A/P CH.12-13

Axon

Axon

• Sends nerve impulses towards another neruron, muscle fiberl, or gland cell,

• Connects to cell by axon hill lock

• Either is myelanted or unmyelenated

Axon Hilllock

• Triangular area of the cell body

Axon Terminals

• Axons and axon collaterals conduct action potentials along their full lengths to end in many fine branches

Cell Body

• Contains nucleus surrounded by cytoplasm that includes typical cellular organelles

Dendrites

• Are the reciving portion of neurons

Endoneurium

Covers myelinated and unmyelinated axons

Epineurium

-Surrounds the whole nerve

Fascicle

• Bundle of nerve fibers

Myelin sheath

-Multilayerd lipid and protein covering around and some axons that insulate them and increases the speed of the nerve impulse conduction

Neurofibril (of Ranvier)

• are bundles of neurofilaments that extend into the dendrites and axon, and provide internal support to them.

Neurolemmocyte (Schwann Cell)

-PNS

• Line all 4 venticles of the brain as well as the central canal of the spinal cord

• These cell form the cerebrospinal fluid and their cilia move the CSF through the ventricles

Nissl bodies

• synthesis and segregation of proteins.

• Subcellular structures found in nerve cell bodies and DENDRITES. They consist of granular endoplasmic reticulum

Nucleaus of the Neuron

• the central area where all the neuronal protein synthesis takes place

• contains the genetic material that helps in the ribosomal RNA synthesis process.

• to guide the axon hillock that generates the impulses throughout the axon.

Perinerium

Surrounds each fasicle

Synaptic End Bulbs

• Towards the end of the axon terminal, closest to the muscle fiber, the tip of the axon terminal enlarges and becomes known as the synaptic end bulb.

• It is the synaptic end bulb of the motor neuron that comprises the neuromuscular junction.

• the neurotransmitter is released into a small space, the synaptic cleft.

Anterior (Ventral) Horn

-Anterior, Somatic motor neuron cell bodies

Anterior (Ventral) Median Fissure

• Anterior median fissure, wide deep groove on anterior surface of spinal cord

How many pairs of nerves in spinal cord?

31 pairs: -8 Cervical -12 Throacic -5 Lumbar -5 Sacral -1 Coccygeal

Brachail Plexus

• Provides almost the entire nerve supply to the shoulders and upper limbs

• Formed from anterior rami of C5-T1

• Main nerves are: -- Axillary (Deltoid) C5-C6 -- Median (Flexor muscles of forearm) C5-T1 -- Musculocutaneous (Bicep brachii/Brachiallis) C5-C7 -- Radial (Tricep brachii/ extensor of forearm) C5-T1 -- Ulnar (flexor carpi ulnaris/ muscle of hand) C8-T1

Cauda Equina

• Nerve roots arising from the inferior portion of the spinal crd continue inferiorly as a group

Central Canal

• Center of gray commissure and contains cerebrospinal fluid

Cervical Enlargement

• C3 to T1

• Designates the location of nuclei for the upper extremitiies

Cervical Plexus

• Supplies the skin and muscles of the head, neck, superior portion of the shoulders and chest, and diaphragm

• Formed from anterior rami

• C1- C5

• Imporant nevre is the PHRENIC nerve -- Which innervates the diaphragm and is important for breathing

Conus Medullaris

• Spinal cord is inferior to it

• between L1 and L2

Gray Commisure

• Narrow bridge of gray matter that connects the right and left side of gray matter in the middle of the spinal cord

Gray Matter

• Contains unmyelinated axons, cell bodies, dendrites, axon terminals, and neruoglia

• Gray matter receives and integrates incoming and outgoing information to perform spinal reflexes

Lumbar Enlargement

• T9 to T12

• Contans nucei for the lower extremitites

Lumbar PLexus

-- Supplies skin, abdominal wall, genitalia, and parts of lower limbs

• Made up of anterior rami

• L1-L4

• Major nerves are: -- Femoral L2-L4 --- Largest nerve, flexor muscles of hip joint and extensor muscles of knee joint, skin over anterior and medial aspect of thigh and medial side of leg and foot. -- Obturator nerves L2-L4 ---Adductor muscle of hip joint

