Flashcards in The nervous system Deck (104):
The nervous sytem is all about ....?
information and control
What does the nervous system do?
receives, processes, an distributes information by way of nerve impulses, and it directly or indirectly controls nearly all body functions.
What is the basic functional unit of the nervous system?
the neuron (nerve cell)
What two main divisions does the nervous system have?
Central nervous system and Peripheral nervous system
The Central nervous system is composed of ?
brain and spinal cord
The peripheral nervous system consists of _____ nerves that link the CNS with the ____________?
cordlike nerves rest of the body
The nervous system's activities fall into 3 main categories ,what are they?
1) sensory functions 2)integrating functions 3) motor functions
In the brain and spinal cord the sensory information is received, analyzed stored, and integrated to produce a response.
A motor response instructs the body to do something such as contract a muscle
The neuron can be divided roughly into what?
a cell body
extensions - dendrites and axons
dendrites receive stimuli, or impulses from other neurons
axons - conduct nerve impulses away from the cell body toward another neuron or an effector cell (a cell that does something when stimulated, such as a muscle or gland cell)
What are the nodes of Ranvier?
located between adjacent glial cells are small gaps in the myelin sheath
- enhances the speed of conduction of nerve impulses along the axon
What are afferent nerves?
conduct nerve impulses toward the CNS (ad means toward) - ferre means carry
What are efferent nerves?
conduct nerve impulses away from the CNS (ex - away)
What is the direction of impulses?
Afferent vs efferent A comes before E
What are afferent nerves also called when they conduct sensations from the sensory receptors in the skin?
What are efferent nerves called when they are the ones that cause skeletal muscles contraction and movement?
What is the Somatic nervous system's function?
a conscious, or voluntary control of skeletal muscles
What is a autonomic nervous system?
part of the nervous system that controls and coordinates these automatic functions also called self-regulating system
What are examples of autonomic nervous system?
Blood pressure receptors inform the body that the pressure is too low
When a neuron is in a resting state, what does this mean?
it means a neuron is not being stimulated - even resting it is still working - it has to work at staying at the resting state
- active rest - has the potential to work
- electronically polarized at rest (like tiny charge batteries
What is the sodium potassium pump?
- specialized molecules located in the neuron's cell membrane pump Na ions from the outside of the neuron to the inside and pump K ions from the inside to the outside
How much of the Na and K can the sodium potassium pump, pump at one time?
2 Na in and then the gate closes and 3 K go out
The cellular membrane separating Na and K is said to be polarized, why?
because it has 2 distinct poles of ions on either side of the membrane - this is accomplished by keeping Na (outside) on one side and K (inside) on the other side
What causes the negative charge in the cell and across the membrane?
the distribution of positive and negative charges from sodium, potassium, proteins, and other charged ions being more negative in the inside than the outside
What is the resting membrane potential?
the electrical difference in charges across the membrane
What is the net negative charge within the cell?
What keeps this negative charge within the cell (the resting membrane potential?
the sodium potassium pump
What is depolarization?
when neuron receives enough stimulation (finger burning) eventually will fire. The Na channel will open and Na will flood in (not as strong)
- because the Na influx results in the loss of 2 distinct poles of Na and K on either side of the membrane
What makes the Na channel only allow sodium ions to pass?
because a higher concentration of Na is on the outside than on the inside. Na readily flow through open Na channels from outside to inside by passive diffusion
Sodium is also driven into the cell by?
by the concentration gradient (the difference between the concentration of the outside and the inside) and the positive Na ions are attracted to the net negative charge inside the cell
When does the cell go from a negatively charged resting membrane potential to a net positive charge?
What is action potential?
the significant change in electrical charge from negative to positive
What is repolarization?
the change of the cell's charge back toward the net negative resting membrane potential
the only difference is that the Na and K are not in their original spots, they are in the opposite spots
What restores the Na/ K back to original locations?
needs ATP and the Na/K pump
What causes the cell to depolarize or fire?
it has reached the threshold - stimulus is strong enough
What is a threshold stimulus?
a stimulus of sufficient intensity to generate a nerve impulse
What is wave depolarization?
the wave of sodium channels opening to allow sodium influx (also called conduction of the action potential)
What is a nerve impulse?
this wave of depolarization or conduction of the action potential along the cell membrane
What is the all-or-nothing principle?
