Human Phys Post Lab Quiz-Action Potentials

Where are sensory receptors located?

Dendrites

Contaneous receptors

Eyes, ears, nose, mouth and skin

Where do sensory neurons send action potentials

Central nervous system

What does the central nervous system do?

Process action potential: interprets and precieves sensation

What does sensory acuity mean?

Ability to precisely locate and distinguish one stimulus from another; sharpness of preception

What two factors effect sensory acuity?

Size of receptor field and lateral inhibition

Size of receptor field

Varies inversely with the number of receptored contained in field

Smaller the receptor field

The greater the density of receptors

Increase receptor field

decrease density of receptors

Two point discrimination

The point at which the distance we can distinguish two separate sensations

What is lateral inhibition

Receptors where touch is the strongest are stimulated more than areas where touch is lighter.

Receptors that are most strongly stimulated inhibit those around them

This allows us to percieve well-defined sensation at a single location instead of “fuzzy” boarder

phasic receptors

Touch and pressure:

-adapt quickly

-respond when stimulus first applied

-cease to respond

-some may produce second response

-recognize changes in stimuli

tonic receptors

-Adapt slowly

-Continue to produce response as long as stimulus persists

-stimuli that require constant monitoring

Examples of tonic receptors

pain, stretching

Referred pain

Visceral pain felt at a site other than place of origin

Why does visceral pain occur?

both somatic sensory and visceral sensory coverage are on the same tract.

Anatomy of the ear

Anatomy of middle ear

Anamtomy of Cochlear Duct

Sound frequency-pitch

The amplitude of the sound wave does not change but frequency does

Higher pitch

Higher frequency

Conduction deafness

Movement of sound waves through external and middle ear is interrupted

Impairs hearing at all frequencies

Sensorineural deafness

Transmission of nerve impulses is impaired from damage to inner hear and neural components.

Impairs hearing at some frequencies more than others.

Function of dendrites

Receive incoming signals

Function of node of Ranvier

action potential jumps

Myelin sheath

Insulates neuron

Schwann cells

Lays myelin in peripheral nervous system

Oligodendrocytes

Lay myelin in CNS

Speed of action potential in unmyelinated region of neuron

Slower (1 m/s)

Speed of action potential in myelinated region of neuron

Fast (300 m/s)

Function of the axon hillock

Trigger zone

Function of axon

Propagates action potentials

Neuron

Functional unit of the nervous system

What is the resting membrane potential

The membrane potential when neuron is inactive/at rest

What is the value of the resting membrane potential

-70 mV

Membrane potential

The difference in charge across the membrane

Inside the membrane

Negative

Outside the membrane

Positive

What is the resting membrane potential established by

1. More K leak channels than Na ion pumps

2. Na/K ATPase: 3 Na out, 2 K in

3. Anionic molecules in the cell (DNA, proteins, ATP)

Action potential

How neurons communicate

What does it mean that action potentials are unidirectional?

only travel in one direction

Depolarization

More positve, increase membrane potential

What causes depolarization?

Voltage Na channel open- large influx of Na

Repolarization

Decrease membrane potential; becomes more negative

What causes repolarization

Na voltage gated ion channels are inactivated, K ion channels open and K flows out of cell

Hyperpolarization

Overshot of resting membrane potential

What causes hyperpoalrization?

K ion channel are slow to close

At low resting membrane potential what is the permeability of Na and K

Low Na permeability, higher K permeability

At depolarization what happens to Na permability

Increases

What happens to Na and K permeability during repolarization?

Decrease in Na permeability and increase in K permeability

What happens to Na and K permeability during hyperpolarization?

Low Na permeability, K permeability slowly decreases

Refractory periods

Recovery time after responding to stimulus

Absolute refractory period

Absolutely no action potentials no matter how strong the stimuli

What causes the absolute refractory period

Inactived Na channels

Relative refractory period

Action pontential requirs an extra strong stimulus

What causes the relative refractory period

Continued outward diffusion of K

Propagation

Movement of action potential down axon and is unidirectional

Continous conduction

Unmyelinated neurons. Action potential is generated at every point down the axon until it reaches the end

Saltatory conduction

Myelinated neurons. Action potentials generated at nodes of Ranvier, much faster AP

All-or-none principle

A graded potential needs to reach threshold in order to trigger an action potential. Amplitude does not change but frequency does

Supthreshold

No Action potential

Thershold

Action potential

Suprathreshold

Action potential with increased frequency

Oscilloscope

Plots electrical potential over time

Exteroceptors

Receptors that receive stimuli from outside the body

Interoceptors

Receptors that are located deep within muscles tendons and other structures and which detect changes within the body

Weber’s law

The size of the just noticeable difference is a constant proportion of the original stimulus.

Referred pain

Perception of pain in one area of the body when another area is actually receiving the painful stimulus

Trigeminal nerve

Divides into the opthalmic, maxillary, and mandibular brances

Rinne Test

Compares air conduction of sound with bone conduction of sound

Autogram

A pure tone audiometer that is an instrument for measuring hearing acuity

In the Wber Test if an individual suffers from conduction deafness

The sound will be heard louder in the deaf ear than in the normal ear because in the normal ear the sound wil be partially masked by environmental noise to which the defective ear is less sensitive

In the weber test if an individual has sensorineural deafness

The sound will be heard better in the normal ear than in the deaf ear because neurla activity is essentail for hearing

In the Rinne Test if someone has conduction deafness

They will hear the sound as long as or longer through bone conduction than through air condution

In the Rinne Test, if someone has sensorineural deafness

Will hear the sound longer through air conduction than through bone conduction but usually requires a louder sound to hear at all.

Where are high pitch sounds found?

Closer to base (cross coclear duct)

Where are low pitch sounds found

Cross cochlear duct at apex