Mizzou Anatomy 2201 Hill Exam 3

SP: Common Fibular Nerve

Sensory innervation- skin of antero-lateral leg, skin on dorsum of foot

Motor innervation- Muscles of anterior leg, muscles of lateral leg

Lesion to this nerve causes foot drop

Functions of the Nervous System

1. Collect information: (sensory input from PNS)

2. Process and evaluate information: processes sensory input and determines response

3. Respond to information: dictates response by activating effector organs

Nervous System: Somatic Sensory

nerve endings in almost all body tissue

has receptors for touch, pain, pressure, vibration, temp

also for sense of body in space

"special senses"

Nervous System: Visceral Sensory

Sensations from the organs

Only stretch and temperature

Nervous System: Somatic Motor

Voluntary muscle system

Contraction of skeletal muscles

Nervous System: Autonomic Motor

Involuntary nervous system

Regulates contraction of smooth and cardiac muscle and gland secretion

Can't control this

Subdivides into sympathetic and parasympathetic

Nervous Tissue

2 types of cells: neurons and glia

Neurons transmit electrical signals (excitable)

Glia ("nerve glue") are supporting cells (not excitable)

Structure of a Neuron

Dendrites- receive signal, transmit to cell body

Soma (cell body)- contains nucleus cytoplasm, organelles

Axon- (long cell process) transmits signal to exon terminals

Myelin insulates axon

Neuron Signal Pathway

Dendrite --> Cell body --> Axon --> Axon terminal

More dendrites more impulses recieved

Synapse

where an axon connects with another cell

Chemical Synapse

Most numerous

Uses neurotransmitters

Electrical Synapse

rely on flow of ions at gap junctions

CNS Glia: Ependymal Cells

Help produce CSF

CNS Glia: Microglia

Defense

CNS Glia: Oligodendrocytes

Myelinates axons

CNS Glia: Astrocytes

Most common

Blood brain barrier

Nerves

a collection of axons in the PNS

Myelinated and non- myelinated

Nerve Structure

Each axon is surrounded by myelin sheath (Schwann Cells)

Groups of axons are nerve fascicles

Groups of fascicles = nerve

Endoneurium

Surrounds axon and myelin sheaths

Perineurium

Surrounds fascicles

Epineurium

Surrounds entire nerve

Multiple Sclerosis (MS)

Progressive demyelination of neurons in CNS with destruction of oligodendrocytes

Functions of the Brain

1. Controls heart rate, respiration, etc.

2. Innervation of head, neck, and viscera

3. High level tasks- intelligence, consciousness, etc.

Main Parts of the Brain

1. Cerebrum- Largest

2. Diencephalon

3. Cerebellum

4. Brain stem

Midbrain

Pons

Medulla oblongata

Gray Matter

is on the outer part of the brain

Also the innermost regions

Gray matter is unmyelinated neurons and neuron cell bodies

White Matter

is made of myelinated axons, lies deep to the cortex of the brain

Diencephalon ("in between brain")

Surrounded by cerebral hemispheres

Contains 3rd ventricle

Thalamus

Filters somatosensory, visual, and auditory info (all but smell)

Any part of the brain that communicates with the cerebral cortex must go through this first

"gate way to cerebral cortex"

Hypothalamus

Main visceral control center of the body, regulates many activities

Epithalamus

Includes pineal gland (which secretes melatonin for circadian rhythm)

Cerebrum

Divided into two halves Left and Right hemispheres

Each hemisphere is divided into 5 lobes: Frontal, Parietal, Occipital, Temporal, and Insula (deep to temporal and parietal lobes)

Cerebrum: Gyri and Sulci

Gyri- ridges of the brain tissue, allow for more cortex to fit in the crainal vault

Sulci- grooves between the gyri

Cerebral Functions

Intelligence and complex thinking

3 types of functional areas

1. Sensory - conscious awareness of sensation (senses)

2. Association areas- integrate info (compare with previous experiences)

3. Motor areas- voluntary motor functions (response of association areas)

Cerebrum: Primary Somatosensory Cortex

In post central gyrus

cortex that receives info from somatic senses and enables conscious awareness of the senses

