Unit III: The Nervous System (2) Flashcards
What is the refractory period, and when does it occur?
The plasma membrane does not respond normally to additional depolarization stimuli from when an action potential begins until the resting membrane potential has been reestablished.
*It begins when the voltage-gated- sodium ion channels open at the threshold.
What is meant by the propagation of action potential?
The action potential spreads along the surface of an axon and does not diminish as it moves from its source.
The rate of the propagation of action potential is determined by what?
Axon diameter and presence of myelin sheaths.
Continuous Propagation
*No myelin sheaths.
*Action potentials are much slower
*Action potential spread by depolarizing the adjacent region of the axon membrane.
Saltatory Propagation
Term for impulse conduction over myelinated axons.
Action potentials jump from one node to the next.
Action potentials are faster.
Myelin limits the movement of ions across the axon membrane.
Synapse
The junction between the processes of two neurons or between a neuron and effector organ, where neural impulses are transmitted by chemical means.
What happens when an action potential reaches the axon terminal of the postsynaptic neuron?
Calcium flows in, and vesicles with neurotransmitters move and are released from the last nerve into the synaptic cleft to transmit the signal to the next neuron
Goes from a electrical to chemical
Gray matter
Nuclei
Neural Cortex (outer layer of the cerebral cortex)
White Matter
Axons with myelin.
(white matter tracts) link with nuclei in other regions of the brain.
With neurons of the neural cortex and spinal cord.
Cerebrum
Can be separated into right and left.
Conscious thoughts, sensations, intellect, memory, and complex movements all originate from here.
Largest part of the brain.
3 parts of the brain stem
Midbrain, pons and medulla oblongata
What protects the brain?
The skull, meninges, cerebrospinal fluid, and blood-brain barrier.
What are the three layers of meninges?
Dura mater, arachnoid mater, and pia mater.
Dura Mater
Tough sheath, the most outer layer of the three. Has two- periosteal and meningeal.
Pia mater
Thin clings to the first layer of brain tissue.
Arachnoid Mater
Middle layer, made of collagen and elastin.
Cerebrospinal Fluid
Works as a liquid shock absorption, watery cushion, and chemical balance environment for the brain. It is continuously circulating.
Blood-Brain Barrier
A stable chemical enviornment contains astrocytes.
Where is CSF formed? Where is it located?
Choroid Plexus
It circulates through cavities in the ventricles of the brain and central canal.
What substances can and cannot pass through the blood-brain barrier?
Can: Small lipid-soluble molecules, such as alcohol, respiration gases, nicotine, and certain anesthetics.
Cannot: Water-soluble molecules, such as proteins
What are the effects of stress on the blood-brain barrier?
It makes the BBB leaky and sensitive to substances.
What is the cerebral cortex?
The surface of the cerebral hemisphere that is highly folded and covered by a collection of neurons that form a thin superficial layer of gray matter.
What are the functions of the cerebrum?
Interprets all sensory information.
Conscious thought process.
Intellectual functions.
Memory storage and subconscious regulation of skeletal contractions.
Where is the cerebral cortex located?
The outermost layer of the brain.
