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Intracellular Fluid (ICF)
67% of total body water
Extracellular Fluid (ECF)
33% of total body water (20% blood plasma, 80% interstitial fluid)
Extracellular Matrix
Composed of protein fibers (collagen and elastin) and a gel-like ground substance made of glycoproteins and proteoglycans
Osmolality
The total molality of a solution when combining all solutes; crucial for maintaining proper cell hydration and preventing cell damage
Tonicity
Refers to how a solution affects cell volume: Isotonic (no net movement of water), Hypotonic (water moves into the cell, causing swelling), Hypertonic (water moves out, causing cell shrinkage)
Dehydration
Physiological response where osmoreceptors in the hypothalamus detect high osmolality, activating thirst mechanism, releasing ADH, and causing water retention in kidneys
Molarity
Moles of solute per liter of solution
Molality
Moles of solute per kg of solvent
Molar solution
Prepared by dissolving 1 mole of solute in 1 liter of solvent (e.g., 180g glucose in 1L water = 1M glucose)
Molal solution
Prepared by dissolving 1 mole of solute in 1 kg of solvent
Diffusion
Movement of solutes from high to low concentration
Osmosis
Movement of water across a selectively permeable membrane
Membrane potential (MP)
The voltage difference across a cell membrane, measured by placing one electrode inside the cell and one outside
Resting Membrane Potential (RMP)
Maintained by the Na+/K+ pump moving 3 Na+ out and 2 K+ in, along with selective ion permeability
Equilibrium Potential
The voltage at which the electrical and chemical forces for an ion are balanced, preventing further net movement
Transport Across Epithelial Membranes
Molecules move through absorption, reabsorption, transcellular transport, paracellular transport, and carrier-mediated transport
Active transport
Requires ATP (e.g., Na+/K+ pump)
Passive transport
Does not require ATP (e.g., diffusion, osmosis)
Secondary Active Transport
Movement of one substance using the energy from another substance's concentration gradient (e.g., Na+-glucose cotransport)
Brain Imaging Techniques
Different methods used to visualize the brain
MRI
Soft tissue imaging.
PET
Metabolic activity.
CT
Soft tissue and bones.
fMRI
Blood flow changes in brain.
Depolarization
Membrane potential becomes more positive due to Na+ influx.
Repolarization
Return to resting potential as K+ exits the cell.
Hyperpolarization
Membrane potential becomes more negative than resting due to excessive K+ efflux.
Action Potential
An all-or-none electrical impulse that propagates along an axon.
EPSP (Excitatory Post-Synaptic Potential)
A graded depolarization that moves the neuron closer to threshold.
IPSP (Inhibitory Post-Synaptic Potential)
A graded hyperpolarization that moves the neuron further from threshold.
Pre-synaptic neuron
Releases neurotransmitters into the synaptic cleft.
Synaptic cleft
The gap between neurons where neurotransmitters diffuse.
Post-synaptic membrane
Contains receptors that bind neurotransmitters to initiate a response.
Ligand-Gated Channels
Open in response to neurotransmitters (e.g., nicotinic ACh receptors).
Voltage-Gated Channels
Open in response to changes in membrane potential (e.g., Na+ and K+ channels in action potentials).
Leaky Channels
Always open, allowing passive ion movement (e.g., K+ leak channels maintain resting potential).
Resting Phase
-70mV: Na+/K+ pump maintains potential.
Depolarization Phase
+30mV: Voltage-gated Na+ channels open, Na+ enters.
Repolarization Phase
-70mV: Voltage-gated K+ channels open, K+ exits.
Hyperpolarization Phase
-90mV: Excessive K+ efflux, followed by return to resting potential.
Positive Feedback
Depolarization opens more Na+ channels, amplifying the signal.
Negative Feedback
K+ channels open during repolarization, restoring resting potential.
Absolute Refractory Period
No new action potential can be generated (Na+ channels are inactivated).
Relative Refractory Period
A stronger stimulus is required to initiate an action potential (some Na+ channels reset).
Myelinated Neurons
Conduct via saltatory conduction, where the action potential jumps between nodes of Ranvier, increasing speed.
Unmyelinated Neurons
Conduct via continuous conduction, where the signal propagates along the entire axon length, making it slower.
Dendrites
Receive signals.
Cell Body (Soma)
Contains the nucleus and processes information.
Axon
Transmits impulses away from the cell body.
Myelin Sheath
Insulates the axon and speeds up conduction.
Axon Terminals
Release neurotransmitters to communicate with other neurons.
Schwann Cells
Myelinate axons in the PNS; one Schwann cell per axon segment.
Oligodendrocytes
Myelinate axons in the CNS; one oligodendrocyte myelinates multiple axons.
Precentral Gyrus
Controls voluntary movements.
Postcentral Gyrus
Processes sensory input from the body.
Homunculus
A map of the body on the motor and sensory cortex, showing areas with higher nerve density (e.g., hands, lips).
Broca's Aphasia
Difficulty with speech production, comprehension intact.
Wernicke's Aphasia
Difficulty with language comprehension, speech is fluent but nonsensical.
Amygdala
Processes emotions, especially fear, aggression, and emotional memory.
Thalamus
Acts as the sensory relay station, sending sensory information (except smell) to the cerebral cortex.
Ascending Tracts
Carry sensory information to the brain (e.g., spinothalamic tract).
Descending Tracts
Carry motor commands from the brain to muscles (e.g., corticospinal tract).
Convergence
Multiple neurons synapse onto a single neuron, integrating signals.
Divergence
One neuron synapses onto multiple neurons, amplifying signals.
Ganglion
Cluster of neuron cell bodies in the PNS.
Nucleus
Cluster of neuron cell bodies in the CNS.
EPSP
Excitatory Post-Synaptic Potential: Depolarization increases the likelihood of an action potential.
IPSP
Inhibitory Post-Synaptic Potential: Hyperpolarization decreases the likelihood of an action potential.
Action Potential
All-or-none electrical impulse.
Post-Synaptic Potential
Graded response, can be excitatory or inhibitory.
Neurons
Transmit signals.
Glial Cells
Support neurons, e.g., astrocytes, Schwann cells.
Sympathetic Nervous System
"Fight or flight" (thoracolumbar origin, short preganglionic, long postganglionic, norepinephrine release).
Parasympathetic Nervous System
"Rest and digest" (craniosacral origin, long preganglionic, short postganglionic, acetylcholine release).
Blood-Brain Barrier
A selective barrier formed by tight junctions in endothelial cells, protecting the brain from harmful substances while allowing essential nutrients.
