Exam 4 Study Guide Flashcards
How are stimuli communicated to the central nervous system?
Sensory stimuli is turned into electrical signals that are passed along by neurons within the PNS and travel to the CNS
How are responses sent to effectors in the body?
the CNS makes a decision and the motor neurons transmit the information to the designated area of the body to carry out a response
What is the threshold for production of an action potential?
-55mV
Why is -55mV the threshold?
When depolarization reaches threshold, it becomes self generating, urged on by positive feedback. As more Na enters, the membrane depolarizes further and opens more ion channels until all Na channels are open.
Name the five essential components of the reflex arc.
- receptor
- sensory neuron
- integration center
- motor neuron
- effector
Describe the process of the reflex arc.
The receptor picks up a stimulus then sends it down the sensory neuron. The sensory neuron then sends it into the integration center where a decision is made on what to do. The decision is then sent down the motor neuron, which sends it to the effector. The effector carries out the decision.
Describe the retina
-the innermost layer of the eyeball that develops from extension of the brain
-delicate two layer membrane
-absorbs light and keeps it from scattering
-composed of photoreceptors, bipolar cells, and ganglion cells
-contains the optic disc and quarter billion photoreceptors
Describe rods
-dim light and peripheral vision receptors
-no color vision or sharp images
-more numerous and sensitive to light than cones
Describe cones
-vision receptors for bright light
-high resolution color vision
-fovea centralis is a tiny pit in center or macula w all cones; best vision
Describe ganglion cells
-generate AP’s transmitted in optic nerve to brain
-ganglion cell axons exit eye as optic nerve
Describe graded potentials
-the more neurotransmitters, the more graded potentials
-the longer they stick around, the more graded potentials
-short lived, localized changes in membrane potential
-can either be depolarizations or hyperpolarizations
-are triggered by changes in the neuron’s environment that opens gated ion channels
-the more GP there are, the closer you are to an AP
Describe excitatory postsynaptic potentials(EPSP)
EPSPs move closer to the threshold
Describe inhibitory postsynaptic potentials(IPSP)
IPSP’s move away from the threshold
What is an action potential?
a brief change in membrane potential in a patch of membrane that is depolarized by local currents
Describe the optic nerve
-only consists of sensory function(vision), not motor function
Describe the visual cortex
-located in the occipital lobe
-receives visual information that originates on the retina of the eye
-the largest cortical sensory area
Describe gray matter
consists of short, nonmyelinated neurons and neuron cell bodies
Describe white matter
consists mostly of myelinated axons with some nonmyelinated axons, primarily in fiber tracts; the dense coating of fatty myelin is what gives white matter its color
Describe the cerebral cortex
the “executive suite” of the nervous system where the conscious mind is found; enables us to be aware, communicate, remember, and understand; composed of grey matter
The brain stem consists of:
the midbrain, pons, and medulla oblongata
Brain centers produce the rigidly programmed:
automatic behaviors necessary for survival
The brain stem is heavily involved with
innervating the head
Describe the cerebellum
ultimate planner and coordinator of complex motor activities; also adjusts motor output, ensuring coordination and balance
What are sulci?
shallow grooves marking the surface of the brain
What are fissures?
deep(deeper than sulci) grooves marking large regions of the brain
The median longitudinal fissure separates the ______ _________.
cerebral hemispheres
The ________ ______ _______ separates the cerebral hemispheres from the cerebellum below
transverse cerebral fissures
Commissural fibers connect:
corresponding gray matter areas of the two hemispheres, allowing the two hemispheres to function as a coordinated whole.
-Largest commissure is the corpus callosum
Association fibers connect:
different parts of the same hemisphere.
Sensory information reaches the cerebral cortex and motor output leaves it through _________ _____.
projection fibers
-they tie the cortex to the rest of the nervous system and to the body’s receptors and effectors
What are the three major regions of the brain stem?
midbrain, pons, medulla oblongata
What is the function of the midbrain?
contains visual and auditory reflex centers
What is the function of the medulla oblongata?
contains the vital centers such as the cardiac, vasomotor, and respiratory centers
What is the function of the pons?
handles unconscious processes, such as breathing and sleep-wake cycle
What are the meninges and its function?
a specialized connective tissue that envelopes and protects the brain; it is composed of the outer layer: dura mater, the middle layer: arachnoid mater, and the innermost layer: pia mater
What is cerebrospinal fluid and its purpose?
separates the brain and the arachnoid mater; serves as a cushion that protects the brain from injury while allowing the exchange of substances between the brain and blood
Where is cerebrospinal fluid created?
the choroid plexus in the third ventricles
What is the blood brain barrier?
a functional barrier that allows the passage of some substances from the blood into the CSF while preventing the passage of others
What is the cause behind Alzheimer’s disease?
