Biology slides 4
Nervous System purpose
Receives information and then responds through coordinating muscular and gland activities.
Intracellular Signaling
Signaling that occurs within neuron cells.
Intercellular Signaling
Signaling that occurs between neurons.
Endocrine System Signaling Mechanism
Chemical.
Nervous System Signaling Mechanism
Chemical/electrical.
Primary Chemical Signal in Endocrine System
Hormones.
Primary Chemical Signal in Nervous System
Neurotransmitters.
Distance Traveled by Endocrine System
Long or short.
Distance Traveled by Nervous Signals
Always short.
Response Time of Endocrine System
Fast or slow.
Response Time of Nervous System
Always fast.
Environment Targeted by Endocrine System
Internal.
Environment Targeted by Nervous System
Internal and external.
Nervous System Functions
1) Monitor internal and external environment of the body 2) Integrate and analyze sensory information 3) Co-ordinate responses in all other organ systems.
Sensory Receptors
Pick up STIMULI.
Examples of External Stimuli
Temperature, light, noise, smell, position, pressure, pain.
Examples of Internal Stimuli
Ions (Na*, K+, Ca++...), blood gasses/pH, glucose levels, water levels.
CNS
Central Nervous System, resposible for processing information (making decisions).
PNS
Peripheral Nervous System, all nerves that extend from the spine and brain.
Afferent Component of PNS
Sends information to the CNS.
Efferent Component of PNS
Acts based on the CNS' commands.
Brain Function
Controls almost every part of the body.
Reflexes
Quick communication with the spine, ex: knee tap, closing your eyes.
Neurons in the Brain
Contains approximately 100 billion neurons.
Protection of the Brain
Well-protected with skull, cerebrospinal fluid, and blood-brain barrier.
Somatic Nervous System (SNS)
Controls our voluntary muscles, sends and receives information to/from the CNS.
Autonomic Nervous System (ANS)
Involuntary, influences breathing, heart, parts of the digestive system, and more.
Sympathetic ANS Function
Fight or flight - 'active' behaviour.
Parasympathetic
Rest and digest - 'passive' behaviour.
Autonomic Nervous System
A part of the nervous system that controls involuntary actions.
Rest and Digest
A state of the autonomic nervous system that conserves energy.
Fight and Flight
A state of the autonomic nervous system that prepares the body for action.
Neurons
Cells that quickly and efficiently communicate information.
Glial Cells
Supportive cells in the nervous system that assist neurons.
Astrocyte
A type of CNS glial cell that provides support.
Oligodendrocyte
A CNS glial cell responsible for insulation and myelination.
Microglia
CNS glial cells involved in immune surveillance and phagocytosis.
Ependymal cell
CNS glial cell that creates cerebrospinal fluid (CSF).
Satellite cell
A PNS glial cell that provides support.
Schwann cell
A PNS glial cell responsible for insulation and myelination.
Dendrites
Extensions of neurons that receive information.
Cell Body (Soma)
The part of a neuron where proteins may be produced.
Axon
The part of a neuron that transmits information away from the cell body.
Axon Hillock
The structure where the soma branches into the axon.
Synapse
The junction between dendrites and axons where communication occurs.
Sensory Neurons
Neurons that receive information and pass it towards the CNS.
Interneurons
Neurons that receive information from sensory neurons and make decisions.
Motor Neurons
Neurons that cause muscular contractions/relaxation in response to decisions.
Multipolar Neurons
The most common type of neuron in the CNS, characterized by a classic lollipop shape.
Unipolar Neurons
Neurons with dendrites feeding directly into the axon, typically found in the PNS.
Grey Matter
Regions of the nervous system containing cell bodies, arranged in a butterfly shape.
White Matter
Regiond of the nervous system containing myelinated axons, arranged into columns.
Myelin
A substance that insulates axons, produced by oligodendrocytes in the CNS and Schwann Cells in the PNS.
Nodes of Ranvier
Gaps between segments of myelin where ions can cross the axon's cell membrane.
Intraneuronal Communication
Communication within a neuron is via action potentials.
Interneuronal Communication
Communication between neurons is via neurotransmitter release into the synapse.
