Chapter 2: Essential Functional Anatomy of the Nervous System

Flashcards covering essential functional anatomy of the central and peripheral nervous systems, cranial nerves, spinal nerve plexuses, peripheral nerve injuries, autonomic nervous system, and sensorimotor processing.

What are the main components of a neuron and their directional functions?

A neuron consists of a cell body, dendrites that conduct information toward the cell body, and an axon that conducts information away from the cell body.

What are the three connective tissue sheaths that wrap nerve structures from individual axons to whole nerves?

The endoneurium wraps around each individual axon, the perineurium wraps around each fascicle (bundle of axons), and the epineurium wraps around groups of fascicles (nerves).

How do afferent neurons and efferent neurons differ in their function?

Afferent neurons are sensory neurons that transmit sensory information toward the CNS, whereas efferent neurons are motor neurons that transmit motor impulses away from the CNS.

How is the human nervous system structurally and functionally divided?

The nervous system is divided into the Central Nervous System (brain and spinal cord) and Peripheral Nervous System. The PNS includes motor (efferent) and sensory (afferent) neurons; motor neurons divide into the autonomic system (involuntary: sympathetic and parasympathetic) and somatic system (voluntary).

How many pairs of cranial nerves exist and where do they originate?

There are 12 pairs of cranial nerves, identified by Roman numerals and names, which arise from the brainstem within the skull to innervate head and neck structures.

What are the primary functions and classifications of cranial nerves CN I through CN IV?

CN I (Olfactory): Sensory, olfaction (smell); CN II (Optic): Sensory, vision; CN III (Oculomotor): Motor, moves eye up, down, medially, raises eyelid, constricts pupil; CN IV (Trochlear): Motor, moves eye down and medially (superior oblique muscle).

What are the primary functions and classifications of cranial nerves CN V through CN VIII?

CN V (Trigeminal): Both, mastication and sensation to face and TMJ; CN VI (Abducent): Motor, abducting the eye (lateral rectus muscle); CN VII (Facial): Both, facial expression and taste (anterior two-thirds of tongue); CN VIII (Vestibulocochlear): Sensory, hearing and vestibular sense.

What are the primary functions and classifications of cranial nerves CN IX through CN XII?

CN IX (Glossopharyngeal): Both, swallowing, taste, and salivation; CN X (Vagus): Both, visceral regulation and speech; CN XI (Spinal accessory): Motor, scapular elevation (trapezius) and head rotation (sternocleidomastoid); CN XII (Hypoglossal): Motor, movements of the tongue.

How many total pairs of spinal nerves are in the body and how many are in each regional group?

There are 31 pairs of spinal nerves grouped into 5 regions: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.

How do spinal nerve exit locations relative to vertebrae differ between cervical and lower regions?

Spinal nerves C1–C7 exit above their corresponding vertebrae (with C1 exiting between C-1 and the skull), whereas C8–L5 exit below their corresponding vertebrae.

What functional differences exist between ventral/dorsal nerve roots and ventral/dorsal rami?

Ventral nerve roots carry motor impulses, while dorsal nerve roots carry sensory impulses. Ventral rami innervate the ventral body wall and all limb parts, while dorsal rami innervate the skin and muscles of the back.

What is a dermatome and why is it clinically useful?

A dermatome is an area of skin supplied by an individual spinal nerve. It is used clinically to assess the level of spinal cord injury (SCI).

Which spinal roots form the cervical plexus and what structures do its terminal nerves innervate?

The cervical plexus is formed by the anterior rami of C1–C4 spinal nerves. Its terminal nerves innervate the diaphragm and neck muscles.

What is the correct anatomical sequence of structural divisions in the brachial plexus?

Roots (ventral rami C5–T1) -> Trunks -> Divisions -> Cords -> Branches.

What are the 5 main terminal branch nerves derived from the brachial plexus?

The axillary, musculocutaneous, median, radial, and ulnar nerves.

