lecture exam 4 Flashcards
: made up of the brain and the spinal cord
Central nervous system (CNS)
: made up of the neural tissue outside of the CNS
Peripheral nervous system (PNS)
location of cranial nerves
coming off the brain
location of spinal nerves
coming off the spinal cord
carrying nerve impulses from the sensory receptors to the central nervous system
Afferent division:
carrying nerve impulses from the central nervous system to muscles, visceral organs, and glands
Efferent division:
cells that transmit nervous impulses
Neurons:
highly branched processes which carry nervous impulses toward the cell body
Dendrites:
long cytoplasmic process which carries nervous impulses away from the cell body
Axon:
end of an axon which interacts with another cell at the synapse
Synaptic terminal (aka, synaptic knob, axon terminal):
junction between a neuron and another cell
Synapse:
has one long axon and only one dendrite, positioned at opposite ends of the cell body; occurs in special sense organs
Bipolar:
appears to have one process which bifurcates into an axon and a single dendrite; most sensory neurons are unipolar
Unipolar (aka, pseudounipolar):
` has one long axon and many dendrites; most common type of neuron in the CNS
Multipolar:
small, with a short axon not easily distinguished from the dendrites; primarily found in the brain and in special sense organs
Anaxonic:
the 4 types of neuronal classification are
bipolar, unipolar, multipolar, anaxonic
cells of the afferent division of the peripheral nervous system
Sensory neurons:
cells of the efferent division of the peripheral nervous system
Motor neurons:
may act as connectors between sensory and motor neurons; located entirely within the central nervous system
Interneurons (aka, association) neurons:
support cells of the nervous system
Neuroglia:
epithelial cells, lining the ventricles of the brain and the central canal of the spinal cord; some specialized ependymal cells secrete cerebrospinal fluid (CSF)
Ependymal cell:
support cell for neurons in the central nervous system; a component of the ‘blood-brain barrier’
Astrocyte:
the ‘immune system’ cells of the central nervous system
Microglia:
processes wrap around axons and dendrites of the central nervous system, insulating them
Oligodendrocyte:
a multi-layered membranous covering; increases the speed of action potential propagation along the axon
Myelin:
ependymal cell, astrocyte, microglia, oligodendrocyte, and myelin are located within the ______ _______ _______
central nervous system
surround and provide support for neuron cell bodies within a ganglion
Satellite cells:
a cluster of neuron cell bodies
Ganglion:
myelinate axons and dendrites of the peripheral nervous system
Schwann cells:
satellite cells, ganglion, and schwann cells are located where?
within the peripheral nervous system
- Uneven distribution of cations on either side of the cell membrane
- Inner surface of cell membrane is more negatively charged than the outer surface; the membrane is said to be ‘polarized’
- Resting potential = -70mV
Resting potential of the cell membrane of a neuron
(resting potential becomes more negative)
Hyperpolarizing
(resting potential becomes less negative)
depolarizing
amount of change in membrane potential is directly proportional to the size of the stimulus
Graded potential:
local changes in membrane potential can be additive if they occur close together in time or space
Summation:
membrane potential at which sodium-channels open, allowing sodium ions to readily enter the cell; depolarization to -60 to -55mV (for neurons)
Threshold potential:
wave of depolarization that is propagated across an entire cell membrane
Action potential (aka, nervous impulse):
the properties of the action potential are independent of the relative strength of the depolarizing stimulus as long as that stimulus exceeds the threshold potential
The All-or-None Principle:
Generation of an action potential
a. Depolarization of the membrane to threshold potential
b. Activation of the sodium channels, allowing sodium ions to enter the cell; cell membrane depolarizes entirely
c. Sodium channels close and potassium channels reopen, causing the membrane to repolarize
d. Resting potential is re-established and normal ion permeability is restored
junction between a neuron and another cell
The synapse:
transmission of neural impulse from one cell to another
Synaptic transmission:
______ ________ of the synaptic terminal releases neurotransmitters into the synaptic cleft
Presynaptic membrane
space between the two cells
Synaptic cleft:
________ diffuses across the synaptic cleft and binds to _______ within the postsynaptic membrane
Neurotransmitter, receptors
Postsynaptic membrane may become _______, generating propagation of an action potential in the _______ ______
depolarized, postsynaptic membrane
Postsynaptic membrane may become ________, inhibiting propagation of an action potential in the _______ ______
hyperpolarized, postsynaptic membrane
The effect of a________ on the postsynaptic membrane depends on the _______ __ ___ _______, not on the nature of the neurotransmitter
neurotransmitter, properties of the receptor
Modification of the sarcolemma into the______ -____ -_____
‘motor end plate’
made up of a single motor neuron and those muscle fibers controlled by it
The motor unit:
autoimmune disease causing muscle weakness
Myasthenia gravis:
neurotoxin prevents muscle contraction, by preventing release of neurotransmitter from the motor neuron
Botulism:
neurotoxin causes excessive stimulation of target muscle, which results in severe muscle spasms and sustained muscle contractions
Tetanus:
clinical considerations with neural tissue are?
