Unit 2 Sensory and Integrative Nervous System Flashcards
Transduction
the conversion of stimulus energy into an electrical signal
Adaptation
decreased sensitivity to continuous stimuli
tonic receptors
adapt slowly if at all; pain is sensed with tonic receptors; when the stimulus is applied, the receptor potential is on; when the stimulus is removed, the recereceptor potential is off
phasic receptors
adapt quickly; touch is sensed with phasic receptors; when the stimulus is applied, the receptor potential signals at the beginning; when the stimulus is removed, the receptor potential signals at the
Modality-
correctly interpreting electrical signals in the brain; what is perceived has to do with the part of the brain that is stimulated; the brain knows what is sensed based on the location of the signal
Intensity-
stronger stimuli elicit stronger responses
frequency coding-
more frequent action potentials on a given sensory neuron
population coding-
more receptors activated/more sensory neurons recruited
exteroreceptors-
sense the external environment
enteroreceptors-
sense the internal environment
proprioreceptors-
sense the relationship between self and the environment
photoreceptors-
detect light
chemoreceptors-
detect chemicals
mechanoreceptors-
detect pressure, movement, sound to name a few
thermoreceptors-
detect temperature
cutaneous senses-
detect touch/pressure, cold, warmth, pain
visceral senses-
sense the internal environment; chemicals, pain, temperature, pressure
special senses-
vision, smell, taste, hearing, rotational/linear acceleration (balance)
Cutaneous Senses
Touch, pain, cold, and warmth are sensed with naked nerve endings. All are histologically identical but physiologically distinct.
naked nerve ending-
can be positioned between skin cells or wrapped around the base of hairs
expanded tips on nerve endings-
Ruffini endings, Merkel’s disks; slowly adapting (tonic)
encapsulated endings
- cells ore extracellular material surrounding the receptor; Meissner’s corpuscles, Pacinian corpuscles, Krause’s corpuscles; rapidly adapting (phasic)
In Pacinian corpuscles
mechanical distortion causes the opening of Na+ channels. Stronger stimuli open more channels and recruit more receptors.
In Pacinian corpuscles
mechanical distortion causes the opening of Na+ channels. Stronger stimuli open more channels and recruit more receptors.
Touch receptors are most abundant on the fingers and lips but are scarce on
the trunk
Two major types of pain
Fast Pain and Slow Pain
Fast Pain
felt within 0.1 sec of stimulus
sharp, localized sensation immediately after stimulus
mostly cutaneous; cut, burn, electric shock
felt as sharp, prickling, acute, electric pain
Slow Pain
felt after 1 sec or more or stimulus
dull, intense, diffuse, unpleasant feeling (after initial wave of pain)
“can lead to prolonged, unbearable suffering” (from text)
can be cutaneous or visceral; tissue destruction
felt as slow burning, aching, throbbing, nauseous, chronic pain
There are three types of stimuli
mechanical, thermal, and chemical
Fast pain results from
mechanical and thermal pain, while all three types of stimuli cause slow pain.
Chemical pain is the result of
substances often released by damaged cells exciting receptors. Examples of these substances are bradykinin, serotonin, histamine, K+, H+, acetylcholine, and proteolytic enzymes.
Pain receptors do no adapt but instead
exhibit progressive increased sensitivity called hyperalgesia, especially with slow pain.
Prostaglandins and substance P function
nhance pain receptor sensitivity.
Aspirin inhibits
prostaglandins, which is part of its analgesic effect.
