Neural and Hormonal Systems

Module 3

History of Mind

In 1800, Franz Gall suggested that bumps

of the skull represented mental

abilities.

Phrenology

Bettm

an/ Corbis

Neural CommunicationWe are a biopsychosocial system.

Cellular Level(Interconnected

Neurons)

Organ Level(Brain)

System Level(InformationProcessing)

Individual Level(Human Being)

Group Level(Family)

Ethnic Level(Culture)

Community Level(Society)

Neural Communication

Neurobiologists and other investigators understand that humans and animals operate

similarly when processing information.

Neural Communication

The body’s information system is built from billions of interconnected cells called neurons.

Neuron

A nerve cell, or a neuron, consists of many different parts.

The cell body

– Round, centrally located structure

– Contains DNA– Controls protein

manufacturing – Directs metabolism– No role in neural

signaling

• Contains the cell’s Nucleus

Dendrites

• Information collectors• Receive inputs from

neighboring neurons• Inputs may number in

thousands• If threshold is reached

the AXON will generate an output

Dendritic Growth

• Mature neurons generally can’t divide

• But new dendrites can grow

• Provides room for more connections to other neurons

• New connections are basis for learning

Axon

• The cell’s output structure

• One axon per cell, 2 distinct parts– tubelike structure,

terminal branches at end that connect to dendrites of other cells

Myelin sheath

• Specialized Glial cells • Acts as an electrical

insulator • Not present on all

cells• When present

increases the speed of neural signals down the axon.

Myelin Sheath

How neurons communicate

• Neurons communicate by means of an electrical signal called the Action Potential

• Action Potentials are based on movements of ions between the outside and inside of the cell

• When an Action Potential occurs a molecular message is sent to neighboring neurons

Action PotentialA neural impulse. A

brief electrical charge that travels down an

axon and is generated by the movement of positively charged atoms in and out of

channels in the axon’s membrane.

Threshold

Threshold: Each neuron receives excitatory and inhibitory signals

from many neurons.

Action Potential Properties

All-or-None Response: A strong stimulus can trigger more neurons to fire, and to fire more often, but it does not affect the

action potentials strength or speed.

Intensity of an action potential remains the same throughout the length of the

axon.

Synapse Synapse [SIN-aps] a junction between the

axon tip of the sending neuron and the dendrite or cell body of the receiving

neuron.

Neurotransmitters

Neurotransmitters (chemicals)

released from the sending neuron travel across the synapse and bind to receptor sites on the receiving

neuron.

Reuptake

Neurotransmitters in the synapse are reabsorbed into the sending neurons through

the process of reuptake.

Chemical Messengers

• Neurotransmitters

• Hormones

• Neurohormones

Types of Neurotransmitters• Acetylcholine• Serotonin• Norepinephrine• Dopamine• Endorphins• GABA • Glutamate

Acetylcholine

• Found in neuromuscular junction

• Involved in muscle movements

Disruption of Ach Functioning• Curare - blocks ACh receptors

– paralysis results

• Nerve gases and Black Widow spider venom - too much ACh leads to severe muscle spasms and possible death

• Cigarettes - nicotine works on ACh receptors– can artificially stimulate skeletal muscles, leading to slight,

trembling movements

Alzheimer’s Disease• Deterioration of memory, reasoning,

and language skills

• Symptoms may be due to loss of ACh neurons

Serotonin

Serotonin pathways are involved with

mood regulation.

Dopamine

Important for movement, rewards & pleasure.

Involved with diseases such

as schizophrenia

and Parkinson’s disease.

Parkinson’s Disease

• Results from loss of dopamine-producing neurons

• Symptoms include– difficulty starting and stopping voluntary movements– tremors at rest– stooped posture– rigidity– poor balance

Parkinson’s Disease

• Treatments– L-dopa– transplants of fetal dopamine-producing

substantia nigra cells– adrenal gland transplants– electrical stimulation of the thalamus has

been used to stop tremors

Oliver Sacks: “Awakenings”

• Patients had suffered from encephalitis lethargica decades earlier

• Patients were in a frozen or semi-frozen state• Encephalitis lethargica causes the symptoms of

Parkinson’s disease

Sacks: Results

• Patients “awoke” from their frozen states

L-Dopa

Sacks administered the experimental drug L-Dopa

Sacks: Results & Legacy

• L-Dopa lost its effectiveness, and patients returned to their frozen state

• The experiment showed the relationship between encephalitis lethargica and dopamine and between encephalitis lethargica and Parkinson’s disease

