nervous system sensory systems - napa valley college · middle ear consists of the: the tympanic...

Nervous System – Sensory Systems

Biol 105

Lecture 11

Chapter 9

Copyright © 2009 Pearson Education, Inc.

1. Depolarization is caused by ______ ions entering or

leaving (which one) the axon

1. The gap in between two neurons is called the

________.

2. What is the name for the chemicals that are held in

vesicles and released from one neuron, and bind to

receptors of the next neuron?

3. What part of the autonomic nervous system stimulates

digestion?

4. What is the thin outer layer of the cerebrum where most

of the higher thinking and processing takes place called

5. The part of the brain that processes sensory

information (except smell) is called the ______.

Concepts to Know:


Outline

I. Senses

II. Sensory receptors

III. Touch

IV. Vision

V. Hearing and balance

VI. Smell


Senses

Major senses – touch, hearing, smelling, taste,

and seeing.

All the sensory nerves are routed through the

thalamus except the nerves for smell.


Sensory receptor cells

Sensory receptors are specialized structures

that detect stimuli (stimulus)

Sensory receptor cells change the stimulation

into an electrical response that is transmitted

through the nerves

If a sensory receptor is continuously

stimulated, it will stop responding = sensory

adaptation

12.2 The Central Nervous System

12-18


Touch

We can sense different things through

touch:

Thermal

Tactile

Pain

Vibration


Figure 9.2 Sense receptors of the skin


Types of receptors in the skin

Free nerve endings

Merkel disks

Meissner’s corpuscles

Pacinian corpuscles

Ruffini corpuscles

Thermoreceptors


Free Nerve Endings

Free nerve endings – tips of dendrites of

sensory neurons (free nerve endings may be

wrapped around hair), detect touch and pain


Figure 9.2 Free nerve endings


Merkel Disks

Merkel disks – comprised of free nerve endings

and Merkel cells, detect touch


Merkel disk


Meissner’s corpuscles

Meissner’s corpuscles – encapsulated nerve

endings - detect light touch, tell us exactly where

we were touched


Meissners corpuscle


Pacinian corpuscles

Pacinian corpuscles – layers of tissues surround

the nerve ending, detects pressure when first

applied, important in sensing vibration


Pacinian corpuscle


Ruffini corpuscles

Ruffini corpuscles – encapsulated nerve endings in

deep layers that respond to continuous pressure


Ruffini corpuscle


Thermoreceptors

Thermoreceptors – specialized nerve endings,

detects changes in temperature.


Vision

Sight is complex:

Light enters the eye, it is focused, then the

light has to be transformed into it into an

electrical signal that then has to be

processed.


Vision

Light enters through the cornea

The lens focuses it to the back of the eye

The retina is a layer at the back of the eye

where light is transformed into electrical

signals

Copyright © 2009 Pearson Education, Inc. Figure 9.4

Retina

FoveaOptic disk

(blind spot)

Optic nerve

Choroid

Sclera

Vitreous humor

(fills the posterior

chamber)

Iris

Ciliary body

Pupil

Cornea

Aqueous humor

(fills the anterior

chamber)

Sclera

Lens


Layers of the Eye – Outer layer

The sclera

Protects and shapes the eye

Provides attachment for muscles

The cornea

Allows light to enter


Outer Layer of Eye

Table 9.1 (1 of 4)


Middle Layer of Eye

The choroid

Contains blood vessels that supply nutrients and

oxygen.

Contains melanin, absorbs light reflected from the

retina

The ciliary body

A ring of muscle that functions to focus the lens on

the retina


Middle Layer of Eye

The iris

The colored portion of the eye

Contains smooth muscle that dilates or constricts

to regulate the amount of light entering the eye

The pupil

The opening in the center of the iris that lets light

into the eye


Middle Layer of the Eye

Table 9.1 (2 of 4)


Inner Layer of Eye

Contains:

Retina

Photoreceptors - Rods and Cones

Fovea


Inner Layer of Eye - Retina

The retina contains photoreceptors

Rods

Cones – detect color

The fovea is a pit in the retina with a high

concentration of cones


Vision Depends on the Eye

Table 9.1 (3 of 4)


