Nervous system Flashcards
The nervous system
responsible for controlling most body functions, enabling organisms to receive and respond to stimuli from their external and internal environments.
Which is faster in relaying signals to the brain, the endocrine or the nervous system?
the nervous system. 100m/s in some cases
neurons
specialized nervous tissue that convert stimuli into electrochemical signals.
neuroglia
cells that support and protect the neurons
Organs of the nervous system
brain, spinal cord, eye, ear, etc.
What are the two divisions of the nervous system?
CNS, PNS
What are the functional units of the nervous system?
neurons
What are neurons composed of?
dendrites, cell body, axon
dendrites
cytoplasmic extensions that receive information and transmit it toward the cell body
cell body (soma)
contains the nucleus and controls the metabolic activity of the neuron.
axon
long cellular process that transmits impulses or action potentials away from the cell body. sheathed with myelin.
Myelin sheath
prevents leakage of signal from the axon and allows for faster conduction of impulses
Nodes of ranvier
gaps between the segments of myelin where the action potential actually propagates through saltatory (hopping) conduction.
Oligodendrocytes
Glial cells that protect the myelin sheath in the CNS. provide structural framework for the CNS
Schwann Cells
Glial cells that protect the myelin sheath in the PNS. Aid in the myelination of some peripheral axons
synaptic terminals
swellings in the axon ends. realease neurotransmitter via this into the synapse (synaptic cleft).
Major cells of the CNS
Astrocytes, Oligodendrocytes, Microglia, Ependymal Cells.
Major cells of the PNS
Satellite cells and Schwann Cells
Astrocytes
CNS. Maintain the integrity of the blood-brain barrier, regulate nutrient and dissolved gas concentrations, and absorb and recycle neurotransmitters
Microglia
CNS. remove cellular debris and pathogens
Ependymal Cells
CNS. Line the brain ventricles and aid in the production, circulation, and monitoring of CSF
Satellite Cells
PNS. Surround the neuron cell bodies in the ganglia
Polarized neurons
Neurons are polarized even at rest because of unequal distribution of ions between the inside and outside of the cell.
resting potential
the potential difference at rest between the extracellular space and the intracellular space. -70mV. inside of the neuron is more negative.
Na+/K+ pump
Maintains the selective permeability of the neuronal cell membrane. Pumps 3Na+ out of the cell for every 2K+ it transports into the cell. Cell membrane is more permeable to K+ than to Na+.
Action Potential
When cell body becomes excited and depolarized (inside less negative), to reach the threshold potential, then voltage-gated ion channels located in the nerve cell membrane open in response. Begins when the Voltage-gated Na+ channels open in response to depolarization, allowing Na+ to rush down electrochemical gradient into cell causing further depolarization. Process continues down axon toward terminal. Once the synaptic cleft is reached another voltage0gated channel opens for calcium. Ca triggers the endocytosis of synaptic vesicles containing neurotransmitters. ALL OR NONE. frequency and not magnitude
Repolarization
Voltage gated K+ channels open allowing K to rush down its electrochemical gradient and out of the cell. Na+ channels close and the Pump pumps Na out of cell again. Return the cell to a negative potential.
Hyperpolarizaton
cells gets more negative than necessary in the refractory period.
What would cause a faster propagation of a signal down an axon?
Larger diameter and more myelination.
effector cells
cells other than neurons that other neurons can communicate with. Muscle cells
neurotransmitters
the nerve terminal contains thousands of membrane bound vesicles containing these chemical messengers. When released from pre synaptic cells, they bind to post synaptic cells on proteins. Can be removed from the synapse by being taken back up into the nerve terminal where it may be reused or degraded or it may be degraded by enzymes or it may diffuse into the synapse
Effects of Curare
blocks post synaptic nicotinic acetylcholine receptors, such as those on muscles, so acetylcholine is unable to interact with them. This leads to muscle relaxation and paralysis by blocking the ability of muscle to constrict
Effects of Boulinum toxin
prevents the release of acetylcholine from the presynaptic membrane and also results in paralysis
Effects of Anticholinesterases
used as nerve gases and in the insecticide parathion. inhibit the activity of the acetylcholinesterase enzyme responsible for degrading acetylcholine released into the synapse. acetylcholine is not degraded and continues to affect the postsynaptic membrane. No coordinated muscular contractions can take place.
afferent neurons
sensory
efferent neurons
motor
INterneurons
link sensory and motor neurons in the brain and spinal cord. cell bodies and nerve terminal in the same location.
plexus
network of nerve fibers
neuronal cell body clusters in the PNS
ganglia
neuronal cell body clusters in the CNS
nuclei
PNS comprised of?
