Studied by 4 peopleTrue
True or False? The nervous system must be able to send signals to, and receive signals from, all parts of an animal’s body.
Excitable Cells
in general its cell membrane can generate and conduct impulses, or action potential
permits neurons to carry signals over long distances
Neurons
all parts of the animal nervous system are composed of _____
Multi-part, typically elongate, cells that are bundled into long strands called nerves
Thousands of _____ within a sheath
originate in the central nervous system
Signals are delivered to only defined locations
Nerves
Neurons are multi-part cells that are bundled into long strands called ______
An individual ____ will consist of thousands of individual neurons bundled together in a sheath
Originate in the central nervous system which consists of the brain and spinal cord
Sheath
multiple neurons bundled into a nerve _____
Four anatomical regions of a Neuron
1) A set of Dendrites
2) A Cell body
3) An axon
4) A set of presynaptic axon terminals
Dendrites
receive signals from other cells
Cell body of a neuron
contains the nucleus and organelles and serves to integrate the incoming signals
Axon
a long process that is anatomically specialized for long-distance signal conduction
Synapse
the point of innervation which allows the nervous system to communicate with and control other cells
cell to cell contact point that is specialized for signal transmission from one cell to another
Glial Cells
found in the vertebrate nervous system
While these cells are not excitable and do not transmit impulses, they are nonetheless important cells that support, insulate and nourish
Central nervous system relies upon these for metabolic functions
Myelin
glia wrap around the axons to form an electrical insulation
helps to improve the efficiency and speed of transmission
The Central Nervous System
brain and spinal cord
The peripheral Nervous system
all parts of the nervous system except brain and spinal cord
False; Neurons must be excitable
True or False? neurons do not need to be excitable.
Action potential
are temporary, transient, reversals of electrical potentials on either side of the membrane
a state of reversed polarity of the cell membrane where an ______ present
permits neurons to carry signals over long distances
Electrical Potential
neurons establish an _____ by using ion channels n their membranes to maintain a net positive charge outside of the cell, and a net negative inside
Non polar lipids
the membrane, because it is composed of ________, is a crucial component in establishing these action and electrical potentials
Voltage
If left uninterrupted in a bulk solution, positive and negative ions would simply be attract to each other. A physical barrier allows the charges to be seperated, establishing a ______
Membrane Potential
a potential difference (voltage) across a membrane is called __________
Ion Concentrations
Changes in _______ across the membrane are mediated by ion channels.
False; The most important ion channel is the sodium - potassium pump
True or False? The most important ion channel is the saline pump.
The resting potential
of a neuron is primarily a function of the concentrations of sodium and potassium ions on either side of the membrane.
Sodium - Potassium Pump
To move the ions, the _________ uses one molecule of ATP to pump three sodium ions into the cell and two potassium ions out
Potassium Leak Channels
Potassium is allowed to move somewhat freely through _______
Potassium
will either follow a concentration gradient and move out of the cell, or will be pulled back into the cell by the electrical gradient
True
True or False? Due to strong voltage gradient across the membrane, and only because the ions closest to the membrane are affected, only very small changes in the distribution of ions are needed to propagate an action potential
Gated
some ion channels are _____, they will only open and close in response to a particular stimulus
Voltage - Gated Channels
respond to a change in membrane potential
Stretch - Gated Channels
respond to a physical stimulus, like touch pressure
Ligand - Gated Channels
will only open when their activator molecule binds to them
Depolarization
occurs when the inside of a cell becomes less negative than it is at rest
when gated channels are active
Hyperpolarization
occurs when the inside of a cell becomes more negative
when gated channels are active
Invertebrates
tend to use large-diameter neurons to quickly propagate actions potentials.
Squids
have. the largest - diameter neurons in the animal kingdom
Vertebrates
used saltatory conduction
Saltatory Conduction
use the gaps between myelin sheaths to increase the speed with which a potential is propagated
Chemical Synapse
when the action potential reaches the presynaptic bump, a chemical called a neurotransmitter is released. The neurotransmitter crosses a small gap, the synaptic cleft, before reaching the next cell. Neurotransmitter causes the electrical potential to be transmitted to the postsynaptic cell.
