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Lecture 11

PNB 2264 Lecture Notes - Lecture 11: University Of Manchester, Action Potential, Cytosol

Physiology and Neurobiology
Course Code
PNB 2264

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Notes Day 11
Excitable cells
- Remember the properties of excitable cells and now apply them to muscle cells
- Specific type of cell designed to generate movement
o Associated with bones (skeletal), organs and vessels (smooth muscle) and the
heart (cardiac)
o Stimulated to contract by movement of sodium and potassium across membrane
Physiological functions
- Movement: bones, tendons, muscle
o Via generation of tension
- Posture
o Standing erect
- Respiration
- Heat production
- Communication
- Eating/digestion
Functional Characteristics
- Contractibility
o Fibers shorten, generate force and pull on bones, tissues, vessels, pressure
- Excitability
o Respond to stimulus, CNS, hormones, physical
- Extensibility
o Stretch past original length
- Elasticity
o Recoil after stretch
- Do skeletal muscle push or pull or both?
o Muscles only pull
Skeletal muscle
- They only pull bones
- They drive the movement of bones and tissues
- Requires energy
o Conversion of ATP into work
- Structure dictates function; molecular to marco scale
- It’s the meat you eat
- Deep red color, surface striations
o Hence striated muscle
o Muscle fibers
o Myoblasts
o Neuromuscular
- Sarco prefix
o Sarcolemma muscle cell membrane

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o Sarcoplasm cytosol
o Sarcoplasmic reticulum ER
Muscle fibers
- Fusion of individual muscle cells
o Multiple nuclei
- Fibers fused end-to-end
- Set at birth
- Lengthens during growth
- Diameter changes with use
o Throughout life
- Muscle fibers
o 0.1 to 4 cm length
o 10 to 100 um in diameter
- connective tissue
- blood supply
- nerves
Connective tissue
- external maina next to sarcolemma
o reticular fibers
- endomysium next layer
o loose connective, reticular fibers
- perimysium covers several fibers (fasciculi)
- epimysium (fascia) covers several fasciculi
- fascia
o heavy layer, continuous with connective tissue to bone
o holds muscle intact, transfers energy to bone
- muscles are capable of generating movement through ATP consumption
- comes in different forms with different properties
- can be excited, stretched and recoil back to original length
- now lets talk about how muscle does it
Skeletal muscle fibers
- repeating pattern that extends the length of the skeletal muscle
- the repeating pattern is described as a sarcomere
o defined as one Z-line to another (from the German scientists who first
characterized the structure)
- alpha motor neurons
o cell bodies ventral horn of the spinal cord
o branch within muscles
innervate single muscle fibers
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