Effectors II

Question 0

I. Ca++ Regulation of Muscle Contraction

A. Ca++ Effect

Answer 0

1. Tropomyosin filaments wrap actin
   - > block myosin binding sites
2. Troponin on Tropomyosin; controls its shape
3. Ca++ binds to troponin
   - > “moves” tropomyosin
   - > exposes actin binding sites for myosin
4. A-M cross-bridges now form (contraction), if and only if ATP in available

figure 39.5 Regulatory Proteins & Ca++ controlling Muscle Contraction

Question 1

Effectors II

parts

Answer 1

I. Ca++ Regulation of Muscle Contraction
II.Muscle Physiology
III. Vertebrate Bone

Question 2

I. Ca++ Regulation ofMuscle Contraction

B. Ca++ Availability

Answer 2

1. Ca++ storage

2. Ca++ release

Question 3

1. Ca++ Storage

Answer 3

a) extracellular fluid
b) sarcoplasmic reticulum (SR)

diagram: muscle fiber and plasma membrane and t tubules

Question 4

2. Ca++ Release

Answer 4

(from SR)

a) NMJ -> EPSP in muscle -> AP

b) AP invades T tubules
=> increase Ca++ release from SR in cytoplasm

c) Ca++ binds to triponin
- > initiate contraction

d) After AP, Vm repolarize, allows Ca++ to be repumped back into SR
=> terminates contraction

Note: AP allows Ca++ entery from outside through VGCCs

Figure 39.6b** Regulation of Muscle Fiber Contraction

Question 5

II. Muscle Physiology

parts

Answer 5

A. Twitch
B. Tetanus
C. Cardiac Muscle

Question 6

II. Muscle Physiology

A. Twitch

Answer 6

single stimulus of motor nerve produces brief contraction

diagram:
- strength of muscle contraction vs stimulus, intensity to nerve
- increase stimulus #axons activated causes increases # of muscle fibers contracting

Note: Motor Unit: #of muscle fibers innervated by same motor neuron
Figure 39.7 Motor Units in vertebrate skeletal muscle

Question 7

II. Muscle Physiology

B. Tetanus

Answer 7

Maximal contraction
-> caused by rapid &repeated stimulation

diagrams:
- strength of muscle contraction vs time
- tetanus strength > maximal twitch
- b/c of [Ca++] ; build up

diagram:

• stimulus frequency
• force of concentration proportional [Ca++], over some range

Figure 39.8 summation of twitches

Question 8

II. Muscle Physiology

C. Cardiac Muscle

Answer 8

1. Different from Skeletal:
   little SR; most Ca++ from extracellular fluid
2. Long duration AP with VGCC activation
   - >lots of Ca++ influx

diagram: Vm vs Time (ms)
sustained Ca+ influx
->sustained contraction
->PUMP

Question 9

IV. Vertebrate Bone

parts

Answer 9

A. Functions

B. Composition

Question 10

IV. Vertebrate Bone

A. Function

Answer 10

1. Support & Protection (e.g. ribs, & skull)
2. Movement (muscle attachment)
3. Ca++ reservoir

Figure 39.12 Bones & Joints of the Human Skeleton
Figure 39.13 Types of Joints

Question 11

IV. Vertebrate Bone

B. Composition

Answer 11

1. Gross Structure
   - muscle comes in antagonistic pairs (e.g. flexor / extensor)
   diagram: bones and muscles
2. Bone Matrix:
3. Cell Types:

Question 12

2. Bone Matrix

Answer 12

a) 70% inorganic salts: Ca++ & PO4-
- very insoluble
- provides COMPRESSIONAL strength

b) Collagen fibers
(protein) ->run parallel to stress lines
- > provide TENSILE strength

Question 13

3. Cell Types

Answer 13

a) osteoblasts
- > synthesize bone

b) Osteocytes
- synthesize & degrade BONE
- > “fine-tune” bone strength

c) Osteoclasts:
degrade bone
->Ca++

Question 14

Osteoblasts

Answer 14

synthesize bone

Question 15

Osteocytes

Answer 15

synthesize & degrade BONE

-> “fine-tune” bone shape

Question 16

Osteoclasts

Answer 16

degrade bone

->Ca++