Intro to neuro exam 1

Reticular Theory

nerves communicate through a continuous nerve net - Camillo Golgi

Golgi Method

stains neurons - silver solution that stains 1% of neurons in their entirety

Early idea about nervous system

central dogma of biology

central dogma of biology

cells are structural units of all living matter

Did early anatomists believed cell theory applied to brain?

no

Camillo Golgi

reticular theory

Santiago Ramon y Cajal

Father of modern neuroscience - contributed to neuron doctrine and principle of dynamic polarity - identified neurons and glia - awarded nobel prize

golgi method by cajal provided evidence against…..

….against the reticular theory

cajal showed….

no continuity between neurons

The Neuron Doctrine

The principle that individual neurons are the units and signaling elements of the nervous system - neurons are discrete entities not a continuum

Neuron Doctrine also showed…

…showed that neural processes (dendrites and axons) grow from cell body when neurons are isolated in culture - axons extend to target neurons or tissue

neuron doctrine also shows….

…shows synapses and gaps between neurons

Brainbow

Process which stains individual neurons using genetically encoded fluorescent proteins - 100+ colors

Two major components of nervous system

CNS and PNS

CNS

protected inside bone (skull and vertebral column)

PNS

extends beyond (or exists entirely outside of) the bony skull and vertebral column

neurons

the building blocks of the nervous system

Principle of dynamic polarity

electrical signals within a neuron flow in one direction - Cajal principle

---

—> direction of signal

Dendrites

INPUT

Soma

INTEGRATION

Axon

PROPAGATION

Terminal

OUTPUT

types of neuron signaling

electrical and chemical signaling

intracellular signaling

signaling occurs within a neuron

Intercellular signaling

between neurons or between neurons and their non-neuronal targets

are neurons cells?

yes

elements of neurons

plasma membrane, cytosol, cytoskeleton, neurofilaments, nucleus, ER, ribosomes, golgi, vesicles

Vesicles

used by the cell to organize cellular substances

Synaptic Vesicle

store and release neurotransmitter

ectosomes

fuse with membrane to deliver proteins

endosomes

remove protiens from membrane

lysosome

breakdown waste and debris

mitochondria

generate ATP - storage, buffering, release of Calcium - concentrated in axon terminals - ATP required to release neurotransmitter

Number of dendritic branches correlates with…

…with the number of inputs

Spines

specialized location for synapses

spines increase….

…increase the number of input locations

Axons

Propagate electrical signals between neurons and form presynaptic terminals of synapses

Optimizations for speed

myelin and nodes of ranvier

Myelin

wraps axon like insulation - keeps electricity from escaping

nodes of ranvier

breaks in myelin with concentrated channels - depolarized region

Structure determins….

…function

Sensory receptor neurons

transduce environmental signal into a neural signal

transduction

change sensory input to electrical signals

examples of sensory receptor neurons

rods, cones, olfactory receptor, taste bud, hair cell, pain-temp-pressure sensors

Projection neurons

communicate with other neurons located in a different or distant CNS region

1) between brain areas

2) between brain spinal cord and sensory or motor structures

Motor neuron

contract muscles or control glandular/endocrine secretion

interneurons

communicate with other neurons located in the same or nearby CNS region - local connections within a brain area or spinal cord

excitatory

GO

inhibitory

STOP

Glial cells

“glue” - thought to hold brain together - non neural cells - more numerous then neurons - support system for neurons

Glia has

standard cellular features, expresses glia fibrillary acid protein (GFAP)

Astrocytes

“star like” - only in CNS - maintain proper extracellular chemical environment necessary for cellular signaling (for Ca2+) - have end feet that interact with capillary cells to maintain TIGHT JUNCTIONS

Oligodendrocytes

in CNS - myelinates SEVERAL parts of CNS axons

Schwann Cells

in PNS - myelinates one part of a single PNS axon

Oligodendrocytes and Schwann cells

lays down multiple layers of myelin and retains stem cell properties even in mature nervous system and can divide to produce new oligodendrocytes or schwann cells

