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Homeostasis

The body's way of keeping internal stability despite external changes.

Importance of Homeostasis

It keeps the body functioning properly; imbalance can lead to illness.

Set Point

Normal target value, such as 98.6°F for body temperature.

Control Center

Usually the brain or spinal cord, decides what actions to take for homeostasis.

Afferent Signal

Information sent to the control center.

Efferent Signal

Commands sent from the control center to the effectors.

Effectors

Muscles or glands that enact change in the body.

Negative Feedback

Reverses a change to maintain homeostasis (e.g., sweating when hot).

Positive Feedback

Increases a change for a specific purpose (e.g., contractions in childbirth).

Active Transport

Transport that requires energy to move substances against their concentration gradient.

Passive Transport

Movement of substances without energy, from high to low concentration.

Simple Diffusion

Movement from an area of high concentration to low concentration.

Factors Influencing Diffusion Rate

Larger gradient, higher temperature, smaller molecule size, and larger surface area increase diffusion.

Primary Active Transport

Direct use of ATP to move substances across a membrane.

Secondary Active Transport

Utilizes energy from another gradient to move substances across a membrane.

Bulk Transport

Movement of large materials in or out of the cell (e.g., endocytosis, exocytosis).

Endocytosis

Cellular process of taking in material (e.g., white blood cells consuming bacteria).

Exocytosis

Cellular process of releasing material (e.g., neuron releasing neurotransmitters).

Osmosis

Movement of water through a membrane from less concentrated to more concentrated areas.

Osmolarity

Total concentration of solutes in a solution.

Tonicity

Describes the effect of a solution's non-penetrating solutes on cell volume.

Hypertonic Solution

Solution with a higher concentration of solutes outside the cell, causing water to leave the cell.

Hypotonic Solution

Solution with a lower concentration of solutes outside the cell, causing water to enter the cell.

Isotonic Solution

Equal concentration of solutes inside and outside the cell, resulting in no net movement of water.

Neurons

Cells that transmit signals in the nervous system.

Dendrites

Parts of a neuron that receive signals.

Axon

The part of the neuron that transmits signals away from the cell body.

Axon Terminals

Ends of axons that release neurotransmitters to communicate with other neurons.

Nodes of Ranvier

Gaps in the myelin sheath that facilitate faster signal conduction along the axon.

Synapse

The junction between two neurons where communication occurs.

Synaptic Cleft

The gap between the presynaptic and postsynaptic cells.

Presynaptic Cell

The neuron that sends the neurotransmitter signal.

Postsynaptic Cell

The neuron or cell that receives the neurotransmitter signal.

Neurotransmitter

Chemical messengers that transmit signals across the synaptic cleft.

Resting Membrane Potential

The electrical potential difference across the neuronal membrane at rest, typically -70 mV.

Ion Distribution

Na+ is greater outside the cell, and K+ is greater inside the cell.

Na+/K+ Pump

A protein that maintains resting membrane potential by moving Na+ out and K+ into the cell.

Depolarization

The process when Na+ enters the cell, making the inside more positive.

Repolarization

The process when K+ exits the cell, returning the inside to a negative potential.

Hyperpolarization

When the inside of the cell becomes more negative than the resting potential due to excess K+ outflow.

Action Potential

A rapid, all-or-nothing electrical signal that travels down an axon.

Graded Potential

A small, variable change in membrane potential.

Ligand-gated Channel

A channel that opens in response to the binding of a neurotransmitter.

Voltage-gated Na+ Channels

Channels that open when the membrane depolarizes, allowing Na+ to enter the cell.

Saltatory Conduction

Rapid signal conduction that occurs when action potentials jump between Nodes of Ranvier.

Non-saltatory Conduction

Slower conduction where the action potential travels step-by-step along the axon.

A Fibers

Fastest nerve fibers that are large and myelinated.

Calcium's Role in Neurotransmitter Release

Calcium influx causes vesicles with neurotransmitters to fuse with the membrane.

Ligand-gated Channels Location

Found on the postsynaptic membrane, activated by neurotransmitter binding.

Excitatory Response

When Na+ enters the neuron, making it more likely to fire an action potential.

Inhibitory Response

When Cl- enters or K+ leaves, making it less likely for the neuron to fire.

EPSP

Excitatory postsynaptic potential; moves the membrane potential closer to the threshold for firing.

IPSP

Inhibitory postsynaptic potential; moves the membrane potential further from the firing threshold.

Agonist

A substance that activates a receptor.

Antagonist

A substance that blocks a receptor.

Reuptake Inhibitor

A substance that prevents the recycling of neurotransmitters.

Enzyme Inhibitor

A substance that stops the breakdown of neurotransmitters.

Acetylcholine Receptors

Receptors that ACh binds to include nicotinic (always excitatory) and muscarinic (variable effects).

Nicotinic Receptors

Type of receptor found in skeletal muscle that is always excitatory.

Muscarinic Receptors

Type of receptor found in various tissues that can be either excitatory or inhibitory.

Adrenergic Receptors

Receptors that bind epinephrine/norepinephrine; include alpha (vasoconstriction) and beta (varying effects).

Serotonin's Role

A neurotransmitter involved in mood regulation and sleep.

Dopamine's Role

A neurotransmitter crucial for reward processing and movement.

Glutamate

The main excitatory neurotransmitter in the brain.

GABA

The main inhibitory neurotransmitter in the brain.

Substance P

A neurotransmitter involved in the pain pathway.

Endorphins

Natural painkillers produced by the body.

Neurotransmitters in Alzheimer’s

Reduced acetylcholine levels are associated with Alzheimer's disease.

Neurotransmitters in Parkinson’s

Reduced dopamine levels are characteristic of Parkinson's disease.

Runner's High

Increased endorphin levels that occur during prolonged exercise.

Cobra Venom

Blocks the action of acetylcholine at the neuromuscular junction.

High Blood Pressure Neurotransmitters

Excess norepinephrine can lead to high blood pressure.

Neurotransmitters in Depression Treatment

Serotonin, dopamine, and norepinephrine are often targeted in depression therapies.

Excitatory Neurotransmitters

Include glutamate, acetylcholine (nicotinic), and some dopamine.

Inhibitory Neurotransmitters

Include GABA, glycine, and some acetylcholine (muscarinic).