Puzzle Piece 9: Nervous Tissue

Central Nervous System (CNS)

Brain and spinal cord.

Peripheral Nervous System (PNS)

All nervous system found outside of the brain and spinal cord, including cranial nerves, spinal nerves, ganglia, enteric plexus, and sensory receptors.

Ganglia

Group of neuronal cell bodies outside the central nervous system.

Nucleus

Group of neuronal cell bodies within the central nervous system.

Enteric plexus

Interconnections of neurons along the digestive tract, including the myenteric plexus and submucosal plexus.

Sensory receptors

Structures that receive sensation in viscera and skin, which can be part of or associated with a sensory neuron.

Somatic nervous system

We are consciously aware of the sensory input and the motor output.

Autonomic nervous system

We are not consciously aware of the sensory input and the motor output; it works automatically.

Sympathetic division

Part of the autonomic nervous system responsible for the 'Fight or flight' response.

Parasympathetic division

Part of the autonomic nervous system responsible for the 'Rest and digest' response.

Enteric nervous system

'Gut brain'; the interweaving of nerve fibers along the digestive tract.

Sensory neurons

Afferent neurons that transmit sensory information from the environment or internal organs to the CNS.

Somatic Sensory Neurons

Transmit conscious sensations to the CNS, involving sensations of touch, temperature, and pain.

Autonomic Sensory Neurons

Transmit unconscious sensations to the CNS, involving viscera sensations such as blood pressure and level of oxygen in the blood.

Exteroceptors

Sensory receptors located in the skin.

Proprioceptors

Sensory receptors located in muscles and joints.

Interoceptors

Sensory receptors located in visceral organs.

Integrative function

The process by which the central nervous system interprets sensory information and determines the appropriate outcome.

Motor neurons

Efferent neurons that transmit motor information from the CNS to the appropriate effectors (muscles and glands).

Somatic motor neurons

Control skeletal muscles consciously and transmit conscious motor commands from the CNS to skeletal muscles.

Autonomic motor neurons

Control smooth muscles, cardiac muscle, and glands, transmitting unconscious motor commands from the CNS.

Afferent neurons

Another name for sensory neurons, which carry sensory information to the CNS.

Somatic afferent neuron

A sensory neuron that allows us to become aware of sensations.

Autonomic afferent neuron

A sensory neuron that transmits sensations we do not become aware of.

CNS

Central Nervous System, which interprets sensory information.

Motor neuron

A neuron that exits the CNS to control muscle contraction or relaxation.

Efferent neuron

Another name for motor neurons, as they carry information away from the CNS.

Somatic motor neuron

A type of motor neuron used for conscious movement.

Autonomic motor neuron

A type of motor neuron that operates automatically, without conscious awareness.

Smooth muscle cells

Muscle cells found in the walls of blood vessels that affect blood pressure and heart rate.

Neurons

Highly specialized cells capable of communication and forming networks.

Number of neurons in the brain

Approximately 85 billion neurons.

Neuron communication

Each neuron communicates with 1,000 to 10,000 other neurons.

Dendrites

Branched extensions of the neuron that receive incoming signals.

Cell body (perikaryon/soma)

The part of the neuron that contains the nucleus.

Axon hillock

The point of no return in a neuron where the nerve impulse passes into the axon.

Axon

The branch of the neuron that takes information away from the cell body.

Terminal button

The end of the axon where neurotransmitters are stored.

Neurotransmitters

Chemical signals that transfer information from one neuron to another.

Electrical signals

Changes in voltage that travel through the neuron.

Chemical signals

Signals in the form of neurotransmitters that communicate between neurons.

Nerve Cells

Another term for neurons.

Nerve Fibers

Another term for neurons, emphasizing their long extensions.

Voltage change

The basis of electrical signals in neurons.

Lie detector

A device that uses autonomic responses like heart rate and blood pressure to detect deception.

Neuronal communication process

The sequence where electrical signals trigger neurotransmitter release, which then affects other neurons.

Nerve Impulse

Electrical signal and action potential are the same thing when we are talking about transmission of information along neurons.

Action Potential

Initiated by depolarization of the cell membrane, leading to the generation of an electrical impulse.

Depolarization

The process that occurs when a cell is not 'at rest', making the inside of the cell more positive compared to the outside environment.

Resting Membrane Potential

The state of a cell when it is 'at rest', characterized by a more negative charge inside compared to the outside environment.

Polarized Cell

A cell that is more negative on the inside compared to the outside environment.

Sodium/Potassium Active Pump

A mechanism that pumps 3 Na+ ions outside of the cell and 2 K+ ions inside the cell, using ATP for energy.

Excitable Cells

Cells capable of changing polarity, such as muscle cells and neurons, which can undergo depolarization and repolarization.

Depolarization and Repolarization

Fundamental processes involved in the generation of action potentials.

