Nerve & Muscle Physiology

Rahul Dave’Rdave2@uic

9/6/2002

Lecture 1

• How can a solution be hyperosmotic, but isotonic?

• What is the function of cholesterol in membranes?

• Questions on other topics …

Lecture 2• Nernst Eqn:

• Permeability:

• The Hodgkin Cycle

• Questions???

inout

zE log60

OUT][][][][][][log60

ClPKPNaPClPKPNaPE

ClinKinNa

CloutKoutNa

Lecture 3

• What affects conduction velocity

• How does a membrane get depolarized?

• Ionotropic vs Metabotropic receptors

• Questions???

The Autonomic Nervous SystemSympathetic Parasymp

PreganglionicNTLength

Ach (N)Short

Ach (N)Long

PostganglionicNTLength

Epi/NorepiLong

Ach (M)Short

Pre/Post Ratio High(Diffuse)

Low(Specific)

ANS continued

• Remember constrict, dilate: (general)

• Sympathetic: Epi, but Norepi controls BP.

1 = heart, 2 = lung (1 heart, 2 lungs).

DCBA

Even more ANS …

• Sympathetic Responses

• Parasympathetic Responses

• Pupils, HR, Micturition/Defecation

• Mike Broman’s ANS review:http://www.geocities.com/mbroma1/Physio1.htm

Lecture 7

• Hypertrophy vs Hyperplasia

• Smooth vs Striated muscle

• Questions????

Lecture 7: The Bands

Lecture 8

• Size principle

• Large vs small motor units

• The crossbridge cycle

• Questions???

Lecture 9

• Skeletal vs. Cardiac muscle

• Length-Tension relationship

• Questions???

Lecture 10

Preload: The force (load) a muscle exertsprior to contraction.

Pre-contraction load

Afterload: Force muscle exertsduring contraction.

After [the start of] contraction load

Lecture 11

• Oxygen Debt: Consume first, make later– ATP > Creatine-P > lactate prod > Aerobic

• Due to Cori cycle– Lactate formed in muscle– Converted to glucose in liver

Fiber Types

Metabolism ATPase activity

Fatigue Resistance

Contraction Adaptation Example

White Fast

Glycolysis + - Short term phasic

hypertrophy Power lift

Slow Red Oxidative - ++ Sustained tonic

Incr mt myoglobin

Postural mm

Fast Red Oxid/Glyc + + Sustained phasic

both rowing

Resting Membrane Potential

Inside outside PermeabilityNa 40 500 10K 100 1 1

mV 601004010

150010log60

m

V

LEVER MECHANICS

A muscle generates 60 grams to lift a 10 gram object. The total length of the lever arm is 42 inches. How far from the joint is the insertion of the muscle?

(10/60) x 42in = 7 in

POWER AND WORK

To complete 1 revolution on a bicycle, 50 Newtons of force must be used. Each revolution covers 2 meters. During a 10 minute exercise, an individual maintains 100 rev/min.

(1)     W = Fxd = 50 x (100x10x2) = 100,000 J(2)     P = W/t = 100000 J/600s = 167 W

VELOCITY AND LEVERAGE

The biceps is 30 cm long and 5 cm away from the elbow. The distance between the hand and elbow is 25 cm. The speed of the biceps is 6 musclelengths per second; the speed of the hand is approximately …

Biceps moves 6x30 = 180 cm/sec.The hand moves 25/5 = 5 times as fast as the joint180 cm/sec x 5 = 900 cm/sec

Efficiency Calculations

A 70-kg individual does 20 pullups, lifting his body weight 1 meter each time. In doing so, he consumes 4 liters of O2. Baseline is 400 ml of O2/min. Total exercise time is 5 mins. What is his gross and net mechanical efficiency.

Answer …

W = mgh = (70 x 9.8 x 1) x 20 reps = 13.7 kJ= 13.7/4.186 = 3.3 kCal

Total E = 4 x 4.8 = 19.2 kCalNet E = (4 – 0.4x5) x 4.8 = 9.6 kCalGross Efficiency = W/E = 3.3/19.2 = 17%Net Efficiency = 3.3/9.6 = 34%

Don’t forget to …

• Do the TLEs and Mallard (may have mistakes)

• Make sure you know the question sheet

• The exam will be taken from the handouts

Good Luck!!!!