The Spinal Cord, Spinal Nerves, and Sensory Pathways

These flashcards cover key concepts related to the spinal cord, spinal nerves, sensory pathways, and associated disorders as taught in Human Anatomy BIOL 220.

What structures protect the spinal cord?

The protective structures include the Vertebral Column, Meninges, and Cerebrospinal fluid.

What is the function of Cerebrospinal fluid?

Cerebrospinal fluid serves as a watery cushion for the central nervous system.

What is the epidural space?

The epidural space is the area between the vertebral column and dura mater that provides cushioning.

What is the Dura Mater?

The Dura Mater is a dense irregular connective tissue that begins at the foramen magnum and is continuous with the epineurium of cranial and spinal nerves.

What characterizes the Arachnoid Mater?

The Arachnoid Mater has a webbed appearance due to collagen and elastin.

What is the Subarachnoid space?

The Subarachnoid space is the area where cerebrospinal fluid flows.

What is the Pia Mater?

The Pia Mater is a thin inner layer of the meninges that allows blood vessels to reach the spinal cord.

What are Denticulate ligaments?

Denticulate ligaments suspend the spinal cord and protect against shock and displacement.

What is the function of the spinal cord?

The spinal cord provides two-way conduction pathways and serves as a major center for reflexes.

Where does the spinal cord extend from and to?

The spinal cord extends from the foramen magnum to the level of vertebra L1 or L2.

What is the Conus medullaris?

The Conus medullaris is the inferior end of the spinal cord.

What is the Filum terminale?

The Filum terminale is a long filament of connective tissue that attaches the spinal cord to the coccyx.

What are cervical and lumbar enlargements?

Cervical and lumbar enlargements are areas where nerves for the upper and lower limbs arise.

What is the Cauda equina?

The Cauda equina is a collection of spinal nerve roots located at the lower end of the spinal cord.

What is the structure of white matter in the spinal cord?

White matter is the outer region composed of myelinated and nonmyelinated axons that allows communication between the spinal cord and brain.

What are Funiculi?

Funiculi are continuous tracts of white matter separated by the medial gray matter.

What is the function of ascending fibers?

Ascending fibers carry sensory information to the brain.

What is the role of descending fibers?

Descending fibers carry motor instructions from the brain to the body.

What are commissural fibers?

Commissural fibers carry information from one side of the spinal cord to the other.

What characterizes gray matter in the spinal cord?

Gray matter contains neuron cell bodies, nonmyelinated axons, and neuroglia.

What is the role of dorsal horns in gray matter?

Dorsal horns contain interneurons that receive sensory information from dorsal root ganglion neurons.

What are ventral horns responsible for?

Ventral horns contain interneurons and cell bodies of motor neurons that send axons out via ventral roots.

What is a somatic sensory pathway?

A pathway that carries sensory information from receptors to the brain.

What is the function of the posterior column-medial lemniscus pathway?

To carry fine touch, stereognosis, proprioception, and kinesthesia information to the brain.

What does the spinothalamic pathway carry?

The spinothalamic pathway carries information on pain, temperature, tickle, itch, touch, pressure, and vibration.

What is the primary function of lower motor neurons?

Lower motor neurons serve as the final common pathway for motor neuronal signals.

What are direct motor pathways?

Direct motor pathways (pyramidal pathways) carry information to lower motor neurons directly from the cerebrum.

What are indirect motor pathways?

Indirect motor pathways provide information to lower motor neurons from the brain stem and are integrative in nature.

Define dermatome.

A dermatome is the area of skin innervated by a single spinal nerve.

How do upper limbs dermatomes differ from trunk dermatomes?

Upper limb dermatomes are supplied by the ventral rami of the brachial plexus, while trunk dermatomes are horizontal and in direct lines with their spinal nerves.

What is meant by the term 'nerve plexus'?

A nerve plexus is a network of nerves formed by the ventral rami that branch and join to serve the limbs.

What is Hilton's Law?

Hilton's Law states that any nerve innervating a muscle that produces movement at a joint also innervates the joint and the skin over it.

How many pairs of spinal nerves are there?

There are 31 pairs of spinal nerves.

What distinguishes the brachial plexus?

The brachial plexus is formed by ventral rami of C5–T1 and serves the upper limb.

What is the phrenic nerve?

The phrenic nerve innervates the diaphragm and carries sensory and motor information.

Identify the main branches of the brachial plexus.

Main branches include musculocutaneous, median, ulnar, radial, and axillary nerves.

What does the lumbar plexus primarily innervate?

The lumbar plexus primarily innervates the anterior thigh.

What is the largest nerve of the sacral plexus?

