Combo with Anatomy Chapter 16 Spinal Cord and Spinal Nerves and 2 others

Ganglion

Cluster of neuron cell bodies within the PNS

Somatic Motor

Component of Motor Nervous System. Conducts nerve impulses from the CNS to the skeletal muscles, causing them to contract. Voluntary.

Autonomic Motor

Component of Motor Nervous System. Innervates internal organs and regulates smooth muscle, cardiac muscle, and glands without our control. Also known as visceral motor system or involuntary motor system.

Wernicke Area

Functional Brain region Typically located in the left hemisphere involved in recognizing, understanding, and comprehending spoken and written language.

Gliomas

Glial cell tumor can be benign and slow-growing or malignant

CN IX

Glossopharyngeal Sensory Function: Touch and taste of posterior one-third of tongue, visceral sensory from carotid bodies Somatic Motor Function: Stylopharyngeus Parasympathetic Motor (autonomic) Function: Increases secretion from parotid salivary gland

Subarachnoid Space

Immediately deep to the arachnoid mater Arachnoid trabeculae extend through this space from the arachnoid mater to the underlying pia mater.

Motor nuclei

In the anterior and lateral horns contain motor neuron cell bodies that send nerve impulses to muscles and glands.

Autonomic motor nuclei

In the lateral horns innervate smooth muscle, cardiac muscle, and glands.

Cerebral Nuclei

Paired, irregular masses of gray matter buried deep within the central white matter in the basal region of the cerebral hemispheres inferior to the floor of the lateral ventricle. Components: Caudate Nucleus- C-shaped. when one walks, the neurons in this nucleus stimulate the appropriate muscles to produce pattern and rhythm of arm and leg movements associated with walking. Amygdaloid Body-Participates in the expression of emotions, control of behavioral activities, and development of moods. Putamen and globus pallidus- combine to form a larger body, the lentiform nucleus. Functions in controlling muscular movement at the subconscious level. Claustrum- Processes visual information at a subconscious level.

Vermis

Part of Cerebellum Separates the left and right cerebellar hemispheres Receives sensory input reporting torso position and balance. Its output to the vestibular nucleus helps maintain balance.

Anterior Group

Thalamic Nuclei Changes motor cortex excitability and modifies mood

Chromatophillic/Nissl

two types of Ribosomes, stain darkly with basic dyes which causes the grey color of the gray matter due to large collections in an area

Sensory Homunulus

May be traced on the postcentral gyrus surface.

converging circuit

nerve impulses converge at a single postsynaptic neuron

Autonomic Centers of the medulla oblongata

Cardiac center: Heart rate and strength of contracrion Vasomotor center: Blood pressure Respiratory Center: Respiratory rate Other nuclei: coughing, sneezing, salivating, swallowing, gagging, and vomiting.

CNS Synapse

Consists of the close association of a presynaptic neuron and a postsynaptic neuron at a region where their plasma membranes are separated by a very narrow space called the synaptic cleft.

Arcuate Nucleus

Hypothalamic Nuclei Regulates appetite, release of gonadotropin-releasing hormone, release of growth hormone-releasing hormone, and release of prolactin-inhibiting hormone

Suprachiasmatic Nucleus

Hypothalamic Nuclei Regulates sleep-wake (circadian) rhythm

Visual Association area

Located in the occipital lobe and surrounds the primary visual area Enables us to process visual information by analyzing color, movement, and form, and to use this information to identify things we see.

Somatosensory Association area

Located in the parietal lobe interprets sensory information and is responsible for integrating and interpreting sensations to determine the texture, temperature, pressure, and shape of objects. Allows us to identify objects with our eyes closed.

Sensory nuclei

Located in the posterior horns within the nuclei, contains interneuron cell bodies

Filum terminale

Located within the cauda equina A thin strand of pia mater that helps anchor the conus medullaris to the coccyx

Auditory Association area

Located within the temporal lobe interpret the characteristics of sound and store memories of sounds heard in the past.

Long Thoracic

Smaller branches of the brachial plexus Anterior rami: C5-C7 Motor innervation: Serratus anterior

Thoracodorsal

Smaller branches of the brachial plexus Anterior rami: C6-C8 Motor innervation: Latissimus dorsi

Medial cutaneous nerve of arm

Smaller branches of the brachial plexus Anterior rami: C8-T1 Cutaneous innervation: Medial side of arm

Medial cutaneous nerve of forearm

Smaller branches of the brachial plexus Anterior rami: C8-T1 Cutaneous innervation: Medial side of forearm

Medial Pectoral

Smaller branches of the brachial plexus Anterior rami: C8-T1 Motor innervation: Pectoralis major, minor

Diaphragma sellae

Smallest of the dural septa Forms a "roof" over the sella turcica of the sphenoid bone. A small opening within it allows for the passage of a thin stalk, called the infundibulum, that attaches the pituitary gland to the base of the hypothalamus.

Cords

Structure of the brachial plexuses Upon reaching the axilla, the anterior and posterior divisions converge to form three cords, which are named in respect to their position near the axillary artery. Posterior cord: Posterior to the axillary artery and is formed by the posterior divisions of the superior, middle, and inferior trunks. It contains portions of C5-T1 nerves. Medial cord: Medial to the axillary artery. Formed by the anterior division of the inferior trunk; it contains portions of nerves C8-T1. Lateral cord: Lateral to the axillary artery. Formed from the anterior divisions of the superior and middle trunks. Contains portions of nerves C5-C7.

Saltatory Conductions Continuous Conductions

process where nerve impulse "jumps" from node to node In unmyelinated axon, nerve impulse must travel entire length of axon. Requires more energy.

Cranial Nerves

Are part of the PNS and originate on the inferior surface of the brain. 12 of them

Reflexes

Are rapid, automatic, involuntary reactions of muscles or glands to a stimulus. They all similar properties: -A stimulus is required to initiate a response to sensory input. -A rapid response requires that a few neurons be involved and synaptic delay be minimal. -An automatic response occurs the same way every time. -An involuntary response requires no intent or pre-awareness of the reflex activity. It is a survival mechanism; it allows us to quickly respond to a stimulus that may be detrimental to our well-being without having to wait for the brain to process the information.

Motor Speech area

(Broca area) Located within the inferolateral portion of the left frontal love. Responsible for controlling the muscular movements necessary for vocalization.

Motor Nervous System

(Efferent = conducting outward) Responsible for transmitting motor impulses from the CNS to muscles or glands. The motor nervous system is responsible for output. Contains both CNS and PNS components: Parts of the brain and spinal cord (CNS) initiate nerve impulses, which travel through motor nerves that in turn transmit these impulses to effector organs.

Sensory Nervous System

(Afferent = inflowing) -Responsible for receiving information from receptors and transmitting this information to the CNS. -It is responsible for input. -Contains both PNS and CNS components: nerves of the PNS transmit the sensory information, and certain parts of the brain and spinal cord in the CNS interpret this information. -Has two components: Somatic Sensory and Visceral Sensory.

Lateral Group

Controls sensory flow to parietal loves and emotional information to cingulate gyrus.

Anterior Rootlets

Arise from the spinal cord and merge to form a single anterior root, which contains motor axons only. These motor axons arise from cell bodies in the anterior and lateral horns of the spinal cord.

Neurons

Basic structural unit of the nervous system. Conduct nerve impulses from one part of the body to another. Characteristics: -High metabolic rate (need a lot of O2 and Glucose) -Extreme longevity (can last a life time) -Nonmitotic (during development, mitotic activity is lost)

Subdural Space

Between the arachnoid mater and the overlying dura mater is a potential space called subdural space. Becomes an actual space if blood or fluid accumulates there, a condition called subdural hematoma.

Primary Brain Vesicles

By the fourth week of development, the three primary brain vesicles have formed. These eventually give rise to all the different regions of the adult brain. Prosencephalon Mesencephalon Rhombencephalon

Peripheral nervous system (PNS)

Composed of the cranial nerves (nerves that extend from the brain), spinal nerves (nerves that extend from the spinal cord), and ganglia (clusters of neuron cell bodies located outside the CNS). Structural Organization

Tract

CNS axon bundle in which the axons have a similar function and share a common origin and destination.

Posterior

Directional term Refers to Caudal (toward the tail)

Subarachnoid mater

Deep to the arachnoid mater A real space filled with CSF

Pia mater

Deep to the subarachnoid space, is a delicate, innermost menigeal layer composed of elastic and collagen fibers. This meninx directly adheres to the spinal cord and supports some of the blood vessels supplying the spinal cord.