myasthenia gravis, botulism, and tetanus
center of conscious thought
Cerebrum:
(composed of ‘gray matter’; i.e., mostly neuron cell bodies)
cerebral cortex
located in the frontal lobe, just in front of the central sulcus (i.e., the pre-central gyrus)
Motor cortex,
, located in the parietal lobe, just behind the central sulcus (i.e., the post-central gyrus)
Sensory cortex
located throughout the cerebral cortex
Association and integration areas,
(composed primarily of myelinated axons)
Central white matter
(clusters of gray matter embedded within the central white matter)
Centers for subconscious motor control
Cerebral nuclei
Diencephalon, containing the _____ and ______
thalamus, hypothalamus
_______ located on either side of the third ventricle
Thalamus,
what does the thalamus do?
Relays and filters sensory information ascending from the spinal cord to the cerebral nuclei and cerebral cortex
lying below the thalamus and making up the lower walls and floor of the third ventricle
- Contains important control and integrative centers (i.e., control of autonomic functions, of skeletal muscle contractions, coordination of nervous and endocrine systems, regulation of homeostasis)
- Production of emotions and behavioral drives
Hypothalamus,
the ‘primitive’ or ‘emotional’ brain
- Functional unit, composed of elements along the boundary between the cerebrum, diencephalon, and mesencephalon
- Controls emotional experience and expression
Limbic system:
joins lower parts of the brain stem and spinal cord to the diencephalon and cerebrum
A. Includes several masses of gray matter which serve as reflex centers (e.g., visual and auditory reflexes)
B. Contains bundles of sensory nerve fibers ascending to the thalamus and bundles of motor fibers descending from the motor cortex
Mesencephalon (aka, midbrain):
A. Composed of an outer cortex of gray matter, an inner area of white matter, and deep clusters of gray matter (i.e., cerebellar nuclei)
B. Coordinates automatic adjustment of skeletal muscles to maintain posture
C. Fine-tuning of learned motor patterns
D. Connected to all other parts of the brain
Cerebellum
A. Links the cerebellum to the mesencephalon, cerebrum, and spinal cord
B. Contains nuclei for cranial nerves V (Trigeminal) through VIII (Vestibulocochlear)
C. Contains nuclei dealing with control of respiration
Pons
` an enlarged continuation of the spinal cord, extending from the foramen magnum to the pons
A. Relay for all sensory and motor nerve tracts
B. Contains nuclei associated with autonomic control of visceral activities (e.g., cardiovascular centers, respiratory rhymicity centers)
C. Contains nuclei for cranial nerves VIII (vestibulocochlear) through XII (hypoglossal)
Medulla oblongata:
the meninges
Coverings of the brain:
- Dural folds: falx cerebri, falx cerebelli, tentorium cerebelli
Dura mater
- Subarachnoid space and the circulation of cerebrospinal fluid (CFS)
Arachnoid mater
fused to the outside surface of the brain
Pia mater:
contains cell bodies of somatic and visceral sensory neurons
Posterior gray horn:
contains cell bodies of somatic motor neurons
Anterior gray horn:
contains cell bodies of visceral motor neurons
Lateral gray horn:
White matter divided into three regions:
anterior, posterior, and lateral columns (aka, funiculi [pl.]; funiculus [sing.])