There are two types of temperature receptors
cold and warm
Cold receptors response range
8 to 43C
warm receptors response range
30 to 50C
adaptation temperature range
20 to 40 C
Normal Body Temperature
37 C
Tissue damage occurs and cold/warmth becomes pain at what temperatures
below 8C and above 50C
Temperature center in the body
Hypothalamus
Visceral pain is often referred to as a
somatic structure (ex. Heart pain is felt in the Left arm)
Common Visceral Receptors
Stretch and chemical receptors
baroreceptors-
walls of great elastic arteries, which are responsible for short-term regulation of blood pressure (Stretch Receptor)
walls of atria-
responsible for long term regulation of blood pressure (Stretch receptor)
alveoli of lungs-
Herring-Breuer Reflex to regulate respirations; this isn’t that important in humans (Stretch Receptor)
stomach-
gastrocholic reflex; causes contractions in the large intestine and regulates hunger (Stretch receptor)
colon-
primary stimulus for defecation (Stretch Receptor)
urinary bladder-
primary stimulus for urination (Stretch Receptor)
arterial PO2 (Chemoreceptor)-
walls of great elastic arteries; limited importance
H+/CO2 in medulla oblongata (Chemoreceptor)
pH of cerebrospinal fluid; important for regulation of respiration
osmotic pressure of plasma (Chemoreceptor)-
hypothalamus; water and salt balance
arteriovenous blood differences in glucose (Chemoreceptor)-
hypothalamus; regulates appetite
protein/lipid/H+ in small intestine (Chemoreceptor)-
enterogastric reflex; regulates stomach activity
NUmber of taste buds and location
10,000 taste buds on the upper surface of the tongue in fungiform and vallate papillae.
Fungifom Papillae are found
on the tip of the tongue , and there are
Vallate Papillae are found
at the back of the tongue, and there are ≤100 taste buds per papillae
Taste receptors are modified
Epithelial cells
In each taste bud, there are ___receptor cells and supporting cells that will become receptors. They are arranged like slices of an orange in the taste bud.
50
Microvilli from receptor cells are sticking out of the taste pore and in contact with mucous in which
food particles are dissolved.
five taste modalities:
bitter, sweet, sour, salt, and umami
Umami
Japanese for delicous, the associated chemical is L-Glutamate which is a savory taste (meat, aging cheese, soy)
Perceived taste depends on
the combination and degree of receptors stimualted similar to perception of color
Taste Blindness Chemical
phenyl-thiocarbamide
Frequency of Taste Blindness
15-30% of people can’t taste this chemical (phenyl-thiocarbamide)
Sour Taste Threshold (HCl)
0.0009 M
Salt Taste Threshold (NaCl)
0.01 M
Sweet Taste Threshold (Sucrose)
0.01 M
Bitter Taste Threshold (Quinine)
0.000008 M
Bitter may be a warning of
Dangerous chemicals since many toxins are bitter. The lowest threshold is for bitter and most are alkaloids and long-chain organics containing nitrogen
50% of taste adaptation occurs in the
Central nervous system
Sensory neurons for the anterior 2/3 of the tongue travel in
Cranial Nerve VII (facial nerve)
neurons for the posterior 1/3 of the tongue travel in
Cranial Nerve IX (glossopharyngeal nerve
Cells involved in smell
Olfactory Cells
Sustenacular Cells
Bowman’s Glands
Bowman’s Glands function
Mucous secretion
Olfactory cells
receptors; humans have about 100,000,000; neurons are replaced every 1-2 months (the only neurons in the human body that divide)
Sustenacular Cells
receptor precursors
Process of Smell
odorants bind to cilia of olfactory cells . The olfactory cells depolarize in response to the odorants. Olfactory cells penetrate the ethmoid bone and synapse at the olfactory bulb. The Olfactory Nerve (Cranial Nerve I) carries signals from there to the cerebrum and limbic systems
Ear is divided into three parts:
Inner, Middle, Outer
Outer and middle ear are
air-filled tunnels that direct and amplify sound waves
The inner ear
is fluid-filled and is the location of receptors for hearing and equilibrium
The outer ear consists of
Pinna, ear canal, and ear drum (tympanic membrane). The eardrum vibrates when struck with sound waves
Middle Ear
Cavity between the eardrum and the inner ear. It opens into the nasopharynx via eustachian tube. The tube is normally closed, but opening allows for pressure equalization
The main function of the middle ear
Transmit sound waves as vibrations to the inner ear
Three bones in the middle ear
Malleus, incus, and stapes
Malleus is next to the eardrum, the stapes is attached to the oval window (Beginning of inner ear), and the incus is between the malleus and the stapes.