Fissures

Deeper grooves in the brain.

Myelencephalon

Derives from the rhombencephalon, and it eventually forms the medulla oblongata.

White Matter

Derives its color from the myelin in the myelinated axons. Lies below (deep) to the gray matter of the cortex.

Referred visceral pain

Dermatomes are also involved in referred visceral pain, a phenomenon in which pain or discomfort from one organ is mistakenly referred to a dermatome. Pain in a dermatome may arise from an organ nowhere near the dermatome.

Thalamic nuclei

Each part of the thalamus is a gray matter mass composed of about a dozen major thalamic nuclei that are organized into groups; axons from these nuclei project to particular regions of the cerebral cortex. Sensory impulses from all the conscious senses except olfaction converge on the thalamus and synapse in at least one of its nuclei.

Cerebral hemisphere

Either of two symmetrical halves of the cerebrum, separated by the longitudinal fissure.

Association Areas

Either process and interpret incoming data or coordinate a motor response. Integrate new sensory inputs with memories of past experiences

Prosencephalon

Forebrain

Somatic motor nuclei

In the anterior horns innervate skeletal muscle

Mesencephalon

Midbrain

Nerve Plexus

Network of nerves in PNS

Perikaryon

Neuron. The cytoplasm within the cell body is called perikaryon.

Somatic sensory nuclei

Receive information from sensory receptors, such as pain or pressure receptors in the skin.

Medial Group

Sends signals about conscious awareness of emotional states to frontal lobe.

Functional Classifications of neurons

Sensory Motor Interneuron

Terminal Branches

Structure of the brachial plexuses The five major terminal branches emerge from the three cords: Axillary, median, musculocutaneous, radial, and ulnar nerves.

Myelin Sheath

The insulating covering around the axon consisting of concentric layers of myelin. Mainly consists of the plasma membrane of glial cells (oligodendrocytes and neurolemmocyte) and contains large proportion of fats and a lesser amount of proteins. The high lipid content gives the axon a distinct, glossy-white appearance.

Mesencephalon

The only primary vesicle that does not form a new secondary vesicle.

Telencephalon

Arises from the prosencephalon and eventually forms the cerebrum.

Preoptic Area

Hypothalamic Nuceli "Thermostat" (regulates body temperature)

Ventromedial nucleus

Hypothalamic Nuclei "Satiety center" (produces hunger sensations)

Rhombencephalon

Hindbrain

Diencephalon

Arises from the prosencephalon and eventually forms the thalamus, hypothalamus, and epithalamus.

Metencephalon

Arises from the rhombencephalon and eventually forms the pons and cerebellum.

Anterior Nucleus

Hypothalamic Nuclei "Thirst Center" (stimulates fluid intake); autonomic control center

Mammillary Body

Hypothalamic Nuclei Processes sensations related to smelling

Paraventricular Nucleus

Hypothalamic Nuclei Produces oxytocin and antidiuretic hormone (ADH)

Supraoptic Nucleus

Hypothalamic Nuclei Produces oxytocin and antidiuretic hormone (ADH)

Gray commissure

A horizontal bar of gray matter that surrounds a narrow central canal. It primarily contains unmyelinated axons and serves as a communication route between the right and left sides of the gray matter.

Functions of Hypothalamus

-Master control of autonomic nervous system (influences heart rate, blood pressure, digestive activities, and respiration) -Master control of the endocrine system (secretes hormones that control secretory activities in the anterior pituitary gland) -Regulation of body temperature (shivering and sweating) -Control of emotional behavior (Pleasure, aggression, fear, rage, contentment, and the sex drive) -Control of food intake (Monitors nutrients and produces sensations of hunger) -Control of water intake (Monitor blood solute concentrations) -Regulation of sleep-wake (circadian) rhythms

Reflex Testing in a Clinical Setting

-Testing reflexes can be used to test specific muscle groups and specific spinal nerves or segments of the spinal cord. -Hypoactive reflex: reflex response is diminished or absent May indicate damage to a segment of the sc May indicate muscle disease or damage to a neuromuscular junction -Hyperactive reflex: Reflex response is abnormally strong May indicate damage somewhere in the brain or spinal cord

CSF Circulation

1. CSF is produced by choroid plexus in each ventricle 2. CSF flows from lateral ventricles and 3rd ventricle through the cerebral aqueduct into the 4th ventricle. 3. CSF in 4th flows into subarachnoid space by passing through openings in the roof of the 4th ventricle. These openings are the paired lateral apertures and the single median aperture. CSF also fills the central canal of the spinal cord. 4. As it travels through the subarachnoid space, CSF removes waste products and provides buoyancy for the brain and spinal cord. 5.CSF accumulates w/i the suarachnoid space, it exerts pressure w/i the arachnoid villi. This pressure exceeds the pressure in the venous sinuses. Thus, the arachnoid villi extending into the dural venous sinuses provide a conduit for a one-way flow of excess CSF to be returned into the blood within the dural venous sinuses.

Brain structures associated with the Limbic System

1. Cingulate Gyrus: receives input from the other components of the limbic system. Focuses attention on emotionally significant events and appears to bring them into consciousness. 2. Parahippocampal gyrus: Associated with the hippocampus 3. Hippocampus: Essential in storing memories and forming long-term memory. 4. Amygdaloid body: Involved in several aspects of emotion, especially fear. Can help store and code memories based on how a person emotionally perceives them- ex. as related to feat, extreme happiness, or sadness. 5. Olfactory bulbs, olfactory tracts, olfactory cortex: emotions with odors. 6. Fornix: connects hippocampus with diencephalon 7. Anterior thalamic nuclei, habenular nuclei, septal nuclei, and mammillary bodies: contribute to overall function of limbic system.

Conduction of a nerve impulse from the presynaptic neuron to the postsynaptic neuron

1. Nerve impulse travels through the axon and reaches its synaptic knob. 2. This causes an increase in Ca2+ movement into the synaptic knob through voltage-gated calcium ion channels in the membrane. 3. This causes synaptic vesicles to move to and bind to the inside surface of the membrane; neurotransmitter molecules within the synaptic vesicles are released into the synaptic cleft by exocytosis. 4. Neurotransmitter molecules diffuse across the synaptic cleft to the plasma membrane of the postsynaptic cell. 5. NT mole. attach to specific protein receptors in the plasma mem. of the postsynaptic cell, causing ion gates to opne. 6. Influx of NA+ moves into the postsynaptic cell through the open gate, affecting the charge across the mem. 7. Change in the postsynaptic cell voltage causes a nerve impulse to begin in the postsynaptic cell. 8. Enzyme AChE resides in the synaptic cleft and rapidly breaks down molecules of ACh that are released into the synaptic cleft. Thus, AChE is needed to that ACh wil not continuously stimulate the postsynaptic cell.

Myelination of PNS Axons

1. Neurolemmocyte starts to wrap around a portion of an axon. 2. Neurolemmocyte cytoplasm and plasma membrane begin to form consecutive layers around axon. 3. The overlapping inner layers of the neurolemmocyte plasma membrane form the myelin sheath. 4. Eventually, the neurolemmocyte cytoplasm and nucleus are pushed to the periphery of the cell as the myelin sheath is formed.

Nerve

A cablelike bundle of parallel axons. Has three successive CT wrappings: endoneurium, Perineurium, and Epineurium.

Cerebrospinal Fluid (CSF)

A clear, colorless liquid that circulates in the ventricles and subarachnoid space. Bathes the exposed areas of the CNS and completely surrounds the brain and spinal Cord. Functions: Buoyancy- without CSF, the brain would sink through the foramen magnum. Protection- Cushions, asks as a "movement buffer" Environmental stability- Transports nutrients and chemicals to the brain and removes waste products from the brain.

Arachnoid sudural space

A narrow space that separates the dura mater from the arachnoid mater. Found only in tissue preparations, and in life it is merely a potential space.

Nerve Plexus

A network of interweaving anterior rami of spinal nerves. The anterior rami of most spinal nerves form nerve plexuses on both the right and left sides of the body These nerve plexuses then split into multiple "named" nerves that innervate various body structures. The principal plexuses are the cervical plexuses, brachial plexuses, and lumbar plexuses, and sacral plexuses.

Ipsilateral

A reflex arch may be ipsilateral or contralateral. When both the receptor and effector organs of the flex are on the same side of the spinal cord. Ex. left arm contracts to pull your left hand away from a hot object.

