The Nervous The Nervous SystemSystem

Chapter 3.1Chapter 3.1

CNS vs. PNSCNS vs. PNS CNS: Central Nervous SystemCNS: Central Nervous System

Brain and the spinal cordBrain and the spinal cord

PNS: Peripheral Nervous SystemPNS: Peripheral Nervous System Nerve cells that send messages Nerve cells that send messages

between central nervous system and between central nervous system and other parts of the bodyother parts of the body

NeuronsNeurons Nerve cells that run through our Nerve cells that run through our

entire body and communicate with entire body and communicate with each othereach other

Messages relate to certain eventsMessages relate to certain events Ex.: memories, learning a new skill, Ex.: memories, learning a new skill,

injuryinjury

In case of injury or In case of injury or disease, the brain disease, the brain can reorganize can reorganize itself by altering itself by altering connection connection between neuronsbetween neurons Ability to Ability to

reorganize neurons reorganize neurons in brain = in brain = neuroplasticityneuroplasticity

Parts of a neuron:Parts of a neuron: Cell body: produces energy to fuel Cell body: produces energy to fuel

neural activityneural activity

Dendrites: receive Dendrites: receive information from information from other neurons and other neurons and pass the message pass the message through the cell through the cell bodybody

Cell bodies have Cell bodies have many dendrites; one many dendrites; one axonaxon

Axons: transmit Axons: transmit messages away messages away from the cell from the cell bodybody Vary in length: Vary in length:

smaller than an inch smaller than an inch to a several feetto a several feet

Myelin: fatty sheath Myelin: fatty sheath that covers and that covers and protects the axonprotects the axon

Speeds Speeds transmission of transmission of messages sent messages sent from neuronsfrom neurons

Axon Terminals: Axon Terminals: fibers holding the fibers holding the axonsaxons

Communication between Communication between NeuronsNeurons

Flow of message:Flow of message:

Axon Terminals Axon Terminals DendritesDendrites

Messages move in Messages move in one directionone direction

Synapse: junction between the axon Synapse: junction between the axon terminal of one cell and the terminal of one cell and the dendrites of the nextdendrites of the next

Sensory Neurons: Sensory Neurons: information information received by senses received by senses to the CNSto the CNS

Motor Neurons: Motor Neurons: nerve cells that nerve cells that carry information carry information from the CNS to from the CNS to muscles and muscles and glandsglands

NeurotransmittersNeurotransmitters Neurotransmitters: chemicals that are Neurotransmitters: chemicals that are

stored in sacs in the axon terminals.stored in sacs in the axon terminals. Chemical message between two neuronsChemical message between two neurons Converted into an electrical impulse that travels Converted into an electrical impulse that travels

through the neuron, triggers another release of through the neuron, triggers another release of neurotransmitter to go the next neuron, etc.neurotransmitter to go the next neuron, etc.

Process takes a fraction of a secondProcess takes a fraction of a second

Numerous types of neurotransmitter Numerous types of neurotransmitter each serves a different purposeeach serves a different purpose Each has its own structure; fits into Each has its own structure; fits into

receptor site on the next neuronreceptor site on the next neuron Imbalance of neurotransmitter can lead Imbalance of neurotransmitter can lead

to certain diseases or mental disordersto certain diseases or mental disorders

Ex.: acetylcholine involved in memory; too Ex.: acetylcholine involved in memory; too little can impair the formation of new little can impair the formation of new memories (possibly tied to Alzheimer’s)memories (possibly tied to Alzheimer’s)

Ex.2: dopamine involved in motor behavior; Ex.2: dopamine involved in motor behavior; too little can cause trembling hands, too little can cause trembling hands, problems with balance, and uncoordinated problems with balance, and uncoordinated movements (Parkinson’s)movements (Parkinson’s)

Central Nervous SystemCentral Nervous System

Brain and spinal cordBrain and spinal cord

Spinal cord: column of nerves; Spinal cord: column of nerves; extends from brain down the backextends from brain down the back Protected by the spineProtected by the spine Transmits messages between brain and Transmits messages between brain and

the muscles and glandsthe muscles and glands

Spinal reflexes: automatic response to a trigger Spinal reflexes: automatic response to a trigger without input from the brainwithout input from the brain

Occurs when nerve impulses are received from the Occurs when nerve impulses are received from the body’s sensory organs (eyes, ears, etc.)body’s sensory organs (eyes, ears, etc.)

