Chapter 6 Human Physiology

Equilium

________ is reached when the concentration gradient pushing sodium in is equal to the electrical gradient that pushes sodium out.

chemical gradient

A(n) ________ exists for certain diffusible ions, which causes charge to move across the cell membrane.

Sodium

________ and calcium are likely depolarizing ions.

Myelination

________ occurs to insulate the axons (prevent ion leakage) and speed up conduction velocity.

Backwards propagation

________ is prevented by the refractory period.

ion channels

Voltage- gated ________ are required for an excitable membrane (aka a membrane that can do an action potential)

K+ gradient

The [________ tends to create membrane potential of- 90 mV.

membrane potential

At rest, a(n) ________ is polarized (is negative at resting)

Na+ gradient

The [________ tends to create membrane potential of +60 mV.

neuron

The ________ is made up of the cell body, debdrites, and axon.

Velocity of action potential propogation

________ depends on axon diameter (larger= faster) and myelination (more= less conduction)

Equilium

________ is reached when the concentration gradient pushing out potassium is equal to the electrical gradient that pushes sodium in.

Potassium

________ and chloride are likely hyperpolarizing ions.

Sodium

________ is in much higher concentrations outside of the cell because of ion pumps.

Interneurons

________ are all part of the CNS.

Axon

________ collateral branches: The extra branching on the ________ of a neuron.

Central Nervous System

Brain and spinal cord

Peripheral Nervous System

Nervous structures that arent the brain and spinal cord

Soma

The cell body of the neuron that includes the nucleus and organelles

Dendrites

The spikes of a neuron that increase receiving surface

Axon

The main stem of a neuron that carries output "message" to target cells

Initial segment

The beginning of the stem of the neuron, part of the axon

Axon collateral branches

The extra branching on the axon of a neuron

Axon terminals

The ending "base" of the axon of the neuron; also valled varicosities

Muelination

20 to 200 layers of modified plasma membrane, formed by glial cells

Glial cells

Non-neuronal cells (i.e

Oligodendrocytes

The glial cells of the CNS

Schwann Cells

The glial cells of the PNS

Nodes of Ranvier

specialized axonal segments that lack myelin, allowing the saltatory conduction of action potentials

Afferent neurons

Neurons that relay sensory information to the CNS

Efferent neurons

Neurons that relay commands away fron the CNS

Interneurons

Neurons that connect afferent and efferent neurons

Synapse

The junction between two neurons

Presynaptic neuron

The neuron that releases a neurotransmitter

Postynaptic neuron

The neuron that receives a neurotransmitter

Membrane potential

Charge inside the cell relative to the extracellular fluid

Graded potential

Local change in membrane potential due to the opening/closing of ion channels, takes place in the dendrites and the cell body (recieving parts)

Spatial summation

many graded potentials located close together on a neuron

Temporal summation

Multiple, repeated graded potentials coming from the same source over a short period of time

Refactory periods

Times during which it is difficult or impossible to fire a second action potential at a point on the neuron

Absolute refactory period

The period from the firing of the action potential to repolarization

Relative refractory period

The period from repolarization to the end of after-hyperpolarization