PSY1BNA Week 2-Lecture (1 slide pp)

Types of Glial Cells and Their Functions

Glial cells, also known as neuroglia, play essential roles in supporting and maintaining the function of neurons. The various types include:

• Astrocytes:

  • Star-shaped cells that provide structural support to neurons.

  • Regulate blood flow and maintain the blood-brain barrier.

  • Supply nutrients to neurons and help in the repair of the nervous system after injury.

• Oligodendrocytes:

  • Found in the central nervous system (CNS).

  • Produce the myelin sheath that insulates axons, facilitating faster signal transmission.

• Schwann Cells:

  • Located in the peripheral nervous system (PNS).

  • Produce myelin sheaths for peripheral nerves, similar to oligodendrocytes in the CNS.

• Microglia:

  • The immune cells of the CNS.

  • Act as the brain's first line of defense against pathogens and injury.

  • Remove debris and dead neurons through phagocytosis.

• Ependymal Cells:

  • Line the ventricles of the brain and the central canal of the spinal cord.

  • Produce and circulate cerebrospinal fluid (CSF).

• Radial Glia:

  • Serve as scaffolding during brain development, guiding migrating neurons to their final destinations.

  • In some cases, can differentiate into neurons or other glial cells.

Each type of glial cell contributes to the overall health and functionality of the nervous system, supporting neurons in various ways, from structural support to immune defense.

Components of a Neuron

A neuron is composed of several key components, each serving a specific function in the transmission of electrical and chemical signals. The primary components of a neuron include:

• Cell Body (Soma):

  • Contains the nucleus and organelles. It is responsible for maintaining the cell's health and metabolic activities.

• Dendrites:

  • Branch-like structures that extend from the cell body. They receive signals from other neurons and transmit this information toward the cell body.

• Axon:

  • A long, slender projection that conducts electrical impulses away from the cell body. It can be covered by a myelin sheath, which insulates the axon and increases the speed of signal transmission.

• Axon Terminals (Synaptic Boutons):

  • The endpoints of the axon that release neurotransmitters into the synapse (the gap between neurons) to communicate with other neurons.

• Myelin Sheath:

  • A fatty layer that surrounds the axon in segments, formed by glial cells. It helps speed up the transmission of electrical signals along the axon.

• Nodes of Ranvier:

  • Gaps in the myelin sheath where the axon membrane is exposed. These nodes facilitate rapid signal transmission through a process called saltatory conduction.

These components work together to enable neurons to receive, process, and transmit information throughout the nervous system.

Parts of the Brain

The brain is a complex organ composed of several key parts, each responsible for different functions. Here are the main parts of the brain:

• Cerebrum:

  • The largest part of the brain, divided into two hemispheres (left and right).

  • Cerebral Cortex: The outer layer of the cerebrum, involved in higher brain functions such as thought, reasoning, memory, and voluntary muscle movements. It is further divided into four lobes:

    • Frontal Lobe: Responsible for executive functions, decision-making, problem-solving, and motor control.

    • Parietal Lobe: Processes sensory information such as touch, temperature, and pain; involved in spatial awareness.

    • Temporal Lobe: Involved in auditory processing, memory, and language comprehension.

    • Occipital Lobe: Primarily responsible for visual processing.

• Cerebellum:

  • Located at the back of the brain, beneath the cerebrum.

  • Responsible for coordination, balance, and fine motor skills. It helps regulate voluntary movements and is involved in learning motor tasks.

• Brainstem:

  • Connects the brain to the spinal cord and controls basic life functions.

  • Composed of three main structures:

    • Midbrain: Involved in vision, hearing, motor control, sleep/wake cycles, and temperature regulation.

    • Pons: Relays signals between different parts of the brain; involved in regulating sleep and respiration.

    • Medulla Oblongata: Controls vital functions such as heart rate, blood pressure, and breathing.

• Diencephalon:

  • Located beneath the cerebrum and above the brainstem; includes:

    • Thalamus: Acts as a relay station for sensory information before it reaches the cerebral cortex.

    • Hypothalamus: Regulates homeostasis, including temperature, hunger, thirst, and circadian rhythms. It also controls the pituitary gland, linking the nervous and endocrine systems.

• Limbic System:

  • A group of structures involved in emotion, memory, and motivation, including:

    • Amygdala: Plays a key role in processing emotions, particularly fear and pleasure.

    • Hippocampus: Essential for forming new memories and learning.

