©1999 prentice hall neurons, hormones, and the brain chapter 4

©1999 Prentice Hall

Neurons, Hormones, and the Brain

Chapter 4


Neurons, Hormones and the Brain

The central nervous system. The peripheral nervous system. Communication in the nervous system. Neurotransmitters. Mapping the brain. A walk through the brain. Are there “his” and “hers” brains?


The Central Nervous System

Brain. Spinal cord.

A collection of neurons and supportive tissue running from the base of the brain down the center of the back

Protected by spinal column.


The Withdrawal Reflex


Peripheral Nervous System Somatic

Includes the nerves that are connected to sensory receptors and skeletal muscles.

Autonomic The sympathetic nervous system mobilizes bodily

resources and increases the output of energy during emotion and stress.

The parasympathetic nervous system operates during relaxed states and that conserves energy.


Organization of the Nervous System


Communication in the Nervous System The structure of the neuron.

Different kinds of neurons. How neurons communicate.

Action potential. Chemical messengers in the nervous system.

Neurotransmitters. Major neurotransmitters. Opioids and substance P.

Endocrine system. Hormones.


Structure of a Neuron Dendrites

receive information from other neurons and transmit towards the cell body

Cell body keeps the neuron alive and

determines whether it will fire.

Axon extending fiber that conducts

impulses away from the cell body and transmits to other cells.


Structure of a Neuron Myelin Sheath Fatty insulation that may surround the axon of a neuron.


Different Kinds of Neurons


How Neurons Communicate Axon terminals release

neurotransmitter. Neurotransmitter

enters synaptic gap. Neurotransmitter binds

to receptors that it fits.


Action Potential A brief change in electrical voltage which occurs

between the inside and outside of an axon when a neuron is stimulated. It produces an electrical impulse.


Neurotransmitter A chemical substance that is released by a

transmitting neuron at the synapse and that alters the activity of a receiving neuron.


Major Neurotransmitters Serotonin Dopamine Acetylcholine (ACh) Norepinephrine Gamma amino butryic acid (GABA) Glutamate Endorphins


Opioids and Substance P


The Endocrine System Endocrine glands

release hormones into the bloodstream.

Hormones regulate growth, metabolism, sexual development and behavior, and other functions.


Hormones: Long Distance Messengers Melatonin. Adrenal Hormones.

Cortisol, epinephrine, and norepinephrine. Sex Hormones.

Androgens, estrogens, and progesterone.


Mapping the Brain Lesion method. Electroencephalogram (EEG). Transcranial magnetic stimulation (TMS). Positron-Emission tomography (PET). Magnetic resonance imaging (MRI).


Mapping the Brain

Lesioning Involves damaging and removing sections of

brain in animals, then observing their effects. Transcranial magnetic stimulated (TMS)

Stimulates brain cells using a powerful magnetic field produced by a wire coil placed on the head.

Can be used to temporarily inactivate neural circuits.


Electroencephalogram (EEG) A recording of neural activity detected by

electrodes.


Positron Emission Tomography (PET) A method for analyzing biochemical activity in the

brain, using injections of a glucose-like substance containing a radioactive element.

Active areas have increased blood flow.

Sensors detect radioactivity.

Different tasks show distinct activity patterns.


Magnetic Resonance Imaging (MRI) Method for studying body

and brain tissue. Magnetic fields align

certain ions and compounds

When field is removed, these molecules release energy as radio waves

Computer calculates tissue density from radio waves.

Provides clear, 3D images.


A Walk Through the Brain 3 Major Regions The brain stem. The cerebellum. The thalamus. The hypothalamus and the pituitary gland. The amygdala. The hippocampus. The cerebrum and lobes of the cerebral cortex..

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3 Major Regions of the Brain Hindbrain

Located in the skull’s rear, is the lowest portion of the brain. = 3 parts medulla, pons, cerebellum

Midbrain Located between the hindbrain and forebrain responsible

for connecting the two - (reticular activating system) (substantia nigra)

Forebrain the brain’s largest and most complex region

encompassing thalamus, hypothalamus, limbic system, cerebrum


The Brain Stem - Hind/Midbrain Pons

involved in sleeping, waking and dreaming.

Medulla responsible for certain

automatic functions such as breathing and heart rate.

Reticular activating system (or formation) arouses cortex and screens

incoming information.


The Cerebellum Regulates movement

and balance. Involved in

remembering simple skills and acquired reflexes.

Plays a part in analyzing sensory information, solving problems and understanding words


The Thalamus Relays sensory messages to the cerebral cortex.

“Traffic Officer” - “Server” Includes all sensory messages except those from

olfactory bulb.


Hypothalamus and Pituitary Gland Involved in emotions and

drives vital to survival including fear, hunger, thirst, and reproduction.

Also regulates autonomic nervous system.

The pituitary gland is a small endocrine gland which releases hormones and regulates other endocrine glands.

Pituitary Gland


The Amygdala Responsible for arousal

and regulation of emotion and the initial emotional response to sensory information.

Plays important role in mediating anxiety and depression.


The Hippocampus Responsible for the

storage of new information in memory.

Compares information with what the brain has come to expect about the world.

“Gateway to memory” because it enables us to navigate through the environment.


The Cerebrum Largest brain structure.

19/13/3 lbs. 1/1,000 - 1/10,000 - 1/60 Consists of upper part of brain and divided into two

cerebral hemispheres which are connected by the corpus callosum.

In charge of most sensory, motor and cognitive processes.

Surrounded by cerebral cortex, a collection of several thin layers of cells (gray matter). only 3 millimeters thick - 70% neurons in the

central nervous system Corticalization - increase in size and wrinkling


Lobes of the Cerebral Cortex Occipital lobes.

Visual cortex.

Parietal lobes. Somatosensory cortex.

Temporal lobes. Memory, perception, emotion and auditory cortex. Left lobe, Wernicke’s area.

Frontal lobes. Emotion, planning, creative thinking and motor cortex. Left lobe, Broca’s area.


Lobes of the Cerebral Cortex


Phineas Gage Gage was a railroad

construction foreman An 1848 explosion forced

a steel tamping rod through his head

Others said he was “…no longer Gage…”

Lost his job, worked as a sideshow exhibit


The Corpus Callosum Millions of myelinated

axons connecting the brain’s hemispheres.

Provides a pathway for communication between the hemispheres.

If surgically severed for treatment of epilepsy, hemispheres cannot communicate directly.


Split-Brain Experiment


Split-Brain Experiment Subjects were presented information to one or the

other side of their brains. Patients identified verbally the pictures to the right

(i.e., boy). When asked to point to the face seen, the patients

pointed to the left picture.


Are There “His” and “Hers” Brains? After analyzing 49 studies of sex differences in

brain anatomy, researchers found small differences between the two groups and larger differences within groups.

There does appear to be sex differences in lateralization of language. Males show left hemisphere activation only. Females, left and right.

There also appears to be differences in amounts of gray matter. Females have more.


3 Ways to Interpret These Findings

These supposed differences are stereotypes. A biological differences does not necessarily

have implications for behavior and performance.

Sex differences in the brain could be the result rather than the cause of behavioral differences.

©1999 prentice hall neurons, hormones, and the brain chapter 4

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