• Showed how medicine can affect behavior

Norepinephrine

• Arousal• Sympathetic nervous system• “Fight or flight” response• Wakefulness, sleep• Learning• Mood regulation

Endorphins• Control pain and

pleasure• Released in response

to pain• Morphine and codeine

work on endorphin receptors Involved in healing effects of acupuncture

Gamma-Aminobutyric Acid (GABA)

• Main inhibitory neurotransmitter of the CNS when you sleep

• Benzodiazepines (which include tranquilizers such as Valium) and alcohol work on GABA receptor complexes

Glutamate

• Major excitatory neurotransmitter

• Too much glutamate (and too little GABA) associated with epileptic seizures

• Involved w/memory

Lock & Key Mechanism

Neurotransmitters bind to the receptors of the receiving neuron in a key-lock mechanism.

Agonists

Antagonists

The Nervous System

The Nervous System

Nervous System: Consists of all the nerve cells. It is the body’s speedy, electrochemical communication system.

Central Nervous System (CNS): the brain and spinal cord.

Peripheral Nervous System (PNS): the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body.

Nervous System

CentralNervousSystem(CNS)

PeripheralNervousSystem(PNS)

Kinds of Neurons

Sensory Neurons carry incoming

information from the sense receptors to the

CNS. Motor Neurons carry outgoing information

from the CNS to muscles and glands. Interneurons connect

the two neurons.

Central Nervous System

The Spinal Cord and Reflexes

Simple Reflex

The Nerves

Nerves consist of neural “cables” containing many axons. They are part of the peripheral

nervous system and connect muscles, glands, and sense organs to the central nervous

system.

Peripheral Nervous System

Somatic Nervous System: The division of the peripheral nervous system that controls the body’s skeletal muscles.

Autonomic Nervous System: Part of the PNS that controls the glands and other muscles.

Autonomic Nervous System (ANS)

Sympathetic Nervous System: Division of the ANS that arouses the body, mobilizing its energy in stressful situations.

Parasympathetic Nervous System: Division of the ANS that calms the body, conserving its energy.

Central Nervous SystemThe Brain and Neural Networks

Complex Neural Network

Interconnected neurons form networks in the brain.

The Endocrine System

The Endocrine System is the body’s “slow”

chemical communication

system. Communication is

carried out by hormones

synthesized by a set of glands.

Hormones vs. Neurotransmitters

• Distance traveled between release and target sites– hormones travel longer distances– neurotransmitters - travel across a synaptic

cleft (20 nm)

• Speed of communication– hormones - slower communication– neurotransmitters - rapid, specific action

Hormones

Hormones are chemicals synthesized by the endocrine glands that are secreted in the

bloodstream. Hormones affect the brain and many other tissues of the body.

For example, epinephrine (adrenaline) increases heart rate, blood pressure, blood sugar, and feelings of excitement during

emergency situations.

Pituitary Gland

Is called the “master gland.” The anterior pituitary lobe releases hormones that

regulate other glands. The posterior lobe regulates water and salt balance.

The effects of the pituitary are clearly shown here. Entertainer David Frost stands between the

world’s tallest and smallest man.

The tallest man in history was 8 feet 11 inches tall. He died at the age of 22, partly as a result of this defect. The shortest known person was 23 inches tall when she died at the age of 19. Today’s medicines can handle most of these problems if caught earlier enough, but these cases show what happen if the pituitary gland goes awry.

• Tallest man• http://www.youtube.com/watch?

v=zL_nklbytbY• Smallest man• http://www.youtube.com/watch?

v=UyJOOS6raQw• Tallest woman• http://www.youtube.com/watch?

v=F0V_8ZXZyzM• Gigantism at National Geographic 44:55

Adrenal GlandsAdrenal glands consist of the adrenal medulla and the cortex. The medulla secretes hormones (epinephrine and norepinephrine) during stressful and

emotional situations, while the adrenal cortex regulates salt and carbohydrate

metabolism.

Endocrine Glands

• Thyroid gland – metabolism, calcium

• Pineal gland - sleep and wakefulness

• Pancreas - regulates blood sugar level

• Ovaries and testes - secrete sex hormones such as testosterone and estrogen

• Altering neurons with light at ted talks 18:24

• Recording neuronal activity at ted talks 17:35

• http://www.ted.com/talks/gero_miesenboeck

EXPLORING PSYCHOLOGY(7th Edition in Modules)

David MyersPowerPoint Slides

Aneeq AhmadHenderson State

University

Worth Publishers, © 2008