Anatomy and Physiology of the Spinal Cord, Nervous Tissue, and Autonomic Nervous System

Flashcards for reviewing lecture notes on the spinal cord, spinal nerves, nervous tissue, and the autonomic nervous system.

Protections of the Spinal Cord

Bone (vertebrae), connective tissue (meninges), and fluid (cerebrospinal fluid).

Layers of the Meninges

Dura mater, arachnoid mater, and pia mater.

Beginning and End of the Spinal Cord

Extension of the medulla oblongata at the foramen magnum, terminating at L2.

Cervical Plexus

C1-C5

Brachial Plexus

C5-T1

Lumbar Plexus

L1-L4

Sacral Plexus

L4-S4

Dermatome

Area of skin that provides sensory input to the brain.

Myotome

Group of muscles innervated by a single spinal nerve.

Lesser Occipital Nerve (C2) Distribution

Skin of scalp posterior and superior to ear.

Great Auricular Nerve (C2-C3) Distribution

Skin anterior, inferior, and over ear, and over parotid glands.

Transverse Cervical Nerve (C2-C3) Distribution

Skin over anterior and lateral aspect of neck.

Supraclavicular Nerve (C3-C4) Distribution

Skin over superior portion of chest and shoulder.

Ansa Cervicalis Superior Root (C1) Distribution

Infrahyoid and geniohyoid muscles of neck.

Ansa Cervicalis Inferior Root (C2-C3) Distribution

Infrahyoid muscles of neck.

Phrenic Nerve (C3-C5) Distribution

Diaphragm.

Segmental Branches (C1-C5) Distribution

Prevertebral (deep) muscles of neck, levator scapulae, and scalenus medius muscles.

Phrenic Nerve Mnemonic

C3,4,5 keeps the diaphragm alive.

Brachial Plexus Function

Provides almost the entire nerve supply to the shoulders and upper limbs.

Dorsal Scapular Nerve (C5) Distribution

Levator scapulae, rhomboid major, and rhomboid minor muscles.

Long Thoracic Nerve (C5-C7) Distribution

Serratus anterior muscle.

Nerve to Subclavius (C5-C6) Distribution

Subclavius muscle.

Suprascapular Nerve (C5-C6) Distribution

Supraspinatus and infraspinatus muscles.

Musculocutaneous Nerve (C5-C7) Distribution

Coracobrachialis, biceps brachii, and brachialis muscles.

Lateral Pectoral Nerve (C5-C7) Distribution

Pectoralis major muscle.

Superior Subscapular Nerve (C5-C6) Distribution

Subscapularis muscle.

Thoracodorsal Nerve (C6-C8) Distribution

Latissimus dorsi muscle.

Inferior Subscapular Nerve (C5-C6) Distribution

Subscapularis and teres major muscles.

Axillary Nerve (C5-C6) Distribution

Deltoid and teres minor muscles; skin over deltoid and superior posterior aspect of arm.

Median Nerve (C5-T1) Distribution

Flexors of forearm (except flexor carpi ulnaris), ulnar half of flexor digitorum profundus, some hand muscles, skin of lateral two-thirds of palm and lateral 3 1/2 digits.

Radial Nerve (C5-T1) Distribution

Triceps brachii, anconeus, extensor muscles of forearm, skin of posterior arm and forearm, lateral two-thirds of dorsum of hand, and lateral 3 1/2 digits.

Medial Pectoral Nerve (C8-T1) Distribution

Pectoralis major and pectoralis minor muscles.

Medial Cutaneous Nerve of Arm (C8-T1) Distribution

Skin of medial and posterior aspects of distal third of arm.

Medial Cutaneous Nerve of Forearm (C8-T1) Distribution

Skin of medial and posterior aspects of forearm.

Ulnar Nerve (C8-T1) Distribution

Flexor carpi ulnaris, ulnar half of flexor digitorum profundus, most muscles of hand, skin of medial side of hand and medial 1 1/2 digits.

Klumpke's Palsy

Damage to the nerves in the brachial plexus.

Iliohypogastric Nerve (L1) Distribution

Muscles of anterolateral abdominal wall; skin of inferior abdomen and buttocks.

Ilioinguinal Nerve (L1) Distribution

Muscles of anterolateral abdominal wall; skin of superior and medial aspect of thigh, root of penis and scrotum in male, and labia majora and mons pubis in female.

Genitofemoral Nerve (L1-L2) Distribution

Cremaster muscle; skin over middle anterior surface of thigh, scrotum in male, and labia majora in female.

Lateral Femoral Cutaneous Nerve (L2-L3) Distribution

Skin over lateral, anterior, and posterior aspects of thigh.

Femoral Nerve (L2-L4) Distribution

Largest nerve arising from lumbar plexus; distributed to flexor muscles of hip joint and extensor muscles of knee joint, skin over anterior and medial aspect of thigh and medial side of leg and foot.

Obturator Nerve (L2-L4) Distribution

Adductor muscles of hip joint; skin over medial aspect of thigh.

Superior Gluteal Nerve (L4-L5, S1) Distribution

Gluteus minimus, gluteus medius, and tensor fasciae latae muscles.

Inferior Gluteal Nerve (L5-S2) Distribution

Gluteus maximus muscle.

Nerve to Piriformis (S1-S2) Distribution

Piriformis muscle.

Nerve to Quadratus Femoris and Inferior Gemellus (L4-L5, S1) Distribution

Quadratus femoris and inferior gemellus muscles.

Nerve to Obturator Internus and Superior Gemellus (L5-S2) Distribution

Obturator internus and superior gemellus muscles.

Perforating Cutaneous Nerve (S2-S3) Distribution

Skin over inferior medial aspect of buttocks.