Vibrations on the eardrum move the bones which result in vibrations on the oval window
with 20x amplification and faithful frequency
Inner ear modalities
Hearing and equilibrium
Hearing is detected with the
cochlea, which is innervated by the auditory nerve
Equilibrium is detected by the
vestibular apparatus, which is innervated by the vestibular nerve.
The auditory and vestibular nerves join to form the
Vestibulocochlear nerve (CN VIII), Sensory only
CN VIII
Vestibulocochlear nerve is routed through the medulla, then thalamus, and finally the auditory cortex of the cerebrum. Receptors in both modalities are hair cells, which are irreplaceable.
scala vestibuli
upper chamber filled with perilymph, connected to the oval window, communicates with the scala tympani via helicotrema
scala tympani-
lower chamber filled with perilymph, connected to the round window
scala media-
middle chamber filled with endolymph
Inner ear
Contains a canal within a canal. Outer canal is bony labrynth , channels within the temporal bone that are filled with fluid called perilymph.
Outer Canal of the inner ear
Outer canal is bony labrynth , channels within the temporal bone that are filled with fluid called perilymph.
Inner canal of the inner ear
is the membraneous labyrinth, channels with more or less the same shape as the bony labyrinth and filled with fluid called endolymph
Does communication exist between the endolymph and perilymph?
No. The two labyrinths divide the cochlea into three chambers:
Three chambers of the Cochlea
Scala Vestibuli
Scala Tympani
Scala Media
Organ of Corti
is found along the length of the floor of the scala media, making up the basilar membrane. Hair cells are found here, which are the sound receptors
Membrane covering the hair cells
tectorial membrane
Reissner’s membrane
Roof of the scala media/floor of scala vestibu
Endolymph is located between
the tectorial and Reissner’s membranes
Steps of sound detection
Sound waves funneled through the outer ear hit the eardrum, which vibrate the middle ear bones. The stapes hits the oval window causing the perilymph to vibrate
Reisner’s Membrane role in sound detection
causes endolymph to vibrate; moves the tectorial membrane causing hair cells to move. The mechanical deformation of hairs opens and closes K+ and Ca++ gates causing alternating depolarizing and hyperpolarizing graded potentials.
Round window Role in sound detection
bulging of window dissipates sound waves
Inner hair cells in sound detection
Sound waves cause a mechanical bend of inner hair cells that results in a graded potential. A sensory neurotransmitter, possible glutamate but still unclear, is released by the hair cell and binds to the next neuron in line
Outer Hair cells in sound detection
they receive input from motor neurons. Outer hair cells frantically bound up and down if sounds are loud (high amplitude), possibly to enhance the response to inner hair cells.
Sound Pitch
depends on frequency
seven notes
human ears can detect 20-20,000 Hz
120 Hz is the frequency of the average male’s voice, 250 Hz is the frequency of the average female’s voice
intensity-
depends on amplitude; loudness
measure in decibels (DB), which is a log scale
jet plane = 160 DB
threshold of human hearing = 0.0002 DB
normal conversation = 60 DB
sounds ≥100 DB are dangerous
threshold of hearing moves the basilar membrane a fraction of a diameter of an H atom
Frequency discrimination depends on
where waves hit High frequency hits early, low frequency hits late = place principle
Amplitude discrimination depends on
how much of the hair on a hair cell is bent. Loud sounds bend the hair more
Two types of deadfness
Conduction deafness and Nerve Deafness
Conduction Deafness-
sound waves are poorly conducted to the Organ of Corti. This can be caused by a blocked ear canal, ruptured eardrum, fluid buildup in eustachian tube, problems with middle ear bones, and damage to oval window. Common treatments are hearing aides and tubes to drain the ears.
Nerve Deafness-
sound waves in the inner ear are not transduced to action potentials. This can be caused by damage to the Organ of Corti, damage to the auditory nerve, damage to the auditory cortex of the brain, and excessive exposure to loud noises which kills hair cells. A common treatment is cochlear implants.
