mizzou anatomy exam 3

functions of the nervous system

1. collect information

2. proccess and evaluate info

3. respond to info

central nervous system

brain and spinal cord

peripheral nervous system

the sensory and motor neurons that connect the central nervous system to the rest of the body

- cranial nerves, spinal nerves, ganglia

sensory nervous system

The system of nerves that carries information from the body's receptors to the CNS

somatic sensory

receives sensory information from skin, fascia, joints, skeletal muscles, special senses

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

visceral sensory

sensation from organs, only stretch and tempature

function of the motor nervous system

Transmits information from CNS to the rest of the body, sends motor information to effectors

somatic motor

"voluntary" nervous system: innervates skeletal muscle

autonomic motor

"involuntary" nervous system: innervates cardiac muscle, smooth muscle, glands

- sympathetic and parasympathetic

2 types of cells in nervous tissue

neurons: transmit electrical signals (excitable)

glial cells: nerve glue, are supporting cells (not excitable)

neurons

Cells that transmit electrical message from one area of the body to another area.

dendrite

receive signal, transmit to cell body. Smaller projections from the soma

soma

cell body of a neuron, contains nucleus, cytoplasm, organelles

myelin

insulates axon, helps speed up signal through axon

Axons

long cell process, transmits signal to axon terminals

pathway a nerve travels through neuron

dendrite, cell body, axon, axon terminal

synapase

where one neuron meets another

chemical: use neurotransmitters

electrical: rely on flow of ions at gap junctions

4 types of glia in CNS

astrocytes

- most common, blood-brain barrier

microglia

- defense

ependymal cells

- helps produce CSF

oligodendrocytes

- myelinates Axons

2 types of glia in PNS

Schwann cells: myelinated axons of PNS/ myelin sheath

satellite cells: found in ganglia, surround the neuron cell bodies

(ganglia are collections of neuron cell bodies outside of CNS)

What is a nerve?

collection of axons in the PNS

axons are arranged in parallel and wrapped in Connective tissue

Nerve Structure

Group of axons= fascicles

group of fascicles= nerve

Endoneurium

inside the fasicle that covers each axon

deepest layer of nerve

surrounds myelin sheath NOT the actual myelin sheath

perineurium

surrounds each fascicle

middle layer of nerve

epineurium

surrounds the entire nerve

most superfical layer

multiple sclerosis

Progressive demyelination of neurons in CNS with destruction of oligodendrocytes (glia)

interrupts conduction of nerve impulses

inflammation leads to scarring and permanent problems

functions of the brain

Controls heart rate, respiration and blood pressure and maintains homeostasis.

Innervation of head, neck and viscera.

High level tasks - intelligence, consciousness, memory, emotion, behavior

4 main parts of the brain

cerebellum

cerebrum

diencephalon

brainstem (midbrain, pons, medulla oblongata)

gray mater

located in horn of spinal cord

unmyelinated

all over outside of brain

white mater

myelinated

outside of SC

inside of brain

diencephalon

lateral walls= thalamus

floor= hypothalamus

roof= epithalamus

contains 3rd ventricle

surrounded by cerebral hemisphere

thalmus

Lateral walls of 3rd ventricle

gateway to cerebral cortex

largest part of diencephalon

filters somatosenosory, visual and auditory info (not smell)

any part of brain that communicates with cerebral cortex must go through...

thalamus

functions of hypothalamus

- Control of the autonomic nervous system (visceral control)

- Control of the endocrine system

- body temp

- hunger/thirst

- sleep/wake cycle

-emotional responses

-formation of memory

epithalamus

roof of 3rd ventricle

contains the pineal gland (secretes melatonin)

cerebrum

divied into left and right hemisphere

contains 5 lobes of brain

- Frontal, parietal, occipital, temporal, insula

Cerebral Functions

Intelligence and complex thinking

3 types of functional areas

1. Sensory - conscious awareness of sensation

2. Association areas- integrate info

3. Motor areas- voluntary motor functions

gyri

ridges, allow for more cerebral cortex to fit in the cranial vault

sulci

shallow grooves that separate gyri

central sulcus

separates frontal and parietal lobes

parietal-occipital sulcus

separates parietal and occipital lobes

lateral sulcus

Separates temporal lobe from parietal and frontal lobes

primary somatosensory area

- in postcentral gyrus

receives information from senses (touch, pressure, vibration, pain, proprioception) and enables conscious awareness of the senses

primary visual cortex

- in posterior part of occipital lobe

receives visual info from retina of eye

primary auditory cortex

- in temporal lobe

receives and processes auditory information from inner ear

primary motor cortex

- precentral gyrus

controls skeletal muscle movement, Broca's

brocas area

speech production

front lobe

wernickes area

speech comprehension

temporal lobe

corpus callosum

A thick band of axons that connects the two cerebral hemispheres and acts as a communication link between them. (white mater)

