(Organizational Principles)

Interconnectivity of the Brain

primary sensory and motor regions in the crebrum are conneted through association and commissural fibers.

This allows messages w/i hemisphere and b/w hemispheres

(Organizational Principles)

Centrality of CNS

integrates incoming and outgoing information

everything must go through the CNS

synthesize incoming

generate response

Commissural fibers

consists of brain & spinal cord

integrates incoming/outgoing information

generates appropriate responses

(Organizational Principles)

Hiearchy of Neuraxial Organization

complexity of info processing increases the more cephalic (of or related to the head)

1. Spinal Cord

2. Brainstem/Spinal Cord

3. Cerebral cortex

**all work together to keep an optimal homeostatic state

(Laterality)

Bilateral Anatomic Symmetry

two hemispheres are similar w/ minor differences

(Organizational Principles)

Laterality

1. Bilateral Anatomic Symmetry

2. Unilateral Functional Difference

3. Contralateral Sensorimotor Control

(Laterality)

 Unilateral Functional Difference

two hemispheres are equipotential at birth and then in first few years they have specialized functions

(Laterality)

Contralateral Sensorimotor Control

all sensory and motor fibers decussate (cross) the body's midline

>most at caudal medulla of brainstem

>pain/temp at midline at spinal cord

>some cross multiple pathways

(Organizational Principles)

Functionally Specialized Networking

specialization of nerve cells in motor and sensory systems that lead to

1. increased adaptability

2. increased processing speed

3. ability to make detailed analysis of selected signals

(Organization Principles)

Topographic Organization in Cortical Pathways

brain pathways and areas reflect body surface

(homunculus)

(Organizational Principles)

Plasticity

Brain's capability of being reorganized in the face of an injury

mostly evident in ages under 6

Paul Broca (1861)

French physician, focused on people who couldn't articulate but could understand

patient: M. Leborgne (epileptic lost ability to speak at 31)

"tan, tan"

issue of coordinating movements not memory

Karl Wernicke (1874)

German, auditory comprehension of speech, aphasia

nerve cell

nerve(s)

one or more bundles of myelinated or unmyelinated fibers in the peripheral nervous system (PNS)

Neuron

Glial cells or Neuroglia

Cells associated with nervous system responsible for a variety of supportive functions

-Astrocyte, oligodendrocytes, microglia cells, ependymal cells, and Schwann cells

Unipolar neurons

• exist in ganglia of PNS
• primarily sensory neurons from physical stimulus
  
• 1st in a line of neurons carrying sensory information from periphery to hemispheres

Bipolar Neuron

"interneuron"

two process- one in CNS & one in PNS

*both processes conduct nerve impulses

3 Factors that affect speed of transmission

diameter of axon: fatter=faster

length of axon: shorter=faster

myelinattion: more=faster

Demylenation

impairs conduction of neural impulses, impairment in sensosimotor fuctions and speech-language-cognitive skills

CNS: Multiple Sclerosis

PNS: Gulliam-Barre syndrome

Teledendrion

CNS terminology

Nucleus: cluster of neurons in brain or spinal cord

Tract: bundle of nerve fibers

Faciculus: several trats

PNS terminology

ganglion: cluster of neurons in periphery

nerves: one or bundles of the nervous system that conducts electrical impulses (cranial and spinal nerves)

**basal ganglia is in the forebrain!

collection of nerve cells that forms the external surface of the brain

-White Matter

-Gray Matter

gray matter

the gross appearance of the brain

-nerve cells; neurons

-supporting glia cells

-unmyelinated fibers

white matter

consists of nerve fibers that form tracts and carry information from one brain site o another

-myelin

Cerebrum

(cerebral hemispheres and cortex)

Functions

higher mental functions

regulates sensorimotor integration

regulates perceptions w/ experiences

Basal Ganglia Functions

(subcortical nuclei)

regulate motor movements and muscle tone

Diencephalon Functions

(Thalamus)

On either side of 3rd ventricle/medial to intner capsules

2 egg shaped bridged by massa intermedia

consists of numerous nuclei

-channels sensorimotor information to cortex

-cortex-mediated functions

-crude awareness for sensation

-states of sleep/walefullness

Diencephalon Functions

(Hypothalamus)

under thalamus, contains small nuclei

Regulates body temperature, food intake, water balance, hormonal secretions, emotional behavior, sexual responses

controls activities in the autonomic nervous system

Midbrain Functions

adjoins pons & diencephalon

-Mediates auditory/visual reflexes

-Regulates cortical arousal

-Houses cranial nerve nuclei

Cerebellum Funcitons

attached to dorsal of pons/medulla

connected to brainstem through 3 penducles

(superior, middle, inferior)

-Participates in the coordination of movements (time b/w; scale; does not initiate)

-regulation of equilibrium

Pons functions

major bridge b/w cerebellum & brainstem by cerebellar penducles

ascend/descend fibers

contains cranial nerve nuclei

& sensory motor regulating fibers

Medulla Oblongata Functions

ascend/descend fibers

where decussation takes places

Contains 3 important cranial nerve nuclei

Regulates respiration, phonation,

heart beat, and blood pressure

Spinal Cord

links body w/ CNS

regulates reflexes

Types of Neuroglial Cells  in CNS (1)

