Introduction To The Nervous System Flashcards
What does the nervous system do?
Responds to stimuli
Transmits impulses
Controls every function in the human body
What are the basic functional units of the nervous system? What is their function?
Neurons
Responsible for signaling, responding to stimuli, transiting impulses, and information processing
What is the function of glial cells (glia)?
Support nervous system tissue
Help neurons wire together in the developing brain, nurture them in the adult brain, insulate axons, mop up dead cells, recycle used neurotransmitters and protect the brain from infection
What mental and regulatory functions are facilitated by neurons?
Awareness of self and surroundings
Memory, learning and speech
Muscular contraction and glandular secretion
What is a dendrite?
Receives and transmits impulses to the cell body
What is the cell body?
Receives nerve impulses from dendrites
What is the axon?
Transmits impulses away from the cell body
What is the function of neuronal cell bodies?
Contains nucleus
Maintain neuron integrity
What 2 components other then usual organelles does cytoplasm contain? What is their function?
Nissl bodies (endoplasmic reticulum) are prominent in the cytoplasm except where the axon emerges. They produce proteins
Neurofibrils are arranged longitudinally and are
involved in transport
What cellular components can lead to the formation of protein clumps in neurodengenerative diseases.
Neurofibrils
What is a unipolar neuron? Where are they found? How are they organized?
Axon is a single protoplasmic process
Located almost exclusively in spinal nerves and some cranial nerves
Cell bodies are organized in ganglia
What is a bipolar neuron? Where are they found?
Axon and 1 dendrite
Visual, auditory and vestibular pathways
What is a multipolar neuron? Where are they found?
Axon and multiple dendrites
Everywhere else in the nervous system
Describe the difference between dendrites and axons.
Dendrites impulse towards cell body
Axons impulse away from cell body, can have variable length
What is the significance of the morphological classifications of neurons?
Shapes help to maximize function
What are synapses?
Junction between the axonal ending and a muscle cell, gland, or another neuron
Junctional space is called the synaptic cleft
What carries impulses within a synaptic cleft?
Neurotransmitters which are manufactured and released by neurons, can be excitatory or inhibitory
What is the significance of polarization in synapses?
Allows impulse to travel
Impulse always travels from the axon to the next
neuron, muscle cell or gland
What is an excitatory synapse? Where are they found?
Enhances impulse production
Neuromuscular and neuro glandular synapse
Neuronal synapse
What is an inhibitory synapse? Where can they be found?
Hinders production of impulse
Neuronal synapse
What is anterograde axoplasmic transport?
Cell body nutrients are carried in a forward direction from the cell body to the termination of the axon
What is retrograde axoplasmic transport? What is the clinical significance?
Occurs from the distal end of the axon back to
the cell body
Enables return of used or worn out materials to the cell body for restoration
route by which toxins and viruses are transported into the CNS from the peripheral nervous system (ex: rabies)
What is the support tissue (glia) of the CNS?
Astrocytes
Oligodendrocytes
What are the support tissue (glia) of the PNS?
Schwann cells
capsular cells
What is the blood brain barrier? What is its function?
Permeability control system controlling passage between capillaries and the CNS parenchyma; related to tight junctions between endothelial cells.
What are oligodendrocytes? Function? Location?
Small
Form and maintain myelin
Wraps around axons to form tight spiral
Can surround cell bodies (no myelin)
Produces neurotrophic factors that promote growth of damaged factors
What are Schwann cells? Function?
Oligodendrocytes of the PNS
surrounds only one part of myelinated axon
What are capsular cells (satellite cells)?
Glial elements that surround neuronal cell bodies in sensory autonomic ganglia
Help regulate the neuronal chemical environment
What is the ratio of glial cells to neurons?
50:1
What is included in and the function of the CNS?
Brain and spinal cord
Receives, processes and acts on information in the environment
What is the PNS? How are connections made?
Connect CNS to areas outside nervous system
Connections are made via cranial no spinal nerves
Where does the spinal cord extend? What are its extensions?
