Chap 3: Biological Bases of Behaviour

Source: Barron's AP Psychology

Neuroanatomy

Neuroanatomy

The study of the parts and functions of neurons

Neurons

Individual nerve cells

Dendrites

• Root-like parts of the cell that stretch out from the cell body.

• Grow to make synaptic connections with other neurons

Cell Body (Soma)

Contains the nucleus and other parts of the cell needed to sustain its life

Axon

Wire-like structure ending in the terminal buttons that extends from the cell body

Myelin Sheath

A fatty covering around the axon of some neurons that speeds neural impulses

Terminal Buttons

The branched end of the axon that also contains neurotransmitters

Neurotransmitters

• Chemicals contained in terminal buttons that enable neurons to communicate

• Fit into receptor sites on the dendrites of neurons like a key into a lock

Synapse

Space between the terminal buttons of one neuron and the dendrites of the next neuron

Receptor Sites

A place on the dendrites where neurotransmitters fit into

Absolute Threshold

The amount of neurotransmitters needed for firing

Action Potential

When a neuron sends information down an axon, away from the cell body

All-or-none principle

A neuron either fires completely or it does not fire at all

Excitatory Neurotransmitters

Excite the next cell into firing

Inhibitory Neurotransmitters

Inhibit the next cell from firing

Acetylcholine

• A neurotransmitter involved in motor movement

• Lack of acetylcholine is associated with Alzheimer’s disease

Dopamine

• A neurotransmitter involved in motor movement and alertness

• Lack of dopamine is associated with Parkinson’s disease

• An overabundance of dopamine is associated with schizophrenia

Endorphins

A neurotransmitter involved in pain control and addictions

Serotonin

• A neurotransmitter involved in mood control

• Lack of serotonin is associated with clinical depression

GABA

• An important inhibitory neurotransmitter

• Involved in seizures and sleep problems

Glutamate

• Excitatory neurotransmitter

• Involved in memory, migraines, and seizures

Norepinephrine

A neurotransmitter involved in alertness/arousal, can cause depression

Afferent Neurons (Sensory)

Take information from senses to brain

Interneurons

Once info reaches the brain or spinal cord, interneurons take the messages and send them elsewhere in the brain or onto efferent neurons

Efferent Neurons (Motor)

Take information from the brain to the rest of the body

Central Nervous System (CNS)

Consists of brain + spinal cord (all nerves encased in bones)

Peripheral Nervous System

• All nerves not encased in bone

• Somatic and autonomic nervous systems

Somatic Nervous System

Controls voluntary muscle movements

Autonomic Nervous System

• Controls automatic functions of our body

• Controls response to stress

• Contains parasympathetic and sympathetic nervous systems

Sympathetic Nervous System

• Mobilizes body to respond to stress

• Alert system - accelerates some functions (e.g. heartbeat) but conserves resources needed for a quick response by slowing down other functions (e.g. digestion)

Parasympathetic Nervous System

Causes body to slow down AFTER a stress response (break pedal)

Reflexes

Reactions that occur the moment sensory impulses reach the spinal cord

Accidents

By observing the brain damage and behaviour after an accident, researchers can determine the functions the damaged part played in behaviour.

Lesions

• The removal or destruction of part of the brain

• Observe behaviour afterwards to determine function of that part of the brain

• Frontal Lobotomy (In the past, lesioning of frontal lobe was used to make the patients calm and relieve symptoms)

Electroencephalogram (EEG)

• Detects brain waves

• Examine what type of waves the brain produces during different stages of consciousness and use this information to generalize about brain function.

Computerized Axial Tomography Scan (CAT or CT)

• Several X-ray cameras that rotate around the brain and combine all the pictures into a detailed 3D picture

• Only show structure, not the functions or activity

Magnetic Resonance Imaging (MRI)

• Uses magnetic fields to measure the density and location of brain material.

