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Neural and Hormonal Systems

Module 4

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Neural and Hormonal Systems

Neural Communication Neurons How Neurons Communicate How Neurotransmitters Influence Us

The Nervous System The Peripheral Nervous System The Central Nervous System

The Endocrine System

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History of the Mind

Plato correctly located mind in the brainAristotle believed that mind was in the

heart.

Today - mind and brain are faces of the same coin. Everything that is psychological is biological.

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History of the Mind

In 1800, Franz Gall - bumps of the skull represented mental

abilities. His theory is incorrect, but proposed different mental abilities

were modular.

Today - Biological Psychologists study the links between biology and psychology

Phrenology

Bettm

an/ Corbis

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Neural Communication

Note similarity of brain regions involved withinformation processing of similar kind.

Neurobiologists and other investigators understand that information processing in

humans and animals operate similarly.

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Neurons - the basic cell that makes up the nervous system and which receives and sends messages within that system.

Nerves – bundles of axons in the body that travel together through the body.

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Parts of a Neuron

Cell Body: Life support center of the neuron.

Dendrites: Branching extensions at the cell body. Receives messages from other neurons.

Axon: Long single extension of a neuron, covered with myelin [MY-uh-lin] sheath to insulate and speed up messages through neurons.

Terminal Branches of axon: Branched ending of axons. Transmitting messages to other neurons.

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Other Types of Brain Cells

• Glial cells - grey fatty cells that: – provide support for the neurons to grow on

and around,– deliver nutrients to neurons,– produce myelin to coat axons,– clean up waste products and dead

neurons.

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Kinds of Glia Cells

Astrocytes provide nutrition to neurons.

Oligodendrocytes and Schwann cells insulate neurons as

myelin.

Astrocytes

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Generating the Message: Neural Impulse

• Ions – charged particles.– Inside neuron – negatively charged.– Outside neuron – positively charged.

• Resting potential - the state of the neuron when not firing a neural impulse.

• Action potential - the release of the neural impulse consisting of a reversal of the electrical charge within the axon.– Allows positive sodium ions to enter the cell.

• All-or-none - referring to the fact that a neuron either fires completely or does not fire at all.

• Return to resting potential.

LO 2.2 Neurons and nerves

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Action PotentialA neural impulse. A

brief electrical charge that travels down an

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

axon’s membrane.

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Depolarization & Hyperpolarization

Depolarization: Depolarization occurs, when positive ions enter the neuron,

making it more susceptible to fire an action potential. When negative ions enter the neuron making it less susceptible to fire,

hyperpolarization occurs.

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Threshold

Threshold: Each neuron receives depolarizing and hyperpolarizing currents from many neurons. When the depolarizing

current (positive ions) minus the hyperpolarizing current (negative ions)

exceed minimum intensity (threshold) the neuron fires an action potential.

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Refractory Period & Pumps

Refractory Period: After a neuron has fired an action potential it pauses for a short period to recharge itself to fire

again.

Sodium-Potassium Pumps: Sodium-potassium pumps pump positive ions out

from the inside of the neuron, making them ready for another action potential.

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LO 2.2 Neurons and nerves

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Synapse

Synapse [SIN-aps] a junction between the axon tip of the sending neuron and the dendrite or

cell body of the receiving neuron. This tiny gap is called the synaptic gap or cleft.

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LO 2.3 Neuron communication

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NeurotransmittersNeurotransmitters

(chemicals) released from the sending neuron,

travel across the synapse and bind to receptor sites on the receiving neuron, causing it to generate an

action potential.

Excitatory neurotransmitter -

neurotransmitter that causes the receiving cell

to fire.Inhibitory

neurotransmitter - neurotransmitter that

causes the receiving cell to stop firing.

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Reuptake

Neurotransmitters in the synapse are

reabsorbed into the sending neurons.

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How Neurotransmitters Influence Us

Serotonin pathways are involved with mood regulation.

From Mapping the Mind, Rita Carter, © 1989 University of California Press

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Dopamine Pathways

Dopamine pathways are involved with

diseases like schizophrenia and

Parkinson’s disease.

From Mapping the Mind, Rita Carter, © 1989 University of California Press

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Neurotransmitters

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Lock & Key Mechanism

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

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Agonists

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Antagonists

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Nervous System

CentralNervousSystem(CNS)

Brain and Spinal cord

PeripheralNervousSystem(PNS)

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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.

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The Nervous System

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Kinds of NeuronsSensory 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.

Sensory Neuron(Bipolar)

Interneuron Neuron (Unipolar)

Motor Neuron(Multipolar)

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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.

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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.

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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.

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Autonomic Nervous System (ANS)

Sympathetic NS “Arouses”

(fight-or-flight)

Parasympathetic NS “Calms”

(rest and digest)

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Central Nervous System

The Spinal Cord and Reflexes

Simple Reflex

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Central Nervous System

The Brain and Neural Networks

Complex Neural Network

Interconnected neurons form networks in the brain. Theses networks are complex and modify with growth and experience.

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The Endocrine System

Endocrine System is the body’s “slow”

chemical communication

system. Communication is

carried out by hormones

synthesized by a set of glands.

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Hormones

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

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

For example, epinephrine (adrenaline) increases heart rate, blood pressure, blood

sugar and feelings of excitement during emergency situations.

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Pituitary Gland

Is called the “master gland.” Anterior pituitary lobe releases hormones that regulate other glands. Posterior lobe

regulates water and salt balance.

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Thyroid & Parathyroid Glands

Regulate metabolic and calcium rate.

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Adrenal GlandsAdrenal glands consists of adrenal medulla

and cortex. Medulla secretes hormones (epinephrine and norepinephrine) during stress and emotions, and adrenal cortex

regulates salt and carbohydrate metabolism.

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Gonads

Sex glands are differentially placed in men and women. Regulate bodily development

and maintain reproductive organs in adults.