CH12/13 Flashcards
CNS, Central Nervous System
- Brain (cerebrum, cerebellum, brainstem)
- Spinal cord
PNS, Peripheral Nervous System
all nerves and sensory structures outside the brain and spinal cord
- 12 pairs of cranial nerves
- 31 pairs of Spinal nerves
- Ganglion: small masses of tissue; (clusters of nerve cell bodies)
- Sensory Receptors (in skin)
Ganglion
small masses of tissue; (clusters of nerve cell bodies)
Somatic Nervous System
Voluntary (skeletal muscles)
Autonomic Nervous system
Involuntary (smooth muscle, cardiac, glands)
- Includes the sympathetic, parasympathetic, enteric nervous systems
Sympathetic Nervous System
Increase Heart Rate, supports exercise, emergency situations, ‘flight or flight response’
- You sympathize
Parasympathetic Nervous System
slow heart rate; ‘rest and digest’ response/activities
Enteric nervous System
Regulates GI function/motility, neurons that extend the GI Tract.; Sensory neurons of ENS monitor stretching of GI Tract walls
Sensory Function
detection of stimuli
- sense changes through sensory receptors (changes in the internal/ external environment)
- process begins in the PNS and sent to the CNS
- Sensory neurons serve this function
Integration function
- Decision making; analyzing incoming sensory information
- The CNS determines the response to stimuli
- Association and interneurons serve this function
Motor Function
response to stimuli, initiates action
- From the CNS, motor output signals target effectors (muscles and glands) in the PNS.
- stimulate tissues to control body movement and gland secretion.
- Motor neurons serve this function
Which part of the neuron is the endoplasmic reticulum?
Nissil Bodies - rough ER, constantly replaces the cell membrane (normal process of growth and repair)
What do the dendrites do?
Tree like branches that receive or input of information
Which type of neuron has several dendrites and one axon?
Multipolar
* Most common type!
* Several dendrites extending from the cell body, one axon
* motor and interneurons, which make up most of the brain and spinal cord.
Define Neuroglia
- specialized tissue cells that support the neuron. Also known as glial cells
- attaches neurons to blood vessels; “acts as glue”
- produces myelin sheath around the axon
- carries out phagocytosis
Define Neuron
- functional cell of the nervous system (nerve cell)
- have the property of electrical excitability!
- Cellular Structures
What type of glial cell is found on the cell body in the PNS?
Schwann cells:
wrap around neuron axons in the PNS forming myelin sheaths
satellite cells: maintain the health of neurons and protect them
Satellite cells
wrap around the neuron cell body
Define myelination
process of wrapping around axons to form layers of myelin
Glial cell of the CNS
- Astrocytes
- Oligodendrocyte
- Microglial cells
- Ependymal cells
Astrocytes
- Extension wrap around capillaries in brain to regulate blood entering CNS.
- Removal of excess neurotransmitters
- Looks like a star
Oligodendrocyte
Creates myelin sheath
Microglial cells
phagocytosis
Ependymal cells
creates & circulates cerebrospinal fluid (CSF)
cushions and nourishes the brain and spinal cord
Parkinson’s Disease
Neurons in CNS breakdown/die, Tremors, affects movements
Alzheimer’s Disease
plaques found in the brain. Atrophy of brain/ breakdown of energy production within the cells.
memory loss
Guillain-Barré syndrome
demyelination PNS
a condition in which the body’s immune system attacks the nerves. It can cause weakness, numbness or paralysis
Multiple Sclerosis
- Myelin around neurons is loss in the CNS (demyelination occurs)
- difficulties walking, visual problems, pain
Stroke
- blood supply to brain is stopped. Neurons die (lack of oxygen)
- sudden weakness, loss of speech
ALS- Amyotrophic Lateral Sclerosis
- motor neurons from brain and spinal cord (CNS) to the voluntary muscles; motor neurons stop functioning.
- muscle weakness
Lyme Disease
- Bull’s eye rash
- bacteria spread by ticks; bacteria enters bloodstream via tick attachment.
