Introduction Control and communication center of the body interprets incoming data Fight or flight Generates thoughts Controls behaviors

Organs Brain Spinal Cord Nerves Specialized sense organs Eyes, ears and skin receptors

Neuron Neuron = Nerve cell Transmits information from one cell to another Can amplify or dampen signal Consist of cell body, dendrites and an axon Three main types of neuron: Sensory Neurons Motor Neurons Associative Neurons

Sensory Neurons Afferent neurons Emerge from sensory organs (ex. Skin) Transmit impulses toward the brain or spinal cord

Motor Neurons Efferent Neurons Carry impulses away from the brain or spinal cord to muscles and glands of the body

Associative Neurons Interneurons Carry impulses from sensory neurons to motor neurons

Structure Cytoplasmic extentions - Dendrite: receives information Cells may have several, one or none Typically short and branched Axon: Transmits impulses away Cell has only one Long Branch at their ends – Axon Terminals Make contact with dendrites of other neurons

Structure Cont. Multipolar: neuron with many dendrites Most neurons of the brain and spinal cord Bipolar: neuron with only one dendrite Receptor cells in: inner ear, nose, retina Unipolar: only one extension; serves as both an axon and a dendrite

Myelin Sheath Neurilemma Insulating material that covers axon of neuron Similar to plastic around electrical wire Gives nerves there white appearance Made up of Schwann Cells (neurolemmocytes) Nodes of Ranvier: Gaps on myelin sheath Gaps allow substances (needed for energy) to flow from extracellular fluid to axons Capable of regeneration. Not found in brain or spinal cord.

Neuroglial Cells Insulate, support, and protect neurons Do not conduct nerve impulses Schwann Cells Astrocytes: Star shaped Part of the blood brain barrier Oligodendroglial cells: Support Create myelin located in the brain and spinal cord Microglial cells: Protect neurons (phagocytosis) Ependymal Cells: Produce CSF in ventricals Help to move CSF

Nerves A group of peripheral nerve fibers Each axon is surrounded by endoneurium Wrapped axons are grouped fascicles Fascicles are surround by perineurium The whole nerve is covered by epineurium

A self-propagating wave of electrical disturbance Must be initiated by a stimulus Resting neurons have a slight positive charge on the outside and a slight negative charge on the inside Nerve Impulses

When the membrane is stimulated, sodium rushes in causing a reverse of the charges If the membrane is covered in myelin, the impulse jumps in what is called saltatory conduction Nerve Impulses, cont’d

Synapse Three structures: Synaptic knob Synaptic cleft Plasma membrane of the postsynaptic neuron

Synapse Area between the terminal branches of an Axon and the ends of a branched Dendrite Axons and Dendrites never actually touch. Nerve signals “jump” the space between the two called the synaptic cleft How do nerve signals jump? Neurotransmitters

Neurotransmitters Neurotransmitters: chemical messengers, found in synaptic knobs Acetycholine Epinephrine (autonomic) Dopamine Seratonin Endorphins Enkephalins

Synapse and Synaptic Cleft

Reflex Arcs Involuntary reaction to an external response. Two neuron and three neuron arcs Only allow impulse conduction in one direction Starts at the beginning of dendrites to its cell body in the ganglion,

Reflex Arcs The dendrites of the sensory neuron pick up a signal and send it to the cell body in the ganglion. The axon of the sensory neuron travels from the cell body and ends near the dendrites of a motor neuron. The signal jumps the synapse and is sent down the dendrites to the cell body and to the axon of the motor neuron to the “effectors” organ

Functions Sensory Integrative Motor

Reflex Arcs 3 Neuron Reflex The sensory neuron’s axon synapses with the dendrites of the interneuron The signal is send down the interneuron to the dendrites of the motor neuron The “withdrawal” reflex All interneurons lie within the gray matter of the brain and spinal cord

Day 2

Divisions of the Nervous System Central Nervous System Brain Spinal Cord Peripheral Nervous System Nerves Cranial Nerves Spinal Nerves

Divisions of the PNS Somatic Nervous System (SNS): Connects CNS to Skin, Skeletal Muscle Initiates voluntary responses Autonomic Nervous System (ANS): Connects the CNS to Visceral Organs Initiated involuntary responses Sympathetic Fight or Flight Parasympathetic Restores homeostatic balance

Divisions Brainstem Medulla oblongata Pons Midbrain Cerebellum Diencephalon Hypothalamus Thalamus Cerebrum

The Brain Responsible for all human physical and mental functions Gray Matter: Cell Bodies White Matter: bundles of Axons (covered in Myelin)

Meninges Protective tissues that surround the brain and spinal cord Dura (outermost) Tough fibrous connective tissue Does not attach directly to the vertebrae. Space between vertebra and dura is termed Epidural space Arachnoid Thin, weblike Pia Space between the arachnoid and pia layers is termed the subarachnoid space

Cerebral Cortex Surface layer of the brain

Cerebrum Largest portion of the human brain Gyri: convolutions Sulci: deep grooves (fissures) Divided into two hemispheres by the Longitudinal Fissure Transverse Fissure: separates the cerebrum from the cerebellum

Cerebrum Cont. Right Hemisphere: Nonverbal, intuitive behaviors Left Hemisphere: Speech, computational, analytical skills What hemisphere dominates you? 90% Left

Cerebrum Cont. Sulci and gyri also divide the cerebrum into lobes named for the bone that covers it: Frontal Temporal Parietal Occipital

Ventricles & CSF Interconnected canals and cavities Filled with clear, colorless fluid (CSF)

Cerebellum Essential role in movements Produces smooth, coordinated movements, maintain equilibrium, and sustain normal posture Bell shaped structure under the occipital lobe

Diencephalon Consists of 2 major structures Hypothalamus helps control vital functions, water balance, and body temp. Thalamus helps produce sensations and associates sensations with emotions

Mesencephalon Midbrain Contains white matter and gray matter

Brainstem Composed of 3 structures Medulla-upward extension of spinal cord located above foramen magnum.

Blood Supply Carotid artery Anterior cerebral artery Middle cerebral artery Median anterior spinal artery

Spinal Cord Provides two-way conduction Ascending tracts direct impulses to the brain Descending tracts direct impulses away from the brain

Day 3

Cranial Nerves I – Olfactory II – Optic III – Oculomotor IV – Trochlear V – Trigeminal VI – Abducens VII – Facial VIII – Vestibulocochlear IX – Glossopharyngeal X – Vagus XI – Accessory XII – Hypoglossal

Cranial Nerves Cont.

Spinal Nerves 31 total 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal

Neoplasms Primary- neural tissues or meninges Secondary- metastatic lesions Intracranial tumors- diagnosed with CT Compression Destruction Irritation Increase intracranial pressure