    • Cingulate Gyrus: Involved in emotion formation and processing, learning, and memory.

• Basal Ganglia:

  • A group of nuclei located deep within the cerebral hemispheres.

  • Involved in the regulation of voluntary motor control, procedural learning, and routine behaviors.

• Ventricles:

  • A system of interconnected cavities filled with cerebrospinal fluid (CSF) that cushions the brain and helps maintain its environment.

Summary

Each part of the brain plays a crucial role in overall brain function and behavior, working together to process information, control movements

Cranial Nerves and Spinal Nerves

Cranial nerves and spinal nerves are both essential components of the peripheral nervous system (PNS), responsible for transmitting sensory and motor information between the central nervous system (CNS) and the rest of the body. Here’s a breakdown of each:

Cranial Nerves

• Definition: Cranial nerves are a set of twelve pairs of nerves that emerge directly from the brain (specifically the brainstem) rather than the spinal cord.

• Function: They primarily serve the head and neck regions, carrying sensory information (such as smell, vision, and taste) and motor commands (such as movements of the face and neck).

• List of Cranial Nerves:

  • Olfactory Nerve (I): Responsible for the sense of smell.

  • Optic Nerve (II): Responsible for vision.

  • Oculomotor Nerve (III): Controls most eye movements, pupil constriction, and maintaining an open eyelid.

  • Trochlear Nerve (IV): Controls the superior oblique muscle, which is involved in rotating the eye.

  • Trigeminal Nerve (V): Responsible for sensation in the face and motor functions such as biting and chewing.

  • Abducens Nerve (VI): Controls the lateral rectus muscle, responsible for moving the eye outward.

  • Facial Nerve (VII): Controls the muscles of facial expression and conveys taste sensations from the anterior two-thirds of the tongue.

  • Vestibulocochlear Nerve (VIII): Responsible for hearing and balance.

  • Glossopharyngeal Nerve (IX): Involved in taste from the posterior one-third of the tongue and swallowing.

  • Vagus Nerve (X): Controls functions of the heart, lungs, and digestive tract; involved in autonomic control.

  • Accessory Nerve (XI): Controls shoulder and neck muscles.

  • Hypoglossal Nerve (XII): Controls the muscles of the tongue.

Spinal Nerves

• Definition: Spinal nerves are a set of 31 pairs of nerves that emerge from the spinal cord. Each spinal nerve is formed by the combination of motor and sensory fibers.

• Function: They transmit sensory information from the body to the CNS and motor commands from the CNS to the body. Each spinal nerve innervates a specific region of the body.

• Regions: The spinal nerves are categorized based on their location along the spinal column:

  • Cervical Nerves (C1-C8): 8 pairs, innervating the neck, shoulders, arms, and hands.

  • Thoracic Nerves (T1-T12): 12 pairs, innervating the upper back, chest, and abdomen.

  • Lumbar Nerves (L1-L5): 5 pairs, innervating the lower back, hips, and legs.

  • Sacral Nerves (S1-S5): 5 pairs, innervating the pelvis, buttocks, and legs.

  • Coccygeal Nerve (Co1): 1 pair, innervating the skin over the coccyx.

Summary

• Cranial Nerves: 12 pairs that primarily serve the head and neck, responsible for sensory and motor functions.

• Spinal Nerves: 31 pairs that emerge from the spinal cord, responsible for transmitting sensory and motor information throughout the body.

Both cranial and spinal nerves are crucial for communication between the CNS and the peripheral body, enabling sensory perception, motor control, and various autonomic functions.

Nervous System Components

The nervous system is divided into several components, with the somatic nervous system (SNS) and the autonomic nervous system (ANS) being two key divisions of the peripheral nervous system (PNS). Here’s a detailed overview of each:

Somatic Nervous System (SNS)

• Definition: The somatic nervous system is responsible for voluntary movements and the transmission of sensory information to the central nervous system (CNS) from the external environment.

• Components:

  • Motor Neurons: These neurons carry signals from the CNS to skeletal muscles, enabling voluntary movements such as walking, talking, and other physical activities.

  • Sensory Neurons: These neurons transmit sensory information (such as touch, pain, temperature, and proprioception) from sensory receptors in the skin, muscles, and joints to the CNS.

• Function:

  • Controls voluntary movements of skeletal muscles.

  • Processes sensory information from the body’s surface and musculoskeletal system.

  • Involved in reflex actions (e.g., the knee-jerk reflex), which are rapid, involuntary responses to stimuli.

