BIOL 216 Topic 6

why do evolving animals need a more complex nervous system

To compete

Escape danger/predators

Find food, shelter, mates

cephelization

the development of an anterior head where sensory organs and nervous tissues are concentrated

nerve nets

loose mesh of neurons found in radially symmetrical animals

nerve cord

bundle of nerves which extend from the central ganglia to the rest of the body

ganglia

functional clusters of neurons

bilateral symmetry

body parts are mirror images on either side of the midline

organization of the nervous system, such as paired nerves linking lobes in brain with specific muscles and receptors

how is bilateral symmetry useful?

allows for sophisticated sensory processing

how is the nervous system refined?

differential gene expression that varies spatio-temporally

what does the forebrain in the 4-week old embryo develop in to?

at the 5-week embryo, the forebrain becomes the telencephalon and diencephalon

what does the midbrain in the 4-week embryo develop in to?

at the 5-week embryo, the midbrain becomes the mesencephalon

what does the 4-week embryo hindbrain develop in to?

at 5 weeks, the hindbrain develops in to the metencephalon and myelencephalon.

telencephalon (cerebrum) in adult

higher functions, such as thought, action, and communication

thalamus in adult

coordinates sensory input and relays it to cerebellum

developed from diencephalon

hypothalamus in adults

center for homeostatic control of internal environment

developed from diencephalon

midbrain in adults

coordinates involuntary reactions and relays signals to telencephalon

developed from mesencephalon

cerebellum in adults

integrates signals for muscle movement

developed from metencephalon

pons in adult

center for information flow between cerebellum and telencephalon

developed from metencephalon

medulla oblongata

controls many involuntary tasks

developed from myelencephalon

functions of the brain

• receive information

• integrate information

• send out information

• store information

• retrieve information

left brained

logical/objective

right brain

creative/intuitive

blood brain barrier (BBB)

a separation of circulating blood and CSF

occurs along all capillaries and consists of tight junctions around the capillaries that do not exist in normal circulation

uses endothelial cells

endothelial cells

restrict the diffusion of microscopic objects (eg. bacteria) and large hydrophilic molecules into the CSF

• allows the diffusion of small hydrophobic molecules (o2, hormones, CO2)

paracellular pathway

substances to pass through the intercellular spaces between cells, across epithelia and endothelia

passive diffusion of lipid soluble molecules

movement of molecules that easily dissolve in lipids (fat-soluble molecules) across a cell membrane without the need for energy

carrier-mediated transport (CMT)

transport mediated by a membrane carrier protein

efflux pump

active transporter in cells that moves out unwanted material (also common in bacteria)

receptor-mediated transcytosis (RMT)

principal pathway for transport of macromolecules essential for brain function across the blood–brain barrier

adsorptive-mediated transcytosis (AMT)

process where molecules, particularly positively charged ones, cross a cell membrane like the blood-brain barrier (BBB) by adhering to the negatively charged cell surface, essentially "sticking" to the membrane, and then being taken into the cell via vesicles, allowing for transport across the barrier and into the brain tissue

cell-mediated transcytosis

employs specialized cells like macrophages or dendritic cells to facilitate nanovesicle transport across barriers

CSF

• clear colorless fluid

• produced in the choroid plexus

• found in brain and spinal cord

• circulates nutrient and chemicals filtered from the blood and removes waste products from the brain

• occupies the subarachnoid space

choroid plexus

a complex of glial cells called ependymal cells

subarachnoid space

the space between the arachnoid mater and the pia mater and the ventricular system

functions of csf

• provides chemical balance

• provides buoyancy and support to the brain against gravity

• protect the brain from striking the cranium when the head is jolted

buoyancy

protects the brain since the brain and CSF are similar in density; this makes the brain float in neutral buoyancy, suspended in the CSF

meninges

layers of connective tissue (membranes) covering the brain and spinal cord (3)

what are the three connective tissue layers

pia, arachnoid, dura mater

function of the meninges

provide structural support for blood vessels (notice tubes), serve as a pad between brain and skull

ventricular system

cavities in the brain filled with CSF

what are the four ventricles

two lateral, third ventricle, fourth ventricle

what is the function of the ventricle system?

•These structures are responsible for the production, transport and removal of cerebrospinal fluid

how does the ventricle help prevent brain injury?

helps with shock absorption, allows for some swelling

forebrain

forms the cerebrum

gives rise to telencephalon and diencephalon

cerebrum

left and right hemisphere

made from telencephalon

diencephalon

creates thalamus and hypothalamus

left hemisphere

responds to sensory signals from the right side of the body and controls movements on right side of body

right hemisphere

responds to sensory signals from the left side of the body and controls movements on the left side of the body

what connects the hemispheres?

corpus callosum

enables the exchange of information between the hemispheres

corpus callosum

consists of about 200 million axons that interconnect the two hemispheres. the primary function is to integrate motor, sensory, and cognitive performances between the cerebral cortex on one side of the brain to the same region on the other side

left hemisphere

focus on details (such as recognizing a particular face in a crowd); spoken and written language, abstract reasoning, math

broca’s and wernicke’s areas here

right hemisphere

focus on broad background (such as understanding the relative position of objects in a space); intuitive thinking, conceptualization, music, art, etc

lateralization

difference in function between the left and right hemisphere

cerebral cortex

outermost thin layer of grey matter (in mammals, comprised of 6 layers of neurons, 2-4mm think in humans) covering a core of white matter

convoluted (folds) to increase surface area

regulates cognitive functions such as thinking, learning, speaking, remembering, and making decisions

grey matter

neuron cell bodies and dendrites

white matter

axons (many axons have myelin sheaths)

primary somatosensory area

receive and integrate sensory info

in cerebral cortex

primary motor area

are involved in the planning, control, and execution of voluntary movements

in cerebral cortex

association areas

broca’s, wernicke’s, etc

integrate sensory info, formulate responses, relay responses to motor area

in cerebral cortex

frontol lobe

executive function

thinking, organizing, planning, problem solving, memory, attention, movement

temporal lobe

deals with senses of smell, sound, and the formation and storage of memories

runs along the side of the brain under the frontal and parietal lobes

parietal lobe

sits behind the frontal lobe

deals with perception and integration of stimuli from the senses

occipital lobe

back of brain

concerned with vision