AL

Untitled Flashcards Set

  1. Dendrites – Receive signals.

  2. Cell Body (Soma) – Processes signals.

  3. Axon – Transmits impulses.

  4. Axon Terminals – Release neurotransmitters.

  5. Myelin Sheath – Increases conduction speed.

  6. Nodes of Ranvier – Allow saltatory conduction.

Types of Neurons

  1. Sensory (Afferent) Neurons – Carry signals to CNS.

  2. Motor (Efferent) Neurons – Carry signals from CNS.

  3. Interneurons – Process and relay information within CNS.

Glial Cells & Their Functions

  • CNS:

    • Astrocytes – Support neurons, blood-brain barrier.

    • Oligodendrocytes – Myelinate CNS axons.

    • Microglia – Immune defense.

    • Ependymal Cells – Produce cerebrospinal fluid (CSF).

  • PNS:

    • Schwann Cells – Myelinate PNS axons.

    • Satellite Cells – Support neuron cell bodies.

Ion Channels & What Opens Them

  1. Voltage-gated – Open at specific membrane potentials (e.g., Na⁺, K⁺, Ca²⁺).

  2. Ligand-gated – Open when a neurotransmitter binds.

  3. Mechanically-gated – Open due to pressure or stretch.

  4. Leak Channels – Always open (K⁺ leak channels help maintain resting potential).

Key Membrane Voltages

  • Resting Membrane Potential: ~ -70mV

  • Threshold Potential: ~ -55mV (triggers action potential)

  • Depolarization Peak: ~ +30mV

  • Hyperpolarization: ~ -80mV

Na⁺ and K⁺ in Membrane Potential

  • Resting State: More Na⁺ outside, more K⁺ inside.

  • Depolarization: Na⁺ channels open, Na⁺ rushes in.

  • Repolarization: K⁺ channels open, K⁺ exits.

  • Hyperpolarization: Excess K⁺ leaves before channels close.

Stages of an Action Potential

  1. Resting Potential (-70mV)

  2. Depolarization (Na⁺ enters, +30mV)

  3. Repolarization (K⁺ exits, returning to negative)

  4. Hyperpolarization (K⁺ overshoots, then returns to rest)

Graded vs. Action Potential

  • Graded Potential – Small, localized, can summate.

  • Action Potential – All-or-none, travels down axon.

Types of Summation

  1. Temporal Summation – Multiple signals from one neuron.

  2. Spatial Summation – Signals from multiple neurons.

Types of Refractory Periods

  1. Absolute – No action potential possible.

  2. Relative – Needs stronger stimulus.

Saltatory vs. Continuous Conduction

  • Saltatory Conduction – Faster, jumps between nodes of Ranvier (myelinated).

  • Continuous Conduction – Slower, occurs in unmyelinated fibers.

Synapse & Integration

  • Structure: Presynaptic neuron → Synaptic cleft → Postsynaptic neuron

  • Neurotransmitters communicate by binding to receptors on the postsynaptic cell.

EPSP vs. IPSP

  • EPSP (Excitatory Postsynaptic Potential) – Depolarizes, increases firing likelihood.

  • IPSP (Inhibitory Postsynaptic Potential) – Hyperpolarizes, decreases firing likelihood.

Inhibition & Excitation

  • Excitatory (EPSP): Na⁺ or Ca²⁺ enters.

  • Inhibitory (IPSP): Cl⁻ enters or K⁺ exits.

Neurotransmitters & Their Neurons

  • Cholinergic (ACh) → Muscarinic & Nicotinic receptors

  • Adrenergic (Epinephrine & Norepinephrine) → Sympathetic system

Amino Acid Neurotransmitters

  • Excitatory: Glutamate

  • Inhibitory: GABA, Glycine

CNS Diseases

  • Parkinson’s – Dopamine loss in substantia nigra.

  • Alzheimer’s – Amyloid plaques, neurofibrillary tangles.

Gray vs. White Matter

  • Gray Matter – Cell bodies, processing.

  • White Matter – Myelinated axons, signal transmission.

Fiber Connections in CNS

  • Commissural Fibers – Between hemispheres (corpus callosum).

  • Association Fibers – Within same hemisphere.

  • Projection Fibers – Connect cortex to lower CNS.

Dermatomes

  • Skin areas innervated by specific spinal nerves.

Lobes of the Brain & Functions

  • Frontal – Motor control, decision-making.

  • Parietal – Sensory integration.

  • Occipital – Vision.

  • Temporal – Hearing, memory.

Functions of Diencephalon, Brainstem, Cerebellum

  • Diencephalon: Thalamus (relay), Hypothalamus (homeostasis).

  • Brainstem: Midbrain, pons, medulla (autonomic functions).

  • Cerebellum: Coordination, balance.

Reflexes

  • Stretch Reflex – Knee-jerk.

  • Withdrawal Reflex – Pulling away from pain.

Motor & Sensory Tracts

  • Motor (Descending): Corticospinal (voluntary movement).

  • Sensory (Ascending): Spinothalamic (pain, temperature).

Sleep & Brain Waves

  • Stages: NREM (light to deep), REM (dreaming).

  • Brain Waves: Alpha, Beta, Delta, Theta.

Sensory System

Receptor Types

  • Mechanoreceptors – Touch.

  • Thermoreceptors – Temperature.

  • Nociceptors – Pain.

  • Photoreceptors – Vision.

Order of Sensory Neurons

  1. 1st Order – From receptor to spinal cord.

  2. 2nd Order – From spinal cord to thalamus.

  3. 3rd Order – From thalamus to cerebral cortex.

Referred Pain

  • Pain felt in different location (e.g., heart attack → left arm).

Visual Terms

  • Accommodation – Lens focusing.

  • Refraction – Bending of light.

  • Reflection – Light bouncing off surfaces.

Visual Disorders

  • Myopia (nearsighted), Hyperopia (farsighted), Astigmatism (irregular cornea).

Iris Control

  • Sympathetic → Dilation.

  • Parasympathetic → Constriction.

Retina Cells & Pathway

  • Rods (low light), Cones (color).

  • Pathway: Retina → Optic Nerve → Optic Chiasm → Visual Cortex.

Ear & Sound Pathway

  • Hair Cells: In cochlea (detect sound).

  • Pathway: Eardrum → Ossicles → Cochlea → Auditory Nerve → Brain.

Taste & Nerves

  • Tastes: Sweet, sour, salty, bitter, umami.

  • Nerves: Facial (VII), Glossopharyngeal (IX), Vagus (X).