Chapter 13 Flashcards
Principal functions of the spinal cord?
Conduction, locomotion, reflexes, neural integration
What is locomotion?
Simple, repetitive movements coordinated by central pattern generators
What are examples of reflexes?
Posture, coordination, protective responses to pain
What is the spinal cord?
Cylinder of nervous tissue taking up top 2/3 of vertebral canal, arises from brainstem
How many pairs of spinal nerves are there?
31
Regions of spinal cord?
Cervical, thoracic, lumbar, sacral
How are spinal cord regions named?
By the level of the vertebral column the nerves emerge from
What are the grooves on the anterior and posterior sides of the spinal cord?
Anterior median fissure and posterior median sulcus
What is the cervical enlargement?
Thicker cord where nerves of upper limbs come from
What is the lumbar enlargement?
Thicker cord where nerves of pelvic region and lower limbs come from
What is the medullary cone?
A tapered region of lumbar enlargement which gives rise to the cauda equina
What are meninges?
Fibrous membranes that enclose the spinal cord and brain
What is the dura mater?
Outermost meninge, forms dural sheath around spinal cord
What is the epidural space?
Space between sheath of dura mater and vertebral bones, where anesthetics for childbirth are administered
What is the arachnoid mater?
Middle layer of meninges, made of squamous to cuboidal cells
What is the subarachnoid space?
Gap in arachnoid mater filled w/ CSF
What is the pia mater?
Innermost layer of meninges, follows contours of spinal cord and fuses w/ dura to form coccygeal ligament
What are denticulate ligaments?
Extensions anchoring the arachnoid to the dura to limit side-to-side movements
Where does the spinal cord end?
L1 or L2
What is spina bifida?
A congenital defect in which vertebrae fail to form an arch for enclosing the spinal cord
What is gray matter?
Nervous tissue made of unmyelinated neurons which serves as site of synaptic contact and all neural integration
What is white matter?
Nervous tissue made of myelinated axons which carry signals from one level of the CNS to another
What is the gray commissure?
Bridge in gray matter connecting right and left sides
What is the lateral horn?
In gray matter, it contains neurons of sympathetic nervous system
How dense are neurons in anterior horns?
Very, for motor control and limb sensation
How are white matter axons bundled?
3 pairs called columns or funiculi - posterior, lateral, and anterior
What are spinal tracts?
Tracts of myelinated axons that carry info to or from brainstem
What do ascending tracts do?
Carry information up cord
What do descending tracts do?
Carry motor impulses down cord
What is decussation?
Nerves crossing over from one side of body to the other. Ex: left side of brain gets sensory info from right side of body
What are the sensory neurons in ascending tracts?
First-order, second-order, and third-order
What do first-order neurons do?
Detect stimulus and transmit signal to spinal cord or brainstem
What do second-order neurons do?
Carry signal to thalamus
What do third-order neurons do?
Carry signal from thalamus to sensory region of cerebral cortex
What are the major ascending tracts?
Gracile fasciculus, cuneate fasciculus, spinothalamic tract, spinoreticular tract, and posterior and anterior spinocerebellar tracts
What does gracile fasciculus do?
Proprioception - nonvisual sense of position and movements of body
What does cuneate fasciculus do?
Carry sensory signals from upper limb and chest
What does spinothalamic tract do?
Carry signals of pain, pressure, temperature, light touch, tickle, and itch
What does spinoreticular tract do?
Carry pain signals resulting from tissue injury
What do posterior and anterior spinocerebellar tracts do?
Provide cerebellum w/ feedback to coordinate muscle actions
What are the major descending tracts?
Corticospinal tracts, tectospinal tract, lateral and medial reticulospinal tracts, and lateral and medial vestibulospinal tracts
What do corticospinal tracts do?
Carry signals from cerebral cortex for precise, finely coordinated movements
What do tectospinal tracts do?
Reflex of turning head in response to sights and sounds
What do lateral and medial reticulospinal tracts do?
Control muscles of upper and lower limbs (esp for balance), reduce transmission of pain signals to brain
What do lateral and medial vestibulospinal tracts do?
Receive impulses for balance from inner ear
What do poliomyelitis and ALS do?
Cause destruction of motor neurons, causing skeletal muscle atrophy
A bundle of parallel axons within CNS is called a
Tract
A groove on the cerebral cortex is called a
Sulcus
A bump on the cerebral cortex is called a
Gyrus
An interneuron carries impulsed where?
Only within CNS
What separated the cerebrum from the cerebellum?
Transverse fissure
Where is the primary auditory area?
Temporal lobe
What white matter structure connects 2 central hemispheres?
Corpus callosum
What are the components of the brainstem?