Action Potential
An action potential is electrical and depends on the movement of ions across a membrane.
Neurotransmitters
Neurotransmitters are chemical substances that bind to receptors, causing cellular changes.
Ion movement
Ions cannot move through the cell membrane; they depend on channels/carriers to get across.
Phospholipid Bilayer
The cell membrane is composed of a phospholipid bilayer with many transmembrane proteins.
Na+/K+ pump
The Na+/K+ pump maintains ion concentration differences by sending out 3 Na+ for every 2 K+ it allows in.
Charge imbalance in neurons
At most times, neurons have low Na+ inside and high K+ inside the cell.
Facilitated Diffusion
Neurons send information by allowing Na+ and K+ to flow with their gradients through facilitated diffusion.
Ligand-gated ion channel
A ligand-gated ion channel opens when a molecule, typically a neurotransmitter, binds to it.
Mechanically-gated ion channel
Mechanically-gated ion channels open in response to physical pressure.
Voltage-gated ion channel
Voltage-gated ion channels open when a specific voltage is detected.
Ionotropic Receptors
Ionotropic receptors are another name for ligand-gated ion channels.
Cations
Cations are positively charged ions, such as sodium, calcium, and potassium.
Thermoreceptors
Thermoreceptors work on the principle that a change in local tissue temperature causes the channel to open.
Transmembrane voltage
Transmembrane voltage changes can cause voltage-gated channels to open.
Charge imbalance
At most times, neurons have low Na+ inside the cell and high K+ inside the cell.
Na+/K+ pump
Maintains the difference in ion concentration by sending out 3 Na+ for every 2 K+ it allows in, using energy (active transport).
Voltage difference
The outside of neurons is more positive than the inside, which can be measured.
Resting membrane voltage
The inside of a neuron is normally at -70mV.
Depolarization
If a stimulus allows Na+ to enter the cell, the voltage will become positive.
K+ exit
Allows K+ to leave the cell, eventually causing the inside to return to being negative.
Overshooting voltage
Loss of K+ from the cell can cause voltage to go lower than -70mV (ex: -90mV).
Threshold voltage
The minimum voltage change required to activate voltage-gated channels, going from -70mV to at least -55mV.
Ligand-gated channel
A type of ion channel that opens in response to a chemical signal, initiating the action potential process.
Mechanically-gated channel
An ion channel that opens in response to mechanical stimulus, allowing Na+ to enter the cell.
Voltage-gated channels
Channels that open when the membrane potential reaches a certain threshold, allowing Na+ to enter and K+ to exit.
Repolarization
The process of returning the membrane voltage back to a negative value after depolarization.
Hyperpolarization
Occurs when the membrane voltage goes below the resting value after repolarization.
Node of Ranvier
Gaps in the myelin sheath where action potentials are triggered in myelinated axons.
Saltatory conduction
The process by which the action potential jumps from one Node of Ranvier to the next in a myelinated axon.
Ion current
The flow of ions across the membrane during an action potential.
Membrane potential
The voltage across the cell membrane, which changes during action potentials.
Stimulus
An external signal that triggers the opening of Na+ channels in the neuron.
Electrical signal
The change in voltage that propagates along the axon as a result of ion movements.
Saltatory propagation
Jumping conduction of action potentials along the axon.
Signal speed
The speed at which a signal leaps down the axon, approximately ~18-140m/s.
Spatial summation
Activation when multiple neurons send messages additively to provide enough stimulation.
Temporal summation
Activation when one neuron sends messages continuously over time.
EPSP
Excitatory PostSynaptic Potential.
Chemical synapse
A synapse where neurotransmitters are released from one axon to bind receptors on another neurons dendrites.
Electrical synapse
A synapse where ions are directly transferred from one neuron to another to initiate action potentials.
Multiple Sclerosis
A condition resulting from the gradual destruction of oligodendrocytes and removal of myelin.
Seizures
Excessive firing in certain neurons leading to abnormal electrical activity in the brain.
Calcium channels
Voltage-gated channels that open to allow Ca2+ to enter the cell when an action potential reaches the axon terminal.