Contralateral

A reflex arch may be ipsilateral or contralateral. When the sensory impulses from a receptor organ cross over through the spinal cord to activate effector organs in the opposite limb. Ex. A contralateral effect occurs when you step on a sharp object with your left foot and then contract the muscles in your right leg to maintain balance as you withdraw your left leg from the damaging object.

Polysynaptic Reflexes

A reflex may be monosynaptic or polysynaptic. Have more complex neural pathways that exhibit a number of synapses involving interneurons within this reflex arc. Because this reflex arc has more components, there is a more prolonged delay between stimulus and response. Ex. The crossed-extensor reflex, which is the reflex that supports postural muscle activity when you withdraw your foot from a painful stimulus. Enables you to balance for example.

Monosynaptic Reflexes

A reflex may be monosynaptic or polysynaptic. The simplest of all reflexes. Sensory axons synapse directly on the motor neurons, whose axons project to the effector. Interneurons are not involved in processing this reflex. Very minor synaptic delay is incurred in the single synapse of this reflex arc, resulting in a very prompt reflex response. Ex. The patellar (knee-jerk) reflex.

Lumbar Part

A shorter segment of the spinal cord Contains neurons for the lumbar spinal nerves

Dermatome

A specific segment of the skin supplied by a single spinal nerve. All spinal nerves except C1 innervate a segment if skin, and so each of these nerves is associated with a dermatome. The skin of the body may be divided into sensory segments that collectively make up a dermatome map. Clinically important because they can indicate potential damage to one or more spinal nerves.

Golgi Tendon Reflex

A spinal reflex A polysynaptic reflex that prevents skeletal muscles from tensing excessively. Golgi tendon organs are nerve endings located within tendons near a muscle-tendon junction. As a muscle contracts, force exerted on its associated tendon, resulting in increased tension in the tendon and activation of the Golgi tendon organ. Nerve impulses in the Golgi tendon organ signals interneurons in the spinal cord, which in turn inhibit the actions of the motor neurons. When the motor neurons that cause the muscle contraction are inhibited, the associated muscle is allowed to relax, thus protecting the muscle and tendon from excessive tension damage.

CN VI

Abducens Sensory Function: NONE Somatic Motor Function: Lateral rectus eye muscle Parasympathetic Motor (autonomic) Function: NONE

CN XI

Accessory Sensory Function: NONE Somatic Motor Function: Trapezius muscle, sternocleidomastoid muscle Parasympathetic Motor (autonomic) Function: NONE

Anterior Ramus

After leaving the intervertebral foramen, a typical spinal nerve almost immediately splits into branches, termed rami. The larger of the two main branches. This splits into multiple other branches, which innervate the anterior and lateral portions of the trunk, the upper limbs, and the lower limbs. Many of the anterior rami go on to form nerve plexuses. Additional rami, called the rami communicantes, are also associated with spinal nerves. These rami contain axons associated with the autonomic nervous system. Each set of rami eommunicantes extends between the spinal nerve and a ball-like structure called the sympathetic trunk ganglion. These ganglia are interconnected and form a beaded necklace-like structure called the sympathetic trunk.

Posterior Ramus

After leaving the intervertebral foramen, a typical spinal nerve almost immediately splits into branches, termed rami. The smaller of the two main branches. Innervates the deep muscle of the back and the skin of the back.

Epineurium

All of the fascicles are bundles together by a superficial CT covering called epineurium. This thick layer of dense irregular CT encloses the entire nerve, providing both support and protection to the fascicles within the layer.

Nerve Impulse

Also called action potential it is the rapid movement of an electrical charge along a axon's plasma membrane.

Sensory Neurons

Also known as afferent neurons. Transmit nerve impluses from sensory receptors to the CNS. Specialized to detect changes in their environment called stimuli. This can be in the form of touch, pressure, heat, light, or chemicals. Most are unipolar, the rest are bipolar (olfactory/retina). The cell bodies are located outside the CNS and housed within structures called posterior (dorsal) root ganglia.

Motor Neurons

Also known as efferent neurons. Transmit nerve impulses from the CNS to muscles or glands. Most of them extend to muscle cells, and the nerve impulses they transmit cause these cells to contract. The muscle and gland cells that receive nerve impulses from motor neurons are called effectors, because their stimulation produces a response or effect. The cell bodies of most motor neurons lie in the spinal cord, whereas the axons primarily travel in cranial or spinal nerves to muscles and glands. All are multipolar.

Glial Cells

Also known as neuroglia. Occur within both CNS and PNS. Differ from neurons in that they are smaller and capable of mitosis. Do not transmit nerve impulses. They protect and nourish neurons. They provide an organized, supporting framework for all nervous tissue. Outnumber neurons. Astrocytes, ependymal cells, microglial cells, and oligodendrocytes.

Endoneurium

An individual Axon in a myelinated neuron is surrounded by neurolemmocytes and then wrapped in the endoneurium, a delicate layer of areolar CT that separates and electrically isolates each axon. Also within this layer are capillaries that supply each axon.

Hypothalamus

Anterionferior region of the diencephalon A thin, stalklike infundibulum extends inferiorly from the hypothalamus to attach the pituitary gland.

Structure of brachial plexus

Anterior rami (also called roots): The continuations of the anterior rami of the spinal nerves C5-T1. These rami emerge from the intervertebral foramina and travel through the neck. Trunks: The five roots unite to form the superior (C5, C6), middle (C7), and inferior trunks (C8 and T1) in the posterior triangle of the neck. Divisions: Portions of each trunk divide inferior to the clavicle into an anterior division and a posterior division, which primarily contains axons that innervate the anterior and posterior parts of the upper limb, respectively.

Nerve

Axon bundles extending through the PNS

Synapses

Axons terminate as they contact other neurons, muscle cells, or gland cells at specialized junctions called synapses where the nerve impulse is transmitted to the other cell. As the axon approaches the cell onto which it will terminate, it generally branches repeatedly into several telodendria, and each telodendrion loses its myelin covering. The endings usually form swellings called synaptic knobs at the ends of the axon branches.

Axillary Nerve

C5, C6 Terminal Branch of the brachial plexus Traverses through the axilla and posterior to the surgical neck of the humerus. Emerges from the posterior cord. Innervates both the deltoid and the teres minor muscle. Receives information from the superolateral part of the arm.

Musculocutaneous Nerve

C5-C7 Terminal Branch of the brachial plexus Arises from the lateral cord of the brachial plexus. Innervates the anterior arm muscles (coracobrachialis, biceps brachii, and brachialis), which flex the humerus and flex the forearm.

Radial Nerve

C5-T1 Terminal Branch of the brachial plexus Arises from the posterior cord of the brachial plexus. Travels along the posterior side of the arm and then along the radial side of the forearm. Innervates the posterior arm muscles (forearm extensors) and the posterior forearm muscles (extensors of the wrist and digits and the supinator of the forearm). Receives sensory information from the posterior arm and forearm surface and the dorsolateral side of the hand.

Median Nerve

C5-T1 Terminal Branch of the brachial plexus Formed from branches of the medial and lateral cords of the brachial plexus. Travels along the midline of the arm and forearm, and deep to the carpal tunnel in the wrist. Innervates most of the anterior forearm muscles, the thenar muscles, and the lateral two lumbricals. Receives sensory information from the palmar side of the lateral 3-1/2 fingers (thumb, index finger, and the lateral half of the ring finger) and from the dorsal tips if these same fingers.

Ulnar Nerve

C8-T1 Terminal Branch of the brachial plexus Arises from the medial cord of the brachial plexus and descends along the medial side of the arm. It wraps posterior to the medial epicondyle of the humerus and then runs along the ulnar side of the forearm. Innervates some of the anterior forearm muscles (the median region of the flexor digitorium profundus and all of the flexor carpi ulnaris). Innervates most of the intrinsic hand muscles, including the hypothenar muscles, the palmar and dorsal interossei, and the medial two lumbricals. Receives sensations from the skin of the dorsal and palmar aspects of the medial 1-1/2 fingers (the little finger and the medial half of the ring finger).

Difference between myelin sheaths in CNS and PNS

CNS: Oligodendrocytes can myelinate many axons, not just one. Cytoplasmic extensions wrap successively around a portion of each axon, and successive plasma membrane layers form the myelin sheath. PNS: Neurolemmocytes can myelinate a portion of a single axon only. Multiple neurolemmocytes on one axon.