What spinal roots form the axillary nerve and what muscles does it innervate?

The axillary nerve arises from C5 and C6 and innervates the deltoid and teres minor muscles to position and stabilize the shoulder for reaching.

What spinal roots form the musculocutaneous nerve and what is its motor function?

The musculocutaneous nerve arises from C5, C6, and C7 and innervates shoulder and elbow flexors essential for ADL and IADL functions.

What spinal roots form the radial nerve and what is unique about its motor innervation?

The radial nerve arises from C5–T1 and innervates muscles that extend the elbow, wrist, fingers, and thumb. All of its motor innervation occurs proximal to the wrist.

What spinal roots form the ulnar nerve and what key motor roles does it fulfill in the hand?

The ulnar nerve arises from C8 and T1. It supplies forearm flexors near the elbow as well as intrinsic hand muscles important for grip and lateral (key) pinch.

What spinal roots form the median nerve and what functional roles does it serve?

The median nerve arises from C5–T1 and innervates muscles for forearm pronation, finger flexion, and thumb motion, while providing sensory innervation to the radial aspect of the palm and fingers.

How do neuropraxia, axonotmesis, and neurotmesis differ?

Neuropraxia is a mild direct injury or temporary conduction block; axonotmesis is the interruption of the axons; neurotmesis is the complete interruption of the entire nerve structure.

Which spinal roots form the lumbar plexus and what are its two primary motor nerves?

The lumbar plexus originates from L1–L4, and its primary motor nerves are the femoral nerve and the obturator nerve.

What spinal roots form the femoral nerve and what muscles does it innervate?

The femoral nerve arises from L2–L4 and innervates the iliacus, quadriceps femoris group, pectineus, and sartorius muscles.

What spinal roots form the obturator nerve and what clinical gait pattern is linked to tightness in its motor group?

The obturator nerve arises from L2–L4 and primarily innervates hip adductors. Tightness or spasticity in these muscles can contribute to a scissor gait pattern.

What spinal roots form the sciatic nerve and what muscles does it innervate before dividing?

The sciatic nerve arises from L4–S3 and is the largest nerve in the body. Before dividing at the knee into the tibial and common fibular nerves, it innervates the hamstrings and adductor magnus.

What spinal roots form the tibial nerve and what is its primary motor targets in the leg?

The tibial nerve arises from L4–S3 and passes down the posterior leg to innervate the gastrocnemius, soleus, and other ankle plantar flexor muscles.

What spinal roots form the common fibular nerve and what muscles does it innervate?

The common fibular nerve arises from L4–S2 and passes to the anterior aspect of the lower leg to innervate ankle dorsiflexor and toe extensor muscles.

How do origin sites and example functions differ between the sympathetic and parasympathetic nervous systems?

Sympathetic fibers arise from the thoracic and lumbar spinal cord for 'fight or flight' actions (increases cardiovascular/respiratory activity, slows digestion, dilates pupils/bronchi). Parasympathetic fibers arise from the brainstem and sacral spinal cord for 'rest and digest' actions (decreases cardiovascular/respiratory activity, increases digestion, constricts pupils/bronchi).

What are somatosensation, proprioception, and stereognosis?

Somatosensation is tactile sensation received from the skin, limbs, and joints; proprioception is sensory information from joints about body position and movement; stereognosis is the ability to identify an object based on sensory input alone.

What are the step-by-step cortical stages of the sensorimotor process?

1. Primary sensory cortex (perceives/discriminates sensory info)
2. Secondary sensory cortex (recognizes specific sensation)
3. Association cortex (connects perception to memory and interprets meaning)
4. Motor planning areas (plans movement, sequence, and timing)
5. Primary motor cortex (executes planned motor response via efferent commands).

In which cerebral lobes are the sensory cortex and motor cortex located?

The sensory cortex is located in the parietal lobe, while the motor cortex and motor planning areas are located in the frontal lobe.