The sciatic nerve is the largest nerve of the sacral plexus.

What role do the tibial nerve and common fibular nerve play in the sacral plexus?

The tibial nerve innervates the posterior lower limb, while the common fibular nerve innervates the anterolateral leg.

What are monosynaptic reflexes?

Monosynaptic reflexes are reflexes that involve just one synapse, such as the knee-jerk reflex.

What are polysynaptic reflexes?

Polysynaptic reflexes involve one or more interneurons and are more common, such as withdrawal reflexes.

What can cause peripheral neuropathy?

Causes of peripheral neuropathy include trauma, repetitive use, and systemic disorders such as diabetes.

Differentiate between paraplegia and quadriplegia.

Paraplegia is paralysis of the lower limbs due to injury between T1 and L2, while quadriplegia is paralysis of all four limbs from cervical spinal cord injury.

What are congenital malformations of the nervous system?

Congenital malformations include conditions like hydrocephalus, neural tube defects, and cerebral palsy.

When do spinal nerves form during development?

Spinal nerves form in week 4 of embryonic development.

How does the PNS change over time?

Over time, PNS structures reach their target organs, and some dermatomes may become displaced.

What are ascending pathways in the nervous system?

Ascending pathways are neural pathways that carry sensory information from the peripheral nervous system to the central nervous system.

What is the function of ascending pathways?

The main function of ascending pathways is to relay information about sensory modalities like touch, pain, temperature, and proprioception to the brain.

What are descending pathways in the nervous system?

Descending pathways are neural pathways that carry motor commands from the central nervous system to the peripheral nervous system.

What is the function of descending pathways?

Descending pathways primarily control voluntary movements and modulate sensory inputs from the peripheral nervous system.

What are examples of major ascending pathways?

Major ascending pathways include the spinothalamic tract, dorsal column-medial lemniscal pathway, and the trigeminal pathway.

What are examples of major descending pathways?

Major descending pathways include the corticospinal tract, rubrospinal tract, and vestibulospinal tract.

What is the cervical plexus?

The cervical plexus is a network of nerves formed by the anterior rami of the first four cervical spinal nerves (C1-C4) that innervate areas of the neck, shoulder, and diaphragm.

What are the main functions of the cervical plexus?

The cervical plexus provides sensory innervation to the skin of the neck and parts of the head, and motor innervation to the muscles of the neck and diaphragm (via the phrenic nerve).

What is the brachial plexus?

The brachial plexus is a network of nerves that arises from the anterior rami of the spinal nerves from C5 to T1 and innervates the shoulder, arm, and hand.

What are the major components of the brachial plexus?

The brachial plexus consists of roots, trunks, divisions, cords, and branches which include major nerves like the axillary, musculocutaneous, median, ulnar, and radial nerves.

What is the function of the median nerve?

The median nerve primarily provides motor function to the flexors of the forearm and sensation to parts of the hand, mainly the thumb, index, and middle fingers.

What common condition can affect the brachial plexus?

Brachial plexus injury or plexopathy can result from trauma, leading to weakness or loss of sensation in the affected arm.

What is the lumbar plexus?

The lumbar plexus is a network of nerves formed by the anterior rami of the first four lumbar spinal nerves (L1-L4) that innervates the lower abdominal wall, pelvis, and parts of the lower limb.

What are the main functions of the lumbar plexus?

The lumbar plexus provides sensory innervation to the skin of the lower abdomen and parts of the groin and motor innervation to several muscles in the thigh, including the quadriceps and iliopsoas muscles.

What is the sacral plexus?

The sacral plexus is a network of nerves that arises from the anterior rami of the lumbar and sacral spinal nerves (L4-S4) and innervates the pelvic region and lower limbs.

What are the major components of the sacral plexus?

The sacral plexus consists of several important nerves, including the sciatic nerve, tibial nerve, and common fibular nerve, which provide motor and sensory function to the posterior thigh, lower leg, and foot.

What is the function of the sciatic nerve?

The sciatic nerve is responsible for motor function to the muscles of the back of the thigh and hamstrings, and it provides sensory input from the lower leg and foot.

What common conditions can affect the lumbar and sacral plexus?

Conditions such as lumbar radiculopathy or sciatica can affect these plexuses, leading to pain, weakness, or numbness in the lower back, thighs, and legs.

What is the gray commissure?

The gray commissure is a band of gray matter that connects the two halves of the spinal cord, playing a key role in interconnecting neurons between the right and left sides.

What is the central canal?

The central canal is a small, fluid-filled channel that runs longitudinally through the center of the spinal cord, containing cerebrospinal fluid (CSF) and playing a role in nourishing and cushioning the spinal cord.