Cerebrum: Primary Visual Cortex

posterior/medial occipital lobe receives info from eyes (farthest possible from eyes)

Cerebrum: Primary Auditory Cortex

in the temporal lobe, receives and process auditory info from inner ear

Cerebrum: Primary Motor Cortex

Is located in precentral gyrus, Control voluntary skeletal muscle, also Broca's Area

Cerebrum: Broca's and Wernicke's Area

Broca's- motor speech area, controls motor movements for speech. If damaged an understand speech but can't speak it very well (temporal lobe)

Wernicke's- multimodal association area, recognition and understanding of speech. If damaged can speak but not comprehend language

Cerebrum: White Matter

Corpus Callosum- is largest, most visible band of commissural tissue fibers (connect hemispheres

Association Fibers- short fibers that connect regions in the same hemisphere

Cerebrum: Cerebral Nuclei

the deep paired masses of gray matter (basal nuclei) involved in motor control

Brain Stem Functions

1. Connects cerebrum and spinal cord

2. Start of cranial nerves for innervation of the face and head

3. Autonomic and reflex centers needed for survival

Brain Stem: Midbrain

Located between diencephalon and pons

Cerebral aqueduct- connects 3rd and 4th ventricle

Tectal Plate- site for reflexes

Superior Colliculi- for visual reflexes

Inferior Colliculi- responds to sound

Brain Stem: Pons

Located between midbrain and medulla. Separated from cerebellum by 4th ventricle

Brain Stem: Medulla Oblongata

Most caudal part of brain stem; continuous with spinal cord

Pyramids carry voluntary motor output from cerebrum to spinal cord

Fibers "decussate" or crossover left controls right, right controls left

Cerebellum Functions

1. Fine tunes/tweaks body

2. Coordinates body movements

3. Maintain posture and equilibrium

Cerebellum

2 hemispheres connected by vermis

Folia: leaflike folds increase surface area

Outer is gray matter

What matter is Arbor Vitae (tree of life)

(hindbrain)

Cerebellum: Processing

Receives info from cerebrum on movements planned

Compares planned movements with current body position

Sends instructions back to cerebral cortex to readjust motor commands

Limbic System

Involved with emotion and motivation, creating, storing, retrieving memories

1. Cingulate gyrus-emotional response

2. Hippocampus- stores memory

3. Amygdala- processes fear

Connected by fornix

Pia Mater

Innermost lay, follows curves of brain, very delicate and lots of blood vessels

Arachnoid Mater

Superficial to pia mater. Looks like spiderweb

Subarachnoid space- weblike threads attach arachnoid mater to pia mater filled wit CSF

Dura Mater

outmost layer

Two layers

1. Meningeal (Deepest)

2. Periosteal (Superficial)

These layers run together but split apart to form dural sinuses

Also migraines occur in the pia mater

Dural Sinuses

Drain blood from brain into the internal jugular vein.

Anterior/Superior -> Posterior/Inferior: Superior Sagital Sinus> Straight Sinus> (Confluence>) Transverse Sinus> Sigmoid Sinus

Ventricles

Lateral ventricles (1 and 2) communicate with 3rd via interventricular foramen

3rd ventricle drains into 4th via cerebral aqueduct

circulate CSF

CSF

Prevents damage/crushing

Resists compressive forces, cushions against trauma, feeds brain, removes waste, carries chemical signals

CSF Flow

1. Made in choroid plexuses

2. Flows thru ventricles > subarachnoid space

3. Flows thru subarachnoid space

4. Absorbed > dural venous sinuses

~500mL/day is processed/circulated

Brain Blood Supply

Internal carotid divides into anterior and middle cerebral arteries. Anterior cerebral joins anterior communicating artery. Middle cerebral artery supplies ~80 of cerebrum (parts of temporal and parietal lobes)

Basilar Artery

Formed by fusion of right and left vertebral, divides into posterior cerebral arteries (a/p cerebral connected by post. comm.)

