2007PSY Mid Tri Exam Notes

Discuss different applications of biological psychology?

Behavioural neuroscience (or biological psychology) was formed by scientists who combined the experimental methods of psychology with those of physiology. In recent years, information from experimental biology, chemistry, animal behaviour, psychology, computer science, and other fields has contributed to creating the diverse interdisciplinary field of biological psychology. The outcome of biological psychology is to explain the relationship between the brain and behaviour.

What is the difference between generalisation and reduction in biological psychology?

A generalisation is a broader explanation based on many different smaller observations of a similar phenomenon. Reduction however refers to the explanation of a broader complex phenomenon using a series of smaller ones. Research efforts of behavioural neuroscientists involve both forms of explanation, as research is fuelled both by psychological generalisations about behaviour and the physiological mechanisms that underlie it.

Discuss the history of biological psychology and its approach to the mind-body problem?

Generalisation and reduction are two of the main approaches used in biological psychology. Humans have long been interested in the mind, and philosophers have debated its relationship to the physical body and the brain. As an example, some have considered the mind separate from the body, whereas others argue that the mind arises from the body. These debates have been labelled the mind-body problem, which can be explained by two different approaches. Dualism is a belief in the dual nature of reality, that the mind and body are separate (the body is made up of ordinary matter, but the mind is not). On the other hand, monism is a belief that everything in the universe consists of matter and energy and that the mind is a phenomenon produced by the workings of the nervous system. Biological psychology tends to take a monistic approach.

What is the rubber-hand illusion

The rubber-hand illusion shows how light information is encoded by receptors in the eyes and touch information is encoded by receptors in the skin. This conflicting information from the receptors gets sent to the cortex of the brain, where the brain misattributes the touch signal to an object that is outside the body (the rubber hand) and the mind is mistaken into thinking the rubber hand is its own. It demonstrates the nuanced relationship between body and mind.

Explain what functionalism and natural selection is within the context of biological psychology?

The principle of functionalism states that the best way to understand a biological phenomenon (e.g., a behaviour or a physiological structure) is to try and understand its useful functions for the organism.

Natural selection is the process by which inherited traits that confer a selective advantage (increase an animals likelihood to live and reproduce) become more prevalent in a population.

Why are human brains different in size to other species?

From a biological psychology perspective, human brains are significantly larger relative to body size compared to other species due to the evolutionary pressures of complex social interactions, advanced tool use, and the need to solve intricate environmental challenges. These pressures require a larger brain capacity for cognitive processing, particularly within the neocortex.

What are the university and national guidelines that govern animal research - including the 3 R's?

At Griffith, the Australian Code for the Care and Use of Animals for Scientific Purposes, and the Queensland Animal Care Protection Act guide animal research. There are many guidelines that govern animal research, the most important however are; respect for animals, justification of use, minimisation of harm, high standards of animal care, ethical review and oversight, training and competence, and transparency and accountability. The 3 R's are in national and international legislation and regulatory requirements that stand for replacement, reduction and refinement. Replacement involves using methods that avoid or replace the use of animals, reduction involves using methods that minimise the number of animals used per study, and refinement involves methods that minimise pain and distress and improve animal welfare.

What is informed consent in human research and in the field of neuroethics?

Neuroethics in an interdisciplinary field devoted to understanding implications of and developing best practices in ethics for neuroscience research. Informed consent is the process in which researchers must inform any potential participant about the nature of the research study, how any data will be collected and stored, and what the anticipated benefits and cost of participating will be.

Define the central and peripheral nervous system

The CNS and the PNS are both parts of the nervous system. The CNS is made up of the brain and spinal cord and is the control centre of the body. The PNS consists of all the nerves and sensory organs that lie outside the brain and spinal cord. Nerves that are connected to the brain are cranial nerves, whereas nerves connected to the spine are spinal nerves. There are 3 different neurons in the PNS, sensor neurons detect environmental changes and send information to the CNS. Interneurons are found in between sensory and motor neurons in the CNS, and finally motor neurons contract muscles and glands that control motor behaviour.

Locate and define key parts of a neuron

Neurons are made of different parts. The soma is the cell body of a neuron, which has many different layers inside. The membrane surrounds the soma and is made up of proteins that detect or transport substances in and out of the cell. The cytoskeleton is made up of protein strands, and the cytoplasm is the space inside the membrane that contains organelles. The axon is responsible for transmitting electrochemical messages on its surface from the cell body down to the terminal buttons. The myelin sheath wraps around the axon to stop neuron messages from interfering with each other. The nodes of Ranvier are the small gaps in the myelin sheath that allow for saltatory conduction of an AP. The  terminal buttons send chemical messages to other neurons, and the dendrites receive those chemical messages to other neurons.