Brain Ventricles

Cavities or expansions within the brain that are derived from the lumen (openings) of the embryonic neural tube. They are continuous with one another as well as with the central canal of the spinal cord. Contains CSF

Nucleus

Center in the CNS that displays discrete anatomic boundaries.

Pathway

Centers and tracts that connect the CNS with body organs and systems.

Gray matter

Centrally located Resembles a letter H or a butterfly Subdivided into anterior horns, lateral horn, posterior horns, and they gray commissure.

Biceps Reflex

Clinically important reflexes. Spinal nerve segments tested: C5, C6 Normal Action of Effector: Flexes elbow when biceps brachii tendon is tapped

Triceps Reflex

Clinically important reflexes. Spinal nerve segments tested: C6, C7 Normal Action of Effector: Extends elbow when triceps brachii is tapped.

Cremasteric Reflex

Clinically important reflexes. Spinal nerve segments tested: L1, L2 Normal Action of Effector: Elevates testis (due to contraction of cremaster muscle in scrotum) when medial side of thigh is briskly stroked.

Patellar (knee-jerk) Reflex

Clinically important reflexes. Spinal nerve segments tested: L2-L4 Normal Action of Effector: Extends knee when patellar ligament is tapped.

Plantar Reflex

Clinically important reflexes. Spinal nerve segments tested: L5, S1 Normal Action of Effector: Plantar flexes foot; flexes toes when plantar side of foot is briskly stroked.

Ankle (Archilles) Reflex

Clinically important reflexes. Spinal nerve segments tested: S1, S2 Normal Action of Effector: Plantar flexes ankle when calcaneal tendon is tapped.

Abdominal Reflexes

Clinically important reflexes. Spinal nerve segments tested: T8-T12 Normal Action of Effector: Contract abdominal muscles when one side of the abdominal wall is briskly stroked.

Brainstem

Connects the prosencephalon and cerebellum to the spinal cord. Three regions: superiorly placed mesencephalon, the pons, and the inferiorly placed medulla oblongata. It is a bidirectional passageway for all tracts extending between the cerebrum and the spinal cord.

Somatic Sensory

Component of Sensory Nervous System. General somatic senses: touch, pain, pressure, vibration, temperature, and proprioception (sensing the position or movement of joints and limbs)- and the special senses: taste, vision, hearing, balance, and smell. Voluntary control.

Visceral Sensory

Component of Sensory Nervous System. Transmit nerve impulses from blood vessels and viscera to the CNS. The visceral senses primarily include temperature and stretch (of muscles of the organ wall). Involuntary control.

Central nervous system (CNS)

Composed of the brain and spinal cord. The brain is protected and enclosed within the skull. The spinal cord is housed and protected within the vertebral column. Structural Organization

Anterior funiculus

Composed of tracts of white matter that occupy the space on each anterior side of the cord between the anterior gray horns and the anterior median fissure; the anterior funiculi are interconnected by the white commissure.

Association tracts

Connect different regions of the cerebral cortex within the same hemisphere. Short association tracts are composed of arcuate fibers; they connect neighboring gyri within the same lobe. Longer association tracts are composed of longitudinal fasciculi; connect gyri in different lobes of the same hemisphere.

Spinal nerves

Connect the CNS to muscles, glands, and receptors. Contains three types of successive CT wrappings: endoneurium, perineurium, and epineurium. Motor axons in a spinal nerve originate from the spinalcord. Contains both motor axons (from the anterior root) and sensory axons (from the posterior root).

Transverse cervical nerve

Cutaneous branches of the cervical plexus C2, C3 Innervation: Skin on anterior part of neck

Greater auricular nerve

Cutaneous branches of the cervical plexus C2, C3 Innervation: Skin on ear; CT capsule covering parotid gland

Supraclavicular nerves

Cutaneous branches of the cervical plexus C3, C4 Innervation: Skin on superior part of chest and shoulder

Lesser occipital nerve

Cutaneous branches of the cervical plexus C2 Innervation: Skin of scalp superior and posterior to ear

Anterior

Directional term Refers to Rostral (toward the nose)

Pineal Gland

Endocrine gland Part of epithalamus Secretes hormone melatonin- which appears to help regulate day-night cycles known as circadian rhythm.

Posterior Rootlets

Enter the posterior aspect of the spinal cord. These rootlets were derived from a single posterior root, which contains sensory axons only. The cell bodies of these sensory neurons are located in a posterior root ganglion, which is attached to the posterior root.

Commissural Tracts

Extend between the cerebral hemispheres through axonal bridges called commissures. The prominent commissural tracts that link the left and right cerebral hemispheres include the large, C-Shaped corpus callosum and the smaller anterior and posterior commissures.

Falx cerebelli

Extending into the midsagittal line inferior to the tentorium cerebelli is the falx cerebelli, a sickle-shaped vertical partition that divides the left and right cerebral hemispheres. A tiny occipital sinus runs in its posterior vertical border.

Lumbosacral enlargement

Extends through the lumbar and sacral parts of the spinal cord and innervates the lower limbs

Dura Mater

External tough, dense irregular CT layer composed of two fibrous layers. Meningeal layer lies deep to the periosteal layer. Periosteal layer is the most superficial layer, forms the periosteum on the internal surface of the cranial bones.

CN VII

Facial Sensory Function: Taste from anterior two-thirds of tongue Somatic Motor Function: Muscles of facial expression, digastric (posterior belly), stylohyoid, Stapedius Parasympathetic Motor (autonomic) Function: Increases secretion from lacrimal gland of eye, submandibular and sublingual salivary glands.

Gnostic Area

Functional Brain Region Located in regions of the parietal, occipital, and temporal lobes Integrates all sensory, visual, and auditory information being processed by the association areas within these lobes.

Five secondary brain vesicles

Five weeks of development Three primary vesicles gives rise to five secondary vesicles. Telencephalon Diencephalon Mesencephalon Metencephalon Myelencephalon

CSF Formation

Formed by choroid plexus in each ventricle Choroid plexus is composed of a layer of ependymal cells and the capillaries that lie within the pia mater. Produced by secretion of a fluid from the ependymal cells that originates from the blood plasma. Similar to blood plasma, although certain ion concentrations differ between the two types of fluid.

Lumbar Plexuses

Formed from the anterior rami of spinal nerves L1-L4 located to the L1-L4 vertebrae and along the psoas major muscle in the posterior abdominal wall. It is subdivided into an anterior division and a posterior division.

Sacral Plexuses

Formed from the anterior rami of spinal nerves L4-S4 and are located immediately inferior to the lumbar plexuses. The lumbar and sacral plexuses are sometimes considered together as the lumbosacral plexus. The nerves emerging from a sacral plexus innervate the gluteal region, pelvis, perineum, posterior thigh, and almost all of the leg and foot. The anterior rami organize themselves into an anterior division and a posterior division. The nerves arising from the anterior division tend to innervate muscles that flex (or plantar flex) parts of the lower limb, while the posterior division nerves tend to innervate muscles that extend (or dorsiflex) part of the lower limb.

Pons

Forms part of the mesencephalon Housed within the Pons are the sensory and motor tracts that connect to the brain and spinal cord. The middle cerebellar peduncles are transverse groups of fibers that connect the pons to the cerebellum. Houses CN V, CN VI, CN VII, some of CN VIII

Epithalamus

Forms the posterior roof of the diencephalon and covers the 3rd ventricle. Posterior portion houses the pineal gland and the habenular nuclei.

Lateral horns

Found in the T1-L2 parts of the spinal cord Contain cell bodies of autonomic motor neurons, which innervate cardiac muscle, smooth muscle, and glands.

Center

Group of CNS neuron cell bodies with a common function.

Funiculus

Group of tracts in a specific area of the spinal cord

Perineurium

Groups of axons are wrapped into separate bundles called fascicles by a cellular dense irregular CT layer called perineurium. This layer supports blood vessels supplying the capillaries within the endoneurium.

Fascicles

Groups of axons are wrapped into separate bundles called fascicles.

Tentorium cerebelli

Horizontally oriented fold of dura mater that separates the occipital and temporal lobes of the cerebrum from the cerebellum. Transverse sinuses run within its posterior border. Tentorial notch- gap in anterior surface, allows for passage of brainstem.

