Jan 24 - Peripheral Nervous System

Question 1

what do spinal nerves do?

Answer 1

• they connect the spinal cord to different parts of the body
• they are essential for transmitting sensory and motor information

Question 2

How many vertebrae is the spine composed of?

Answer 2

33 vertebrae

Question 3

What are the 5 different regions of the vertebrae? how many vertebrae are apart of each region?

Answer 3

• 7 cervical
• 12 thoracic
• 5 lumbar
• 5 sacral
• 3-5 coccygeal

Question 4

how many spinal nerve pairs are there?

Answer 4

31 pairs of spinal nerves

Question 5

what are the 5 spinal nerve pairings?

Answer 5

• 8 cervical
• 12 thoracic
• 5 lumbar
• 5 sacral
• 1 coccygeal

Question 6

How does each nerve emerge from the spinal cord?

Answer 6

it emerges through the intervertebral foramina

Question 7

what kind of fibers are spinal nerves compose of?

Answer 7

afferent (sensory) and efferent (motor) fibers

Question 8

what do the cervical nerves (C1-C8) do?

Answer 8

Innervate the neck, shoulders, arms, and hands

Question 9

what do the thoracic nerves (T1-T12) do?

Answer 9

Control chest, certain abdominal muscles, and mid-back

Question 10

what do the lumber and sacral nerves do?

Answer 10

Innervate lower abdomen, legs, bowel, and bladder.

Question 11

What does the Phrenic Nerve do? where does it originate from? What happens if its damaged?

Answer 11

• The Phrenic Nerve is crucial for breathing, primarily innervating the diaphragm.
• Originates from the cervical spinal nerves C3, C4, and C5.
• Provides motor innervation to the diaphragm, stimulating its contraction for inspiration.
• Damage to the phrenic nerve can result in disphragmatic paralysis or dysfunction, affecting respiratory function.

Question 12

Where do afferent (sensory) nerves originate from?

Answer 12

They originate in the dorsal (posterior) root ganglion, entering the spinal cord through the dorsal root.

Question 13

What do efferent (motor) nerves originate from?

Answer 13

They originate in the ventral (anterior) horn of the spinal cord and exit through the ventral root.

Question 14

What are skeletal muscles composed of?

Answer 14

muscles fibers, connective tissue, blood vessels, and nerves

Question 15

What is each fiber and what surrounds each one of those?

Answer 15

Each muscles fiber is a single muscle cell, surrounded by a plasma membrane called sarcolemma.

Question 16

What do muscle fibers contain?

Answer 16

They contain myofibrils, which are made up of repeating units called sarcomeres - the basic functional units of muscle fibers.

Question 17

How are sarcomeres arranged and what do they do to the appearance of muscles?

Answer 17

Sarcomeres are arranged in series and give muscles their striated appearance.

Question 18

what is the sliding filament theory?

Answer 18

• Muscle contraction is driven by the sliding filament theory.
• Upon stimulation, myosin filaments within the sarcomere pull on actin filaments causin the sarcomere to shorten.

Question 19

What is a motor unit? what does it do/ what is it made of?

Answer 19

• a motor unit consists of a single motor neuron and all the muscle fibers it innervates/controls.
• a muscle can have many motor units; each controls a subset of fibers in the muscle.

Question 20

What is the difference between size of motor units?

Answer 20

• Fine movement muscles (e.g. in the eye) have smaller units with only a few muscles fibers.
• While larger, more powerful muscles (e.g. quadriceps) have larger motor units.