Nervous System Anatomy and Physiology

• The material relates to the anatomy, and physiology of the nervous system and the senses, with a focus on common pathologies

Chapter 1: Practical Introduction and Contextualization

• Many bodily functions depend on receiving stimuli and generating responses, all require a coordination system
• The body has two coordinating systems: the endocrine system and the nervous system
• The nervous system enables fast and precise communication between the organism and the external environment

Chapter 2: General Information about the Nervous System and Neurons

• The nervous system communicates through physicochemical signals
• Neurons: the basic structural and functional unit of the nervous system
• Neurons specialize in integrating information from sensory receptors or other neurons
• Neurons transmit information to other neurons or effector organs through the process of synapse and nerve impulses
• Neurons have distinct parts:
• Soma (cell body): contains the cytoplasm, nucleus, Nissl bodies, cytoskeleton, mitochondria, Golgi apparatus, and endoplasmic reticulum
• Dendrites: cytoplasmic extensions covered by the cell membrane, possess microtubules, and form the grey matter with the soma
• Axon: a longer extension from the soma that is surrounded by an axolemma, which may or may not be covered by Schwann cells (glial cells in the peripheral nervous system) to form a myelin sheath
• Myelin sheaths facilitate nerve impulse transmission
• A collection of axons is known as white matter
• Synaptic terminal occurs at the end of the axon and divides into terminal buttons that form synapses with adjacent neurons, glands, or muscle cells and store neurotransmitters that transmit nerve impulses
• Neurons are classified into three types based on their function:
• Sensory (afferent): responsible for transporting information from receptors to the central nervous system (CNS)
• Motor (efferent): conduct responses from the central nervous system to the effector organs
• Association: located entirely in the central nervous system and connect neurons to each other
• Neurons possess polarity where they can be unipolar, bipolar, pseudounipolar, and multipolar

Nerve Impulses and Synapses

• Neurons are the only cells capable of generating and transmitting electrical impulses
• These cells and their extensions form a network to connect and communicate with each other
• Neuronal communication happens through nerve impulses, which move in one direction within a neuron from the grey matter to the axon's synaptic terminal
• Myelin sheathing increases the speed of nerve impulse transmission
• A neurotransmitter is released at the end of the axon, and it transits signal to another cell
• Neurotransmitters travel through the synaptic cleft (space between the axon terminals of one neuron and the dendrites of another) to the next neuron, where specific receptors bind to them
• Synapse: the communicative process which involves neurotransmitters between the end of one neuron and the somatic part of the next neuron, allowing nerve impulses to be transmitted from one neuron to another
• Presynaptic Neurons: Neurons secrete neurotransmitters
• Postsynaptic Neurons: Neurons that receive those neurotransmitters
• Presynaptic vesicles accumulate in the terminal buttons, contain neurotransmitters, and are secreted into the synaptic cleft through exocytosis
• The vesicles merge with the membrane of the terminal buttons
• The released neurotransmitters are captured by the receptors on the dendrites of the next neuron, allowing it to receive and transform information
• Amount of neurotransmitters released depends on the amount of information to be transmitted
• Synapses only proceed in one direction since presynaptic vesicles accumulate only in the final part of the axon, transferring information solely to the cell it is connected to

Chapter 3: The Central Nervous System

• The nervous system divides into the central nervous system (CNS) and peripheral nervous system (SNP) anatomically
• The peripheral (SNP) connects the CNS to the rest of the body
• The central nervous system (CNS) divides into the brain and spinal cord
• The brain is located within the skull and is the main coordination and integration center of the nervous system. It is divided into:
• Cerebrum: contains the cerebral cortex (spherical with folds called convolutions, grooves called sulci, and deeper fissures) and the diencephalon (located centrally and contains the thalamus, hypothalamus, and pituitary gland)
• Brainstem: located immediately below the cerebrum and contains three structures
• Midbrain: involved in muscle coordination, vision, hearing, and general alertness
• Pons: connects and transmits sensory information from the brain to the cerebellum
• Medulla oblongata: controls cardiac, respiratory, and vasoconstrictor activity and vomiting, with lesions being incompatible with life
• Cerebellum: lies behind the brainstem and coordinates movements and maintains normal postures
• Spinal cord: a cylinder inside the vertebral column that transmits nerve impulses from the periphery to the brain and from the brain to the effector organs
• It plays an important role in producing reflexes

Protection of the Central Nervous System

• The CNS is protected by the skin, bones, and:
• Meninges: membranes that cover the brain and spinal cord, consisting of the dura mater (outermost, thick, and strong), arachnoid (intermediate with a spider web appearance), and pia mater (innermost and in contact with the nervous tissue)
• Cerebrospinal fluid: a fluid alike blood plasma which provides nutrients and acts as a shock absorber that flows between the arachnoid and pia mater
• Blood-brain barrier: a layer of endothelial cells that cover the capillaries that irrigate the brain and serves as a filter for substances passing from the blood to the brain

Peripheral Nervous System (PNS)

• The Peripheral Nervous System (PNS) is a part of the nervous system that connects the CNS to the rest of the organism made up of nerves (bundles of axons) and ganglia (clusters of neuronal bodies)
• Peripheral nerves are of two types:
• Cranial nerves (12 pairs) exiting from lower underside of the brain
• Spinal nerves (31 pairs) which exit both sides of the vertebral column
• Two components from the PNS depend on its functions:
  • Autonomic or vegetative nervous system: regulate the activity of internal organs and homeostasis
  • Somatic or voluntary nervous system (SNS): establishes the connection between the receptors, the central nervous system, and the effectors