Alzheimer’s is a form of dementia that is characterized by the atrophy of the frontal and temporal cortex of the brain; affects older people(~70+); caused by the buildup of amyloid proteins in the brain
What is the cause behind Parkinson’s disease?
is a subcortical neurogenetive disorder characterized by the movement disorders and changes of the motor system of the midbrain; characterized by the degeneration of dopamine releasing neurons of the substantia nigra; basal nuclei become more overactive
What is the cause behind Huntington’s disease?
fatal hereditary disorder; Huntington protein accumulates in brain cells and tissue dies; presents w/ motor disturbances, progressive dementia, and abnormal behavior; most patients become mentally incapacitated and die within 20 years of onset
Describe exteroreceptors
detect stimuli outside the body, so most are located near the body surface; include touch, pressure, pain, and temperature
Describe interoreceptors
aka visceroreceptors; respond to stimuli within the body; monitor chemical changes, tissue stretch, and temperature; their activity can cause us to feel pain, discomfort, hunger, or thirst; usually unaware of their workings
Describe proprioreceptors
respond to internal stimuli, however location is more restricted than interoreceptors; occur in skeletal muscles, tendons, joints, and ligaments; advise the brain of our body movements by monitoring how much organs containing the receptors are stretched; inform brain of where body is in space
What is a ganglion?
a collection of neuron cell bodies in the PNS
What is a nerve?
cordlike bundle of axons that conduct sensory and motor impulses
Describe the regeneration of nerves
mature neurons do not divide. If damage is severe or close to the cell body, the entire neuron may die. However, if the cell body remains intact, axons of peripheral nerves can regenerate but axons in the CNS cannot
Describe mixed nerves
contain both sensory and motor fibers and transmit impulses both to and from the CNS
Describe sensory(afferent) nerves
carry impulses only toward CNS
Describe motor(efferent) nerves
carry impulses only away from the CNS
Describe the general structure of a nerve
Epineurium surrounds fascicles that make up a nerve, the perineurium surrounds the fascicles, the endoneurium surrounds the axons that make up the fascicles
Name the components of the reflex arc
- receptor
- sensory neuron
- integration center
- motor neuron
- effector
Define the autonomic nervous system and explain its relationship to the peripheral nervous system
subdivision of the peripheral nervous system that regulates body activities that are not under conscious control; aka involuntary nervous system; motor pathways
What is the somatic nervous system?
aka the voluntary nervous system; innervate the skeletal muscles
What are the effectors of the autonomic nervous system?
cardiac muscle, smooth muscle, glands
What are the effectors of the somatic nervous system
skeletal muscle
What are the functions of the parasympathetic nervous system?
-conserves energy
-promotes house keeping functions during rest(ie: digesting food)
-“rest and digest” system
What are the functions of the sympathetic nervous system?
-mobilizes body systems during activity
The wall of the eyeball contains three layers which are:
fibrous, vascular, inner
Mechanoreceptors:
respond to touch, pressure, vibration, and stretch (ie: Dr checking patellar tendon)
Thermoreceptors:
sensitive to changes in temperature
-a hot stove would set off nociceptors NOT thermoreceptors bc it is causing pain
Photoreceptors:
respond to light energy
Chemoreceptors:
respond to chemicals(eg: smell, taste) (ie: taste buds, olfactory receptors)
Nociceptors:
sensitive to pain causing stimuli(eg: extreme heat or cold, excessive pressure)
Brown pigment absorbs _____ to prevent it from ________ and visual confusion.
light; scattering
Describe the pupil.
central opening that regulates amount of light entering the eye
For close vision and bright light-
the sphincter pupillae contract; pupils constrict
For distant vision and dim light-
dilator pupillae contract; pupils dilate
Changes in emotional state-
pupils dilate when subject matter is appealing or requires problem solving skills
What are the two photoreceptors?
rods and cones
What are rods used for?
-dim light and peripheral vision
-no color vision or sharp images
-sensitive to light
What are cones used for?
-need bright light for activation
-high resolution color vision
What is the fovea centralis?
tiny pit in center of macula with all cones
What is the optic disc?
-site where optic nerve leaves eye
-lacks photoreceptors
-blind spot
Describe the lens of the eye
-changes shape to precisely focus light on retina
-biconvex, transparent, flexible, avascular
-two regions:
-lens epithelium
-lens fibers
What are cataracts?
clouding of lens
Pathway of light entering eye:
cornea, aqueous humor, lens, vitreous humor, entire neural layer of retina, photoreceptors
Where is light refracted in the pathway of light?
