why?
2. How are steroid hormones delivered and why?
3. How are amine hormones delivered and why?

Answer 93

1. Peptide hormones are soluble in blood. They are degraded by the liver and then cleared by the kidney with half-lives of a few minutes.
2. Steroid hormones and
3. thyroid hormone are not soluble in blood.

They circulate bound to protein carriers. Binding to the transport carrier protein extends the half-life of the hormone in the blood (60-90 minutes for steroids, several days for thyroid hormone)

Question 94

Endocrine system coordinates and integrates cellular activity within the whole body by chemicals (hormones) delivered by blood.

1. Specific missions are to (6 really 9)

Answer 94

Regulate sodium and water balance

Regulate calcium balance

Regulate energy balance

Coordinate processes that cope with stressful environments

Coordinate growth and development.

Coordinate processes associated with reproduction and lactation.

Question 95

Hearing

1. How is the pitch of sounds encoded
2. How is the loudness of sounds encoded

Answer 95

_{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 96

Eye

1. Draw the anatomy of the eye
2. Indicate where most focusing is done

Answer 96

Question 97

Mineral homeostasis in the bones

1. Draw a diagram showing the bones place in mineral homoeostasis

Answer 97

image LINK

Question 98

How does stretch get Ca++ into smooth muscle to activate the muscle?

Answer 98

MEMBRANE ACTIVATION

Contraction of smooth muscle, like skeletal muscle, is dependent on a rise of cytosolic Ca++ due to changes in the plasma membrane. However, smooth muscle does not have T tubules. Instead Ca++ enters from the ECF by diffusion through calcium channels in the plasma membrane. These Ca++ channels include: voltage-gated channels, ligand-gated channels and mechano-gated channels. The inputs that regulate contraction include:

Autonomic nervous system via voltage gated Ca++ channels.
Hormones via ligand-gated Ca++ channels.
Stretch via mechano-gated Ca++ channels.

At any one time, multiple inputs, some excitatory and others inhibitory, can be activated in a single cell. The net effect is dependent on the relative intensity of these inputs. Note that the intracellular Ca++ of smooth muscle can increase (or decrease) due to changes in the membrane potential from graded depolarization, hyperpolarization, or an action potential

Question 99

Two types of muscle sensory receptors

1. The muscle ….??…. is an important muscle sensory receptor that provides information about muscle length and the rate of change of muscle length.

Answer 99

Two types of muscle sensory receptors

_{In order for the body to be able to control muscle contraction properly, there must be feedback about the contractile status of individual muscles.}

The muscle spindle is an important muscle sensory receptor that provides information about muscle length and the rate of change of muscle length.

_{In addition, Golgi tendon organs are encapsulated sensory receptors situated in tendons near the junction with the muscle (Figure 38). They detect changes in muscle tension instead of changes in muscle length.}

_{Both types of sensory receptors send information to the spinal cord and the brain that is usually subconscious.}

Question 100

In smooth muscle cells, a pacemaker potential:

always reach threshold
activate with the influx (entry) of Cl-

activate with the efflux (exit) of Na+

vary in size

Answer 100

always reach threshold

Pacemaker cells exhibit an unstable resting membrane potential leading to rhythmic states of depolarization followed by repolarization