Introduction to Psychology

Brain and Behaviour

Neuroscience

Plan for Today

• Biological bases of behavior

• Communication in the nervous system

• Organization of the nervous system

• Researching the brain

Components of the Neuron– Dendrites: receive

information from other neurons

– Cell body: creates transmitter molecules

– Axon• Myelin insulates the nerve cell,

speeds up conduction of nerve messages

• Terminal buttons of the axon release transmitter

Graded Potentials• Stimulation of the nerve

membrane can open ion channels in the membrane

• NA+ ions flowing in will depolarize the membrane (movement from -70 mV to say -60 mV

• K+ ions flowing out of membrane will hyperpolarize the membrane (-70 mV to say -90 mV)

The Action Potential• Graded potentials are generated at the dendrites and are conducted along the membrane

to the axon hillock• If the summated activity at the axon hillock raises the membrane potential past

threshold, an action potential (AP) will occur

• During the AP, NA+ ions flow into the cell raising the membrane potential to +40 mV, producing the spike– The restoration of the membrane potential to -70 mV is produced by an opening of channels to K+– The AP is conducted along the axon toward the terminals

Details of the Synapse

Neurotransmitters

• Acetylcholine (Ach)

• Monoamines:

- epinephrine and norepinephrine

- serotonin

- dopamine

• GABA

• Glutamate

Overview of the Nervous System

Autonomic Nervous System

• The Autonomic Nervous System (ANS) has two divisions:– Sympathetic: Emergency system– Parasympathetic: Vegetative functions (e.g.

digestion)

• The two systems often act in opposition (as in the control of heart rate)

• Can act in concert (as in the control of sexual reflexes)

Autonomic Nervous System

Midline View of Human Brain

Medulla: Controls heart rate, respirationCerebellum: Coordinates smooth movements, balance, and posturePons: Involved in the control of sleep

Limbic System Functions

• Septal area is involved in pleasure and in relief from pain

• Amygdala is involved in learning and recognition of fear

• Hippocampus is involved in memory

Cerebral Cortex

• Functions of cerebral cortex:– Provides for flexible control of patterns of

movement– Permits subtle discrimination among complex

sensory patterns– Makes possible symbolic thinking

• Symbolic thought is the foundation of human thought and language

The Cortical Lobes of the Human Brain

Frontal Lobe Damage and Personality

• Frontal lobes are involved in movement, attention, planning, memory, and personality.

• Frontal lobe function in personality is evident in the case of Phineas Gage– Gage suffered frontal lobe damage after an accident

involving a dynamite tamping rod

– Gage was a railroad supervisor prior to the damage; after the damage he became childish and irreverent, could not control his impulses, and could not effectively plan.

Cerebral Lateralization

• The structures of the cortex and sub-cortex appear to specialize in function:– Hemispheric Specialization

• Left hemisphere is dominant for language, logic, and complex motor behavior.

• Right hemisphere is dominant for non-linguistic functions including recognition of faces, places, and sounds (music)

• The hemispheric specializations are evident from studies of– Damage to one hemisphere (I.e. Broca’s area)– Split-brain subjects

The Split-Brain Study• Information from the one visual field is usually

transmitted to the opposite visual cortex• The corpus callosum serves to integrate the two

hemispheres• Cutting the corpus callosum can result in

information reaching only one hemisphere– Language is a left-hemisphere function– Information reaching the left hemisphere will be

reported by the subject, but not information reaching the right hemisphere

Split-Brain Studies

(Figure adapted from Gazzaniga, 1967)

The Endocrine System

• Glands that secrete hormones into the bloodstream to help control bodily functioning

• Hypothalmus connected to pituitary gland (master gland)

- adrenal glands = fight or flight

- Gonads = secondary sex characteristics

Endocrine Systems

• Endocrine glands release hormones into blood stream– Have effects at diffuse target sites

throughout the body– Hormones bind to receptors – Hormones can have organizational

effects (permanent change in structure and function)

– Hormones can have activational effects:

• Lack of testosterone reduces sexual behavior