The Biology of Behavior

Chapter 2

Overview: What We Have in Mind

Building blocks of mind: ____________ and how they communicate (neurotransmitters)

Systems that build the mind: Functions of Parts of the ___________________

Supporting player: the slower-communicating ___________________(hormones)

Tools for examining the brain and its activities More primitive and advanced brain structures

Interesting Figures in Neuroscience

• Franz Gall-1758-1828

• Phrenology

• Santiago Ramon y Cajal

1852-1934

Neurons and Neuronal Communication:The Structure of a Neuron

There are billions of neurons (nerve cells) throughout the body.

________________________:a neural impulse that travels down an

axon like a waveJust as “the wave” can flow to the right in a stadium even though the people only move up and down, a wave moves down an axon although it is only made up of ion exchanges moving in and out.

The neuron

receives signals

from other neurons; some are telling it to

fire and some are telling it

not to fire.

• When the threshold is reached, the action potential starts moving.

• Like a gun, it either fires or it doesn’t; more stimulation does nothing.

• This is known as the “all-or-none” response.

The action

potential travels

down the axon

from the cell body

to the terminal

branches.

The signal is transmitted to another cell. However, the

message must find a way to cross a gap

between cells. This gap is

also called the synapse.

How neurons communicate(with each other):

When does the cell send the action potential? When it reaches a threshold.

The threshold is reached when excitatory (“Fire!”) signals outweigh the inhibitory (“Don’t fire!”) signals by a certain amount.

The synapse is also known as the “synaptic junction” or “synaptic gap.”

The SynapseThe synapse is a junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron.

Neurotransmitters

Neurotransmitters are chemicals used to send a signal across the synaptic gap.

Reuptake: Recycling Neurotransmitters [NTs]

Reuptake: After the neurotransmitters stimulate the receptors on the receiving neuron, the chemicals are taken back up into the sending neuron to be used again.

Seeing all the Steps TogetherNeural Communication:

Some Neurotransmitters and Their FunctionsNeurotransmitter Function Problems Caused by Imbalances

Roles of Different Neurotransmitters

Serotonin Affects mood, hunger, sleep, and arousal

Undersupply linked to depression; some antidepressant drugs raise serotonin levels

DopamineInfluences movement, learning, attention, and emotion

Oversupply linked to schizophrenia; undersupply linked to tremors and decreased mobility in Parkinson’s disease and ADHD

Acetylcholine (ACh)

Enables muscle action, learning, and memory

ACh-producing neurons deteriorate as Alzheimer’s disease progresses

Norepinephrine Helps control alertness and arousal

Undersupply can depress mood and cause ADHD-like attention problems

GABA gamma-aminobutyric acid

A major inhibitory neurotransmitter

Undersupply linked to seizures, tremors, and insomnia

GlutamateA major excitatory neurotransmitter; involved in memory

Oversupply can overstimulate the brain, producing migraines or seizures; this is why some people avoid MSG (monosodium glutamate) in food

__________ pathways

Networks of neurons that communicate with serotonin help regulate mood.

Networks of neurons that communicate with dopamine are involved in focusing attention and controlling movement.

____________ pathways

Divisions of the Nervous System

The Inner and Outer Parts of the Nervous System

The Central Nervous System (CNS), the brain and spinal cord, is the body’s decisionmaker.

The Peripheral Nervous System (CNS), gathers information from the body and sends CNS decisions out to the body.

Types of NeuronsSensory

neurons carry messages IN

from the body’s tissues and

sensory receptors to the

CNS for processing.

Motor neurons carry instructions

OUT from the CNS out to the body’s tissues. Interneurons (in the

brain and spinal cord) process information between the sensory

input and motor output.

The Peripheral Nervous System

The ___________

Nervous System:

The sympathetic NS arouses

(fight-or-flight)

The parasympathetic

NS calms(rest and digest)

The ________________ System

The endocrine system: a set of glands that produce chemical messengers called hormones.