Electrical Synapse
the presynaptic cells share cytoplasm through gap junctions. The potential propagates very quickly though this
An Example of a Chemical Synapse
a synapse between a neuron and a muscle cell
True
True or False? sometimes, individual potentials are too small on their own to propagate a potential, but several potentials can be summed by a neuron in order to produce a single strong enough to cross the threshold for synaptic transmission.
Sensory Receptor Cells
are cells specialized for receiving energy from certain stimuli - light, pressure, chemical - and converting that energy into an action potential also know as signal transduction
Sensory receptor proteins
sensory receptor cells depends upon them
detect the stimulus and either directly or indirectly trigger a change in membrane potential
Ionotropic receptors
can directly trigger a membrane potential when they detect a stimulus
Metabotropic receptors
1) adorant molecule binds to the receptor
2) activate a G-protein
3) G-protein activates an enzyme that causes an increase in a secondary messenger
4) secondary messenger opens ion channel
Mechanoreceptors
respond to mechanical distortion of the cell membrane; most are ionotropic
cold and hot receptors
light touch, deep pressure
Pain = free nerve endings
Stretch Receptors
muscles adjusts the muscles strength of contraction to match the load the muscle can sustain
Receptors in the muscle detect how much the muscle is being lengthened by the load; keep the muscle as stable as the load increases
Chemoreceptors
senses olfaction and gustation (smell and taste)
Olfaction
sense of smell
Dogs
have 220,000,000 olfactory receptors
specialized ‘vomeronasal’ organ
Humans
have about 5 million olfactory receptors
Male Moths
have thousands of receptors on their antennae that respond to pheromones emitted by the females
Auditory Systems
use mechanoreceptors to sense sound pressure waves, many hearing organs have a membrane that move in and out when sound pressure waves hit us. In mammals this is the tympanic membrane
Tympanic Membrane
ear drum
The Ear
hearing and equilibrium
Cochlea
hearing
hold fluid in the _______ duct
Equilibrium: vestibule, semicircular canals
Visible light spectrum
750-400nm
Vertebrate Eyes
Image forming eyes, like a camera
Focusing and image formation by cornea and lens on retina
Photoreceptors
receptor cells sensitive to light
are metabotropic
consist of cones and rods
Rhodosins
consist of the protein opsin and a light - absorbing group 11-cis-retinal… changes to trans when exposed to light
Cones
color vision
better acuity
need bright light
5 million
have better visual acuity
fewer per nerve fiber
Rod
less visual activity
better in low light
100 million
_____ have less visual acuity
many _____ per nerve fiber means less ability to discriminate
Compound Eyes
arthropods have them consisting of units called ommatidia
each ommatidium points in a slightly different direction, the higher the image resolution
Fast-flying predators such as dragonflies have up to 30,000
Ommatidia
each has a lens to focus light onto photoreceptor cells containing rhodopsin
Ultraviolet Vision
Birds and insects see ____,photoreceptors in ultraviolet range <400nm
Sponges
do not have a nervous system
The Cnidarians and Echinoderms
have nerve nets, the simplest type of nervous system
Centralization
integrating neurons became clustered together in centralized organs (e.g. brain and spinal cord)
Cephalization
major integrating areas became concentrated toward the anterior end of the animal (head)
Centralization and Cephalization
Evolution of nervous system followed two major trends
Vertebrate Brains
have three main regions; forebrain, midbrain and hindbrain
Medulla oblongata
how the brain and spinal cord are connected
most posterior part of the hindbrain
Sensory Functions of the Nervous System
internal conditions and external environment
Integrative Functions of the Nervous System
relays sensory information to effectors
Motor Functions of the Nervous System
reacts to sensory / integrative input
carry signals to muscle cells, stimulating contraction
Grey matter
the outer 5mm of ______ in the cerebrum is responsible for consciousness, thought and abstraction
Sympathetic Nervous System
fight or flight
Parasympathetic Nervous System
rest and digest
Sensory Neurons
carry signals from sense organs to central nervous system
Spinal Nerves
arise in pairs, one going to each side of the body
Presynaptic Cell
cell that conducts signals into the synapse
Postsynaptic cell
the cell that conducts signals away from the synapse
Presynaptic axon terminal
at its end, an axon branches, and each branch terminates in a small swelling called…
Resting Potential
the membrane potential of a resting neuron is referred to as the ________
Note 
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