Virginia Tech BMSP 2135 RAT #21

sound wave

The displacement of air molecules in response to an object moving

waves

sound waves

- The air molecules barely move from their original position

- They bump into adjacent molecules and transfer their energy, which causes those molecules to collide with others

- The energy is transmitted in _________ that radiate away from the vibrating object like ripples spreading across a pond, except that sound waves spread in three dimensions.

pitch (frequency)

number of cycles in 1 second; determined by how many times the object vibrates back and forth during a certain period

Hertz (cycles/second)

what is the unit of measurement for pitch/frequency?

Loudness

_______________ (amplitude) of a sound wave is determined by the difference between areas of high and low air pressure

Louder sounds result from the displacement of more air molecules as the object moves

decibels

what is the unit of measurement for loudness/amplitude?

auditory canal

the auricle funnels sound waves into where?

tympanic membrane

What is the first membrane to vibrate as sound waves enter the ear?

auditory ossicles

What structures are attached to the tympanic membrane?

oval window

The auditory ossicles transmit the vibrations to what structure?

amplify

Although the oval window vibrates at the same frequency as the tympanic membrane, the ossicles transmit the force from the larger tympanic membrane to the smaller oval window. This concentrates the force in a smaller area and so increases it. The ossicles also act as a lever system to ___________ the vibration of the oval window

tympanic membrane

auditory pathway

(1) when sound waves strike the _____________ ________________, movement of the connected auditory ossicles causes the oval window to vibrate at the same frequency

basilar membrane

auditory pathway

(2) vibration of the oval window produces pressure waves in the perilymph of the scala vestibuli and the endolymph of the cochlear duct, which then vibrate the ___________ ______________

high

auditory pathway

(3a) pressure waves from ______-frequency sounds travel only a short distance into the cochlea and cause the basilar membrane to vibrate where it is narrow and stiff

wide, flexible

auditory pathway

(3b) pressure waves from low-frequency sounds travel farther into the cochlea and cause the basilar membrane to vibrate where it is ______ and _______________

helicotrema

For very low-frequency sounds that we cannot hear, the waves travel all the way to the tip of the cochlea, where the scala vestibuli connects with the scala tympani at an opening called the __________________

perilymph

The movement of the round window is critical, as without it, the ______________ would not move

As the oval window is pushed into the inner ear, the round window bulges outward, and vice versa.

which area of the basilar membrane vibrates

Pitch is determined by what?

how much the basilar membrane vibrates at that area

Loudness is determined by what?

spiral organ

Regardless of which portion of the basilar membrane vibrates, the movement causes changes in the _________ ________, which rests on the basilar membrane.

hair

The spiral organ contains receptor cells called _______ cells

stereocilia

Each hair cell (receptor cells in the spiral organ) has microvilli of varying lengths known as ____________ that project from the cell into the endolymph of the cochlear duct; arranged from tallest to smallest; they are stiff but bend by flexing at the junction with the cell body

inner

spiral organ

- single row of inner hair cells

- 3 rows of outer hair cells

- 3500 (inner/outer) hair cells are primarily responsible for detecting sound

tectorial

A stiff membrane, called the _____________ membrane, sits on top of the hair cells so that they are sandwiched between the basilar and ______________ membranes

same answer

no

- The stereocilia on the outer hair cells contact the tectorial membrane

- Do the the stereocilia in the inner hair cells contact the tectorial membrane?

- When the basilar membrane vibrates up and down in response to sound waves, the hair cells move with it toward and away from the tectorial membrane.

tip link

Each stereocilium is connected to its neighbor by an elastic filament called a _____ _______. When the tallest stereocilium bends in one direction, the other stereocilia are pulled in the same direction.

tallest stereocilium

The basilar membrane moves up toward the tectorial membrane, bending the stereocilia toward the __________ _________________.

endolymph

Stereocilia of inner hair cells also bend due to movement of the _____________ between the two membranes.

potassium

Bending the stereocilia opens _________________ ion channels that depolarize the hair cell.

into the hair cells

In typical neurons, opening potassium ion channels would hyperpolarize the cell, but the endolymph contains such a high concentration of potassium ions that the gradient is reversed, causing them to flow (out of the hair cells/into the hair cells.)

This leads to depolarization and a local potential.

cochlear nerve

The depolarized hair cell releases neurotransmitters, triggering action potentials in the axon of the ____________ _________ that innervates the hair cell.

basilar membrane

the outer hair cells have an essential role in increasing the sensitivity of the inner hair cells and amplifying the vibration of the ___________ ______________.

The outer hair cells have motor proteins that allow them to generate forces that enhance the movement of the basilar membrane as much as a hundred-fold.