NOT part of Cerebral Arterial Circle

Circle of Willis (Cerebral Arterial Circle)

Allows re-routing of blood flow through anastomosis

Composed of anterior cerebral artery (L&R), anterior communicating artery, internal carotid artery (L&R), posterior cerebral artery (L&R), and posterior communicating artery (L&R)

Spinal Cord Functions

1. Sensory and motor innervation of body

2. Two-way conduction pathway for signals between body and brain

3. Major center for reflexes

Spinal Cord (location)

Extends from foramen magnum to L1 or L2

31 pairs of spinal nerves

-8 cervical

-12 thoracic

-5 lumbar

-5 sacral

-1 coccygeal

Cervical/Lumbar Enlargements

Necessary for nerves supplying upper/lower limbs.

Conus Medullaris

Inferior end of actual spinal chord, ends at L1 in adults and L4 in kids.

Cadua Equina

Bundle of nerve roots at inferior end of vertebral canal. (very end of spine)

Filum Terminale

A long filament that extends from conus medullaris to coccyx that acts as a tether.

Spinal Cord Protection

Bone, meninges (same 3 as brain), and CSF

Epidural space that is filled with fat and veins (outside dura mater)

Denticulate ligaments anchor spinal cord to dura mater

Spinal Cord: Clinical

Epidural nerve block is injected between L4 & L5 w/o risk of damage to spinal cord. Cauda equina gets "pushed" out of the way if necessary.

Location of Spinal Nerves (in respect to vertebrae)

Most cervical spinal nerves emerge SUPERIOR to their respective vertebrae (C1 nerve emerges superior to C1 vertebra)

C8 nerve emerges inferior to C7 vertebra.

Thoracic -> Coccygeal emerge INFERIOR to respective vertebrae.

Spinal Cord Gray Matter

"H" shape, surrounded by white matter

Commissure: unmyelinated axons crossing from one side to the other.

Posterior arms = dorsal horns

Anterior arms = ventral horns

Ventral and Dorsal Roots

Dorsal horns receive information from sensory neurons (located in ganglia)

Sensory neuron signals reach SC via DR.

Ventral horns send out info to skeletal muscle.

Signals to motor neurons travel via VR.

Spinal Nerves

Formed by merged dorsal and ventral roots.

Has both sensory and motor axons.

Immediately splits into dorsal and ventral rami.

Exits vertebral column @ intervertebral foramina.

Ventral Rami

Carries both sensory and motor fibers.

Innervate most of the body, including trunk and limbs.

Dorsal Rami

Carries both sensory and motor fibers.

Innervate small portion of the back.

Reflexes

Basic structural plan of NS, simple neuron chain.

Usually exclude brain: rapid, automatic, unlearned motor response to stimuli.

Signal synapses at SC.

Ex. somatic: hot stove, visceral: vomiting.

Dermatome

Area of skin supplied by a single spinal nerve. ALL spinal nerves except C1 have this.

Numbness can pinpoint spinal cord injuries

Referred Pain

When pain from an organ is mistakenly referred to dermatome.

I.E. Appendicitis starts as pain in T10 dermatome.

Nerve Plexus

A network of nerves formed only VENTRAL rami of spinal nerves only.

All but T2-T12 branch and rejoin.

Damage to one spinal nerve cannot completely paralyze and limb muscle.

Cervical Plexus

Ventral rami of first 4 cervical nerves

Most are sensory

Some motor to anterior neck

Phrenic nerve comes from C3, C4,C5- diaphragm

Brachial Plexus

Partly in neck, partly in axilla

Gives rise to most nerves of the upper limb

Brachial plexus divisions: 5 roots merge into 3 trunks which branch 2 divisions each.

Anterior division: nerves that innervate anterior compartment muscles of upper limbs and skin.

Posterior division: nerves that serve posterior compartment and skin.

Contains Axillary, Radial, Ulnar, Medial, and Musculocutaneous nerves

Brachial Plexus Division

Roots (C5, C6, C7, C8, and T1) divide into Upper (C5, C6), Middle (C7, C8), and Lower (C8, T1) branches. Trunks branch into anterior and posterior divisions.

