Lecture #2

Question 1

Characteristics of muscles

Answer 1

1. Excitability (responsiveness)
2. Conductivity
3. Contractility
4. Extensibility
5. Elasticity

Question 2

Types of muscles

Answer 2

1. Skeletal
2. Cardiac
3. Smooth

Question 3

Myofilaments – the functional contractile unit

Answer 3

• Muscles shorten b/c their individual sarcomeres shorten

Neither thick nor thin filaments change length during shortening - Only the amount of overlap changes

Question 4

Sliding Filament Thoery

Answer 4

Thick and thin filaments slide over one another = sliding filament theory

Elastic filaments (titin) stabilize thick filament and allows recoil

Question 5

Myofilaments - Thick

Answer 5

Made of several hundred myosin molecules, shaped like a golf club
Heads directed outward in a helical array around the bundle


Question 6

Myofilaments - Thin Filaments

Answer 6

1. Fibrous (F) actin: two intertwined strands
   • String of globular (G) actin subunits each with an active site that can
   bind to head of myosin molecule 2. Tropomyosin
   • Blocks active sites on G actin subunits
2. Troponin
   • Calcium-binding protein on each tropomyosin molecule

Question 7

2 kinds of muscles

Answer 7

1. Striated Muscles - have sarcomeres, and alternating light and dark bands
2. Smooth Muscle
   lack sacromeres

Question 8

Striations

Answer 8

Dark = A band -- thick (myosin) and thin (actin) overlap
Light = I band -- thin filaments (actin) only

Question 9

Nerve Relationship

Answer 9

skeletal muscles never contracted unless stimulated by a nerve

Question 10

Muscle fibers of one motor unit

Answer 10

• contract in unison
• dispersed throughout muscle (large SA = weaker contraction)
• long term contraction

Question 11

Excitation

Answer 11

nerve action potentials = muscle action potentials

Question 12

Excitation-contraction coupling

Answer 12

link action potentials on sacrolemma to activation of the myoflimates … preparing them to contract

Question 13

Contraction

Answer 13

muscle fibers develop tensions and shortens

Question 14

Relaxation

Answer 14

relaxes and turns to resting length

Question 15

The process of Excitation

Answer 15

1. Voltage-gated Ca+ channels open in synaptic knob
2. Ca+ enters, which causes the release of ACh
3. ACh binds to receptor
4. Na enters = end plate which opens and creates action potential

Question 16

The process of Excitation-contraction Coupling

Answer 16

1. Action potential spreads down T tubules
2. Open voltage-gated ion channels in T tubules and Ca channels in SR
3. Ca leaves SR and
   enters cytosol, binds to troponin = exposure of active sites on actin

Question 17

The process of Contraction

Answer 17

1. ATPase in myosin head hydrolyzes ATP
2. Activates the head “cocking” it in an extended position
   • ADP + Pi remain attached
3. Head binds to actin active site forming a myosin–actin cross- bridge
4. Myosin releases ADP and Pi, and flexes pulling thin filament with it = power stroke

Question 18

Latent Period

Answer 18

delay between stimulus and contraction

Question 19

Contraction Phase

Answer 19

time when muscle generates external tension

Question 20

Relaxation phase

Answer 20

—time when tension declines to baseline

Question 21

Recruitment or multiple motor unit (MMU) summation

Answer 21

Occurs according to the size principle

Question 22

Isometric Contraction

Answer 22

Muscle produces internal tension but external resistance causes it to stay the same length – Stablizing

Question 23

Isotonic Contraction

Answer 23

Muscle changes in length with no change in tension

Question 24

Sensory Receptors and its general properties

Answer 24

a structure specialized to detect a stimulus

1. Transduction—the conversion of stimulus energy into nerve signals
2. Receptor potential—small local electrical change on a receptor
   cell

Question 25

Sensation

Answer 25

a subjective awareness of the stimulus

Question 26

Sensory Receptores

Answer 26

1. Afferent neurons 2. Epithelial Cells both send signal to integrating centre

Question 27

Phasic receptors

Answer 27

adapt rapidly, smell, hair movement

Question 28

Tonic Receptors

Answer 28

adapt slowly, body position, joint movement

Question 29

Free nerve endings

Answer 29

for pain and temperature | located in skin and mucous membrane

Question 30

Tactile (Merkel discs)

Answer 30

for light touch and tecture

Question 31

Hair receptors

Answer 31

monitor movement of the hair

Question 32

Somatosensory Projection Pathways

Answer 32

from receptor to brain 1st order neuron 2nd order neuron 3rd order neuron

Question 33

The Chemical Senses

Answer 33

``` Taste (Gustation): • stimulants on taste buds • Tastants must dissolve in saliva • Smell (Olfaction): • Response to odorants ```

Question 34

The Five Primary sensations of taste

Answer 34

``` 1. Salty: • by metal ions 2. Sweet: • associated with carbohydrates 3. Sour: • acids such as in citrus fruits 4. Bitter: • associated with spoiled foods 5. Umami: • “meaty” taste of amino acids ```

Question 35

Hearing and Equilibrium

Answer 35

Hearing - a response to vibrating air molecules Equilibrium- the sense of motion, body orientation, and balance

Question 36

1. Sound 2. Loudness 3. Pitch

Answer 36

1.any audible vibration of molecules 2. the perception of sound energy, intensity, or amplitude of the vibration in decibels (dB) 3. sense of whether a sound is “high” or “low” vibration frequency: hertz (Hz) or cycles/second