Unipolar Neurons

Have a single, short neuron process that emerges from the cell body and branches like a T. Found in spinal region Most sensory neurons of the PNS are unipolar. The combined peripheral process (from dendrites o the cell body) and central process (from the cell body into the CNS) together denote the axon, because these processes generate and conduct impulses and are often myelinated.

Bipolar Neurons

Have two neuron processes that extend from the cell body-one axon and one dendrite. Relatively uncommon in humans and primarily limited to special senses. Ex. Located in the olfactory epithelium of the nose and in the retina of the eye.

CN XII

Hypoglossal Sensory Function: NONE Somatic Motor Function: Intrinsic tongue muscles and extrinsic tongue muslces Parasympathetic Motor (autonomic) Function: NONE

Motor Areas of Cerebrum

Housed in the frontal lobe Primary motor cortex: located within the precental gyrus of frontal lobe. Controls skeletal muscle activity. Left controls the right skeletal muscles and vice versa.

Primary Somatosensory cortex

Housed within the postcentral gyrus of the parietal lobes. Neurons in this cortex receive general somatic sensory information from touch, pressure, pain, and temperature receptors.

Gray Matter

Houses motor neuron and interneuron cell bodies, dendrites, telodendria, and unmyelinated axons. Forms the cortex that covers the surface of most of the adult brain.

Autonomic respiratory centers

In the pons Pseumotaxic center Apneustic center They regulate the rate and depth of breathing, and both of them influence and modify the activity of the respiratory center in the medulla oblongata.

Superior Olivary Complex

In the pons located in the inferior pons Receives auditory input and is involved in the pathway for sound localization

Cauda equina

Inferior to conus medullaris a group of axons project inferiorly from the spinal cord

Pia Mater

Innermost layer Thin layer of areolar CT Highly vascularized Tightly adheres to the brain

Premotor Cortex

Located in the frontal lobe Permits us to process motor information and is primarily responsible for coordinating learned, skilled motor activities, such as moving the eyes in a coordinated fashion.

Common Fibular Nerve

L4-S2 Nerve of the sacral plexus Formed from the posterior division of the sciatic nerve As the common fibular division of the sciatic nerve, it supplies the short head of the biceps femoris muscle. Along the lateral knee, as it wraps around the neck of the fibula, this nerve splits into two main branches: The deep fibular nerve and the superficial fibular nerve.

Cervical enlargement

Located in the inferior cervical part of the spinal cord Contains neurons that innervate the upper limbs

Interneurons

Known as association neurons. Lies entirely within the CNS. Multipolar Receive nerve impulses from many other neurons and carry out integrative function of the nervous system. They retrieve, process, and store information and "decide" how the body responds to stimuli. They facilitate communication between sensory and motor neurons. Interneurons outnumber all other neurons in both their total number and different types; it is estimated that 99% of our neurons are interneurons.

Ilioinguinal

L1 Smaller branches of the lumbar plexus Partial innervation to abdominal muscles Cutaneous innervation to the inferior abdominal wall and scrotum in males or labia majora in females

Iliohypogastric

L1 Smaller branches of the lumbar plexus Partial innervation to abdominal muscles Cutaneous innervation to the superior lateral gluteal region. Inferior abdominal wall.

Gentiofemoral

L1, L2 Smaller branches of the lumbar plexus Cutaneous innervation to the small area in anterior superior thigh. Scrotum in males or labia majora in females.

Lateral Femoral Cutaneous

L2, L3 Smaller branches of the lumbar plexus Cutaneous Innervation of the anterolateral thigh.

Obturator Nerve

L2-L4 Main nerve of the anterior division. Travels through the obturator foramen to the medical thigh. There, the nerve innervates the medial thigh muscles (which adduct the thigh) and receives sensory information from the superomedial skin of the thigh. Smaller branches of each lumbar plexus innervate the abdominal wall, the scrotum and the labia, and the inferior portions of the abdominal muscles.

Femoral Nerve

L2-L4 Main nerve of the posterior division of the lumbar plexus. Supplies the anterior thigh muscles, such as the quadriceps femoris (knee extensor) and the the sartorius and iliopsoas (hip flexors). Receives sensory information from the anterior and inferomedial thigh as well as the medial aspect of the leg.

Deep Fibular Nerve

L4-S1 Nerve of the sacral plexus Travels in the anterior compartment of the leg and terminates between the first and second toes. Supplies the anterior leg muscles (which dorsiflex the foot and extend the toes) and the muscles on the dorsum of the foot (which extend the toes). This nerve receives sensory innervation from the skin between the first and second toes on the dorsum of the foot.

Primary Gustatory Cortex

Located in the insula Involved in processing taste information

Tibial Nerve

L4-S3 Nerve of the sacral plexus Formed from the anterior divisions of the sciatic nerve. In the posterior thigh, the tibial division of the sciatic nerve innervates the hamstrings (except the short head of the biceps femoris) and the hamstring part of the adductor magnus. Travels in the posterior compartment of the leg, where it supplies the plantar flexors of the foot and the toe flexors. In the foot, the tibial nerve splits into the lateral and medial plantar nerves, which innervate the plantar muscles of the foot and conduct sensory impulses from the skin covering the sole of the foot.

Sciatic Nerve

L4-S3 Nerve of the sacral plexus. Largest and longest nerve in the body Projects from the pelvis through the greater sciatic notch of the os coxae and extends into the posterior region of the thigh. Composed of two divisions wrapped in a common sheath; the tibial division and the common fibular division. Just superior to the popliteal fossa, the two divisions of the sciatic nerve split into two nerves: the tibial nerve and the common fibular nerve.

Superficial Fibular Nerve

L5-S2 Nerve of the sacral plexus Travels in the lateral compartment of the leg Just proximal to the ankle, this nerve becomes superficial along the anterior part of the ankle and dorsum of the foot. The superficial fibular nerve innervates the lateral compartment muscles of the leg (foot evertors and weak plantar flexors). Conducts sensory information from most of the dorsal surface of the foot and the anterioinferior part of the leg.

Falx cerebri

Largest of the four dural septa Sickle shape, vertical fold of dura mater Located in midsagittal plane, projects into the longitudinal fissure between the left and right cerebral hemispheres. Running within the margins of this dural septa are two dural venous sinuses: superior sagittal sinus and the inferior sagittal sinus.

Posterior Group

Lateral geniculate nuclei: Relay visual information from optic tract to visual cortex and midbrain. Medial geniculate nuclei: Relay auditory information from inner ear to auditory cortex Pulvinar Nuclei: Integrate and relay sensory information for projection to association areas of cerebral cortex.

Satellite Cell

Located in PNS Flattened cell clustered around neuronal cell bodies in a ganglion (a collection of neuron cell bodies located outside of the CNS). Functions: Protects and regulates nutrients for cell bodies in ganglia.

Primary Olfactory cortex

Located in temporal lobe Provides conscious awareness of smells

Primary auditory cortex

Located in temporal lobe Receives and processes incoming visual information

Axoaxonic Synapse

Least common synapse Far less understood Occurs between the synaptic knob of a presynaptic neuron and the synaptic knob of a postsynaptic neuron. The action of this synapse appears to influence the activity of the synaptic knob.

Cerebral Hemispheres

Left and right Separated by the longitudinal fissure that extends along the midsagittal plane. Separated from one another, except at a few locations where bundles of axons called tracts form white matter regions that allow for communication between them. The largest one is the corpus callosum. This provides the main communications like between these hemispheres.

Anterior horns

Left and right anterior masses Primarily houses the cell bodies of somatic motor neurons, which innervate skeletal muscle.

Posterior horns

Left and right posterior masses of gray matter. The axons of sensory neurons and the cell bodies of interneurons are located in this region.

Epidural Space

Lies between the dura mater and the periosteum covering the inner walls of the vertebra, and houses areolar CT, blood vessels, and adipose CT. * Epidural anesthetic is given here.

Posterior funiculus

Lies between the posterior gray horns on the posterior side of the cord and the posterior median sulcus.

Dura mater

Lies deep to the epidural space Most external of the meninges Spinal dura mater has only one meningeal layer, whereas the cranial dura mater has two. Provides stability to the spinal cord At each intervertebral foramen, the dura mater extends between adjacent vertebrae and fuses with the CT layers that surround the spinal nerves.

Central White Matter

Lies deep to the gray matter of the cerebral cortex and is composed primarily of myelinated axons. Most of the axons are grouped into bundles called tracts, or projection tracts.

Arachnoid Mater

Lies external to the pia mater Composed of delicate web of collagen and elastic fibers, termed arachnoid trabeculae.