• Only show structure, not functions or activity

Positron Emission Tomography (PET)

• Shows what areas of the brain are most active during certain tasks

• Measures how much of a certain chemical parts of the brain are using

Functional MRI (fMRI)

• Combines elements of MRI and PET scans

• Show details of brain structures with information about blood flow in the brain

Hindbrain

• Controls basic biological functions that keep us alive

• Contains medulla, pons, and cerebellum

Medulla

Part of hindbrain that controls blood pressure, heart rate, and breathing

Pons

Part of hindbrain that controls facial expressions

Cerebellum

Part of hindbrain that coordinates habitual muscle movements

Midbrain

Coordinates simple movements with sensory information

Reticular Formation

A netlike connection of cells throughout the midbrain that controls general body arousal and the ability to focus our attention

Forebrain

• Controls thought and reason (what makes us human)

• Contains thalamus, hypothalamus, amygdala, and hippocampus

Thalamus

Receives the sensory signals coming up the spinal cord and sends them to the appropriate areas in the rest of the forebrain

Hypothalamus

• Metabolic functions

• e.g. body temperature, sexual arousal (libido), hunger, thirst, and the endocrine system

Amygdala

Vital to experiences of emotion

Hippocampus

Processes memory to be permanently stored in other areas of the cerebral cortex

Cerebral Cortex

• Grey wrinkled surface of the brain (layer of densely packed neurons)

• Contains 8 lobes, 4 in each hemisphere (frontal, parietal, occipital, temporal)

• Overtime, the dendrites of the neurons grow and connect with other neurons to form the complex neural web

Fissures

Wrinkled surface of the cerebral cortex to increase surface area

Hemispheres

• The two halves of the brain (right and left)

• Theories: Left = logic and sequential tasks, Right = spatial and creative tasks

Contralateral Control

• LEFT hemisphere: sensory and motor functions of RIGHT half of body

• RIGHT hemisphere: sensory and motor functions of LEFT half of body

Brain Lateralization

• Specialization of function in each hemisphere

• Research is done by examining split-brain patients

Split-brain

• Corpus callosum is cut to treat severe epilepsy

• Operation pioneered by Roger Sperry and Michael Gazzaniga

• Cannot orally report info only in the right hemisphere since spoken language is in the left hemisphere

Association Area

Any area of the cerebral cortex that is not associated with receiving sensory information or controlling muscle movements

Frontal Lobes

Large areas of the cerebral cortex located at the top front part of the brain behind the eyes

Prefrontal Cortex

• Anterior / front of frontal lobe

• Critical role in thought directing process

Broca’s Area (Paul Broca)

• Frontal lobe

• Responsible for controlling muscles involved in producing speech

Wernicke’s Area (Carl Wernicke)

• Temporal lobe

• Responsible for understanding of spoken and written language

Motor Cortex

• Thin, vertical strip at the back of the frontal lobe

• Sends signals to our muscles, controlling our voluntary movements

• Top of the body is controlled by neurons at the bottom of this cortex, progressing down the body as you go up the cortex

Parietal Lobes

• Located behind the frontal lobe but still on the top of the brain

• Contains the sensory cortex

Sensory Cortex

• A thin, vertical strip that receives incoming touch sensations from the rest of our body

• Top of sensory cortex receives sensations from the body of the body and vice versa

Occipital Lobes

• At the very back of our brain, farthest from our eyes

• Interpret messages from our eyes in our visual cortex

  • Impulses from right half of each retina are processed in the visual cortex in the right occipital lobe

  • Impulses from left half of each retina are processed in the visual cortex in the left occipital lobe

Temporal Lobes

• Process sound sensed by our ears (auditory cortex)

• Sound received by either ear is processed in both auditory cortices

• Damage to this area affects ability to interpret spoken language (Wernicke’s area)

Brain Plasticity

The ability of the nervous system to change its activity in response to intrinsic or extrinsic stimuli by reorganizing its structure, functions, or connections.

Endocrine System

• A system of glands that secrete hormones that affect many different biological processes in our bodies

• Controlled by hypothalamus

Adrenal Glands

• Produce adrenaline

• Signals body to prepare for fight or flight (autonomic nervous system - involuntary responses)

Ovaries and Testes

• Produce sex hormones

• Levels of estrogen and testosterone may explain gender differences (Developmental Psychology)

Monozygotic Twins

Identical twins (same genetic material)

Thomas Bouchard

• Studied monozygotic twins raised in different families to see if traits were nature or nurture

• Criticized because twins share the same physical characteristics, thus causing others to treat them in similar ways (effective psychological environment).

Turner’s Syndrome

Single X chromosome instead of a 23rd pair

Klinefelter’s Syndrome

Extra X chromosome, thus XXY pattern

Down Syndrome

Extra chromosome on 21st pair