Central Nervous System •Central nervous system (CNS) •brain and spinal cord enclosed in bony coverings •Functions of the spinal cord •spinal cord reflexes •integration (summation of inhibitory and excitatory) nerve impulses •highway for upward and downward travel of sensory and motor information •Brain functions •sensations, memory, emotions, decision making, behavior 14-1
53
Embed
Central Nervous System Central nervous system (CNS) brain and spinal cord enclosed in bony coverings Functions of the spinal cord spinal cord reflexes.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Central Nervous System
• Central nervous system (CNS)• brain and spinal cord enclosed in bony coverings
• Functions of the spinal cord• spinal cord reflexes• integration (summation of inhibitory and excitatory) nerve
impulses• highway for upward and downward travel of sensory and
• 3 Fibrous layers enclosing spinal cord• Dura mater
• tough collagenous membrane surrounded by epidural space filled with fat and blood vessels
• epidural anesthesia utilized during childbirth
• Arachnoid mater• layer of simple squamous epithelium lining dura mater and
loose mesh of fibers filled with CSF(creates subarachnoid space)
• Pia mater• delicate membrane adherent to spinal cord
14-6
Meninges of Vertebra and Spinal Cord
14-7
Cross-Sectional Anatomy of the Spinal Cord
• Central area of gray matter shaped like a butterfly and surrounded by white matter in 3 columns
• Gray matter = neuron cell bodies with little myelin• White matter = myelinated axons
14-8
Gray Matter in the Spinal Cord
• Pair of dorsal or posterior horns• dorsal root of spinal nerve is totally sensory fibers
• Pair of ventral or anterior horns• ventral root of spinal nerve is totally motor fibers
• Connected by gray commissure punctured by a central canal continuous above with 4th ventricle
14-9
White Matter in the Spinal Cord• White matter of the spinal cord surrounds the gray matter
• White column = bundles of myelinated axons that carry signals up and down to and from brainstem
• 3 pairs of columns or funiculi• Dorsal, lateral, and anterior columns• Tracts or fasciculi - subdivisions of each column• Ascending and descending tract head up or down • Contralateral means origin and destination are on opposite sides while ipsilateral
• Carry information from receptors to posterior horn of spinal cord or the brainstem
• Integrating center• Part of the CNS that processes the information and generates response
• Motor neuron• Transmits the response to the effector
• Effector • Muscle or gland
• 4 important somatic spinal reflexes• Stretch reflex - when a muscle is stretched, it “fights back” and contracts • Tendon reflex - contraction of a muscle when its tendon is tapped
• in response to excessive tension on the tendon
14-21
The Patellar Tendon Reflex Arc
14-22
Central Nervous System-The Brain
14-23
• Evolution of the central nervous system shows spinal cord has changed very little while brain has changed a great deal• Greatest growth in areas of vision, memory, and motor control of the
• Cerebrum is 83% of brain volume; cerebral hemispheres, gyri and sulci, longitudinal fissure, corpus callosum
• Cerebellum contains 50% of the neurons; second largest brain region, located in posterior cranial fossa
• Brainstem is the portion of the brain that remains if the cerebrum and cerebellum are removed; diencephalon, midbrain, pons, and medulla oblongata
Gray and White Matter
• Gray matter = neuron cell bodies, dendrites, and synapses• forms cortex over cerebrum and cerebellum• forms nuclei deep within brain
• White matter = bundles of axons• forms tracts that connect parts of brain
14-26
Meninges of the Brain
14-27
Brain Ventricles
14-28
• Ventricles - four internal chambers within the brain• Two lateral ventricles: one in each cerebral hemisphere
• Interventricular foramen—a tiny pore that connects to third ventricle• Third ventricle: single narrow medial space beneath corpus callosum
• Cerebral aqueduct runs through midbrain and connects third to fourth ventricle• Fourth ventricle: small triangular chamber between pons and cerebellum
• Connects to central canal, runs down through spinal cord• Ependyma - neuroglia that lines the ventricles and covers choroid plexus
• Produces cerebrospinal fluid
• Choroid plexus - spongy mass of blood capillaries on the floor of each ventricle
Cerebrospinal Fluid
• Fills ventricles and subarachnoid space
• Brain produces and absorbs 500 ml/day• choroid plexus creates by filtration of blood
• Functions• floats brain so it is neutrally buoyant• cushions from hitting inside of skull• chemical stability -- rinses away wastes
chemicals, body temperature, and other internal stimuli• Afferent neurons: leading to the CNS• Interneurons: in the CNS• Efferent neurons: carry motor signals away from the CNS• Effectors: that make adjustments
• ANS modifies effector activity
15-45
Visceral Reflexes
• Example of homeostatic negative feedback loop
• High blood pressure detected by arterial stretch receptors (1), afferent neuron (2) carries signal to CNS, efferent (3) signals travel to the heart, then (4) heart slows reducing blood pressure
• Nerve impulses of these motor neurons start in the CNS (medulla oblongata and pons)
• Pathway through:• Spinal cord• Cranial nerves
14-46
Divisions of the ANS
• Two divisions innervate same target organ• May have cooperative or contrasting effect• Prepares body for physical activity: exercise, trauma, arousal,
competition, anger, or fear• Increases heart rate, BP, airflow, blood glucose levels, etc.• Reduces blood flow to the skin and digestive tract
15-47
Sympathetic Division
• The sympathetic division is called the “fight or flight” system
• when the body needs to generate energy• exercise, excitement, emergency, and embarrassment