Figure 46-19

Sarcomere

Myofibril

Dark band Light band

Relaxed

Contracted

Muscle tissue

Bundle of muscle fibers (many cells)

Muscles

Muscle fiber (one cell) contains many myofibrils

Figure 46-24a

Figure 46-20

Myofibril

Relaxed

Contracted

Thin filament (actin) Thick filament (myosin)

Z disk

A

A C

C D

DB

B

Figure 46-24b

Ryanodine receptors line on the sarcoplasmic reticulum

Voltage gated calcium channel in the T-Tubules

Figure 46-23

Myosin head

Troponin

Tropomyosin

Actin

Calcium ionsMyosin binding sites

Calcium ion Troponin-tropomyosin complex, moved

Figure 46-22

CHANGES IN THE CONFORMATION OF THE MYOSIN HEAD PRODUCE MOVEMENT.

1. ATP bound to myosin head. Head releases from thin filament.

2. ATP hydrolized. Head pivots, binds to new actin subunit.

3. Pi released. Head pivots, moves filament (power stroke).

4. ADP released. Cycle is ready to repeat.

Myosin head of thick filament

Actin in thin filament

Experimental evidenceIn vitro motility

Experimental evidenceOptical Tweezers

What stops muscle contraction?ATP is needed to (1) Induce the release of myosin crossbridges from actin.(2) Pump Ca++ back into the sarcoplasmic reticulum.

Forc

e

Time

http://www.dkimages.com/discover/previews/773/258319.JPG

Nerve nets, ganglia, cephalization

Midbrain: reflexive coord, tactile + auditory

Hindbrain: refined limb movement, resp., cardiac, gastric.

Forebrain Voluntary muscle, thought

Sulcus formation

Central Nervous system

Nervous Stysem Organization

Figure 45-19PARASYMPATHETIC NERVES

“Rest and digest”SYMPATHETIC NERVES

“Fight or flight”

Constrict pupils

Stimulate saliva

Slow heartbeat

Constrict airways

Stimulate activityof stomach

Inhibit release ofglucose; stimulategallbladder

Stimulate activityof intestines

Contract bladder

Promote erectionof genitals

Sacralnerves

Lumbarnerves

Thoracicnerves

Cervicalnerves

Cranialnerves

Dilate pupils

Inhibit salivation

Increase heartbeat

Relax airways

Inhibit activityof stomach

Stimulate releaseof glucose; inhibitgallbladder

Inhibit activityof intestines

Relax bladder

Promoteejaculation andvaginal contraction

Secreteepinephrine andnorepinephrine(hormones thatstimulate activity;see Chapter 47)

Figure 45-21b

Lefthemisphere

Intra-abdominal

Tongue

TeethJaw

Lips

NoseE

yeThum

bFingers

Hand

Arm

Head

Tru

nk

Hip

Leg

Gen

itals

How we study the brain:Electrically

Imaging

Lesions

Genetic maps

Figure 44-28

Sinoatrial node

Atrioventricular node

Purkinje fibers

Electrical control and conducting system

30

-30

-60

0

Phase 4

Phase 0

Phase 3

Cardiac pacemaker activity – The sinoatrial node

mV

0 100 200Time (ms)

Key Ion Currents

30

-30

-60

0

mV

0 100 200Time (ms)

Control of heart rateParasympathetic (Vagus nerve) Sympathetic

How do heart rate, vessel resistance and stroke volume help determine blood pressure?

Cardiac Output =heart rate(beats/min) * stroke volume (ml/beat)

Cardiac Output = PA-PV/R R = 8 L/ r4 (r is the “radius of arterioles” aka resistance vessels)

Stroke volume is determined, in part, by effective blood volume (EBV) returned to the heart. Constricting large veins increases EBV. (capacitance vessels). More than half of the blood volume is in veins.

Stand up quickly and feel dizzy?Giraffes? Fighter pilots? Tree-snakes versus land snakes?What organ are we worried about? Where (and how) do we sense blood pressure?

How do heart rate, vessel resistance and stroke volume help determine blood pressure?

Cardiac Output =heart rate(beats/min) * stroke volume (ml/beat)

Cardiac Output = PA-PV/R R = 8 L/ r4 (r is the “radius of arterioles” aka resistance vessels)

Blood pressure plummeting. Three mechanisms!

(1)Cardiac output(2)Diameter of resistance vessels(3)Diameter of capacitance vessels.

HeartHeart

What are directions of flow and the key events in the cardiac cycle?

Systole Diastole

Vena cava

Aorta artery

Pulmonary artery

Pulmonary vein

Conservation of mass: the total blood volume is constant (over minutes to hours).

That means all of the blood passing though the aorta has to equal all of the blood passing though the capillaries in every second!

AortaAorta

Cardiac Output = Area*Velocity = Total Area * Velocity

30

-30

-60

0

mV

0 100 200Time (ms)

Recap: Control of heart rateParasympathetic (Vagus nerve) SympatheticSlow heart rate Increase heart rateAch leads to lower Ica NE increases ICa,IF

Ca channel blockersDigitalis increases vagal activity

What would hyperkalemia (too much K) cause?

How do heart rate, vessel resistance and stroke volume help determine blood pressure?

Cardiac Output =heart rate(beats/min) * stroke volume (ml/beat)

Cardiac Output = PA-PV/R R = 8 L/ r4 (r is the “radius of arterioles” aka resistance vessels)

Stroke volume is determined, in part, by effective blood volume (EBV) returned to the heart. Constricting large veins increases EBV. (capacitance vessels). More than half of the blood volume is in veins.

Stand up quickly and feel dizzy?Giraffes? Fighter pilots? Tree-snakes versus land snakes?What organ are we worried about? Where (and how) do we sense blood pressure?

What are directions of flow and the key events in the cardiac cycle?

Systole Diastole

Vena cava

Aorta artery

Pulmonary artery

Pulmonary vein

Cardiac Output = PA-PV/R R = 8 L/ r4

What is blood?

40% RBC, 60% Plasma

How does the viscosity of blood vary with hematocrit (fraction rbc) or vessel diameter?

hematocrit Tube diameter m

1 10 100 10000 20 40 60 80

The Farheus-Lindvist Effect --- there are fewer red blood cells in the microcirculation because they move faster than all of the plasma!

Rouleaux formation

Faster RBC motion in middle of tube.

Equal areas – different velocities!

Other circulatory systems

Open versus closed

Figure 44-23

Interstitial fluid

Excess fluid in interstitialspace enters lymphatic duct Lymph leaves tissue

Blood enterscapillary fromarteriole (asmall artery)

Net pressure 10 mm Hg out

Osmoticpressure22 mm Hg

Blood pressure32 mm Hg

Capillary

Fluid leaves

Blood leavescapillary tovenule (asmall vein)

Net pressure 7 mm Hg in

Osmoticpressure22 mm Hg

Blood pressure15 mm Hg

Fluid returns

Lymphatic duct

Is it really “closed”?

Plasma and lymphatic exchange : a consequence of the balance of mechanical and osmotic pressures.