Ch13: Peripheral Nervous System - Lecture 1 -

Front 1

What does the Peripheral Nervous System do?

Back 1

- Gathers info from sensory receptors

- Communicates w/ CNS and sends output to the effectors

- includes neural structures outside the CNS:

a) Sensory receptors

b) Peripheral nerves and their ganglia

c) Efferent motor endings

Front 2

Organizations of PNS (diagram)

Front 3

What are sensory receptors classified by?

Back 3

- location

- stimulus type

Front 4

What are the types of sensory receptors based on location?

Back 4

a) Exteroceptors: located on skin

b) Interoceptors (visceroceptors)

c) Proprioceptors

Front 5

What do Exteroceptors respond to?

Back 5

- respond to stimuli arising OUTSIDE body

- touch, pressure, pain, temperature

- most special sense organs

Front 6

What do Interoceptors respond to?

Back 6

- respond to stimuli arising in internal viscera and blood vessels

- sensitive to chemical changes, tissue stretch, and temperature changes

Front 7

What do Proprioceptors respond to?

Back 7

- respond to stretch in skeletal muscles, tendons, joints, ligaments, and connective tissue coverings of bones and muscles

- inform brain of one's movements

Front 8

What are the different sensory receptors based on stimulus type?

Back 8

a) Mechanoreceptors

b) Thermoreceptors

c) Photoreceptors

d) Chemoreceptors

e) Nociceptors

Front 9

What do Mechanoreceptors respond to?

Back 9

- respond to touch, pressure, vibration, and stretch

Front 10

What do Thermoreceptors respond to?

Back 10

- sensitive to changes in temperature

Front 11

What do Photoreceptors respond to?

Back 11

- respond to light energy

Front 12

What do Chemoreceptors respond to?

Back 12

- respond to chemicals

Front 13

What do Nociceptors respond to?

Back 13

- sensitive to pain-causing stimuli

Front 14

Diagram showing receptor level to perceptual level

Back 14

Front 15

What is the structure of the nerve?

Also, where do the different nerves arise? (Cranial, Spinal)

Back 15

Cordlike structures: consist of parallel bundles of axons enclosed in wrappings of connective tissue

1. Cranial nerves - arise from brain

2. Spinal nerves: arise from spinal cord

Front 16

Diagram showing nerve structure

Back 16

- note the epineurium, perineurium, and endoneurium

Front 17

Picture showing nerve structure

Back 17

Front 18

How are nerves classified?

Back 18

- most nerves are mixtures of Afferent and Efferent fibers and Somatic and Autonomic (Visceral) fibers

Classified according to direction of impulse:

a) Mixed nerves - both sensory and motor; impulses to and from CNS

b) Sensory (afferent) nerves - impulses towards CNS

c) Motor (efferent) nerves - impulses only away from CNS

Front 19

Most nerves are mixed, what are the types of fibers in mixed nerves?

Back 19

a) Somatic afferent and Somatic efferent

b) Visceral afferent and Visceral efferent

Front 20

What are Ganglia?

Back 20

Contain neuron cell bodies associated with nerves in PNS

a) Ganglia associated w/ afferent nerve fibers contain cell bodies of sensory neurons (dorsal root ganglia - sensory, somatic)

b) Ganglia associated w/ efferent nerve fibers contain autonomic motor neurons (Autonomic ganglia - motor, visceral)

Front 21

How many spinal nerves are there total, and how many in each section?

Back 21

31 pairs of mixed nerves named for point of issue from spinal cord

- 8 cervical (C1-C8)

- 12 thoracic (T1-T12)

- 5 Lumbar (L1-L5)

- 5 Sacral (S1-S5)

- 1 Coccygeal (C0)

Front 22

Diagram of the spinal nerves branching from the spine

Back 22

Front 23

What are the root pairs that form the spinal nerves?

Back 23

1) Ventral roots:

- contain motor (efferent) fibers from ventral horn motor neurons

- fibers innervate skeletal muscles

2) Dorsal roots:

- contain sensory (afferent) fibers from sensory neurons in dorsal root ganglia and conduct impulses from peripheral receptors

Front 24

Diagram showing the spinal nerve roots, ganglia, vertebrae, etc.

Back 24

Front 25

How long are the spinal nerves?

Also, what are the separate structures as they branch into mixed rami?

Back 25

Spinal nerve length: short (~1-2cm)

Each branches into mixed rami:

1) Dorsal ramus

2) Ventral ramus - larger

3) Meningeal branch - tiny, re-enters vertebral canal, innervates meninges and blood vessels

4) Rami communicantes (autonomic pathways) join ventral rami in thoracic region

Front 26

Which ventral rami form interlacing nerve networks called nerve plexuses?

Back 26

- all ventral rami except T2-T12 form nerve plexuses

Front 27

How is the back innervated?

Back 27

- by dorsal rami via several branches

Front 28

What do the ventral rami of T2-T12 innervate?

Back 28

they become intercostal nerves:

- supply muscles of ribs, anterolateral thorax, and abdominal wall

Front 29

Diagram showing a cross section of the thorax with the main roots and branches of a spinal nerve

Back 29

Front 30

What is a dermatome?

Back 30

Dermatome - area of skin innervated by cutaneous branches of a single spinal nerve

a) All spinal nerves except C1 participate in dermatomes

b) Extent of spinal cord injuries ascertained by affected dermatomes

c) Most dermatomes overlap, so destruction of a single spinal nerve will not cause complete numbness

Front 31

Multiple pictures not sure if necessary to add

Back 31

but we shall see