Cerebral Nuclei

- Deep gray matter

also called basal ganglia, involved in motor control

INclude caudate nucleus, putamen, amygdala and globus pallidus

start and stop, regulate the intensity of voluntary movements

functions of brainstem

1. connects cerebrum to spinal cord

2. start of cranial nerves for innervating the face and head

3. autonomic relfex center needed for survival

Midbrain

Located between diencephalon and pons

internal cavity is cerebral aqueduct

tectal plate, superior colliculi, inferior colliculi

Pons

Located between midbrain and medulla, separated from cerebellum by fourth ventricle

Medulla oblongata

most caudal, continues with spinal cord

pyramids carry voluntary motor output

left Brian controls right side of body, right brain controls left side of body

cerebellum

1. Fine-tunes/tweaks body movements

2. Coordinates body movements

3. Maintain posture and equilibrium

connected to brainstem

Cerebellum Features

connected by vermis

folia increase surface area

Arbor vitae- tree of life, white matter

Processing= receives info from cerebrum on movements planned

compares planned movements with current body position

sends instructions back to cerebral cortex to readjust/refine motor commands

Limbic System

Emotion and motivation, creating, storing, retrieving memories

1. Cingulate gyrus: emotional response

2. Hippocampus: stores memory

3. Amygdala: processes fear

protect the brain

Meninges= cover and protect CNS, enclose and protect blood vessels to CNS, contain and circulate CSF

CSF= resists compressive forces, cushions, feeds brain, removes wastes, carries chemical signals

Blood-brain-barrier= protects brain from exposure to toxins

pia mater

Innermost layer, follows curves of brain, very delicate, lots of blood vessels

arachnoid mater

superficial to pia mater, looks like spiderweb

subarachnoid space- weblike threads attach to arachnoid mater to Pia mater. Filled with CSF

dura mater

outermost layer of meninges, two layers of dense fibrous connective tissue (meningeal inferior to periosteal)

separates to form dural sinuses for brain

from outermost to inward meninge layers

dura

arachnoid

subarachoid

pia

dural venous sinuses

drain blood from brain and drain into the internal jugular veins

superior sagittal sinus

Striaght sinus

transverse sinus

sigmoid sinus

function of ventricles

making and circulating CSF

lateral ventricles

2, communicate with this ventricle via interventricular foramen

Third ventricle

Drains into fourth ventricle via cerebral aqueduct

CSF

1. Made in choroid plexuses

2. Flows through ventricles and into subarachnoid space

3. Flows through subarachnoid space

4. Absorbed into dural venous sinuses

500ml a day produced

Blood Supply for brain (anterior)

Internal carotid divides into anterior and middle cerebral arteries.

Anterior cerebral artery joins anterior communicating artery.

Middle cerebral artery supplies parts of temporal and parietal lobes

(= ~ 80% of cerebrum).

Blood supply for brain

Right and left vertebral arteries merge to become basilar artery, which divides into posterior cerebral arteries

there are connected into posterior communicating arteries

Circle of Willis

Anastomosis to protect brain's blood supply (allows re-routing of blood flow) Formed by posterior cerebral arteries (l, r), posterior communicating arteries (l, r), internal carotid arteries (l, r), anterior cerebral arteries (l, r),anterior communicating artery.

Function of the Spinal cord

Part of CNS

Functions:

1. Sensory and and motor innervation of body

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

3. Major center for reflexes

Spinal Nerves

Extends from foramen magnum to level of L1 or L2 (lumbar vertebrae)

31 pairs of spinal nerves (part of PNS)

- 8 cervical spinal nerves

- 12 thoracic spinal nerves

- 5 lumbar spinal nerves

- 5 sacral spinal nerves

- 1 coccygeal spinal nerve

Cervical, lumbar enlargements for nerves supplying upper and lower limbs.