Vestibulocochlear nerve

What cranial nerve carries auditory signals?

primary auditory cortex

The thalamus stimulates neurons of the ___________________________________ in the superior portion of the temporal lobe; _____________________________ is where our first conscious awareness of sound begins, as well as analysis of its location, pitch, and loudness.

same answer

Conduction

_______________ hearing loss is due to a problem in the outer or middle ear that prevents sound waves from reaching the inner ear.

Examples include excessive buildup of cerumen, a middle ear infection, a perforated tympanic membrane, or fusion of the auditory ossicles.

Sensorineural

_________________ hearing loss refers to a defect in the cochlea or any of the neural pathways in the cochlear nerve or CNS.

sensory hearing loss, neural hearing loss

what are the two types of sensorineural hearing loss?

Sensory

__________ hearing loss occurs when action potentials cannot be generated in the cochlea, usually due to dysfunction of the hair cells.

stereocilia

sensory hearing loss

- Exposure to loud sounds or certain medications may damage hair cells.

- We also lose ______________ as we age, especially those in the proximal part of the cochlea that are responsible for detecting high-frequency sounds.

- Hearing aids can help mild to moderate cases of sensory hearing loss.

- A cochlear implant may also be an option

Neural

____________ hearing loss occurs when the action potentials fail to propagate through the cochlear branch of the vestibulocochlear nerve or CNS pathways.

are not

neural hearing loss

- Typical causes include strokes or tumors such as an acoustic neuroma, a benign tumor outside the brainstem at the junction of the medulla and pons.

- Cochlear implants (are/are not) effective for neural hearing loss.

external auditory canal

HEARING Big Picture

(1) the ocean waves and your friend's laugh as he falls produce sound waves that enter the what?

oval window

HEARING Big Picture

(2) sound waves cause vibration of the tympanic membrane, auditory ossicles, and ________ ___________

perilymph, endolymph

HEARING Big Picture

(3) vibration of the oval window moves the __________ and ____________ in the cochlea, which in turn causes the basilar membrane to vibrate

depolarizes

HEARING Big Picture

(4) transduction occurs when the vibration of the basilar membrane and endolymph ___________ the hair cells, triggering APs in the cochlear neurons

vestibulocochlear

HEARING Big Picture

(5) auditory signals travel through the axons of the ________________ nerve to the brainstem and eventually reach the primary auditory cortex in the temporal lobe. There, conscious awareness and analysis of the sound begin.

somatic motor neuron

Skeletal muscle fibers are voluntary and contract only when stimulated to do so by a what?

cerebrum

motor pathway that leads to a voluntary muscle contraction

(1) the CNS initiates movement—upper motor neurons in the primary motor cortex of the ____________ make the "decision" to move and initiate movement (with the help of the basal nuclei)

upper motor neurons

motor pathway that leads to a voluntary muscle contraction

(2) However, the __________ _________ ______________ do not contact skeletal muscle fibers, and so by themselves cannot stimulate muscle contraction.

lower motor neurons

motor pathway that leads to a voluntary muscle contraction

(3) Instead, the messages from upper motor neurons are relayed to these, which release acetylcholine onto the muscle fiber and initiate muscle contraction

Anterior horn of spinal cord, or the brainstem

Where is the cell body of a lower motor neuron located?

anterior root

if the lower motor neuron is located in the spinal cord, its axons would be located in which root of the spinal nerve?

Skeletal muscle fibers within a single skeletal muscle

Where does the axon of a lower motor neuron end?

cerebellum

after lower motor neurons stimulate a skeletal muscle to contract, sensory information is relayed back to the ______________ in the CNS, which will then send instructions to upper motor neurons to modify movement as needed

reflexes

Certain types of sensory-motor integration involve cooperation between multiple parts of the CNS and PNS.

Other types of integration, however, are much simpler and result in programmed, automatic responses to selected sensory input. These types of integrative responses are known as _______________.

motor

steps of a reflex arc

(1) PNS detects and delivers stimulus to CNS

(2) CNS integrates stimulus

(3) PNS delivers _________ responses from CNS to effectors

muscle spindles, Golgi tendon organs

Name two structures that detect stretch

muscle spindles

A specialized bundle of intrafusal muscle fibers innervated by sensory neurons that detect stretch

regular contractile muscle fibers (extrafusal muscle fibers)

Muscle spindles

- tapered structures that are found embedded among the what?

- within each spindle are 2-12 specialized muscle fibers called intrafusal muscle fibers ("within the spindle").

- intrafusal fibers have contractile filaments composed of actin and myosin at their poles and a central area where contractile filaments are absent.

