Spinal Cord and Spinal Nerves

Question 1

Explain how spinal nerves are named

Answer 1

-named with letter corresponding to the region they are in (cervical, thoracic, lumbar, sacral, coccygeal) and a number

Question 2

Number of pairs of spinal nerves attached to cervical area

Answer 2

8; (C1- C8)

Question 3

Number of pairs of spinal nerves attached to thoracic (intercostal) area

Answer 3

12; (T1- T12)

Question 4

Number of pairs of nerves attached to lumbar area

Answer 4

5; (L1- L5)

Question 5

Number of pairs of nerves attached to sacral area

Answer 5

5; (S1- S5)

Question 6

Define plexus

Answer 6

places where the nerves coming out are connected/ networked to each other

Question 7

Name, locate, and identify the area supplied by the cervical plexus

Answer 7

C1-C5; neck

Question 8

Name, locate, and identify the area supplied by the brachial plexus

Answer 8

C5-T1; shoulder

Question 9

Name, locate, and identify the area supplied by the lumbar plexus

Answer 9

L1-L4; lower back

Question 10

Name, locate, and identify the area supplied by the sacral plexus

Answer 10

L4-S4; hip/ butt

Question 11

PROCESS

Answer 11

• sensory neurons come in; cell bodied are concentrated in posterior or dorsal root ganglion that anchor to spinal cord and provide pathways for axon of sensory neuron to come into spinal cord; sensory neuron goes into dorsal root of grey matter (non myelinated) and relays immediately with motor neuron (sometimes stimulates interneuron in between)
• motor response goes back through interior grey horn and comes out through anterior root

Question 12

Define reflex and explain the differences between spinal reflexes and cranial reflexes

Answer 12

-reflex: fast, unplanned sequences in response to stimulus; involuntary, automatic response

• spinal reflexes: sensory signal goes to spinal cord and reroutes right back out from motor nerve to muscle
• ex. patellar reflex: stretching stimulates sensory receptor -> sensory neuron excited -> goes back to spinal cord, within integrating center (spinal cord), sensory neuron activates motor neuron -> motor neuron excited -> effector (same muscle) contracts and relieves the stretching
• cranial reflexes: goes to brain
• ex. pupillary reflex arc: light shines into eye -> light signal goes to brain through optic nerve -> signal comes back through nerves to stimulate muscle to contract

Question 13

Explain the difference between somatic reflexes and autonomic (visceral) reflexes

Answer 13

• somatic reflexes: involve skeletal muscle and happen without your control (ex patellar reflex)
• autonomic reflexes: smooth or cardiac muscle (ex. pupillary reflex)

Question 14

Define reflex arc (reflex circuit) and describe 5 components of a reflex arc

Answer 14

1. sensory receptor: responds to stimulus by producing a generator or receptor potential
2. sensory neuron: axon conducts impulses from receptor to integration center (spinal cord)
3. integrating center: one or more regions within CNS that relay impulses from sensory to motor neurons)
4. motor neuron: axon conducts impulses from integrating center to effector
5. effector: muscle or gland that responds to motor nerve impulses

Question 15

Ipsilateral, contralateral, and crossed extensor reflex

Answer 15

-ipsilateral: stimulus and response happen on same side (ex patellar reflex- the leg that gets struck is the same leg that jerks)

• contralateral: stimulus on one side and response on other side
  (ex. pupillary reflex- iris in other eye also constricts

-crossed extensor reflex: ex step on tack and foot draws away (ipsilateral) and left leg immediately extends to maintain balance

Question 16

Monosynaptic and polysynaptic

Answer 16

• mono: only one CNS synapse/ only one connection
• ex. sensory to motor neuron (patellar reflex)
• poly: multiple CNS synapses; goes through interneurons
• ex. sensory to inter, inter to motor (stepping on tac)

Question 17

Describe the flexor (withdrawal) reflex, and explain why it would be described as intersegmental, ipsilateral, and polysynaptic

Answer 17

-ex when something is hot, remove hand right away

Question 18

Meninges

Answer 18

-around brain and spinal cord
-dura mater: tough outer layer
(subdural space)
-arachnoid mater: middle layer
(sub arachnoid space - CSF)
-pia mater: inner layer (right on spinal cord)

Question 19

Distinguish between sensory (ascending) and motor (descending) tracts and explain how most tracts are named

Answer 19

• sensory tracts go up spinal cord to brain
• motor tracts go from the brain down spinal cord
• named based on where they’re found and what they do (usually indicates position, beginning and end of tract)

Question 20

Be able to identify the names of major sensory and motor tracts (such as spinothalamic and corticospinal tracts) and briefly describe their functions

Answer 20

• sensory tracts: spinothalamic, spinocerebellar
• spinothalamic = transmits pain, temp, and touch to thalamus
• motor tracts: corticospinal, rubrospinal, reticulospinal,, tectospinal
• corticospinal= from cerebral cortex to spinal cord; movement tract

Question 21

Rami

Answer 21

branches that form first coming off of spinal nerves

Question 22

dorsal ramus

Answer 22

• innervates deep muscles and skin of dorsal trunk (muscles and skin of back)
• ex. when bending over

Question 23

ventral ramus

Answer 23

-innervates upper and lower limps and lateral and ventral trunk (all of core muscles, chest, arms, legs, etc)

Question 24

meningeal ramus

Answer 24

-do short reroutes and come right back into vertibrae as well as blood vessels providing to spinal cord and meninges

Question 25

ramus comminicans

Answer 25

-autonomic (loop with ganglion)