Chapter 4: The Nervous System Flashcards
Astrocytes form the __________ which controls the transmission of solutes from the bloodstream into nervous system
Blood Brain Barrier
Ependymal cells lines the ventricles of the brain and produce __________ , which physically supports the brain and serves as a shock absorber.
Cerebrospinal fluid
Microglia are __________ cells that ingest an break down waste products and pathogens in the central nervous system.
Phagocytic cells
__________ (CNS) and ____________ (PNS) produce myelin around axons.
Oligodendrocytes and Schwann cells
_________ are specialized cells capable transmitting electrical impulses and then translating those electrical impulses into chemical signals.
Neurons
________ = neuron cell body
Soma
The neutron has many appendages emanating directly from the soma called _________
Dendrites
The information received from the dendrites is transmitted through the cell body before it reaches the __________, which integrates the incoming signals.
Axon hillock
The axon hillock plays an important role in ___________, or the transmission of electrical impulses down the axon.
Action potential
The ________ is a long appendage that terminates in close proximity to a target structure (a muscle, a gland, or another neutron).
Axon
Most mammalian nerve fibres are insulated by _________, a fatty membrane, to prevent signal loss or crossing of signals.
Myelin
Just like insulation prevents wires next to each other from accidentally discharging each other, the ____________ maintains the electrical signal within one neuron. It also increases the speed of conduction in the axon.
Myelin sheath
There are small breaks in the myelin sheath with exposed areas of axon membrane called __________
Nodes of Ranvier
At the end of the axon is the ___________ or ____________ (knob)
Nerve terminal or synapsing bouton
______________ are the chemicals that transmit information between neuron.
Neurotransmitters
Between neuron, there is a small space called _________ into which the terminal portion of the axon releases neurotransmitters, which bind to the dendrites of the adjacent neuron (postsynaptic neuron)
Synaptic cleft
Together, the nerve terminal, synaptic cleft, an postsynaptic membrane are known as a ________
Synapse
Multiple neurons may be bundled together to form a _________ in the peripheral nervous system.
Nerve
Nerves in the PNS can be identified as __________, __________, or mixed.
Sensory, motor
The cell bodies of the same nerve type (sensory, motor, or mixed) are clustered together into _________ in the PNS.
Ganglia
In CNS, axons may be bundled together to form _________.
Tracts
The cell bodies of neurons in the same tract of the CNS are grouped into _________.
Nuclei
Astrocytes, ependymal cells, and microglia are types of ___________ or ____________
Glial cells or neuroglia
Neurons use all-or-nothing messages called ___________ to relay electrical impulses down the axon to the synaptic bouton.
Action potentials
A cell’s ______________ is the net electric potential different that exists across the cell membrane, created by movement of charged molecules sodium and potassium across the membrane.
Resting membrane potential
To facilitate the outward movement of potassium K+, the cell membrane has transmembrane _________________, which allows the slow leak of potassium out of the cell.
Potassium leak channels
_____________ is when there is no net movement of the potassium ion, as the cell is in equilibrium with respect to potassium (inside and outside of cell).
Equilibrium potential of potassium (around -90 mV)
The slow leak of sodium Na+ into the cell, which causes a build-up of electric potential is facilitated by _____________
Sodium leak channels
___________ is when there is no net movement of sodium ions, as the cell is in equilibrium after sodium moves into the cell.
Equilibrium potential of sodium (around +60 mV)
_____________ continually pumps sodium out of the cel and potassium into the cell to maintain their respective gradients, if a resting potential is to be maintained.
Na+/K+ ATPase
Sodium/Potassium ATPase
Excitatory input causes ___________ (raising the membrane potential, Vm, from its resting potential) and thus makes the neuron more likely to fire an action potential.
Depolarization
Inhibitory input causes ____________ (lowering the membrane potential from its resting potential) and thus makes the neuron less likely to fire an action potential.
Hyperpolarization
If the axon hillock receives enough excitatory input to be depolarized to the __________ value (usually in the range of -55 mV to -40 mV), an action potential will be triggered.
Threshold value
The additive effect of multiple signals (excitatory + inhibitory) is known as ___________
summation
There are 2 types of summation: ____________ and ___________.
Temporal and spatial
In ___________, multiple signals are integrated during a relatively short period of time.
Temporal summation
In ___________, the additive effects are based on the number and location of the incoming signals.
Spatial summation
The voltage-gated sodium channel is __________ before the cell reaches threshold, and after inactivation has been reversed).
Closed
The voltage-gated sodium channel is __________ from threshold to approximately +35 mV.
Opened
The voltage-gated sodium channel is __________ from approximately +35 mV to the resting potential
Inactive
As positively charged potassium cations are driven out of the cell, there will be a restoration of the negative membrane potential called ______________
Repolarization
During the ___________ refractory period, no amount of stimulation can cause another action potential to occur.
Absolute refractory period
During the ___________ refractory period, there must be greater than normal stimulation to cause an action potential because the membrane is starting from a potential that is more negative than its resting value.