Gated Ion Channels

Channels that open and close to regulate ion flow across the cell membrane.

Voltage-Gated Ion Channel

A gated ion channel that opens in response to a change in voltage.

Ligand-Gated Ion Channel

A gated ion channel that opens in response to a ligand binding a receptor on the channel.

Voltage-Gated Na+ Channel

A voltage-gated ion channel that allows the passage of Na+ ions.

Voltage-Gated Ca+2 Channel

A voltage-gated ion channel that allows the passage of Ca+2 ions.

Ligand-Gated Na+ Channel

A ligand-gated ion channel that allows the passage of Na+ ions.

Synapse

The communication between neurons.

Electrical Signal

An action potential or nerve impulse that results from depolarization.

Resting Neuron

A neuron at resting membrane potential, which is negative inside relative to the outside.

Stimulus

An event that causes voltage-gated Na+ channels to open, leading to depolarization.

Positive Ions (Na+)

Ions that flow into the neuron during depolarization.

Terminal Buttons

The end of the axon where the electrical signal causes the opening of voltage-gated Ca2+ channels.

Voltage-gated Ca2+ Channels

Channels that open in response to an electrical signal, allowing calcium ions to flow into the terminal buttons.

Neurotransmitter Release

The process where vesicles filled with neurotransmitters fuse with the plasma membrane of the terminal button, releasing neurotransmitters into the synaptic gap.

Synaptic Gap

The gap between neurons where neurotransmitters flow and bind to receptors in the adjacent neuron.

Presynaptic Neuron

The neuron before the synaptic gap that sends the signal.

Postsynaptic Neuron

The neuron after the synaptic gap that receives the signal.

Ligand-gated Ion Channels

Channels that open when neurotransmitters bind to receptors, allowing the flow of ions across the plasma membrane.

Neurotransmitter

Chemicals that facilitate the transmission of information from one neuron to another.

Excitatory Neurotransmitters

Neurotransmitters that bind to receptors associated with ligand-gated Na+ channels, permitting Na+ to enter the postsynaptic cell, resulting in depolarization.

Inhibitory Neurotransmitters

Neurotransmitters that bind to receptors associated with ligand-gated Cl- channels, permitting Cl- to enter and K+ to exit the postsynaptic cell, resulting in hyperpolarization.

Acetylcholine

A neurotransmitter that is excitatory in skeletal muscle and inhibitory in cardiac muscle.

Adrenaline (Epinephrine)

A neurotransmitter that is excitatory in cardiac muscle (increases heart rate) and inhibitory on respiratory smooth muscle (relaxes smooth muscle in respiratory system).

Endorphins

Neurotransmitters with inhibitory effects, causing relaxation and sleepiness.

Narcotic Drugs

Substances that mimic the effects of endorphins (endogenous morphine).

Removal of Neurotransmitters

The process of terminating signal transmission by removing neurotransmitters from the synaptic cleft.

Reuptake

The process where neurotransmitters are taken back up into the presynaptic neuron for recycling.

Enzymatic Degradation

The breakdown of neurotransmitters into inactive metabolites by enzymes in the synaptic cleft.

Diffusion

The process where neurotransmitters diffuse into the nearby tissue fluid.

Myelinated Axon

An axon that has Schwann cells or oligodendrocytes wrapping around it, insulating segments of the axon.

Unmyelinated Axon

An axon that is bare, with nothing wrapping around it.

Myelin Sheath

The insulating layer formed by the wrapping of another cell around segments of the axon.

Node of Ranvier

The part of the axon that does not have another cell wrapped around it.

Saltatory Conduction

The jumping motion of electrical signals from one Node of Ranvier to the next, allowing faster signal transmission.

Conduction Velocity

Myelinated Neurons have a higher conduction velocity than unmyelinated neurons.

Nerve Impulse Speed (Unmyelinated)

Nerve impulses can travel as slowly as 0.5 meters per second.

Nerve Impulse Speed (Myelinated)

Nerve impulses can travel as fast as 130 meters per second.

Nerve Impulse Strength

Remains constant over time and distance, with no information lost regardless of the distance traveled.

Multipolar Neuron

A neuron with several branches leaving the cell body, including several dendrites and one axon.

Bipolar Neuron

A neuron with two branches leaving the cell body, one being a dendrite and the other an axon.

Unipolar Neuron

A neuron with a single branch that splits into two branches: one dendrite and one axon.

Interneurons

Multipolar neurons that connect other neurons within the nervous system.

Sensory Neurons (Special Senses)

Bipolar neurons that carry sensory information for special senses.

Sensory Neurons (Other Sensations)

Unipolar neurons that carry sensory information for sensations other than special senses.

Pseudounipolar Neuron

Another name for unipolar neurons, indicating a single branch that splits.

Pseudounipolar

A type of neuron that appears to have a single branch but originates from two branches during embryonic development.