Embryonically and morphologically the structures of the eye are derived from
The central nervous system
The most complex sense organ
The eye
Sclera
tough outer layer that makes up the white of the eye
Made from connective tissue
cornea-
transparent portion of sclera that covers the iris and pupi
choroid-
next layer of the eye inside the sclera
Highly vascularized
Feeds the retina
retina-
found on the back of the eye
Retina is made of
nervous tissue; photoreceptors and sensory neurons
fovea centralis-
center of field of vision; loaded with conestext annotation indicator
optic disk-
no photoreceptors because all sensory neurons converge to form the root of the optic nerve (Cranial Nerve II); also called the blind spot
Lens-
proteinaceous, transparent structure behind the iris
Focuses light on the retina
associated with suspensory ligaments and ciliary muscles to change the shape of the lens for focusing on images
cataracts
cloudiness in the lens, occur when proteins in the lens are denatured
iris-
pigmented cells above the lens
layers of circular and longitudinal muscles that constrict or dilate to control the amount of light entering the eye
pupil-
opening in the middle of the iris that allows light to enter the eye
Humors of the eye
aqueous humor and Vitreous humor
aqueous Humor
fluid between the lens and the cornea; produced by the ciliary body (modified choroid); drained through the canal of Schlemm; blocking the canal causes glaucoma, which is an increase in intraocular pressure due to buildup of aqueous humor
vitreous humor-
clear gelatinous material between lens and retina
Focusing on light types
Far objects and near objects
Focusing on far objects
pupil is dilated to let in light; longitudinal muscles contracted
lens is thin; ciliary muscles relaxed and suspensory ligaments taut
Focusing on Near objects
pupil constricted to minimize light entry; circular muscles contracted
lens is thick; ciliary muscles contracted and suspensory ligaments relaxed
Properties of light
Light resembles sound except frequencies are much higher. Light waves are measured in nm (1 m = 109 nm). Human eyes are sensitive to wavelengths between 400-700 nm. 400 nm = 7.52 X 1014 cycles/sec. Refer to Figure 50-8 to see the various wavelengths of light.
Retina
the pigmented layer of the eye. It is black and absorbs light not directly striking photoreceptors. This is why pupils are black.
Two types of photoreceptors in the eye
Rods and Cones
Rods
detect light intensity or black and white vision
extremely sensitive to light but are unable to discriminate frequency
most numerous on the periphery of the retina
Cones
detect color in the form of wavelengths
not very sensitive to light but discriminate frequency
1 cone:1 sensory neuron in the fovea centralis results in little convergence, high acuity or good detail resolution; no summation possible
concentrated in the center of the retina, especially in the fovea centralis
Three types of cones
red, green, and blue
Bipolar Cells
synapse with rods and cones
ganglion cells-
synapse with bipolar cells; leave the eye in the optic nerve
horizontal cells-
lateral connections between photoreceptors and bipolar cells
amacrine cells-
lateral connections between bipolar and ganglion cells
Opsin in Rods
rhodopsin, and it absorbs all wavelengths in the visible spectrum.
Opsin in Cone Pigments
Absorbs at different wavelengths than rhodopsin
Photopigments have 2 parts
Opsin and Retinal. Retinal is the same in all photoreceptors, but opsins vary
Electrical Activity in the Dark
- In the outer segment, there is a high concentration of CGMP.
- Na+ channels open.
- Depolarization spreads across the receptor.
- Once at the synaptic end of the photoreceptor, Ca++ channels open.
- There is an increase in the release of the neurotransmitter glutamate.
- This inhibits bipolar cells.
- As a result, there is no action potential on ganglion cells.
Electrical Activity in Light
- In the outer segment, a photopigment absorbs light causing a conformational change in the retina that activates opsin.
- This decreases the concentration of CGMP.
- Na+ channels close.
- The photoreceptor is hyperpolarized.
- Ca++ channels close.
- There is a decrease in the release of neurotransmitter.
- The bipolar cells are disinhibited (excited), and the potential is graded. Stronger light causes greater excitation.
- This causes an action potential on ganglion cells.
Red-Green Colorblindness
Individuals with red-green color blindness are unable to distinguish between red and green because they have two types of cones instead of three (blue and red/green cones). Red-green color blindness is much more common in males because it is a sex-linked recessive trait.
