APBI 311 - Nervous System Flashcards
Basic Nervous System Constitutes: (2)
1) Neurons
2) Supporting Tissue
Define Neuron
a cyton or soma (nerve cell body) one or more nerve process.
Define “Processes” in terms of the nervous system.
Dendrites or dendrons conduct impulses toward the cell bodies; axons conduct impulses away from the cell bodies. Axis-cylinder processes, neur-axons or neurites.
Parts of a typical Neuron: (5)
1) Dendrites
2) Cell Body
3) Axon
4) Preseynaptic Terminal
5) Myelin (sometimes…. gaps between myelin are Node of Ranvier)
Define Synapse
A junction of the axon of one neuron with another neuron (neurons that are functioanally related).
Contact is axon to cell body or axon to dendrite.
Nuclei vs Ganglia
Nuclei are groups of cell bodies WITHIN CNS
Ganglia are group of cell bodies OUTSIDE of CNS
CNS constitutes of (2)
1) Brain
2) Spinal Cord
Fasciculi (or tracts) vs nerves
Fasciculi (or tracts) are bundles nerve processes WITHIN the CNS
Nerves are bundles of nerve processes OUTSIDE the CNS
Nervous System breaks off into: (2)
1) Central Nervous System (brain and spine)
2) Peripheral Nervous System (Cranial and spinal nerves)
CNS constituants (2)
1) Brain
2) Spinal Cord enclosed in vertebral column.
PNS breaks off to: (2)
1) Autonomic Nervous System (ANS) - Muscles and stuff
2) Somatic Portion (skeletal nerves)
ANS constituants (2)
1) Sympathetic Nervous System (thoraco-lumbar outflow)
2) Parasympathetic Nervous System (Cranio-sacral outflow)
Brain and Spinal Cord are: (2)
1) Located in the Dorsal Cavity
2) Protected by Cranial Skull, Vertebrae, and Dura Matter
Brain includes: (4)
1) Cerebrum
2) Cerebellum
3) Brain Stem
4) Four Ventricles filled with CSF
The Brain can be subdivided into: (3)
1) Forebrain
2) Midbrain
3) Hindbrain
Prosencephalon
Forebrain
1) Telencephalon
2) Diencephalon (next to mid brain)
Mesencephalon
Midbrain
Rhombencephalon
Hindbrain
1) Metencephalon
2) Myelencephalon
Telencephalon is part of (4)
1) Cerebral Cortex
2) Cerebrum
3) Corpus striatum
4) Rhinecephalon
in the Cerebral cortex the Telencephalon encloses (2)
1) Cavities of the lateral ventricles
2) Interventricular foramina of monro and the rostral protion of the 3rd Ventricle
Cerebrum form:
1) Two hemispheres of main brain with folds
2) Gray matter on the surface, white matter at centre
Cerebrum function (3)
1) Voluntary muscle control
2) Interpretation of sensations
3) Reasoning all involves cerebral cells
gyri vs sulci
1) gyri - ridges on the brain
2) sulci - furrows on the brain
Corpus striatum function
Connects each cerebral cortex with other parts of the CNS
Function of Rhinencephalon
Smell (olfactory brain)
Diencephalon contains: (5)
1) Thalamus
2) Epithalamus
3) Hypothalamus
4) 3rd Ventricle
5) Optic nerves enter.
Order of cephalon organization.
1) Prosencephalon (forebrain) - telencephalon, diencephalon
2) Mesencephalon (midbrain)
3) Rhombencephalon - Metencephalon, myelencephalon.
Thalamus function:
Relay center for never fibers connecting cerebral hemispheres to the brain stem and spinal cord.
Hypothalamus form:
incudes hypophysis or pituitary gland
Mesencephalon contains: (2)
1) Cerebral peduncles
2) 4 Quadrigeminal bodies
Cerebral Peduncles form:
Continuous of the spinal cord and the brain stem into the respective cerebral hemispheres.
Contains fiber tracts and nuclei
Quadrigeminal bodies (corpora quadrigeminal) Function (2)
1) Anterior - vision
2) Caudal - hearing
Rhombencephalon (hindbrain) constitutes of:
1) Metencephalon
2) Myelencephalon
3) 4th Ventricle
Metencephalon constitutes of:
1) Cerebellum
2) Pons
3) The 4th ventricle
Form of Cerebellum
1) Many folds (folia)
2) Two hemispheres
3) Vermis
4) Gray matter on surface and white matter at center
Function of Cerebellum
Coordination of voluntary movements
Form of pons
Bridge of fibers between hemispheres,
Other fiber tracts and nuclei.