 ** Astrocyte **

Physical and nutrition support for neurons

1. clean up debris

2. transport nutrients to neurons

3. hold neurons in place

4. contribute to BBB

(selects permeability of capillaries and arteries)

Types of Glial cells in CNS (2)

Microgia

-digest parts of dead neurons

-form scar tissue

-reduce damage to other neurons

-clean up debri

Types of Glial cells in CNS (3)

Oligodendroglia

forms myelin sheath

Types of Glial cells in CNS (4)

Ependymal cells

primarily form the inner surface of the ventricles

Types of Glia Cells in PNS

Schwann cells

forms myelin sheath

Types of Glia Cells in PNS (2)

Satellite Cells

-physical support to neurons

-sensory neuron cell body

Neoplasm (2 types and 4 causes)

brain tumor

1) Glimos: starts in spine or brain

2) Astrocytoma: orignate in astrocyte glial cell

Causes: aphasia, disphagia, dysarthria, cognitive impairments

3 Types of Muscles

Smooth: involuntary movements; digestive system, respiratory passages, intestinal tracts, blood vessels.

Cardiac: involuntary; pumps blood from heart; controled by ANS cardiovascular reflexes

Striated/Skeletal: under control; motor

divided into sarcomeres

thick filamints:myosin

thin filaments: actin

Motor unit

1. alpha motor neuron (large multipolar) located in ANTERIOR HORN of spinal cord 

2. muscles cells it inervates

neurotransmitters

action potential

electrical impulse representing a transient fluctation in membrane potentials which are propagated along axonal process to activate postsynaptic terminals

15mv triggers

resting membrane potential

membrane potential of -70mV not generating action potentials

polarized, negative inside, positive outside

sodium-potassium pump (3 Na out for 2 K in)

Grated Potential

stimulation by another neuron or special receptors

dendrites produce this and resting membrane starts to change

1. chemical

2. mechanical (pain, temperature)

3. light (photreceptors)

4. acoustic (hearing)

depolarization

repolarization

hyperpolarization

into action potential, less negative

Na channels open, Na flows in

-------

into resting, Na closes, K opens, K flows out

-------

more negative, undershoot, less excitable

Synapse (3 parts)

1. presynaptic ternminal: terminal buttons, activate synaptic vesicles filled w/ neurotransmitters
2. synaptic cleft: diffuse in space
3. postsynaptic:  dendrites contain receptors for the neurotransmitters

CLINICAL EXAMPLE of loss of transmitter

Myasthenia Gravis: a chronic autoimmune neuromuscular disease (muscle weakness, fatigue)

a. impairment in loss of acetycholine transmitter at neuromuscular juncion

b.   muscles of eye, facial expression, chewing, talking, swallowing may be effected

**acetycholine regulates forebrain activity inhibits basal ganglia activity

Protection of CNS

Bony Shell

Minings (Pia, Arachnoid, Dura)

-subarachnoid (CSF)

Blood Brain Barrier: protect from chemicals, allows certain

Sensory Tracts (3) in the midbrain

superior colliculus

-vision

inferior colliculus

-hearing

periaquductal gray matter (PAG)

-gray matter around cerebral aqueduct

Motor tracts in Midbrain????

cerebral penduncles

white matter fibers--> corticospinal tracts

rubrospinal tract

red nucleus

Clinical example of deteriorated substantia nigra

Parkinson's disease

barely black anymore

Pontine nuclus

3 Cranial nuclei in Medulla for relex centers

1. cardiac center: regulates heart beat

2. vasomotor center: monitors/alters diam. of blood vessels

3. respiratory center: controls rhythm/rate of breath

Structure of cerebellum

convolutions: folia

midleine: vermis

3 lobes

1. anterior lobe

2. posterior lobe

3. flocculonodular lobe

The error control device

cerebellum

compares sensory to efferent commands, corrects output based on feedback

Cerebellar pathology

Ataxia

Dydiadochokinesia

Dysarthia

Dysmetria

Intention tremor

Cerebral Palsy

Hypothalamus

Thalamus

Subthalamus

Epithalamus

Hypothalamus communication

w/ brainstem, brain, spinal cord

1. Neural: controls ANS by efferent proections to brainstem/spinal cord

2. Hormonal: liks NS to endocrine system via pituitary glad

Epithalamus

1. pineal gland

2. habenular nuclei

Subthalamus

linked to basal ganglia system

helps with motor control

Ventricles (3 places it flows)

Two lateral

3rd: b/w two thalami

4th: b/w pons and cerebellum

>circulates cerebrospinal fluid (CSF)

1. interventricular foramen: 1,2,3

2. cerebral aqueduct: 3, 4

3. subarachnoid space: 4

Cerebrospinal fluid (CSF)

produced by choroids plexus

replaced 3x a day

Clinical example: CSF pathology

CSF Hydrocephalus

water in the brain

dissociation b/w absorbtion rate of CSF

too much, added pressure, enlargement, damage

Multipolar Neurons (2 types)

Golgi Type 1 Projection Neuron

Golgi Type 2 Local Circuit Neuron