A&P Midterm (exam #3)

3 types of muscle

skeletal, cardiac, and smooth

shared characteristics

• excitable/responsive (respond to stimulus)

• contractility

• extensibility (stretch and extend)

• elasticity (recoil back to original state)

shared functions (all muscle types)

• movement

• generate heat

Skeletal muscle movement

moving body around

cardiac muscle movement

movement of heart

smooth muscle movement

internal movement (organs)

Cardiac muscle

• bulk of heart walls

• striated*(intercalated discs)

• involuntary* (cannot control)

Smooth muscle

• walls of organs

• moves fluids and ingested solids

• no visible striations*

• involuntary*

Skeletal muscle

• posture (unique function)

• movement of skeleton

• voluntary*

• striated*

• adaptable strength

• multinucleated

insertion meaning

attachment point that moves

origin meaning

attachment point that stays put

action meaning

main action

a fiber =

1 cell

a fascicle=

multiple fibers

a muscle=

multiple fascicles

muscle fibers

• up to a few cm

• striated*

• multiple nuclei visible (fusion from development)

myoblasts

muscle “stem cells”

fiber development

myoblasts→ myotube → skeletal muscle fiber

unique anatomical features

• sarcolemma/transverse (T) tubules (plasma membrane)

• sarcoplasmic reticulum (SR) (stores Ca2+)

• contractile proteins (myosin and actin)

• mitochondria (lots of ATP production

sarcolemma

plasma membrane

excitable-can form and carry out an electrical current

sarcoplasmic reticulum (SR)

• stores Ca2+

• releases Ca2+ when exposed to electrical current

4 tissue types

muscle, nervous, connective, and epithelial

arteries

• blood away from heart to muscle

• nutrient rich

• oxygen, fuel, and calcium

veins

• blood to the heart from the muscle

• nutrient poor

• waster: co2 and lactic acid

contraction requirements

• nutrients

• waste removal

• nervous input

skeletal muscle-vasculature

1 artery + 1 vein per muscle, but lots of capillaries

capillaries

where nutrient + waste exchange happens

Nervous input

the CNS uses neurons to make skeletal muscles contract

Parts of a neuron

NEED TO KNOW: cell body (soma), axon, axon branches, axon terminals

synapse

where a neuron communicates with another cell

Where do neurons synapse with a skeletal muscle?

Neuromuscular junction

how many neurons control each fiber?

1

1 fiber connects to…

1 neuron

1 neuron has many…

branches

1 neuron connects to many…

fibers

What is a motor unit

1 SMN and ALL of the fibers it controls

What happens when a SMN fires?

every NMJ is activated

in 1 neuron, NMJs are where?

spread out among many fascicles

Somatic Motor neuron

type of neuron that always synapses w/ skeletal muscle

How does a contraction become stronger?

More neurons being activated

endomysium

covers muscle fiber

perimysium

covers muscle fascicle

epimysium

covers entire muscle