BIOL 220 Exam 2 Review - Nervous System

Afferent (Sensory) Neurons

Conducts signals from receptors and transmits them to the CNS. Can be unipolar or bipolar.

Interneurons

CNS neurons that internally communicate and intervene between the sensory inputs and motor outputs. Makes up 99% of all neurons in the body, and are typically multipolar.

Efferent (Motor) Neurons

Conducts signals from the CNS to effectors (muscles & glands). Multipolar

Nerves

Axon bundles of the CNS

Ganglia

Collections of nerve cell bodies, resulting in a knot-like swelling

Somatic Afferent

Collects sensory information from the skin, muscles, and joints

Visceral Afferent

Collects sensory information from internal organs

Somatic Efferent

Controls voluntary movements and automatic reflexes

Autonomic Efferent

Controls involuntary visceral reflexes

Cell Body (Soma)

Contains the nucleus and other parts of the cell needed to sustain its life

False

TRUE or FALSE: Neurons possess centrioles, allowing them to undergo mitosis

Dendrites

Branching heads of neurons that receive electrical impulses

Axon

Tail of neurons that transmit electrical impulses

Terminal Arborizations

Fine terminal branches of an axon

Axon Terminals

Branches at the end of the axon that release neurotransmitters to communicate with other neurons

Axolemma

Specialized plasma membrane surrounding the axon

Axoplasm

Cytoplasm inside a neuron's axon

Axon Hillock

Cone-shaped region in a neuron's soma where action potentials are initiated

Axonal transport

Microtubules guide the transport of organelles, vesicles, and macromolecules

Anterograde Axonal Transport

Transport of materials to the synapse

Retrograde Axonal Transport

Transport of materials to the soma

Neuroglial Cells

Support cells of nervous tissue

Astrocytes (CNS)

Star shaped cells that maintain the environment of nervous tissue, guide developing neurons, facilitate synapse formation, and form scar tissue.

Microglial Cells (CNS)

Small ovoid cells with thorny dendritic branches that phagocytize damaged neurons and pathogens

Ependymal Cells (CNS)

Line cavities of the brain and spinal cord; produce and circulate cerebrospinal fluid

Oligodendrocytes (CNS)

Forms and maintains myelin sheaths of axons

Satellite Cells (PNS)

Protect neuron cell bodies in PNS

Schwann Cells (PNS)

Form myelin sheaths in PNS

Grey Matter

Contains unmyelinated structures

White Matter

Contains myelinated axons

Myelin Sheaths

Layered plasma membrane that increases transmission speed

Node of Ranvier

Gap in myelin sheaths

Neruolemma

Thick, outermost layer of a myelin sheath

Multipolar Neurons

Neuron with one axon and many dendrites; most common type of neuron

Bipolar Neurons

A neuron that has only two projections (one axon/one dendrite) from the cell body

Unipolar Neurons

Neuron that has a single process leading away from the cell body, splitting into a central process (receives sensory input) and peripheral process (transmits to the CNS)

Anaxonic Neurons

Consists of many dendrites but no axons

Membrane Potential

Voltage difference across a membrane

Voltage

Stored potential energy

Current

Flow of charge

Na+/K+ pump

ATPase Antiporter; 3 Na+ comes in, 2 K+ comes out

Electrochemical Gradient

Net driving force tending to move charged solutes across a membrane; sum of membrane potential and concentration gradients

Steep Electrochemical Gradient

Membrane potential and concentration gradients work in same direction

Small Electrochemical Gradient

Membrane potential and concentration gradients work against each other

Non-Gated (Leak) Channels

Channels that are always open, allowing solutes to "leak" through

Graded Potential

A temporary shift in the electrical charge in a tiny area of a neuron

Resting State

All gated Na+ and K+ channels are closed; membrane charge sits at -70mV

Depolarization Phase

Na+ channels open

Repolarization Phase

Na+ channels close. K+ channels open shortly after. K+ exits the cell down its gradient and repolarizes the membrane

Refractory Period

Period where K+ channels are delayed in closing after resting potential is reached.

Summation

Addition of all excitatory and inhibitory potentials to determine if an action potential is fired

Temporal Summation

Multiple signals from one neuron gather over time, pushing the postsynaptic cell towards its action potential

Spatial Summation

The sum of multiple synapses firing at different locations at the same time add to push the postsynaptic cell towards its action potential

Excitatory Postsynaptic Potentials (EPSPs)

Cause the postsynaptic membrane to depolarize, increasing the likelihood of an action potential

Inhibitory Postsynaptic Potentials (IPSPs)

Causes the postsynaptic membrane to hyperpolarize, decreasing the likelihood of an action potential

Absolute Refractory Period

The period immediately following the firing of an action potential where a new one cannot be stimulated no matter how great the stimuli

Relative Refractory Period

The period during repolarization where the firing of an action potential is possible but requires stronger stimuli

0.5-2 m/s

Conduction velocity of a small, unmyelinated fiber

3-15 m/s

Conduction velocity of a small, lightly myelinated fiber

Up to 120 m/s

Conduction velocity of a large, myelinated fiber

Electrical Synapses

Electrical current flows from one neuron to another; Very fast but not very modifiable

Chemical Synapses

Specialized for release and reception of chemical neurotransmitters; Slow but very modifiable

Acetylcholine (ACh)

Neurotransmitter that plays a major role in neuromuscular junctions

Biogenic Amines

Amino acid neurotransmitters that play a major role in emotional behavior

Amino Acids

GABA and Glutamate

Peptides

Associated with pain pathways

Purines

ATP and Adenosine

Ipsilateral Reflex Arc

Input and output occur on the same side

Contralateral Reflex Arc

Input and output occur on different sides

Ascending Tracts

Carries sensory information up the spinal cord

Descending Tracts

Carries motor commands down the spinal cord

Decussation

Crossing of neurons that occurs at the level of the medulla oblongata and spinal cord

Brain Barrier System

Regulates what substances can get from the bloodstream into the tissue fluid of the brain

Medulla Oblongata

Major regulator of autonomic function

Spinothalamic Pathway

Transmits pain and temperature sensations.

Corticospinal Pathway

Responsible for movement below the neck

Pons

A brain structure that relays information from the cerebellum to the rest of the brain

Tectum

Composed of the superior and inferior colliculi

Cerebral Peduncles

Connects the cerebrum to the brainstem

Tegmentum

Highly vascular area of the grey matter; Assists with fine motor control

Substantia Nigra

Prevents unwanted movements via inhibition of potential motor outputs; Damage to this structure is seen in patients with Parkinson's Disease

Cerebral crus

Connects the cerebrum to the pons

Reticular Formation

A nerve network that travels through the brainstem and thalamus and plays an important role in controlling arousal

Cerebellum

Structure at the rear of the brainstem; functions include processing sensory input and coordinating movement output and balance

Folia

Grey matter with folds located on the cerebellum

Arbor Vitae

"Tree of life"; white matter of the cerebellum

Thalamus

Major relay center of the cerebrum, plays a major role in emotions and memory

Hypothalamus

Major endocrine control center

Pineal Gland

Produces melatonin and modulates sleep patterns

Limbic System

Responsible for emotion and learning

Hippocampus

A neural center located in the limbic system that helps process explicit memories for storage.

Amygdala

Responsible for primal emotions, such as sorrow, anger, fear, aggression, and sexual arousal

Nucleus Accumbens

Reward center, target for some recreational drugs