The Nervous System

Facts:Facts:

Responsible for all behavior Every thought, action, and behavior controlled here Works together with the endocrine system to achieve

homeostasis Cells communicate by electrical signals

Responsible for all behavior Every thought, action, and behavior controlled here Works together with the endocrine system to achieve

homeostasis Cells communicate by electrical signals

Three Main Functions:Three Main Functions:

Sensory input Integration Motor output

Sensory input Integration Motor output

Sensory InputSensory Input

Our bodies have millions of sensory receptors

They detect changes Changes are called “stimulus” This is where all stimuli is collected Called the “afferent pathway”

Our bodies have millions of sensory receptors

They detect changes Changes are called “stimulus” This is where all stimuli is collected Called the “afferent pathway”

IntegrationIntegration

Your brain makes decisions about what to do with the stimulus

It processes the info gathered It establishes a set point

Your brain makes decisions about what to do with the stimulus

It processes the info gathered It establishes a set point

Motor OutputMotor Output

Causes a response to the stimulus Activates effector organs Sends signal down “efferent pathway”

Causes a response to the stimulus Activates effector organs Sends signal down “efferent pathway”

Nervous System DivisionsNervous System Divisions

Central Nervous System (CNS) CNS includes brain & spinal cord Peripheral Nervous System (PNS)’ PNS broken down into afferent & efferent divisions Sensory division = Afferent division Motor division = efferent division Both CNS and PNS work together You can’t have one without the other

Central Nervous System (CNS) CNS includes brain & spinal cord Peripheral Nervous System (PNS)’ PNS broken down into afferent & efferent divisions Sensory division = Afferent division Motor division = efferent division Both CNS and PNS work together You can’t have one without the other

Nervous System HistologyNervous System Histology

Nervous tissue is highly cellular Less than 20% of cns is extra-cellular space Cells densely packed together Tissue is made up of two principal types of cells (nerve

cells and supporting cells)

Nervous tissue is highly cellular Less than 20% of cns is extra-cellular space Cells densely packed together Tissue is made up of two principal types of cells (nerve

cells and supporting cells)

Supporting Cells in CNSSupporting Cells in CNS

Glial cells (neuroglia) Glial cells have branching processes and central cell

body, like neurons Smaller than neurons Outnumber neurons in CNS 9 to 1 They make up half the mass of the brain

Glial cells (neuroglia) Glial cells have branching processes and central cell

body, like neurons Smaller than neurons Outnumber neurons in CNS 9 to 1 They make up half the mass of the brain

Common Glial Cells in CNSCommon Glial Cells in CNS

Astrocytes Control chemical enironment around neurons “mop up” leaked potassium ions & recycle them Recapture/recycle neurotransmitters

Microglia Monitor health of neurons Protect against microorganisms Can turn into macrophages which destroy foreign intruders Fact: immune system cells are denied access to CNS

Oligodendrocytes Make up myelin sheaths

Astrocytes Control chemical enironment around neurons “mop up” leaked potassium ions & recycle them Recapture/recycle neurotransmitters

Microglia Monitor health of neurons Protect against microorganisms Can turn into macrophages which destroy foreign intruders Fact: immune system cells are denied access to CNS

Oligodendrocytes Make up myelin sheaths

Supporting Cells in PNSSupporting Cells in PNS

Satellite Cells Surround neuron cell bodies Play a role in controlling the chemical environment of

the neurons

Schwann Cells Surrounds & forms myelin sheaths around larger nerve

fibers in PNS Functionally similar to oligodendrocytes

Satellite Cells Surround neuron cell bodies Play a role in controlling the chemical environment of

the neurons

Schwann Cells Surrounds & forms myelin sheaths around larger nerve

fibers in PNS Functionally similar to oligodendrocytes

NeuronsNeurons

Structural units of the nervous system Highly specialized cells Have extreme longevity with good nutrition (100 years

plus) Neurons are amitotic - no ability for mitosis. Cannot be

replaced if destroyed Have a high metabolic rate - need high amounts of

oxygen & glucose. Cannot survive more than a few minutes without

oxygen

Structural units of the nervous system Highly specialized cells Have extreme longevity with good nutrition (100 years