Posterior (Dorsal) Horn

• Posterior, Contain neuron cell bodies that receive impulses from sensory neurons

Postererior Medial Sulcus (Fissure)

• Posterior median sulcus, a narraw groove

Sacral Plexus

-L4 to S4 -Formed from the anterior rami

• supllies lower limbs and glutes

Symphatic Trunk

• a paired bundle of nerve fibers that run from the base of the skull to the coccyx

White Matter

• Made up of myelinated axons

• White matter tacts conduct nerve impulses to and from the brain

Medula Oblongata

he connection between the brainstem and the spinal cord

Anterior Root

• Carry motor responses

• Down the CNS to muscles, nerves, glands

Common Fibular nerve

• Sacral Plexus

• L4-S2

• Fibularis longus muscle,

• tibialis anterior,

• extensor digitorumlongus

Femoral Nevre

• Lumbar Plexus

• L2-L4

• Iliopsoas -quadriceps femoris -sartoris

• pectineus

Orbturartor Nerve

• Lumbar plexus

• L2-L4

• Adductor longus

• Adductor brevis

• Aductor magnus,

• Gracilis

Median Nerve

• Brachial Plexus

• C5-T1

• Muscle of anterior forearm

• Muscle of hand

Musculocutaneous Nerve

• Brachial Plexus

• C5-C7 Bicep Brachii

• Brachialis

Posterior Root

-Carries sensory fibers

• Up the CNS

Posterior Root Ganglion

• Consist of sensory neuron cell bodies that synapse onto interneuron and motot neuron cell bodies

Radial Nerve

• Part of brachail plexus

• C5-T1 -Tricep brachii

• Extensor on forearm

Scaitic Nerve

• Sacral Plexus

• L4-S3

• Moves Bicep femoris

• Semimembraneous and semitendinosus

• Breaks up into tibial and common fibular nerve

Tibial Nerve

• Sacral plexes -L4-S3

• Gastronemius,

• soleus

• tibialis posterior

• flexor digitorum longus

• plantaris

• flexor hallucis longus

Ulnar Nerve

• Brachial Plexus -C8-T1

• Muscles of anterior forearm

Phrenic

• Cervical Plexus

• C3-C5

• Diaphragm

Ansa Cervicals

a neural loop in the neck formed by connecting the superior root from the cervical spinal nerves (C1–2) and the inferior root descending from C2–C3

Superior root of ansa cervicals

• created by the first cervical nerve (C1).

Inferior root of ansa cervicals

• comprised of nerve fibers arising from ventral rami of C2–C3.

• These two branches join in the anterior wall of the carotid sheath and form a neural loop. -The ansa cervicalis almost always travels anterior to the internal jugular vein [2].

Sensory Nerves (Chart)

• Input

• Receptors

• To feel

• Up the CNS

• Ascending

• Posterior/Back/Dorsal -Pre-ganglionic

• Afferent

Motor Nerves (Chart)

• Output

• Effectors

• To feel

• Down the CNS

• Descending

• Anterior/Front/Ventral

• Post-ganglionic

• Efferent

--- 2 main sundivisions of nervous sysyetem---

Central Nervous System (CNS)

Includes the Brain and spinal cord

Peripheral Nervous System (PSN)

Includes cranial nerves, spinal nerves & their branches, ganglia, and sensory receptors

---Organization of PNS---

Somatic Nervous system

• Conveys output from the CNS to the skeletal muscles only.

