MCAT Biology - The Nervous System

Neurons

Specialized cells capable of transmitting electrical impulses and then translating those electrical impulses into chemical signals

Action Potentials

Transmission of electrical impulses down the axon

Soma

Cell body, location of endoplasmic reticulum and ribosomes

Dendrites

Recieve incoming messages from other cells

Axon Hillock

Integrate incoming cells

Axon

Long appendage that terminates in close proximity to target structure

Myelin

Prevent signal loss or crossing signals

Myelin Sheath

Maintain electrical signal within one neuron

Oligoendrocyte

Produce myelin in CNS

Schwann Cell

Produce mylein in PNS

Nodes of Rainver

Critical for rapid signal conduction

Nerve terminal/synaptic bouton

Maximize transmission of signals to the next neuron and ensure proper release of neurotransmission

Synaptic Cleft

Space between neuron in whcih the terminal portion of axon releases neurotransmitters, when bind to dendrite of adjacent neuron

Synapse

Nerve terminal, synaptic cleft and post synaptic membrane

Tracts

Axon bundled together and only carry one type of information

Nuclei

Cell bodies of neuron in same tracts are grouped (In CNS)

Ganglia

Ganglia In PNS cell bodies of neurons of same type with a nerve cluster together

Glial Cell/neuroglial

Other cell in nervous system in addition to neurons

Astrocyte

Nourish neuron and form blood brain barrier, which control transmission of solute from bloodstream into nervous tissue

Ependymal Cells

Line the ventriale of the brain and produce cerebrospinal fluid, which physically supports the brain and serves as schock absorber

Microglia

Phagocytic cells that ingest and break down waste products and pathogen in CNS

Oligodendrocyte

Produce myelin around axon (CNS)

Schwann Cell

Produce myelin around axon (PNS)

Action Potential

An abrupt change in the membrane potential of a nerve or muscle caused by changes in membrane ionic permeability, results in conduction of an impulse in nerve or contraction in muscles

Resting Membrane Potential

Net electric potential differecne that exists across the cell membrane, created by movement of charged molecules across the membrane

Resting membrane potential of Neurons

-70mV

Resting membrane potential of Sodium

60mV

Resting membrane potential of Calcium

-90mV

Equilibrium potential of potassium

The potential difference that represents the equilibrium within the cell

Sodium leak channels

Facilitate movement of pushing Na into cell

Na/K ATPase

Continually pumps sodium and potassium back to where they started

Depolarization

Raising the membrane potential from its resting potential

Hyperpolarization

Raising the membrane potential from its resting potential

Summation

Additive effects of multiple signals

Temporal Summation

Multiple signals are integrated during a relatively short period of time

Spatial Summation

The additive effects are based on the number and location of incoming signals

Sodium Ion Channel (Closed)

Before the cell reaches threshold and after inactivation has been reversed

Sodium Ion Channel (Open)

From threshold to approximately +35mV

Sodium Ion Channel (Inactive)

approxiamtely +35mV to resting potential

Repolarizaiton

Restoration of negative memrane potential

Absolute refractory period

No amount of stimulation can cause another action potential to occur

Relative Refractory period

Greater then normal stimulation to cause an action potential

Impulse Propagation

Movement action potential travel down axon and initiate neurotransmitter

Saltatory Conduction

Hops form node to node

Presynaptic Neuron

Neuron preceeding the synaptic cleft

Postsynaptic neuron

Neuron after the synaptic cleft

Effector

If neuron signals to a gland or muscle rather than around another neuron

Sensory Afferent Neuron

Transmit sensory info from sensory receptor to spinal cord and brain

Motor/Efferent Neuron

Transmit motor info from brain and spinal cord o muscle and gland

Interneuron

Found between other neurons

Central Nervous System

Composed of brain and spinal cord

White matter

Consists of axons encased in myelin sheaths

Grey Matter

Consists of unmyelmated cell bodies and dendrites

Vertebral Column

Transmits nerves at the space between adjacent vertebrae

Peripheral Nervous System

Made of nerve tissues and fibers outside the brain/spinal cord including all 31 pairs of spinal nerves

Somatic Nervous System

Consists of sensory and motor neurons distributed throughout the skin joints and muscles

Automatic Nervous System

Manages involuntary muscles associated wiht many internal organs and glands

Monosynaaptic Reflex

There is a single synapse between the sensory neurons that recieves the stimulus and motor neuron that responds to it

Polysynaptic reflex arc

At least one interneuron between sensory and motor neurons

Parasympathetic Nervous System

Conserve energy

Sympathetic Nervous System

Activated by stress