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Biology and Behavior:Studying the Last Frontier

Neuroscience

• Involves study of the brain and nervous system

Biological psychology

• Focuses on how the brain and other biological systems influence human behavior

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Can you identify the structure of a typical neuron?

Dendrites

Cell body

Axon

Myelin sheath

Terminal buds

Synapse

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Biology and Behavior

Glia to the Rescue

A scanning electron micrograph shows neurons (green) and glia (orange).

Glial cells serve as the “glue” of the nervous system, providing cohesion and support for the neurons.

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COMMUNICATION WITHIN NEURONS

1. THE NEURON AT

REST

2. THE ACTION POTENTIAL

3. ACTION POTENTIAL TRAVELS

LENGTH OF AXON

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Biology and Behavior:Studying the Last Frontier

COMMUNICATION WITHIN AND BETWEEN

Resting potential

• Electrical potential of cell at rest

• -70 mv

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Biology and Behavior:Studying the Last Frontier

COMMUNICATION WITHIN AND BETWEEN

Action potential

• Spike in electrical energy that passes through the axon of a neuron, purpose of which is to convey information

• “all-or-none”

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Biology and Behavior:

COMMUNICATION WITHIN AND BETWEEN

• Myelin sheath insulates and protects the tiny spikes in electricity happening inside the axon.

• Action potential “skips” over the segments of myelin, hopping from one node to the next, instead of traversing the entire length of the axon.

MYELINProtein that envelops and insulates the axon, facilitating faster transmission of the impulse.

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Biology and Behavior:

Neurotransmitters

• Chemical messengers that neurons use to communicate at the synapse

Receptor sites

• Location where neurotransmitters attach on the receiving side of the synaptic gap

Reuptake

• Process by which neurotransmitters are reabsorbed by the sending terminal bud

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Synaptic TransmissionSending neurons transmit their messages to receiving neurons by electrochemical action. When a neuron fires, the action potential

arrives at the axon terminal and triggers the release of neurotransmitters from the synaptic vesicles. Neurotransmitters flow into the synaptic cleft and move toward the receiving neuron, which has numerous receptors. The receptors will bind only with neurotransmitters

whose molecular shapes match their enclosed volumes. Neurotransmitters influence the receiving neuron to fire or not to fire.

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Biology and Behavior

Axon terminal of a sending neuron interacts with the dendrites of a receiving neuron by releasing chemical messengers (neurotransmitters) into the synapse.

Once the neurotransmitters migrate across the gap and latch onto the dendrite’s receptor sites, the message has been conveyed.

The Synapse

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NEUROTRANSMITTERS

Acetylcholine

• Relays messages from motor neurons to muscles, enabling movement; involved in memory

• Too much = spasms; too little = paralysis

Glutamate

• Makes neurons fire; central role in memory and learning

• Too much = strokes; too little = schizophrenia

GABA

• Inhibits neurotransmitter firing; contributes to motor control, vision

• Too little = anxiety

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NEUROTRANSMITTERS

Norepinephrine

• Has variety of effects in CNS; helps body prepare for stress

Epinephrine

• Adrenaline; physical booster; fight/flight response

Serotonin

• Plays key role in controlling appetite, aggression, and mood; regulates sleep and breathing

Dopamine

• Plays role in modulating mood; plays central role in positive reinforcement and dependency; involuntary behavior

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NEUROTRANSMITTERS

Endorphins

• Regulates secretion of other neurotransmitter; naturally produced opioids; reduces pain and elevates mood

Agonists

• Interfere at level of synapse; increase normal neurotransmitter activity’ mimics NT activity or blocks reuptake

Antagonists

• Interfere at level of synapse; decrease normal neurotransmitter activity

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The Human Nervous System The nervous system is divided into two parts: the peripheral nervous system and the central nervous system. The diagram shows the relationships among the parts of the

nervous system and provides a brief description of the functions of those parts.

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The Peripheral Nervous System

• Includes all neurons not in Central Nervous System (CNS)

• Supplies CNS with information about body’s environment

• Made up of 2 subdivisions:

• Somatic

• Autonomic

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SOMATIC NERVOUS SYSTEM

• Includes sensory nerves and motor nerves

• Gathers information from sensory receptors

• Controls the skeletal muscles responsible for voluntary movement

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The Supporting Systems

Sensory neurons

•Receive information about the environment from the sensory systems and convey this to the brain for processing

Motor neurons

•Carry information from CNS to produce movement; provide mechanism regulated by spinal cord and brain

Interneurons

•Resides in brain and spinal cord; act as bridges connecting sensory and motor neurons

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AUTONOMIC NERVOUS SYSTEM• Regulates involuntary activity

• Has two divisions involved in physiological responses to stress or crisis situations

• Sympathetic nervous system – fight or flight

• Parasympathetic nervous system – rest and digest

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THE SYMPATHETIC AND

PARASYMPATHETIC NERVOUS SYSTEM

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The Supporting SystemsThe Central Nervous System

Spinal cord

• Allows communication between the brain and the peripheral nervous system

• Connects with the body’s muscles, glands, and organs

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BRAINSTEM AND CEREBELLUM

Medulla

• Controls heartbeat, blood pressure, breathing, coughing, swallowing

Reticular formation

• Controls levels of arousal and quickly analyzes sensory information on its way to the cortex

Pons

• Involved in sleep and dreaming

Cerebellum

• Involves muscle coordination, posture and balance

• May also affect fine distinctions in cognition

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Digging Below the Cortex: Identify Functions

Hippocampus

Amygdala

Thalamus

Hypothalamus

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The Hemispheres

RIGHT BRAIN, LEFT BRAIN: THE TWO HEMISPHERES

Cerebrum

• Includes largest, most highly developed part of brain

• Involved in intelligence, personality, thinking, perceiving, planning and organization, language, sensation, motor functions

• Divided into right and left hemispheres and covered by corpus callosum

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The cerebrum looks like a walnut with its two wrinkled halves. Regions of the left and right hemispheres specialize in different activities, but the two sides of the brain are constantly communicating and collaborating.

The right hemisphere controls the left side of the body, and the left hemisphere controls the right.

This explains why Brandon, who was shot on the left side of his head, suffered paralysis and loss of sensation on the right half of his body.

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The Hemispheres

LATERALIZATION

• Left hemisphere plays a crucial role in language processing and right hemisphere plays a crucial role in managing visual spatial tasks.

But

• Hemispheres constantly integrate and share information.

• Corpus Callosum

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Assigning functions to one hemisphere or the other allows the brain to function more efficiently.

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THE LOBES: UP CLOSE AND PERSONAL

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The Hemispheres

LANGUAGE AREA AND THE BRAIN

Broca’s area

Wernicke’s area

Wernicke’s area

Broca’s area