DECK 1: Neurophysiology Flashcards

What are the six major types of sensory receptors?

Mechanoreceptors → touch, pressure, vibration

• Thermoreceptors → temperature

• Chemoreceptors → chemicals

• Photoreceptors → light

• Nociceptors → pain

• Proprioceptors → body position and movement

What is the difference between Meissner’s corpuscles and Pacinian corpuscles?

Meissner’s corpuscles

• Light touch

• Located near skin surface

• Small receptive field

Pacinian corpuscles

• Deep pressure

• Vibration

• Located deeper in dermis/hypodermis

Meissner = Mild touch

Pacinian = Pressure

What is membrane potential?

The electrical difference between the inside and outside of a cell membrane caused by unequal ion distribution.

What is the resting membrane potential

Approximately -70 mV

What is the 3:2:1 rule of the sodium-potassium pump?

Every cycle:

• 3 Na⁺ OUT

• 2 K⁺ IN

• Uses 1 ATP

Easy memory:

3 Out → 2 In → 1 ATP

Why is the sodium-potassium pump important?

It maintains the resting membrane potential and restores ion balance after action potentials.

What is threshold stimulus

The minimum stimulus needed to trigger an action potential.

Approximately -55 mV

List the steps of an action potential in order.

1. Resting membrane potential

1. Threshold reached

2. Depolarization

3. Repolarization

4. Hyperpolarization

5. Return to resting state

What causes depolarization?

Voltage-gated sodium channels open.

Na⁺ enters the neuron.

The inside becomes more positive.

What causes repolarization?

Voltage-gated potassium channels open.

K⁺ leaves the neuron.

The membrane becomes negative again.

What causes hyperpolarization?

Potassium channels stay open slightly longer than necessary.

Too much K⁺ leaves, making the cell more negative than resting potential.

What is the absolute refractory period?

The neuron cannot fire another action potential, no matter how strong the stimulus.

What is the relative refractory period?

The neuron can fire again, but only if the stimulus is stronger than normal.

What are the three causes of local potential changes

1. Mechanical stimulation

2. Chemical stimulation

3. Opening or closing of ion channels (ligand- or voltage-gated)

What is an EPSP?

Excitatory Postsynaptic Potential

• Depolarizes the neuron

• Makes it more likely to fire

• Usually caused by Na⁺ entering

What is an IPSP?

Inhibitory Postsynaptic Potential

• Hyperpolarizes the neuron

• Makes it less likely to fire

• Often due to K⁺ leaving or Cl⁻ entering

EPSP vs IPSP

EPSP	IPSP
Excitatory	Inhibitory
Depolarization	Hyperpolarization
More likely to fire	Less likely to fire

What is temporal summation?

One presynaptic neuron fires repeatedly over time until threshold is reached.

Think: TIME

What is spatial summation?

Multiple presynaptic neurons fire simultaneously to reach threshold.

Think: SPACE

Temporal vs Spatial Summation

Temporal:

• One neuron

• Multiple impulses

• Over time

Spatial:

• Multiple neurons

• Same time

• Combined effect

What is convergence?

Many neurons send signals to one neuron.

Many → One

What is divergence?

One neuron sends signals to many neurons.

One → Many

What is the difference between the Nernst and Goldman equations

Nernst Equation

• Calculates equilibrium potential for one ion

Goldman Equation

• Calculates membrane potential using multiple ions

Memory:

Nernst = One

Goldman = Many

How does synaptic transmission occur?

1. Action potential arrives

2. Ca²⁺ channels open

3. Calcium enters

4. Vesicles release neurotransmitter

5. Neurotransmitter binds receptors

6. Response occurs in the next cell

How are neurotransmitters removed from the synaptic cleft?

Three ways:

1. Reuptake

2. Enzymatic degradation

3. Diffusion

What are the Nodes of Ranvier?

Gaps between myelin sheath segments where ion exchange occurs.

Why are the Nodes of Ranvier important?

They allow saltatory conduction, where the action potential “jumps” from node to node, greatly increasing conduction speed.

Sensory neuron vs Interneuron vs Motor neuron

Sensory (Afferent):

Carries information to the CNS.

Interneuron:

Found in the CNS; connects neurons.

Motor (Efferent):

Carries commands from the CNS to muscles or glands.

What is frequency coding

A stronger stimulus is represented by a higher firing rate of the same neuron

What is population coding

A stronger stimulus is represented by recruiting more neurons to fire.

What are the five parts of a reflex arc?

1. Receptor

2. Sensory neuron

3. Integration center

4. Motor neuron

5. Effector

What is an alpha motor neuron?

Innervates extrafusal skeletal muscle fibers and causes muscle contraction.

What is a gamma motor neuron?

Innervates intrafusal muscle spindle fibers and maintains muscle spindle sensitivity.

Extrafusal vs Intrafusal fibers

Extrafusal

• Main muscle fibers

• Produce force

Intrafusal

• Muscle spindle fibers

• Detect stretch

What are locomotor pattern generators?

Neural circuits in the spinal cord that generate rhythmic movements such as walking.