SG 6: Chap 7 Neurons Flashcards
(41 cards)
What is a nerve?
is a bundle of parallel axons and dendrites that transmit nervous impulses between nerve cells and various parts of the body.
what is a sensory neuron?
it conducts information towards the brain and spinal cord.
what is a motor neuron?
it carries information away from the brain and spinal cord to an effector (muscle or gland)
what is an interneuron?
these are located between the motor and sensory neurons. only found within the brain and spinal cord and account for more than 99% of the body neurons. JOB: integrate and interpret the sensory singnals
What are functions of glial cells ?
Also known as neuroglial cells, some provide structural support for the neurons of the brain and spinal cord, others provide a steady supply of chemicals(nerve growth factor) that stimulates nerve growth, others form insulating sheaths around the axons called myelin sheath (Schwann cells) these cells can communicate w/one another & w/neurons
How do neurons differ from glial cells In Terms of cell division?
Glial cells retain the ability to undergo cell division in adulthood whereas most neurons can’t.
what is the myelin sheath?
composed of the plasma membrane in multiple layers of the glial (schwann) cell, it increases the of conduction of a nerve impulse & helps its repair. it covers most of the axons outside the brain and spinal cord and some w/in.
what is a Schwann Cell?
forms neurons myelin sheaths. insulates individual axons and prevents messages from short circuiting between neurons.
what are the nodes of Ranvier?
the gaps between the Schwann cells, where the axon is exposed. A function is that they allows nutrients and waste to enter and exit the neuron, and facilitate the rapid conduction of the nerve impulses.
what is the gray matter?
is the region of the CNS that contain neuron cell bodies, dendrites and axon terminals and unmyelinated axons.
what is the white matter?
regions of the CNS but mainly PNS that are myelinated nerve fibers(axons). these are important for communication over long distances.
Saltatory conduction function?
is a transmission where with the assistance of myelin sheath in place, a nerve impulse “jumps” successfully from one rode of ranvier to the next. These axons are 100% faster than a single conduction.
what is Multiple Sclerosis?
it is a disease in which the myelin sheaths in the brain and spinal cord are progressively destroyed. Damaged regions of the myelin sheath become hardened scars which interfere w/the transmission of nerve impulses. depending of the region of the nervous system, results can be paralysis, loss of sensation, including loss of vision.
what is ALS ?
short of Amyotrophic Lateral Sclerosis. ALS is a disease in where only motor neurons throughout the brain and spinal cord die and stop sending messages to the skeletal muscles. w/out stimulation from the motor neurons, muscles gradually weaken & person loses control of body movement.
leads to respiratory failure(death) since muscles that control breathing eventually die
What is a Nerve Impulse?
also known as action potential, its an electrochemical signal caused by Na+ ions and K+ ions crossing the neurons membrane to enter and leave the cell.
What are the diff concentrations inside and outside of the cell of Na+ and K+ ions during diff stages?
Resting potential: + in the outside & – in the inside
action potential: – in the outside & + + in the inside
what structures in the plasma membrane participate in the transport of these ions?
gated ions channels and Sodium-Potassium pumps.
what are Ion channels when regarding a Nerve Impulse?
are pores in the neuron membrane that dont need cellular energy to pass through.
Na+ channels & K+ channels
what are Pumps when regarding a nerve impulse?
Na+-K+ pump are special proteins that actively(using cellular energy in form of ATP to move ions across their concentration gradient) transports Na and K ions across the membrane.
pumps out 3 Na+ ions and intakes 2 K+ ions
the pump restores the original levels of charges after action potential took place back to resting potential.
What is “resting potential?” and what is the ions concentration?
is a charge difference across the membrane which results from unequal distribution of ions. no conduction impulse. inside is neg, and outside is positive. Na+ greater in the outside, and K+ greater inside the neuron.
what is action potential? and what is the ion concentration?
or Nerve impulse. is when the neurons receive an ecitatory signal which results in a sudden reversal in the charge difference across the membrane followed by the restoration of the original charge diff. Neg in the outside and positive in the inside.
what happens during depolarization? Depo= deposit
depo= deposit Na+ gated ion channels open and Na+ ions enters which results in the ++ charges increase inside the axon membrane.
what happens during repolarization? repo=take
repo=take about 1/2 way through the action potential, K+ gated ion channels open and K+ ions flow out. as k flows back out, almost returning the charge differences to resting potential.
what is refactory period?
occurs after action potential when neurons cannot be stimulated. Na+ ions channels are closed and cant be opened. inside more neg than outside