Describe the functions of glial cells in the nervous system

Glial cells are non-neuronal cells that provide support and maintenance to the neurons of the NS. They keep neurons together, which helps maintain structure and integrity of the NS. They control chemical and nutrient supply, provide protection, and destroy or remove dead neurons. Glial cells in the CNS are different to those in the PNS. In the CNS, there are 3 different types of glial cells. First are astrocytes, which supply nutrients (glucose) and oxygen to neurons and help with chemical regulation. Microglia help with damage control and immune function. Oligodendrocytes produce myelin for insulation, which cover axons that have gaps. In the PNS, there are Schwann cells, which produce myelin for the PNS (they are different to oligodendrocytes).

Describe why the blood-brain-barrier (BBB) in crucial for the nervous system

Cells forming the BBB are tightly packed together. The BBB is crucial for protecting the brain by selectively blocking harmful substances, toxins, and pathogens from entering while allowing essential nutrients, like glucose and oxygen, to pass through. It helps maintain a stable chemical environment for optimal brain function, regulates neurotransmitter levels, and prevents fluctuations in blood composition from disrupting neural activity. The BBB also protects against inflammation and plays a key role in preserving homeostasis, ensuring that the brain's delicate environment remains conducive to proper neural signalling and overall brain health.

Use the withdrawal reflex to describe excitatory and inhibitory neural communication

The withdraw reflex is an involuntary response to painful stimuli that helps protect the body from harm. When a painful stimulus activates sensory neurons, they send signals to the spinal cord. In the spinal cord, excitatory neurons stimulate motor neurons to contract muscles and quickly withdraw the affected body part. Simultaneously, inhibitory neurons prevent opposing muscles from contracting, allowing for a quick withdrawal. The communication between excitatory and inhibitory neurons ensures the body reacts swiftly to pain, with excitatory signals driving the withdrawal and inhibitory signals preventing counterproductive muscle activity.

Define membrane potential, resting potential, hyperpolarization, depolarization, and the action potential

A membrane potential is the difference in electrical potential inside VS outside a neuron. The resting potential is always at -70mv. Hyperpolarization is negative, meaning it is less likely an action potential will occur. On the other hand, depolarization is positive, meaning it is more likely that an action potential will occur. The threshold of excitation occurs when there is enough depolarization occurring in the neuron. An action potential is a wave of depolarization that spreads down an axon, from the soma towards the terminal buttons. When this wave has reached the terminal buttons, the action potential causes the neurotransmitter to be released into the synapses.

Describe how diffusion, electrostatic pressure and the sodium potassium pump determine the resting potential of a neuron

Ions are either inside or outside a neuron, which are either positively or negatively charged. The concentration of ions determines the resting charge of an ion. Diffusion causes ions to move from areas of high concentration to low concentration, with potassium ions (K+) concentrated inside the neuron and sodium ions (Na+) outside. Electrostatic pressure, driven by the charge differences between inside and outside the cell, attracts oppositely charged ions (e.g., Na+ towards the inside and K+ towards the outside). The sodium-potassium pump helps maintain the resting potential by actively transporting three sodium ions out of the cell and two potassium ions into the cell, against their concentration gradients. This active transport helps create and maintain the concentration differences, with more Na+ outside and more K+ inside, while also contributing to a negative internal charge relative to the outside, around -70 mv. Together, these processes establish the neuron's resting potential, providing the electrical charge necessary for action potentials and neural communication.

Describe voltage gated ion channels, and how ions move during an action potential

VGIC are specialized proteins in the neuron's membrane that open or close in response to changes in membrane potential. During an action potential, sodium (Na+) channels open, allowing Na+ to rush into the cell, depolarizing the membrane, followed by the opening of potassium (K+) channels, allowing K+ to exit the cell, which repolarizes the membrane and restores the resting potential.

Describe how action potentials are sent down the axon of a neuron

Action potentials travel down the axon of a neuron through a process called saltatory conduction in myelinated axons, where the electrical signal jumps from one node of Ranvier to the next, speeding up transmission. In unmyelinated axons, the action potential moves along the axon in a continuous wave as voltage-gated ion channels sequentially open and close, propagating the signal down the length of the axon.

