A/P CH.12-13

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