• Its motot responses can be be consciously controlled, the action of the PNS is VOLUNTARY

Autonomic Nervous sytem

• Conveys output from the CNS to smooth muscle, cardiac muscles, and glands

• Motor resposnses can be consciously controlled, the action of the PNS is Voluntary

Enteric Nervous System

• Network of over 100 million neurons confined to the wall of the digestive canal

• Helps regulate the activity of smooth muscles and glands

• Functions independtly, but communicates with branches of ANS

---Histology of Nervous tissue----

Nuerons

• Electrically Excitable

• Cellular structure

• Nerve impulses is called an action potential

Neurolgia

• Not electrically Excitable

• Make up about half of the volume of the nervous system

• Can multiply and divide

• 6 kind total ( 4 in CNS, 2 in PNS)

• Glue that holds nervous tissue together

--- Explanation of Neuron Cell---

Cell Body

• Contains nucleus surrounded by cytoplasm that includes typical cellular organelles

Dendrites

• Are the reciving portion of neurons

Axon

-Sends nerve impulses towards another neruron, muscle fiberl, or gland cell,

• Connects to cell by axon hill lock

• Either is myelanted or unmyelenated

---Structural Classification of nuerons---

Multipolar Neurons

• Usually have several dendrites and 1 axon

• Most neurons in the brain and spinal cord are this type, As well as motot neurons

Bipolar neurons

• Have 1 main dendrite and 1 axon

• Found in the retina of the eye

Unipolar neurons

• Have dendrites and 1 axon that are fused together to form a continues process from the cell body

• Found in sensory ganglia

---Functional Classification---

Sensory or afferent neruons

-Conveys information to the CNS -unipolar

Motor of efferent neurons

Conveys action potential from the CNS

• Multi Polar

Interneruons or association neurons

-Process sensory information and elict motor resposnes

• Multi polar

---Types of Neuroglia---

Neuroglia

Glue that holds nervous tissue together

Astrocytes

• CNS

• Have many process that make them look star shaped

• Wrap around and cover neurons and blood vessels to support them

• Guide neurons during development and control the composition of the chemical enviroment

Oligodendrocytes

-CNS

• Support the CNS neurons and have the process that form myelin sheaths around axons to increase speed of nerve impulses

Microglia

• CNS

• Are the phagocytes of the CNS that engulf debris, necrotic tissue and invading bacteria or virus

Ependymal cells

• CNS

• Lines all 4 ventricles of the brain as well as the central canal of the spinal cord

Schwann Cells

-PNS

• o Flattened cells that wrap around the axons in the PNS o Many Schwann cells form the myelin sheath around one axon.

Satellite Cells

-PNS -Have process that are flattend and surrounded sensory neruron cell bodies located in the ganglia in the PNS -They give support to these neurons and regulate their chemical enviroment

---Myelanation/ 2 types of axons---

Myelin sheath

-Multilayerd lipid and protein covering around and some axons that insulate them and increases the speed of the nerve impulse conduction

Unmyelinated

• Axons witouth myelin sheath

• Make up gray matter

Myelinated

• Axons with a myelin sheath

• Make up white matter

which 2 types of neuroglia produce myelin sheathS

• Schwannn Cells (PNS)

• Oligodendrocytes (CNS)

---Gray and White matter---

Gray matter

• Contains unmyelinated axons, cell bodies, dendrites, axon terminals, and neruoglia

• Gray matter receives and integrates incoming and outgoing information to perform spinal reflexes

White matter

• Made up of myelinated axons

• White matter tacts conduct nerve impulses to and from the brain

---Physiology-Electrical signals in neurons: 2 types---

Action Potential

• membrane potential and resting membrane potential

• Communicate over SHORT and LONG distances occurs when a neuron sends information down an axon, away from the cell body.

Graded potentials

• A graded potential occurs in response to the opening of a mechanically-gated or ligand-gated ion channel

• Allow communications over SHORT distances only

Resting Membrane potential

• Unequal distribution of ions across the plasma membrane and the selective permeability of the neuron’s membrane to N a+ and K+

• Most anions cannot leave the cell

• N a+/K+ pumps

---2 types of Graded Potentials---

Hyperpolarizing graded potential

• When the response makes the membrane more polarized (inside more negative)

Depolarizing graded potential

• When the response makes the membrane less polarized (inside less negative)

---Generation of action potential: 3 phases---

Depolarzing phase

• Excitation

• The negative membrane potential becomes less negative, reaches zero, and then become positive.

Repolarizing Phase

• Relaxation The membrane potential is restored to the resting state of -70 mv