- entering the cornea
- entering the lens
- leaving the lens
-majority of refractory power in cornea
How is light focused for distant vision?
the lens flattens
How is light focused for close vision?
lens squishes to make thicker
What is presbyopia?
farsightedness; loss of accommodation over age 50
The inner neural layer is composed of three main types of neurons, which are:
photoreceptors, bipolar cells, ganglion cells
Optic nerve is only a ______ receptor.
sensory
Outer pigmented layer of retina:
-absorbs light and prevents is scattering
-stores vitamin A
Photopigments(visual pigments)-
change shape as absorb light
Why are cones used for high resolution vision?
pathways are nonconverging resulting in detailed high res vision; have their own ganglion cells
Why do rods result in fuzzy images?
the pathways converge, resulting in fuzzy indistinct images; all share ganglion cells
What causes color blindness?
the lack of one or more cone pigments
How do visual pigments work when lights hit them?
retinal(light absorbing molecule) combines with 1/4 proteins(opsins) to form visual pigments
What are the three steps of rhodopsin formation and breakdown?
-pigment synthesis
-pigment bleaching
-pigment regeneration
What occurs during pigment synthesis?
11-cis-retinal, is combined with opsin to form rhodopsin
What occurs during pigment regeneration?
enzymes slowly convert all trans retinal to its 11-cis form in cells of the pigmented layer; requires ATP
What occurs during pigment bleaching?
retinal changes shape bc of light absorption by rhodopsin(11-cis to all-trans) and eventually releases from opsin
11-cis retinal is
bent form(dark)
all-trans retinal is
straight form(light)
In order to smell substance, it must be _______?
volatile(dissolved or evaporated)
Olfactory receptors require ______, which acts as a solvent for odorants.
mucus
Gaseous odorant must ______ in fluid of olfactory epithelium.
dissolve
Dissolved odorants bind to receptor proteins in ________ ______ ________.
olfactory cilium membranes
Humans have ~100 smell genes active in the those that encode for ______ _______ ______.
unique receptor protein
What are the five basic taste sensations?
sweet, sour, salty, bitter, umami
What causes a sweet taste sensation?
sugar, saccharin, alcohol, etc
What causes a sour taste sensation?
hydrogen ions in solution
What causes a salty taste sensation?
metal ions(inorganic salts); sodium chloride taste saltiest
What causes a bitter taste sensation?
alkaloids such as quinine, nicotine, caffeine
What causes an umami taste sensation?
amino acids glutamate and aspirate; ie: beef or cheese taste
Explain how taste receptors are activated
- binding of food chemical(tastant) depolarizes cell membrane of gustatory epithelial cell membrane, causing release of neurotransmitter
- neurotransmitter binds to dendrite of sensory neuron and initiates a generator potential that lead to action potentials
What are the three major areas of the ear?
-external ear
-middle ear
-internal ear
What is the purpose of the external ear?
hearing only
What is the purpose of the middle ear?
hearing only
What is the purpose of the inner/internal ear?
hearing and equilibrium
What are the three ear ossicles
malleus, incus, stapes
What are the two major divisions of the internal ear?
bony labyrinth & membranous labyrinth
What are the three regions of the bony labyrinth?
vestibule, semicircular canals, cochlea; also filled with perilymph
What is the membranous labyrinth?
series of membranous sacs and ducts; filled w endolymph
The semicircular canals allow you to know
where you are in space
Describe the crista ampullaris
-structure of the inner ear
-has hairlike structures
-endolymph moves in direction of rotation, moving the cupula, which excites the hair cells
Pitch perceived by impulses from ______ _____ _____ in different position along basilar membrane.
specific hair cells
Loudness detected by ______ ___ _______ ________ that result when hair cells experience larger deflections
increased number of action potentials
What is otitis media?
inflammation of the inner ear
What is sensorineural deafness?
damage to neural structures at any point from the cochlear hair cells to and including the auditory cortical cells; usually results from gradual loss of hair cells throughout life
The semicircular canals monitor changes in:
head rotation, called our sense of dynamic equilibrium.
How do the semicircular canal and vestibule help maintain equilibrium?
They send signals to the brain that initiate reflexes needed to make changes in position as well as more complex movement such as pitching a ball.
First order sensory neurons
conduct impulses from receptor level to spinal reflexes or second order neurons in CNS
Second order sensory neurons
transmit impulses to third order sensory neurons
third order sensory neurons
conduct impulses from thalamus to the somatosensory cortex
Ventral roots
-contain motor(efferent) fivers from ventral horn motor neurons
-fibers innervate skeletal muscles
Dorsal roots
-contain sensory(afferent) fibers from sensory neurons in dorsal root ganglia and conduct impulses from peripheral receptors
Dorsal and ventral roots unite to form _____ _____, which emerge from vertebral column via ___________ ________.
spinal nerves; intervertebral foramina
What is the integration center in a simple reflex
single synapse between a sensory neuron and motor neuron; monosynaptic reflex
