Bio 4- Nervous System

The resting membrane potential is -__mV for the average nerve cell b/c K+ movement pulls the cell potential toward -__mV, while Na movement pulls the cell potential the opposite way toward +__mV -The resting potential is closer to K's equilibrium potential b/c the cell is slightly more permeable to K+.

-70mV -90mV K +60mV Na

Na concentration gradient is the reverse if K+, with a concentration of about __mV inside and ___mV outside the cell meaning there is a driving force pushing Na into the cell. -The movement is facillitated by sodium leak channels. The slow leak of Na into the cell causes a build up of electric potential. -The equilibrium potential of sodium is around __mV and is positive b/c Na is moving into the cell.

12mV inside; 145mV outside; 60mV equilibrium

The K+ content inside the cell averages around ___mV compared to _ mV extracellularly, making it favorable for K+ to move outside the cell. ______ leak channels allow a slow leak of K+ out of the cell to help facilitate the outward movement of K+. -This causes the cell to lose a small amount of positive charge leave and leave behind a small negative charge, making the outside of the cell slightly + The potential difference that causes potassium equilibrium is called the equilibrium potential of potassium. K+ equilibrium potential is around -__mV, and is negative due to the positive K+ ions moving out of the cell.

14mV & 4mV; potassium leak channels; -90mV

Neuron structure: _____ are appendeges that recieve incoming signals from other cells. The cell body or ____ is the location of the nucleus as well as organelles such as the ER & ribosomes sums inhibitory or excitatory signals and can fire action potentials (transmission of electrial impusles down the axon). The axon _____ is where the cell body transitions to the axon, and where action potential travels to a terminal target (gland, muscle, or other neuron). Nerve fibers are insulated by _____ to prevent loss of crossing of signals, which also increases the speed of conduction. Myelin in produced by ___________ in the CNS and _____ cells in the PNS The ____ sheath maintains the electrical signal within one neuron.

Dendrites; soma; axon hillock; myelin; oligodendrocytes; schwann cells; myelin sheath; nerve terminal or synaptic bouton

Multiple neurons are bundled together to form a ____ in the PNS. These may be sensory, motor, or mixed which refers to the type of info they carry. The cell bodies of neurons of the same type are clustered together into ______. In the CNS, axons may be bundled together to form ____. Unlike nerves, these only carry one type of info. The cell bodies of neurons in the same tract are grouped together into _____.

Nerves; ganglia; tracts; nuclei

Cells of the nervous system: ____ cells (neuroglia) are other cells within the nervous system in addition to neurons that play structural and supportive roles. ______ nourish neurons and form the blood-brain barrier, which controls the transmission of solutes from the bloodstream into nervous tissue. ______ cells line the ventricles of the brain and produce cerebrospinal fluid, which physically suports the brain and serves as a shock absorber. ______ are phagocyctic cells that ingest and break down waste products and pathogens in the CNS. ________ (CNS) and _____ cells (PNS) produce myelin around axons

Neuroglia or glial cells; Astrocytes; Ependymal cells ; Microglia; Oligodendrocytes & Schwann cells

______ are highly specialized cells responsible for the conduction of impulses. They communicate using both electrical & chemical forms of communication. -Chemical communication occurs via _________ release from the __-synaptic cell and the binding of these transmitters to the ___-synaptic cell.

Neurons; neurotransmitters; presynaptic; postsynaptic

Neuron structure: _____ of Ranvier are exposed areas of myelinated axons that permit salatory conduction The ____ terminal or synaptic ____ is the end of the axon from which neurotransmitters are released. The ____ consists of the nerve terminal of the presynaptic neuron, the membrane of the postsynaptic cell, and the space between the two, called the synaptic ____.

Nodes of Ranvier; Nerve terminal or synaptic bouton (knob); synapse; synaptic cleft

There are two types of summation: _______ summation refers to the addition of mutiple signals near each other in a short period of time. ecx. _______ summation refers to the addition of multiple signals in space (location)

Temporal summation; Spatial summation

Axons carry neutral signals _______ from the soma; Dendrites carry signals __________ the soma.

away toward

Na channels can exist in 3 states: _____ (before the cell reached threshold & after inactivation has been reversed) _____ (from threshold to approximately +35mV) _____ (from +35mV to the resting potential) Threshold =-55 to -40mV

closed; open; inactive

Incoming signals can be excitatory or inhibitory: Excitatory signals cause _______ of the neuron, which raises the membrane potential, Vm, making it more likely to fire an action potential. Inhibitory signals cause _______ of the neuron, which lowers the membrane potential from its resting potential and making it less likely to fire an action potential

depolarization; hyperpolarization

An action potential is used to propagate signals down the axon. When enough excitation stimulation occurs, the cell is _______ to the threshold voltage and voltage-gated Na channels open. -Na flows into the neuron due to its strong electrochemical gradient, which continues depolarizing the cell. -At the peak of the action potential (+__mV), __ channels are closed and __ channels open -K+ flows out into the neuron due to its strong electrochemical gradient, _________ the cell. K+ channels stay open long enough to overshoot the action potential, resulting in a _________ neuron, then the K+ channels close. -The Na+K+ ATPase brings the neuron back to its resting potential and restores sodium & potassium gradients.

depolarized; +35mV, Na+, K+; repolarizing; hyperpolarized

Individual axons are bundled in to Nerves or Tracts. - A single nerve may carry multiple types of info, including sensory, motor, or both. Tracts contain only one type of info. - Cell bodies of neurons of the same type within a nerve cluster into _____ in the PNS - Cell bodies of the individual neurons within a tract cluster into _____ in the CNS

ganglia; nuclei

The impusle propagates down the length of the axon b/c the influx of Na in one segment of the axon brings the subsequent segment of the axon to threshhold. The fact that the preceding segment of the axon is in its refractory period means that the action potential can only travel in one direction.

impulse propagation

In Multiple sclerosis (MS), the immune system attacks _____ which slows information transfer in nerves.

myelin

Na+ wants to go into the cell because the cell is more ______ inside (electrical gradient) and has a _____ concentration of Na+ inside (chemical gradient)

negative; lower

While the axon is hyperpolarized, it is in its _______ period. (two types) During the ______ refractory period, the cell is unable to fire another action poteintial and no amount of stimulus can cause it to occur. During the ______ refractory period, the cell requires a larger than normal stimulus to fire an action potential b/c the membrane is starting from a potential that is more negative than its resting value.

refractory period; absolute refractory period; relative refractory period

All neurons exhibit a _____ membrane potential of -__mV with the inside of the neuron being negative relative to the outside. -Resting potential is maintained using selective permeability of ions as well as the __+/_+ ATPase -The Na+/K+ ATPase pumps _ Na+ ions out of the cell for every _ K+ ions pumped in.

resting membrane potential; -70 mV; Na+/K+ ATPase; 3 Na+ for every 2 K+

There is a small space btwn neurons called the synaptic ____ into which neurotransmitters are secreted. The neuron preceding the synaptic cleft is called the ___-synaptic neuron. The neuron after the synaptic cleft is called the ___-synaptic neuron. If the neuron signals to a gland or muscle rather than another neuron, the post synaptic cell is termed an _____. Most synapses are chemical, and use _________ to send messages from one cell to the next.

synaptic cleft; pre-synaptic neuron; post-synaptic neuron; effector; neurotransmitters

If the axon hillock receives enough excitatory input to be depolarized to the ______ value (-55mV to -40mV), an action potential will be fired. The additive effect of multiple signals is known as ____, and can lead to an action potential or cause one to not occur.

threshold; summation