phsyio exam 2

CNS vs PNS

CNS = brain & spinal cord (processing); PNS = communication to/from body

Afferent vs efferent

Afferent = sensory → CNS; Efferent = motor → body

Parts of a neuron

Dendrites, cell body, axon, myelin

Resting membrane potential

~ -70 mV

Depolarization

Na⁺ influx

Repolarization

K⁺ efflux

EPSP

Excitatory; Na⁺ enters

IPSP

Inhibitory; K⁺ leaves or Cl⁻ enters

Temporal summation

Rapid signals from same neuron

Spatial summation

Signals from multiple neurons

Threshold potential

Level needed to trigger action potential

Saltatory conduction

Signal jumps node to node (myelinated axon)

Action potential step 1

Depolarization (Na⁺ in)

Action potential step 2

Repolarization (K⁺ out)

Action potential step 3

Hyperpolarization

Why is myelin important?

Speeds conduction

What triggers neurotransmitter release?

Ca²⁺ influx

Role of SNARE proteins

Vesicle fusion

Neurotransmitter removal methods

Reuptake, enzymatic breakdown, diffusion

Acetylcholine (ACh) function

Muscle activation

Nicotinic receptor

Ionotropic (fast)

Muscarinic receptor

Metabotropic (slow)

Dopamine

Reward, motivation

Serotonin

Mood regulation

SSRIs

Block serotonin reuptake → increase serotonin

Norepinephrine/Epinephrine

Fight or flight response

GABA

Main inhibitory neurotransmitter

GABA-A vs GABA-B

GABA-A = fast; GABA-B = slow

Endorphins

Pain relief

Transduction

Stimulus → electrical signal

Sensory pathway

1st → 2nd → 3rd neuron → cortex

Decussation

Crossing to opposite side

Thalamus role

Relay station for sensory signals

Exteroceptors

Detect external stimuli

Interoceptors

Detect internal organ conditions

Proprioceptors

Detect body position

Tonic receptors

Constant signaling

Phasic receptors

Rapidly adapting

Merkel cells

Pressure (tonic)

Meissner corpuscles

Light touch (phasic)

Pacinian corpuscles

Vibration (phasic)

Ruffini endings

Stretch (tonic)

Hair cells

Detect sound

Semicircular canals

Detect angular acceleration

Maculae

Detect linear acceleration

Rods

Low light vision

Cones

Color vision

Phototransduction result

Hyperpolarization of photoreceptors

Myopia

Near-sighted

Hyperopia

Far-sighted

Sympathetic nervous system

Fight or flight

Parasympathetic nervous system

Rest and digest

Preganglionic neurotransmitter

ACh (both systems)

Sympathetic postganglionic neurotransmitter

Norepinephrine

Parasympathetic postganglionic neurotransmitter

ACh

Sympathetic structure

Short preganglionic, long postganglionic

Parasympathetic structure

Long preganglionic, short postganglionic

Adrenal medulla

Releases epinephrine and norepinephrine

Hypothalamus

Controls ANS and endocrine integration

Dual innervation

Organs receive both sympathetic and parasympathetic input