Identify different types of synapses and describe their key structures

Synapses are formed between the terminal buttons of the presynaptic cell and the dendritic membrane of the postsynaptic cell - either a smooth dendrite or a dendritic spine. Synapses are also formed between the terminal buttons of the presynaptic cell and the somatic membrane of the postsynaptic cell, or the terminal button of a postsynaptic cell.

Describe the role of ionotropic and metabotropic receptors on the postsynaptic cell

When a neurotransmitter molecule attaches to binding sites on postsynaptic receptors, postsynaptic potentials (PSPs) are generated. Ionotropic receptors open ion channels directly as there is a neurotransmitter binding site and an ion channel. Whereas metabotropic receptors open ion channels indirectly as there is a neurotransmitter binding site but no ion channel.

Describe how neurotransmitter dependent ion channels on the postsynaptic cell influence postsynaptic potentials

Neurotransmitter-dependent ion channels on the postsynaptic cell open in response to neurotransmitter binding, allowing specific ions to flow in or out of the cell. This ion movement generates postsynaptic potentials—excitatory postsynaptic potentials (EPSPs) if positively charged ions enter, or inhibitory postsynaptic potentials (IPSPs) if negatively charged ions enter, altering the membrane potential of the postsynaptic cell and influencing its likelihood of firing an action potential.

Define the processes of reuptake and enzymatic deactivation

Once a neurotransmitter enters the synapse, receptor binding causes hyperpolarization and depolarization of the postsynaptic cell. Reuptake occurs when neurotransmitter molecules in the synapse are taken back up into the terminal buttons of the presynaptic cell. Whereas enzymatic deactivation removes neurotransmitter molecules from the synapse by breaking them into smaller parts.

Explain how postsynaptic potentials are integrated to determine if an action potential is triggered

Postsynaptic potentials (PSPs) are integrated by the postsynaptic neuron at the axon hillock, where the summed effects of excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) determine whether the membrane potential reaches the threshold needed to trigger an action potential. If the cumulative EPSPs depolarize the membrane sufficiently to reach the threshold, voltage-gated sodium channels open, leading to the initiation of an action potential. Conversely, if IPSPs dominate and the membrane remains hyperpolarized, no action potential will occur.

Describe the roles of autoreceptors and axoaxonic synapses in regulating neurotransmitter release

Autoreceptors are receptor proteins on the membrane of the presynaptic neuron that help regulate neurotransmitter levels. When activated, they typically inhibit further neurotransmitter release, acting as a feedback mechanism to regulate the amount of neurotransmitter in the synaptic cleft and prevent overstimulation. Axoaxonic synapses are formed between the terminal buttons of two neurons that modulate neurotransmitter release and control the strength of the synaptic transmission. When the presynaptic axon is activated, it can modulate the release of neurotransmitters from the second neuron, often through mechanisms like presynaptic facilitation or inhibition, affecting the strength of synaptic transmission without direct involvement of the postsynaptic cell.

Identify the role of neuromodulators and hormones in the functioning the nervous system

Neuromodulators diffuse across extracellular fluid more broadly and can influence the activity of several neurons at once. Whereas hormones are chemicals that are released by endocrine glands that are then distributed through the bloodstream and can influence neuronal activity.

Use anatomical terms to describe the nervous system

The nervous system is divided into two main components: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The brain, located within the cranial cavity, is responsible for processing sensory information, higher functions like thought and memory, and initiating motor control. The brain includes the cerebrum, which is involved in sensory perception and voluntary movement, the cerebellum, which coordinates balance and motor control, and the diencephalon, which includes the thalamus and hypothalamus, responsible for sensory relay and autonomic regulation. The brainstem, composed of the midbrain, pons, and medulla oblongata, manages vital functions such as heartbeat, breathing, and blood pressure. The spinal cord, located within the vertebral canal, connects the brain to the rest of the body, transmitting motor and sensory signals and controlling reflex actions.

The PNS comprises the cranial nerves, which originate from the brain and handle functions like vision and facial muscle movement, and the spinal nerves, which emerge from the spinal cord and serve as pathways for communication between the CNS and the body. The PNS is further divided into the somatic nervous system, which governs voluntary movements and sensory input from the skin, muscles, and joints, and the autonomic nervous system (ANS), which regulates involuntary functions such as heart rate and digestion. The ANS has two divisions: the sympathetic division, which prepares the body for "fight or flight" responses, and the parasympathetic division, which promotes "rest and digest" functions.

