Chapter 3

Biology and Behavior

• Sensation, perception, memory, and thinking are all psychological processes that have at least a partly biological basis.

• Three major areas of study for biological psychologists include the nervous system, the endocrine system, and heredity.

Nervous System

• The human nervous system is working when we are active or still, awake or asleep.

• Two main parts:

• Central nervous system consists of brain and spinal cord.

• Peripheral nervous system is made up of nerve cells that send messages between the central nervous system and all the parts of the body.

• The cerebrum – the front of the brain The largest part of the brain located in the front is called the cerebrum. The cerebrum is responsible for:

• Movement • Body temperature • Touch • Vision • Hearing • Judgment • Reasoning • Problem solving • Emotions • Learning

• The cerebrum has 2 parts: the right cerebral hemisphere and the left cerebral hemisphere. They are connected at the bottom and have a deep groove running between them. In general, the right cerebral hemisphere controls the left side of the body, and the left cerebral hemisphere controls the right. The right side is involved with creativity and artistic abilities. The left side is important for logic and rational thinking.

• The hemispheres of the cerebrum are divided into lobes, or broad regions of the brain. Each lobe is responsible for a variety of bodily functions:

• Frontal lobes are involved with personality, speech, and motor development

• Temporal lobes are responsible for memory, language and speech functions

• Parietal lobes are involved with sensation • Occipital lobes are the primary vision

centers

• The surface of the cerebrum appears wrinkled and is made up of deep grooves and bumps or folds. The outer part of the cerebrum is called gray matter and contains nerve cells. The inner part is called white matter and contains connections of nerves.

• The brainstem is located in front of the cerebellum. The brainstem is like the hard-drive of a computer. It is the main control panel for the body that passes messages back and forth between the brain and other parts of the body. The cerebrum, the cerebellum, and the spinal cord are all connected to the brainstem. The brainstem has three main parts, the midbrain, the pons, and the medulla oblongata.

• The brainstem controls vital functions of the body, including:

• Breathing • Consciousness • Cardiac function • Involuntary muscle movements • Swallowing • Movement of the eyes and mouth • Relaying sensory messages (pain, heat,

noise, etc.) • Hunger

• The cerebellum – the back of the brain Behind the cerebrum at the back of the head is the cerebellum. In Latin, cerebellum means “little brain.” However, the cerebellum contains more nerve cells than both hemispheres combined. The cerebellum is primarily a movement control center, responsible for:

• Voluntary muscle movements • Fine motor skills • Maintaining balance, posture, and equilibrium • Unlike the cerebrum, the left cerebellum controls

the left side of the body, and the right cerebellum controls the right side of the body.

• Nerve cells called neurons run through our entire bodies and communicate with each other.

• They send and receive messages from other structures in the body such as muscles and glands.

• Neurons resemble tree structures (branches, trunk, and roots).

• Unlike trees, neurons can also lie end to end. “Roots” can intertwine with “branches” of neurons that lie below.

• Each neuron has a cell body, dendrites, and an axon.

• A neuron has many dendrites but only one axon, which vary greatly in length.

• Many axons are covered in myelin which insulates and protects the axon and also helps to speed up the transmission of the message.

• At the end of the axon, small fibers, axon terminals branch out.

• Messages are sent from the axon terminals of one neuron to the dendrites of other neurons.

• It must cross the synapse. Messages travel in only one direction.

• New synapses can develop between neurons that were not previously connected.

• Information sent and place that it goes depends on a number of factors – locations and events.

• Sensory neurons are nerve cells that carry information received by the senses to the central nervous system.

• Motor neurons are nerve cells that carry information from the central nervous system to the muscles and the glands and influence their functioning.

• Neurons send messages across synapses through the release of neurotransmitters.

• A neuron fires its neurotransmitters like water droplets shooting out of a spray bottle.

• There are several types of neurotransmitters, each with its own specific structure and fits into a receptor site on the next neuron.

• The message is converted into an electrical impulse that travels the length of the neuron, then it is transmitted to the next neuron by neurotransmitters.

• The process continues until the next message arrives at its destination, and takes only a fraction of a second.

• There are dozens of types of neurotransmitters with different functions:

• acetylcholine – control of skeletal muscles

• dopamine – motor behavior• noradrenaline – prepares the body

for action• serotonin – emotional arousal and

sleep

• All messages are carried via the spinal cord and the peripheral nervous system.

• The central nervous system consists of the neurons of the spinal cord and the brain.

• The spinal cord is a column of nerves about as thick as the thumb and is protected by bones.

• The spinal cord transmits messages between the brain and the muscles & glands throughout the body.

• The peripheral nervous system lies outside the central nervous system and is responsible for transmitting messages between the central nervous system and all parts of the body.

• There are two main divisions:

• Somatic nervous system – transmits sensory messages to the central nervous system.

• Autonomic nervous system – regulates the body’s vital functions such as heartbeat, breathing, digestion, and blood pressure.

• The autonomic nervous system has two divisions with opposing functions:

• sympathetic nervous system – activated when a person is going into action, fight or flight response.

• parasympathetic nervous system – restores the body’s reserves of energy after an action has occurred.