The Nervous System & The Endocrine System: Year 8 Biology Final Exam Summary

1.2 The Central Nervous System

The Brain and Spinal Cord
> Each of the major areas of the brain– the cerebrum, cerebellum, and brain stem– are responsible for processing and relaying information.
> Sensory experiences changes the pattern of neuron connections in the brain.
> The stem cells in the brain produces new neurons throughout life.
> New cells– originate in regions associated with learning and memory.
> The spinal cord is the main communication link between the brain and the rest of the body.
> 31 pairs of spinal nerves branch out from the spinal cord, connecting the brain to the rest of the body.
> Information, including many reflexes are processed in the spinal cord.
> A reflex is a quick, automatic response to a stimulus.

Structure of the Brain
A. Hemispheres

The left hemisphere and right hemisphere are connected by a band of tissue called the corpus callosum. The left hemisphere controls the right part of the body, and vice versa.

B. Lobes

C. Other important stuff
> Cerebrum: largest region of human brain. Responsible for voluntary/ conscious activities. Site of learning, intelligence, and judgement.
Consists of two layers:
Outer layer– cerebral cortex
> Has densely packed nerve cell bodies (grey matter).
>This layer processes information from sense organs & controls body movement. Where thoughts, plans, and learning abilities are processed.
> Very wrinkly so it could have more surface area.
Inner layer– white matter
> The whitish color comes from bundles of axons with myelin sheaths.
> These axon may connect different areas of the cerebral cortex, or connect the cerebrum to other areas of the brain (i.e. brain stem).

> Limbic System: Structures make up the limbic system functions for emotion, behavior, memory.
Example: amygdala– associated with emotional learning (fear & anxiety) & also long term memories.
The limbic system is also associated with the brain's pleasure center, a region that produces feelings of satisfation and well-being.

> Thalamus and Hypothalamus: Found between the brain stem and the cerebrum.
Thalamus receives messages from sensory receptors & relays them to the proper region of the cerebrum.
Hypothalamus is the control center for recognition & analysis of hunger, thirst, fatigue, anger, and body temperature. Also helps coordinate the nervous & endocrine systems.

> Cerebellum: Second largest region. Info about muscle and joint position, as well as other inputs are sent here.
The commands to move muscles come from the cerebral cortex, but the cerebellum coordinates and balances the actions of these muscles so your body can move gracefully.

> Brain Stem: Connects the brain and the spinal cord. Three regions– the midbrain, the pons, and the medulla oblongata.
Regulates the flow of information between the brain and the rest of the body.
Regulation of blood pressure, heart rate, and breathing, and swallowing, etc. are all controlled by the brain stem. It keeps your body functioning when you're unconscious.

Addiction and the Brain
> Synapse makes the brain works by transferring message from cell to cell. (i.e. thinking, producing and feeling emotions.)
> If a chemical change the way the synapse worked, they would also alter behavior.
> Addictive substances (heroin, methamphetamine, cocaine, tobacco, alcohol) affect brain synapses.
> They all produce changes in one particular group of synapses. These synapses use the neurotransmitter dopamine and are associated with the brain's pleasure and reward centers.
> When things make us happy, neurons in the hypothalamus and the limbic system release dopamine.
> Dopamine molecules stimulates other neurons across these synapses, producing happiness.

The brain reacts to excessive dopamine levels by reducing the nunber of receptors for the neurotransmitter. As a result, normal activites no longer produce the sensations of pleasure they once did.
> This is why addicts feel depressed and sick without their drugs.
> Fewer amount of receptors– larger amounts of drugs needed to produce the same high. Then they become more addicted. The addiction is hard to break.

5 minute break time!

LOL! Moving on...