Neural and Hormonal Systems
Neural and Hormonal Systems are important systems that we should know more about. Every thought, feeling, and action is biological.
By the end of this section, you should know about:
- Why are psychologists concerned with human biology?
- Historical Foundations of Brain Studies
- Importance of the nervous system in behavior and cognition
- The Nervous System: A Dynamic Network
- The Central Nervous System (CNS)
- Types of Neurons
- The Endocrine System
Let’s take a closer look at them.
Test Your Knowledge
At the end of this section, take a fast and free pop quiz to see how much you know about Neural and Hormonal Systems.
Why are psychologists concerned with human biology?
Psychologists emphasize the important relationship between biological processes and human behavior. Every thought, feeling, and action is fundamentally biological. Without the physical systems in our bodies—genes, brains, and nervous systems—our psychological experiences could not exist. Ancient philosophers like Plato and Aristotle discussed the relationship between mind and body, Plato assigned the mind to the brain and Aristotle mistakenly assigned it to the heart Though such early ideas lacked scientific rigor, but modern biology emphasizes that it is controlled by the brain, not the emotions and actions of the heart.
Historical Foundations of Brain Studies
In the 19th century, Franz Gall introduced phrenology, the study of skull curves to calculate psychological symptoms. Although dismissed as a pseudoscience, phrenology played an important role in illuminating the idea of the localized brain. Today, neuroscience uses sophisticated methods to probe the complexities of the brain, revealing the functions of specific brain regions, and how the systems that together create human experience extend to the cultural context in the various fields
To understand neurons and their role in communication
Nerves are the foundation of the nervous system and they carry information through electrical signals. Each neuron has a cell body, dendrites that receive signals, and transmit them intact. The myelin sheath surrounding the axon increases the speed of signal transmission. These neurons are supported by glial cells that nourish and protect neurons and are involved in memory and learning. Notably, the proportion of glial cells increases with brain complexity, as seen in such prominent examples as Einstein’s brain.
Neural and Hormonal Systems: electrical phenomena in music
The nerves produce action potentials, brief electrical impulses triggered by external stimuli or chemical cues. This impulse travels along the axons, opening ion channels in a domino effect. The process is based on the exchange of energetic ions, producing a dynamic system of relaxation, depolarization, and refractive moments. Despite these speeds, human reaction times are slower than computer reactions, indicating the complexity of biological computation.
Decision and stimulus responses in neurons
Each neuron acts as a decision maker, processing excitatory and inhibitory signals from other neurons. When excitatory signals exceed thresholds, the neuron fires a general response, such as whether a gun fires or not. Strong stimuli do not increase the velocity or intensity of the impulse but instead cause more frequent firing or add an additional muscle. This mechanism allows the nervous system to distinguish between subtle and intense sensory stimuli, such as a light touch and a firm hug.
Biological perspective concerned with the links between biology and behavior. Includes psychologists working in neuroscience, behavior genetics, and evolutionary psychology. These researchers may call themselves behavioral neuroscientists, neuropsychologists, behavior geneticists, physiological psychologists, or biopsychologists.
Neuron is a nerve cell; the basic building block of the nervous system.
Dendrites a neuron’s bushy, branching extensions that receive messages and conduct impulses toward the cell body.
Axon the neuron extension that passes messages through its branches to other neurons or to muscles or glands.
Myelin [MY-uh-lin] sheaths a fatty tissue layer segmentally encasing the axons of some neurons; enables vastly greater transmission speed as neural impulses hop from one node to the next.
Glial cells (glia) cells in the nervous system that support, nourish, and protect neurons; they may also play a role in learning, thinking, and memory.
Action potential is a neural impulse; a brief electrical charge that travels down an axon.
Synapse [SIN-aps] the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. The tiny gap at this junction is called the synaptic gap or synaptic cleft.
Neurotransmitters are chemical messengers that cross the synaptic gaps between neurons. When released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether that neuron will generate a neural impulse.
Reuptake a neurotransmitter’s reabsorption by the sending neuron.
Importance of the nervous system in behavior and cognition
Shared principles in neurons allow scientists to study simple biology to understand how the human brain works. These insights reveal the extraordinary complexity of how neurons and their fibers give rise to thoughts, feelings, and actions. By capturing how neural activity interacts, we deepen our understanding of the biology underlying human cognition and behavior.