Medulla oblongata, midbrain, and pons
What part of brain coordinates skeletal muscle movements?
Cerebellum
In PNS, myelin sheath is formed by what?
Schwann cells
A bundle of myelinated axons is a
Nerve
A collection of nerve cell bodies in PNS is a
Ganglion
Regions of spinal cord
Thoracic, lumbar, cervical, sacral
What is made of gray matter?
Anterior, posterior, and lateral horns
Sequence of structures in a reflex arc?
Receptor, sensory nerve, interneuron, motor nerve, effector
What section of the spinal cord doesn’t form a nerve plexus?
Thoracic
What structure is richest in lipid content?
White matter
What tracts carry information up to the brain in the spinal cord?
Sensory nerves
What is a nerve?
Cordlike organ composed of axons bound together by connective tissue
What are peripheral nerves?
Branches of nerves
Order of nerve wrappings?
Endoneurium, fascicles, perineurium, epineurium
What surrounds a single nerve fiber?
Endoneurium
What is a bundle of nerve fibers?
Fascicle
What is a bundle of nerve fibers, or a fascicle, wrapped in?
Perineurium
What are several fascicles wrapped together in?
Epineurium
What are most nerve fibers type?
Mixed, not purely sensory or motor
What is a ganglion?
A cluster of neurosomas in the peripheral nervous system
How many pairs of spinal nerves?
31
What do posterior roots do?
Send sensory input to spinal cord
What do anterior roots do?
Output motor command of spinal cord
What root has a ganglion?
Posterior
What is the anterior ramus?
Branch which gives rise to nerves of limbs
What is the posterior ramus?
Branch which innervates muscles and joints in skin of back
What is the meningeal branch?
Branch which innervates meninges and vertebrae
What is the intercostal nerve?
A nerve which travels along rib and innervates skin and intercostal muscles for breathing
What are the nerve plexuses?
Cervical, brachial, lumbar, sacral, and coccygeal
What is somatosensory?
Carrying sensory signals from bones, joints, muscles, and skin (opposed to viscera)
What is proprioception?
Brain receives information about body’s position from nerve endings in muscles, tendons, and joints
Nerve of cervical plexus?
Phrenic
Nerves of brachial plexus?
Median and radial
Nerve of lumbar plexus?
Femoral
Nerve of sacral and coccygeal plexuses?
Sciatic
What is sciatica?
Sharp pain travelling from gluteal region, thigh and leg, to ankle
What is a dermatome?
A specific area of skin that conveys a sensory input to a spinal nerve
What is a dermatome map?
A diagram of cutaneous regions innervated by each spinal nerve
What surrounds a single nerve fiber?
Endoneurium
What are reflexes?
Quick, involuntary, stereotypes reactions of glands or muscles to stimulation
What nervous system are reflexes of skeletal muscle?
Somatic nervous system
Steps of a reflex arc?
Somatic receptors > afferent nerve fibers > integrating center > efferent nerve fibers > effectors
What are muscle spindles?
Stretch receptors embedded in muscles
What is the function of muscle spindles?
Informing brain of muscle length and body movements
Where are muscle spindles abundant?
Muscles w/ fine control
What is the stretch reflex?
When a muscle is stretch, it “fights back” and contracts
What is the knee-jerk reflex?
A monosynaptic reflex with one synapse between afferent and efferent neurons
What is a flexor reflex?
Quick contraction of flexor muscles, resulting in withdrawal of limb from an injurous stimulus
What is crossed extension reflex?
Contraction of extensor muscles in limb opposite of the one that is withdrawn
What are tendon organs?
Proprioceptors in a tendon near its junction with a muscle
What is a tendon reflex?
A reflex in response to excessive tension on the tendon, inhibiting the muscle from contracting strongly
Spinal cord trauma facts?
10k-12k ppl in US each year, 55% from motor accidents, risk group men 16-30
What is complete transection?
Complete severance of the spinal cord
What area of spinal cord severance poses threat of respiratory failure?
Above C4
What is paraplegia?
Paralysis of both lower limbs
What is quadriplegia?
Paralysis of all 4 limbs
What is hemiplegia?
Paralysis on 1 side of body
What is paresis?
Partial paralysis or weakness of limbs
What are tendon organs?
Proprioceptors
What branch of a spinal nerve has somas of only sensory neurons?
Posterior root
Where are ganglions?
PNS. Neurosomas
What does somatosensory NOT refer to?
Signals from viscera
Signals that control your handwriting travels down spinal cord in what tracts?
Corticospinal
Components of the diencephalon?
Thalamus and hypothalamus
Components of the diencephalon?
Thalamus and hypothalamus