Microglia

scavenger cells that remove debris from sites of injury - modulate inflammation, cell survival and cell death

*immune cells of brain

*shape-shifting according to function

meninges

3 layers of tissues that provide protection to the brain and spinal cord

Dura mater

outermost meninges layer - tough and leathery

Arachnoid mater

middle meninges layer - delicate and impermeable

subdural space

space separating dura and arachnoid mater

subarachnoid space

space separating arachnoid and pia mater and is filled with cerebrospinal fluid

pia matter

innermost meninges layer - adheres to surface of brain and covers gyri - very thin and glossy

Meningitis

infection/inflammation of the meninges

viral meningitis

• scary but treatable inflammation of meninges

bacterial meningitis

more serious, often fatal but immunization is available

Ventricular system

series of interconnected, fluid filled spaces within core of CNS

Cerebralspinal Fluid (CSF) process

1) derived from CHOROID PLEXUS secreting CSF into ventricles

2) CSF leaves ventricles through several FORAMINA (openings/passenges) into the SUBARACHNOID space surrounding brain and spinal surface

3) CSF drains out of subarachnoid space through ARACHNOID VILLI/GRANULATIONS into subdural sinuses and back into general blood circulation

choroid plexus

Specialized vascular tissue within walls of ventricles; filters capillary blood and secretes the CSF product into the ventricles

Purposes of CSF

1) Buoyancy

• brain can be dense without being damaged by own weight

2) Protection

• CSF protects brain tissue from everyday injury by providing fluid buffer that acts as shock absorber

does ventricular system extend down to spinal cord?

yes - it protects entire central nervous system

Spinal tap/Epidural

• CSF is collected for testing (meningitis)

• drugs can be administered through CSF

Hydrocephalus (water head)

condition caused from block in CSF drainage

How is hydrocephalus treated?

by a surgical implantation of a shunt into a vein or abdominal cavity - very effective and high success

Blood Brain Barrier

protects the brain from substances in the blood - formed by TIGHT JUNCTIONS between capillary endothelial cells within the brain and spinal cord - maintained by ASTROCYTES end feet

Brain capillaries are…

…are NON-FENESTRATED meaning they have TIGHT JUNCTIONS that form a barrier to protect brain

Rest of body’s capillaries are…

…are FENESTRATED (no tight junctions)

Blood Brain Barrier also….

1) helps keep blood cells, proteins, toxins, hormones, bacteria out of brain tissue to preserve optimal balance of extracellular chemical composition

What goes through Blood Brain Barrier…

….anything that is small and lipid soluble or that has specific transporters (O, CO2, gases, glucose, insulin, amino acids, alc, nic, cocaine, psycoactive drugs)

Are Circumventricular organs protected by Blood Brain Barrier?

no because they are allowed access to blood to detect toxins

rostral

forward

caudal

behind or down

Anterior

in front of

Superior

above

posterior

behind

inferior

below

White matter

myelinated axons

gray matter

consists mostly of cell bodies and dendrites

Spinal cord

• transfers info from CNS and PNS

• pairs spinal nerves

• sensory info enters DORSAL (back)

• motor info exits VENTRAL (stomach)

ganglion

collection of somas

root

axons entering and exiting the spinal cord

Brainstem includes..

…includes medulla, midbrain and pons

• all levels contain sensory + motor axons

midbrain

superior and inferior colliculi: localization of visual and auditory stimuli

pons

includes axons allowing cerebellum to communicate with brainstem and cerebral cortex

• includes fourth ventricle

medulla

includes neurons that maintain normal, rhythmic breathing

Cerebellum

• Motor planning - aids planning complex movements

• Motor learning - error correction when learning movement, synapses change w experience

Diencephalon components…

Thalamus and Hypothalamus

Thalamus

Relay for info going to and coming from the neocortex

hypothalamus

regulates autonomic nervous system and regulates hormone release

Cerebral Cortex (neocortex)

• processing of sensory input

• initiation/planning of movements

• “high-order” functions including memory, cognition and language