Neurobio Final

What are the events involved in hearing?

-The auricle directs sound waves into the external auditory canal - Sound waves strike the tympanic membrane causing it to vibrate. -The vibration conducts from the tympanic membrane through the ossicles, in the following order: malleus, incus, and the stapes. -The stapes moves back and forth pushing the membrane of the oval window in and out. - The movement of the oval window establishes pressure waves in the perilymph of the cochlea (scala vestibuli). - Pressure waves in the scala vestibuli are transmitted to the scala tympani, which then pushes the vestibular membrane back and forth, which increases and decreases the pressure in the endolymph of the cochlea duct. -These pressure changes in the endolymph move the basal membrane ever so slightly, which moves the hair cells of the spinal organ against the tectorial membrane. -The bending of these hair cells produces receptor potentials that lead to action potentials, if the threshold is reached, along the cochlear nerve fibers of cranial nerve 8. -Pressure changes in the scala tympani cause the round window to bulge outward into the middle ear.

How many types of stimuli can each sensory receptor transduce?

1

What are the three ear ossicles?

1. Malleus 2. Incus 3. Stapes

What are the 2 types of equilibrium?

1. Static 2. Dynamic

Events of perception of a sensation

1. Stimulation of the receptive field of a sensory neuron 2. Transduction of the stimulus 3. Generator potential 4. Impulse generation and conduction 5. Integration of the sensory input

What is action potential?

A brief fluctuation in membrane potential caused by the rapid opening and closing of voltage-gated ion channels. Action potentials sweep like a wave along axons to transfer information from one place to another in the nervous system.

What is graded potential?

A graded potential is a wave of electrical excitation that corresponds to the size of the stimulus. Graded potentials are used by dendrites for returning signals from sensory organs.

Where are the first order neurons located?

A sensory neuron that conducts impulses from somatic receptors (periphery) to the spinal cord and the brainstem.

What is receptor potential?

A stimulus-induced change in the membrane potential of a sensory receptor.

What is a C-fiber?

An unmyelinated postganglionic fiber that provides slow nerve impulse transmission.

What are the 2 branches of Cranial Nerve 8?

Cochlear: has a spiral ganglion in the bony modiolus. Vestibular: it consists of the saccular, utricular and the ampullary nerves.

External Ear

Collects sound waves and directs them towards the external auditory canal and consists of the oracle/pinna (elastic cartilage covered with skin).

How is dynamic equilibrium accomplished?

Cristae receptors

Tympanic tube

Eustachian tube

Where do graded potentials occur?

Graded potentials are in ligand/mechanically graded ion channels, they are localized and the amplitude depends on the stimulus strength.

Where are hair cells located?

Hair cells are located in the organ of corti of the cochlea.

Where are the auditory receptors located?

In the bony labyrinth and the inner membranous labyrinth.

What is the somatic sensory system?

Input to the nervous system is provided by sensory receptors that detect such stimuli as touch, sound, light, pain, cold, and warmth.

Malleus

Located in the middle ear and it is connected to the eardrum.

**Incus**

Located in the middle ear and it is connected to the floor plate and then the oval window.

Stapes

Located in the middle ear and it is connected to the floor plate and then the oval window.

What is the difference between damage to the upper and lower motor neurons? What would the patient experience?

Lower motor neurons extend from the brain stem and spinal cord to skeletal muscles. These lower motor neurons are called the final common pathway. Upper motor neurons (UMN) extend from the cerebral cortex (frontal lobe) to the anterior horn of the spinal cord as well as the pons and the medulla. The primary motor area of the cerebral cortex is the pre-central gyrus in the frontal lobe. The neurons in the frontal lobe are quite large; they allow conscious control over voluntary movements of skeletal muscle. These neurons have very long axons and they form massive voluntary motor tracts. Most of these neurons are involved with conscious motor control (skeletal muscle) of the face, the tongue, the hands, as well as posture, reflexes and muscle tone. Motor innovations are contralateral (opposite side). The left frontal lobe controls muscles on the right side of the body and vice versa.

How is static equilibrium accomplished?

Macular receptors

Dynamic Equilibrium

Maintenance of body position (mainly the head) in response to sudden movements such as rotation, acceleration and deceleration.

Static Equilibrium

Maintenance of posture, balance and body position (mainly the head) relative to the force of gravity.

What are the additional sensory pathways that we discussed?

Major indirect tracts such as rubrospinal (tracts that originate from the red nucleus and are responsible for motor input of gross postural tone), tectospinal (a contralateral tract that is responsible for postural muscle tone associated with auditory and visual stimuli and vestibulospinal (an ipsilateral tract that is responsible for gross postural adjustments in response to head movements).