Posterior Femoral Cutaneous Nerve (S1-S3) Distribution

Skin over anal region, inferior lateral aspect of buttocks, superior posterior aspect of thigh, superior part of calf, scrotum in male, and labia majora in female.

Pudendal Nerve (S2-S4) Distribution

Muscles of perineum; skin of penis and scrotum in male and clitoris, labia majora, labia minora, and vagina in female.

Sciatic Nerve (L4-S3) Distribution

Actually two nerves—tibial and common fibular—bound together by common sheath of connective tissue; splits into its two divisions, usually at the knee. As sciatic nerve descends through thigh, it sends branches to hamstring muscles and adductor magnus.

Tibial Nerve (L4-S3) Distribution

Gastrocnemius, plantaris, soleus, popliteus, tibialis posterior, flexor digitorum longus, and flexor hallucis longus muscles.

Medial Plantar Nerve Distribution

Abductor hallucis, flexor digitorum brevis, and flexor hallucis brevis muscles; skin over medial two-thirds of plantar surface of foot.

Lateral Plantar Nerve Distribution

Remaining muscles of foot not supplied by medial plantar nerve; skin over lateral third of plantar surface of foot.

Superficial Fibular Nerve Distribution

Fibularis longus and fibularis brevis muscles; skin over distal third of anterior aspect of leg and dorsum of foot.

Deep Fibular Nerve Distribution

Tibialis anterior, extensor hallucis longus, fibularis tertius, and extensor digitorum longus and extensor digitorum brevis muscles; skin on adjacent sides of great and second toes.

Sciatic Nerve Injury Symptoms

Pain extends from the buttock down the posterior and lateral aspect of the leg and foot.

Special Tests - Neural

Straight leg raise and Slump Test

Information Travel in the Spinal Cord

White matter tracts conduct nerve impulses to and from the brain; gray matter receives and integrates incoming and outgoing information to perform spinal reflexes.

Reflex

Fast, involuntary, unplanned response to a particular stimulus.

Ipsilateral

Same side.

Contralateral

Opposite side.

Monosynaptic

One synapse.

Polysynaptic

More than one synapse.

Reciprocal Innervation

Neural circuit simultaneously contracts one muscle and relaxes its antagonists.

Stretch Reflex

Causes contraction of a muscle that has been stretched.

Tendon Reflex

Causes relaxation of the muscle attached to the stimulated tendon.

Flexor (Withdrawal) Reflex

Causes withdrawal of a limb to avoid injury or pain.

Crossed-Extensor Reflex

Maintains balance during a withdrawal reflex.

Shingles

Acute infection of the PNS caused by herpes zoster virus; causes pain, discoloration of the skin and line of skin blisters.

Neurons

Electrically excitable cells that transmit electrical signals.

Sensory/Afferent Neurons

Conveys information to the CNS.

Motor/Efferent Neurons

Conveys action potential from the CNS.

Interneurons/Association Neurons

Process sensory information and elicit motor response.

Neuroglia

Not electrically excitable cells that support, insulate, and protect neurons.

Multiple Sclerosis

Autoimmune disease that causes progressive destruction of myelin sheath.

Epilepsy

Short, recurrent attacks of motor, sensory or psychological function initiated by abnormal synchronous electrical discharges from the millions of neurons in the brain.

Comparison of Somatic and Autonomic Nervous Systems

The somatic nervous system includes sensory and motor neurons. The autonomic nervous system receives input from sensory receptors located in organs, blood vessels, muscles and the nervous system.

Autonomic Motor Pathways

Preganglionic neuron (cell body in the CNS) and the postganglionic neuron (cell body in an autonomic ganglion).

Sympathetic Nervous System (Fight-or-Flight)

Increases alertness and metabolism to be ready for an emergency.

Parasympathetic Nervous System (Rest-and-Digest)

Slows down most body activity.

Location of Sympathetic Preganglionic Neurons

Lateral horns of the gray matter in the 12 thoracic and first 2 or 3 lumbar segments

Location of Parasympathetic Preganglionic Neurons

The nuclei of four cranial nerves (III, VII, IX and X) in the brain stem and in the lateral gray matter of sacral segments 2–4 of the spinal cord.

Cholinergic Neurons

Release the neurotransmitter acetylcholine.

Adrenergic Neurons

Release norepinephrine (noradrenalin).

Autonomic Tone

Balance between sympathetic and parasympathetic nervous system activity and is regulated by the hypothalamus.

Autonomic Dysreflexia

Exaggerated response of the sympathetic nervous system occurring in 85% of individuals with spinal cord injury at or above T6.

Raynaud Phenomenon

Occurs due to excessive sympathetic stimulation of smooth muscle in arterioles of digits; vasoconstriction leads to numbness and ischemia in digits.

Protections of the Spinal Cord

Bone (vertebrae), connective tissue (meninges), and fluid (cerebrospinal fluid).

Layers of the Meninges

Dura mater, arachnoid mater, and pia mater.

Beginning and End of the Spinal Cord

Extension of the medulla oblongata at the foramen magnum, terminating at L2.

Cervical Plexus

C1-C5

Brachial Plexus

C5-T1

Lumbar Plexus

L1-L4

Sacral Plexus

L4-S4

Dermatome

Area of skin that provides sensory input to the brain.

Myotome

Group of muscles innervated by a single spinal nerve.

Lesser Occipital Nerve (C2) Distribution

Skin of scalp posterior and superior to ear.

Great Auricular Nerve (C2-C3) Distribution

Skin anterior, inferior, and over ear, and over parotid glands.

Transverse Cervical Nerve (C2-C3) Distribution

Skin over anterior and lateral aspect of neck.