Chapter 2

Chapter 1: What is Psychology?

Chapter 2Biology and Psychology

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The Nervous System: On Being Wired

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LO1 Describe the nervous system, including neurons, neural impulses, and neurotransmitters

Neurons

Neurons

Receive and pass messages

Cell body, dendrites (cellulipetal), axon (cellifugal)

Glial cells

Nourish and insulate neurons

Direct growth of neurons

Remove waste products

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Truth or Fiction? The human brain is larger than that of any other animal. FALSE A human brain weighs about 3 pounds, but the brains of elephants and whales may be four times as heavy. However, our brains account for a greater part of our body weight than do those of elephants or whales.

glial cells cells that nourish and insulate neurons, direct their growth, and remove waste products from the nervous system

dendrites rootlike structures, attached to the cell body of a neuron, that receive impulses from other neurons

axon a long, thin part of a neuron that transmits impulses to other neurons from branching structures called terminal buttons

myelin a fatty substance that encases and insulates axons, facilitating transmission of neural impulses

Neurons

Afferent Neurons

Transmit messages from sensory receptors to the spinal cord and brain

Efferent Neurons

- Transmit messages from brain or spinal cord to muscles and glands

Interneurons

- form all neural wirings within the CNS

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Truth or Fiction? A single cell can stretch all the way from your spine to your toe. TRUE A single cell can stretch all the way from your spine to your toe.

afferent neurons - neurons that transmit messages from sensory receptors to the spinal cord and brain. Also called sensory neurons

efferent neurons neurons that transmit messages from the brain or spinal cord to muscles and glands. Also called motor neurons

Neurotransmitters

Excitatory neurons

Cause other neurons to fire

Inhibitory neurons

Prevent other neurons from firing

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The Anatomy of a Neuron

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Figure 2.1. The Anatomy of a Neuron. Messages enter neurons through dendrites, are transmitted along the trunk-like axon, and then are sent from axon terminal buttons to muscles, glands, and other neurons. Axon terminal buttons contain sacs of chemicals called neurotransmitters. Neurotransmitters are released into the synaptic cleft, where many of them bind to receptor sites on the dendrites of the receiving neuron.

Go to 4ltrpress.cengage.com/psych to access an interactive version of this figure.

Firing: Neuron to Neuron

Synapse

Fluid-filled gap (Synaptic cleft) between

Axon terminal from transmitting neuron, and

Dendrite of receiving neuron

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synapse a junction between the axon terminals of one neuron and the dendrites or cell body of another neuron

Neurotransmitters

Neurotransmitters

Chemical substances that communicate from one neuron to another

Synaptic vesicles/clefts

Contain neurotransmitters in the axon terminals

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neurotransmitters chemical substances involved in the transmission of neural impulses from one neuron to another

Neural Impulse

Electrochemical messages that travel within neurons

Resting potential

Neuron is not responding to other neurons

degradation

Action potential

Conduction of neural impulse along axon

depolarization

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Truth or Fiction? Messages travel in the brain by means of electricity. TRUE The messages are within neurons. Communication between neurons, however, is carried out quite differently.

neural impulse the electrochemical discharge of a nerve cell, or neuron

polarize to ready a neuron for firing by creating an internal negative charge in relation to the body fluid outside the cell membranes

resting potential the electrical potential across the neural membrane when it is not responding to other neurons

depolarize to reduce the resting potential of a cell membrane from about 70 millivolts toward zero

action potential the electrical impulse that provides the basis for the conduction of a neural impulse along an axon of a neuron


Firing

Conduction of neural impulse along the length of a neuron

Threshold

Incoming messages reach a strength at which neuron will fire

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All-or-none principle

Every time a neuron fires, it transmits an impulse of the same strength.

Refractory period

Period of recovery time between firings

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Truth or Fiction? A brain cell can send out hundreds of messages each second and manage to catch some rest in between. TRUE During the refractory period, the neuron is insensitive to messages from other neurons and will not fire

all-or-none principle the fact that a neuron fires an impulse of the same strength whenever its action potential is triggered

refractory period a phase following firing during which a neuron is less sensitive to messages from other neurons and will not fire

Neurotransmitters

Receptor site

On dendrite of receiving neuron

Reuptake

Neurotransmitters reabsorbed

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receptor site a location on a dendrite of a receiving neuron tailored to receive a neurotransmitter

Neurotransmitters of Interest to Psychologists

Acetylcholine (ACh)

Controls muscle contractions, learning, remembering, controlling stag of sleep

Paralysis

Epinephrine

Adrenal medulla; central core of the adrenal glands

Dopamine

Pleasure, voluntary movement, learning, memory

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acetylcholine (Ach) a neurotransmitter that controls muscle contractions

hippocampus a part of the limbic system of the brain that is involved in memory formation


Norepinephrine

Excitatory neurotransmitter

Accelerates heart rate, affects eating, linked to activity levels, learning and remembering

Serotonin

Emotional arousal, pain, eating and sleep

Eating disorders, alcoholism, depression, aggression, insomnia

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serotonin a neurotransmitter, deficiencies of which have been linked to affective disorders, anxiety, and insomnia