Can hair cells regenerate?

No

What are postganglionic axons in the parasympathetic and sympathetic systems?

Postganglionic Neuron: the second neuron in the autonomic motor pathway, the cell body and dendrites are located in autonomic ganglia, where they synapse with one or more preganglionic fibers. They are non-myelinated Axon fibers of a postganglionic neuron terminates in a visceral effector organ

What are preganglionic axons in the parasympathetic and sympathetic systems?

Preganglionic Neuron: the first of two autonomic motor neurons, the cell body is located in the brain or spinal cord and they are myelinated axons, which usually extends to an autonomic ganglion where it synapses with the postganglionic neuron 1. The cell bodies of Sympathetic preganglionic neurons are located in the lateral gray horns of the T1 through L2 segments of the spinal cord.

What are its functions and responsibilities of the somatic sensory system?

Sensory receptors change sensory stimuli into nerve signals and the information conveyed in these signals is then processed by the nervous system. The components of the brain interact to receive sensory input, integrate and store the information, and transmit motor responses.

Where are sympathetic ganglia located, what types are there and what are 3 possibilities for synapse in these ganglia?

Sympathetic ganglia is the flight or fight response in stress, fright or anger. They are located in a vertical row on either side of the vertebral column Two types of sympathetic ganglia are the Paravertebral Ganglia and the Prevertebral ganglia. Three possibilities for synapse are: it may synapse with postganglionic neuron in the ganglion it first reaches (this is the preferred mode of travel), it may ascend or descend to a higher or lower ganglion before synapsing with postganglionic neurons at a different level or it may continue, without synapsing, through the sympathetic trunk ganglion, becomes a splanchnic nerve, and proceeds to a prevertebral (collateral) ganglion where it synapses with the postganglionic neuron.

Where are second order neurons located?

Synapses with a first order neuron in the brainstem which will conduct impulses from the spinal cord and the brainstem up to the thalamus

Where are third order neurons located?

Synapses with a second order neuron in the thalamus. They relay impulses from the thalamus up to the somatosensory cortex (post-central gyrus) of the cerebrum where the conscious perception of the sensation is elicited.

What is autonomic tone?

The balance between the parasympathetic and sympathetic activity.

What cranial nerves are involved in hearing?

The cranial nerve involved is cranial nerve 8.

What are the general somatic senses?

The general somatic senses are touch, pressure, vibration, itch, tickle, warmth, cold and pain. They arise from receptors located in the skin as well as proprioception. For example pressure sensitive receptors found in large muscular arteries that regulate blood pressure are baroreceptors, they are located in the aorta, carotid.

What is one main function of the hypothalamus?

The hypothalamus controls and integrates the autonomic nervous system.

What is the posterior column medial lemniscus pathway?

The medial lemniscus extends from the medulla to the thalamus to the somatosensory cortex. This pathway carries discrete signals of the posterior columns of the spinal cord decussates to the medulla, it will ascend into the thalamus. The nerve impulses for conscious proprioception and most tactile sensations ascend to the cortex along a common pathway formed by three-neuron sets. These neurons are a part of the posterior columns which consist of the gracile fasciculus and cuneate fasciculus. 1. Impulses conducted along this pathway are concerned with fine touch, proprioception, and vibratory sensations.

What is a motor pathway?

The motor pathway of the spinal cord is: Lower motor neurons -> right anterior corticospinal tract -> spinal cord and left lateral corticospinal tract -> pyramid and decussation in the medulla -> upper motor neurons -> through the midbrain to the right side of the body

What are the parasympathetic ganglia, where are they located and what types are there?

The parasympathetic ganglia are the autonomic ganglia, they are the rest and digest responses that conserve and restore body energy, digest and absorb nutrients, and eliminate waste products They are located very close to or actually within the wall of a visceral organ The main types of parasympathetic ganglia are terminal ganglia.

What region of the nervous system controls defecation and urination?

The parasympathetic rest and digest response.

What is the function of hair cells?

Their function is to generate receptor potentials because they convert mechanical energy into electrical energy.

How many hair cells are in each ear?

There are 15,000 hair cells in each of our ears.

How much do nociceptors adapt to stimuli?

They adapt very little or not at all because it allows the patient to keep being informed of the damaging stimulus and to seek treatment.

How are receptors classified?

They are classified microscopically, by location and by the type of stimulus detected.

Where are proprioceptors located?

They are located in skeletal muscles, tendons, joints, ligaments, in CT coverings of bones and muscles, in and around joints, and in the internal ear and are stimulated by stretching or movement.

