The Nervous System and the Endocrine System
Neurons: The Building Blocks of the Nervous System
Nervous System The electrochemical communication system of the body Sends messages from the brain to the body for movement Brings information to the brain from the senses
Neuron A nerve cell; the basic building block of the nervous system Neurons perform three basic tasks Receive information Carry the information Pass the information on to the next neuron
Parts of the Neuron - Terminals Axon terminals The endpoint of a neuron where neurotransmitters are stored
How Neurons Communicate: The Neural Impulse
Action Potential A neural impulse; a brief electrical charge that travels down the axon of a neuron Considered an on condition of the neuron
Refractory Period The recharging phase during which a a neuron, after firing, cannot generate another action potential Once the refractory period is complete the neuron can fire again
Resting Potential The state of a neuron when it is at rest and capable of generating an action potential The neuron is set and ready to fire
All-or-None Principle The principle stating that if a neuron fires it always fires at the same intensity All action potentials are of the same strength. A neuron does NOT fire at 30%, 45% or 90% but at 100% each time it fires.
How Neurons Communicate: Communication Between Neurons
Synapse The tiny, fluid filled gap between the axon terminal of one neuron and the dendrite of another neuron The action potential cannot jump the gap
Neurotransmitters A chemical messenger that travels across the synapse from one neuron to the next Can influence whether the second neuron will generate an action potential or not
Neurotransmitters
Neurotransmitters
Excitatory Effect A neurotransmitter effect that makes it more likely that the receiving neuron will generate an action potential or fire The second neuron is more likely to fire.
Inhibitory Effect A neurotransmitter effect that makes it less likely that the receiving neuron will generate an action potential or fire The second neuron is less likely to fire.
How Neurons Communicate: The Neural Chain
Receptor Cells Specialized cells in the sensory systems of the body that can turn other kinds of energy into action potentials (neural impulses) that the brain can process Receptor cells in the eye turn light into a neural impulse the brain understands.
Sensory Nerves Nerves that carry information from the sensory receptors to the spinal cord and brain. Connect the sense organs to the brain and spinal cord
Interneurons Nerve cells in the brain and spinal cord responsible for processing information Related to sensory input and motor output
Motor Nerves Nerves that carry information from the brain and spinal cord to the muscles and glands. Carries messages from the brain and spinal cord to other parts of your body
The Structure of the Nervous System
The Nervous System
Central Nervous System (CNS) The brain and spinal cord The brain is the location of most information processing. The spinal cord is the main pathway to and from the brain.
Peripheral Nervous System (PNS) The sensory and motor nerves that connect the brain and the spinal cord to the rest of the body Peripheral means outer region The system is subdivided into the somatic and autonomic nervous systems.
Somatic Nervous System The division of the peripheral nervous system that controls the body s skeletal muscles Contains the motor nerves needed for the voluntary muscles
Autonomic Nervous System The division of the peripheral nervous system that controls the glands and muscles of the internal organs Monitors the autonomic functions Controls breathing, blood pressure, and digestive processes Sub-divided into the sympathetic and parasympathetic nervous systems
Sympathetic Nervous System The part of the autonomic nervous system that arouses the body to deal with perceived threats Fight or flight response
Parasympathetic Nervous System The part of the autonomic nervous system that calms the body Brings the body back down to a relaxed state
The Endocrine System
Endocrine System One of the body s two communication systems A set of glands that produce hormones-- chemical messengers that circulate in the blood
Hormone Chemical messengers produced by the endocrine glands and circulated in the blood Similar to neurotransmitters in that they are also messengers Slower communication system, but with longer lasting effects
Pituitary Gland The endocrine system s gland that, in conjunction with the brain, controls the other endocrine glands Called the master gland Located at the base of the brain and connects to the hypothalamus
Thyroid Gland Endocrine gland that helps regulate the energy level in the body Located in the neck
Adrenal Gland Endocrine glands that help to arouse the body in times of stress Located just above the kidneys Release epinephrine (adrenaline) and norepinephrine (noradrenaline)
Pancreatic Gland Regulates the level of blood sugar in the blood
Sex Glands Ovaries (females) and testes (males) are the glands that influence emotion and physical development. Testosterone primary males hormone Estrogen primary female hormone Males and females have both estrogen and testosterone in their systems.
