Nervous System and Senses - PowerPoint Presentation

Slide1

Nervous System and Senses

Chapters 27

“Our conscious model of reality is low-dimensional projection of the inconceivably richer physical reality surrounding and sustaining us. Our sensory organs are

limited.They

evolved for reasons of survival, not for depicting the enormous wealth and richness of reality in all its unfathomable depth”

-Thomas

MetzingerSlide2

The Nervous System

Central nervous system (CNS)

: portion of nervous system consisting of

_______________________

Integration of signalsPeripheral nervous system (PNS): the nervous system outside of the brain and spinal cord, which includes the sensory organsEyesSkinEarsMouthSlide3

The Nervous System

Afferent division

: collection of nerves that

_________________

the brain or spinal cordEfferent division: collection of nerves that _________________ the brain or spinal cord to other parts of the PNS. Slide4

Types of Neurons

Sensory or afferent neuron

: nerve cell that receives signals from

__________________

inside and outside of the body then sends information to CNSInterneuron: nerve cells that interconnect other neuronsMotor or efferent neuron: nerve cells that transmit signals from the CNS to

________ _________________Slide5

Somatic nervous system

: portion of PNS’s efferent division that provides

________

control of skeletal muscles.Autonomic nervous system: part of the PNS’s efferent division that provided ______________________ of smooth muscle, cardiac muscle, and glandsThe Nervous SystemSlide6

Autonomic Nervous System

Parasympathetic division

: controls internal organs during

_____________ conditions

“rest and digest”Sympathetic division: controls internal organs during periods of ________ “flight or fight”Slide7

The Neuron

Dendrites

: extensions of neuron that receives signals and relays the signal towards nerve cell body

Axon

: extension of the neuron that _____________ to other neuronsCell body: area of the neuron containing organelles and nucleusSynaptic terminals

: transmit signal to adjacent nerve cells across the synapse Slide8

The Neuron

____________

insulate the axon of the neuron.

Prevents action potential from weakening as it move through axonOnly found in vertebratesAction potential: a temporary reversal of cell membrane potential that results in a conducted nerve impulse down the axon.Slide9

Anatomy of a Nerve

Nerve

: bundle of nerve cell

______

of PNS nerve cells that transmit signals to and from the CNSSlide10

Reflexes

Reflex

: automatic response independent of integration from the

________

Sensory neuron  Spinal cord interneuron or motor neuron  Automatic muscle movementSlide11

Membrane Potential

Membrane potential

:

______

difference between the inside and outside of the plasma membrane of a neuron Resting potential: membrane potential when not sending a signalControlled by ion channels and sodium-potassium pumpsDifferent

concentration gradients for Na

+

and K

+

inside and outside of cell

Net

______________

inside neuronSlide12

1.Unbound protein

2. Sodium binding. Phosphorylation of pump by ATP

3. Shape change

4. Sodium release

5.Unbound protein

6. Potassium binding

7. Phosphate release. Shape change

8. Potassium release

Sodium Potassium PumpSlide13

Transmitting a Signal

Gated ion channels

: ion channels that open or close in response to stimuli

Sodium (Na

+) and Potassium (K+) channels______________: positive-going change in membrane potential, which decreases the negative charge inside the nerve cellOpening of Na+ channels

Action potential

: a temporary reversal of cell membrane potential that results in a conducted nerve impulse down the axon.Slide14

Propagation of the Action Potential

Stimulus causes some voltage-gated sodium channels to open

Sodium ions (Na

+

) rush into the axon causing depolarization in the neuron and initiating an action potential

Depolarization moves down the axon causing more voltage-gated sodium channels to open

Another action potential occurs further down the axon resulting in the transmission of the signal through the neuron

Voltage-gated ion channels

become

temporarily inactive causing the

______________________

of the signal

Refractory period

Sodium ions (Na+) move into the axon

Positive charge inside the axon spreads

Positive charge causes more sodium channels to openSlide15

Transmitting a Signal

After depolarization occurs potassium channels open causing potassium ions to move out of the axon.

Removal of potassium ions cause the membrane potential to return to

resting potential.

Sodium-potassium pumps regulate the concentration of sodium and potassium ions in the axon to maintain resting potentialSlide16

Transmitting a Signal

Voltage-gated sodium channels are only located in the

_____________

(

gaps in myelin sheath)Fewer ion channels opening and closing means faster signalSlide17

_________

: area where sending neuron, receiving nerve cell and space between the two all come together

Synaptic cleft

: the gap between adjacent nerve cells within the synapse

__________________: A chemical, secreted into the synaptic cleft, that affects another neuron or effector by binding with receptors on it.