If the initial stimulus was strong enough to reach threshold, the action potential would be generated and conducted along the entire neuron with a uniform strength
- either the complete neuron depolarizes to maximum strength or it doesn't depolarize
What is the refractory period?
means that the neuron is insensitive to new stimuli until it recovers from the previous nerve impulse
What is absolute refractory period?
the cell absolutely cannot respond
What is relative refractory period?
if a very large stimulus comes during the tail end of repolarization, it may be possible to stimulate anther depolarization.
What is salatory conduction?
a nerve impulse jumps from one node of Ranvier to the next, producing rapid conduction of the nerve impulse
What can only take place at the gaps on the myelin sheath that occur at the nodes of Ranvier?
Depolarization in the myelinated axons
What is called salatory conduction?
the depolarization wave is skipping from one node to the next - accelerating the rate at which the depolarization wave moves from the neuron cell body to the other end of the axon
What is synaptic transmission?
the perpetuation of the nerve impulse form one neuron to the next
The 2 adjacent neurons do not physically touch each other, the neuron must release a _______ that stimulates the next neuron or cell.
What is the junction between 2 neurons or a neuron and target cells?
The synapse consists of a physical gap between the 2 cells
What is the presynaptic neuron?
it is the neuron bringing the depolarization wave to the synapse and releasing the chemical to stimulate the next cell
What is the neurotransmitter?
the chemical released by the presynaptic neuron
At the end of the axon on the presynaptic neuron, there is a branched structure called the ...?
What is the terminal bouton, synaptic end bulb, or synaptic knob?
a slightly enlarged bulb that is at the end of each branch of the telodendron
What is the postsynaptic neuron?
the neuron that contains the receptors that received the nerotransmitter
What does the synaptic knob contain?
many mitochondria (provides energy for the process that occur), and many vesicles (small sacs that contain the neurotransmitter)
What happens when the depolarization wave reaches the synaptic knob?
Calcium channels open in the knobs cellular membrane - influx of Ca into the synaptic knob which causes the neurotransmitters to fuse with knobs cellular membrane and dump their contents into the synaptic cleft. Then the neurotransmitters diffuse rapidly across the short synaptic cleft toward the postsynaptic membrane
On the postsynaptic membrane are specialized proteins called ...?
What are receptors?
What happens with these receptors?
The neurotransmitter molecules released by the synaptic knob bind with these receptors and trigger a change in the post synaptic cell. The postsynaptic membrane receptors are very specific about which neurotransmitters they will bind, if they don't match they will not bind to each other and no change will be triggered in the postsynaptic cell
What are the 2 categories that we can classify the neurotransmitters that are associated with both the Central nervous system and the peripheral nervous system?
Excitatory neurotransmitters or inhibitory neurotransmitters
What are excitatory neurotransmitters?
they have an excitatory effect on the postsynaptic membrane when they combine with their specific receptors
Specifically, what does excitatory neurotransmitters cause?
an influx of sodium so that the postsynaptic membrane moves toward threshold
When the postsynaptic membrane is stimulated sufficiently by enough excitatory neurotransmitters, then ...?
threshold will be attained and depolarization of the postsynaptic membrane will occur (-55 threshold)
What is an inhibitory neurotransmitter?
tend to hyperpolarize the postsynaptic membrane, making the inside of the cell more negative instead of positive and moving the charge within the postsynaptic cell farther away from threshold
What happens when inhibitory neurotransmitters combine with their specific receptors on the postsynaptic side?
they may cause chloride channels or potassium channels to open up on the postsynaptic membrane. This allows the negatively charged chlorine ions (Cl) to enter the cell and allows potassium (K) ions to leave the cell, making the inside of the cell more negatively charged (a change in charge that is opposite from that needed to reach threshold)
What are some common neurotransmitters?
Acetylcholine, norepinephrine, epinephrine, dopamine, gamma-aminobutyric acid (GABA) and glycine
What is one of the most commonly studied neurotransmitters in the body?
Is Acetylcholine an (depending on its location in the body):
a) excitatory neurotransmitter
b) inhibitory neurotransmitter
At the junction between somatic motor neurons and the muscles they supply, acetylcholine is an?
a) excitatory neurotransmitter
b) inhibitory neurotransmitter
At the junction between somatic motor neurons and the muscles they supply, acetylcholine is an excitatory that?
stimulates muscle fibers
At the site where nerves synapse with the heart, acetylcholine has an _________ effect?
a) excitatory effect
b) inhibitory effect
At the site where nerves synapse with the heart, acetylcholine has an inhibitory effect that ....?
slows down the heart rate
Norepinephrine is associated with arousal and _________ reaction of the sympathetic nervous system?
