BIO 225 Unit 2: Chapter, "Nervous Coordination Continued"

Basic path of a signal through sense organs

1. Sensor stimulation

2. Stimulation translated to AP

3. AP interpreted in the brain

How can you stimulate the optic nerve?

Light and pressure

How can you stimulate auditory nerves?

Perceive action potentials as sound

Our perception of our environment depends a lot on what?

The nerves those signals are traveling on

What is the “common language of the nervous system”?

Action potential

What are the main categories of receptors?

1. Chemoreceptors

2. Mechanoreceptors

3. Photoreceptors

4. Thermoreceptors

5. Nociceptors

6. Electroreceptors

7. Magnetoreceptors

8. Itch receptors

Chemoreception

The ability to respond to chemicals

Where in the body do we respond to chemicals (i.e. chemoreceptors)?

Smell and taste

Mechanoreception

The ability to respond to mechanical stimulus (pressure)

Mechanoreceptors in mammals; what does it do?

Mammalian ear; responds to auditory signals

Mechanoreceptors in fish; what does it do

Lateral line; allows spacial awareness and balance using sound waves in the water

Types of mechanoreceptors in the body

Stretch receptors and Touch receptors

Stretch receptors; where are they found and what do they do?

Found in muscles; adapts movement based on environment

Stretch receptors tend to be ________; what do they send signals to; a good example of this is the what?

Dendrites; Sends signal to a neuron, which passes it down as an AP; example is the Reflex Arc

Touch receptors; where are they found and what do they do?

Found in the skin; responds to mechanical stimulation, such as pressure, vibration, and movement

Photoreceptors

Receptors that respond to photons

Where are photoreceptors found?

The eyes

Thermoreceptors

Receptors that respond to temperature

Where are thermoreceptors generally found?

The skin

Nociceptors

Receptors that respond to pain

Intense stimulation/pain can relatively be felt by what receptors?

Any receptor

What disease often caused people to lose a sense of pain in the Bible?

Lepresy

Electroreceptors

Receptors that response to electrical fields/bioelectricity

What animal is known for having a lot of electroreceptors? What specific structure detects these signals

Sharks; the ampullae of Lorenzini

Magnetoreceptors

Receptors that respond to the Earth’s magnetic field

What animals are known for using magnetoreceptors? What is associated with following magnetic fields?

Birds, fish, and sea turtles; migration

Itch receptors

Receptors that respond to chemicals/histamines

What white blood cell secretes histamines?

Basophils

What does histamine do? What is this associated with?

It causes capillaries to leak; can cause allergic reactions

How do allergic reactions occur?

Basophils secrete the chemical histamine, which causes capillaries to leak and allow WBCs like Neutrophils to attack substances they perceive to be harmful. Sometimes, these substances they attack are not harmful to the body, but the body still perceives it at painful, and the attacking of it causes irritation (allergic response).

Most receptors are activated ________.

Chemically

What do odorant molecules bind to?

Receptors in the cilia in the nose

What receptors can also respond to odorants?

G-Protein receptors

What are the 4 types of tastebuds/receptors in the tongue?

Sweet, Sour, Salty, Bitter

What is the relatively new type of taste bud; what does it respond to?

Umami; savory flavors

Tastebuds are _______, but they are not ________.

Sensors, Neurons

How does “tasting” work?

Tastebuds release a neurotransmitter that sends a signal down a neuron to the brain, which interprets the taste.

Do tastebuds get replaced? How often?

Yes; very often

Why is it good that tastebuds are not neurons?

1. If our tastebuds were neurons, and we ate something spicy, we would never taste anything else for the rest of our lives.

2. Because our tastebuds are not neurons, they can adapt to like new flavors, or previously disliked food.

What taste are tastebuds especially sensitive to? Why?

Bitter; because bitter tastes often alert the body to potentially toxic or harmful substances.

Is it always bitter tastes that alert the body of harmful substances?

