Neuroscience and Behavior

ObjectivesGain a general understanding of the

nervous systemGain knowledge of the structure and

function of the neuronNavigate your way around the major

brain areas and understand their function

Nervous System Hierarchy

Central nervous systemBrain

◦~2% of body weight, uses ~20% of resources

◦Composed of bunches of neurons, which form nerves

Spinal cord◦Complex tangle of nerves that stretch from

brain to tailbone◦Collects & transmits info between brain and

peripheral nervous system◦Also initiates reflexes: automatic

responses to an event

Peripheral Nervous System

PNS links the CNS to the organs, muscles, and glands of the body

PNS has two parts◦Somatic (SNS): nerves controlling voluntary

muscle movements◦Autonomic (ANS): controls glands, organs,

blood vessels ANS has two parts

Sympathetic: arouses body to prepare for action (fight or flight)

Parasympathetic: slows down body to reserve energy

Sympathetic and Parasympathetic

The NeuronAll brain activity originates with the neuronThe messengers of the brain-world

◦ These cells receive signals from neurons or sense organs, process the signals, and send them to other neurons, muscles, or organs

Three types◦ Sensory: respond to sensory organ input◦ Motor: send signals to muscles to control movement◦ Interneurons: the go-between of sensory and motor

neuronsWe have about 100 billion neurons

◦ Most, but not all, can be re-grown (severe spinal cord injury vs. cutting your finger)

The Neuron

The Neuron: StructureCell body: houses nucleusCell Membrane: skin of the cellAxon: cable extending from the cell body

◦ Impulse from cell body travels along axon to its end, where terminal buttons release neurotransmitters (chemical messengers), received by other neurons

◦ Axon is covered by myelin sheath, which is composed of a fatty substance that helps impulses travel the length of the axon

Dendrite◦ Branches extending from cell membrane that

receive neurotransmitters from other neurons

The DendriteIncreases receptive surface of the

neuronContacts occur along surface of

dendrite

The AxonAxon hillockMyelin

sheathNodes of

Ranvier◦The points

just between the myelin sheaths

The Neuron in ActionWhen a neuron receives impulses from

other neurons, the cell membrane allows open exchange of positively and negatively charged ions◦Action potential (change in electrical

charge) runs down axon to terminal buttons◦This all starts with the axon hillock – the

gatekeeper of the neuron◦Terminal buttons release neurotransmitters◦Neurotransmitters cross the synaptic cleft

to the dendrite of the receiving neuron

The Neuron in action

Communication in the Neuron

All-or-nothing◦ The action potential either happens or it doesn’t

Non-decremental◦ Action potentials don’t change in amount (voltage)

as they travelRefractory period

◦ Neurons need 2ms to recover before they can transmit again

Threshold◦ The minimum level of stimulation required to

trigger a neural impulse◦ Once you reach the threshold, the action potential

doesn’t get bigger

Several NeurotransmittersAcetylcholine (Ach)

◦ Slows down the body, memory, and attention (involved in Alzheimer’s disease)

Dopamine (DA)◦ Voluntary movement, attention, and learning; high

levels are associated w/ schizophreniaEndorphin

◦ Reduce sensitivity to pain; linked with pleasure (opiate-like)

Serotonin◦ Arousal, sleep; Prozac increases levels of serotonin

Norepinephrine◦ Helps control alertness and arousal; low levels can

depress mood

History of Studying the Brain

Franz Joseph Gall (1758 – 1828)◦Phrenology

The study of the structure of the skull to determine a person’s character and mental capacity

26 ‘organs’ on the surfaceof the brain

History of Studying the Brain

Phrenological Map of the Skull

History of Studying the Brain

Flourens (1794 – 1867)◦Emphasized the importance of

experimental research of the brain◦Carefully controlled experiments on animals

to determine localities of brain and their functions

◦Moved the field of brain research into a more scientific arena

The BrainThree main parts

◦Brain Stem◦Limbic System◦Cerebral Cortex

Areas of the Brain

Brain StemRegion of the brain where the spinal

cord enters the skull and swellsMedulla

◦Regulates heart-rate, breathing, blood pressure, and motor movements

Cerebellum◦Controls skilled motor movements

Brain StemPons

◦Connects the two hemispheres of the cerebellum

Reticular formation◦Sleep (Moruzzi & Magoun, 1961)◦Attention

Thalamus◦Relay center

Filters & organizes information from senses

Limbic SystemHypothalamus

◦Feeding◦Reproductive behavior◦Temperature (Barbour, 1912)

Hippocampus◦Memory

H.M.Amygdala

◦Feeding◦Memory◦Emotion

Cerebral CortexTwo halves, four lobes

◦Frontal lobe Motor cortex

◦Parietal lobe Sensory cortex

Prosopagnosia Unilateral neglect

◦Temporal lobe Auditory areas

◦Occipital lobe Visual areas

Two Cerebral HemispheresContralateral arrangementCorpus callosum

◦Thick band of nerve fibers connecting the hemispheres

◦It’s how the 2 hemispheres communicate

Right-brained vs. left-brained?

OR

Left & Right Functions