Structures of the Eye

Optic Nerve

Fluid

Aqueous humor

Vitreous humor

Lens


Optic Nerve

The optic nerve

Carries visual information to the brain

Forms a blind spot where it leaves the retina


Fluid in the Eye

There are two fluid filled chambers in the eye

Vitreous humor – jelly like fluid in posterior

chamber. Holds retina against the wall of the

eye

Aqueous humor – clear fluid in anterior

chamber. Supplies nutrients and oxygen to

cornea and lens, removes the waste. Creates

pressure in eye to maintain shape of eye.


Lens

The lens can change shape to focus on

near and far objects.

Focuses the light onto the retina

Ciliary muscles are attached to lens by

ligaments


Vision Depends on the Eye

Table 9.1 (4 of 4)


Photoreceptors

Cones and Rods have pigments that

absorb

Cones work best in bright light and provide

color vision

Rods work in low light situations but can only

provide black and white vision


Photoreceptors

The photoreceptors (rods and cones) have

pigments that absorb light

When there is no light coming in, they are

releasing neurotransmitters (opposite of most

receptors)

When they absorb light they stop releasing

neurotransmitters


Photoreceptors

The neurotransmitters are inhibitory

When the neurotransmitters diminish, cells

that process the information are stimulated

This information from these cells (bipolar and

ganglion cells) is transmitted to the optic

nerve to the thalamus to the visual cortex

Copyright © 2009 Pearson Education, Inc. Figure 9.8a

(a) Light enters the left eye

and strikes the retina.

Light

Retina

Choroid

Sclera

Blind spot

Copyright © 2009 Pearson Education, Inc. Figure 9.8b

Ganglion

cell layer

Bipolar

cell layer

Retina

Photoreceptor

cells

Pigment layer

Choroid

Sclera

Rod

Electrical

signals

Axons

Cone

Light

Vitreous

humor

Copyright © 2009 Pearson Education, Inc. Figure 9.8c

(c) The axons of the ganglion cells leave the eye at the blind spot,

carrying nerve impulses to the brain (viewed from below) by means

of the optic nerve.

Retina

Light

Optic nerve

Visual cortex


Rods and Cones

Figure 9.9 (2 of 2)

Rod cell

Cone cell


Which part of the human eye detects colored light?

1. Pupil

2. Rods

3. Cones

4. Cornea


A ring of muscle that functions to focus the lens on

the retina is the:

1. Iris

2. Choroid

3. Ciliary body

4. Sclera


Figure 9.10 A standard test for color blindness


Vision

Vision is much more complicated because

these signals have to be processed into a

3-D image


Hearing

Sound enters the ear canal and hits the tympanic

membrane (ear drum).

The tympanic membrane vibrates.

This causes small bones in the ear to vibrate.

These bones focus and amplifies the vibrations

onto a small place (oval window) on the cochlea.

The cochlea is a fluid filled coiled membrane.

The vibrations shakes the fluid in the cochlea


Three regions of the ear

Outer ear – the receiver

The middle ear – the amplifier

The inner ear – the transmitter


Three Regions of the Ear

Figure 9.12 (1 of 2)

Outer

ear

(receiver)

Middle

ear

(amplifier)

Inner

ear

(transmitter)


The Outer Ear

Consists of the:

Pinna – gathers the sound, acts like a

funnel

External auditory canal – brings the sound

from pinna to the tympanic membrane


Middle Ear

Consists of the:

The tympanic membrane separates the outer

ear from the middle ear, vibrates when sound

waves hit it.

Three auditory bones – amplify the vibration

Malleus

Incus

Stapes

Auditory tube (eustachian tube) – equalizes

pressure between outer and middle ear


Middle Ear

The tympanic membrane vibrates when

sound waves hit it and transmits the

vibration to the malleus

The vibrations are amplified by the three

bones and transmitted to the oval window


Parts of the Inner Ear

Oval window – transmits sound from the stapes

to the fluid in the cochlea

Round window – relieves pressure

Cochlea – contains the receptor cells that

transform the signal from vibration to an

electrochemical signal to the neurons.