Epinephrine is released primarily from the adrenal medulla (center of the adrenal gland) and therefore plays more of a role as a ___________ in the fight-or-flight reactions of the sympathetic nervous system.
What is found in the brain, where it is involved with automatic functions and muscle control?
__________ is found in the brain, where it is involved with automatic functions and muscle control?
Gamma-aminobutyric acid (GABA) and glycine are two neruotransmitters that are _____?
a) excitatory neurotransmitter
b) inhibitory neurotransmitter
GABA - gamma-aminobutyric acid is found ______?
in the brain
Glycine is found _______?
in the spinal cord
The body needed a way to stop the effect of the acetylcholine neurotransmitter quickly. What is used?
What is acetylcholinesterase?
an enzyme that acts on acetylcholine.
What happens when acetycholine is acted upon by acetylcholinesterase?
the broken down components of acetylcholine are reabsorbed by the synaptic knob, reassembled into new acetylcholine molecules, and repackaged into vesicles for release with the next wave of depolarization.
What happens if acetylocholinesterase is prevented from working?
acetylcholine will not be broken down and acetylcholine receptors will continue to be stimulated.
What happens after the release of norepinephrine from the presynaptic neuron?
the norepinephrine is rapidly taken back into the synaptic knob where it is broken down into its components by the enzyme monoamine oxidase (MAO)
What is monamine oxidase (MAO)?
breaks down norepinephrine
The brain is divided into 4 different sections. What are they?
cerebrum, cerebellum, diencephalon and brain stem
What is the cerebrum?
It is the largest part of the brain. responsible for those functions most commonly associated with higher-order behaviors (learning, intelligence, awareness)
What is the cerebellum?
located just caudal to the cerebrum, is the second largest component of the brain - coordinated movement, balance, posture, and complex reflexes
What is the diencephalon?
it serves as a nervous system passageway between the primitive brain stem and the cerebrum.
What three structures are associated with the diencephalon?
the thalamus - regulation of sensory inputs to the cerebrum
the hypothalamus - master of endocrine system
Pituitary - hormone production - releases chemical messengers
What is the brain stem's purpose?
to maintain basic support functions of the body, so it operates at the subconscious level
What is cerebrospinal fluid?
a fluid - we have it
What is the blood-barrier?
is a functional barrier separating the capillaries in the brain from the nervous tissue itself - brain is protected
also cellular barrier that prevents many drugs, proteins, ions, and other molecules from readily passing from the blood into the brain
What is the autonomic nervous system?
controls many functions of the body at a subconscious level
The automatic functions of the autonomic system are performed by two divisions, what are they?
sympathetic nervous system and the parasympathetic nervous system
These two system generally have opposite effects on organs or tissues, and whichever system dominates at any given moment determines the state of the organ systems
The sypathetic nervous system is often called?
fight-or-flight system - helps the body cope with emergency situations
The parasympathetic nervous system could be called?
rest-and-restore system because of its ability to decrease the strong excitatory effects of the fight-or-flight system
What are the effects of the heart rate in the sympathetic system and the parasympathetic system?
increases in sympathetic system and decreases in the parasympathetic system
What can reflexes be?
somatic reflexes - involve contraction of skeletal muscles
autonomic reflexes, which regulate smooth muscle, cardiac muscle, and endocrine glands
If the motor neuron is a somatic neuron, the reflex arc ends in ....?
contraction or inhibition of skeletal muscle.
If it is an autonomic neuron, the reflex arc ends in ....?
smooth muscle within an organ or blood vessel, cardiac muscle, or endocrine gland - bodies response
What is the stretch reflex?
a simple, monosynaptic or two-neuron reflex arc because it involves only a sensory neuron, a motor neuron, with out any interneurons
What is crossed extensor reflex?
reflex initiated by a stimulation of a limb that results in extension of the limb on the other side of the body
What is hyperreflexive?
when the vet taps on the patellar ligament, the quadriceps muscles contract with more force and produce more limb movement than normal
What is hyporeflexive?
absent altogether - the arc is damaged or broken anywhere the reflex will either not function or it will function weakly