Animal Nervous Systems

Flashcards covering the key vocabulary and definitions related to animal nervous systems.

Nervous System

Main Function: Detect, process, and respond to stimuli and maintain homeostasis.

Central Nervous System (CNS)

Control center; consisting of the Brain and Spinal Cord.

Peripheral Nervous System (PNS)

All the nerves that connect the brain and spinal cord with sensory receptors, muscles and glands.

Cell body

Main part of the cell containing the nucleus, most of the cytoplasm, and organelles.

Dendrites

Small extensions from the cell body of a neuron that receive incoming information.

Axon

Long extensions from a neuron that conduct electrical impulses away from the cell body.

Axon Terminals

Fine extensions at the ends of axons that contact with dendrites of other neurons.

Nerve

Bundle of axons in the PNS.

Cranial nerves

12 pairs connecting body parts to the brain & brainstem

Spinal nerves

31 pairs connecting body parts to the spinal cord

Sympathetic nervous system

The nerves that stimulates fight-or-flight responses, such as increased heart rate, increased blood pressure, and slowed digestion.

Parasympathetic nervous system

Nerves that trigger responses for conserving or restoring energy, such as reduced heart rate and stimulated digestion.

Sensory (afferent) neurons

Neurons that have sensory receptors that detect changes in the environment and carry impulse to interneurons.

Internuncial (association or interneuron) neurons

Multipolar neurons in the brain and spinal cord that carry impulses to the correct part of the brain or spinal cord for processing.

Motor neuron

A nerve cell that carries signals from the central nervous system to effector cells (efferent neuron) in a muscle or gland.

Resting potential

The difference in voltage (relative charge) across the cell membrane in a cell at rest (-65to -70 mV).

Na+/K+ ATPase

Cell membrane protein that uses ATP to transport three Na+ out of the cell and two K+ into the cell to constantly maintain the resting potential.

Depolarize phase

Reversal of electrical charge from resting potential.

Threshold potential

The membrane potential that will trigger an action potential in an excitable cell.

Action potential

A rapid, temporary change in electrical potential across a membrane, from negative to positive and back to negative that flows along a cell’s membrane.

Repolarization phase

A change in membrane potential from a depolarized state back to resting potential.

Hyperpolarization phase

When the membrane potential is slightly more negative than the resting potential.

Synapse

Gap between axon terminal of one neuron and the dendrite of a neighboring neuron, or between neurons and muscles.

Synaptic vesicles

Neurotransmitter-containing vesicle inside the end of an axon that releases neurotransmitters into the synaptic cleft by exocytosis.

Neurotransmitter

Chemicals that transmit signals from a neuron to a target cell across a synapse.

Excitatory neurotransmitters

Depolarize the postsynaptic cell.

Inhibitory neurotransmitters

Hyperpolarize the postsynaptic cell and prevent signal transmission.

Presynaptic neuron

Neuron at the synapse releasing neurotransmitters

Postsynaptic neuron

Neuron at the synapse that contains proteins that the neurotransmitters will bind.

Glutamate

Amino acid neurotransmitter that binds sodium transporters (glutamate receptors). -The most abundant excitatory neurotransmitter released by nerve cells in the brain.

GABA (Gamma-aminobutyric acid)

Amino acid neurotransmitter that inhibits neuron transmission by opening Cl- channels that increase negative charge inside the postsynaptic neuron, preventing sodium influx from starting an action potential.

Norepinephrine

Neurotransmitter that has 3 different receptors that can either excite or inhibit an action potential, depending on the receptor composition in a target cell. -The main neurotransmitter used by the sympathetic nervous system (fight-or-flight responses).

Summation

If the total signal from many synapses is enough to initiate an action potential down the axon.

Neuroglia (glial) cells

Nerve cells that perform support and protection for neurons.

Astrocytes

Cells that connect neurons to blood vessels to form a supporting network in the brain and spinal cord.

Oligodendroglia (oligodendrocytes)

Cells that form a structure holding axons together and make myelin sheaths in the CNS.

Myelin Sheaths

Fatty sheath surrounding some axons.

Schwann Cells (neurolemmocytes)

Entire cells that forms 1 myelin sheath around neuronal axons in the PNS.

Nodes of Ranvier (neurofibral nodes)

Gaps in myelin sheaths that let ions flow freely from the extracellular fluid to the axons, which increases the speed of the action potential.

Microglial cells

Small immune cells that protect the CNS by engulfing and destroying bacteria or cellular debris.

Ependymal cells

Cells that line the fluid filled ventricles of the brain and produce cerebrospinal fluid.

Blood-brain barrier

Extensions from astrocyte cells surround brain blood vessels to prevent entry of certain chemicals and pathogens from the blood.

Brainstem

Neural tissue that connects the brain to the spinal cord.

Diencephalon

Structure that lies between the 2 cerebral hemispheres.

Cerebrum

Largest part of the brain consisting of 2 hemispheres.

Cerebellum

Butterfly-shaped tissue located beneath the cerebrum and behind the brainstem that helps maintain balance and coordination.

Frontal Lobe

Anterior (front) portion of both hemispheres. -It controls voluntary muscles, moods & aggression. (movement, emotions, and problem solving)

Occipital lobe

Back portion of the 2 hemispheres. -It receives and interprets visual information. (visual processing)

Parietal lobe

Lobe between frontal and occipital lobes. -It evaluates (sensory information of touch), pain, balance, taste, and temperature.

Temporal Lobe

Lobe beneath the frontal and parietal lobes. -Controls hearing