Neural and Hormonal Systems Module 3 Neural and Hormonal Systems

Neural Communication The Nervous System The Endocrine System Neurons How Neurons Communicate How Neurotransmitters Influence Us The Nervous System The Peripheral Nervous System The Central Nervous System The Endocrine System

History of Mind Phrenology In 1800, Franz Gall suggested that bumps of the skull represented mental abilities. His theory, though incorrect, nevertheless proposed that different mental abilities were modular. Preview Question 1: Why do psychologists study biology? Bettman/ Corbis

The Nervous System Neuron Approx. 100 billion neurons (1011) a nerve cell the basic building block of the nervous system Approx. 100 billion neurons (1011) Approx. 300-400 trillion synapses (1014)

Hummm??? How many is 400 trillion really?

The Nervous System Nervous System Central Nervous System (CNS) the body’s speedy, electrochemical communication system consists of all the nerve cells of the peripheral and central nervous systems 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

The Nervous System Nerves neural “cables” containing many axons part of the peripheral nervous system connect the central nervous system with muscles, glands, and sense organs

The Nervous System Sensory Neurons Motor Neurons neurons that carry incoming information from the sense receptors to the central nervous system Motor Neurons carry outgoing information from the CNS to muscles and glands

The Nervous System Interneurons CNS neurons that internally communicate and intervene between the sensory inputs and motor outputs

Central Nervous System The Brain and Neural Networks Interconnected neurons form networks in the brain. Theses networks are complex and modify with growth and experience. Complex Neural Network

Neural Communication Dendrite Axon Myelin [MY-uh-lin] Sheath the bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body Axon the extension of a neuron, ending in branching terminal fibers, through which messages are sent to other neurons or to muscles or glands Myelin [MY-uh-lin] Sheath a layer of fatty cells segmentally encasing the fibers of many neurons enables vastly greater transmission speed of neutral impulses

Neural Communication

Threshold Threshold: Each neuron receives excitatory and inhibitory signals from many neurons. When the excitatory signals minus the inhibitory signals exceed a minimum intensity (threshold) the neuron fires an action potential.

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. This tiny gap is called the synaptic gap or cleft. Preview Question 3: How do nerve cells communicate? Synapse was coined by Lord Sherrington (1857-1952) who inferred it through behavioral experiments. Cajal (1852-1934) described the synapse based on his anatomical studies of the brain.

Neurotransmitters Neurotransmitters (chemicals) released from the sending neuron travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing it to generate an action potential.

Reuptake Neurotransmitters in the synapse are reabsorbed into the sending neurons through the process of reuptake. This process applies the brakes on neurotransmitter action.

Neural Communication

How Neurotransmitters Influence Us A particular pathway in the brain may use only one or two neurotransmitters and particular neurotransmitters may have particular effects on behavior and emotions

How Neurotransmitters Influence Us Serotonin pathways are involved with mood regulation. Preview Question 4: How do neurotransmitters influence human behavior? From Mapping the Mind, Rita Carter, © 1989 University of California Press

Dopamine Pathways Dopamine pathways are involved with diseases such as schizophrenia and Parkinson’s disease. From Mapping the Mind, Rita Carter, © 1989 University of California Press

Neurotransmitters

Lock & Key Mechanism Neurotransmitters bind to the receptors of the receiving neuron in a key-lock mechanism.

Agonists

Antagonists

How Neurotransmitters Influence Us Endorphins [en - DOR-fins]: “morphine within”— natural, opiatelike neurotransmitters linked to pain control and to pleasure. Drugs and other chemicals affect brain chemistry at synapses: Agonist molecules bind to a neurotransmitter’s receptor and mimics its effects. Antagonists bind to receptors and block a neurotransmitter’s functioning.

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.

The Nervous System Autonomic Nervous System Sympathetic Nervous System the part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart) Sympathetic Nervous System division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations Parasympathetic Nervous System division of the autonomic nervous system that calms the body, conserving its energy

Nervous System Preview Question 4: What are the functional divisions of the nervous system?

Autonomic Nervous System (ANS) Sympathetic NS “Arouses” (fight-or-flight) Parasympathetic NS “Calms” (rest and digest)

A Simple Reflex

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. Preview Question 5: How does the endocrine system-the body’s slower information system-transmit its messages?

Hormones Hormones are chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream, and affect other tissues.. For example, epinephrine (adrenaline) increases heart rate, blood pressure, blood sugar, and feelings of excitement during emergency situations.

The Endocrine System adrenal [ah - DREEN-el] glands: pair of endocrine glands that sit just above the kidneys and secrete hormones (epinephrine and norepinephrine) that help arouse the body in times of stress. pituitary gland: the endocrine system’s most influential gland. Under the influence of the hypothalamus, it regulates growth and controls other endocrine glands.