Neural and Hormonal Systems: The Protoplasmic Connection
The neurons are intricately connected, allowing for seamless communication. Early researchers including Sir Charles Sherrington discovered that synapses- tiny gaps in neurons act as junctions for information transfer These synaptic gaps release neurotransmitters from the axon terminals of a single neuron, with receptor sites on neuron on the next small space for bonding This particular spinning process allows charged ions to flow, and the receptor excited or inhibited neuron’s ready to fire. Subsequently, excess neurons are destroyed, migrate, and are reabsorbed through a mechanism called reuptake.
Neural and Hormonal Systems: The Role of Neurotransmitters in Behavior and Emotion
Neurotransmitters, intravenous chemicals, have a profound effect on both physical and emotional states. For example, acetylcholine (ACh) plays an important role in learning, memory, and motor function. ACh is required for muscle contraction; In its absence it causes paralysis, as seen in some forms of anesthesia. Other neurotransmitters, such as endorphins, are naturally produced by the brain and act as opiates, reducing pain and improving mood. Endorphins explain phenomena like “runner’s high” and mild pain in extreme situations. However, these systems can be chemically manipulated to disrupt the body’s natural chemical balance.
How Drugs Alter Neurotransmitter Activity
Drugs affect vascular permeability by increasing or inhibiting vascular endothelial activity. Agonists enhance neurotransmitter activity by enhancing, inhibiting reuptake, or mimicking its activity. Opiates, for example, act as antidotes, increasing mood and temporarily experiencing euphoria. In contrast, antagonists block neurotransmitter activity by blocking its inhibition or by inactivating its receptor sites. For example, botulinum toxin (Botox) causes neuropathy by blocking ACh inhibition, while curare blocks nerve activity by recruiting ACh-occupied areas without stimulating them.
Neural and Hormonal Systems: Balancing the Brain’s Chemistry
The use of chemicals to alter neurotransmitter function can have profound consequences. The production of natural neurotransmitters can be suppressed by injecting the brain with substances such as heroin or morphine. This pressure can lead to dependence and cessation of symptoms when the drug is discontinued. The delicate balance of the brain highlights the risks and challenges of altering neurogenesis, whether through medical intervention or substance abuse. Understanding this balance is critical to address the effects of drugs on behavior and mental health.
The Nervous System: A Dynamic Network
The communication and decision-making nervous system, divided into two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS) Together they coordinate the reception, processing and transmission of information, allowing us to respond to intrinsic and extrinsic stimuli.
Endorphins [en-DOR-fins] “morphine within”—natural, opiate-like neurotransmitters linked to pain control and to pleasure.
Nervous system the body’s speedy, electrochemical communication network, consisting 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.
Nerves bundled axons that form neural cables connecting the central nervous system with muscles, glands, and sense organs.
Sensory (afferent) neurons that carry incoming information from the sensory receptors to the brain and spinal cord.
Motor (efferent) neurons that carry outgoing information from the brain and spinal cord to the muscles and glands.
Interneurons neurons within the brain and spinal cord; communicate internally and process information between the sensory inputs and motor outputs.
Somatic nervous system the division of the peripheral nervous system that controls the body’s skeletal muscles. Also called the skeletal nervous system.
Autonomic [aw-tuh-NAHM-ik] nervous system (ANS) the part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). Its sympathetic division arouses; its parasympathetic division calms.
Sympathetic nervous system the division of the autonomic nervous system that arouses the body, mobilizing its energy.Parasympathetic nervous system the division of the autonomic nervous system that calms the body, conserving its energy.
The Central Nervous System (CNS)
Neural and Hormonal Systems: Brain
The center of thought, perception and action. The 400 million neurons of the brain, each made up of thousands of connections, are complex networks of about 400 billion synapses it enhances learning and memory.
Neural and Hormonal Systems: Spinal cord
An important two-way highway connecting the brain to the rest of the body. It controls reflex actions independently of the brain, like moving your hand away from a hot flame before you feel pain. A spinal cord injury can sever the connections, leading to paralysis and loss of sensation below the point of injury.
Neural and Hormonal Systems: Pituitary Nervous System (PNS)
The PNS extends the reach of the CNS, connecting it to the rest of the body. It consists of two main parts:
Neural and Hormonal Systems: Somatic Nervous System (SNS)
It controls the voluntary muscles. For example, when you read this text and turn the page, you rely on the SNS to send signals between your brain and bones and muscles.
Neural and Hormonal Systems: Autonomic nervous system (ANS)
It regulates involuntary functions, such as heart rate, digestion, and nerve activity.
Sympathetic Division
Prepares the body to respond to stressful situations by increasing heart rate, blood sugar levels, and slowing down digestion.