Lower-Level Brain Structures: The Brainstem
Brainstem The oldest part and central core of the brain; It begins where the spinal cord swells as it enters the skull Is responsible for automatic survival functions
Medulla Located at the base of the brainstem Controls life-supporting functions like heartbeat and breathing Damage to this area can lead to death.
Reticular Formation A nerve network in the brainstem that plays an important role in controlling wakefulness and arousal Extending up and down the spinal cord into the brain Controls an organism s level of alertness Damage to this area can cause a coma.
Lower-Level Brain Structures: The Thalamus
Thalamus Sits atop the brainstem The brain s sensory switchboard Directs messages to the sensory receiving areas in the cortex Thalamus is Greek for inner chamber.
Lower-Level Brain Structures: The Cerebellum
Cerebellum Latin for the little brain Attached to the rear of the brain Helps coordinate voluntary movements and balance If damaged, the person could perform basic movements but would lose fine coordination skills.
Lower-Level Brain Structures: The Limbic System
Limbic System A ring of structures at the border of the brainstem and cerebral cortex Helps regulate memory, aggression, fear, hunger, and thirst Includes the hypothalamus, hippocampus, and amygdala
Hypothalamus A neural structure lying below the thalamus Regulates the body s maintenance activities such as; eating, drinking, body temperature, and it linked to emotion Plays a role in emotions, pleasure, and sexual function
Hippocampus A neural center located in the limbic system that wraps around the back of the thalamus Helps processing new memories for permanent storage Looks something like a seahorse Hippo is Greek for horse.
Amygdala Two almond shaped neural cluster in the limbic system Controls emotional responses such as fear and anger
The Cerebral Cortex
Cerebral Cortex The intricate fabric of interconnected neurons that form the body s ultimate control and information processing center Covers the brain s lower level structures Contains an estimated 30 billion nerve cells Divided into four lobes
Corpus Callosum The large band of neural fibers that connects the two brain hemispheres and allows them to communicate with each other Is sometimes cut to prevent seizures
Longitudinal Fissure The long crevice that divides the cerebral cortex into left and right hemispheres This and other fissures in the brain create major divisions in the brain called lobes
Frontal Lobes The portion of the cerebral cortex lying just behind the forehead Is involved in planning and judgments Includes the motor cortex
Parietal Lobes The portion of the cerebral cortex lying on the top of the head and toward the rear Includes the somatosensory cortex and general association areas used in processing information Regions available for general processing, including mathematical reasoning Designated as the association lobes Behind the frontal lobes
Occipital Lobe The portion of the cerebral cortex lying at the back of the head It includes the primary visual processing areas of the brain
Temporal Lobes Includes the auditory (hearing) areas of the brain Where sound information is processed Located roughly above the ears
Motor Cortex The strip of brain tissue at the rear of the frontal lobes Controls voluntary movement Different parts of the cortex control different parts of the body. The motor cortex in the left hemisphere controls the right side of the body and visa versa.
Somatosensory Cortex The brain are located in the front of the parietal lobes Registers and processes body sensations Soma is Greek for body.
Differences Between the Two Hemispheres
Hemispheric Differences Left-brained and right-brained debunked Brain is divided into two hemispheres but works as a single entity. Both sides continually communicate via the corpus callosum, except in those with split brains.
Differences Between the Two Hemispheres: Language and Spatial Abilities
The Brain s Left Hemisphere For most people, language functions are in the left hemisphere. For a small percentage of people, language functions are in the right hemisphere.
Broca s Area The brain area of the left frontal lobe Directs the muscle movements involve in speech If damaged the person can form the ideas but cannot express them as speech
Wernicke s Area A brain area of the left temporal lobe Involved in language comprehension and expression Our ability to understand what is said to us Usually in the left temporal lobe
The Brain s Right Hemisphere Houses the brain s spatial abilities Our spatial ability allows us to perceive or organize things in a given space, judge distance, etc. Helps in making connections between words