Glutamic Acid (glutamate)

Direct effects in axos

seizure

Gamma-aminobutyric acid (GABA)

Inhibitory may help relax anxiety reactions

Depression

Endorphins

Occur naturally within the brain and bloodstream

Inhibit pain


Glycine

Inhibitory

Located at the spinal cord and lower portion of the brain

The Divisions of the Nervous System

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Figure 2.4 The Divisions of the Nervous System. The nervous system contains two main divisions: the central nervous system and the peripheral nervous system. The central nervous system consists of the brain and spinal cord. The peripheral nervous system contains the somatic and autonomic systems. In turn, the autonomic system has sympathetic and parasympathetic divisions. Go to 4ltpress.cengage.com/pysch to access an interactive version of this figure.

Parts of the Nervous System

Central Nervous System

Brain and spinal cord

Peripheral Nervous System

Sensory (afferent) and motor (efferent) neurons

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nerves a bundle of axons from many neurons

central nervous system the brain and spinal cord

peripheral nervous system the part of the nervous system consisting of the somatic nervous system and the autonomic nervous system

Peripheral Nervous System

Somatic Nervous System

Sensory and motor neurons

Transmits messages to the brain and purposeful body movements from the brain

Autonomic Nervous System

Regulates glands and muscles of internal organs

Contains sympathetic and parasympathetic divisions

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somatic nervous system the division of the peripheral nervous system that connects the central nervous system with sensory receptors, skeletal muscles, and the surface of the body

autonomic nervous system (ANS) the division of the peripheral nervous system that regulates glands and activities such as heartbeat, respiration, digestion, and dilation of the pupils

Branches of Autonomic Nervous System

Sympathetic

Most active during emotional responses

Spend the bodys reserves of energy

Parasympathetic

Most active during processes that restore bodys reserve of energy

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Truth or Fiction? Fear can give you indigestion. TRUE The sympathetic division of the ANS predominates when we feel fear or anxiety, and these feelings can therefore cause indigestion.

sympathetic the branch of the ANS that is most active during emotional responses, such as fear and anxiety, that spend the bodys reserves of energy

parasympathetic the branch of the ANS that is most active during processes (such as digestion) that restore the bodys reserves of energy

The Parasympathetic and Sympathetic Branches of the Autonomic Nervous System

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Figure 2.5 The Parasympathetic and Sympathetic Branches of the Autonomic Nervous System (ANS). The parasympathetic branch of the ANS generally acts to replenish stores of energy in the body. The sympathetic branch is most active during activities that expend energy. The two branches of the ANS frequently have antagonistic effects on the organs they service.

Central Nervous System

Spinal Cord

Transmits messages from sensory receptors to the brain and from the brain to muscle and glands

Spinal Reflex

Simple, unlearned response to stimulus

Gray matter - nonmyelinated

White matter - myelinated

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spinal cord a column of nerves within the spine that transmits messages from sensory receptors to the brain to muscles and glands throughout the body

spinal reflex a simple, unlearned response to a stimulus that may involve only two neurons

gray matter the grayish neurons and neural segments that are involved in spinal reflexes

white matter axon bundles that carry messages from and to the brain

The Reflex Arc

The Reflex Arc. Reflexes are inborn, stereotyped behavior patterns that have apparently evolved because they help individuals adapt to the environment even before they can understand and purposefully manipulate the environment. Here we see a cross section of the spinal cord, highlighting a sensory neuron and a motor neuron, which are involved in the knee-jerk reflex. In some reflexes, interneurons link sensory and motor neurons.

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Figure 2.6 The Reflex Arc. Reflexes are inborn, stereotyped behavior patterns that have apparently evolved because they help individuals adapt to the environment even before they can understand and purposefully manipulate the environment. Here we see a cross section of the spinal cord, highlighting a sensory neuron and a motor neuron, which are involved in the knee-jerk reflex. In some reflexes, interneurons link sensory and motor neurons.

The Brain: Wider Than the Sky

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LO2 List the structures of the brain and their functions.

The Parts of the Human Brain

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Figure 2.9 The Parts of the Human Brain. This view of the brain, split top to bottom, shows some of the most important structures.

Three layers of the BRAIN

Central core

Limbic System

Cerebral Hemisphere (cerebrum)

Central Core

Functions

Basic life processes, breathing, pulse, arousal, movement, balance, sleep, early stage of processing sensory information.

