Neurotransmitters and Blood-Brain Barrier

Neurotransmitters and the Nervous System

• GABA (gamma-aminobutyric acid) is a neurotransmitter that plays an inhibitory role in the nervous system, regulating anxiety.
• One-third of all neurons use GABA for synaptic communication.
• Dopamine is a neurotransmitter that affects thoughts, emotions, motivation, and behavior.

The Blood-Brain Barrier

• The blood-brain barrier is a membrane that controls the passage of substances from the blood into the central nervous system.
• It prevents foreign substances in the blood from disrupting neural functioning in the brain.

Neurons

• Neurons are the basic units of the nervous system, carrying information from cell to cell within the nervous system as well as to and from muscles and organs.
• Neurons receive information from adjacent cells and pass it down the axon.
• The axon is a long extension from the cell body, responsible for transmitting information between neurons.
• Dendrites are branch-like extensions that receive messages from other neurons and pass it down the axon.

Communication between Neurons

• Communication between neurons occurs at synapses, where the axon terminal of one neuron releases neurotransmitters into the synaptic cleft.
• Neurotransmitters depolarize the postsynaptic membrane, making an action potential more likely.
• Inhibitory neurotransmitters hyperpolarize the postsynaptic neuron, reducing the likelihood of an action potential.

The Myelin Sheath

• The myelin sheath insulates the axon, increasing the speed of transmission of messages.
• The nodes of Ranvier are small spaces in the myelin sheath, where the axon is not insulated.

The Nervous System

• The grey matter of the brain gets its color from cell bodies, dendrites, and unmyelinated axons.
• The fundamental unit of the nervous system is the neuron.
• On average, an individual neuron communicates with about 1000 other neurons.

The Peripheral Nervous System

• The peripheral nervous system (PNS) carries information to and from the central nervous system.
• The PNS has two subdivisions: the somatic nervous system and the autonomic nervous system.
• Sensory neurons (afferent neurons) transmit information from sensory cells to the brain.
• Motor neurons (efferent neurons) transmit information from the brain to muscles and glands.

The Brain and Endocrine System

• The pituitary gland is often described as the "master gland" because it stimulates and regulates other glands.
• The endocrine system is a collection of glands that secrete hormones directly into the bloodstream.
• Gonads are endocrine glands that release hormones responsible for sex drive and the development of secondary sexual characteristics.

The CNS and its Functions

• The reticular activating system (RAS) is responsible for maintaining consciousness, regulating arousal levels, and modulating the activity of neurons throughout the CNS.
• The medulla oblongata is an area of the brain that controls heartbeat, circulation, and respiration.
• The cerebral cortex is responsible for symbolic thinking, making it possible for humans to engage in conversations about abstract concepts.

Brain Structure and Function

• The corpus callosum is a band of neural fibers that connect the left and right hemispheres of the brain.
• The septal area is involved in some forms of emotionally significant learning.
• The temporal lobe is involved in the foundation of human thought and language.

Behavior Genetics

• The field of behavior genetics studies the role of genetics in shaping mental processes and behavior.
• Research has shown that heritability estimates of IQ are approximately 0.50, and genetic influences on personality traits, such as neuroticism and aggressiveness, range from 0.15 to 0.5.### Nervous System
• The somatic nervous system is primarily involved in intentional (voluntary) behaviors.
• It transmits sensory information to the central nervous system and carries out motor commands.
• Sensory nerves receive information through receptors in the eyes, ears, tongue, skin, muscles, and other parts of the body.
• Motor neurons direct the action of skeletal muscles.

Thalamus

• The thalamus relays sensory information to the cerebral cortex.
• It acts as a switchboard for routing information from neurons connected to visual, auditory, taste, and touch receptors to the appropriate brain regions.
• It also filters these messages, emphasizing some and de-emphasizing others.

Chromosomes

• Genes are arranged along chromosomes.
• Chromosomes are strands of paired DNA that spiral around each other.
• Human cells have 46 chromosomes, except for sperm cells in males and egg cells in females, which have 23.

Heritability

• A heritability coefficient quantifies the extent to which variation in a trait across individuals can be accounted for by genetic variation.
• Heritability refers to genetic influences on the variability of traits among different individuals.
• A heritability coefficient of 0 indicates no heritability (i.e., no genetic influence), while a coefficient of 1 indicates that a trait is completely heritable (i.e., entirely the result of genetic influence).

Neurons

• Interneurons are responsible for connecting other neurons to each other.
• Dendrites receive information from other neurons and pass it down the axon.
• The cell body includes a nucleus that contains the chromosomes or genetic material of the cell.
• Axons are responsible for transmitting information to other neurons.
• Terminal buttons receive information from the axon and pass it on to adjacent cells via the release of neurotransmitters.
• Neurons send signals by releasing a chemical that alters the electrical charge of the next neuron.
• The resting potential of a neuron refers to the condition in which the neuron is not firing.

Multiple Sclerosis

• Multiple sclerosis is a disorder that involves problems with the myelin sheath.
• Degeneration of the myelin sheath occurs on large clusters of axons and can produce jerky, uncoordinated movement.