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