- chills, fever, neurological problems (facial palsy, stiff neck)
Spina Bifida
- failure of the spinal cord to develop properly
- paralysis, bladder & bowel difficulties; spine disorder
Nerve Fibers
bundles of axons classified according to their diameter and degree of myelination
Type A Nerve FIber
- Motor neurons that innervate skeletal muscles
- large diameters = highly myelinated
- Action potential: very fast conduction
Type B Nerve FIber
fibers are lightly myelinated; intermediate diameters
Type C Nerve FIber
unmyelinated; smallest diameters: slowest conduction
Define Propagation
process by which an electrical impulse travels along the membrane of a nerve cell
Factors that affect Propagation
- axon diameter
- amount of myelination
- Temperature
True or False
Myelin sheath increase from birth to maturity
T
Nodes of Ranvier
- Also known as neurofibril nodes
- Gaps between the myelin sheath
- Plasma membrane exposed
Define a synapse
where neurons connect and communicate with each other
How many cranial and spinal nerves are there?
12 pairs of cranial nerves and 31 pairs of spinal nerves
Meninges
Protective 3-layer covering that run continuously around the spinal cord and brain
Meningeal Layers
Pia Mater
thin delicate inner layer; denticulate ligaments are thickenings of pia mater that suspend the spinal cord
Meningeal layers
Arachnoid mater
middle spider web-like layer
Meningeal layers
Dura mater
tough protective outer layer; extends to cover and protect the pairs of spinal nerves that extend from the cord at the level of each vertebra
Epidural space
outside of the dura mater is a space filled with fat and large blood vessels; adipose tissue contributes to the protection of the spinal cord
Cerebrospinal fluid
- Clear and colorless fluid; produced by the choroid plexus of the brain.
- Acts as a cushion to help prevent injury.
- CSF is found in the subarachnoid space (between the arachnoid and pia mater).
- Spinal Tap: is done to withdraw CSF for diagnostic purposes
Arachnoid villi role?
- facilitate the reabsorption of cerebrospinal fluid (CSF) from the subarachnoid space back into the venous circulation.
- This process helps maintain intracranial pressure and ensures proper brain function
Where does the spinal cord begin?
Continuation of the medulla oblongata and ends at L1-L2 in adults, in children ends at L3-L4
Where does the spinal cord end?
End of the spinal cord is called Conus medullaris: tapered portion of the spinal cord
What is cauda equina?
Where the spinal roots hang off the end of the spinal cord, means horse’s tail
Grey matter
- cell bodies and unmyelinated axons
- butterfly-shaped (H Shape)
- Involved in integration of the lower motor neurons that give rise to the axons that control muscle
- dorsal horn(s) and ventral(horns) regions
Posterior (dorsal) horns
contain cell bodies of sensory neurons from the root ganglia
Anterior (ventral) horns
Large cell bodies of the lower motor neurons (LMN). Axons of these lower motor neurons exit each spinal segment as ventral roots
White Matter
- Surrounds the grey matter (H or butterfly shape), made up of myelinated axons
- ascending sensory pathways
- sensory receptors to the brain
ascending sensory pathways
- delivering sensory information
- sensory receptors to the brain
descending motor pathways
carrying motor commands from the brain to the muscles
Motor Tracts
Efferent: descending tracts
Found in anterior and lateral corticospinal tract
carry electrical impulses from brain to body parts, muscles, sometimes glands
Sensory tracts
- Afferent: ascending tracts, known as spinothalamic tracts
- Found in dorsal column
- Action potential travels to sensory neuron carries electrical impulses from body to brain
Role of dorsal horn?
Receives and relays sensory information from body to brain; pain, temperature, touch
Ipsilateral pathway
traveling on the same side of the stimulus or muscle
Contralateral pathway
traveling on the opposite side
Motor pathway
efferent, alpha motor neuron; carry electrical impulses from brain to body parts, muscles, sometimes glands
Sensory pathway
afferent, Action potential travels to sensory neuron carries electrical impulses from body to brain
Decussation
crossing within brainstem or spinal cord
Three order neurons
- First-order sensory neurons: delivers information from the receptor to spinal cord
- Second-order sensory neurons: information will cross over within the thalamus
- Third-order sensory neurons: project the location on the brain where stimulus was perceived
How many neurons are involved in sensory pathways?
3 neurons
What are the two main routes of the sensory pathway?
- Spinothalamic tract: carries information about pain and temperature
- Posterior column tract: carries general somatosensory (touch, pressure, pain, temp.) and proprioceptive (body position/movement) information
Two circuit neuron
Involved in motor pathways
- UMN (Upper Motor Neurons) and LMN (Lower Motor Neurons)
UMN (Upper Motor Neurons)
originate in cerebral cortex and travel down to brainstem or spinal cord, then transfers to LMN in ventral horn of spinal cord
LMN (Lower Motor Neurons)
begin in spinal cord (ventral horn) and send efferent information to muscles/glands
Where does the lateral corticospinal tract decussate at?