Our perception of color depends on
the relative excitement of three types of cones.
Blue light color percentages
97% Blue cones stimulated
Yellow light color percentages
83% Green cones stimulated
83% Red cones stimulated
Green Light Color Percentages
36% Blue Cones stimulated
67% Green Cones Stimulated
31% Red Cones Stimulated
Orange Light Color Percentages
42% Green Cones stimulated
99% Red Cones Stimulated
3 Parts of the Brain
Hindbrain
Midbrain
Forebrain
Parts of the Hindbrain
medulla oblongata, pons, and cerebellum
medulla oblongata-
This is the most posterior part of the brain just anterior to the spinal cord. It is the major control center for several vital functions Respirations CV function Vomiting Swallowing Coughing
respiration-
location of medullary chemoreceptors that sample H+/CO2; location of neurons that control ventilation
cardiovascular function-
input from baroreceptors; location of neurons that control heart activity
vomiting-
sample the blood looking for toxins
Pons
This is next up from the medulla. The pons is mostly involved in conduction of impulses to and from the cerebrum.
cerebellum-
This is off the main stem. The cerebellum can be divided into three lobes or hemispheres. The function of the cerebellum is to control motor function
vestibulocerebellum-
responsible for balance and control of eye movements
spinocerebellum-
regulates muscle tone and coordination of skilled voluntary movement; compares intentions of cerebrum with performance of muscles and corrects any errors or deviations from the intended movement
cerebrocerebellum-
planning and initiation of voluntary motor activity
Roof of the midbrain
corpora quadrigemina and has four bumps
superior colliculli that
have roles in visual reflexes and moving the head in response to visual stimuli
inferior colliculli
have roles in auditory reflexes and moving the head in response to auditory stimuli.
The base of the midbrain is called
the cerebral peduncles, which are massive nerve tracts carrying information to and from the cerebrum.
Parts of the Forebrain
thalamus, hypothalamus, and cerebrum
thalamus-
The thalamus is on top of the midbrain and found deep in the brain. It is an important relay station for preliminary processing of virtually all sensory input going to the cerebrum
hypothalamus-
The hypothalamus is below the thalamus and has several vital functions.
temperature center-
thermostats that control body temperature; origin of sweating and shivering
Food intake
Glucostats
Feeding Center
Station Center
feeding center-
when stimulated, it causes feeding; if destroyed, the individual will not eat
satiation center-
when stimulated, it stops feeding; if destroyed, the individual will not stop eating
water intake-
osmoreceptors; when there is high osmolarity (salt) in the blood, the individual becomes thirsty and urine volume decreases
sleep/wake cycles-
daily clock; affected by jet lag, daylight savings time, and photoperiod
hormones-
produces hormones that regulate urine production, uterus contractions during labor, ejection of milk during lactaction, and the pituitary gland
cerebrum-
largest, most conspicuous part of the brain; made up of two hemispheres (left and right); connected by the corpus callosum, which is a thick band of approximately 300,000,000 axons
Function of the Cerebrum
intelligence, reason, consciousness, discretion, etc.; not much known about the cerebrum, and there is no suitable animal model
Two regions of the cerebrum
White and grey matter
Outer Layer of the cerebrum
called the cerebral cortex, is made of grey matter and is made up of cell bodies.
White matter contains
myelinated fibers and is found inside the cerebrum
In the spinal cord, the position of the grey and white matter
is reversed with the grey matter in the inner layer of the cord and white matter in the outer layer of the cord.
