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• Chapter 2.2 covers the anatomy of the nervous system.

Standard Anatomical Position

• Refers to a specific body orientation
• The orientation is used when describing an individual's anatomy
• The body stands upright, facing forward, legs parallel, upper limbs at sides, palms forward

Planes of the Body

• Imaginary reference points divide the body into sections for anatomical description
• Sagittal plane divides the body into right and left parts
• Coronal plane divides the body into anterior and posterior parts
• Transverse plane divides the body into superior and inferior parts

Nervous System

• Coordinates all activities of the body
• Enables the body to respond and adapt to changes

Cells of the Nervous System: Neurons

• Specialized cells for reception, conduction, and transmission of electrochemical signals

External Anatomy of Neurons

• Nucleus contains the cell's genetic material
• Cell body (soma) provides energy, maintains structure, and contains genetic information
• Dendrites are projections from the cell body that receive information from other neurons
• Axon is a long, thin nerve fiber that transmits electrical impulses away from a neuron's cell body
• Myelin sheath is a fatty layer that surrounds and insulates nerve cells
• Node of Ranvier are gaps in the myelin sheath that regenerate action potentials along axons
• Speeds up communication via rapid voltage change across cell membrane
• Axon terminal are the ends of axons which transmit messages to other cells by releasing neurotransmitters at synapses

Classes of Neurons

• Unipolar neuron has one process extending from its cell body, found in invertebrate glands and muscles
• Pseudo-unipolar neuron's nerve process splits into two branches or axons; sensory neuron
• Bipolar neuron has two distinct structures extending from the cell body: one axon and one dendrite; found in olfactory epithelium, retina, and certain nerves within the ear
• Multipolar neuron has more than two processes extending from its cell body; it is present throughout the CNS, including the brain and associated nerves in the autonomic nervous system

Glial Cells

• Found throughout the nervous system
• They surround neurons and provide support and insulation
• Glial cells are the most abundant cell types in the central nervous system

Types of Glial Cells

• Oligodendrocytes provide support and insulation to axons in the central nervous system
• Schwann cells in the peripheral nervous system produce the myelin sheath around neuronal axons and guide axonal regeneration after damage
• Respond to injury or disease by multiplying, engulfing cellular debris, and triggering inflammatory responses
• Astrocytes cover the outer surfaces of blood vessels that course through the brain and play a role in allowing the passage of some chemicals from blood into the CNS while blocking others

General Layout of the Nervous System

• The main components are the central nervous system, spinal cord, brain, somatic nervous system, peripheral nervous system, and autonomic nervous system
• Within the autonomic system are the afferent and efferent nerves; the nervous system consists of the sympathetic and parasympathetic systems

Two Divisions of CNS

• The Central Nervous System (CNS) is located within the skull and spine
• Integrates and controls the nervous system
• The brain as part of the CNS is located in the skull and controls major body functions
• It is the organ inside the head that controls thought, memory, feelings, and activity

Five Major Divisions of the Brain

• The five major divisions of the brain are the forebrain, midbrain, and hindbrain,
• Hindbrain controls vital functions like breathing, heartbeat, and motor coordination

Myelencephalon (Medulla)

• It is the most posterior division of the brain
• It is largely composed of tracts carrying signals between the rest of the brain and the body
• The Medulla Oblongata helps control vital processes like heartbeat, breathing, and blood pressure

Metencephalon

• Part of the hindbrain
• It differentiates into the pons and the cerebellum
• Pons is involved in the control of breathing, communication between different parts of the brain, and sensations such as hearing, taste, and balance
• Cerebellum receives information from the sensory systems, the spinal cord, and other parts of the brain and regulates motor movements

Midbrain (Mesencephalon)

• The midbrain is a small but important part of the brain
• Connects the forebrain and hindbrain
• It is a portion of the central nervous system associated with vision, hearing, motor control, and sleep/wake, arousal and temperature regulation

Two Divisions of Mesencephalon

• Tectum is the dorsal (top) part of the midbrain
• Inferior colliculi are involved in auditory processing
• Superior colliculi are involved in visual function and control of eye movements
• Tegmentum is the division of the mesencephalon ventral (lower) to the tectum; it promotes cardiorespiratory functions and airway-protective reflexes

Forebrain

• Controls body temperature and reproductive functions
• Also controls eating, sleeping, and the display of emotions

Diencephalon

• Situated between the telencephalon and the midbrain
• It is composed of two structures: the thalamus and hypothalamus

Thalamus

• Large mass of grey matter in the dorsal part of the diencephalon of the brain
• Relays motor and sensory signals to the cerebral cortex
• Regulates sleep, alertness, and wakefulness

Hypothalamus

• Exerts effects in part by regulating the release of hormones from the pituitary gland
• Plays an important role in the regulation of several motivated behaviors (e.g., eating, sleep, and sexual behavior)

