Test 2 (The Nervous System and Synapses) Flashcards
Glands communicate with, integrate and control organs by secreting hormones into the blood
Endocrine system
Brain, spinal cord and nerves communicate, integrate and control body functions with nerve impulses
Nervous system
Brain+Spinal Cord
Control+Integration
Central Nervous System
Cranial nerves and spinal nerves
Communication
Peripheral Nervous System
Carries nerve impulses via eletrical signals
Neurons
Support, protect and nourish neurons and is a majority of nerve tissue cells
Neuroglia
What are the structures of a neuron?
Cell body, dendrites, axon
Contains nucleus and other organelles
Cell body
Branched extensions of the cell body that carry impulses toward the cell body
Dendrites
Long extension of cell body, beginning with the axon hillock and ending in synaptic/axon terminal with synaptic knobs/vesicles and carries impulses away from cell body
Axon
Increases the speed of impulse conduction and makes the process of sending impulses more energy efficient
myelin sheath
Made of neuralgia cells called Schwann cells wrapping around the axon
PNS myelinated neurons
Sheath made of oligodendrocytes that wrap around an axon
CNS myelinated neurons
3 types of neurons
afferent, efferent, association neurons
Carries impulses from receptors in the PNS to the CNS
sensory (afferent) neurons
Carries impulses from the CNS to the muscles and glands
motor (efferent) neurons
Carries impulses within the CNS and relays impulses from the sensory neurons to the motor neurons
Association neurons
Carries impulses from the CNS to the muscles and glands
motor (efferent) neurons
carries impulses within CNS- relay impulses form the sensory neurons to the motor neurons
Association neurons
What are the types of neuralgia cells?
Schwann cells Oligodendrocytes Astrocytes Microglia Ependymal cells
Form the blood-brain barrier
Astrocytes
Phagocytosis to prevent infection
Microglia
Works in cerebrospinal fluid circulation
Ependymal cells
Cells that form a regeneration tube that eventually becomes functional again
Schwann cells
When these axons are cut, the severed distal portion regenerates
PNS neuroglial cells
How do neuralgia cells function in blood brain barrier
Separate the brain from the circulatory system
Steps to protect blood brain barrier
Prevent toxic substance from entering CNS
- Endothelial cells line capillaries in brain fit tightly together, making diffusion much more difficult
- Astrocyte feet surrounding the endothelial cells and their secretions also provide a physical barrier
Not transmitting an impulse
resting neuron
What is polarization like in resting membrane potential
Electrical charge on the outside of the membrane is positive while the electrical charge on the inside of the membrane is negative
The difference/imbalance in electrical charges
Testing potential (~70mV)
Where is the greatest Na+ concentration in membrane potential
Outside of the membrane
Membrane potential other than 0mV
Polarization
Less negative than resting membrane potential
Depolarization
Membrane returns to resting potential after depolarization
Repolarization
More negative than resting membrane potential
Hyperpolarization
How is Ionic imbalance brought about?
Sodium-Potassium pumps out more + ions than it brings in
Channels that are always open
Leaky/nongated
Channels that are open for specific ions
Gated
- ligand-gated
- voltage-gated
Group of transmembrane ion channel proteins which open to allow ions to pass through the membrane in response to the binding of a chemical messenger, such as a neurotransmitter
Ligand-gated`
Changes in membrane potential cause channel to open
Voltage-gated
What are the two types of K+ channels
not gated
voltage gated
Types od Na+ channels
Voltage gated (open ~55mV)
What happens when a nerve cell “fires”?
An electrical signal moves down the neuron
Electrical signals are produced by changes in ion concentrations
Alter ion concentrations by altering ion permeability
Produced by a specific change in the environment acting on a specific region or portion of the cell membrane
Graded potential
What does the magnitude of graded potential depend on?
Strength and frequency of the stimulus
A brief, rapid, large change in membrane potential, causing it to reach its threshold
Action potential
The critical level to which a membrane must be depolarized for an action potential to occur
Threshold potential
The neuron either propagates an impulse of does not at all
“All of none law”, which action potential follows
Where does action potential begin?
Axon hillock
A period following stimulation during which a cell is unresponsive to further stimulation
Refractory period
The period of time after a nerve has fired an action potential during which another AP cannot be fired, no matter how strong the stimulus
Absolute refractory period
The period of time after a nerve has fired an action potential (and after the absolute refractory period) during which another AP cannot be fired with the threshold stimulus, but larger than threshold stimulus can be fired
Relative refractory period
How does action potential propagate unmyelinated axons
AP opens voltage gated Na+ channels
Serves as stimulus for depolarization of next adjacent region, triggering an AP at the segment
AP produced continuously along plasma membrane or unmyelinated axons
Gaps in between either Schwann cells or Oligodendrocytes
Ranvier
How does action potential propagate in myelinated axons
Impulses bounce from one Ranvier to the next, avoiding the myelin sheath and speeding u the impulse (saltatory conduction)
Why is saltatory conduction faster?
myelinated axon have voltage-gated channels ONLY at the nodes of ranvier as as opposed to the entire length
Communication junction between a neuron and either another neuron or a muscle or gland cell
synapse
Stimulates physiological change
synapse
What are the two types of synapse
Chemical
Electrical
Chemical messenger is transmitted across the junction separating the neurons
Chemical synapse
Two neurons are connected by gap junction
Electrical synapse
what is the anatomy of a synapse
Presynaptic neuron
Synaptic cleft
Postsynaptic cell
What is the chemical sequence of synapse function
AP triggers Ca2+ channels in axon terminal
Ca2+ rushes in
Ca2+induced exocytosis of synaptic vesicles
Neurotransmitter diffuses across synaptic cleft and binds to receptors on postsynaptic cell membrane
Substance that binds to a receptor
Ligand
Specific ligand-gated ion channels in postsynaptic cell membrane
Chemical synapse
What are two possible types of synaptic potential
Excitatory postsynaptic potential
Inhibitory postsynaptic potential
Post synaptic cell membrane depolarizes and Increases the chances of a post-synaptic action potential occurring
Excitatory postsynaptic potential
Postsynaptic cell membrane is hyper polarized and decreases the changes of a post synaptic action potential occurring
Inhibitory postsynaptic potential
Excitatory neurotransmitter that stimulates muscles
Acetylcholine
Inhibitory neurotransmitter that stops the excitatory neurotransmitters that lead to anxiety
Gamma-Aminobutyric acid
Valium enhances GABBA
Inhibitory neurotransmitter that regulates mood
serotonin
Excitatory neurotransmitter that brings the NS to high alert
Norepinephrine/epinephrine- excitatory
What does the firing of a postsynaptic neuron depend on?
the number of active synapses
whether the synapses are excitatory or inhibitory