Parasympathetic compartment
Calms the body after stress, stores energy and restores balance (homeostasis).
Types of Neurons
Information in the nervous system flows through three types of neurons:
Sensory nerves (Afferent): transmit signals from sensory nerves to the CNS.
Motor Neurons (Efferent): Send signals from the CNS to nerves and nerves.
Neurons: Reside in the CNS and process information between sensory input and output. These make up the bulk of the nervous system and are responsible for our cognitive processes.
Reflexes and Neural Pathways
Movements such as twisting a knee or pulling away from a flame reflect the activity of the spinal cord. These actions occur without the involvement of the brain, as sensory neurons send signals directly to the motor nervous system via neurons in the spinal cord. But pain or pleasure requires emotional information to reach the brain.
Implications for spinal cord injury
A spinal cord injury can cause paralysis and laceration of the brain and body below the injury. Reflex functions persist, but consciousness and voluntary control are lost. Despite this, local sensations such as erection or lubrication can still occur due to an intact sensory pathway, even in the absence of heightened sensitivity and response
This complex CNS and PNS system underlie every aspect of our interaction with the world, from basic thoughts to complex voluntary actions.
Reflex a simple, automatic response to a sensory stimulus, such as the knee-jerk response.
Endocrine [EN-duh-krin] system the body’s “slow” chemical communication system; a set of glands that secrete hormones into the bloodstream.
Hormones chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream, and affect other tissues.
Adrenal [ah-DREEN-el] glands a 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, the pituitary regulates growth and controls other endocrine glands.
The Endocrine System
The endocrine system is the body’s slower but longer-lasting chemical communication system. It works in tandem with the nervous system to regulate bodily functions, influencing our behavior, emotions, and physiological responses.
Key Features of the Endocrine System
Receptor cells secrete coagulation factors into the bloodstream, which reach target tissues, including the brain. These hormones regulate such processes as metabolism, growth, reproduction, and cognition. Unlike the rapid neurotransmitter-dependent communication of neurons, hormonal signals are slow but have lasting effects.
Endocrine vs. Nervous System
Muscle fibers
Fast, accurate, and short-lived; It works through electrical signals and neurotransmitters.
Endocrine system
Slow, diffuse, and long lasting; It relies on the release of hormones into the bloodstream.
Hormone response and persistence
Hormones can outlast neurological signals, which is why emotional states like fear or sadness can persist even after the triggering event has passed. This ability was demonstrated in experiments in which brain-damaged subjects retained emotional states from movies even though they had no memory of the content.
The main components and their functions
These neurons on the kidneys release epinephrine (adrenaline) and norepinephrine (noradrenaline) in response to stress.
Results include increased heart rate, blood pressure, and strength in preparation for a “fight or flight” response. The hormone levels persist even when stress has subsided, resulting in alertness and emotional stability.
Pituitary Gland (“Mr. Gland”)
Under the control of the hypothalamus, the pituitary secretes hormones that regulate growth, reproduction, and mating.
Growth hormone stimulates physical development.
Oxytocin
Facilitates birth, breastfeeding and communication. It also promotes social trust and cooperation, as seen in experiments in which participants given oxytocin showed greater trust in gambling games.
Controlling other glands
The pituitary signals the adrenals, sex glands and other glands to release their hormones, which then go back to the brain to affect behavior and emotions
The hypothalamic-pituitary-adrenal (HPA) axis
It’s a feedback loop that connects the brain and endocrine system.
For example, in response to stress, the hypothalamus signals the pituitary to release a hormone that stimulates the adrenal glands to release cortisol from blood sugar, preparing the body for prolonged stress
Muscle and metabolic interdependence
The endocrine and nervous systems work closely together, forming a feedback loop:
The nervous system initiates an endocrine response.
Hormones then affect the nervous system, altering nerve function, mood, and behavior.
This simple system, orchestrated by the brain, balances the body and responds appropriately to its environment.
By combining rapid nerve signals with long-term hormonal messages, the body ensures immediate response and ongoing adaptation.
So chapter provides an in-depth understanding of brain structure and function, focusing on tools and techniques for studying neural activity such as PET scans and EEG, and exploring areas such as the brainstem, thalamus, brain of the nervous system, and limbic system. Also highlights the cerebral cortex’s contribution to movement coordination The hypothalamus controls hunger and integrates the nervous and endocrine systems, while the hippocampus and amygdala are important for memory and cognitive processing.