Deep within the white matter is
more grey matter called basal nuclei
Cerebrum 4 lobes
Occipital Lobes
Temporal Lobes
Parietal Lobes
Frontal Lobes
occipital lobes-
back of the cerebrum; processes visual input
temporal lobes-
sides of the cerebrum; processes auditory input
parietal lobes-
top of the cerebrum; two main functions
Parietal Lobe functions
processing sensory input from the surface of the body such as temperature, pressure, pain, proprioreception; left side of body sends input to the right parietal lobe; somatosensory cortex is just behind the central sulcus which is a deep notch separating the parietal and frontal lobes; homunculus and modality apply here (partnership with thalamus)
understanding speech- Wernicke’s Area (discussed more later)
frontal lobes-
front of the cerebrum; three main functions
voluntary motor activity- primary motor cortex; located just in front of the central sulcus; has partnership with cerebellum; left side muscles controlled by right frontal lobe; homonculus applies and modality in reverse
speaking ability- Broca’s Area (discussed more later)
elaboration of thought
Simple and initial motor/sensory integration occurs in
the primary motor cortex or somatosensory cortex
More complex integration occurs
more inward in the parietal and frontal lobes
Association areas are “silent areas”, meaning
that electrical stimulation in these regions causes no observable motor or sensory response.
Prefrontal Association Cortex-
in the frontal lobe; controls planning, decision making, and personality traits; this part is removed in a lobotomy
Parietal-temporal-occipital Association Cortex-
pools and interprets somatic/auditory/visual sensations; comlex perceptual processing; also part of connection between Wernicke’s Area and visual and auditory cortexes
Limbic Association Cortex-
inner surface and bottom of temporal lobe; motivation, emotion, and memory
Wernicke’s Area-
posterior parietal lobe (left side of right-handed people); somatic, visual, auditory association areas all come together here; general interpretative area; gnostic area; knowing area; tertiary association area; electrical stimulation in Wernicke’s Area occassionally causes a complex thought
Angular Gyrus-
just behind Wernicke’s Area and fusing with occipital lobe in behind; interpretation of visual information; if angular gyrus is destroyed, one can still interpret auditory data normally because the person can see the words but can’t interpret the meaning (dyslexia or word blindness)
When a person learns a second language, where is it stored?
In a separate place from the first language
When two languages are learned at the same time, where is it stored?
in the same place
Broca’s Area is found
in the left frontal lobe
Broca’s Area function
responsible for language expression. It is wired to facial muscles causing contractions that make appropriate sounds. Broca’s Area is also wired to hand muscles causing contractions responsible for writing.
Wernicke’s Area is found
The left parietal Lobe
Wernicke’s Area Function
responsible for language comprehension and formulation of coherent speech for expression by Broca’s Area. It receives input from the occipital lobe for reading comprehension and describing an object. Input from the temporal lobe is used for speech comprehension.
Basal nuclei are made of
grey matter deep within the white matter
The basal nuclei have three main functions
Inhibitory aspects of maintaining muscle tone
Help monitor and coordinate slow, contractions
selecting and maintaining useful motor activity
inhibitory aspects of maintaining muscle tone-
Tone is the balance between excitation and inhibition of neurons associated with skeletal muscles.
Parkinson’s Disease is caused by
degeneration of dopamine-secreting neurons of basal nuclei
The symptoms of Parkinson’s
are useless or unwanted movements (trembling), increased muscle tone (rigidity), difficulty (slowness) initiating and carrying out different motor behaviors, and impeded speech.
Parkinson’s can be treated with
administration of L-dopa, an isomer of dopamine. Dopamine itself cannot cross the blood brain barrier, but L-dopa can cross.
The limbic system is
a ring of forebrain tissue (cerebrum, thalamus, hypothalamus components) surrounding the midbrain.
If you stimulate parts of the limbic system, you can produce
joy, satisfaction, fear, anxiety, anger, etc. If you stimulate other parts, copulatory movements are produced.
An EEG
is a record of the electrical activity in the brain. Electrodes on the scalp record electrons, mostly EPSPs and IPSPs in the brain. EEGs are used to diagnose cerebral dysfunction, distinguish between different types of sleep, and determine legal brain death (no EEG activity).
On average, about 20% of time sleeping is
REM (Rapid Eye Movement)
Short-term memory is
used for rapid retrieval and is usually permanently lost or forgotten.
information that is consolidated or practiced can become part of
one’s long-term memory. Long-term memory is used for slower retrieval but is usually only transiently forgotten.
Engraved memories are
long-term memories that are rapidly retrieved
Declarative memories are
things stated and are stored in the temporal lobes.