Message is passed along to the brain but the reflex is Message is passed along to the brain but the reflex is carried out without direct input from the braincarried out without direct input from the brain

Ex.: touching a hot stove; blinking; tapping the kneecap Ex.: touching a hot stove; blinking; tapping the kneecap

Peripheral Nervous Peripheral Nervous SystemSystem

Transmits messages Transmits messages between CNS and between CNS and everywhere else in everywhere else in your bodyyour body

Divided between Divided between the somatic nervous the somatic nervous system (SNS) and system (SNS) and the autonomic the autonomic nervous system nervous system (ANS)(ANS)

Somatic Nervous SystemSomatic Nervous System Transmits sensory messages to the CNSTransmits sensory messages to the CNS Carry messages from Carry messages from voluntaryvoluntary muscles muscles

and sense organsand sense organs

Activated by touch, pain, temperature Activated by touch, pain, temperature changes, and body positionchanges, and body position

Allows experiencing of heat/cold, Allows experiencing of heat/cold, pressure, painpressure, pain Ex.: Fuzzy Puppy—feeling warmth from Ex.: Fuzzy Puppy—feeling warmth from

sitting on your lap, soft fur, and pain if the sitting on your lap, soft fur, and pain if the puppy bites youpuppy bites you

Alerts brain which parts of the body Alerts brain which parts of the body moved; maintains balance and posturemoved; maintains balance and posture

Autonomic Autonomic Nervous SystemNervous System ““autonomic” = autonomic” =

occurring occurring involuntarilyinvoluntarily

Regulates body’s vital functions like Regulates body’s vital functions like heartbeat, breathing, digestion, blood heartbeat, breathing, digestion, blood pressure, etc.pressure, etc.

Regulates involuntary muscles and Regulates involuntary muscles and internal organsinternal organs

Two divisions:Two divisions: Sympathetic:Sympathetic:

Prepares body for Prepares body for action under stress; action under stress; “fight or flight”“fight or flight”

Parasympathetic:Parasympathetic: Restores body’s Restores body’s

reserves of energy reserves of energy after intense after intense activity; body activity; body returns to normal returns to normal

““rest and digest”rest and digest”

Example of the communication:Example of the communication: You see a tiger outside of its cage at the You see a tiger outside of its cage at the

zoo. zoo.

Sensory neurons relay message to the Sensory neurons relay message to the CNS. “I see a tiger outside of the cage! CNS. “I see a tiger outside of the cage! It’s almost like in nature!” It’s almost like in nature!”

Brain processes the situation. The tiger looks Brain processes the situation. The tiger looks pretty cool outside its cage. You’re in a zoo so pretty cool outside its cage. You’re in a zoo so there has to be an employee near by, but there has to be an employee near by, but you’re still a bit nervous—this is a new you’re still a bit nervous—this is a new situation. CNS tells you to watch the tiger and situation. CNS tells you to watch the tiger and look for the employee. look for the employee.

You see the employee. He’s laying on the You see the employee. He’s laying on the ground, mauled by the tiger. You panic. CNS ground, mauled by the tiger. You panic. CNS freezes. freezes.

PNS (autonomic PNS (autonomic nervous system) kicks nervous system) kicks your adrenal glands your adrenal glands into overdrive (fight or into overdrive (fight or flight) and your legs flight) and your legs begin to break into a begin to break into a run. OR your adrenal run. OR your adrenal glands go into glands go into overdrive, you tackle a overdrive, you tackle a scared zoo employee, scared zoo employee, take his/her take his/her tranquilizer gun and tranquilizer gun and stop the tiger.stop the tiger.

After successfully After successfully fleeing or fighting the fleeing or fighting the tiger, you feel a bit tiger, you feel a bit weak. Your adrenal weak. Your adrenal glands have slowed glands have slowed down. You feel a need down. You feel a need to sit down and eat. to sit down and eat. The gift shop is nearby; The gift shop is nearby; you walk in, get some you walk in, get some ice cream and sit on a ice cream and sit on a bench. Your body bench. Your body returns to normal returns to normal (parasympathetic (parasympathetic nervous system).nervous system).

You save the princess. You save the princess. Game over.Game over.

Until next tiger…Until next tiger…