plus) Neurons are amitotic - no ability for mitosis. Cannot be

replaced if destroyed Have a high metabolic rate - need high amounts of

oxygen & glucose. Cannot survive more than a few minutes without

oxygen

Neuron AnatomyNeuron Anatomy

The most common neuron is multipolar They are made up of four basic parts: Dendrites - receive signals from previous neurons Cell body - controls/sustains neuron Axon - allows nerve signals to travel along neuron Terminal bodies - release neurotransmitters at tips Myelin sheaths cover axon in many neurons. Protects,

insulates, and speeds up conduction. Myelinated neurons include “nodes of Ranvier” Function … speeds up signal transmission Myelinated neurons faster conductors than

unmyelinated

The most common neuron is multipolar They are made up of four basic parts: Dendrites - receive signals from previous neurons Cell body - controls/sustains neuron Axon - allows nerve signals to travel along neuron Terminal bodies - release neurotransmitters at tips Myelin sheaths cover axon in many neurons. Protects,

insulates, and speeds up conduction. Myelinated neurons include “nodes of Ranvier” Function … speeds up signal transmission Myelinated neurons faster conductors than

unmyelinated

Multipolar NeuronMultipolar Neuron

Drugs & NeurotransmittersDrugs & Neurotransmitters

Inside of hypothalamus is our “pleasure center”

Motivates much of human behavior Responsible for anything that gives us

pleasure/joy Our ability to feel good involves

neurotransmitters Drug use re-programs how these

neurotransmitters work

Inside of hypothalamus is our “pleasure center”

Motivates much of human behavior Responsible for anything that gives us

pleasure/joy Our ability to feel good involves

neurotransmitters Drug use re-programs how these

neurotransmitters work

Speed (Methamphetamine)Speed (Methamphetamine)

Artificially stimulates brain to provide pleasure flush

When outside chemicals are introduced, brain produces less neurotransmitters

“why bother?!?!?”

Artificially stimulates brain to provide pleasure flush

When outside chemicals are introduced, brain produces less neurotransmitters

“why bother?!?!?”

CocaineCocaine

Comes in snorted form (white powder) Stimulates pleasure center then squeezes it

dry Hooks to dopamine transporter protein So, it blocks reabsorption of dopamine …..the neurotransmitter remains in synapse

and stimulates receptor cells over and over again

Increased heart rate, blood pressure, sexual appetite

Comes in snorted form (white powder) Stimulates pleasure center then squeezes it

dry Hooks to dopamine transporter protein So, it blocks reabsorption of dopamine …..the neurotransmitter remains in synapse

and stimulates receptor cells over and over again

Increased heart rate, blood pressure, sexual appetite

As dopamine is blocked, it accumulates in synapse It’s washed away Brain dopamine supply becomes inadequate to maintain

normal moods The sending cells cannot make dopamine fast enough to

make up for the loss and pleasure circuits go dry Cannot experience pleasure without the drug Catch-22: cocaine needed to experience pleasure, but

more use = more depletion of neurotransmitter supply Weight loss, trouble sleeping, mood swings, death Incredibly difficult to treat

As dopamine is blocked, it accumulates in synapse It’s washed away Brain dopamine supply becomes inadequate to maintain

normal moods The sending cells cannot make dopamine fast enough to

make up for the loss and pleasure circuits go dry Cannot experience pleasure without the drug Catch-22: cocaine needed to experience pleasure, but

more use = more depletion of neurotransmitter supply Weight loss, trouble sleeping, mood swings, death Incredibly difficult to treat

CrackCrack

Cheaper than cocaine More potent Smokable form of cocaine Produces higher high and a deeper

crash!! Intensely addictive

Cheaper than cocaine More potent Smokable form of cocaine Produces higher high and a deeper

crash!! Intensely addictive

HeroinHeroin

Is a depressant Far more expensive than cocaine Demands higher doses to achieve the same

effect When addicted and going without, body goes

into incapacitated nausea and convulsions With an overdose, lungs fill with fluid and user

drowns.

Is a depressant Far more expensive than cocaine Demands higher doses to achieve the same

effect When addicted and going without, body goes

into incapacitated nausea and convulsions With an overdose, lungs fill with fluid and user

drowns.