Extends from the brain stem and through the neck and back
Peripheral extensions are spinal nerves
What are afferent pathways?
Carry info to the brain
Sensory
What are efferent pathways?
Carry info away from brain
Motor
In what NS are afferent and efferent pathways contained?
Both PNS and CNS
Describe the somatic nervous system.
Voluntary control of movements via skeletal muscles
Describe autonomic nervous system.
Control of smooth muscles, internal organs, muscle
including blood vessels, stomach, intestine, liver, kidneys, bladder, genitals, lungs, pupils, heart, and sweat, salivary and digestive glands
Unconscious, involuntary
What are the 2 division of the autonomic nervous system? What is their functions?
Sympathetic fight or flight
Parasympathetic rest and digest
What is blastulation in the development of the nervous system?
Single-layered structure formed after repeated
cleavage of a fertilized egg.
Epithelial covering encases the fluid filled cavity
What are astrocytes? What is their function?
Most numerous cells in CNS
Blood Brain barrier, electrolyte balance,
neurotrophic factors and removal of neurotransmitters from synaptic cleft
What is the function of oligodendrocytes?
Forms the myelin sheath
What is the function of Schwann cells?
Forms the myelin sheath (PNS)
Describe the structure of astrocytes and the function their provide.
Star shaped cell body with irregular processes
End-feet on surface of brain/spinal cord
◦ Form external limiting membrane (glial membrane)
Vascular end-feet form blood brain barrier by surrounding capillaries
◦ Selectively governs the passage of materials into the CNS via the circulatory system
What are some additional functions of astrocytes?
Electrolyte balance of CNS
Neurotrophic factors: promote growth of axons, necessary for survival
Remove certain neurotransmitters from the synaptic cleft
What support cells are highly susceptible to the formation of neoplasms?
Astrocytes
What is gastrulation in the development of the nervous system?
Blastula is reorganized into a multilayered (3) structure known as the gastrula.
What is neurulation in the development of the NS?
Formation of the neural tube from the neural plate through folding process in vertebrate embryos
What 3 layers of cells are formed during gastrulation? What structures does each form?
Ectoderm—outer layer that becomes the skin and nervous system
Mesoderm—middle layer that becomes muscle
Endoderm—inner layer that becomes internal organ systems
What is the notochord?
Signaling center
Source of midline signals that pattern surrounding tissues
Major skeletal element of developing embryo
Describe the further development that occurs in the brain after neurulation?
Swellings/outpouchings form the parts of the brain
Fluid-filled cavities develop into ventricles that contain cerebrospinal fluid
After neurulation what parts of the brain develop?
Prosencephalon (forebrain)
Spinal Cord
Mesencephalon (midbrain)
Rhombencephalon (hindbrain)
What does rostral refer to anatomically?
Anterior, towards the head
What is contained in the forebrain?
Cerebrum
Diencephalon
What is contained in the hindbrain?
Pons/cerebrum
Medulla
Describe the forebrain.
Partially sits in middle and anterior cranial fossa
Largest part of the brain
Develops into two parts:
◦ Telencephalon
◦ Diencephalon
What is the functions of the telencephalon?
Paired cerebral hemispheres (cerebrum)
Contains functional centers for all brain activity
◦ Motor/output and sensory/input
Integrates the highest mental functions
What is the diencephalon? What parts of the brain are included in it?
Deep nuclear structures
Thalamus- relay center of incoming info
Hypothalamus- involuntary CNS control, emotions, hormones
Basal ganglia- movement refinement
How does the eye function as part of the diencephalon?
Eye is an outpouching of the diencephalon and the optic nerves transmits information directly to the thalamus.
Visual pathway is part of CNS
How are gyri and sulci involved in the function of cerebral hemispheres?
Brain growth is limited to size of cranial cavity
Continued growth requires folding into sulci (grooves) and gyri (convolutions)
What is Lissencephaly? What does it result in?