Thoracic Part

Lies inferior to the cervical part Contains the neurons for the thoracic spinal nerves

Sacral Part

Lies inferior to the lumbar part and contains the neurons for the sacral spinal nerves

Flocculonodular lobes

Life anterior and inferior to each cerebellar hemisphere

Projection Tracts

Link the cerebral cortex to the inferior brain regions and the spinal cord. The packed group of axons in these tracts passing to and from the cortex between the cerebral nuclei is called internal capsule.

Fourth ventricle

Located between the pons/medulla and the cerebellum. Narrows at its inferior end before it merges with the slender central canal in the spinal cord. Contains CSF

Cervical Plexuses

Located deep on each side of the neck, immediately lateral to cervical vertebrae. C1-C4. They are formed primarily by the anterior rami of spinal nerves C1-C4. The fifth cervical spinal nerve is not considered part of the cervical plexus, although it contributes some axons to one of the plexus branches. Branches of the cervical plexuses innervate anterior neck muscles as well as the skin of the neck and portions of the head and shoulders.

Astrocyte

Located in CNS Large cell with numerous cell processes In contact with neurons and capillaries Most common type of glial cell Functions: Helps for blood-brain barrier Regulates tissue fluid composition Provides structural support and organization to CNS Replaces damaged neurons Assists with neuronal development

Ependymal Cell

Located in CNS Simple cuboidal epithelial cell lining cavities in brain and spinal cord. Cilia on apical surface Functions: Lines ventricles of brain and central canal of spinal cord Assists in production and circulation of CSF They work together with nearby capillaries to form a network called choroid plexus, which produces CSF.

Microglial Cell

Located in CNS Small cell with slender branches from cell body Least common type of glial cell Functions: Wanders through CNS and replicate in response to an infection Defends against pathogens Removes Debris Phagocytizes waste

Oligodendrocyte

Located in CNS Rounded, bulbous cell with slender cytoplasmic extensions Extensions wrap around CNS axons Functions: Myelinates and insulates CNS axons (myelin sheath) Allows faster nerve impulse conduction through the axon

Neurolemmocyte (Schwann Cell)

Located in PNS Flattened cell wrapped around a portion of an axon in the PNS Functions: Myelinates and insulates PNS axons Allows for faster nerve impulse conduction through the axon

Primary Visual Cortex

Located in the occipital lobe Receives and processes incoming visual information

Olive

Medulla oblongata Contains a large fold of gray matter called the inferior olivary nucleus. Relay ascending sensory impulses, especially prorioceptive information, to the cerebellum.

Nucleus cuneatus and Nucleus gracilis

Medulla oblongata Relay somatic sensory information to the thalamus Nucleus cuneatus: Receives posterior root fibers corresponding to sensory innervation from the arm and hand of the same side. Nucleus gracilis: Receives posterior root fibers carrying sensory information from the leg and lower limbs of the same side.

Decussarion pyramids

Medulla oblongata In the posterior region of the medulla, most of these axons cross to the opposite side of the brain at a point called the decussation of the pyramids. As a result of the crossover, each cerebral hemisphere controls the voluntary movements of the opposite side of the body.

Medial Lemniscus

Medulla oblongata Projects through the brainstem to the ventral posterior nucleus of the thalamus

Axodendritic Synapse

Most common type Occurs between the synaptic knobs of a presynaptic neuron and the dendrites of the postsynaptic neuron. Occur either on the expanded tips of narrow dendritic spines or on the shaft of the dendrite.

Multipolar Neurons

Most common type of neuron. Multiple neuron processes- many dendrites and a single axon extend from the cell body. Ex. Include motor neurons that innervate muscle and glands. Makes up majority of the neurons in body

Coccygeal Part

Most inferior "tip" of the spinal cord One pair of coccygeal spinal nerves arises from this region

Chemical Synapses

Most numerous type of synapse Facilitates most of the interactions between neurons and all communications between neurons and effectors. The presynaptic membrane releases a signaling molecule called a neurotransmitter. Acetylcholine (ACh) is most common type of neurotransmitter.

Ansa Cervicalis Nerve

Motor branch of the cervical plexus Consists of: Superior root: C1, C2 Inferior root: C3, C4 Innervation: Geniohyoid; infrahyoid muscles (omohyoid, sternohyoid, sternothyroid, and thyrohyoid)

Segmental branches

Motor branches of cervical plexus C1-C4 Innervation: Anterior and middle scalenes

Nervous Tissue

Nervous system is composed of all tissue types, but primarily of nervous tissue- neurons and glial cells.

Blood-Brain Barrier (BBB)

Nervous tissue is protected from the general circulation by the BBB, which strictly regulates what substances can enter the interstitial fluid of the brain. Keeps the neurons in the brain from being exposed to drugs, waste products in the blood,and variations in levels of normal substances (e.g. ions, hormones) that could adversely affect brain function. Astrocytes contribute to the BBB by using their perivascular feet to cover and wrap around the capillaries in the brain. Controlling what goes in and out of them. BBB is reduced or missing in the choroid plexus, hypothalamus, and the pineal gland due to permeability and hormones.

Brachial Plexuses

Networks of nerves that supply the upper limb. Each is formed by the anterior rami of spinal nerves C5-T1. The component of the brachial plexus extend laterally from the neck, pass superior to the first rib, and then continue into the axilla. Each innervates the pectoral girdle and the entire upper limb of one side.

Axon Collateral

Neuron. Axon may give rise to a few side branches called axon collaterals. Most axons and their collaterals branch extensively at their distal end into an array of fine terminal extensions called telodendria, or axon terminals.

Cell Body

Neuron. Also called soma. The neuron's control center and is responsible for receiving, integrating, and sending nerve impulses. Enclosed by a plasma membrane and contains cytoplasm surrounding a nucleus. The nucleus contains a prominent nucleolus, reflecting the high metabolic activity of neurons. Many mitochondria are present. Also large amounts of free ribosomes.

Telodendria

Neuron. Axon terminals.

Neurofilaments

Neuron. Intermediate filaments that aggregate to form bundles called neurofibrils. Neurofibrils extend as a complex network into both dendrites and axons, where their tensile strength provides support for these processes.

Anaxonic

Neuron. Neuron that has no axon. Small neurons that provide no clues to distingush axon from dendrite; they are only found in CNS; they are uncommon and their function is unknown.

Dendrites

Neuron. Tend to be shorter, smaller processes that branch off the cell body. Some neurons only have one dendrite, while others have many. They conduct nerve impulses toward the cell body for precessing. The more dendrites a neuron has, the more nerve impulses that neuron can receive from other cells.

Axon Hillock

Neuron. The axon connects to the cell body at a triangular region called the axon hillock. The axon hillock is devoid of chromatophilic substance, and so it lacks those dark staining regions when viewed under the microscope.

Axon

Neuron. Typically longer nerve cell process emanating from the cell body. Sometimes called a nerve fiber. Neurons either have one axon or no axon at all, those that do not have one is called anaxonic. The axon transmits a nerve impulse away from the cell body toward another cell. The axon transmits output information to other cells.

Unmyelinated Axons

Not all axons are myelinated. Can be found in PNS and CNS In PNS: Associated with a neurolemmocyte, but no myelin sheath covers them. Axon rests in a portion of the neurolemmocyte rather than being wrapped by successive layers of plasma membrane. In CNS: unmyelinated axons are not associated with oligodendrocytes.

Axosomatic Synapse

Occurs between synaptic knobs and the cell body of the postsynaptic neuron.

CN III

Oculomotor Sensory Function: NONE Somatic Motor Function: Four extrinsic eye muscles (medial rectus, superior rectus, inferior rectus, inferior oblique) Levator palpebrae superioris muscle (elevates eyelid) Parasympathetic Motor (autonomic) Function: Innervates sphincter pupillae muscle in eye to make pupil constrict; contracts ciliary muscles to make lens of eye more rounded (as needed for near vision)

CN I

Olfactory Sensory Function: Olfaction (smell) Somatic Motor Function: NONE Parasympathetic Motor (autonomic) Function: NONE

Phrenic Nerve

One important branch of the cervical plexus is the phrenic nerve, which is formed primarily from the C4 nerve and some contributing axons from C3 and C5. Travels through the thoracic cavity to innervate the diaphragm.