Passing the Signal AlongSlide18

Action potential depolarizes presynaptic membrane

Depolarization triggers voltage-gated Ca

2

+ channels to open

Ca2+ channels cause synaptic vesicles

to

fuse with presynaptic membrane, releasing neurotransmitter into synaptic cleft

Neurotransmitters bind

to

ligand-gated

ion channels on postsynaptic membrane which sets off new action potential

Passing the Signal Along

NeurotransmitterSlide19

Major Neurotransmitters

Neurotransmitter

Function

Problems Caused by Imbalance

Serotonin

Affects mood,

hunger, sleep, arousal

Oversupply linked to depression

______________

Influences movement, learning, attention,

and emotion

Oversupply linked to schizophrenia

Undersupply

linked to tremors and decreased mobility (Parkinson’s and ADHD)

Acetylcholine (Ach)

Enables muscle action,

learning, and memory

Degeneration of Ach-producing

neurons cause progression of Alzheimer’s disease

Norepinephrine

Helps control alertness and arousal

Undersupply can depress

mood and cause attention problems

GABA (gamma-

aminobutyric

acid)

Inhibitor neurotransmitter

Undersupply linked to seizures, tremors, and insomnia

Glutamate

Excitatory neurotransmitter,

memory

Oversupply

can overstimulate the brain producing migraines or seizuresSlide20

Check Your Understanding

True or False: The autonomic nervous system regulates

involuntary

functions

such as digestion and breathing.True or False: The parasympathetic division is involved in the flight or fight responseTrue or False: The myelin sheath slows down the action potentialSlide21

Check Your Understanding

Which of the following parts of the neuron receives signals from neighboring neurons?

a. Axon

b. Dendrites

c. Synapse d. Cell bodySlide22

Check Your Understanding

The chemicals released into the synaptic cleft that initiate the transmission of a signal between neurons are known as ________________.

a. Sodium ions

b. Potassium ions

c. Neurotransmitters d. Calcium ions e. ReflexesSlide23

_______________________

:

receptors that responds to pressure or distortion

Touch, hearingThermoreceptors: receptors that respond to changes in temperatureTouch, pit vipers, spicy food (capsaicin receptor), menthol Chemoreceptors: receptors that respond to different chemical stimuli in the environmentTaste, smell, solute concentration (osmoreceptors), glucose, oxygen, carbon dioxide

Photoreceptors:

receptors that respond to different wavelengths of light

_________________

Electromagnetic Receptors:

receptors that respond to electric or magnetic signals

Ampullae

of

Lorenzini

, platypus bill, elephant fish, magnetite

Sensory ReceptorsSlide24

Sending a Signal

Tonic receptors:

receptors that actively send the signal as long as the stimulus is present

Ex. Photoreceptors, ear mechanoreceptors

_________ receptors: receptors that begin to ignore stimulus after a period of continued activation. Sensory adaptation. Ex. Olfactory sense, touchSlide25

Touch

Touch receptors in the skin

Ex: Pacinian corpuscle receptorSlide26

Chemoreceptors: Olfaction (Smell)Slide27

Chemoreceptors: TasteSlide28

Mechanoreceptors: Hearing

Sound waveSlide29
Slide30

Hearing

High frequency waves are detected at beginning of cochlea

Low

frequency waves towards the end of cochlea

Human range = 20 – 20,000 HzDog range = 40 – 60,000 HzWhales sensitive to lower and bats to higher frequenciesSlide31

Mechanoreceptors: BalanceSlide32

Anatomy of the Human Eye

_________

:

allows light to enter

eye, changes diameter based on light conditionsLens: biconvex structure that refracts light passing into the eye

Iris

: pigmented smooth

muscle controls pupil diameter

Ciliary body

: controls lens shape

With near objects lens bulges, far objects it is thin

Retina

: inner layer of eye tissue containing

_________________Slide33

Photoreceptors: Vision

Rods

: photoreceptors that function in

__________________

(night vision)

Provide only black-and-white vision

Cones

: photoreceptors responsible for

_______________

Three types of cones with different color sensitivitiesSlide34

Focusing

Normal vision

: light rays converge on retina

Farsighted vision

: light rays converge ________ retinaNearsighted vision: light rays converge __________ of the retinaSlide35

Check Your Understanding

True or False: Phasic receptors will actively send a signal as long as the stimulus is present.

True or False: Light rays converge in front of the retina in near-sighted people

True or False: Rods

are responsible for color visionSlide36

Check Your Understanding

Which of the following controls the amount of light that enters the eye?

a. Lens

b. Ciliary body

c. Retina d. Iris e. Pupil Slide37

Check Your Understanding

What type of receptors are used in human touch?

a. Mechanoreceptors

b. Chemoreceptors

c. Photoreceptors d. Thermoreceptors e. More than one of the aboveSlide38

Check Your Understanding

Describe how an action potential is transmitted through the axon.