Golgi tendon organs

Mechanoreceptors located within tendons near the muscle-tendon junction; monitor the tension generated by a muscle contraction

collagen

a Golgi tendon organ consists of an encapsulated bundle of _____________ fibers attached to about 20 extrafusal muscle fibers.

monosynaptic reflex

a reflex arc consisting of a single synapse between a sensory and motor neuron within the spinal cord or brainstem

2 (1 sensory, 1 motor)

How many neurons are involved in a monosynaptic reflex?

polysynaptic reflex

What is the term for a reflex that involves more than one synapse?

somatic

___________ reflexes involve somatic sensory and motor neurons

Muscle spindles, spinal cord

simple stretch reflexes

(1) __________ _________ detect the stretch, and primary and secondary afferents transmit an AP to the ________ _________

different answers

spinal cord (or brainstem for cranial nerves)

simple stretch reflexes

where is the signal sent?

spinal cord

simple stretch reflexes

In the _________ __________, sensory afferents synapse on α- motor neurons and trigger an action potential.

The sensory afferents synapse on α-motor neurons in the spinal cord; note that upper motor neurons are not directly involved in this process. This causes the α-motor neurons to generate action potentials.

anterior root

simple stretch reflexes

through which root does the motor neuron travel?

patellar/knee-jerk reflex

simple stretch reflexes

What is the best-known example of a stretch reflex?

nociceptor

What type of receptor detects pain?

posterior root ganglion

Where is the soma of the nociceptor neuron located?

interneurons

spinal __________________ can synapse on two different populations of motor neurons: some that supply the flexor muscles of the affected limb, and some that supply the extensor muscles of the opposite limb.

crossed-extension reflex

a polysynaptic reflex that occurs concurrently with the flexion reflex; triggers extension of the limb on the opposite side of the body from a painful stimulus

simultaneously

One motor neuron causes the hip flexor muscles of the right leg to contract. The other motor neuron causes the hip extensor muscles of the left leg to contract.

Which of the above occurs first? Or do they occur simultaneously?

interneurons

Which neuron decussates?

PNS

nociceptive afferents/sensory neurons, motor neurons are all part of the (CNS/PNS)

CNS

interneurons are part of the (CNS/PNS)

Cranial nerve reflex

The gag reflex and the corneal blink reflex are two examples of what type of reflex?

visceral motor division/autonomic nervous system (ANS)

Have you ever nearly been in an auto accident? Afterwards, you probably felt shaky out of breath and your heart was racing. What division of the PNS was responsible for those physiological changes?

yes (they work together constantly to maintain the delicate balance that is homeostasis)

Can the sympathetic nervous system and the parasympathetic nervous system both be active at the same time?

autonomic

The ________________ nervous system oversees such vital functions as heart rate, blood pressure, and digestive and urinary processes

Visceral reflex arcs

a series of events in which a sensory stimulus in an organ leads to a predictable visceral motor response mediated by the ANS

brain or spinal cord

Events of a visceral reflex arc

(1) Sensory signals from the viscera and skin are sent by afferent sensory neurons to the where?

CNS

Events of a visceral reflex arc

(2) The stimuli are then integrated by the what?

Autonomic ganglion

Events of a visceral reflex arc

(3) Next, motor impulses from the CNS are sent out via efferent motor neurons in cranial and spinal nerves. These nerves usually lead to ganglia in the PNS, called __________________ _____________.

autonomic ganglion

a collection of cell bodies of postganglionic autonomic neurons

target organs

Events of a visceral reflex arc

(4) Finally, the autonomic ganglia send the impulses via other efferent motor neurons to various _________ ____________, where they trigger a motor response in the target cells

acetylcholine

What neurotransmitter is released by somatic motor neurons?

smooth muscle cells, cardiac muscle cells, glands

unlike somatic motor neurons, autonomic motor neurons innervate what?, as well as produce involuntary actions.

do not

differences between the somatic nervous system and autonomic nervous system

autonomic motor neurons (do/do not) directly innervate their target cells.

preganglionic, postganglionic

autonomic motor neurons do not directly innervate their target cells.

- Instead, two neurons are involved.

- The first is the initial efferent neuron called the ________________ neuron, which synapses on the cell body of a second neuron, called the ____________________ neuron

two different answers

target cell

differences between the somatic nervous system and autonomic nervous system

The axon of the postganglionic neuron then synapses on the ________ _______, in which it triggers a change by releasing various neurotransmitters, including ACh and norepinephrine.

in the CNS in the spinal cord or brainstem

Preganglionic neuron soma is located where?

in an autonomic ganglion in the PNS

Postganglionic neuron soma is located where?

ganglion

Collection of neuronal cell bodies in the PNS

sympathetic and parasympathetic nervous systems

What are the two divisions of the ANS?

short, long

In the sympathetic nervous system, the preganglionic axons are often (short/long) and the postganglionic axons are generally (short/long)

long, short

In the parasympathetic nervous system, the preganglionic axons are often (short/long) and the postganglionic axons are generally (short/long)

thoracolumbar

in the sympathetic nervous system, the cell bodies of the preganglionic neurons originate in the thoracic and upper lumbar spinal cord. For this reason, the sympathetic nervous system is often called the _____________________ division.