Chapter 13 Spinal Cord And Spinal Nerves

Front 1

Spinal Cord

Back 1

** Highway** of the CNS

** Transmits signals to and from brain**

** Respond rapidly to various stimuli

** Controls so many different reflexes

Mixed nerve- Are sensory and motor neurons together

Front 2

Anatomy of the Spinal Cord, The Meninges

Back 2

Three CT layers that covers the Spinal Cord:

Dura Mater (Outer), Arachnoid Mater, and Pia Mater (Inner)

Three spaces:

1) Epidural space: contains fat and CT

2) Subdural space: contains interstitial fluid

3) Subarachnoid space: contains CSF- cerebrospinal fluid

Front 3

Two Enlargements of External Anatomy of Spinal Cord

Back 3

1) Cervical: Nerve to and from Upper limbs

2) Lumbar: Nerves to and from Lower limbs

Conus Medullaris: the end of spinal cord at Level of L1 and L2

Cauda Equina: Spinal nerves below the conus medullaris; Supply lower limbs and pelvic cavity

Front 4

External Anatomy of Spinal Nerves

Back 4

Cervical (C1-C8)

Thoracic (T1-T12)

Lumbar (L1-L5)

Sacral (S1-S5)

Coccygeal (Co1)

Spinal nerves are part of PNS; Have mixed and rely sensory and motor impulses between body parts and spinal cord

Front 5

Ascending Somatic Sensory Tracts

Back 5

Ascends from Body part to Spinal Cord to Brain

Examples:

1) Spinothalamic tracts, 2) Posterior Columns, and 3) Spinocerebellar tracts

Front 6

Spinothalamic Tracts

Back 6

Ascends from body parts to Spinothalamic tracts to Thalamus to Cerebral cortex

Located in Primary Somatosensory area

Sensations transmitted:

Pain, Temperature, Itching and Tingling

Front 7

Posterior Columns

Back 7

Ascends from body parts to Posterior Columns to Thalamus to Cerebral Cortex

Located in Primary Somatosensory Area

Sensations transmitted:

Touch, Pressure, Vibrations, and Joint position

Front 8

Spinocerebellar Tracts

Back 8

Ascends from body parts to Lateral Columns to Cerebellum

Sensations transmitted:

Quality, extend and coordination of Muscle contraction

Also, Maintains posture and balance

Front 9

Descending Somatic Motor Tracts

Back 9

Descends from Brain to Spinal Cord to Body parts in Primary Motor area

Examples:

1) Corticospinal tracts

2) Rubrospinal tract

3) Reticulospinal tracts

4) Vestibulospinal tract

5) Tectospinal tract

Front 10

Corticospinal Tracts

Back 10

** Has voluntary control of skeletal muscle contractions

From cerebral cortex to Corticospinal tracts to body parts

Front 11

Rubrospinal Tract

Back 11

** Control precise movements of distal parts of Upper limb (fingers) muscles

Red Nucleus of Midbrain to Rubrospinal tract to Body parts

Example:

Picking up a pen with fingers

Front 12

Reticulospinal Tracts

Back 12

** Regulates skeletal muscle of the trunk and proximal parts of limbs in response to ongoing body movements

Reticular formation of Brainstem to Reticulospinal tract to Body parts

Example: Walking

Front 13

Vestibulospinal Tract

Back 13

** Regulates skeletal muscle of the trunk and proximal parts of limbs and Maintain balance to response to Head movement

Vestibular nuclei of Medulla Oblongata to Vestibulospinal tract to Body part

Front 14

Tectospinal Tract

Back 14

** Regulates head, eye, and trunk reflectively movement in response to Visual or Auditory stimuli

Tectum of Midbrain to Tectospinal tract to Body part

Alertness to sound and vision

Front 15

Spinal Cord Reflexes

Back 15

They are fast, predictable, automatic, and involuntary response to a stimulus

Types of Reflexes: Inborn, Learned, Somatic, and Autonomic (Visceral)

Front 16

Reflex Arc

Back 16

Neuronal circuit of a reflex; the following components are:

** Sensory receptor: Detects stimulus

** Sensory neuron: Trasmits sensory info to spinal cord

** Integration center: One or more interneurons that receive impulses from sensory neuron and transmit impulses to Motor neuron

** Motor neuron: Transmits motor impulses to effector

** Effector: Body part that responds to Motor impulses

Front 17

Formation of a Spinal Nerve

Back 17

Posterior Root: Always contain Sensory axons

Anterior Root: Always contain Motor axons

When both roots meet they become Mixed spinal nerves

Front 18

Covering of Spinal Nerve

Back 18

Nerve is a collection of many axons

** Epineurium: Dense CT covering the outer surface of entire nerve

** Perineurium: Loose CT enclosing a nerve fascicle

** Endoneurium: Loose CT covering outer surface of individual axons

Front 19

Spinal Cord Plexuses

Back 19

Network of axons coming from Anterior rami of Spinal nerves; Nerves contain both Sensory and Motor axons

There are four primary plexuses

1) Cervical

2) Brachial

3) Lumbar

4) Sacro-coccygeal

T1-T12 DO NOT ENTER formation of plexuses because they are know as Thoracic nerves

Front 20

The Cervical Plexus

Back 20

Formed from Anterior Rami C1-C5

** Sensory axons transmit sensation from the skin of the head, neck, upper chest and Shoulder

** Motor axons transmit to muscles of the neck

** Phrenic Nerve stimulates the diaphragm

Front 21

Brachial Plexus

Back 21

Formed from anterior rami of C5-T1

** Sensory axons transmit Sensation from the skin of the Shoulder and Upper limb

** Motor axons transmit to Muscles of the Shoulder and Upper limb

Front 22

Lumbar Plexus

Back 22

Formed from L1-L5

** Sensory axons transmit Sensation from skin of Abdominal wall, external genitalia, portions of lower limb

** Motor axons transmit to muscles of abdominal wall and lower limbs

Front 23

Sacro-coccygeal Plexus

Back 23

Formed from L4-Co1

** Sensory axons transmit sensation from skin of Anal region, external genitalia, and lower limbs

** Motor axons transmit muscles of lower limb