Location of 4th ventricle
Between cerebellum and pons and brain stem
Myelencephalon constitutes
1) Medulla oblongata
2) Continuation of spinal cord
3) Brain stem
4) Cranial nerves III, IV, VII, IX, X, XI, XII, and V
5) Reflex centres
Parts of the brain stem
1) medulla
2) pons
3) midbrain
Reflex centers are for:
control of respiration and circulation
Ventricles are:
1) Chambers filled with cerebrospinal fluid (CSF)
2) Each has a choroids plexus
3) connected with subarachnoid pace of brain/spinal cord
Choroids plexus
network of capillaries
Hydrocephalus
fluid building up in skull causing brain swelling.
Meninges is:
covering of the brain and spinal cord
Layers of the Meninges (3)
1) Dura mater
2) Arachnoidea
3) Pia mater
Meningitis
inflammation of meningitis
Spinal cord is:
1) Medulla oblongata
2) Distinct segments - pairs of spinal nerves (usually one per vertebra)
3) Central gray matter of the spinal cord (gray horns) mainly cell bodies and their processes
Origin of sensory afferent fibers and efferent motor fibers
sensory afferent fibers - dorsal roots of the spinal nerves
Efferent motor fibers - to the ventral roots of the spinal nerves.
Tracts of the spinal cord (3)
1) Peripheral white matter - three column on each side
2) Dorsal white column - afferent tract - sense of position (proprioceptive
3) Lateral white column
4) Ventral white column
Columns on each side of peripheral white matter
1) Dorsal white column
2) Lateral white column
3) Ventral white column
Dorsal white column
1) Afferent tracts
2) Senses position (proprioreception)
Lateral white column
1) Dorsal ventral spinocerebellar - (senses co-ordination of movements)
2) Rubrospinal - from red nucleus in the midbrain to motor cells in the opposite side ventral grey horn.
3) Lateral Spinothalamic - fibers from the dorsal grey horn to the thalamus (detects pain and temperature)
4) Lateral Corticospinal - from motor area of the cerebral cortex to the ventral grey horn (voluntary movement)
Ventral white column
1) direct vestibulospinal tract - from the lateral vetibular nucleus to motor muscles (tone of muscle extensor
2) Crossed vestibulospinal tract - from descending vestibular nuclus to motro centers of the opposite side of the spinal cord
3) Ventral corticospinal (cerebrospinal) tract - connects motor area of the cerebral cortex with spinal cord (same and opposite sides) - impulses are associated with voluntary motor activities
Spinal Nerves function
1) Supply sensory and motor fibers to the regions of the body in the area where they emerge from the spinal cord
Plexus
supplies sensory and motor fibers to appendages
Branchial plexus (right and left)
1) Supplies nerves to for limbs.
2) Derived from C3 or C4 and T1 or T2
Lumbosacral Plexus (right and left)
1) Supplies hind limbs
2) Ventral branches of last few lumbar and S1,2 or 3 nerves.
Cranial Nerves:
1) 12 nerves
2) no dorsal or ventral roots
3) Emerge through various foramina of the skull
4) Some are strictly sensory (afferent) and some are mixed.
5) Cranial nerves are known by number (in approximate order rostral to caudal)
The 12 Cranial nerves are:
I - Olfactory II - Optic III - Occulomotore IV - Trochlear V - Trigeminal VI - Abducens VII - Facial VIII - Auditory (acoustic or vestibulocochlear) IX - Glossopharyngeal X - Vagus XI - Spinal accessory XII - Hypoglossal
Autonomic Nervous System
1) Visceral part of peripheral nervous system
2) Innervates the smooth muscle, cardiac muscle and glands
3) Visceral afferent and efferent fibers
4) Sympathetic/parasympathetic
5) Most autonomic efferent nerves synapse outside CNS.
Afferent nerves have
no cell bodies or synapses and exist outside the CNS
Sympathetic Nervous System
1) From thoracic and Lumbar Spinal Nerves
2) Efferent fibers from lateral gray column
3) Pre-ganglionic sympathetic neurons (myelinated)
4) Synapse with secondary neurons (post ganglionic neurons)
Parasympathetic Nervous System
1) CNIII - occulomotor
2) CNVII - facial
3) CNIX - glossopharyngeal
4) CNX - vagus - heart lungs, almost all viscera
5) Sacral spinal nerves - digestive and most urogenital.
Inclusions
Nissl Bodies (dark staining granules of RER).
Classes of Neurons (2)
1) Pseudo Unipolar Neurons
2) Bipolar neurons (smell, sight, and balance)
3) Multipolar
Pseudo Unipolar Neurons
Looks like two dendritic ends, but really just one big dendrite.
Bipolar Neurons (smell, sight, and balance)
One dendrite and one axon.
Multipolar Neurons
Several Dendrites but USUALLY only one axon.
Dendrites
Short protoplasmic process that branches repeatedly.
Axon
Long process, collateral branches along its course, profuse branching (telodendria) at terminal end as it does main axon.