No; It can be a combination of tastes to generate a generally unpleasant or awful taste

All nociceptors are ____ nerve endings, meaning what?

Free; they are unspecialized and detect a range of stimuli

Where are nociceptors usually found; where can you find a lot of them in?

Everywhere; beneath the skin or surrounding other tissues.

Aside from simply “pain”, nociceptors will respond to any kind of what?

External or internal pressure that is damaging to the body.

What is a corpuscle?

Nerve endings with a capsule surrounding it;

What does a corpuscle start with? What opens first?

A mechanically-gated ion channel; pressure receptors open first.

What nerve endings respond to pressure?

Pacinian Corpuscles

Pacinian corpuscles are used for _________ and responding to _________ or _________.

Adaptation, pressure, vibration

What nerve endings respond to light touch?

Meissner’s Corpuscles

What will pressure receptors in the Pacinian corpuscles begin to do over time at the receptor level and at the CNS level? What is this an example of?

Receptor level: Close/inactivate

CNS level: ignore stimuli

Example: Adaptation

Who invented anesthesia?

William Morton

Examples of pain modulation in the body

Gate control theory and Sympathetic ANS stimulation

What is the gate control theory?

Nociceptor and fiber transmit pain from periphery to the CNS, which stimulates beta fibers, and thereby transmits mechanical stimulation; this causes you to rub your knee. If this mechanical pressure overwhelms the pain sensors themselves, it can send just a pressure signal to the NS, and reduce the pain more quickly.

What, sometimes, is the relationship between nociceptors and the Sympathetic response system/stimulation?

In a fight or flight response, the SNS competes with nociceptors, sending signals that interrupt pain transmission.

What specifically happens to cut off a pain signal?

Coming from the periphery, when a pain signal enters through an afferent nociceptive fiber into the brain, a NT fiber releases norepinephrine or serotonin to a connecting pain interneuron, causing it to cut off the pain signal.

What kind of receptors are in the ear?

Mechanoreceptors

Functions of the ear

1. Hearing

2. Equilibirum

A tympanum is commonly referred to as an:

Eardrum

How does “hearing” work?

1. Sound waves enter ear through the auditory canal and vibrate the tympanic membrane (eardrum).

2. Those sound waves then transfer to the middle ear bones (malleus, incus, and stapes); when the ear drum vibrates, it triggers the malleus to send signals to the stapes.

3. In the stapes the signal hits the oval window, which sends the vibration to the cochlea through the fluid in the vestibular and tympanic canals.

4. When the canals receive the signal, it vibrates the epidermal layer beneath the cochlear duct, also known as the “Organ of Corti”. Hair cells in this membrane will move and stimulate the tectorial membrane, where there are auditory receptors.

5. This sends a signal down the cochlear nerve to the brain

List the path of an auditory signal from the auditory canal to the brain

Auditory canal, tympanic membrane (eardrum), middle ear, malleus, stapes, oval window, cochlea, vestibular and tympanic canals, epidermal layer, Organ of Corti, hair cells, tectorial membrane, auditory receptors, cochlear nerve, brain.

What drains the fluid from the middle ear?

Eustachian Tubes

It is hypothesized that lower vibrations vibrate ________ along the ______, near _______ ______ _____.

Further, cochlea, auditory nerve fibers

It is hypothesized that medium vibrations vibrate ________ along the ______

Halfway, cochlea

It is hypothesized that higher vibrations vibrate ________ along the ______, near the _______ ______

Closer, cochlea, oval window

The lower the number the ________ the soundwaves

Deeper

What could cause the tympanum to vibrate a great deal?

Really loud sounds

Ways to develop hearing loss through vibration or sound

1. Disarticulation

2. Modification to hair cells in the Organ of Corti

Disarticulation

Middle ear bones become disjointed and fail to fit together properly; the tympanum is still functional, but because the middle ear cannot transfer the vibration to the cochlea, hearing becomes limited.