carry sensory information to the brain
Ascending tracts:
carry motor commands out to the periphery
Descending tracts:
Fiber characteristics within a tract
a. All fibers carry information in the same direction
b. All fibers have similar diameter and degree of myelination; therefore, conduction speed is similar
c. All fibers have similar place of origin
d. Fibers may have different destinations
nerve roots
ventral root (efferent fibers), dorsal root (afferent fibers), and dorsal root (housing sensory neuron body cells)
Coverings of the spinal cord:
the meninges
- Dura mater
a. Epidural space - Arachnoid mater
a. Subarachnoid space and the circulation of cerebrospinal fluid (CFS) - Pia mater: fused to the outside surface of the spinal cord
Covering of the spinal cord
spinal nerve coverings
endoneurium, perineurium, epineurium
surrounds each individual fiber (i.e, neuronal axon or dendrite) of the peripheral nervous system
Endoneurium:
surrounds a fascicle (i.e., a bundle of nerve fibers)
Perineurium:
surrounds a peripheral nerve (i.e., a bundle of fascicles)
Epineurium:
pathways of a typical spinal nerve
dorsal primary ramus, ventral primary ramus
sensory and motor innervation to skin and muscles near the spinal column
Dorsal primary ramus:
sensory and motor innervation to the rest of the body
a. Spinal plexuses (cervical, brachial, and lumbosacral)
Ventral primary ramus:
Rami communicantes
a. White ramus
b. Gray ramus
Autonomic Nervous System (ANS)
A. Differences from the Somatic Nervous System
- Always has two motor neurons in the pathway, from the central nervous system to the target organ
- Innervates smooth muscle, cardiac muscle, glandular tissue
Subdivisions of the autonomic nervous system
Sympathetic division:
Parasympathetic division:
in general, prepares the body for ‘fight or flight’
Sympathetic division:
_______ _______ originate in the thoracolumbar region (in the lateral gray horn of ___ __ __)
Preganglionic neurons,
T1-L2
Postganglionic neurons originate in three different places
. Sympathetic chain ganglia (aka, para-vertebral ganglia), reaching from the cervical region down to the sacral region
ii. Collateral ganglia (aka, prevertebral ganglia), located anterior to the vertebral bodies
iii. Adrenal medulla
: in general, prepares the body for ‘rest and repose’ (aka, ‘feed and breed’)
Parasympathetic division
Preganglionic neurons originate in the brain stem (as components of __ ___[oculomotor],___ [facial], __[glossopharyngeal], and __ [vagus]) and in the sacral segments of the spinal cord (in the lateral gray horn of S2-S4)
CN III , VII, IX, X,
_______ ________ occur in peripheral ganglia located ______ -___ ____ to the target organ
Postganglionic neurons,
within or adjacent
Most vital organs receive_______ _______
dual innervation
Dual innervation usually takes place as ______ ________
opposing effects
Some organs receive innervation from _____ ___ ______
only one system
sensory receptor responds only to a specific type of stimulus
Specificity:
the area monitored by a single receptor cell
Receptive field:
sensory receptor adjusts to a continuous sensory stimulus over time
Sensory adaptation:
process by which the brain causes a sensation to be perceived as originating at the point of stimulation
Projection:
Classification by stimulus location
- Exteroceptors
2. Interoceptors
respond to mechanical deformation of the nerve receptor
Mechanoreceptors:
respond to [potential] damage to the receptor
Pain receptors (aka, nociceptors):
respond to temperature stimuli
Thermoreceptors:
respond to chemical stimuli
Chemoreceptors:
respond to light stimuli
Photoreceptors:
touch, pressure, vibration (e.g., Meissner’s and Pacinian corpuscles [aka, corpuscle of touch and lamellated corpuscle, respectively])
Tactile receptors:
changes in pressures within a distensible organ (e.g., within a blood vessel wall)
Baroreceptors:
monitor position/location of joints and muscles; stimulus sent to cerebellum and parietal lobe of cerebrum
Proprioceptors:
- Free nerve endings with a large receptive field
- Respond to damage or extreme deformation of the receptor ending; do not adapt
- Stimulus travels to the thalamus, and then to the cerebral cortex (parietal lobe)
Pain receptors
- Cold vs. hot receptors
- Active during changing temperatures but quickly adapt to a stable temperature
- Stimulus travels to parietal lobe of cerebrum
Thermoreceptors
detect changes in the concentration of specific chemical compounds (e.g., the carotid body monitors the concentration of CO2 and O2 in the blood)
- Sensory input goes to the brain stem, not to the cerebral cortex
- Responds to water- and lipid-soluble substances dissolved in the surrounding fluid
Chemoreceptors:
the sense of smell
- Olfactory receptor cells: chemoreceptors located within the olfactory epithelium; adapt quickly
- Receptor cells synapse with neurons within the olfactory bulbs (Cranial Nerve I)
- Extensive limbic and hypothalamic connections (potential for significant emotional and behavioral responses); then passed on to the olfactory cortex (temporal lobe of the cerebrum)
