The central and peripheral system Nervous system The central and peripheral system

A few terms Nerve fiber (single neuron) – an axon extension Nerve – peripheral system: group of many nerve fibers traveling together to the same location Pathway/tract – group of nerve fibers in the CNS Ganglia – group of cell bodies in PNS Nuclei – group of cell bodies in CNS Gray matter – made primarily of cell bodies White matter – primarily myelinated fibers

Subdivisions of the brain Cerebrum Diencephalon Brain stem includes the midbrain, pons & medulla oblongata cerebellum

Cerebral ventricles Four interconnected fluid filled cavities http://www.arthursclipart.org/medical/nervous/cerebral%20ventricles.gif

Cerebrum Plays a role in perception, movement, reasoning, learning, and memory Most complex integrating system of brain Incoming information is processed and made into meaningful ideas Fine tunes skeletal muscle movements http://www.a2zpsychology.com/images/BIOLOG7.GIF

Diencephalon - Thalamus Thalamus – a group of large nuclei that integrates information coming in from the senses before they are sent onto the cerebrum. Plays a role in awareness and focused attention & skeletal coordination. http://www.thebrainwiki.com/uploads/Forebrain/thalamus.jpg

Diencephalon - Hypothalamus Control center for neural and endocrine coordination. In charge of homeostasis. Regulates pituitary gland Regulates water balance, eating, drinking, reproduction, body temperature, circadian rhythms Plays role in behaviors, emotional behavior & control of autonomic nervous system http://www.colorado.edu/intphys/Class/IPHY3430-200/image/Hypothalamus.jpg

Lymbic system Interconnected group of brain tissues that include the diencephalon and parts of the cerebrum Plays essentional role in learning, emotional experience and behavior, visceral and endocrine functions Mostly controlled by hypothalamus

Cerebellum Coordinates movements, controls posture and balance. Receives information from muscles, joints, skin & viscera

Brainstem Contains all the nerve fibers that pass between the brain and spinal cord Reticular formation – control of cardiovascular and respiratory system, regulation of sleep, wakefulness and focus attention

Spinal cord Gray matter surrounded by white matter Afferent enter on the dorsal side, efferent on the ventral side

Peripheral nerves 43 pairs of nerves 12 are cranial & 31 are spinal Afferent neurons (primary afferents) are the first cells to enter the CNS & bring information from the senses and organ systems into the CNS.

Somatic vs autonomic innervation McGraw Hill, Human Physiology, Vander, Sherman, & Luciano

Subdivisions of the efferent neurons Because there are many possible responses as a result of the firing of the efferent neurons (move left arm up, breathe faster, digest slower, cross legs) it is broken into divisions. Somatic nervous system – controls conscious movements Autonomic nervous system – responses that occur w/o our conscious awareness

Somatic nervous system The efferent nerves that enter skeletal muscle tissue. Cell bodies are located in groups in the brainstem or spinal cord. long axon travels from CNS directly to skeletal muscle with no other synapse Release ACh Impulses along these nerves only cause contraction of skeletal muscle. Also called motor neurons

Innervation of left arm http://www.nature.com/nrn/journal/v4/n7/images/nrn1141-f1.jpg

Autonomic nervous system Efferent nerves that travel from the CNS to cardiac & smooth muscle, glands and digestive tissues. Has two neurons. One that travels from CNS to peripheral synapse & the second that leads from the synapse to the target cells/organ. Primarily ACh is released at the synapse Can excite or inhibit tissue

Divisions of autonomic system

Sympathetic Originate from the cervical, thoracic & lumbar region of spinal cord Ganglia close to CNS Many of the neurons act on the same tissue Acts as a single unit producing a coordinated response Norepinephrine is the major transmitter at the effector/target cell Responsible for “fight or flight” response

Parasympathetic Originate from the brain stem and sacral region spinal cord Ganglia are just out side of the target organ or in the target tissue itself Nerves are mostly independent Finely tune to specific needs of body ACh is the major neurotransmitter at the effector cell Responsible for homeostatic function “rest or digest”

Adrenal medulla Special ganglion in the sympathetic nervous system Does not have axons Releases substances into the blood, thus called horomones Hormones released travel through blood to target organs

Peripheral neurotransmitters McGraw Hill, Human Physiology, Vander, Sherman, & Luciano