B&B

Central NS

Consists of brain and spinal cord

Encased within skull and spinal column

Peripheral NS

Consists of nerves and most sensory organs

Comprised of nerve tissue located outside of brain and spinal cord

Sensory neuron

Detects change in internal or external environment and sends info to CNS

Motor neuron

CNS, Controls contraction of a muscle or secretion of a gland

Interneurons

Located entirely within CNS

Soma:

The cell body which contains the nucleus

Dendrites

Branched structure attached to the soma of neuron, receives info from terminal button of OTHER neurons

Axon hillock

Site of summation for incoming information (action potential)

Axon

Thin, long cylinder, conveys info from the soma to its terminal buttons

Axon terminal/terminal buttons

Bud at the end of branch of axon, forms synapses with another neuron; sends info to that neuron

Synapse

A junction between the terminal button of an axon and the membrane of another neuron

Basic steps for neuron communication (4 steps)

Input, integration, conduction, output

End point of axon

Transforms electrical signal from axon into a chemical signal sent across synaptic cleft

Neurotransmitter

Chemical that is released by terminal button; has an excitatory or inhibitory effect on another neuron

Bipolar neuron anatomy

Neuron with one axon and one dendrite attached to soma (sensory)

Multipolar neuron anatomy

One axon and many dendrites, most common in CNS

Unipolar neuron anatomy

One axon attached to soma, axon divides with one branch receiving sensory info and the other sending the info to CNS (somatosensory, touch, pain)

Membrane

A structure consisting primarily of lipid molecules that makes up the outer boundary of a cell

Cytoplasm

The viscous, semi-liquid substance inside the cell

Nucleus

Contains all genetic info that the neuron needs to function (chromosomes)

Mitochondria

Double membrane

Contains their own DNA and replicate independently of cells

Converts nutrients into ATP

Adenosine triphosphate

Cells main energy source

Endoplasmic reticulum

Storage reservoir and channel for transporting chemicals through the cytoplasm

rough vs smooth ER

Rough: produce proteins that are either transported out of cell (attached) or distributed around cytoplasm (free-floating)

Smooth: lipids produced here

Golgi apparatus

Generates and secretes neurochemicals (exocytosis)

Wrapping and packing

lysosome

Organelle surrounded by membrane; contains enzymes that break down waste products

Cytoskeleton

Matrix of protein strands that give neuron its shape

Microtubule

Long strand of bundles made of protein filaments arranged around hollow core, part of cytoskeleton involved in transporting substances from place to place within the cell

Axoplasmic transport

Active process where substances are propelled along microtubules that run the length of an axon

Anterograde

In a direction along an axon from the cell body to the terminal buttons. Very fast (500 mm/day)

Retrograde

Direction along axon from terminal buttons toward soma. Slower, half the speed.

Kinesin

Molecules that walk like an inchworm down a microtubule, carrying their cargo from soma to axon terminals

grey vs white matter- building blocks of NS

Neurons make up grey matter, electro-chemical transfer of info from one region to another

Glia make up white matter, Greek for glue, outnumber neurons 10:1, supporting cast

Function of glia

Modify chemical milieu

Guide neurons to find final site during development

Remove dead neurons after damage

Phagocytosis

Serve some nutritive needs

Maintain blood brain barrier

Astrocytes

Type of glial cell, surround neurons and contact blood vessels via end-feet

Allow transmission of ions across vascular wall and forms BBB

provides physical support

Provides nourishment

Maintain chemical milieu surrounding neurons

Astrocyte function in relation to glucose

Supply neurons with glucose from capillaries

Glucose processed within astrocyte to produce lactate which is released into extra cellular fluid surrounding neuron

Lactate taken up by neuron for use by mitochondria

Oligodendrocytes

Produce myelin, the fatty sheath that covers axon- can myelinated multiple axon in CNS

producing up to 50 segments

Not all axons have myelin

Schwann cells

Involved in production of myelin in PNS, only myelinates a single nerve

Also digests dead axons and provides process for regrowth

Nodes of Ranvier

Unmyelinated areas of axon

Function of myelination

Speeds up conduction of neural signal

What is the fibre tract

When a group of cells send their signal to one specific place (corpus callosum)

What makes white matter white

The fat in myelin

What is the function of blood-brain barrier

Regulated chemicals that can enter the CNS from blood, prevents many toxins from infecting brain

Selectively permeable

Area postrema

Maintains a weak BBB which allows for detection of toxins in blood and triggers vomiting response