Somatic and autonomic
autonomic nervous system comprised of?
sympathetic and parasympathetic
Outer portion of cell bodies in the brain
gray matter
inner portion of myelinated axons of the brain
white matter
Forebrain
telencephalon and the diencephalon
telencephalon
forebrain. cerebral cortex (highly convoluted gray matter that can be seen on the surface of the brain. processes and integrates sensory input and motor responses and is important for memory and creative thought.) Olfactory bulb (center for reception and integration of olfactory input.)
diencephalon
Forebrain. Thalamus (relay and integration center for the spinal cord and cerebral cortex.) Hypothalamus (controls the visceral functions such as hunger, thirst, sex drive, water balance, blood pressure, and temperature regulation. important role in the control of the endocrine system)
MIdbrain
Mesencephalon. relay center for visual and auditory impulses. motor control
Hindbrain
Rhombencephalon. cerebellum (helps to modulate motor imuplses initiated by cerebral cortex; balance, hand eye coordination, timing f rapid movements), pons (relay center for the cortex to cerebellum), medulla (breathing, heart rate, GI activity). all make up the brainstem
Spinal Cord outer white matter area
motor and sensory axons
spinal cord inner gray matter area
nerve cell bodies
dorsal horn of the spinal cord
sensory information enters the spinal cord through this. The cell bodies of these axons are located in the dorsal root ganglia
ventral horn of spinal cord
where all motor information exits the spinal cord.
somatic nervous system
innervates skeletal muscles and is responsible for voluntary movements as well as reflex arcs
autonomic nervous system
involuntary nervous system. includes both sensory and motor fibers. innervates cardiac and smooth muscles. blood pressure control, GI motility, excretion, respiration, and reproduction.
sympathetic nervous system
fight or flight. uses norepinephrine.
parasympathetic nervous system
rest and digest. vagus nerve. uses acetylcholine
sclera
thick opaque layer covering the eyeball
choroid layer
layer beneath the sclera. supplies the retina with blood. dark pigmented reduces reflection in the eye
retina
contains photoreceptors that sense light
cornea
bends and focuses light rights at the front of the eye.
Pupil
Rays travel from the cornea through the pupil, whose diameter is controlled by the pigmented iris
iris
responds to intensity of light in the surroundings.
lens
light travels through pupil, then through the lens which focuses images onto the retina
ciliary muscles
controls the shape and focal length of the lens.
photoreceptors
transduce light into action potentials
cones
high intensity illumination and are sensitive to color. absorb red, green, and blue wavelengths.
rods
low intensity illumination and are important in night vision. Rhodopsin (the rod pigment) only absorbs a single wavelength.
how do the photoreceptor cells synapse?
onto bipolar cells, which in turn synapse onto ganglion cells.
Optic nerve
bundles of axons of the ganglion cells make up the optic nerve, which conducts visual information to the brain.
blind spot
the point at which the optic nerve exits the eye
fovea
small area above the blind spot that is densely packed with cones and it important for high-acuity vision.
vitreous humor
jelly like. maintains shape and optical properties
Aqueous humor
watery. fills the space between the lens and the cornea
myopia
nearsightedness. image focused in front of the retina
hyperopia
farsightedness. image is focused behind the retina
astigmatism
irregularly shaped cornea
cataracts
lens becomes opaque. light cannot enter the eye and blindness results
glaucoma
increase in eye pressure because of blocking of the outflow of the aqueous humor, which results in optic nerve damage.
Sound energy
pressure waves
outer ear
auricle (external ear) and the auditory canal.
middle ear
tympanic membrane, ossicles (malleus, incus, and stapes) oval window.
inner ear
cochlea, vestibular apparatus (equilibirum)