How can the modification of the hair cells within the Organ of Corti affect hearing?

The hair cells are how soundwaves are mechanically transferred to the mechanical signals that are sent to the brain; therefore, if the hair cells are damaged, certain frequencies might be hard to hear.

Equilibrium is a function of the:

Ear

What gives animals such as jellyfish or crayfish positional information (where it is in relation to its environment)?

The statolith

What is a statolith?

A calcium ball that will move around according to the animal’s movements. It’s oriented on top of a bunch of different cilia; the cilia will tell the animal’s body where it is in relation to its environment.

What structures in the human ear is associated with equilibrium; where are they found?

The semicircular canals, saccule, and utricle; found in the inner ear

What is the function of the semicircular canals?

They provide rotational information; there is fluid in cilia, and as the fluid moves, it orients the human body

What is the function of the saccule and utricle

They provide positional information; they both have statoliths, like the jellyfish, that press on the cilia to orient the body to its environment.

What do the semicircular canals, saccule, and utricle ultimately provide when working together?

Balance

What is the utricle in fish called?

Lagena

What are the 3 main things the inner ear does?

1. Hearing

2. Rotational/positional information

3. Balance

What type of receptors are associated with “seeing”?

Photoreceptors

Main structures of the eye

Lens, pupil, cornea, iris, aqueous humor, inner chamber with vireous humor, fovea centralis, optic nerve, retina

Cornea

Outer layer of eye

Pupil

Not a structure, it is an opening

Iris

Part of the eye that has pigment and muscle contracts and relaxes the pupil size

What structure of the eye is responsible for changing pupil size?

The iris

The aqueous humor; what is it between?

Part of the eye with liquid; the lens and the cornea

Where is the best visual acuity in the eye?

Fovea centralis

When light hits the ______ _____, it creates a blind spot

Optic nerve

Where does the aqueous humor drain its fluid?

The canal of Schlemm

If the aqueous humor does not drain properly through the canal of Schlemm, what happens? What does it especially put a lot of pressure on, and what can it lead to?

Fluid pressure builds up, causing the disease glaucoma; puts a lot of pressure on the optic nerve; can eventually lead to blindness.

What can you do to combat glaucoma?

Put stints in the Canal of Schlemm to drain the fluid

What does some of the fluid from the aqueous humor become after it is drained by the canal of Schlemm?

Some of the fluid becomes tears

What are the “rods” in the eyes?

They ae photoreceptors for non-color vision (low light intensities)

What does the eye take in, what does it convert it into?

The eye takes in photons and converts a photo signal into an electrical signal

Surrounding the rods, there are flattened out membrane structures called _______, where the chemical reaction takes place

Disks

Describe the process of seeing with rods in the light

1. Surrounding the rods, which act as photoreceptors, there are disks. The plasma membrane of the rods have a structure called Opsin (protein) and Retinal (derivative of vitamin A).

2. Opsin and Retinal bind to form Rhodopsin in the disks. When light hits Rhodopsin, Retinal undergoes a chemical configuration, from cisconfiguration (bent) to transconfiguration (straight).

3. This triggers the enzymatic activity of Opsin, which alters the signaling of the NT molecules

Describe the process of seeing with rods in the dark

1. Rhodopsin separates, cleaving opsin and retinal in a process known as “bleaching”

2. Retinal converts back from its trans. configuration to its cis. configuration

3. Retinal in its cis. configuration then rebinds with opsin

Why does Rhodopsin have to bleach in order for the rods to see in the dark?

Because Rhodopsin is a binding of opsin and retinal in its trans. configuration, and retinal can only process light in its cis. configuration; therefore Rhodopsin must break down and separate so that retinal can revert to its cis. configuration before binding again with opsin.

What is Rhodopsin unable to do while bleached?

It cannot respond to light photons

What is there a high concentration of in the Flovea centralis?

Cones

Where in the eye is there a high concentration of rods and cones?

In the back