Chapter 11 Nervous System Flashcards
nerve is resetting the Na+ and K levels to original concentrations during this period, not enough concentration gradient has been established, prevents neuron from generating an action potential (absolutely no action potential)
absolute refractory period
almost all of the Na+ and K have been restored, a very strong stimuli could cause depolarization
relative refractory period
-Axon diameter - the larger the diameter, the faster the impulse
-Presence of a myelin sheath - myelination dramatically increases impulse speed
rate of impulse propagation is determined by
current passes through myelinated axon only at the nodes of Ranvier, voltage-gated Na+ channels are concentrated in these nodes, action potentials are triggered only at the nodes and jump from node to node, much faster than conduction along unmyelinated axons
saltatory conduction
destruction of the myelin sheath on neurons in the CNS and its replacement by plaques of sclerotic (hard) tissue, can harm motor control
Multiple Sclerosis (MS)
“voluntary” nervous system innervates skeletal muscle
somatic motor division
“involuntary” nervous system: innervates cardiac muscle, smooth muscle, glands, broken down into sympathetic (speeds up) and parasympathetic (back to normal)
autonomic motor division
Act as phagocytes, eating damaged cells and bacteria, and act as the brain’s immune system
microglia
holds nucleus and nucleolus, focal point of outgrowth of neuronal processes
nerve cell body
Branchlike parts of a neuron that are specialized to receive information, carry impulses toward the cell body
dendrites
Carry impulses away from the cell body, surrounded by myelin sheaths, contacts nerves, muscles, and glands
axons
outside wrap of Schwann cell containing the nucleus and organelles
neurilemma
gaps in the myelin sheath between the adjacent Schwann cells
nodes of ranvier
found in the brain and spinal cord, white is dense collection of myelinated fibers, and gray is mostly soma and unmyelinated fibers
white matter vs gray matter
the state of the neuron when not firing a neural impulse, about -70mv
resting potential
the change in electrical potential associated with the passage of an impulse along the membrane of a nerve cell, Na+ permeability increases
action potential
inside of the cell becomes less negative, Na+ in, greater than -70mv
depolarization
the membrane returns to its resting membrane potential, K out, inside of the cell becomes more negative, returns to -70mv
repolarization
inside of cell becomes more negative than resting potential of -70mv, extra K out, nerve is now less likely to fire
hyperpolarization
caused by frequency of impulse transmission
stimuli intesity
a junction that mediates information transfer from one neuron to another, there is a gap that separates them which is why we need neurotransmitters, neurotransmitter also opens sodium potassium channel
synapses
nerve impulse comes down axon terminal and opens Ca+ channels which releases neurotransmitter, Ca+ comes into the axon terminal to cause the release of neurotransmitters
function of Ca at axon terminal