CN II

Optic Sensory Function: Vision Somatic Motor Function: NONE Parasympathetic Motor (autonomic) Function: NONE

Cortex

Outer layer of gray matter in cerebrum and cerebellum; consists of densely packed neuron cell bodies.

Denticulate Ligaments

Paired, lateral triangular extensions of the spinal pia mater that attach to the dura mater. They help suspend and anchor the spinal cord laterally to the dura mater.

Medulla Oblongata

Part of brainstem Formed from the myelencephalon Continuous with the spinal cord All communication b/w the brain and the spinal cord involves tracts that ascend or descend through the medulla oblongata. Associated with CN VIII, CN IX, CN X, CN XI, CN XII

Substantia nigra

Part of brainstem/mesencephalon Almost black in appearance, due to melanin Houses clusters of neurons that produce the neurotransmitter dopamine, which affects the brain processes that control movement, emotional response, and ability to experience pleasure and pain.

Tectum

Part of brainstem/mesencephalon Contains pairs of sensory nuclei, the superior and inferior colliculi, which are called the tectal plate. They are relay stations in the processing pathway of visual and auditory sensations. Superior colliculi: "visual reflex centers" help visually track moving objects and control reflexes such as turning the eye and head in response to a visual stimulus. Inferior colliculi: "Auditory reflex centers" control reflexive turning of the head and eyes in the direction of sound.

Tegmentum

Part of brainstem/mesencephalon Contains pigmented red nuclei and the reticular formation. The reddish color of the nuclei is due to both blood vessel density and iron pigmentation in the neuronal cell bodies. Integrates information from the cerebrum and cerebellum and issues voluntary motor commands to the erector spinae muscles of the back to help maintain posture while standing, bending the waist, or walking.

Cerebral Puduncles

Part of brainstem/mesencephalon Located on the anterolateral surfaces of the mesencephalon. Somatic motor axons descend from the primary motor cortex, through these peduncles, to the spinal cord.

Habenular nuclei

Part of epithalamus Help relay signals from the limbic system to the mesencephalon and are involved in visceral and emotional responses to odors.

Cerebral aqueduct

Part of the brainstem/mesencephalon Extends through the mesencephalon, which connects the 3rd and 4th ventricles; it is surrounded by a region called the periaqueductal gray matter.

Insula

Primary gustatory cortex Functions: Interpretation of taste; memory Located deep to the lateral sulcus

Spinal Cord Meninges

Protects and encapsulates the spinal cord Continuous with the cranial meninges Spaces between some of the meninges have clinical significance. Outermost to innermost: vertebra, epidural space, dura mater, subdural space, arachoid mater, subarachnoid space, and pia mater.

Temporal Lobe

Primary auditory cortex Primary olfactory cortex Auditory association area Olfactory association area Part of Wernicke area Part of gnostic area Functions: Interpretation of auditory and olfactory sensations; storage of auditory and olfactory experiences; understanding speech.

Frontal Lobe

Primary motor cortex (located within precentral gyrus) Premotor cortex Motor speech area (Broca area) (usually found only on the left frontal lobe) Frontal eye fields Functions: Higher intellectual functions (concentration, decision making, planning); personality; verbal communication; voluntary motor control of skeletal muscles. Central sulcus separates frontal from parietal lobes Lateral sulcus separates frontal and parietal lobes from the temporal lobe

Parietal Lobe

Primary somatosensory cortex (located within postcentral gyrus) Somatosensory association area Pert of Wernicke area Part of gnostic area Functions: Sensory interpretation of textures and shapes; understanding speech and formulating words to express thoughts and emotions. Terminates at the central sulcus- anteriorly Terminates at the parieto-occipital sulcus- posteriorly

Occipital Lobe

Primary visual cortex Visual association areas Functions: Conscious perception of visual stimuli; integration of eye-focusing movements; correlation of visual images with previous visual experiences.

Lateral Pectoral

Smaller branches of the brachial plexus Anterior rami: C5-C7 Motor innervation: Pectoralis major

Thalamus

Refers to paired oval masses of gray matter that lie on each side of the 3rd ventricle. Located between the anterior commissure and the pineal gland (midsagittal view) interthalamic adhesion: a small, midline mass of gray matter that connects the right and left thalamic bodies. The principle and final relay point for sensory information that will be processed and projected to the primary somatosensory cortex. Responsible for filtering out the sounds and sights in a busy dorm cafeteria when you are trying to study.

Visceral sensory nuclei

Receives information from sensory receptors such as the stretch receptors in the smooth muscle walls of viscera.

Motor homunculus

Reflects the amount of cortex dedicated to the motor activity of each body part.

Pudendal Nerve

Smaller branches of the Sacral Plexus Anterior Rami: S2-S4 Motor Innervation: Muscles of perineum, external anal sphincter, external urethral sphincter Cutaneous Innervation: Skin on external genitalia

Dorsal Scapular

Smaller branches of the brachial plexus Anterior rami: C5 Motor innervation: Rhomboids, levator scapulae

Nerve to subscapularis

Smaller branches of the brachial plexus Anterior rami: C5-C6 Motor innervation: Subclavius

Subscapular nerves

Smaller branches of the brachial plexus Anterior rami: C5-C6 Motor innervation: Subscapularis, teres major

Cerebellum

Second largest part of the brain Develops from the metencephalon Folds of the cerebellar cortex are called folia. Composed of left and right cerebellar hemispheres. Each hemisphere has a anterior and posterior lobe, which are separated by the primary fissure. Three regions: outer gray matter layer of cortex, an internal region of white matter (arbor vitae), and the deepest gray matter layer, which is composed of cerebellar nuclei. Coordinates and "fine tunes" skeletal muscle movements and ensures that skeletal muscle contraction follows the correct pattern leading to smooth muscle, coordinated movements.

Sulci

Shallow depressions between gyri is called sulci (sing. sulcus)

Suprascapular

Smaller branches of the brachial plexus Anterior rami: C5-C6 Motor innervation: Supraspinatus, infraspinatus

Superior Gluteal Nerve

Smaller branches of the Sacral Plexus Anterior Rami: L4-S1 Motor Innervation: Gluteus medius, gluteus minimus, and tensor fasciae latae

Inferior Gluteal Nerve

Smaller branches of the Sacral Plexus Anterior Rami: L5-S2 Motor Innervation: Gluteus maximus

Posterior Femoral Cutaneous Nerve

Smaller branches of the Sacral Plexus Anterior Rami: S1-S3 Cutaneous Innervation: Skin on posterior thigh

Stretch Reflex

Spinal Reflex A monosynaptic reflex that monitors and regulates skeletal muscle length. Stretch in a muscle is monitored by stretch receptors called muscle spindles. When a stimulus results in the stretching of a muscle, that muscle reflexively contracts. The patellar reflex is an example. The stimulus stretches the quadraceps femoris muscle and initiates contraction of the muscle, thereby extending the knee joint.

Withdrawal (Flexor) Reflex

Spinal Reflex A polysynaptic reflex arc that is initiated by a painful stimulus, such as touching something very hot. Stimulation of a receptor organ causes the transmission of sensory information to the spinal cord. Interneurons receive the sensory information and stimulate motor neurons to direct flexor muscles to contract in response. Simultaneously, antagonistic (extensor) muscles are inhibited so that the traumatized body part may be quickly withdrawn from the harmful situation.

Spinal nerves

Spinal nerves are called mixed nerves because they contain both motor and sensory axons. There are 31 pairs of spinal nerves that connect to the CNS to muscles, receptors, and glands. Each side has: 8 cervical nerves (C1-C8) 12 thoracic nerves (T1-T12) 5 lumbar nerves (L1-L5) 5 sacral nerves (S1-S5) 1 coccygeal nerve (Co1)

Frontal eye field

Superior surface of the middle frontal gyrus, which is immediately anterior to the premotor cortex in the frontal lobe.

Cervical Part

Supermost region of spinal cord Continuous with the medulla oblongata Contains motor neurons whose axons contribute to the cervical spinal nerves and receives input from sensory neurons through these spinal nerves.

Funiculus

The white matter of the spinal cord is external to the gray matter. White matter on each side of the cord is partitioned into three regions, called funiculus.

Lateral funiculus

The white matter region on each lateral side of the spinal cord is the lateral funiculus.

Functional Organization: Sensory and Motor Nervous System

The CNS and PNS perform three general functions: -Collection information. Receptors detect changes in the internal or external environment and pass them on to the CNS as sensory input. -Processing and evaluating information. After processing sensory input, the CNS determines what, if any, response is required. -Responding to information. After seeking an appropriate response, the CNS initiates specific nerve impulses called motor output. This travels through structures of the PNS to effectors (cells that receive impulses from motor neurons: muscles or glands).