Olfaction
- Chemoreceptors housed in the taste buds located on the tongue and on the walls of the pharynx
a. Synapse with sensory fibers of cranial nerves VII (facial), IX (glossopharyngeal), and X (vagus)
b. Impulses end up in the cortex of the parietal and temporal lobes of the cerebrum
c. Taste sensations supplemented by input from olfactory receptors - Primary taste sensations: sweet, sour, salt, bitter, umami (aka., ‘savory’); water and ‘metallic’ have also been suggested
Gustation: the sense of taste
composed of the sclera and the cornea
Fibrous tunic:
composed of the choroid layer, iris, pupil, and ciliary body
Vascular tunic:
` composed of the pigmented layer and the neural laye
Neural tunic [aka, retina]:
Placement of the lens divides the eyeball into two spaces: a large _____ _____ (filled with vitreous humor) and a smaller ______ ______ (filled with aqueous humor)
posterior cavity
anterior cavity
Photoreceptors housed in the _______
retina
for visual acuity in dim light; distributed in a broad band on the periphery of the retina
Rods:
for color vision; distributed along the posterior retinal surface, concentrated in the fovea centralis of the macula lutea
Cones:
Light activates visual _____ contained in _____ in the outer segment of the ____ ___ ______
pigments,
discs,
rods and cones
Rods and cones synapse with ____ _____, which in turn synapse with ________ ____
bipolar cells
ganglion cells
_______ ___ ________ cells provide interconnections between different parts of the retina
Horizontal and amacrine
_______ _____ ________ _______ converge on the optic disc to form the optic nerve (Cranial Nerve II
Axons from the ganglion cells
_______ ______ synapses with ______ within both sides of the __________, which then proceed to the visual cortex of the occipital lobe of ___ _________ _________ (producing stereoscopic vision)
Optic nerve
neurons
diencephalon
the cerebral hemispheres
large overlap between right and left visual fields
Binocular vision:
Focusing of the image on the retina is accomplished by ______ ____ ___ ____ (i.e., ‘accommodation’)
changing the shape of the lens
a. Relaxation of the ciliary muscles causes the lens to _______ ____
flatten out
Contraction of the ciliary muscles causes the lens to be _____ _______
more spherical
auricle (aka, pinna) and the external auditory canal
External ear:
tympanic membrane, auditory ossicles (malleus [aka, hammer], incus [anvil], stapes [stirrup]), pharyngotympanic tube (aka, auditory or Eustachian tube)
Middle ear:
a hollow bony labyrinth, divided into three semicircular canals, the vestibule, and the cochlea
Inner ear:
(aka, scala tympani and scala vestibule, respectively), containing perilymph; connected at the tip of the cochlear spiral
Tympanic and vestibular ducts
(aka, scala media), containing endolymph and the Organ of Corti
Cochlear duct
hair cells (mechanoreceptors) which rest on the basilar membrane and contact the overlying tectorial membrane
Organ of Corti:
i. Sound waves arrive at the tympanic membrane
ii. Movement of the tympanic membrane causes displacement of the auditory ossicles
iii. Movement of the stapes at the oval window establishes pressure waves in the perilymph of the vestibular duct
iv. The pressure waves distort the basilar membrane on their way to the round window of the tympanic duct
v. Vibration of the basilar membrane causes vibration of hair cells against the tectorial membrane, generating a nervous impulse
vi. Information about the region and intensity of stimulation is relayed to the medulla oblongata over the cochlear branch of the vestibulocochlear nerve (CN VIII)
vii. Auditory signals proceed from the medulla oblongata to the mesencephalon, then to the thalamus and finally to the auditory cortex in the temporal lobe of the cerebrum
The hearing process
: the sense of balance
Equilibrium
_____________ in the semicircular canals respond to rotational movement of the head
Mechanoreceptors
____ _____ within the ______ respond to movement of the surrounding ________
Hair cells / ampulla / endolymph
Mechanoreceptors in the ______ and _____ (located within the vestibule) provide positional information even when the head is stationary
utricle/ saccule
Hair cells are clustered in a _____, covered by a thin layer of _____ (densely packed calcium carbonate crystals)
macula/ otoliths
Gravitational pull on the ______ deforms the hair cells in specific ways, registering whether the head is level or tilted
otoliths
______ _____ of the vestibule and _______ _____ synapse with fibers of the vestibular branch of the _______ ________(CN VIII); nervous signal is relayed to the vestibular nuclei at the boundary of the _______ _______ and ________
Hair cells / semicircular canals/ vestibulocochlear nerve / medulla oblongata/ and pons
Signals proceed from the ________ _______ to the cerebellum, _______ _______, and to _____ ______ in the brain stem and spinal cord controlling eye, _____, and ____ movements
vestibular nuclei/ cerebral cortex/ motor nuclei / head/ neck
