I. Neuron Structure and Function

II. Relationship between Stimuli Input

III. Nervous System Organization

IV. Brains

V. Preparation for next lecture

Lecture 14 – Ch. 48 & 49: Nervous Systems

Specialized “excitable” cells: receive input, integrate, send output

Neurons

synapse

dendrite

synapticterminal

1 Synaptic terminals:Bring signals fromother neurons.

2 Dendrites:Receive signalsfrom other neurons.

3 Cell body:Integrates signals;Coordinates.

4 Action potentialstarts here.

5 Axon: Conductsthe action potential.

6 Synaptic terminals:Transmit signals toother neurons.

7 Dendrites(of other neurons).

4

What parts of neurons are OUTSIDE the CNS?

1. All sensory, motor, and interneurons neurons

2. Sensory neuron dendrites & cell bodies AND motor neuron axons

3. Interneurons only

4. Motor neuron dendrites and interneuron axons

Neurons are electrical:• At rest, neurons maintain an electrical difference across their membrane

• (-) inside cell; (+) outside cell

Neurons

• charge = about -70 mV

Na+ pumped out, K+ pumped in, but K+ can leak out

gap

dendrite ofpostsynapticneuron

neurotransmitter

synapticvesicle

synapticterminal

Neurotransmittersignals next neuron.

Signal reaches end of axon.

Synaptic vesicles release neurotransmitter.

Receptor bindsneurotransmitter.

Neurons

Synapse: Region connecting two neurons or neuron and muscle

Neurotransmitter may excite or inhibit the next neuron

Neurons Transmit Signals via Action Potentials:

Action Potential (AP): The electrical signal passed along the length of a neuron

• During action potential, Na+ channels open, flows in

(extracellular fluid)

Na+

(axon)action potential

(+) inside cell; (-) outside cell

(extracellular fluid)

Na+

(axon)action potential

K+

• Neuron membrane polarized = charge difference

• Triggers K+ channels to open, flows out

• Charge difference lost = depolarized

Action Potentials

• Repolarized

Action Potentials

Na+ channels openK+ channels open

Before K+ channels close, greater charge difference = hyperpolarized

Action Potentials

Action potentials are propagated down the length of the neuron – after the AP, neuron resets itself (Na+ out, K+ in)

Na+ and K+ channels are voltage gated – as first Na+ channels open, more triggered to open (i.e. positive feedback)

Action potentials can be measured electrically:

Action Potentials

IPSP

time(milliseconds)

pot

en

tial

(mill

ivol

ts)

restingpotential

threshold

EPSP

• Stimulation from a neighbor neuron excites the cell (brief increase in voltage = EPSP)

• Inhibition from another neuron causes a brief decrease in voltage (IPSP)

dendrite ofPost-synapticneuron

neurotransmitter

synapticvesicle

Pre-synapticterminal

Action Potentials

IPSP

time(milliseconds)

pot

en

tial

(mill

ivol

ts)

EPSP

EPSP = excitatory post-synaptic potential

IPSP = inhibitory post-synaptic potential

(+) Neurotransmitter

(-) Neurotransmitter

Individual EPSP & IPSP weak

Action Potentials

• Sum of all excitatory & inhibitory ‘blips’ = summation

Action Potentials

action potential

pot

en

tial

(mill

ivol

ts)

Less (-)

time(milliseconds)

restingpotential

threshold

More (-)

• If threshold voltage is reached, an action potential occurs

Information Coding in the Nervous System:

1) Determine stimulus type (e.g. light / sound / touch)

• All neurons use same basic signal

• Wiring pattern in brain distinguishes stimuli

2) Signal intensity of stimulus

• All signals similar in size (all-or-none response)

• Intensity coded by:

1) Frequency of action potentials

2) # of neurons responding

Stimuli Input

Information Coding in the Nervous System:

Stimuli Input

fires slowly

silent

1

2

fires moderately

silent

1

2

fires rapidly

fires slowly

1

2

Information Coding in the Nervous System:

3) Integrate/coordinate signals

4) Determine Output

Stimuli Input

Neural Pathways Direct Behavior:

1) Receptor: Detects stimulus

2) Sensory neuron: Sends stimulus message

3) Interneuron(s): Integrates stimuli

4) Motor neuron: Activates effector

5) Effectors: Performs function (muscle / gland)

Spinal Cord:

Myelin = Insulation around axons

• Increases AP conduction rate

Nervous System Organization

Spinal Cord:

Nervous System Organization

What part of the spinal cord contains motorneuron cell bodies?

