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AP PsychologyUnit 2

Biological Basis of Behavior

It all starts with the brain. The Human brain is an extremely complex network nerve cells, neurons, lobes, ridges and electric pulses.

To understand behavior, we must first look at the brain, and how it operates.

The Brain

Neurons are individual nerve cells that carry and process information. The brain is literally made up of BILLIONS of neurons.

Neurons link together to form chains and carry information throughout the brain.

Think of neurons as messengers that carry vital information to and from different parts of the brain.

Neurons

A neuron is made up of four different parts Dendrites: neuron fibers that receive incoming

messages. They look like tree roots Soma: The soma is the main cell body of the

neuron, also receives information Axon: Fiber that carries information away from

the cell body Axon Terminals: Branching fibers at the end of

the axon. They link up with Dendrites of other neurons

Myelin Sheath: A fatty covering of the axon that speeds up nerve impulses.

Parts of a Neuron

Electronically charged molecules inside the neurons are called Ions.

Neurons have an electrical charge of minus 70 millivolts. The electrical charge of an INACTIVE neuron is called its Resting Potential.

When a message arrives from another neuron and raises its charge to minus 50 millivolts the neuron reaches its threshold and fires off. This is called the action potential of a neuron. The message is carried on at a speed of 200 miles per hour!!

Ions and Nerve Impulses

Synapse: a microscopic area between neurons.

Neurons technically do not touch each other as they are separated by a very small synapse. When messages cross a synapse, they are met with a chemical which is released by the neurons called Neurotransmitters. These neurotransmitters alter the activity of a neuron’s message in various ways(inhibiting/exciting messages).

Synapses and Neurotransmitters

The brain must relay all of the messages that are being spread to corresponding parts of the body. This takes place through the nervous system. Central Nervous system: consisting of the brain at the spinal cord. The CNS is of utmost importance to the human body. The CNS spreads messages to the Peripheral Nervous System

Peripheral nervous system: All of the parts of the nervous system outside of the brain and spinal cord.

Nervous networks

The Peripheral Nervous System is further broken down into two major parts. The somatic system carries messages to the sense organs and skeletal muscles. The autonomic system communicates with the internal organs and glands of the body.

The Autonomic system is further subdivided into the sympathetic(arousal) and parasympathetic(lowers levels of arousal) branches.

Peripheral Nervous system

The Brain

Researches aim to study the different areas and functions of the brain in an array of different ways.

Scientists can determine the different brain functions through Ablations(surgical removal of part of the brain), CT, PET, and MRI scans, and by using electrode wires to stimulate the brain and induce responses to stimulus.

The Brain

The Cerebrum makes up the two large hemispheres that cover the upper part of the brain. The brain is broken up into two cerebral hemispheres(right and left halves of the cerebrum)

The two sides of the brain are able to communicate by a bundle of fibers connecting the two sides called the Corpus Callosum.

The cerebral cortex is the outer layer of the cerebrum and contains roughly 70% of all neuron activity in the CNS.

Parts of the Brain

The two sides of the brain(left and right) have different functions, and control different parts of the body. The right side of the brain mainly controls the actions of the left side of the body, and the left side of the brain controls the other.

Strokes on the right side of the brain can cause damage to the left side of the body. Can create a curious problem called Spatial neglect.

Cerebral Hemispheres

Spatial neglect occurs when people who have suffered a stoke pay no attention to specific sides of the body. Patients often do not eat food on the left side of their plate(if the injury was o the right side of the brain), and may not even believe their own left arm is theirs.

Spatial Neglect

Split brains occur in people who have had their Corpus callosum severed.

People will literally have two different brains telling them what to do.

Your brain could tell you to walk into two different directions, turn on and off light switches and talk or be silent all at the same time.

“Split Brains”

Each side of our brain takes on specific roles to perform simple as well as complex tasks and everything in between. The left side of the brain is generally used for language(speaking, writing and understanding. Further, the left side is controls the ability to do math, tell time and keep rhythm.

The right side of the brain is better at picking up on patterns, recognizing faces, drawing or figuring out puzzles. The right side of the brain also understand irony, sarcasm and context.

The left side understands pinpoint details whereas the right side sees the bigger picture.

Right Brain/Left Brain

The human brain is broken up into multiple lobes, each with their own individual function.

Occipital Lobes: found in the back of the brain and main function is sight

Parietal Lobes: Next to the occipital lobes. Control touch, temperature and pressure.

Temporal Lobes: main function is controlling hearing. On the sides of the brain

Frontal Lobes: higher mental abilities and movement

Lobes of the Brain

The subcortex area of the brain is found immediately below the cerebral hemispheres.

It is divided into the forebrain, midbrain and hindbrain

Each part of the subcortex play vital roles in human cognition

Subcortex

The hindbrain contains important parts of the brain such as the Medulla and the Cerebellum.

The Medulla connects the brain with the spinal cord and regulates vital bodily function such as heart rate, breathing and swallowing.

The Cerebellum regulates posture, muscle tone and muscular coordination.

Hindbrain

Found in the Forebrain are the extremely important parts of the brain, the Thalamus and the Hypothalamus.

The Thalamus is the area of the brain that relays messages to the cerebral cortex.

The Hypothalamus regulates emotional behaviors and motives such as rage, temperature control, eating, drinking and waking up.

Forebrain

Found in the Limbic system are the Amygdala and the Hippocampus.

The Amygdala regulates emotions such as fear

The Hippocampus has the main function of storing memories.

Limbic System

The Endocrine system is a network of glands that’s secrete hormones into our bodies.

A hormone affects our moods, behavior, growth and more.

These hormones come from a variety of different glands in our body.

The Pituitary gland is deemed the master gland. It regulates growth, or the lack thereof. Too much or too little of a specific hormone coming from the Pituitary gland can cause Gigantism or people being very small.

Endocrine System

Other glands of note:Thyroid glandPineal glandAdrenal gland

All of these other glands have very specific jobs including the regulation of sleep, metabolism, stress, fear and anger.

Other glands