Human Anatomy Lecture Exam #3 Ch. 16

List the three major components of the gross anatomy of the spinal cord

1. Conus medullaris

2. Cauda equina

3. Filum terminale

Conus medullaris

• Is the terminal spinal cord at L1

• Stops age 4

Cauda equina

• Cauda = tail

• equina = horse

Filum terminale

• Terminal thread

Study

What is in the spinal cord meninges and place in order from superficial to deep

Superficial

1. Epidural space

2. Dura mater

3. Subdural space

4. Arachnoid mater

5. Subarachnoid space

6. Pia mater

Deep

Epidural space

• Above

• Real

Subdural space

• “Potential” space

Subarachnoid space

• Contains CSF

  • Reason why it is unique!

What are the three meninges and place them in order from superficial to deep

Superficial

1. Dura mater

2. Arachnoid mater

3. Pia mater

Deep

Dura Mater

• Tough outer layer

• Thickest layer

• Directly under skull and vertebral column

• Provides protective covering for brain and spinal cord

Arachnoid mater

• Middle layer

• Web-like structure

• Beneath dura mater

• Contains subarachnoid space

  • Filled with cerebrospinal fluid that cushions the brain and spinal cord

Pia mater

• Delicate inner layer

• Thinnest layer

• Directly adhering to the surface of the brain and spinal cord

• It follows the contours of the brain, including the sulci (grooves) and gyri (ridges)

Study

List what is located in the nuclei of gray mater in the spinal cord?

• Posterior horn

• Gray commissure

• Lateral horn

• Anterior horn

Posterior horn

• Afferent

• Sensory

• Axons of sensory neurons

• Cell bodies of interneurons

• unipolar

Function of posterior horn

Receives sensory information from the body, including pain, temperature, touch, and relays it to the brain

Structural classification of neuron in posterior horn

• Somatic sensory neuron (receptor)

• Visceral sensory neuron (receptor)

• Posterior root ganglion

Somatic sensory

Pain and pressure receptors in skin

Visceral sensory

Stretch receptors in smooth muscle (like organs) from viscera

Posterior root ganglion

Collection of cell bodies of sensory neurons

Anterior horn

• Efferent

• Motor

• Cell bodies of somatic motor neurons that innervate skeletal muscle

• Multipolar

Function of anterior horn

Sends signals from motor neurons to skeletal muscles, enabling movement and motor control

Structural classification of neuron in anterior horn

• Autonomic (visceral) motor neuron (effectors)

• Somatic motor neuron (effectors)

Autonomic (visceral) motor neuron

Innervates and controls smooth muscle, cardiac muscle, and gland tissue

Somatic motor neuron

Innervates skeletal muscle, enabling voluntary movements and muscle contractions

Lateral horn

• Efferent

• Motor

• Cell bodies of autonomic (visceral) motor neurons

• Multipolar

Function of lateral horn

Fuses spinal cords, controlling the autonomic nervous system

Autonomic (visceral) motor neurons

Innervates smooth muscle, cardiac muscle, and glands

Study

Study

What are the four nerve plexuses?

• Cervical nerve plexus

• Brachial nerve plexus

• Intercostal nerve - No thoracic plexus

• Lumbar nerve plexus

• Sacral nerve plexus

Cervical Nerve plexus

• Innervates the muscles of the neck

• Has phrenic nerve

  • Innervates diaphragm

Brachial nerve plexus

Supplies upper limbs

What are the five major Brachial plexus terminal branches that innervate the arm?

• Axillary nerve

• Median nerve

• Musculocutaneous nerve

• Radial nerve

• Ulnar nerve

Motor innervation of axillary nerve

Arm abduction

Sensory innervation of axillary nerve

Superolateral arm

Motor innervation of median nerve

Wrist, digit flexors

Sensory innervation of median nerve

Palmar aspects and dorsal tips of lateral 3 ½ digits

• Thumb

• Index finger

• Middle finger

• ½ ring finger

Motor innervation of musculocutaneous nerve

Forearm flexors

Sensory innervation of musculocutaneous nerve

Lateral region of forearm

Motor innervation of radial nerve

Forearm, wrist, digit extensors

Sensory innervation of radial nerve

• Posterior region of arm

• Posterior region of forearm

• Dorsal aspect of lateral 3 digits

  • Except their distal tips

Motor innervation of ulnar nerve

Wrist, digit flexors

Sensory innervation of ulnar nerve

Dorsal and palmar aspects of medial 1 ½ digits

• Little finger

• medial aspect of ring finger

Study

Lumbar nerve plexus

• Innervates abdomen, some external genitalia, anterior and medial thigh

Sacral nerve plexus

• Innervates:

  • Pelvis

  • Posterior thigh

  • Leg

  • Foot

• The main nerve is the sciatic nerve

  • Largest and longest nerve in the body

Main nerve (sciatic nerve)

Reflexes

Rapid, automatic, involuntary reactions of muscles or glands to a stimulus

What are the characteristics of reflexes?

• Stimulus

• Rapid response

• Automatic response

• Involuntary response

Reflex arc

Neutral wiring of a single reflex

• Receptor in PNS → CNS

What are the steps of a simple reflex arc?

1. Receptor responds

2. Sensory neuron to spinal cord

3. Integration - sometimes by interneuron (monosynaptic and polysynaptic)

4. Motor neuron to effector

5. Effector responds

Study how steps look on diagram

Classification of Ipsilateral

Receptor and effector on the same side

Classification of Contralateral

Receptor and effector on opposite sides

Classification of Monosynaptic

Does not involve interneuron

• Ex: Knee-jerk (stretch reflex)

Classification of Polysynaptic

Involves interneuron

• Ex: Withdrawal reflex