CH 9: Muscular System -- Histology and Physiology

General functions of muscular system (7)

1. Movement

2. Maintain posture

3. Respiration

4. Production of HEAT

5. Communication

6. Constrict of organs

7. Contract heart

Skeletal muscle tissue

Characteristic: STRIATIONS, Multinucleate, VOLUNTARY

Function: regulate body temp + control breathing

Location: ATTACH TO BONES

• There’s a lot of striations (very thick)

Cardiac Muscular Tissue

Characteristics: INTERCALATED DISCS, INVOLUNTARY, THIN STRIATIONS, Uninucleate

Function: PUMP HEART

Location: HEART

Smooth Muscle Tissue

Characteristic: INVOLUNTARY, NO striations, uninucleate,

Function: CONSTRICT BLOOD VESSELS/ORGANS

Location: INTERNAL ORGANS (digestive tract)

• NO STRIATIONS

  • NOT WAVY unlike dense regular connective tissue

General Properties of Muscle Tissue

• Contractility: Muscles can SHORTEN WITH FORCE

• Excitability: Muscles can RESPOND TO STIMULI

• Extensibility: Muscles can be STRETCHED BEYOND NORMAL

• Elasticity: Muscles can GO BACK TO ORIGINAL LENGTH after being stretched a lot

Label the following 1-9

1. Axon of Motor Neuron

2. Fiber — 1 MUSCLE FIBER that’s SHAPED LIKE A CYLINDER

3. Capillary

4. Endomysium (and 6 is included too)

5. Fascicle — GROUPS OF MUSCLE FIBERS; more than 1 fascicle = muscle organ

6. Endomysium

7. Perimysium

8. Epimysium

9. Muscular Fascia

Label following 1-6

1. Sarcoplasmic reticulum

2. Myofibril

3. Terminal Cisterna

4. T Tubule

5. Terminal cisterna

   1. Triad (the t tubule in the middle and terminal cisterna in both sides of the t-tubule)

Neuromuscular junction (AKA synapse)

1. Presynaptic terminal — where ACTION POTENTIAL ENDS in which RELEASES NEUROTRANSMITTERS into the synaptic cleft

   • When the neurotransmitters are released into the synaptic cleft, it binds to the receptors within there which triggers the opening of ligand-gated Na+ ion channels, ultimately causing depolarization

2. Synaptic cleft — this is the SPACE between PRE AND POSTSYNAPTIC

3. Postsynaptic membrane — this is the RECEIVING END that CONTAINS RECEPTORS the NEUROTRANSMITTERS WOULD BIND TO

Isometric VS isotonic Muscle contraction

Isometric contraction: the LENGTH stays SAME, but there’s FORCE CREATED because it’s holding something

• this helps with MAINTAINING POSTURE

• e.g: holding a dumbell upright

• NO MOVEMENT INVOLVED

Isotonic contraction: the LENGTH CHANGES BECAUSE OF MOVEMENT, but the RESISTANCE (LOAD) stays the SAME

• MOVEMENT INVOLVED

• e.g: doing a bicep curl

  • The muscle changes because there’s movement, but the weight of the resistance stays the same

Process of process of crossbridge cycle (6 steps)

1. The Myosin binding site is BLOCKED because of tropomyosin

2. 1 ATP in the myosin (golf club looking thing) goes through HYDROLYSIS and turns into 1 ADP + inorganic phosphate.

3. Binding site still becomes BLOCKED

4. Ca+ from sarcoplasmic reticulum and BINDS TO TROPONIN, CHANGING ITS SHAPE

5. Tropomyosin that’s attached to the troponin gets DISPLACED because the troponin changed shape

6. The binding site becomes FREE, allowing myosin head to bind to actin filament

Muscle Twitch

CONTRACTION of 1 MUSCLE FIBER

• SMALL MUSCLE CONTRACTION

Summation

ADDING EFFECT of repeated muscle twitches that CAUSE STRONG AND LONG MUSCLE CONTRACTION

Fill in the blank

Fill in the blank

Fill in the blank