At the cellular level, the nervous system is composed of neurons and glial cells. Sensory neurons (afferent neurons) transmit sensory information from the body to the CNS, while motor neurons (efferent neurons) carry motor commands from the CNS to muscles and glands. Interneurons within the CNS process and relay information between sensory and motor neurons. Glial cells, such as astrocytes, oligodendrocytes, microglia, and Schwann cells, provide structural support, nourishment, and protection for neurons. The coordination of these components allows the nervous system to regulate and maintain bodily functions, facilitate movement, and respond to the environment.

Describe how the meninges, cerebrospinal fluid, and ventricular system support the nervous system

The meninges is made of layers of connective tissue that covers the NS to provide protection and structure. In the CNS, the meninges has 3 layers, the dura mater forms the outer layer, the arachnoid membrane forms the middle layer, and the pia mater is shaped to the brains surface. In the arachnoid membrane, there is subarachnoid space that is filled with cerebrospinal fluid produced by the ventricular system. This fluid is a shock absorber and material exchanger. The PNS has the same layers, but only the dura mater and the pia mater.

Locate and describe key structures/functions of the forebrain

The forebrain is the largest and most complex region of the brain, located at the front of the cranial cavity, and it is crucial for higher cognitive functions, sensory processing, and emotional regulation. It consists of two main divisions: the telencephalon and the diencephalon. The telencephalon includes the cerebrum, which is divided into two hemispheres and is responsible for advanced functions such as thought, voluntary movement, reasoning, and perception. The cerebrum is further divided into lobes: the frontal lobe, which is involved in decision-making, problem-solving, and motor control; the parietal lobe, responsible for processing sensory information related to touch, temperature, and spatial orientation; the temporal lobe, which processes auditory information, memory, and language; and the occipital lobe, primarily involved in visual processing.

Within the cerebrum, specific regions are responsible for different types of sensory and motor functions. The sensory cortex is located in the parietal lobe and is responsible for processing sensory information from the body, including touch, pain, and temperature. The somatosensory cortex specifically processes these sensations and maps them to corresponding areas of the body. The visual cortex, located in the occipital lobe, is responsible for interpreting visual information from the eyes. The auditory cortex, found in the temporal lobe, processes sound and is crucial for hearing. The motor cortex, located in the frontal lobe, controls voluntary movements by sending signals to muscles throughout the body.

Beneath the telencephalon lies the diencephalon, which contains several critical structures. The thalamus, located near the centre of the forebrain, acts as a relay station, directing sensory information (except for smell) from the body to the appropriate regions of the cerebral cortex for processing. It plays a key role in regulating consciousness, sleep, and alertness. The hypothalamus, situated just below the thalamus, is essential for maintaining homeostasis by regulating vital bodily functions such as temperature, hunger, thirst, and circadian rhythms. It also controls the autonomic nervous system and links the nervous system to the endocrine system through the pituitary gland. The pituitary gland is divided into two parts: the anterior pituitary, which secretes hormones such as growth hormone, thyroid-stimulating hormone, and gonadotropins to regulate growth, metabolism, and reproduction, and the posterior pituitary, which stores and releases hormones like oxytocin and vasopressin, crucial for processes such as childbirth, lactation, and water balance.

Together, the structures of the telencephalon and diencephalon are essential for sensory processing, emotional regulation, motor control, and maintaining homeostasis, making the forebrain central to the coordination of bodily functions and higher cognitive abilities.

Locate and describe key structures/functions of the midbrain

The midbrain (or mesencephalon) is a small, but vital region of the brain, located between the forebrain and the hindbrain, and it plays a key role in sensory processing, motor control, and maintaining alertness. The midbrain can be divided into two major parts: the tectum and the tegmentum, each with distinct functions.

The tectum is located at the dorsal (top) part of the midbrain and is primarily involved in visual and auditory processing. It contains two prominent structures: the superior colliculi and the inferior colliculi. The superior colliculi are involved in the integration of visual stimuli and control of eye movements, helping the brain direct visual attention toward important stimuli in the environment. The inferior colliculi play a critical role in auditory processing, particularly in locating the direction and source of sounds. These structures are essential for reflexive responses to visual and auditory cues, aiding in coordination and reaction to the environment.