The Body’s “Slow but Sure” Endocrine Message System The endocrine system sends

molecules as messages, just like the nervous system, but it sends them through the bloodstream instead of across synapses.

These molecules, called hormones, are produced in various glands around the body.

The messages go to the brain and other tissues.

Pituitary gland

The pituitary gland is the “master gland” of the endocrine system.

It is controlled through the nervous system by the nearby brain area--the hypothalamus.

The pituitary gland produces hormones that regulate other glands.

The Brainstem: Pons and Medulla

The Base of the Brainstem: The Medulla

The medulla controls the most basic functions such as ___________________________

Someone with total brain damage above the medulla could still breathe independently, but someone with damage in this area could not.

The Thalamus The thalamus is the

“sensory switchboard” or “router”: All sensory messages, except smell, are routed through the thalamus on the way to the cortex (outer brain).

These messages cross over from one side of the body to the opposite side of the brain.

The crossover

The cerebellum helps coordinate voluntary movement such as playing a sport.

Cerebellum (“little brain”)

The cerebellum has many other functions, including enabling nonverbal learning and memory.

emotions such as fear and aggression.

basic drives such as hunger and sex.

the formation of episodic memories.

The hippocampus (“seahorse”) processes conscious, episodic

memories. works with the amygdala to

form emotionally charged memories.

The Amygdala (“almond”) consists of two lima bean- sized

neural clusters. helps process emotions,

especially fear and aggression.

The Limbic (“Border”) SystemThe limbic system coordinates:

The Amygdala: Enabling two different responses to threat

Electrical stimulation of one area of a cat’s amygdala provokes _________________ reactions.

If you stimulate a different part of the amygdala and put the cat in a cage with a mouse, the cat will cower in terror.

lies below (“hypo”) the thalamus.

regulates body temperature and ensures adequate food and water intake (homeostasis), and is involved in sex drive.

directs the endocrine system via messages to the pituitary gland.

The Hypothalamus:Thalamus

Riddle: Why did the rat cross the grid? Why did the rat want to get to the other side?

The Hypothalamus as a Reward Center

Pushing the pedal that stimulated the electrode placed in the hypothalamus was much more rewarding than food pellets.

Review of Brain Structures

Higher Brain, Split BrainTopics for your cortex to process:

Cerebral Cortex Structure: The Lobes

The motor and sensory strips and association areas

Brain Plasticity Functioning of he

right and left hemispheres from cases of the divided and intact brains

The Cerebral Cortex:

300 billion synaptic connections

The brain has left and right hemispheres

The outer grey “bark” structure that is wrinkled in order to create more surface area for 20+ billion neurons.

Organized into 4 lobes in each of two hemispheres.

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The Lobes of the Cerebral Cortex: Preview

Frontal Lobes

Parietal Lobes

Occipital Lobes

______________

involved in speaking and muscle movements and in making plans and judgments

include the sensory cortex

include the visual areas; they receive visual information from the opposite visual field

include the auditory processing areas

Input: Sensory cortex (Left hemisphere section receives input from the body’s right side)

Output: Motor cortex (Left hemisphere section controls the body’s right side)

Functions of the Brain: The Motor and Sensory Strips

Axons receiving motor signals FROM the cortex

Axons sending sensory

information TO the cortex

Sensory Functions of the Cortex

The sensory strip deals with information from touch stimuli.

The occipital lobe deals with visual information.

Auditory information is sent to the temporal lobe.

___________ function of the cortexMore complex animals have more cortical space devoted to integrating/associating information

Our Two Hemispheres

_________________________ (“going to one side”)The two hemispheres serve some different functions. How do we know about these differences? Brain damage studies revealed many functions of

the left hemisphere. Brain scans and split brain studies show more about

the functions of the two hemispheres, and how they coordinate with each other.

• Thoughts and logic

• Language: words and definitions

• Pieces and details

• Feelings and intuition

• Language: tone, inflection, context

• Wholes, including the self

The intact but lateralized brainRight-Left Hemisphere Differences

Left Hemisphere Right Hemisphere