Intercostal Nerves

The anterior rami of spinal nerves T1-T11 are called intercostal nerves because they travel in the intercostal space sandwiched between two adjacent ribs. T12 is called a subcostal nerve because it arises below the ribs, not between the two ribs. With the exception of T1, the intercostal nerves do not form plexuses. A portion of T1 helps form the brachial plexus. T2 conducts sensory impulses from the skin covering the axilla and the medial surface of the arm. Anterior rami of T3-T6- follow the costal grooves of the ribs and the intercostal muscles. In addition receives sensory info from the anterior and lateral chest wall. Anterior rami of T7-T12- inferior intercostal spaces, but als the abdominal muscles and their overlying skin.

Tracts

The axons within each white matter funiculs are organized into smaller structural units called tracts or fasciculi. Individual tracts conduct either sensory impulses or motor commands only. Each funiculus region contains both ascending and descending tracts. Thus, each funiculus contains both motor and sensory axons.

Epidural Space

The dura mater and the bones of the skull may be separated by the potential epidural space, which contains the arteries and veins that nourish the meninges and bones of the cranium. Under healthy conditions, not a space, but can fill with fluid if needed.

Cerebral Cortex

The external layer of gray matter Covers the surface of most of the adult brain

Synaptic knobs

The extreme tips of the fine extensions of telodendria are slightly expanded regions called synaptic knobs.

Cerebrum

The location of conscious thought processes and the origin of all complex intellectual functions. It is identified as the two large hemispheres. Center of your intelligence, reasoning, sensory perception, thought, memory, and judgement, as well as your voluntary motor, visual, and auditory activities. Formed from the telecephalon.

Limbic System

The limbic system and reticular formation, a loosely organized gray matter core in the brainstem. Composed of multiple cerebral and diencephalic structures that collaboratively process and experience emotions. It is a collective name for the human brain structures that are involved in motivation, emotion, and memory with an emotional association. Affects memory formation by integrating past memories of physical sensations with emotional states. Forms a ring around the diencephalon.

Conus Medullaris

The tapering inferior end of the spinal cord Marks the official "end" of the spinal cord proper (usually at the level of the first lumbar vertebrae)

Dural venous sinuses

The meningeal layer is usually fused to the periosteal layer, except in specific areas where the two layers separate to form large, blood-filled spaces called dural venous sinuses. Typically triangular in cross-section, they do not have valves to regulate venous blood flow. They are large veins that drain blood from the brain and transport to the internal jugular veins that help drain blood circulation of the head.

Cranial Dural Septa

The meningeal layer of the dura mater extends as flat partitions (septa) into the cranial cavity at four locations. Collectively, these double layers of dura mater are called cranial dural septa. They separate parts of the brain and provide additional stabilization and support to the entire brain. Four: The falx cerebri, tentorium cerebelli, falx cerebelli, and diaphragma sellae.

Superior Cerebellar Peduncles

The mesencephalon is the final destination of the superior cerebellar peduncles connecting the cerebellum to the mesencephalon.

Reflex arc

The neural wiring of a single reflex. Always begins at a receptor in the PNS, communicates with the CNS, and ends at a peripheral effector, such as a muscle or gland cell. Five steps: 1. Stimulus activates receptor. 2. Nerve impulse travels through sensory neuron to the CNS. 3. Information from nerve impulse is processed in the integration center by interneurons. 4. Motor neuron transmits nerve impulse to effector. 5. Effector (peripheral target organ) responds to nerve impulse from motor neuron.

Gyri

The outer surface of an adult brain exhibits folds called gyri (sing. gyrus).

Electrical Synapses

The plasma membranes of the presynaptic and postsynaptic cells are bound together. Electrical synapses are fast and secure, and they permit two-way signaling. Gap junctions formed by connexons between both plasma membranes, between the cells. Primarily occurs between smooth muscle cells and cardiac muscle at the intercalated discs.

Anatomy of spinal cord

The spinal cord is partitioned into an inner gray matter region and an outer white matter region. The gray matter is dominated by dendrites and cell bodies of neurons and glial cells and unmyelinated axons, whereas the white matter is composed primarily of myelinated axons.

Hemispheric Lateralization

The two hemispheres appear as anatomic mirror images, but they display some functional differences. Ex. the portions of the brain that are responsible for controlling speech and understanding verbalizarion are frequently located in the left hemisphere.

Higher-Order Processing Centers

These centers process information from several different association areas. Ultimately direct either extremely complex motor activity or complicated analytical functions. Involve functions such as speech, cognition, understanding spatial relationships, and general interpretation. Housed in both cerebral hemispheres. Primary -> Association -> Higher Order

Cranial Meninges

Three CT layers that separate the soft tissues of the brain from the bones of the cranium, enclose and protect blood vessels that supply the brain, and contain and circulate cerebrospinal fluid. Forms some of the veins that drain blood from the brain. Deep (closest to the brain): pia mater Middle: arachnoid mater Superficial (farthest away from the brain): dura mater

Cerebellar Peduncles

Three thick tracts, called peduncles, link the cerebellum with the brainstem. Superior cerebellar peduncles connect the cerebellum to the mesencephalon. Middle cerebellar peduncles connect the pons to the cerebellum. Inferior cerebellar peduncles connect the cerebellum to the medulla oblongata.

CN V

Trigeminal Sensory Function: General sensory from anterior scalp, nasal cavity, entire face, most of oral cavity, teeth, anterior two-thirds of tongue; part of auricle of ear. Somatic Motor Function: Muscles of mastication, mylohyoid, digastric (anterior belly), tensor tympani, tensor veli palatini Parasympathetic Motor (autonomic) Function: NONE

CN IV

Trochlear Sensory Function: NONE Somatic Motor Function: Superior oblique eye muscle Parasympathetic Motor (autonomic) Function: NONE

Lateral ventricles

Two In the cerebrum Separated by a thin medial partition called the septum pellucidum. Communicates with the third ventricle via an opening called interventricular foramen. Contains CSF

Structural Classification of Neurons

Unipolar Bipolar Multipolar

CN X

Vagus Sensory Function: Visceral sensory information from pharynx, larynx, coratid bodies, heart, lungs, and most abdominal organs. General sensory information from external acoustic meatus, eardrum, and pharynx Somatic Motor Function: Most pharyngeal muscles; laryngeal muscles Parasympathetic Motor (autonomic) Function: Innervates smooth muscle and glands of heart, lungs, larynx, trachea, most abdominal organs.

Ventral Group

Ventral anterior nuclei: Relay somatic motor information from cerebral nuclei and cerebellum to primary motor cortex and premotor cortex of frontal lobe. Ventral lateral nuclei: Same as ventral anterior nuclei Ventral posterior nuclei: Relay sensory information to primary somatosensory cortex of parietal lobe

CN VIII

Vestibulocochlear Sensory Function: Hearing (cochlear branch); equilibrium (vestibular branch) Somatic Motor Function: NONE Parasympathetic Motor (autonomic) Function: NONE

Nuclei

Within regions of gray matter are various functional groups of neuron cell bodies.

Third Ventricle

Within the diencephalon is a smaller ventricle called third ventricle. Lateral ventricles communicate with this ventricle via an opening called interventricular foramen. Communicates with fourth ventricle via a narrow canal called the cerebral aqueduct, which passes through the mesencephalon. Contains CSF

Cerebral nuclei

Within the masses of white matter, the brain also contains discrete internal clusters of gray matter called cerebral nuclei, which are oval, spherical, or sometimes irregularly shaped clusters of neuron cell bodies.

Posterior median sulcus

located on the exterior surface of the spinal cord Dips internally on the posterior surface

Anterior median fissure

located on the exterior surface of the spinal cord A slightly wider groove located on the anterior surface

Pyramids

medulla oblongata House the motor projection tracts called the corticospinal tracts

diverging circuit

spreads information from one presynaptic neuron to several postsynaptic neurons

Neurofibril Nodes

the portion of the axon not covered by myelin sheaths where nerve impulses jump from node to node Myelinated axons produce faster nerve impulses and requires less energy.

Presynaptic neurons post-synaptic neurons

transmit nerve impulses through their axons toward a synapse. conduct nerve impulses through their dendrites and cell bodies away from the synapse.