Beneath the tectum lies the tegmentum, which is involved in a variety of functions, including motor control and regulating consciousness. The tegmentum houses several important structures, including the red nucleus and the substantia nigra. The red nucleus plays a significant role in motor coordination, particularly in controlling movements of the limbs. The substantia nigra, known for its dark appearance due to high levels of dopamine-producing neurons, is crucial for the control of movement and is involved in the initiation and smooth execution of voluntary movements. Degeneration of the substantia nigra is associated with Parkinson’s disease, a disorder characterized by motor impairments such as tremors and rigidity.

Additionally, the reticular formation runs through the tegmentum and plays a central role in regulating arousal, attention, and the sleep-wake cycle. It sends signals to the thalamus and other parts of the brain, influencing alertness and the ability to focus on sensory information.

Overall, the midbrain, including the tectum and tegmentum, is crucial for sensory processing, motor control, and regulating consciousness. It serves as an important relay station between different regions of the brain, contributing to both reflexive responses to environmental stimuli and higher-level processes like attention and movement coordination.

Locate and describe key structures/functions of the hindbrain

The hindbrain is a crucial part of the brainstem, located at the posterior part of the brain, and it is responsible for essential functions such as motor control, coordination, autonomic regulation, and maintaining balance. The hindbrain is divided into two primary regions: the metencephalon and the myelencephalon.

The metencephalon consists of the cerebellum and the pons. The cerebellum, located at the back of the brain, plays a central role in the coordination and fine-tuning of voluntary movements. It receives sensory input from the body and sends out motor commands to adjust movements for precision and balance. The cerebellum is also involved in motor learning and maintaining posture and equilibrium. It contains two hemispheres and a central structure called the vermis, which helps in coordinating movements and maintaining body balance. The pons, situated just below the cerebellum and above the medulla oblongata, acts as a communication bridge between different parts of the brain. It relays signals between the cerebrum and the cerebellum and also plays a role in regulating breathing through the pontine respiratory centres. Additionally, the pons houses nuclei involved in sleep, arousal, and facial sensations, and it helps control facial expressions and movements through cranial nerve nuclei.

The myelencephalon consists of the medulla oblongata, located just below the pons, at the junction of the brain and spinal cord. The medulla is responsible for regulating vital autonomic functions that are essential for survival, such as heart rate, blood pressure, and respiration. It contains the cardiac centre, which helps regulate the heart’s rate and force of contraction, and the vasomotor centre, which controls blood vessel diameter and thus blood pressure. The respiratory centres in the medulla regulate breathing patterns in response to changes in blood oxygen and carbon dioxide levels. In addition to these vital functions, the medulla oblongata is a conduit for motor and sensory signals traveling between the brain and spinal cord. It also contains the pyramidal decussation, where the motor fibers from the cerebral cortex cross over to the opposite side of the body, explaining why the right side of the brain controls the left side of the body, and vice versa.

Together, the structures of the hindbrain—the cerebellum, pons, and medulla oblongata—are critical for regulating basic life functions, coordinating movements, and maintaining balance. These regions ensure the smooth execution of voluntary motor activities, control vital autonomic functions, and allow the body to respond quickly and appropriately to changing internal and external conditions.

Locate and describe key structures/functions of the spinal cord

The spinal cord is a long, cylindrical structure that extends from the base of the brain (medulla oblongata) down through the vertebral column. It is a critical part of the central nervous system (CNS) and serves as the main communication pathway between the brain and the rest of the body. The spinal cord is responsible for transmitting motor commands from the brain to the muscles and sensory information from the body to the brain. Additionally, it plays a central role in reflex actions that occur without direct involvement of the brain.

The spinal cord is divided into segments that correspond to specific regions of the body. These segments give rise to spinal nerves, which are categorized based on the part of the body they serve: cervical, thoracic, lumbar, sacral, and coccygeal regions. Each spinal nerve emerges from the spinal cord through openings between the vertebrae and branches out to innervate muscles, skin, and organs.

Structurally, the spinal cord consists of grey matter and white matter. The grey matter, located centrally and shaped like a butterfly or "H," is primarily composed of neuron cell bodies and is involved in processing information. The grey matter is divided into dorsal (posterior) and ventral (anterior) horns. The dorsal horns receive sensory input from the body through the dorsal root ganglia, while the ventral horns contain motor neurons that send out commands to muscles.

The white matter, located on the outer part of the spinal cord, consists of myelinated ascending and descending tracts. The ascending tracts transmit sensory information from the body to the brain, while the descending tracts carry motor commands from the brain to the body. These tracts include pathways like the spinothalamic tract, which transmits pain and temperature sensations, and the corticospinal tract, which is involved in voluntary motor control.