Motor Unit
Motor nerve each terminal branch supplies a single muscle fiber.
Myelinated (white) nerve fibers
1) White
2) Sheath of fatty material - (many schwann cells - neurolemmocyte) wrapped around nerve fiber.
Unmyelinated nerve fibers
1) Grey
2) Surrounded (not wrapped) by ONE LAYER of Schwann Cell.
Function of neurons:
1) Perception of changes in ext. environment.
2) Perception of changes in int. environment.
3) Ability to adapt to these changes.
Resting potential of a membrane is:
1) Electrical different between negative charges inside the membrane and positive changes outside membrane.
2) Produced by difference in ions (sodium and potassium and chlorides).
3) Unequal distribution of charges produces a measurable voltage difference across the membrane (this is the membrane potential)
Membrane Potential
1) Unequal distribution of charges produces a measurable voltage difference across the membrane.
2) Varies from cell to cell.
Action Potentials
Results from reversal of polarity on the plasma membrane created by an adequate stimulus, a stimulus capable of significantly increasing membrane permeable Na+.
Stimulus
Any changes in the environment of a nerve which can depolarize resting potential.
Threshold Stimulus
when stimulus is just enough to initiate action potential and therefore an impulse
Depolarization
Rapid increase in the membrane permeability to Na+.
Repolarization
Getting back to original state.
Conductance
Overall process of action potential, depolarization and depolarization depends on the changes in the membrane conductance of Na+ & K+.
The Nerve Impulse
1) Is the propagation of action potential.
2) Usually proceeds only in one direction.
Cunductance Velocities
1) Speed of conduction of an impulse remains constant
2) Vary in speed
3) Myelinated fibers conduct impulses more rapidly than unmyelinated nerver fibers.
Neuronal Synapse:
1) Electrochemical transmission site
2) Usually a specialized junction between two neurons.
3) Presynaptic and post synaptic
4) Excitatory or inhibitory.
5) Transmitting substances
Presynaptic neurons
Conduct impulses towards the synapse.
Postsynaptic neurons
1) Conducts impulse away from the synapse.
2) Excitatory synapse or inhibitory synapse changes excitability.
Neurotransmitters
1) Acetylcholine
2) Norepinephrine
3) Dopamine
4) Seratonin (stimulatory)
5) Glycine
6) Gamma-aminobutyric acid (GABA).
Type I Synapse
Axodendritic - Axon to dendritic.
Type II Synapse
Axosomatic - Axon to cell body.
Factors affecting transmission
1) Synaptic junction is weakest link in the neuron chain.
2) Many drugs act at synapse.
3) pH or oxygen concentration affecting transmission.
Drugs that affect synapse:
1) Morphine
2) Strychnine
3) Tranquilizer
Alkalosis
1) Increase pH of body fluids.
2) Neuron excitability increases.
Acidosis
1) Decrease pH of body fluids.
2) Neuron excitability decreases.
Decreased oxygen in body fluids influences excitability of neurons…
Decreased excitability of neurons.
Reflexes
Autonomic or unconscious response of an effector organ to an appropriate stimulus.
Reflex Arc
1) Afferent, sensory or receptor neurons.
2) Efferent, motor or effector neurons.
3) Usually one or more connector neurons.
Spinal Reflex
Stretch reflex
Visual Reflex
Production of salivary & gastric secretion by a dog when it sees the food.
Conditioned reflex
let down of milk.
Reflex Centers
1) Located through out the CNS: Spinal cord - less complex.
2) More complex reflexes found in brain.
3) Medulla oblongata
4) Cerebelum.
Medulla oblongata control - in terms of reflexes
1) Control of heart action
2) Respiration
3) Swallowing
4) Vomitting
5) Coughing
6) Sneezing
Cerebellum - in terms of reflexes
1) Locomotion
2) Posture
Role of ANS:
1) Maintain a relatively stable internal body environment
2) Regulating muscles and glands.
3) Activation can occur either by cerebrocortical input or other afferent input to hypothalamus.
Hypothalamus sections that integrate of ANS
1) Caudal part integrate sympathetic division
2) Rostal part integrate parasympathetic division.
3) Fight/Fright activity - sympathetic
4) Relaxed vegetative activity - parasympathetic.
Chemical Transmitters
1) Post ganglionic sympathetic - Norepinephrine
2) All Other - Acetlycholine
Pathology of nervous system
1) Death of nerve cells - may be serious because nerve cells can’t be replace
2) Injuring to nerve process - peripheral nerves may or may not be permanent.
3) Peripheral nerve injuries results in loss of sensation and/or muscle activity
4) CNS damage is very serious.
Sympathetic nervous system
Fright or flight activity
Parasympathetic nervous system
Relaxed and vegetative activity
