306 MT 2 GPT generated

Tendons - Function

Transmit muscle force to bone, store and release elastic energy, absorb shock, and allow flexibility at joints.

Internal vs External Tendons

Internal tendons (aponeuroses) lie within the muscle belly; external tendons extend to the bone.

Pennation Angle

It’s the angle between muscle fibers and the line of action; larger angles increase PCSA but reduce force along the line of pull.

Physiological Cross-Sectional Area (PCSA)

Represents the number of sarcomeres in parallel; directly proportional to muscle force generation.

Muscle Spindles

Detect muscle length and rate of length change.

Muscle Spindle Components

Intrafusal fibers (bag & chain), Ia (dynamic) & II (static) afferents, γ motor efferents.

Golgi Tendon Organs

Detect muscle tension or force; help prevent over-contraction.

CNS Damage & Muscle Tone

Increases reflex gain → spasticity and hyperreflexia.

Divisions of Nervous System

Central (CNS: brain & spinal cord) and Peripheral (PNS: sensory & motor nerves).

Neuroglia Types & Functions

Astrocytes (support, BBB), microglia (immune), oligodendrocytes (CNS myelin), Schwann cells (PNS myelin).

Sensory Pathways

Dorsal column–medial lemniscus (fine touch, proprioception) and spinothalamic (pain, temperature, crude touch).

Motor Tract

Corticospinal tract.

Brodmann Areas

52 cortical regions defined by cell structure; e.g., Areas 1–3 = sensory, Area 4 = motor.

Cortical-Subcortical Loops

Thalamus (relay) and basal ganglia (movement control).

Ion Channel Types

Voltage-gated, ligand-gated, and mechanically-gated.

Resting Membrane Potential (RMP)

Set by Na+/K+-ATPase, K+ leak channels, and ionic gradients (~ -70 mV).

Driving Force

The difference between Vm and Eion (Vm – Eion); determines ion movement direction.

Nernst Equation

Calculates the equilibrium potential for a single ion.

Goldman-Hodgkin-Katz Equation

Calculates membrane potential considering multiple ions’ contributions.

Na+ Channel Gates

Activation gate (opens on depolarization) and inactivation gate (closes after opening).

Ohm’s Law

V = IR; voltage equals current times resistance.

Passive (Graded) Potential

Subthreshold voltage change that decays with distance; not regenerative.

Passive Properties Affecting Signal

Membrane resistance (Rm), capacitance (Cm), and axial resistance (Ra).

Length Constant (λ)

Distance where voltage decays to 37% of original; increases with higher Rm or fiber diameter.

Action Potential Sequence

Na+ influx → depolarization; K+ efflux → repolarization; brief hyperpolarization follows.

Unidirectional AP Propagation

Due to NaV inactivation and increased K+ permeability.

EPSP

Excitatory postsynaptic potential; Na+ influx > K+ efflux → depolarization.

IPSP

Inhibitory postsynaptic potential; Cl− influx or K+ efflux → hyperpolarization.

Spatial vs Temporal Summation

Spatial = multiple inputs at once; temporal = rapid successive inputs.

Saltatory Conduction

Action potentials “jump” between nodes of Ranvier; increases speed.

Effect of Myelination on Conduction

Increases membrane resistance, decreases capacitance → faster conduction.

Excitatory Neurotransmitters

Glutamate, Acetylcholine (ACh).

Inhibitory Neurotransmitters

GABA, Glycine.

Ionotropic vs Metabotropic Receptors

Ionotropic = direct ion channel (fast); Metabotropic = GPCR (slow, second messengers).

GPCR Activation

Ligand binding activates G protein (GDP → GTP exchange).

Gs Pathway

Activates adenylyl cyclase → ↑ cAMP → activates PKA.

Gi Pathway

Inhibits adenylyl cyclase → ↓ cAMP.

Gq Pathway

Activates PLC → IP3 & DAG → ↑ Ca2+, activates PKC.

Transducin (Gt) Role

In retina; activates phosphodiesterase → ↓ cGMP → closes CNG channels → hyperpolarization.

Second Messengers

cAMP, cGMP, IP3, DAG, Ca2+.

Electrophysiology

Study of ion movements and electrical properties of biological membranes.

Voltage Clamp vs Current Clamp

Voltage clamp fixes voltage, measures current; current clamp fixes current, measures voltage.

Patch-Clamp Technique

Records current through single ion channels.

Patch-Clamp Configurations

Cell-attached, inside-out, outside-out, whole-cell.

In Vivo Recording

High physiological relevance; technically difficult.

In Vitro Recording

High experimental control; less physiological relevance.

I-V Curve Slope

Represents conductance (γ).

Hebb’s Rule

“Neurons that fire together, wire together.”

Synaptic Plasticity

Ability of synapses to change strength.

LTP vs LTD

LTP strengthens synapses; LTD weakens them.

LTP Mechanism

NMDA receptor activation → Ca2+ influx → CaMKII activation → AMPAR insertion.

Homeostatic Plasticity

Restores neuron to baseline after prolonged activity change.

Sensory Transduction

Conversion of stimulus energy into electrical signals.

Phasic vs Tonic Receptors

Phasic adapt quickly; tonic maintain continuous response.

Sensory Tracts

Dorsal column–medial lemniscus (fine touch), spinothalamic (pain/temp).

Lateral Inhibition

Enhances contrast by inhibiting neighboring afferents; improves localization.

Proprioceptive Sensors

Muscle spindles detect length; GTOs detect tension.

Motor Unit

One α-motor neuron and all muscle fibers it innervates.

Size Principle

Small motor units recruit first; large ones last.

Stretch Reflex

Monosynaptic; maintains muscle length via spindle (Ia afferent).

Golgi Tendon Reflex

Polysynaptic; inhibits excessive tension via Ib afferent.

Basal Ganglia Function

Initiates and suppresses movement; dopamine modulates direct/indirect pathways.

Cerebellum Function

Coordinates movement, balance, and motor learning.

UMN vs LMN Lesion Signs

UMN: spasticity, hyperreflexia; LMN: flaccidity, atrophy, fasciculations.