Procedural memories
such as the steps of a certain dance, are stored in the cerebellum.
Memory is located in
temporal lobes, limbic system, cerebellum, and diffuse other regions of the cerebrum.
Short-term memory causes transient changes in
pre-existing synapses
Long-term memory causes permanent physical changes
in the brain
The steps in storing long-term memories are:
new synaptic connections between neurons form
changes in presynaptic or postsynaptic neurons
increase or decrease neurotransmitter release and synthesis
Anterograde amnesia occurs when
the hippocampus is surgically removed
A person with anterograde amnesia can recall
previously learned memoried fine but is unable to learn anything new based on verbal symbolism. They can remember for moments then forget, even names they see every day.
Tumors in the CNS are
inappropriate divisions of glial cells since neurons don’t divide by mitosis.
Four types of Glial Cells
Astrocytes
Oligodentrocytes
Ependymal Cells
Microglia
Astrocytes-
most abundant glial cell; several functions
act as glue holding neurons together in correct spatial arrangements
help repair injuries and with scar formation
help with metabolic needs of neurons
Astrocytes
remove excess K+ from the extracellular fluid when brain activity outstrips the Na+/K+ pump; if excess K+ wasn’t removed, the membranes would be hyperpolarized; hyperpolarization is related to epileptic seizures
help form the blood-brain-barrier;
Oligodendrocytes-
form myelin sheaths around CNS axons; increase conduction speed; found in white matter; not capable of regeneration the way Schwann cells help with peripheral neurons
Ependymal Cells-
line internal cavities of CNS; contribute to the formation of cerebrospinal fluid
Microglia-
macrophages; cousins of monocytes; scavenge and phagocytize cell debris or foreign invaders
Astrocytes in the blood brain barrier
astrocytes form tight junctions that prevent material from leaving the brain through capillary pores; no capillary pores in brain capillaries; material must move through protein channels and can move more easily into the plasma from the interstitial fluid and cerebrospinal fluid
Meninges
Three protective and nourishing membranes
lie between bone and nervous tissue; meningitis is swelling associated with meninges
Meninges (Layers)
Dura Mater
Arachnoid Mater
Subarachnoid Space
Pia Mater
dura mater-
“tough mother”; tough, inelastic membrane overlying bone
arachnoid mater-
“spiderlike mother”; delicate, highly vascularized layer; communication between the cerebrospinal fluid and blood; overlying bone
subarachnoid space-
space between arachnoid and pia mater (see next); filled with cerebrospinal fluid
pia mater-
“gentle mother”; fragile, highly vascularized; closely adheres to brain tissue; supplies brain tissue with blood; overlying brain tissue
Brain and CNS surrounded by special shock-absorbing fluid called
Cerebrospinal Fluid (CSF)
Blood-Brain Barrier
The blood–brain barrier (BBB) is a highly selective semipermeable border of endothelial cells that prevents solutes in the circulating blood from non-selectively crossing into the extracellular fluid of the central nervous system where neurons reside.
Serotonin is
a “feel good” neurotransmitter. It is associated with clinical depression, post-traumatic stress disorder, and anxiety disorders. Paxil is a drug administered to treat all these disorders, and it works by blocking serotonin reuptake pumps so serotonin remains in the synapses longer. Serotonin is primarily an inhibitory neurotransmitter.
Dopamine is
also a feel good neurotransmitter and is associated with Parkinson’s Disease. People with Parkinson’s Disease have low dopamine levels. Dopamine may also be associated with schizophrenia. Dopamine is primarily an inhibitory neurotransmitter.
Nitric Oxide is associated with
memory
Enkephalins and endorphins are opiates associated with
suppression of pain. Morphine is an analgesic that stimulates the same receptors as enkephalins and endorphins
GABA
a major inhibitory neurotransmitter. GABA inhibits skeletal muscle pathways. Tetanus toxin prevents the release of GABA, which explains the symptoms of lockjaw. Death from lockjaw is due to respiratory failure because the diaphragm wouldn’t relax
Glycine
an inhibitory neurotransmitter. Strychnine, a component of rat poison, blocks receptors for glycine.