What do dual innervations indicate?

They are organs that receive impulses from both sympathetic and parasympathetic fibers. Examples are the heart, blood vessels, kidney and lungs; one system overrides the other.

What type of modalities do proprioceptors detect?

They provide information about body position, muscle tension, joint position and equilibrium.

What are proprioceptors?

They transmit nerve impulses related to muscle tone, movement of body parts, body sensation and balance.

What is the visceral efferent pathway?

They transmit nerve impulses to three effector organs, which are glands, smooth muscle and cardiac muscle. Two divisions that distribute visceral outflow from the CNS are: the Sympathetic (Thoracolumbar) and the parasympathetic (Craniosacral). The visceral motor neurons regulate visceral activities by either exciting or inhibiting ongoing activities of effector organs. These two systems generally have opposing actions one stimulates the other one inhibits.

Do graded potentials get stronger or weaker as they travel along nerve fibers?

Weaker. They last for several milliseconds to several minutes.

Ruffini corpuscles

a single encapsulated myelinated nerve ending with multi- branched or sprayed axonal endings. Large receptor fields, slowly adapting. They represent 20% of the mechanoreceptors in the hand. They are found in the skin, ligaments and tendons. They are important in signaling heavy, continuous touch and pressure. They are important in regulating the degree of joint rotation.

Receptive Field

area with in which a stimulus of appropriate quality and strength will cause a sensory neuron to initiate a nerve impulse.

Hair cell receptors

auditory receptors, they generate receptor potentials because they convert mechanical energy into electrical energy. There are outer and inner hair cell receptors that make up the cranial nerve and contract upon electrical stimulation.

What are the parts of the bony labyrinth?

cochlea, vestibule, semicircular canals

Inner Ear

contains a complicated series of canals and consists of the bony labyrinth and the inner membranous labyrinth.

Transduction

conversion of the stimulus.

Nociceptors

detect damage to the tissues whether physical or chemical. They are naked nerve endings

Tympanic membrane

ear drum

Meissner's corpuscles

encapsulated nerve endings that elicit large myelinated sensory nerve fibers, they have small receptive fields and they rapidly adapt. They are found in the thermos of the skin, mostly non-hairy parts of the skin (lips, fingertips, palms of the hands, and soles of the feet. They provide for 40% of the 6sensory innovation to your hands. They are sensitive to weak stimuli. They are actually myelinated axon terminals that are formed by flattened Schwann cells.

Merkel's discs

flattened portions of dendrites of sensory neurons. They contact the stratum basale. Small receptor fields, slowly adapting. They provide for 25% of all mechanoreceptors are Merkel's disc. They are densely populated in the lips, fingertips, genitalia. They are found in association to hair follicles. Since they are slowly adapting they detect continuous touch of objects against the skin. They are important in determining the texture

Free nerve endings

found everywhere in the skin and they detect pain (nociception), temperature, itch, tickle, touch, pressure and stretch

Middle Ear

it consists of an air-filled cavity in the temporal bone of the cranium, the round windows and the oval windows.

Pacinian corpuscles

lie in the dermis, hypodermis (subcutaneous level), and in deep fascial tissues; only stimulated by very rapid movements of the tissues; they adapt at a few hundredths of a second, rapid adapting. They represent 15% of the mechanoreceptors of the hand. They are important in detecting tissue vibrations. They are a myelinated afferent axon terminal surrounded by layers of lamella. They contain a lymph-like fluid inside.

What are the three parts of the ear?

outer, middle, inner

What parts of the brain make you aware of and able to remember the taste of coffee for example?

sensory memory

First Order Neuron

sensory neuron that conducts impulses from somatic receptors (periphery) to the spinal cord and the brainstem.

Where are nociceptors located?

skin; there is a very high concentration of nociceptors in our bones; also located in anterior walls and joint surfaces. Most other deep tissues are not extensively supplied with pain receptors

What type of modality do nociceptors detect?

stimulated and produce pain at temperatures below 10 degrees C and above 48 degrees C

Separate cells

synapse with first order neurons located in sense organs; hair cells in the ears, rods and cones in the retina (eyes) and gustatory receptor cells on taste buds.

Second Order Neuron

synapses with a first order neuron in the brainstem which will conduct impulses from the spinal cord and the brainstem up to the thalamus.

Third Order Neuron

synapses with a second order neuron in the thalamus. They relay impulses from the thalamus up to the somatosensory cortex (post-central gyrus) of the cerebrum where the conscious perception of the sensation is elicited.