Vessels, Nerves, and Muscles

Question 1

What are the three layers of large vessels?

Answer 1

1. Tunica intima (layer supporting endothelium)
2. Tunica media (smooth muscle cells)
3. Tunica adventitia (loose connective tissue holding outside of vessel to surrounding tissue)

There is also the vasa-vasorum = small vessels runnings through media and adventitia

Question 2

What are characteristics of large elastic arteries?

Answer 2

Media = primarily elastin
Elastic recoil evens out pulse pressure, maintaining flow during diastole

Example = Aorta and its largest branches

Question 3

What are the characteristics of muscular arteries?

Answer 3

Media = mostly smooth muscle

Inner and outer elastic lamina
Resists pulse pressure and responsive to altered flow needs

Question 4

What are the characteristics of veins?

Answer 4

Media = some smooth muscle with substantial ECM (collagen + little elastin)

Wider and thin walled comapred with arteries of same level

Question 5

How is the nervous system divided?

Answer 5

Central = Brain and spinal cord

Peripheral = sensory and motor nerves, autonomic nervous system

Question 6

What is the structure of a typical motor neuron?

Answer 6

All neurons have: cell body, dedrites, and axons

Action potential from dendrites to axon
Schwann cells generate myelin sheath
Nodes of ranvierr permit rapid saltatory action potential propagation

Question 7

What is myelin?

Answer 7

Insulating layer that forms around nerves from glial cells
Composed of mostly lipids and wraps around axons
Inner membrane leaflets fuse to form dense line
Outer leaflets also fuse to form inter-period line

Question 8

What are the characteristics of unmyelinated fibres?

Answer 8

Slower conducting

Schwann cell encloses one or more axon in a single cleft, many have many clefts

Question 9

What are endonerium, perineurium, and epineurium?

Answer 9

Endoneurium = collagenous tissue on the outside of each peripheral nerve, product of schwann cells

Perineurium = Layers of squamous cells which surround every fascicle within the nerve

Epineurium = Outermost layer of delicate connective tissue (fibroblasts, collagen, and vessels)

Question 10

What are the three different kinds of muscle?

Answer 10

Skeletal
Cardiac
Smooth

Question 11

What are the characteristics of skeletal muscle?

Answer 11

Striated and voluntary
Great bulk of all muscle
Possesses enourmously long syncytial cells
Fusion of myoblasts and myotubes
Peripheral nuclei (lots)
Capillaries between cells (fibres)

Question 12

What are the layers in muscle from biggest to smallest?

Answer 12

Muscle
Fascicle (a bundle of structures)
Fibre (muscle cells)
Byofibril (contracting unit)
Sarcomere (thin actin filaments, thick myosin filaments)

Question 13

A sarcomere is the smallest repeating unit of striated muscle tissue responsible for muscle contrarction. What is the structure of a sarcomere?

Answer 13

Sarcomere = consists of myosin-containing thick filaments and bundles of actin-containing thin filaments

Question 14

What are the different bands and lines found in a sarcomere?

Answer 14

A band / anistropic = thick and thin filaments, overlap
I band / isotropic = thin filaments
H band = thick filaments
M line = middle of the H band / sarcomere
Z disc = end of the sarcomere, attachment of thin filament

Held togtther by highly elastic titin

Question 15

What is the sarcoplasmic reticulum (SR)?

Answer 15

Extends throughout muscle cells, wrapping around the myofibrils made up of sarcomeres

Responsible for the storage of calcium ions (Ca2+) that are used in muscle contraction

Question 16

What are transverse tubules (T tubules)

Answer 16

In-folded plasma membraned with basal lmamina (sarcoplasm) on the SR
Permits propagation of action potential deep into cell to activate calcium release
Activates SR

Question 17

What are the different types of skeletal muscle fibre?

Answer 17

Red fibres (slow twitch motor units)

White fibres (fast twitch motor units

There are also other intermediate fibres

Question 18

What are the characteristics of red fibres?

Answer 18

High myoglobin and cytochromes
Many mitochondria
Resist fatigue but weak contraction
Mostly postural muscles

Question 19

What are the characteristics of white fibres?

Answer 19

Low myoglobin and cytochromes
Fewer mitochondria
Fatigue sensitive but strong
Fine motor control

Question 20

Cardiac muscle is similar to skeletal muscle, but also different. What are some if its identifying traits?

Answer 20

Single central nuclei
Branching attachments
Intercalated discs
Different SR and tubule arrangements
Larger mitochondria

Question 21

What are intercalated discs?

Answer 21

The connect adjacent cardiac muscles

Macula adhesions (desmosome equivalent, but vimetin attachment instead of keratin)

Gap junctions = permit spread of depolarising and entraining adjacent cells

Fascia adherens = equivalent to adherens junctions attaching actin filaments

Question 22

What are the characteristics of a smooth muscle?

Answer 22

No striations
Single cells with central nuclei (cork screw)
Involuntary
Found in vascular, alimentary, genitourinary, respiratory, and ciliary body of eye systems