Chapter 4: Coordination and Regulation of the Body

• The nervous system generates instantaneous responses to external or internal stimuli, to facilitate adaptation from changes in the environment
• Coordination between the nervous, muscular, and skeletal systems and the sensory organs involves acting mechanisms:
• Stimuli are signals that trigger a reaction and are captured by sensory organs, which transform stimuli into nerve impulses
• The impulses transmit information and travel through the afferent pathways to the integration center (central nervous system)
• After this is established, the effector triggers a response
• The response travels to the effectors (muscular, skeletal, or endocrine system)
• Reflexes: involuntary, rapid, and automatic action
• The information only reaches the spinal cord, and the response is generated automatically
• Coordination occurs differently, determined by the type of stimuli received (negative or positive) and exterior or interior
• Regulation involves mechanisms of positive and negative feedback to maintain internal balance

Chapter 5: Neurological Pathophysiology

• The nervous system is susceptible to pathologies that alter function
• Neurological disorders involve disruptions in system structures or chemical imbalances like neurotransmitter deficiencies
• Tumors, circulatory lesions, infections, and traumas promote neurological diseases
• Neurological pathologies have unique symptoms related to the affected structure
• Affected areas may include the central or peripheral nervous system

Common Signs and Symptoms of Neurological Disorders

• Headaches: migrainous or tension-related
• Seizures: sudden, spontaneous episodes mostly caused by epilepsy marked by convulsions
• Loss of Strength or Movement: caused by circulatory disorders, inflammation of the muscles, or nerve damage
• Sensory Disorders: with symptoms like numbness or tingling in the extremities, which are often related to neurological conditions

Section 5.1 Neurological and Mental Illnesses

• Associated with the system differentiate between degenerative, mental, and others
• Degenerative: incurable diseases because of the destruction of nervous system structures
• Alzheimer's: causes loss of memory and mental capacities due to cognitive deterioration and the destruction of cerebral cortex neurons
• Parkinson's: triggered by dopamine secretion deficits, leading to slow movements, rigidity, tremors, and loss of postural control, system also brings pain, depression, and altered autonomic system
• Multiple sclerosis: autoimmune disease triggers demyelination of the axons -Amyotrophic lateral sclerosis (ALS): activity among motor neurons decreases
• Mental: disorders, chronic or not, sometimes have genetic influences and affect by drug use. Treatments exist
• Schizophrenia: uncoordinated behaviors among actions and thoughts
• Neurosis: due to distortion
• Bulimia and Anorexia: eating disorders that are physical
• Depression: feeling of dejection, guilt, unhappiness -Meningitis: inflammation of the meninges
• Poliomyelitis: caused by a virus
• Epilepsy: seizures
• The patient suffers conditions of a period of time
• Narcolepsy: the brain unable to regulate the cycles of sleep and wake

Chapter 6: Anatomy and Physiology of the Senses

• Sensory organs receive external stimuli and enable the organism to interact with its environment
• The senses: sight, hearing, taste, touch, and smell each develop in distinct anatomical structures
• Sight involves the eye or eyeball, made up of three layers:
• Sclera: the transparent area on the exterior white part is the cornea.
• Choroid: is a middle layer of ocular tissue possesses a dark pigment inside that stops light rays.
• Ciliar Body: structures regulate the degree and support

Olfaction, Taste, and Touch

• Olfaction detects and processes odors, performed by the olfactory receptors in the yellow pituitary
• The receptors are stimulated by chemical substances in the air and odors diffuse and reach with the olfactory, specific receptors which transform the chemical process with signals and send those to the anterior region
• The receptors weaken in process with the sensitivity
• Taste senses substances through gustatory receptors located on the papillae
• Taste involves combining primary sensations, such as sweet, bitter, sour, salty, and umami
• Chemicals trigger neurotransmitters which produce electrical impulses
• Touch can be perceived through the skin, which transforms stimuli and this is interpreted by the brain

Chapter 7: Case Study 1 - The Sense of Hearing

• The anatomy and physiology of the ear has three parts:
• Outer Ear: gathers sound toward the inner ear
• Middle Ear: transmits to the inner ear
• The eardrum, eardrum, conducts medium and inner ear canal,
• The fluid functions as support for cells
• Cochlea: important organ and processes
• Inner Ear: made up of hollow that form in membranous

Pathologies Associated With the Senses

• Taste, sight,touch can all suffer from alterations that affect their functions
• Ageusia: alteration of taste either diminished or distorted
• Anosmia: the loss of smell
• There are sight alterations that can cause pathologies, which can affect the function of the eyes -Astigmatism: curvature of the lens
  • Daltonism: doesn't distinguish colors from light
  • Hypermetropia: vision loss
  • Myopia: focusing for people and also affected
  • Ceguera: blindness
  • Psioriasis: non-contagious
• Otitis for infection and other diseases that can affect sound and hearing
• Other disease
• -Rinitis
• • Vertigo
• • Glaucoma

Avoiding Health Problems

• Following helpful habits for the health and wellbeing of people is essential
• To help exercise memory through reading
• A great idea to help the mind to stop against premature aging
• Eat fruits and vegetables to help the mind
• Sociability and to have good system
• To avoid and stop negative thinking from psychological problems in the health
• To avoid drugs and alcohol from the mind
• It has been studied that you can help the health using these methods

Explore the nervous system's role in stimulus response and coordination with the endocrine system. Learn about neurons as the fundamental units, their communication via physicochemical signals, and the functions of soma, cytoplasm, and nucleus.