Smooth brain due to disruptions in growth at 6-9
months leading to failure of tissue to fold
Associated with abnormal function
What is Microcephaly? How does it affect a patient?
Arrested growth results in smaller brain and smaller head (regular growth continues until 7 y/o)
Intellectual disability varies depending on severity
What is polymicrogyria? How does it affect the patient?
Excessive folding of the brain leads to formation
of multiple, small gyri
Abnormally thick cortex.
This abnormality can affect either one region of the brain or multiple regions
Intellectual disability, seizures, developmental delays are common associations
What is porencephaly?
Gap in brain tissue
Can have normal brain function
What is Schizencephaly?
Clefts (slits) in brain during development
Can cause development abnormalities
What questions may be asked to detect developmental delays ( that may affect visual system) during a pediatric eye exam?
Were there any problems during the pregnancy?
Did the mother use any alcohol or drugs?
Was the child full term?
Did the child sit up, crawl, walk, talk etc., on time?
Are height and weight appropriate for age?
Head circumference?
School performance?
What are the lobes of the cerebral hemispheres?
Frontal
Temporal
Parietal
Occipital
What are brodmann’s areas?
Classification of cortex into 50 functional areas
Each has physiological function and pattern of connections
What is the functions of the frontal lobe?
Voluntary movement (planning and execution; movement and speech motor)
Connection to limbic system- Personality, initiate, judgment
In front of central sulcus
Sits in anterior cranial fossa
What is the lateral fissure?
Boundary between frontal and temporal lobe
What is the function of the parietal lobe?
Perception of general sensations (pain, temp, position, touch)
Language, attention, awareness, perception
What is the function of the temporal lobe? Where is it located?
Hearing, learning, language
Memory, emotion
Below lateral fissure, base in middle cranial fossa
What is the function of the occipital lobe?
Primary cortex receives visual information
Secondary cortex areas that give us information regarding the visual perceptions
What 2 tissues are contained in the cerebral hemispheres?
Gray and white matter
What is contained in gray matter?
Contains the cell bodies, dendrites and axon terminals of neurons
Where all synapses are located.
What is contained in the white matter? Why is it white?
Made of axons connecting different parts of gray matter to each other and to the rest of the CNS
White due to myelin sheath
What does the cerebral cortex refer to?
Gray matter
Often used incorrectly for cerebrum
What are commissural fibers?
Connect right and left halves of the brain
Ex: corpus callosum, anterior commissure
What are association fibers?
Connect different areas within the same hemisphere
Help the various lobes communicate with each other
What are projection fibers?
Connect the cortex with deeper underlying regions of the brain, brainstem and spinal cord
What are the connections of the corpus callosum?
Genu
◦ Connects homologous parts of the frontal lobes
Trunk
◦ Connects homologous parts of the parietal lobes
Splenium
◦ Connects homologous parts of the occipital lobes
What is a corpus callosotomy?
Cuts corpus callosum
Interrupts spread of seizures between hemispheres
Commissural routes maintain interhemispheric communication
What is the significance of association fibers? What are short association fibers?
Specific bundles of fibers that connect specific parts of the brain
Arcuate are short association fibers
What are projection fibers?
Connect the cortex with deeper underlying regions of the brain, brainstem and spinal cord
Describe the organization of cortical gray matter.
Organized into layer that each have specific functions and communication with CNS for incoming, outgoing and commissural info
What are the growth/development milestones of the brain?
Reaches max size at age 6
Development completes by early 20s
What is the weight and peripheral extensions of the brain?
3 lbs
Cranial nerves
What 3 classifications of senses does the afferent pathway deliver?
General sense: pain, temp, position,
Visceral sense: from organs
Special sense: from sense organs (5 senses)
What 2 classifications of motor function do efferent pathways deliver?
Motor- muscle (somatic)
Visceral- glands (autonomic)
How do developmental abnormalities during neurulation (specifically of the notochord) affect the affect a patient?
