Nervous System

Organization of Peripheral Nervous System

(PNS)

Sensingexternal

environment

PeripheralNervous System

Sensory

Sensinginternal

environment

Motor

AutonomicnervousSystem

(involuntary)

SomaticnervousSystem

(voluntary)

SympatheticSpeeding up

Parasympatheticslowing down

AutonomicnervousSystem

(involuntary)

ParasympatheticSlowing down

SympatheticSpeeding up

Fight or FlightRest and Digest

This is a continuation of the previous flow chart

Organization of Central Nervous System

(CNS)

ForebrainCerebrumThalamusHypothalamus

Midbrain

Pituitarygland

Hindbrain

PonsMedulla oblongataCerebellum Spinal

cord

Cerebralcortex

LeftHem.

RightHem.

CorpusCallosum

Frontal Lobe Parietal Lobe

Temporal Lobe Occipital Lobe

•Frontal Association•Speech•Motor Cortex

•Taste•Speech•Reading

•Smell•Auditory Association•Hearing

•Vision•Visual AssociationOn your notes you

need to have the left picture and labels

Nervous Tissue• Glial Cells

– 90% of CNS– Structural framework– Fatty Myelin sheath– Phagocytosis– Cerebrospinal fluid

circulation

Structure of Single Neuron

Neurons I

• Cell Body– Nucleus– Cytoplasm– Other common

organelles– NO mitotic spindles!(what problems does this

cause?)

• Dendrites– Highly branched– Receive impulses

Neurons II

• Axon– Always only 1– Conducts impulse AWAY

from cell body– Can extend as much as 1

meter– Encased by Schwann cells

Myelin sheath– (In CNS, Oligodendrocytes

may provide sheath)– Nodes of Ranvier

3 types of Neurons

Sensory Neurons – neurons that carry incoming information from the sense to the CNS

Interneurons – CNS neurons that internally communicate and intervene betweenthe sensory inputs and motor outputs

Motor Neurons – Carry outgoing information from the CNS to muscle and glands

How do cells detect and respond to

changes in their internal and external

environment to successfully survive

and maintain homeostasis?

1) Detection of signals from the outside environment or detection of deviation (change) from homeostasis from the internal environment.

2) Integration of multiple signals from outside and inside to produce appropriate response.

BRAIN

3) Response to counteract stimulus being detected.

Draw your own picture to represent RESPONSE

1) Detection of signals from outside environment or detection of deviation (change) from homeostasis from internal environment.

2) Integration of multiple signals from outside and inside to produce appropriate response.

3) Response to counteract stimulus being detected

System builds a Reflex Arc

Sensor Receptor (Detection)

Sensory Input

IntegrationEffector (Response)

Motor Output

Peripheral NervousSystem (PNS)

Central Nervous System(CNS)

Neuron SignalsACTION POTENTIAL

• When an impulse reaches the Axon Terminal, dozen of vesicles fuse with the cell membrane and discharge the Neurotransmitter into the Synaptic Cleft (GAP).

• The molecules of the neurotransmitter diffuse across the gap and attach themselves to SPECIAL RECEPTORS on the membrane of the neuron receiving the impulse.

• When the neurotransmitter becomes attached to the cell membrane of the adjacent nerve cell, it changes the permeability of that membrane.

• As a result, Na+ ions diffuse through the membrane into the cell.

• If enough neurotransmitter is released by the axon terminal, so many Na+ ions diffuse into the neuron that the neuron becomes DEPOLARIZED.

• DEPOLARIZED = Inside the membrane becomes more positive than outside.

• This causes a THRESHOLD to be REACHED and an impulse (ACTION POTENTIAL) begins in the second cell.

• After the neurotransmitter relays it message it is rapidly REMOVED or DESTROYED, thus halting its effect.

• The molecules of the neurotransmitter may be broken down by ENZYMES, taken up again by the axon terminal and recycled, or they may simply diffuse away.

• NERVE GAS prevents enzymes from breaking down neurotransmitters, as a result muscles in the respiratory and nervous system becomes paralyzed.

• The point of contact at which impulses are passed from one cell to another are known as THE SYNAPTIC CLEFT OR SYNAPSE.

• Neurons that transmit impulses to other neurons DO NOT actually touch one another.  The Small Gap or Space between the axon of one neuron and the dendrites of the next neuron is called the Synapse. 

• One importance of the presence of Synapses is that they ensures one-way transmission of impulses in a living person. 

• The Axon Terminals at a Synapse contain tiny vesicles, or sacs. These are known as NEUROTRANSMITTERS.

NEUROTRANSMITTER is a chemical substance that is used by one neuron to signal another.  The impulse is changed from an Electrical Impulse to a Chemical Impulse (Electrochemical Impulses).

Other facts…

• After the neurotransmitter relays it message it is rapidly REMOVED or DESTROYED, thus halting its effect.

• Neurotransmitters may be broken down by ENZYMES, taken up again by the axon terminal and recycled, or they may simply diffuse away.

• NERVE GAS prevents enzymes from breaking down neurotransmitters, as a result muscles in the respiratory and nervous system becomes paralyzed.

Chemical Influences

• How might stimulants work? (Amphetamines, caffeine, nicotine)– Increase synaptic transmission increased

energy/mood, decreased appetite.• Increased irritability and anxiety

• How might depressants work? (Alcohol, anti-anxiety drugs, heroin)– Inhibition of impulses (blocking receptors of

NT• Can result in depression

Animations