1. White matter

2. Dorsal root ganglia

3. Gray matter

4. Ventral roots

PN

SC

NS

Brain and Spinal Cord

Sympathetic nervoussystem

"fight or flight"

Parasympathetic nervoussystem

"rest and repose"

Somatic nervoussystem

(voluntary)

Sensory neuronsregistering external

stimuli

Autonomic nervoussystem

(involuntary)

Sensory Pathways Motor Pathways

Sensory neuronsregistering external

stimuli

Nervous System Organization

Nervous System Organization

If you are surprised by a “predator”, what happens in your nervous system?

1. Sympathetic nervous system increases heart rate

2. Somatic nervous system increases heart rate

3. Autonomic nervous system increases saliva

4. Parasympathetic NS increases saliva secretion

The Brain:

1) Hindbrain:

Automatic BehaviorsA) Medulla: Controls

breathing, heart rate,

blood pressure

B) Pons: Controls

wake/sleep transitions;

sleep stages

C) Cerebellum:

Coordinates movement

spinal cord

meningesskull

cerebellumponsmedulla

hindbrain

Human Brain

The Brain:

2) Midbrain: Relay /

“Screening” Center A) Reticular Formation:

Controls arousal of brain

• Filters sensory input from body

B) Visual / Auditory Reflex Centers

pituitarygland pineal

gland

midbrain- Reticular Formation

Human Brain

The Brain:

3) Forebrain (Cerebrum):

“Seat of Consciousness”

A) Cerebral Cortex

• Two hemispheres (Connection =

Corpus Callosum)

• Left hemisphere controls right side

of body (and vise versa)

cerebralcortex

corpuscallosum

Human Brain

The Brain:

3) Forebrain (Cerebrum)A) Cerebral Cortex

Four regions:

1) Frontal: Primary motor area; complex reasoning

2) Parietal: Primary sensory area

3) Temporal: Primary auditory and olfactory areas

4) Occipital: Primary visual area

Human Brain

OccipitalLobe

ParietalLobe

FrontalLobe

TemporalLobe

OccipitalLobe

primarysensory area

sensoryassociationarea

sensoryassociationarea

primaryvisualarea

primaryvisualarea

visualassociationarea

visualassociationarea

auditory associationarea: languagecomprehension

auditory associationarea: languagecomprehension

memorymemory

speechmotor areaspeechmotor area

higherintellectualfunctions

higherintellectualfunctions

primaryauditoryarea

primaryauditoryarea

premotorareapremotorarea

primarymotor areaprimarymotor area

legleg

trunktrunk

armarm

handhand

faceface

tonguetongue

ParietalLobe

FrontalLobe

TemporalLobe

Human Brain

Motor and Sensory

areas

Human Brain

Which is a correct match between brain region and function:

1. Parietal lobe : visual processing

2. Reticular formation : filters sensory input

3. Cerebellum : controls sleep stages

4. Cerebrum : dictates breathing rate

Cortical Regions Involved in Different Tasks:

Human Brain

Seeing Words

max0

Reading Words Generating Verbs

Hearing Words

The Brain:

hypothalamusthalamus

B) Limbic System

• Produce emotions; form memories

C) Thalamus

• Relays information from body to limbic system / cerebral cortex

3) Forebrain (Cerebrum)

Human Brain

The Brain:

B) Limbic System

• Hypothalamus:

Homeostatic control center

• Amygdala: Produces

sensations of pleasure,

fear, or sexual arousal

• Hippocampus:

Formation of long-term memory

C) Thalamus

• Relays to limbic system /

cerebral cortex

Human Brain

hypothalamus

corpus callosum

limbic regionof cortex

cerebral cortex

amygdala

hippocampus

thalamus

Damage to the hippocampus could result in:

1. Failure to understand speech

2. Reduced fear response

3. Lack of homeostatic control

4. Loss of long-term memory formation

Things To Do After Lecture 14…Reading and Preparation:

1. Re-read today’s lecture, highlight all vocabulary you do not understand, and look up terms.

2. Self-Quiz: Ch. 48 #1-3, 5; Ch. 49 #1, 2, 4, 5, 6 (correct answers in back of book)

3. Read chapters 48 & 49, focus on material covered in lecture (terms, concepts, and figures!)

4. Skim next lecture.

“HOMEWORK” (NOT COLLECTED – but things to think about for studying):

1. Explain the difference between the somatic and autonomic nervous systems.

2. Diagram a basic neuron – for sensory, motor, and interneurons explain the location of each region with respect to peripheral or central nervous system.

3. Compare and contrast the embryonic vertebrate brain with that of adults.

4. List the regions of the brain (with functions) from the “outside” of the brain, inward.