Nervous System: An Introduction HAP Susan Chabot Lemon Bay High School
Function of the Nervous System 3 overlapping functions SENSORY INPUT - Monitor changes inside and outside of the body; these changes are called STIMULI. INTEGRATION - Processes and interprets changing stimuli to decide. MOTOR OUTPUT - Effects a response via activating effectors (muscles or glands).
Working Together The Nervous System works with the Endocrine System to provide ELECTRICAL and CHEMICAL control of ALL body processes.
Structural Organization Nervous System Central Nervous System Peripheral Nervous System Brain and Spinal Cord All neurons not in brain or spinal cord Responsible for Integration Responsible for sensory input and motor output
Functional Organization Peripheral Nervous System Sensory/Afferent Moves information TOWARD the CNS Motor/Efferent Moves information AWAY FROM the CNS Autonomic Involuntary control of smooth and cardiac muscles and all glands Somatic/Motor Voluntary control of skeletal muscles Sympathetic Fight-or-Flight Parasympathetic Resting-or- Digesting
Autonomic Continuum Rest or Digest Fight or Flight
Cells of the Nervous System 2 categories Neurons transmit electrical impulses Sensory neurons = receptors Integration neurons = integrate/think Motor neurons = effect a change through muscles and/or glands Neuroglia = Nerve glue Protect, insulate, and support delicate neurons
Cells of the Nervous System Neuroglia = Nerve Glue Astrocytes Star-shaped cell that provides a scaffold to hold neurons in specific locations. Oligodendrocytes Insulates neurons for speedy transmission of electrical impulses; similar to insulation for electrical wires. Ependymal Cells Produces cerebrospinal fluid (CSF) Microglial cells Small white blood cells that destroy pathogens and cell debris.
Cells of the Nervous System Neurons/Nerves 3 main parts Dendrite: receives info from neighboring neurons. Cell body: living portion of the neuron; contains the nucleus and organelles. Axon: sends info to neighboring neurons.
Appearance Location Function BiPolar 2 extensions on opposite ends of cell body Special senses in skull Collect sensory info for sight, hearing, smell, taste UniPolar 1 continuous extension, cell body pushed to side Special senses far from brain Collect sensory info for pain, pressure, touch MultiPolar Many dendrites, single long axon Brain Form networks that span distance Anaxonic Cannot tell dendrites from axon Brain Form close-knit networks
Bipolar Unipolar Multipolar Anaxonic
Neuronal Networks Connection of individual neurons Forms synapses Axon and dendrite(s) The more dendrites communicating with a single neuron, the wider the network
Synapses Connection between 2 neurons Axon (neuron #1) and Dendrite (neuron #2) Stimulation of neuron causes release of neurotransmitter into the synapse Neurotransmitter must dock onto membrane of next neuron for simulation to continue
Synapses Space in between neighboring neurons. Contains neurotransmitters; chemicals that are released to control info/activity in brain. Types of Synapses Neuron-to-Neuron Found throughout Nervous System Neuron-to-Muscle Neuromuscular Neuron-to-Gland Neuroglandular
Protection of the CNS Review Bones of skull Structure of vertebrae Offer solid protection of Lobes of brain Concentration of nerves in spinal cord
Protection of the CNS Meninges What Are They? Connective tissue outer protection coverings of the brain. What is the function? Intact covers to prevent infection and stability Layers Dura mater Tough; lies just under skull Arachnoid mater Spider-like extensions; Circulates CSF Pia mater Delicate/thin; adheres directly to brain
CSF = Cerebrospinal fluid What is It? Watery substance Contains a balance of nutrients and salts/ions How is it Formed? By EPENDYMAL CELLS in a dense capillary bed called the CHOROID PLEXUS A capillary bed is a group of very small blood vessels closely connected How is it circulated? Found in the arachnoid mater of the meninges Surrounds brain and spinal cord Constantly moving How Does it Offer Protection? Bathes the brain and cushions from trauma.
Meninges
Protection of the CNS Blood-brain barrier What is It? A tight network of capillary beds that are both SELECTIVE - Keeps some things out and other allows other things in. DIRECTIONAL - Moves INTO the brain not OUT OF the brain How Does it Work? Acts as a successively smaller filters to keep substances from entering the circulation of the brain and spinal cord.
Lobular Organization
Divisions of the Brain Cerebral Cortex: high order processes; speech, language, cognition. Cerebellum: responsible for the coordination of muscle activity. Pons: relays sensory info from the cerebellum to the cerebral cortex. Medulla oblongata: the primitive brain; controls heart rate, respirations, hunger, thirst. Diencephalon: important in the integration of the nervous and endocrine system/temperature control
The Brain
Structural Organization Cerebrum Processing Integration Memory storage
Structural Organization Cerebellum Adjusts ongoing movement Muscle memory
Structural Organization Diencephalon Thalamus Relay center Hypothalamus Emotions Autonomic functions Hormone production
Structural Organization Mesencephalon Visual and auditory processing Reflex control Maintains consciousness
Structural Organization Pons Connects brainstem to cerebellum Somatic and visceral motor control.
Structural Organization Medulla Oblongata Regulates heart rate, blood pressure, and digestion
Cranial Nerves
Cranial Nerves Number Name Function Sensory, Motor, Both? I Olfactory Smell S II Optic Sight S III Oculomotor Moves eye/pupil M IV Trochlear Moves eye M V Trigeminal Face sensations B VI Abducens Moves eye M VII Facial Moves face; salivates B VIII Vestibulocochlear Hearing; balance S IX Glossopharyngeal Taste; swallow B X Vagus Heart rate; digestion B XI Accessory Moves head M XII Hypoglossal Moves tongue M