BIOLOGICAL BASES OF BEHAVIOR

GENERALPSYCHOLOGY

CHAPTER II:

BASIC BUILDING BLOCKS OF THE NERVOUS SYSTEM

The Nervous System is the body’s electrochemical communication circuitry.

The field that studies the nervous system is called neuroscience, and the people who study it are called neuroscientist.

BASIC BUILDING BLOCKS OF THE NERVOUS SYSTEM

The Nervous System is primarily composed of the Central Nervous System and the Peripheral Nervous System.

CHARACTERISTICS OF THE NERVOUS SYSTEM

1. Complexity2. Integration3. Adaptability4. Electrochemical Transmission

1. COMPLEXITY

The brain and nervous system being complex allows the individual to do activities of different kinds.

This is due to the orchestration of the billions of cells in the brain and the nervous system.

2. INTEGRATION

Integration refers to the ability of the brain to pull information together.

3. ADAPTABILITYAlthough the composition of the brain and the nervous system have hereditary foundation, both have the ability to constantly adapt to the changes in the body and the environment.

The term plasticity denotes thebrain’s special capacity for modification and change.

4. ELECTROCHEMICAL TRANSMISSION

The brain being the information processing system, powered by electrical impulses and chemical messages allows the individual to perceive and respond to stimuli.

PATHWAYS IN THE NERVOUS SYSTEM

1. Afferent Nerves (Sensory Nerves)-transport information to the brain.

Stimulus Sensory Receptors Afferent Nerves Brain

2. Efferent Nerves (motor nerves)-carry the brain’s output or response.

Brain Efferent Nerves Muscles (motor behaviour response)

3. Neural Networks-cluster of neurons that are interconnected to process information by integrating sensory input and motor output.

Peripheral Nervous System the network of nerves that connect the brain and the spinal cord to other parts of the body. It is divided into the somatic nervous system and the autonomic nervous system.

Somatic Nervous System the division of the PNS consisting of sensory nerves, whose function is to convey information to the CNS, and motor nerves, whose function is to transmit information to the muscles.

Autonomic Nervous System the division of the PNS that communicates with the body’s internal organs. It consist of the sympathetic and the parasympathetic nervous systems.

Sympathetic Nervous System the division of the autonomic nervous system that arouses the body.

Parasympathetic Nervous System the division of the autonomic nervous system that calms the body.

THE NEURONSoma or the cell body contains

the cell’s nucleus and is responsible for the cell’s health and well-being.

Dendrites receive messages from other neurons.

Axon transmits information on to additional neurons.

THE NEURON

The Myelin sheath is the layer of fat cells that encases and insulates most axons which help speed up the transmission of nerve impulse.

THE NEURON

The synapse is the branching end of a neuron’s axon reach out to, but do not touch, the dendrites.

1. Acetylcholine (ACh) stimulates the firing of neurons and is involved in the action of muscles, learning, and memory.

Deficiency in ACh will involve decline in memory storage and Alzheimer’s disease.

2. Dopamine mainly inhibits and helps control the voluntary movement.

Dopamine affects sleep, mood, attention and learning (mainly in planning, and the inhibition of irrelevant behaviours and ideas).

3. Serotonin also primarily inhibits. It also regulates sleep and wakefulness, mood, attention and learning.

NEUROTRANSMITTER SUBSTANCES

NEUROTRANSMITTER SUBSTANCES

4. Gamma Aminobutyric Acid (GABA) helps to control the preciseness of the signal being carried from one neuron to the next.

Low level of GABA is linked to anxiety.

5. Norepinephrine usually inhibits the firing of neurons in the central nervous system, but it excites the heart muscle, intestine, and urogenital tract.

Stress stimulates the release of norepinephrine. Too little norepinephrine is associated with depression, and too much is linked with agitated and manic states.

NEUROTRANSMITTER SUBSTANCES

6. Endorphins are natural opiates that mainly stimulates the firing of neurons. It shields the body from pain and elevates feelings of pleasure.

THE NEURON

The Glial cells (neuroglia) provide chemicals that a neuron need to function properly.

they also serve as the clean up crew by removing dead neurons and excess neurotransmitter substances.

THREE KINDS OF NEURONS

Sensory Neuron Interneurons Motor Neurons

Resting Potential-the stable negative charge of an inactive neuron.

Action Potential-the brief wave of electrical charge that sweeps down the axon during the transmission of a nerve impulse.

THE NEURAL IMPULSE

All-or-none Principle-once the electrical impulse reaches a certain level of intensity, it fires and over all the way down to the axon without losing any of its intensity.

BRAIN STRUCTURE AND FUNCTIONS

The human brain has three major components:

1. the hindbrain;2. the midbrain; and 3. the forebrain.

THE HINDBRAIN

The hindbrain is made up of several smaller structures such as the medulla, the pons, and the cerebellum.

THE MIDBRAINThe midbrain is

composed of two parts:

1. the reticular formation (a.k.a. reticular activating system or RAS); and

2. 2. the brainstem.

THE FOREBRAIN The forebrain mainly consists the following:

1. Cerebral cortex2. Limbic system3. Thalamus4. Hypothalamus5. Hippocampus6. Amygdala

1. Frontal lobe is largely responsible for a wide variety of human activities such as:

language attention reasoning planning goal setting self monitoring decision making judgment learning strategies interpreting others’ behaviour

2. Parietal lobes receive and interpret somatosensory information.

3. Occipital lobes

4. Temporal lobes

The Endocrine System is a set of glands that regulate the activities of certain organs by secreting hormones to the bloodstream.

These hormones are chemical messengers that are manufactured by the glands in the system. The endocrine glands include the pituitary, thyroid, parathyroid, and adrenal glands, the pancreas, ovaries, and testes.

THE ENDOCRINE SYSTEM

1. Pituitary Gland-is located at the base of the skull, regulates the secretion of growth hormone and controls all other endocrine glands. It is known as the master gland.The anterior pituitary is controlled by the hypothalamus.

2. Pineal Gland-also located in the brain, it secretes the hormone melatonin, which regulates the sleep and wake cycle.

3. Thyroid Gland-locate inside the neck and secretes a hormone called thyroxin that regulates metabolism (how fast the body burns its available energy).

4. Pancreas-controls the blood sugar level by secreting the insulin and glucagons.

5. Adrenal Glands-one on top of each kidney, produces the main hormone cortisol (steroid).The adrenal glands regulate moods, energy, and the ability to cope with stress.

They secrete epinephrine (adrenaline) and norepinephrine (noradrenaline) in response to stress.

6. Gonads-produces sex hormones responsible for primary and secondary sex characteristics.