The Biology of Behavior Chapter 2 The Biology of Behavior

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 No animation.

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 wave Just 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.

How neurons communicate (with each other): When does the cell send the action potential? When it reaches a threshold. How neurons communicate (with each other): 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. The threshold is reached when excitatory (“Fire!”) signals outweigh the inhibitory (“Don’t fire!”) signals by a certain amount.

The Synapse The synapse is a junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. The synapse is also known as the “synaptic junction” or “synaptic gap.”

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 Together Neural Communication: Seeing all the Steps Together No animation.

Roles of Different Neurotransmitters Some Neurotransmitters and Their Functions Neurotransmitter Function Problems Caused by Imbalances Serotonin Affects mood, hunger, sleep, and arousal Undersupply linked to depression; some antidepressant drugs raise serotonin levels Dopamine Influences 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 Glutamate A 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.

Divisions of the Nervous System .

The Inner and Outer Parts of the Nervous System The Peripheral Nervous System (CNS), gathers information from the body and sends CNS decisions out to the body. The Central Nervous System (CNS), the brain and spinal cord, is the body’s decisionmaker.

Types of Neurons Sensory 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

Cerebellum (“little brain”) The cerebellum helps coordinate voluntary movement such as playing a sport. The cerebellum has many other functions, including enabling nonverbal learning and memory.

The Limbic (“Border”) System The limbic system coordinates: 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 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.

The Hypothalamus: The Hypothalamus as a Reward Center 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. Thalamus The Hypothalamus as a Reward Center Riddle: Why did the rat cross the grid? Why did the rat want to get to the other side? 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 Brain Topics 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: 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. 300 billion synaptic connections The brain has left and right hemispheres

The Lobes of the Cerebral Cortex: Preview involved in speaking and muscle movements and in making plans and judgments Frontal Lobes Parietal Lobes Occipital Lobes ______________ include the sensory cortex include the visual areas; they receive visual information from the opposite visual field include the auditory processing areas

Functions of the Brain: The Motor and Sensory Strips 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)  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 cortex More 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.

The intact but lateralized brain Right-Left Hemisphere Differences Right Hemisphere Feelings and intuition Language: tone, inflection, context Wholes, including the self Thoughts and logic Language: words and definitions Pieces and details