Telencephalon (Cerebrum)

• Largest division of the human brain.
• Responsible for the integration of complex sensory and neural functions
• The telencephalon controls the initiation and coordination of voluntary activity in the body

Frontal Lobe

• The frontal lobes make up the largest part of the cortex
• Their central functions are to process information related to memory, planning, decision making, goal setting, and creativity
• Contains the primary motor cortex that regulates muscular movements

Temporal Lobe

• Located on the side of the cerebrum
• Responsible for processing auditory information

Parietal Lobe

• Located at the top of the brain in the cerebrum
• Responsible for the sense of touch
• Helps to determine body position and integrate visual information
• Has anterior (front) and posterior (rear) sections

Occipital Lobe

• Primarily concerned with processing visual information
• The occipital lobe is the visual cortex
• Is the outermost layer of the brain containing gray matter
• Responsible for many higher order functions like language and information processing

The Limbic System and the Basal Ganglia

• Limbic System is involved in the regulation of motivated and emotional behaviors
• The limbic system process your memory, thoughts and motivations, then tell your body how to respond
• Amygdala is involved in the control of emotion, survival instincts, and memory, function is to assess the harmfulness of sensory inputs
• Hippocampus is the brain structure responsible for memory of the immediate past
• Fornix is a C-shaped bundle of nerve fibers acting as the major output tract of the hippocampus
• Damage to the fornix has been associated with anterograde amnesia, which is the inability to create new memories
• Cingulate cortex is involved in processing emotions and behavior regulation and helps to regulate autonomic motor function
• Septum is a wall or membrane that separates two spaces or masses of soft tissue (hippocampus and hypothalamus)

Basal Ganglia

• Primarily responsible for motor control, motor learning, executive functions and behaviors, and emotions
• Caudate nucleus (tail-like and C-shaped) processes visual information, movement, and memory
• Putamen (outer part of the nucleus of the brain) is involved in motor learning, speech articulation, language functions, reward, cognitive functioning, and addiction
• Striatum makes decisions functions such as motor control, emotion, habit formation, and reward
• Globus pallidus controls conscious and proprioceptive (body's ability to sense movement, action, and location)

Spinal Cord

• Long, thin bundle of nervous tissue and support cells connected to the brain and located along your back and neck, and it transmits electric signals
• Protected by the vertebrae and cerebral spinal fluid
• Cervical consists of the first seven vertebrae which provides supports for the head and protects the spinal cord
• Thoracic is the middle section; it starts at the base of the neck and ends at the bottom of your ribs

Spinal Cord Anatomy

• Lumbar consists of the five vertebrae in your lower back which allows for a wide range of motions
• Sacrum has five segments fused together into one large bone; that control sensation to the crotch area
• Gray matter is a tissue in the brain and spinal cord that processes and interprets information; and it plays a significant role in mental functions
• White matter connects regions that send and receive signals, affecting the ability to focus and learn and affecting the ability to solve problems

Meninges, Ventricles, and Cerebrospinal Fluid

• Three layers of meninges are layers of tough and connective tissue that protect and cover the brain and spinal cord
  • Dura mater is the thickest and outermost of the three meninges
  • Arachnoid mater (spider-web like membrane) that is filled with cerebrospinal fluid
  • Pia mater is the meningeal envelope that firmly adheres to the surface
• Cerebral ventricles are the four large internal chambers of the brain that produce, transport and remove of cerebrospinal fluid

Central Nervous System

• Central canal, also known as ependymal canal, is the cerebrospinal fluid-filled space
• Cerebrospinal fluid (CSF) can be found in the brain and spinal cord
• Blood-brain barrier is composed of tightly packed cells of the brain's blood vessel walls and it impedes the passage of many toxic substances from the blood into the brain

Peripheral Nervous System

• The PNS contains all the nerves that lie outside of the central nervous system (CNS) and connects the CNS to the organs, limbs, and skin

Two Divisions of PNS

• Somatic Nervous System (SNS) called "Voluntary" is based on the Greek word soma which means "body"
• Afferent nerves (sensory neurons) carry sensory signals
• Autonomic Nervous System (ANS) called "Involuntary" regulates the body's internal environment by efferent nerves that carry signals to internal organs

Efferent Nerves Under ANS

• Sympathetic Nervous System (makes you alert) whose autonomic motor nerves project from the CNS and regulates the flight or fight responses
• Parasympathetic Nervous System (makes you calm); those autonomic motor nerves that project from the brain and spinal cord and regulates the rest or digest

Functions of Sympathetic and Parasympathetic Systems

• Sympathetic System stimulates, organize, and mobilize energy resources in threatening situations and show psychological arousal
• Parasympathetic Systems conserve energy and is indicative of psychological relaxation