Conus Medullaris

Inferior end of actual spinal cord

ends at L1 vertebra in adults, and L4 in kids

Cauda Equina

Bundle of nerve roots at inferior end of vertebral canal is caudal equina

Film terminale

long filament that extends from conus medullaris to coccyx

acts as a tether

Spinal Cord protection

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

deep to superficial : Pia mater, subarachnoid space, Arachnoid mater, Subdural space, dura matter

Denticulate ligaments

Anchor spinal cord to dura mater

Posterior (Dorsal) Roots

Dorsal horns receive information from sensory neurons (cell bodies located in the dorsal root ganglia). Signals from sensory neurons reach spinal cord via dorsal roots.

anterior (ventral) roots

Ventral horns send out info to skeletal muscle. Signals going out to motor neurons travel via ventral roots.

Dorsal and Ventral Ramus

both contain sensory and motor axons, then connect to spinal nerve which ALSO has both sensory and motor axons

Reflexes

Simple neuron chain, Basic structural plan of nervous system, Reflexes usually exclude brain; rapid, automatic, unlearned motor response to stimulus

can be somatic (hot stove), or visceral (vomiting)

Signal comes in and synapses at spinal cord

- Patellar reflex

Dermatomes

Area of skin supplied by a single spinal nerve, except C1

Referred pain: EX: pain starts in T10, actually appendicitis

Nerve plexuses

network of nerves, formed by VENTRAL rami of spinal nerves only

all except T2-T12 branch and rejoin

Damage to one spinal nerve cannot completely paralyze any limb muscle

4 types of nerve plexus

cervical C1-C4

brachial C5-T1

lumbar L1-L4

sacral L4-S4

Cervical Plexus

- Ventral Rami of first 4 cervical nerves

- Most are cutaneous sensory, some motor to anterior neck

- Phrenic nerve receives fibers from C3, C4, and C5; innervates diaphragm for respiration

Brachial Plexus

ventral rami of C5-C8 and most of ventral ramus of T1

- 5 roots merge into 3 trunks which branch into 2 divisions each.

- Anterior division = nerves that innervate anterior compartment muscles of upper limb and skin.

- Posterior division = nerves that serve posterior compartment and skin.

5 nerves of the Brachial Plexus

axillary, musculocutaneous, radial, median, ulnar

Musculocutaneous Nerve

Sensory Innervation: skin sensation for lateral forearm

Motor Innervation: anterior compartment of arm (coracobrachialis, biceps brachia, brachialis)

if damaged: weakness flexing elbow

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 muscle.

if damaged: can't adduct/abduct fingers, "funny bone"

Median Nerve

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

Motor innervation: Anterior compartment of forearm (with ulnar) Thenar muscles of palm (muscles that oppose the thumb)

if damaged: weakness flexing wrist, difficulty opposing thumb, carpal tunnel

Axillary Nerve

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

Motor innervation: teres minor and deltoid

if damaged: difficulty abducting arm to 90 degrees

Radial Nerve

Sensory innervation: skin over dorsolateral arm, forearm and hand

Motor innervation: Posterior compartment of arm and forearm (extensors)

- triceps brachii, extensors

if damaged: difficulty extending elbow, wrist drop

Lumbar Plexus

L1-L4

femoral nerve

obturator nerve

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)

- iliopsoas, sartorious, rectus femoris, vastus mm.

if damaged: walking problems, knee buckles

Obturator Nerve

Sensory innervation- skin of medial thigh

Motor innervation- muscles of medial thigh (adductors)

- adductor longus, gracilis, Manaus and brevis

Sacral Plexus (L4-S4)

Anterior division: Sciatic, common fibular, superficial fibular, deep fibular, tibial, pudendal

Posterior division: superior gluteal, lumbosacral trunk, inferior gluteal, posterior femoral cutaneous

- Tibial Nerve & Common Fibular Nerve together in common sheath = "Sciatic Nerve"

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

Tibial Nerve

Sensory innervation: skin of poster-lateral leg, sole of foot

Motor innervation: Muscles of posterior thigh, posterior leg

- adductor mangus w/obturator n, biceps femoris w/common fibular nerve

if damaged: shuffling gait, difficulty w/plantar flexing