Relative refractory period
For a signal to be conveyed to another neuron, the action potential must travel down the axon and initiate neurotransmitter release. This movement is called ____________
Impulse propagation
__________ is an extraordinarily good insulator, preventing the dissipation of the electric signal.
Myelin
The myelin insulation is so effective that the membrane is only permeable to ion movement at the nodes of Ranvier. Thus, the signal “hops” from node to node - what is called _____________
Saltatory conduction
The neuron preceding the synaptic cleft is called the _____________
Presynaptic neuron
The neuron after the synaptic cleft is called the _____________
Postsynaptic neuron
If a neuron signals to a gland or muscle, rather than another neuron, the postsynaptic cell is termed an ___________
Effector
When the action potential reaches the nerve terminal, voltage-gated __________ channels open, allowing __________ to flow into the cell. This sudden increase in intracellular __________ triggers fusion of the membrane-bound vesicles with the cell membrane at the synapse, causing exocytosis of the neurotransmitters.
Calcium
If the receptor is a ____________, the postsynaptic cell will either be depolarized or hyperpolarized.
Ligand–gated ion channel
If the postsynaptic receptor is a _____________, it will cause either changes in the levels of cyclic AMP (cAMP) or an influx of calcium.
G protein-coupled receptor
Neurotransmitters can be broken down by enzymatic reactions. For example, acetylcholine (ACh) neurotransmitters can be broken down by ______________ to be removed from the synaptic cleft.
Acetylcholinesterase
Neurotransmitters can be brought back into the presynaptic neuron using ______________. Examples are serotonin (5-HT), dopamine (DA) and norepinephrine (NE).
Reuptake carriers
_____________, a gaseous signalling molecule, can simply diffuse out of the synaptic cleft.
Nitric oxide (NO)
_____________ neurons (also known as _____________ neurons) transmit sensory information from sensory receptors to the spinal cord and brain.
Sensory, afferent
_____________ neurons (also known as _____________ neurons) transmit motor information from the brain and spinal cord to muscles and glands.
Motor, efferent
_____________ are found between sensory and motor neurons, and are the most numerous of the three types. They are located predominantly in the brain and spinal cord ad are often linked to reflexive behaviour.
Interneurons
The ______________ is composed of the brain and spinal cord.
Central nervous system (CNS)
The ______________ consists of axons encased in myelin sheaths.
White matter
The ______________ consists of unmyelinated cell bodies and dendrites.
Grey matter
At the base of the brain is the ___________, which is largely responsible for basic life functions such as breathing.
Brainstem
The spinal cord extends downward from the brainstem and can be divided into 4 regions: _________, __________, ___________, and __________.
Cervical, thoracic, lumbar and sacral
The spinal cord is protected by the ____________, which transmits nerves at the space between adjacent vertebrae.
Vertebral column
The sensory neurons bring information in from the periphery and enter the dorsal (back) side of the spinal cord. The cell bodies of these sensory neurons are found in the ______________.
Dorsal root ganglia
The __________________ is made up of nerve tissue and fibers outside the brain and spinal cord, including all 31 pairs of spinal nerves and 10 of the 12 pairs of cranial nerves (the olfactory and optic nerves are technically outgrowths of the CNS)
Peripheral nervous systems (PNS)
The ____________ consists of sensory and motor neurons distributed throughout the skin, joints, and muscles.
Somatic nervous system
__________ neurons transmit information through afferent fibers.
Sensory neurons
__________ neurons travel along efferent fibers.
Motor neurons
The ______________ generally regulates heartbeat, respiration, digestion, and glandular secretions.
Autonomic nervous system (ANS)
A motor neuron in the __________ nervous system goes directly from the spinal cord to the muscle without synapsing.
Somatic nervous system
In the ___________ nervous system, 2 neurons work in series to transmit messages from the spinal cord.
Autonomic nervous system
The first neuron in the autonomic nervous system that helps transmit messages from the spinal cord is known as the _______________ neuron.
Preganglionic neuron
The second neuron in the autonomic nervous system that helps transmit messages from the spinal cord is known as the _______________ neuron.
Postganglionic neuron
The main role of the ______________nervous system is to conserve energy.
Parasympathetic nervous system
______________ is the neurotransmitter responsible or parasympathetic responses in the body and is released by both preganglionic and postganglionic neurons.
Acetylcholine
The __________ nerve (cranial nerve X) is responsible for much of the parasympathetic innervation of the thoracic and abdominal cavity.
Vagus nerve
The _____________ nervous system is activated by stress.
Sympathetic nervous system
In the sympathetic nervous system, the preganglionic neurons release ______________ neurotransmitter.
acetylcholine
In the sympathetic nervous system, the postganglionic neurons release ______________ neurotransmitter.
Norepinephrine
Neural circuits called ___________ control reflexive behaviour.
Reflex arcs
In a ___________ reflex arc, there is a single synapse between the sensory neuron that receives the stimulus and the motor neuron that responds to it. An example is the knee-jerk reflex, which may be elicited by swiftly stretching the patellar tendon with a reflex hammer.
Monosynaptic reflex arc
In a ____________ reflex arc, there is at least one interneuron between the sensory and motor neurons. Interneurons in the spinal cord provide the connections from the incoming sensory information to the motor neurons.
Polysynaptic reflex arc