Midline structures will not develop properly
Ex: cleft palates, ocular structures
Describe the directional terminology as the neural tube orients in the brain
Anterior= toward front of skull
Posterior=toward back of skull
Ventral (inferior)=toward base of skull
Dorsal (superior)=towards top of skull
How do clinicians refer to parts of the brain?
By using their adjacent cranial fossa
What is another name for the corpus callosum?
What is its function?
Tough body
Interconnect homologous (same regions on opposite sides) area of the 2 hemispheres (motor, sensory, and cognitive)
Bundles connect lobes
What is the anterior commissure? What does it connect?
Connect temporal lobes at midline
Interhemispheric transfer of visual, auditory, and olfactory information between temporal lobes
Describe the process by which seizures occur?
Nerve cell activity is disturbed, increasing activity
Seizure results in excessive motor or sensory activity
Due to connectivity this can spread within hemisphere or to opposite hemisphere
Why is crawling an important milestone in babies? What parts of the NS would be questioned if there were abnormalities?
Requires coordination of motor function between right and left sides of body
CNS or visuomotor may be questioned if this milestone is not hit
Describe the internal capsule.
Gathering of cortical projection fibers as they move between thalamus and deep cortical nuclei
Contains ascending (afferent) and descending (efferent) fibers, to and from cerebral cortex
How are fibers segregated in the brain?
Based on where they are projecting
What is the brainstem?
Stalk like part of the brain
Lower part is continuous with the spinal cord at the foramen magnum
Midbrain (uppermost), pons, medulla (lowest)
What is the function of white matter within the brainstem?
Tracts that transmit sensory and motor information
between the cerebrum and the rest of the brain/body
What is the function of gray matter within the brainstem?
Nuclei and functional centers associated with cranial
nerves
Other nuclei and functional centers
What is the function of reticular formation within the brainstem?
Network that integrates and control all activity associated with brainstem
Clusters of neurons that run through brainstem
Maintains arousal/sleep
What is a tract?
Pathways that conveys specific information from one place to another
Input/output
Can be overlapping
What are functional paths?
May contain axons of neurons
Axons usually for bundles called tracts, fasciculi or nerves
NS is composed or functional paths (with white and gray matter sections)
What cranial nerves are associated with the cerebrum?
1 and 2
What cranial nerves are connected to the brainstem?
3-12
How do cranial nerves work?
Can have one or more nuclei depending on function (motor, sensory, autonomic functions)
Receive descending info from higher areas (cortex)
Receives ascending info before relaying to cortex
Work together to carry out functions
What cranial nerve coordinate to allow eye movements in synchronous fashion?
CN 3, 4, 6
What is the cerebellum “little brain”?
Receives sensory info
Provides input to brainstem and cortical pathways
Key role in movement by regulating function of motor pathways (smooth, coordinated movements)
Describe the organization and structure of the cerebellar. What are cerebellar Peduncles?
White and gray matter
Extensive communication (tree like appearance)
Cerebellar penduncles are projection fibers that connect with brainstem
Describe the spinal cord.
Lowest part of CNS
Extends from medulla to neck and back
Begins at foramen magnum
Describe the function of spinal nerves.
Enable communication with all parts of body below the head
Peripheral projections
Afferent and efferent components
Describe ventral roots.
Anterior
Allow exit of efferent neurons from spinal cord
connects with dorsal root to form one spinal nerve
Describe dorsal roots.
Posterior
Allow afferent info to enter the spinal cord
connects with ventral roots to form one spinal nerve
What is a dermatome?
Sensory region of the skin innervates by a sensory nerve root
Can trace problems back to a specific spinal nerve
What is a myotome?
Muscles innervated by a single nerve root
Motor
Describe the internal structure of spinal nerves.
White matter- outer portion of axons
Gray matter- cell bodies and synapses
What are the regions of organization within the gray matter?
Posterior horn
Anterior horn
Lateral horns
Intermediate zones
