Ch 2

Complex network of cells specialized to perform three basic functions:

• 1. detection of sensory stimuli
• 2. information processing (perception, analysis, memory storage and retrieval)
• 3. generating responses and transmitting them to muscles, glands, and organs

Made up to two major branches:

• 1. central nervous system (cns) - nerve tissue encased within the bony protection of the spine and skull
• 2. peripheral nervous system (pns) - all the nerve tissues laying outside the cns

Serves as the command center of the nervous system, made up of two major compnoents:

• 1. spinal cord - main pathway connection the pns and the brain
• 2. brain - evaluation and analysis of sensory input, decide on appropriate response, transmit responses

Consists of several distinct parts: hindbrain, midbrain, and forebrain

Posterior (or caudal): "in back of"

Superior (or dorsal): "above"

Anterior (or vostral): "in front of"

Interior (or ventral): "below"Lateral: "to the side"Medial: "toward the middle"

Brain Stem: two-way information highway; basic life support functions; key roles in consciousness and REM sleep

Cerebellum: coordination of movement; balance and posture; integration of sensory and motor functions; certain memory and cognitive functions

• Limbic System: generating emotions; learning and memory; sexual and social behavior; biological rhythms
• --includes thalmus, hypothalmus, nucleus accumbens, amyfdala, septum, cingulate gyrus, hippocampus

• Basal Ganglia: initiating and controlling movements
• --includes caudate nucleus, putamen, globus pallidus, and several other structures deep inside the brain

Neo cortex = "thinking cap", responsible for all higher mental functions

• Divided into two large hemispheres (left and right), which are further divided into four functions:
• 1. occipital (back of brain) - visual processing
• 2. parietal (top rear area) - processing body sensations
• 3. temproal (lower side of each hemisphere) - hearing, emotions, language
• 4. frontal (front of each hemisphere) - emotional control, all behavior

Sensory nerves: detect stimuli from outside the body and convey this information to CNS

Motor nerves: convey commands from CNS to all muscles and organs of the body

Spinal nerves: 31 nerves, receives sensory input (through back) or conveys motor output (through front) to a specific body part

Cranial nerves: 12 nerves, enter brain directly, handle sensory and motor function in head and face

Somatic nervous system: sensory nerves that detect internal and external stimulation and sends ingo to the CNS; mostly under voluntary control

• Autonomic nervous system: nerves reach out to every part of the body to regulate ongoing activity of muscles, organs, and glands; mostly automatic
• --includes sympathetic nervous system (fight or flight) and parasympathetic nervous system (rest responses)

About 180 billion in the brain; responsible for everything you do

Receive, process, and transmit info to each other

When neurons die, new ones generally do not develop to replace them, except in the hippocampus; when we are born we have almost all the neurons we will ever have; brain compensates for lost neurons by creating more connections (synapses) between live neurons

Each neuron has one specific job; neurons with similar jobs form networks with each other to perform tasks (ex. memory, emotion); the possible number of interconnections exceeds the number of stars in the known universe!

The vast processing capacity of the brain is only possible because of these complex networks

10x more than neurons!

Do not transmit info and are constantly replaced

Four types...

Starlike shape, largest, most numerous

Help form scar tissue; wrap themselves around capilaries to protect them; remove waste and dead cells by digesting them; help regulate levels of certain chemicals; may help communication between neurons

Form myelin

Ogliodendroglia - CNS

Schwann cells - PNS

Found in ventricles (tissue that lines fluid-filled cavities in the brain)

Form and secrete cerebrospinal fluid (CSF)

5-20% of glial cells, distributed throughout CNS

Believed to destroy foreign organisms, remove toxic substances, and promote tissue repair by secreting nerve growth factor (NGF)

Separates neurons from each other

Allows necessary substances to enter (from surrounding extracellular fluid) and exit

"Soma"

Contrains cell's nucleus (DNA/RNA) and other organelles (mitochondria, Golgi appartus, ribosomes)

Uses protien to work

Tiny, multiple busy "branches" that extend from the cell body

Collectively called the dendrite tree; vary greatly in size, shape, and configuration depending on the type of neuron; account for 90% of the neurons total surface area

Long, wire-like fiber that sends messages; 1 per neuron

1. Axon hillock - where long fiber starts

2. Axon fibers - carries messages at up to 200mph (depending on size of axon and myelin content); may split into axon collaterals

3. Axon terminals - bulbous, found at the end of the axon collaterals

Junction between neuron and dendite of another neuron

Messages cannot cross the synaptic gap, so they are helped by neurotransmitters from the synaptic vesicles that "jump" the gap and bind with the receptors on the dendrites of the other neuron

Cream-colored fatty substance that serves as "insulation" for axons

Plays essential roles in transmitting signals: the thicker the myelin sheath, the faster signals are transmitted; icreaces the "fuel efficiency" of neurons by decreasing the metabolic demands involved in transmitting messages

"Afferent" neurons

Receive input from sensory receptors and convey info to CNS and brain

"Efferent" neurons

Largest in the nerve system; have very long axons and extensive dendrites

Convey commands from brain and spinal cord to muscle fibers or glands

"Association" neurons

More than 97% of the neurons in the brain

Receive and process input from other neurons and convey signals to other neurons

Refers to brain tissue composed of closely packed groups of neuron cell bodies and their dendrites; found in several areas of the brain, within the inner core of spinal cord, and parts of the PNS

Primary role = information processing

Brain issue found in the cerebral cortex

Responsible for the brain's highest levels of mental processing, ex. speech, language, cognition, personality

Within the CNS

Formed by closely packed clusters of neuron cell bodies and their dendrites

Function as specialized "processing plans" which form sub-cortical structures, ex. thalmus, hypothalmus

Within the PNS

Composed of neurons with similar specializations and tasks to perform

Most of the brain's interior; composed of large numbers of myelinated axons arranged in near-parallel formations called fiber tracts

Function as information "superhighways"

Carry signals from neuron to neuron; three types

• 1. projection tracts: fan out from one brain region to another, up and down
• 2. association tracts: link different parts of the same side of the brain, front to back
• 3. commisures: carries signals to the left and right side of the brain

1. Corpus Callasum: largest (200 million axons), major information "superhighway" between left/right halves of the brain

2. Anterior Commissure: just below front of the CC, major "superhighway" between left/right temporal lobes

3. Massa Intermedia: connects the left/right halves of the thalamus