BIOS 1300 Chapter 13 Part 2 - Spinal Cord

How many cervical spinal nerves are there and where do they start and end.

8 nerves that start above the C1 vertebra and end blow the C7 vertebrae.

How many spinal nerves are in the thoracic, lumbar, sacral, and coccygeal?

12, 5, 5, and 1.

What are dorsal and ventral nerve roots?

initial segment of nerves leaving or entering CNS

What is the difference between dorsal and ventral roots?

Dorsal roots are sensory and ventral roots are motor.

What does it mean that spinal nerves are mixed?

It means that are both sensory and motor nerves.

What does ramus mean in terms of the spine?

Ramus = branch

What is the dorsal ramus?

It is a smaller branch of the spinal cord that delivers sensory and motor fibers to the muscles and skin of your back.

What is the ventral ramus?

It is a larger branch of the spinal cord that delivers sensory and motor fibers to most other muscles and provide some sensation. It is everywhere else but where thoracic is.

What are the communicating rami?

They branch off ventral ramus and go to and from the sympathetic ganglia. It is located from T1-L2.

What are all of the plexuses?

cervical, brachial, lumbar, sacral

Where is the cervical plexus?

C1-C4 (neck), includes the phrenic nerve.

What does the brachial plexus include?

3 cords (lateral, medial, posterior), 5 main nerves (musculocutaneous, axillary, median, radial and ulnar).

Where lumbar plexus located and what nerve does it involve?

It is located T12 - L4 and it involves the femoral nerves (quads).

Where is the sacral plexus and what nerves does it involve.

It is located L4 to S4 and involves the sciatic nerve, tibial and common fibular nerves which allows sensation to hamstrings and lower leg muscles.

Where is the Coccygeal plexus located?

S4, S5, and Co1

What are reflexes?

Quick involuntary reaction?

What are parts of somatic reflexes?

1. Somatic receptors

2. Afferent nerve fibers

3. Integrating center

4. Efferent nerve fiber fibers

5. Effectors (muscles)

What does monosynaptic mean?

It means no interneurons so its just a simple stretch reflex.

What does polysynaptic mean?

1 or more interneuron

What is a stretch reflex?

It is protection from overstretch and it helps to maintain posture.

What are muscle spindles?

They are bundles of 7-8 specialized muscle fibers in muscles, they are inside muscles and close to tendons. The number of spindles varies for each muscle.

What is a proprioceptors?

Receptors in muscles, tendons and joints that detect position of the body.

What makes up muscle spindles?

Capsule (shealth)

Intrafusal fibers (inside spindle)

Extrafusal fibers (regular fiber that are force producing)

What do nerves supply? (I might have worded this wrong)

Alpha motor neurons, gamma motor neurons, and sensory nerve fibers (mechanically gated ion channels).

What is a mechanically-gated ion channel?

They are in dendrites of sensory neurons and the open by force for Na+ influx to cause a graded potential.

What is the Full knee-jerk reflex?

contraction of agonist (quadriceps), inhibitory interneuron for antagonist