Structures and Functions of the Brain

Hindbrain

Medulla

Breathing, swallowing, digestion, heart rate posture

Pons

sleep

Cerebellum

Little brain

muscle coordination and balance

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medulla an oblong area of the hindbrain involved in regulation of heartbeat and respiration

pons a structure of the hindbrain involved in respiration, attention, and sleep and dreaming

cerebellum a part of the hindbrain involved in muscle coordination and balance


Middle of Central Core

Thalamus

Relay station for sensory stimulation

Transmit message from sense organs to cerebral cortex & from cerebral cortex to cerebellum and medulla

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thalamus an area near the center of the brain involved in the relay of sensory information to the cortex and in the functions of sleep and attention

hypothalamus a bundle of nuclei below the thalamus involved in body temperature, motivation, and emotion


Middle of Central Core

Hypothalamus

Regulates body temperature, motivation and emotion, autonomic function control, endocrine function control, homeostasis, motor function control

Hunger, thirst, sexual behavior, caring for offspring, aggression, sleep-wake cycle


Reticular Activation System

From hindbrain, ascends through midbrain into lower part of forebrain

Vital to attention, sleep, arousal

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reticular activation system a part of the brain involved in attention, sleep, and arousal


Forebrain

Limbic System

Amygdala, hippocampus and parts of hypothalamus

Involved in memory and emotion

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limbic system a group of structures involved in memory, motivation, and emotion that forms a fringe along the inner edge of the cerebrum

amygdala a part of the limbic system that apparently facilitates stereotypical aggressive responses


Cerebrum

Responsible for thinking and language

Cerebral Cortex

the wrinkled surface area (gray matter) of the cerebrum

Corpus Callosum

Connects two hemispheres

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cerebrum the large mass of the forebrain, which consists of two hemispheres

cerebral cortex - the wrinkled surface area (gray matter) of the cerebrum

corpus callosum a thick fiber bundle that connects the hemispheres of the cortex

The Cerebral Cortex

Outer layer of cerebrum

Two Hemispheres

Four Lobes

Frontal, Parietal, Temporal and Occipital

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The Lobes of the Cerebral Cortex

Occipital Lobe

Vision

Temporal Lobe

Hearing and Auditory functions

Parietal Lobe

Somatosensory Cortex, speech centers

Frontal Lobe

Motor Cortex, memory processing, emotion

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Truth or Fiction? If a surgeon were to stimulate a certain part of your brain electrically, you might swear that someone had stroked your leg. TRUE The action would be sensed in the somatosensory cortex.

somatosensory cortex the section of cortex in which sensory stimulation is projected. It lies just behind the central fissure in the parietal lobe.

motor cortex the section of cortex that lies in the frontal lobe, just across the central fissure from the sensory cortex; neural impulses in the motor cortex are linked to muscular responses throughout the body.

Thinking, Language, and the Cortex

Association areas

Not primarily involved in sensation or motor activity

Responsible for learning, thought, memory and language

Association areas in frontal lobe

Responsible for executive functions

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Executive functions such as problem solving, making plans, and decision making.

Association Areas

Posterior association areas

senses

Association areas of the parietal lobe

Locating objects in sensory space and maintaining maps of the environment

Left Brain, Right Brain

Hemispheres do not act independently

Functions overlap and they respond simultaneously

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The Endocrine System

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Endocrine System

Comprised of ductless glands that release hormones into the bloodstream

Hormones

Regulate growth, metabolism and some behaviors

Maintain steady bodily states

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LO3 Explain the role of the endocrine system and list the endocrine glands.

gland an organ that secretes one or more chemical substances such as hormones, saliva, or milk

endocrine system the bodys system of ductless glands that secrete hormones and release them directly into the bloodstream

hormone a substance secreted by an endocrine gland that regulates various body functions

The Endocrine Glands

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Figure 2.14. The Endocrine Glands.

Pituitary and the Hypothalamus

Pituitary gland

Lies below hypothalamus

Labeled as master gland

Hormones secreted by pituitary gland

Hypothalamus regulates pituitary gland activity

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pituitary gland the gland that secretes growth hormone, prolactin, antidiuretic hormone, and other hormones

Growth hormone regulates growth of muscles, bones, and glands

Prolactin regulates maternal behavior in lower mammals and stimulates production of milk in women

Vasopressin inhibits production of urine when body fluids are low

Oxytocin stimulates labor in pregnant women, connected with maternal behavior

Pineal Gland

Pineal gland

Secretes melatonin

Helps regulate sleep-wake cycle

May affect onset of puberty

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Adrenal Glands

Adrenal glands

Located above the kidneys

Cortical steroids

increase resistance to stress, anxiety, pain and emotional events

promote muscle development

Epinephrine and norepinephrine

Helps arouse body in threatening situations

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Adrenal cortex secretes cortical steroids increase resistance to stress; promote muscle development; cause liver to release stored sugar; makes more energy available in emergency

Adrenal medulla secretes epinephrine and norepinephrine Helps arouse body in threatening situations

Testes and Ovaries

Testosterone

produced by testes (smaller amounts from adrenal gland)

male sex characteristics

Estrogen and progesterone

produced by ovaries (smaller amounts from testes)

female sex characteristics

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Evolution and Heredity

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LO4 Describe evolutionary psychology and the connections between heredity, behavior, and mental processes.

Chromosomes

Receive 23 chromosomes from fathers sperm and 23 chromosomes from mothers egg cell

23rd pair of chromosomes are sex chromosomes

XX female

XY male

Down syndrome

Chromosomal abnormality

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sex chromosomes the 23rd pair of chromosomes, whose genetic material determines the sex of the individual

Down syndrome a condition caused by an extra chromosome on the 21st pair and characterized by mental deficiency, a broad face, and slanting eyes

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