BP: Musculotaneous Nerve

Sensory innervation: skin sensation for lateral forearm

Motor innervation: Anterior compartment of arm (Coracobrachialis, Biceps brachii, brachialis 1/2)

BP: Ulnar Nerve

Sensory innervation: skin of medial hand, medial side of digit 4, all of digit 5

Motor innervation: flexors and intrinsic hand muscles (interossei, hypothenar (pinky))

BP: Median Nerve

Sensory innervation: skin of lateral palm and digits 1-3 and lateral side of digit 4

Motor innervation: anterior compartment of forearm (w/ ulnar), thenar muscles of palm (thumb)

Nerve affected by carpal tunnel syndrome: pain/numbness in lateral palm from compression of nerve near hand

BP: Axillary Nerve

Sensory innervation: shoulder joint and skin overlying part of deltoid muscle.

Motor innervation: teres minor and deltoid.

BP: Radial Nerve

Sensory innervation: skin over dorso-lateral arm, forearm, and hand

Motor innervation: posterior compartment of arm and forearm (all posterior compartment muscles)

Lumbar Plexus

L1-L4

LP: Femoral Nerve

Sensory innervation: skin of antero-medial thigh, skin of medial leg and foot

Motor innervation: muscles of anterior thigh (thigh flexors, leg extensors)

TIP: F=front/flex

Sacral Plexus

L4-S4

LP: Obturator Nerve

Sensory innervation: skin of medial thigh

Motor innervation: muscles of medial thigh (adductors)

SP: Sciatic Nerve

Tibial Nerve & Common Fibular Nerve togethe in common sheath

Longest and thickest nerve of the body. serves all of lower limb except anterior/medial thigh

SP: Tibial Nerve

Sensory innervation: skin of postero-lateral leg, skin of sole of foot (subdivides into plantar nerves)

Motor innervation: Muscles of posterior thigh, muscles of posterior leg

Nerve Lesions: Clinical

Phrenic: difficulty breathing

Axillary: difficulty abducting arm to 90 degrees

Musculocutaneous: weakness flexing elbow

Median: carpal tunnel syndrome, weakness flexing wrist

Radial: difficulty extending elbow, wrist drop

Ulnar: can't ad/abduct fingers, "funny bone"

Femoral: walking probs, buckling knees

Tibial: shuffling gait, difficulty w/ plantar flexing

Common Fibular: foot drop

Autonomic Nervous System

General PNS visceral motor system

Involuntary control of visceral functions, regulates smooth and cardiac muscle and glands.

Controls all the "routine" physiological functions.

ANS: Sympathetic

ACTIVATES

"fight or flight"

Causes widespread, long lasting mobilization of fight or flight response

Thoracolumbar: preganglionic neuron cell bodies in thoracic/lumbar SC.

Emergencies, exercise, excitement

ANS: Parasympathetic

INHIBITS

"Rest and digest"

These effects are highly localized and short lived

Craniosacral: preganglionic neurons in brain/sacral regions of SC.

Normal, everyday functioning.

Skin

Largest organ in the human body

7% of total body weight

Skin Functions

1. Protection against mechanical damage

2. Prevent water loss because of water resistance

3. Vitamin D production

4. Sensory reception

5. Temperature regulation (sweat)

6. Excretion of salt/wastes

Epidermis

Keratinized stratified squamous epithelium

4 cell types

Avascular

Regenerates every 35-45 days

Epidermis Cells

Keratinocytes- product keratin, most abundant

Melanocytes- melanocytes produce melanin (shield from UV radiation)

Merkel Cells- sensation

Dendritic Cell- immune cells

Layers of Epidermis

Superficial>Deep

1. Stratum Corneum- dead cells full of keratin, shed regulary.

2. Stratum Lucidum- "clear" layer, only in thick skin, consists of a few rows of flat, dead keratinocytes. (palms and soles of feet)

3. Stratum Granulosum- 1-5 layers of cells. Granules in this layer help waterproof skin.

4. Stratum Spinosum- multiple cell layers of keratinocytes. Only layer with dendritic cells*

5. Stratum Basale- deepest layer, attached to dermis. Mostly keratinocytes with rapid division. Holds melanocytes and merkel cells.

Dermis

Underlies epidermis

Strong, flexible connective tissue

Highly vascularized

Innervated (sensation)

2 cell layers: papillary-superficial (20%), reticular-deep (80%).