In addition to its role in sensory and motor signal transmission, the spinal cord is also the site of many reflexes, which are rapid, automatic responses to stimuli that do not require the involvement of the brain. For example, in the patellar reflex, when the patellar tendon is tapped, sensory neurons carry the signal to the spinal cord, where it synapses with motor neurons that send an immediate command to contract the quadriceps muscle, causing the leg to kick.

Overall, the spinal cord is an essential conduit for communication between the brain and the rest of the body. It enables voluntary movements, processes sensory input, and mediates reflex actions, playing a critical role in the body's ability to respond to both internal and external stimuli.

Describe the functions of cranial and spinal nerves

Cranial and spinal nerves are essential components of the peripheral nervous system, responsible for transmitting sensory, motor, and mixed signals between the brain, spinal cord, and the body. Cranial nerves are twelve pairs of nerves that emerge directly from the brain, primarily from the brainstem. These nerves serve various functions, including sensory input, motor control, and autonomic regulation. For instance, the olfactory nerve (cranial nerve I) is responsible for the sense of smell, while the optic nerve (cranial nerve II) transmits visual information from the eyes to the brain. The vagus nerve (cranial nerve X) plays a crucial role in parasympathetic control, influencing heart rate, digestion, and respiratory functions. Other cranial nerves, such as the facial nerve (cranial nerve VII), control facial expressions and taste sensations, while the trigeminal nerve (cranial nerve V) provides sensation to the face and controls muscles involved in chewing.

Spinal nerves, on the other hand, are 31 pairs of nerves that emerge from the spinal cord, and they are responsible for transmitting signals between the spinal cord and the rest of the body. Each spinal nerve is associated with a specific region of the body and is named based on the segment of the spinal cord from which it arises (cervical, thoracic, lumbar, sacral, or coccygeal). Spinal nerves have both sensory and motor functions. Sensory fibers carry information from receptors in the skin, muscles, and organs to the central nervous system, allowing the body to perceive stimuli such as touch, pain, temperature, and pressure. Motor fibers transmit signals from the central nervous system to muscles, enabling voluntary movement. Additionally, the spinal nerves form plexuses, such as the brachial plexus and the lumbosacral plexus, which allow for more specific control and coordination of movement in the limbs. Reflexes, such as the knee-jerk response, also involve spinal nerves, allowing the body to respond to stimuli automatically, without the involvement of the brain. Together, cranial and spinal nerves play vital roles in sensory perception, motor function, and autonomic regulation, ensuring the body's ability to interact with and respond to the environment.

Describe the anatomy and functions of the sympathetic and parasympathetic divisions of the autonomic nervous system

The autonomic nervous system (ANS) is responsible for regulating involuntary bodily functions, and it is divided into two primary divisions: the sympathetic and parasympathetic systems. Both divisions work in tandem to maintain homeostasis, but they generally produce opposite effects on the body, particularly in response to stress and relaxation. The sympathetic division is often referred to as the "fight or flight" system, as it prepares the body for stressful or emergency situations. Anatomically, sympathetic nerves arise from the thoracolumbar region of the spinal cord, specifically from the T1 to L2 spinal segments. These nerves synapse in ganglia that are located near the spinal cord, forming a chain known as the sympathetic trunk. When activated, the sympathetic division increases heart rate, dilates the bronchioles in the lungs for improved airflow, dilates the pupils for better vision, and redirects blood flow from the digestive organs to the muscles, preparing the body for rapid action. It also stimulates the release of adrenaline (epinephrine) from the adrenal glands, further enhancing the body's response to stress.

In contrast, the parasympathetic division, often called the "rest and digest" system, works to conserve energy and promote relaxation and recovery after stress. The parasympathetic nerves originate primarily from the brainstem (specifically from cranial nerves III, VII, IX, and X) and the sacral region of the spinal cord. These nerves typically synapse in ganglia located near or within the target organs. When activated, the parasympathetic system slows the heart rate, constricts the pupils, stimulates digestive processes, and promotes the excretion of waste. For example, it increases peristalsis in the gastrointestinal tract, enhances salivation, and promotes the secretion of digestive enzymes, all of which aid in digestion and nutrient absorption. The parasympathetic system helps the body return to a state of balance after the activation of the sympathetic system, supporting activities like digestion, waste removal, and overall energy conservation.