Autonomic Nervous System (ANS)

• Definition: The autonomic nervous system regulates involuntary bodily functions, including heart rate, blood pressure, respiration, digestion, and sexual arousal. It operates without conscious control.

• Components: The ANS is further divided into three main branches:

  • Sympathetic Nervous System:

    • Prepares the body for "fight or flight" responses during stressful situations.

    • Increases heart rate, dilates airways, inhibits digestion, and mobilizes energy stores.

    • Activates the adrenal glands to release adrenaline (epinephrine) and norepinephrine.

  • Parasympathetic Nervous System:

    • Promotes "rest and digest" activities, conserving energy and maintaining homeostasis.

    • Decreases heart rate, constricts airways, stimulates digestion, and promotes relaxation.

    • Often counteracts the sympathetic responses.

  • Enteric Nervous System:

    • Sometimes considered a part of the ANS, this system governs the function of the gastrointestinal tract.

    • Controls processes such as peristalsis and the secretion of digestive enzymes, operating independently but can be influenced by the sympathetic and parasympathetic systems.

• Function:

  • Regulates involuntary bodily functions essential for survival.

  • Maintains homeostasis by balancing the sympathetic and parasympathetic responses based on the body’s needs.

Summary

• Somatic Nervous System (SNS):Controls voluntary movements and processes sensory information from the external environment.Involves motor and sensory neurons.

• Autonomic Nervous System (ANS):Regulates involuntary bodily functions and maintains homeostasis.Divided into the sympathetic (fight or flight), parasympathetic (rest and digest), and enteric (gastrointestinal) systems.

Both systems work together to ensure that the body responds appropriately to internal and external stimuli, balancing voluntary and involuntary activities for overall health and function.

Surface Features of the Brain

The surface features of the brain are crucial for understanding its structure and function. These features include various folds, grooves, and regions that contribute to the brain's overall organization. Here’s a detailed explanation of the key surface features:

Gyri (Singular: Gyrus)

• Definition: Gyri are the raised, convoluted ridges on the surface of the brain.

• Function: They increase the surface area of the cerebral cortex, allowing for a greater number of neurons and enhancing cognitive functions such as thinking, memory, and decision-making.

• Examples:

  • Precentral Gyrus: Located in the frontal lobe, it is the primary motor cortex responsible for voluntary movement.

  • Postcentral Gyrus: Located in the parietal lobe, it is the primary somatosensory cortex responsible for processing sensory information from the body.

Sulci (Singular: Sulcus)

• Definition: Sulci are the shallow grooves or indentations that separate the gyri.

• Function: Sulci also contribute to increasing the surface area of the brain and help define the boundaries of different brain regions.

• Examples:

  • Central Sulcus: Separates the frontal lobe from the parietal lobe; it runs from the top of the brain down toward the lateral sulcus.

  • Lateral Sulcus (Sylvian Fissure): Separates the temporal lobe from the frontal and parietal lobes.

Fissures

• Definition: Fissures are deeper grooves that separate large regions of the brain.

• Function: They serve as significant landmarks for identifying major brain areas.

• Examples:

  • Longitudinal Fissure: Divides the brain into the left and right hemispheres.

  • Transverse Fissure: Separates the cerebrum from the cerebellum.

Lobes of the Brain

The brain is divided into four main lobes, each associated with different functions:

• Frontal Lobe: Located at the front of the brain; involved in reasoning, planning, problem-solving, emotional regulation, and voluntary movement.

• Parietal Lobe: Located at the top of the brain; processes sensory information related to touch, temperature, pain, and spatial awareness.

• Temporal Lobe: Located on the sides of the brain; involved in auditory processing, memory, and language comprehension.

• Occipital Lobe: Located at the back of the brain; primarily responsible for visual processing.

Other Surface Features

• Cerebellar Surface: The cerebellum has its own gyri and sulci, which are smaller and more densely packed than those in the cerebrum. The cerebellum is involved in coordination and balance.

• Meningeal Layers: While not strictly a surface feature of the brain itself, the brain is covered by protective membranes called meninges (dura mater, arachnoid mater, and pia mater), which provide additional protection and support.

Summary

The surface features of the brain, including gyri, sulci, and fissures, play a vital role in increasing the surface area of the cerebral cortex, facilitating complex cognitive functions, and helping to delineate different functional areas of the brain. Understanding these features is essential for studying brain anatomy and its relationship to behavior and cognition.