Nervous system
Roman Jauregui Pr 2
Major functions of the nervous system
Major divisions and subdivisons
sensory input, integration, and processing (decision making), and motor output (response).
Central Nervous System (CNS) : Made up of the brain and Spinal Cord, resposible for integration of information and decision making.
Peripheral Nervous System (PNS) : Made up of cranial and spinal nerves that connect the CNS to the rest of the body
Contains sensory (afferent) and motor (efferent) divisions.
Somatic nervous system : controls voluntary skeletal muscles
Autonomic nervous system : controls involuntary effectors (smooth and cardiac muscle glands)
Tissues (structure and funtions of neurons and neorglia)
Neuroglia : cells that support neurons
Functions : fill spaces, structurally support, protect, and insulate neurons.
Do not generate ofr conduct nerve impulses
4 types in CNS, 2 types in CNS
A neuron contains a cell body, tubular cytoplasm-filled dendrites, and a tubular, cytoplasm-filled axon
dendrites conduct impulses towards the cell body; it arises from a thickening extending from the cell body, called the axon hillock
Larger axons are enclosed by myelin sheaths; they are called myelinated fibers
Classification of Nuerons
Multipolar Neurons : have many dendrites and one axon arising from their cell bodies ; most neurons with cell bodies in CNS (interneurons and motor neurons) are multipolar
Bipolar neurons have 2 processes extending from the cell body, a dendrite and an axon; found in some of the special senses, such as the eye, nose, and ears.
Unipolar neurons have only 1 process extending from the cell body; outside the cell body, it soon splits into 2 parts that funtion as 1 axon; the peripheral process has dendrites near a peripheral body part, and the central process runs into the CNS; the cell bodies are found in ganglia outside the CNS; there are sensory neuron
Sensory (afferent) neurons : conduct impulses from peripheral receptors to the CNS; usually unipolar, although some are bipolar
Interneurons (association or internuncial neurons) : multipolar neurons lying within the CNS that form links between other neurons ; the cell bodies of some interneurons aggregate in specialized masses called nuclei.
Motor (afferent) neurons : multipolar neurons that conduct impulses from the CNS to peripheral effectors (muscles or glands)
Connective tissue coverings
Epineurium : outer covering of a nerve
Perineurium : covering around fascicles (bundles) of nerve fibers
Endoneurium : covering around individual nerve fibers (axons)
Cerebrum : largest portion ; associated with higher mental functions, and sensory and motor functions
Diencephalon : processes sensory input and controls many homeostatic processes
Cerebellum : coordinates muscular activity
Brainstem : coordinates and regulates visceral activities, and connects different parts of the nervous system
Major parts of the brain
The four major parts of the spinal cord are the spinal cord, cervical enlargement, Lumbar enlargement, and Cauda equina (horses tail)
Major functions : transmit impulses to and from the brain, and to house spinal reflexes
Ascending tracts carry sensory information to the brain; descending tracts carry motor information from brain to muscles or glands
Spinal reflexes: controlled by reflex arcs that pass through the spinal cord.
Major parts and functions of the spinal cord
cranial nerves and spinal nerves
Twelve pairs of cranial nerves arise from the underside of the brain
Most are mixed nerves, containing sensory and motor nerve fibers, but some are only sensory, and others are primarily motor.
31 pair of spinal nerves arise from spinal cord and all except the first pair are mixed nerves
Numbered in sequence : 8 pairs of cervical nerves, 12 pairs of thoracic nerves, 5 pairs of lumbar nerves, 5 pairs of sacral nerves, and 1 pair of coccygeal nerves.
Each arises from from two roots : a sensory dorsal root, and a motor ventral root
Each dorsal root contains a dorsal root ganglion, which houses the cell bodies of sensory neurons entering the spinal cord.
A ventral root and dorsal root unite to form a spinal nerve, which extends out of the vertebral canal through the intervertebral foramen
There are more than 100 neurotransmitters
Neurotransmitters include acetylcholine, amino acids, neuropeptides
Action of neurotransmitter depends on type of receptors in a specific synapse
Some neurons produce one type of neurotransmitter, while others produce two or three
neurotransmitters
Reflex arc
Components :
A sensory receptor that detects changes
A sensory neuron, that carries the information from a receptor towards the CNS
An interneuron in the CNS (reflex center)
A motor neuron, that carries a command to effectors
An effector (muscle or gland that carries out the reflex) that responds to the initial change.
Diseases/ disorders
Cerebrovascular Accident (stroke) : Occurs when blood flow to a portion of the brain is halted
Autism : Brain disorder that makes it difficult to communicate
Alzheimer's Disease : A form of dimentia associated with age
Spinal cord Injury : Damage to the spinal cord
Meningitis : Infection in the meninges surrounding the sun
Multiple Scierosis : Autoimmune disease that damages the myelin sheath
Action potential and nerve impulse
An action potential is a rapid sequence of changes in the voltage across a membrane
Nerve Impulse ; A signal transmitted along a nerve fiber