What can break down the BBB

Hypertension

Developmental issues

Hyperosmolarity

Radiation

Infections

Trauma, ischemia, inflammation, pressure

Microglia

Damaged neural tissue is invaded by microglia which then remove dead cells

Protect brain from invading microorganisms

Membrane potential

electrical charge across cell membrane,

Difference in electrical potential inside and outside cell

Resting membrane potential

Membrane potential of neuron when it’s not being altered by excitatory or inhibitory postsynaptic potentials

Action potential

Brief electrical impulse that provides the basis for conduction of info along axon

Hyper polarization

Increase in membrane potential of cell relative to normal resting potential

Depolarization

Reduction of the membrane potential of a cell from its normal resting potential

Threshold of excitation

Value of membrane potential that must be reached to produce an action potential

How many mV in resting potential, action potential, threshold and hyperpolarization

Resting, -70

Action, +40

Threshold, -55

Hyper, -90

Diffusion gradient

Movement of molecules from a region of high concentration to low

Electrostatic gradient

Molecules can carry charge (ions)

Move towards areas of unlike charge

Dynamic equilibrium

Gradients can balance one another

Firing rate

Where valuable info, representing the strength of a response to stimulus is conveyed

Saltatory conduction

Conduction of action potential by myelinated axons, jumping from one node of ranvier to the next

Phagocytosis vs apoptosis

P, macrophages gone wild

A, cell death

Axodendritic

Synapse on the dendrite of neuron

Axosomatic

Synapse on soma

Axoaxonic

Synapse on axon

Two main types of postsynaptic receptors

Ionotropic and metabotropic

Reuptake

Rapid removal of neurotransmitter from synaptic cleft

Spatial integration

Equal excitatory and inhibitory input will cause no change

Temporal integration

Ripples combine to make bigger ripples

Autoreceptros

Respond to neurotransmitters they produce

Regulate synthesis and release of other transmitters

Metabolic

Usually inhibitory

Contralateral

Opposite side

Ipsilateral

Same side

Proximal

Close to body

Distal

Far from body

Efferent vs afferent signal

E- away from CNS

A- toward CNS

Parasympathetic

Inhibitory, rest and digest

Constricts pupils

Stimulates saliva production

Constricts bronchitis

Slows heart

Stimulates urination

Promotes erection

Sympathetic division

Stimulation, fight or flight

Dilates pupils

Inhibits saliva production

Dilates bronchi

Accelerates heart

Stimulates epinephrine and norepinephrine release

Inhibits stomach, pancreas and intestines

Inhibits urination

Promotes ejaculation and vaginal contractions

Meningitis

Infection of the meninges increases pressure on brain

Encephalitis

Infection of the brain itself

Cerebrospinal fluid

Brain is surrounded by CSF

Ventricles (filled with csf) are continuous with the outer supply

Csf supports the brain

Provides nutrients, removes waste, helps maintain BBB

Ventricular system and CSF-

How do nerves communicate with CNS

Communicates with body via nerves that connect with the brain (cranial nerves) or the spinal cord (PNS)

Cranial nerves

Olfactory

Optic

Oculomotor

Trochlear

Trigemental

Abducens

Vestibulocochlear

Glossopharyngeal

Vagus

Accessory

Hypoglossal

Medulla oblongata

Many cranial nerves attached to medulla

Reticular activating system- arousal, attention, sleep-wake cycle

Motor fibers cross to contralateral side

Controls reflexes, respiratory and heart rate

Damage can be fatal

Cerebellum

Fine motor control

Balance

Neuroimaging suggests it plays a role in many cognitive processes

Ipsilateral motor organization

Pons

Main connection between cortex and cerebellum

Vestibular functions

Sleep and arousal

Contains superior olive

Superior olive

Point at which info from both ears coverages, important for localization of sound

Midbrain 2 important structures

Superior colliculus, rapid eye movement

Inferior colliculus, auditory equivalent of SC

Hypothalamus

Group of nuclei

Maintains equilibrium

Ventrimedial lesions affect regulation of food intake

Regulate body temp

Regulate hormones

Thalamus

Group of nuclei

Sensory and motor relay center

Lateral and medial geniculate nucleus

In thalamus

Lateral-relays info from retina to visual cortex

Medial- relays info from auditory pathways to cortex

Basal ganglia

Group of nuclia that are functionally related

Primarily involved in motor control

Caudate nucleus, globes pallidus, putamen

Limbic system structures

Hypothalamus

Amygdala

Cingulate cortex

Anterior thalamus

Mammillary bodies

Hippocampus