PSY290H5 Chapter Notes - Chapter 2: Preganglionic Nerve Fibers, Spinal Cord, Somatic Nervous System
Notes:
● Large collection of cell bodies and axons form the tissues that define the gross
neuroanatomy
○ Neural structures that are visible to the unaided eye
● CNS
○ Central Nervous system → brain and spinal cord
● PNS
○ Peripheral Nervous system
■ Consists of nerves → collections of axons bundled together outside the
central nervous system
■ Motor nerves
● Transmit info from spinal cord and brain to muscles and glands
■ Sensory nerves
● Convey information from the body to the CNS
● Nerves of body into 2 distinct systems - Peripheral NS
○ Somatic nervous system
■ Nerves that interconnect the brain and major muscles (skeletal muscles)
and sensory systems of the body
● Consists of cranial nerves and spinal nerves
○ Autonomic Nervous system
■ Nerves that connect primarily to the viscera (internal organs)
● Spinal cord
○ Cauda Equina
■ Spray of fibers that continues downward inside the spinal column
● Autonomic NS
○ Parasympathetic NS
■ Helps body to relax, prepare for future action
● Rest and Digest response
○ Heart rate drops, BP drops
○ Digestive processes are active
■ Nerves originate in the brainstem (above the sympathetic nerves) and in
the sacral spinal cord
■ Parasympathetic nerves travel a longer distance before terminating in
parasympathetic ganglia which is located close to the organs they serve
● Preganglionic parasympathetic neuron is longer than
preganglionic sympathetic neurons
○ Sympathetic NS
■ Axons exit from the middle parts of the spinal cord, travel a short distance
and then innervate the sympathetic ganglia (small clusters of neurons
found outside the CNS), which run in two chains along the spinal column,
one on each side
■ Axons from the sympathetic ganglia then course throughout the body,
innervating all major organ systems
■ Prepare body for immediate action (Fight of Flight)
● Increase BP, Increase HR
● Pupils of eyes widen
○ Parasympathetic receives the Acetylcholine vs Sympathetic NS receives the
norepinephrine
■ Both are neurotransmitters
○ Balance between two systems determines the state of the internal organs at any
given moment
● Spinal cord
○ Contains circuits that perform local processing and control simple units of
behavior such as reflexes
● Brain
○ Outer surface
■ Weighs about 3lbs (1400 g)
■ Cerebral hemisphere
● One of the two halves - right or left- of the forebrain
○ Cerebral Cortex aka cortex
■ Outer covering of the cerebral hemispheres, which consists largely of
nerve cell bodies and their branches
○ Gyrus
■ Ridges or raised portion of a convoluted brain surface
○ Sulcus
■ A crevice or valley of a convoluted brain surface
● Brain
○ Lumpy, convoluted surface
■ Elaborate folding of a thick sheet of tissue, mostly the dendrites, cell
bodies and axonal projections of neurons called the cerebral cortex
○ Resultant ridges of tissue called gyri (singular gyrus) separated from each other
by crevices called sulci (singular sulci)
○ Folding up the tissue → increases the amount of cortex that can be crammed into
the confines of skull
■ About ⅔ of cerebral cortex is hidden in the depths of these folds
○ Pattern of folding is not random
■ It is similar enough between brains that we can name the various gyri and
sulci and group them together into lobes
● Sympathetic NS
■ Thoracic lumbar
○ Consists of sympathetic ganglia and axons that lead to the organs
○ Helps prepare for Fight or Flight
● Parasympathetic NS
■ Cranial sacral
○ Arises from both the brain (cranial) and sacral parts of the spinal cord
○ Helps prepare for Rest and Digest
Document Summary
Large collection of cell bodies and axons form the tissues that define the gross. Neural structures that are visible to the unaided eye. Central nervous system brain and spinal cord. Consists of nerves collections of axons bundled together outside the central nervous system. Transmit info from spinal cord and brain to muscles and glands. Convey information from the body to the cns. Nerves of body into 2 distinct systems - peripheral ns. Nerves that interconnect the brain and major muscles (skeletal muscles) and sensory systems of the body. Consists of cranial nerves and spinal nerves. Nerves that connect primarily to the viscera (internal organs) Spray of fibers that continues downward inside the spinal column. Helps body to relax, prepare for future action. Nerves originate in the brainstem (above the sympathetic nerves) and in the sacral spinal cord. Parasympathetic nerves travel a longer distance before terminating in parasympathetic ganglia which is located close to the organs they serve.