Vestibular apparatus – monitors position of the

head


Hearing Depends on the Ear


The pinna gathers sound and funnels it into the external auditory canal to the tympanic membrane (eardrum).

The eardrum vibrates synchronously with sound waves, causing the bones of the middle ear to move.

The three bones of the middle ear amplify the pressure waves and convey the vibrations of the eardrum to the inner ear.

The cochlea converts pressure waves to neural messages that are sent to the brain for interpretation as sound.

Malleus(hammer)

Incus(anvil)

Stapes(stirrup)

Semicircular canals

Vestibular apparatus:

Auditory nerve

Cochlea

Oval window

Eardrum(tympanic membrane)

Round window

Auditory tube(Eustachiantube)

Outer ear(receiver)

Middle ear(amplifier)

Inner ear(transmitter)

External auditory canal

Vestibule


Cochlea

It is in the cochlea where vibrations are

transformed into electrical signals that can be

sent by neurons

When the fluid in the cochlea moves, it moves

small “hair cells” against a membrane. This

allows ion channels to open

This leads to the release of neurotransmitters,

which trigger the neuron to send the message




Hair cell

Tectorial

membrane


In the ear, the fluid filled coiled membrane that is responsible

transforming the vibrations into electrical signals. This structure is:

1. Tymphanic

membrane

2. Staples

3. Cochlea

4. Incus


The tympanic membrane transmits the vibration to the ___.

Stapes

Malleus

Incus

Oval window


The Vestibular Apparatus

Balance depends on the vestibular apparatus

of the inner ear

The vestibular apparatus is a fluid-filled maze

of chambers and canals within the inner ear


The Vestibular Apparatus - Dynamic equilibrium

Fluid filled cupulas at base of the semicircular

canals have hair cells that are stimulated when

head moves. Hair cells send message to the

brain.


The Vestibular Apparatus - Static equilibrium

Otoliths are small chalk like granules

When head is tilted the otoliths move and

stimulate hair cells that send message to the

brain


Balance Depends on the Vestibular

Apparatus

Figure 9.16a (1 of 2)


Balance Depends on the Vestibular

Apparatus

Figure 9.16a (2 of 2)



Figure 9.16b (1 of 2)



Figure 9.16b (2 of 2)


Smell - olfaction

Sensory nerves for smell go directly to the cerebral cortex and to the amygdala and the hypothalamus.

They do not pass through the thalamus


Smell - olfaction

Odor molecules bind to the receptors in the cilia of olfactory receptor cells

The receptor cells send the message to the neurons in the olfactory bulb which carry the message to the brain.


Figure 9.17 Sense of Smell


Taste

Taste and smell is very connected.

The tongue has taste buds on them

The taste buds have taste cells (receptor

cells) in them


Taste

Food molecules bind to taste cells and

stimulate them. The taste cells send the

messages to the sensory neurons which

send the message to the brain.


Smell and Taste

Figure 9.18


Read Chapter 6

What is the function of sensory receptor

cells?

What is an example of sensory adaptation?

What are the types of senses of touch?

What are the types of sensory receptors in

skin, what type of touch do they detect, be

able to describe them?

Important Concepts


What are all of the layers and structures

(including the fluids) of the eye and what are

their functions?

What is the blind spot?

How does the signal travel from the

photoreceptors to the brain, what part of the

brain receives the signal? Be able to describe

in detail this process, including the cells that

transmit the messages.

Important Concepts


What are all the parts of the ear, are they part of the inner, middle or outer ear, and what is their functions? What is the path of sound waves and vibrations through the ear

How does the ear detect head movement and position?

How do we detect odor? What part of the brain receives the signal? Where are olfactory receptors found?

How do we detect tastes? What structures are responsible for taste?

Important Concepts


Definitions

stimuli (stimulus), sensory adaptation, dilates,

constrict, bipolar cells, ganglion cells,

photoreceptors, transmits, amplifies, otoliths,

cupula, taste buds,

nervous system sensory systems - napa valley college · middle ear consists of the: the tympanic...

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