Lecture #2 Flashcards Preview

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Flashcards in Lecture #2 Deck (36):
1

Characteristics of muscles

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

2

Types of muscles

1. Skeletal
2. Cardiac
3. Smooth

3

Myofilaments -- the functional contractile unit

- Muscles shorten b/c their individual sarcomeres shorten
Neither thick nor thin filaments change length during shortening - Only the amount of overlap changes

4

Sliding Filament Thoery

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

Elastic filaments (titin) stabilize thick filament and allows recoil

5

Myofilaments - Thick

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

6

Myofilaments - Thin Filaments

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
3. Troponin
• Calcium-binding protein on each tropomyosin molecule

7

2 kinds of muscles

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

8

Striations

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

9

Nerve Relationship

skeletal muscles never contracted unless stimulated by a nerve

10

Muscle fibers of one motor unit

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

11

Excitation

nerve action potentials = muscle action potentials

12

Excitation-contraction coupling

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

13

Contraction

muscle fibers develop tensions and shortens

14

Relaxation

relaxes and turns to resting length

15

The process of Excitation

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

16

The process of Excitation-contraction Coupling

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

17

The process of Contraction

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

18

Latent Period

delay between stimulus and contraction

19

Contraction Phase

time when muscle generates external tension

20

Relaxation phase

—time when tension declines to baseline

21

Recruitment or multiple motor unit (MMU) summation

Occurs according to the size principle

22

Isometric Contraction

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

23

Isotonic Contraction

Muscle changes in length with no change in tension

24

Sensory Receptors and its general properties

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

25

Sensation

a subjective awareness of the stimulus

26

Sensory Receptores

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

27

Phasic receptors

adapt rapidly, smell, hair movement

28

Tonic Receptors

adapt slowly, body position, joint movement

29

Free nerve endings

for pain and temperature
located in skin and mucous membrane

30

Tactile (Merkel discs)

for light touch and tecture

31

Hair receptors

monitor movement of the hair

32

Somatosensory Projection Pathways

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

33

The Chemical Senses

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

34

The Five Primary sensations of taste

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

35

Hearing and Equilibrium

Hearing - a response to vibrating air molecules

Equilibrium- the sense of motion, body orientation, and balance

36

1. Sound
2. Loudness
3. Pitch

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