Nervous System 1 - Super 7 List.docx

Nervous System I – Super 7 Organization of the nervous system Central nervous system (CNS) Includes the brain and spinal cord Integrates sensory input and directs motor output Peripheral NS (PNS) Includes nerves and ganglia (cell bodies) outside the CNS Has two divisions: sensory (afferent) and...

Nervous System I – Super 7 Organization of the nervous system Central nervous system (CNS) Includes the brain and spinal cord Integrates sensory input and directs motor output Peripheral NS (PNS) Includes nerves and ganglia (cell bodies) outside the CNS Has two divisions: sensory (afferent) and motor (efferent) Sensory goes to the CNS and it involves somatic fibers (from skin, skeletal muscles, joints) and visceral fibers (from visceral organs) Motor travels from the CNS and it has two divisions: somatic and autonomic Somatic NS controls skeletal muscles and is voluntary Autonomic NS (ANS) controls smooth muscle, cardiac muscle, and glands Parasympathetic and Sympathetic are two divisions of the ANS Neuron, Neuroglia, and Synapse anatomy and classification Neurons: respond to stimuli by conducting impulses – Anatomy: Cell body Neurofibrils maintain shape Nissil bodies are rough endoplasmic reticulum Plasma membranes act as receptors Bodies within CNS called nuclei Bodies outside CNS called ganglia – Processes: Axon Transmit impulses away from (anterograde) and to (retrograde) cell body Terminals secrete neurotransmitters Hillock connects body to axon and is the threshold area Microtubules serve as pathways for transport – Processes: Dendrites Input region Create big surface area to receive signals Form synapses – Myelin Sheath Not on all axons Made of Schwann cells that protect and increase speed of transmission Schwann cell wraps itself around axon and forces its own cytoplasm to the outer layers Oligodendrocytes form myelin sheath in CNS – Nodes of Ranvier Gaps on axon between myelin sheath – Neuron classification by structure Multipolar: one axon and at least two dendrites; abundant; most in CNS Bipolar: one axon, one dendrite; retina and olfactory mucosa Unipolar: one process that divides into two branches Classification by function Sensory: to CNS; unipolar Motor: from CNS; multipolar Interneurons: in CNS; between sensory and motor neurons; multipolar Synapses transfer information between neurons Chemical synapses Use neurotransmitters in synaptic vesicles to relay message to receptor sites on receiving neuron Synaptic cleft separates neurons Electrical synapses Contain gap junctions that can facilitate bidirectional transmission Abundant in embryonic tissue Neuroglia support neurons CNS: Astrocytes - most abundant; surround cell body; capillary permeability; clean up leaked K; recycle neurotransmitters Microglial cells - become macrophages Ependymal cells - line inside of spinal cord and brain; contain cilia Oligodendrocytes - form myelin sheath on CNS fibers PNS: Satellite cells- similar to astrocytes Schwann cells- myelin sheath; regeneration of fibers Cerebrospinal Fluid (CSF) Function: Reduces brain weight by 97% Protects CNS Nourishes brain Rids waste Composition: Formed by plasma (less protein, Ca, K; more Na, Cl, H ions, glucose, O2, and vitamins) Circulation: Made in choroid pluxes of ventricle lined with ependymal cells> flows into subarachnoid space via medial and lateral apertures> absorbed through arachnoid granulations into venous sinus blood CNS structures and brief functions Cerebrum Frontal lobe: motor cortex, prefrontal cortex (cognition), Broca’s area (speech production) Parietal lobe: somatosensory cortex Occipital lobe: vision Temporal lobe: Wernicke’s area (language comprehension), auditory Cerebral Hemispheres Left: controls right side of body; dominant; language Right: controls left side of body; creativity; tone of language Both communicate via Corpus collosum Both have basal nuclei (controls voluntary movement) Brain Stem Midbrain: nuclei for cranial nerves iii and iv Pons: rhythm of breathing Medulla: heart rate/ force, blood pressure; respiratory rate and depth Reticular Formation: prevents sensory overload by filtering weak and strong information; sleep cycle: RAS keeps brain “awake” Diencephalon Thalamus: two bilateral structures; information relay station; part of limbic system Hypothalamus: relay station for olfaction; infundibulum connects pituitary gland; ANS control; temperature; food intake; thirst; controls endocrine function Epithalamus: contains pineal gland (melatonin) Cerebellum Control of timing and coordination of voluntary movements Spinal Cord Organization and Major Tracts Ascending tracts (sensory) Fasciculus Cuneatus and Gracilis tracts: fine touch and pressure Spinothalamic: pain, temperature, gross touch Spinocerebellar: stretch; go to cerebellum Descending tracts (motor) Corticospinal: from motor cortex Somatosensory organization and types of receptors Sensory receptors by stimulus type Mechanoreceptors: touch, pressure, stretch, vibration Thermoreceptors: temperature Chemoreceptors: chemicals Photoreceptors: light Nociceptors: pain, inflammatory chemicals (histamine, bradykinin) Sensory receptors by location Exteroreceptors: stimuli from outside body; superficial receptors Interoreceptor: stimuli from inside Proprioceptors: internal on muscles, joints, tendons, and ligaments Receptors by receptor type Nonencapsulated nerve endings: tactile discs are light touch receptors; hair follicle receptors feel bending of hair Encapsulated nerve endings: surrounded by connective tissue; includes tactile corpuscles, lamellar corpuscles, bulbous corpuscles, muscle spindles, tendon organs, and joint kinesthetic receptors Somatosensory System Input from exteroreceptors, interoreceptors, and proprioceptors Three levels of interpretation: Receptor level: for sensation to occur stimulus must match specificity of receptor, stimulus must be in receptive field, energy must be changed to graded potential, and that potential must reach threshold Circuit level: delivery to cortex Perceptual level: interpretation depends on location of target neuron in brain; intensity and location of stimulus; complexity of stimulus; able to recognize patterns of stimuli Autonomic Nervous System Parasympathetic Sympathetic Originates in the brainstem and sacrum Originates in the thoracic and lumbar Ganglia in or near effector organs Ganglia close to spinal cord Long preganglionic axon, short post Short preganglionic axon, long post Releases acetylcholine (Ach) Releases Ach at ganglion, norepinephrine at effector organ Sweat glands, arrector pili muscles, and vessels only activated by sympathetic NS Cell bodies in motor nuclei of brainstem and lateral grey matter of spinal cord Cell bodies in later horns of spinal cord Rest and digest Fight or flight