Also known as pyramidal tract will decussate in the medulla (at pyramids)
What are the 4 extrapyramidal tracts?
Tectospinal Tract
Vestibulospinal tract
Rubrospinal tract
Reticulospinal tract
Tectospinal Tract
involves reflexive movements of the head, equilibrium, and coordination of visual reflexes
Tech IT, using their eye coordination
Vestibulospinal tract
controls muscle tone and posture that responds to vestibular input from the inner ear allowing us to maintain balance
Vestibular issues make you tilt
Rubrospinal tract
controls limb movement on the basis of cerebellar processing and originates in red nucleus in the brain
Rubro=ruby=red nucleus
Reticulospinal tract
controls body posture as a response to reticular system of the brain; controls level of alertness
Connective tissue coverings of the nerve
- Epineurium: cover the outside of the nerve.
- Perineurium: layer covering the fascicles.
- Endoneurium: layer covering the nerve fiber.
Four main nerve plexuses in the human body
- Cervical plexus supplies nerves to the posterior head and neck, (and diaphragm).
- Brachial plexus supplies nerves to the arm.
- Lumbar plexus supplies nerves to the anterior leg.
- Sacral plexus supplies nerves to the posterior leg
Plexus and the nerve they control
Cervical plexus
- receives input from spinal nerves C1-C5, and phrenic nerve
- Phrenic Nerve: controls diaphragm
- Any damage above C5 will involve mechanical ventilation
Plexus and the nerve they control
Brachial plexus
peripheral nerves of arm
* Axillary, radial, median, and ulnar nerves
Brachial plexus avulsion
Shoulder dystocia: during birth sometimes baby’s shoulders get stuck. From this force this can cause damage to brachial plexus leading to motor and sensory impairments of the arm
Injury
Plexus and the nerve they control
Lumbar and sacral plexus
Lumbar: femoral nerve, obturator nerve, and sciatic nerve (large nerves)
Tactile sensations
- Tactile epithelial cells (merkel cells): light touch, stratum basale of epidermis
- Lamellated (Pacinian) corpuscles: deep pressure, encapsulated endings in hypodermis
- Tactile (Meissner) corpuscle: light touch, encapsulated endings
- Hair root plexus: detect movement of hair at surface of skin (ex: insect on your skin)
- Bulbous corpuscles (Ruffini corpuscles; type II cutaneous mechanoreceptors): stretch receptors
Thermal Sensations
2 types of somatosensory signals: pain and temperature (free nerve endings)
* Temperature: uses thermoreceptors
* Pain: uses nociceptors
Pain Sensations
Nociceptors are in every tissue of the body except brain
- Nociception in the sensation of potentially damaging stimuli
* Mechanical, chemical, thermal or photo (bright light) stimuli beyond a set threshold will elicit the pain sensation
Fast pain
Fast or acute pain occurs rapidly, within 0.1 seconds after a stimulus is applied. myelinated Type A nerve fiber
slow pain
Slow pain is processed and propagated by the unmyelinated Type C nerve fibers. Slow pain tends to increase in intensity and can last a longer time
Dermatome
an area of the skin that provides sensory input via the spinal nerves and one cranial nerve to the central nervous system
Proprioception testing
Simple tests
touching the nose with a finger or touching a location on the skin after it has been touched by the clinician
Proprioception testing
Gait observation
observing the patient’s gait (the way that they walk) or walking heel to toe
Proprioception testing
Romberg test
overall measurment of balance
Hyporeflexia
absent diminished reflex
Hyperreflexia
repeating reflexes; hyperactive
Babinski sign
toes dorsiflex and fan out
* In adults: positive babinski sign = upper motor neuron damage
* In infants: positive Babinski sign is normal (due to incomplete myelination in newborns)
Spinal Cord Injury effects
Paresis:
partial paralysis or weakness of a limb
Spinal cord injury effects
Paraplegia:
paralysis of the lower extremities
Spinal cord injury effects
Quadriplegia:
paralysis of all four limbs
Spinal cord injury effects
Hemiplegia
paralysis of one side of the body
Shingles
a virus known as varicella-zoster virus (VZV); causes chickenpox
* Affects your nerves
Brown- Se’quard syndrome
results in weakness and paralysis on one side of the damage and loss of pain and temperature sensations on the opposite side.
* The left side or the right side of the spinal cord is transected (severed)
Spina Bifida
birth defect of spinal cord, neural tube does not completely close
* Spina bifida myelomeningocele - most severe, projection of meninges and spinal cord through skin
